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Telegram @neetquestionpaper, , Arihant Prakashan (Series), Meerut, All Rights Reserved, , © Publisher, No part of this publication may be re-produced, stored in a retrieval system or distributed, in any form or by any means, electronic, mechanical, photocopying, recording, scanning,, web or otherwise without the written permission of the publisher. Arihant has obtained, all the information in this book from the sources believed to be reliable and true. However,, Arihant or its editors or authors or illustrators don’t take any responsibility for the absolute, accuracy of any information published and the damages or loss suffered there upon., All disputes subject to Meerut (UP) jurisdiction only., , Administrative & Production Offices, Regd. Office, ‘Ramchhaya’ 4577/15, Agarwal Road, Darya Ganj, New Delhi -110002, Tele: 011- 47630600, 43518550; Fax: 011- 23280316, , Head Office, Kalindi, TP Nagar, Meerut (UP) - 250002, Tele: 0121-2401479, 2512970, 4004199; Fax: 0121-2401648, , Sales & Support Offices, Agra, Ahmedabad, Bengaluru, Bareilly, Chennai, Delhi, Guwahati,, Hyderabad, Jaipur, Jhansi, Kolkata, Lucknow, Meerut, Nagpur & Pune, ISBN : 978-93-13196-51-8, , Published by Arihant Publications (India) Ltd., For further information about the books published by Arihant, log on to www.arihantbooks.com or email to info@arihantbooks.com, , /arihantpub, , /@arihantpub, , Arihant Publications, , /arihantpub, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , PREFACE, Handbook means reference book listing brief facts on a subject., So, to facilitate the students in this we have released this, Handbook of Biology. This book has been prepared to serve, the special purpose of the students, to rectify any query or any, concern point of a particular subject., This book will be of highly use whether students are looking, for a quick revision before the board exams or just before other, Medical Entrances., This handbook can even be used for revision of a subject in the, time between two shift of the exams, even this handbook can, be used while travelling to Examination Centre or whenever, you have time, less sufficient or more., The format of this handbook has been developed particularly so, that it can be carried around by the students conveniently., The objectives of publishing this handbook are :, — To support students in their revision of a subject just before, , an examination., — To provide a focus to students to clear up their doubts about, , particular concepts which were not clear to them earlier., — To give confidence to the students just before they attempt, , important examinations., , However, we have put our best efforts in preparing this book,, but if any error or what so ever has been skipped out, we will, by heart welcome your suggestions. Apart from all those who, helped in the compilation of this book, a special note of thanks, goes to Miss Akansha Tomar of Arihant Publications., , Authors, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , CONTENTS, 1. The Living World, , 1-6, , — Characteristics of Living Beings, , — Taxonomy, , — Biodiversity, , — Taxonomical Aids, , — Systematics, , 2. Biological Classification, , 7-23, , — Biology : Nature and Scope, , — Kingdom–Fungi, , — Classification of Living Organisms, , — Kingdom–Plantae, , — Kingdom–Monera, , — Kingdom–Animalia, , — Kingdom–Protista, , — Viruses and Viroids, , 3. Plant Kingdom, — Plants : Producers of Ecosystem, , 24-42, — Gymnospermae, , — Algae, , — Angiospermae, , — Bryophyta, , — Alternation of generations, , — Pteridophyta, , 4. Animal Kingdom, , 43-73, , — Basis of Classification, , — Phylum–Arthropoda, , — Phylum–Porifera, , — Phylum–Mollusca, , — Phylum–Coelenterata (Cnidaria), , — Phylum–Echinodermata, , — Phylum–Platyhelminthes, , — Phylum–Hemichordata, , — Phylum–Aschelminthes, , — Phylum–Chordata, , — Phylum–Annelida, , 5. Morphology of Flowering Plants, , 74-103, , — Plant Morphology : An Overview, , — Flower, , — Stem, , — Fruit, , — Leaf, , — Seed, , — Inflorescence, , 6. Anatomy of Flowering Plants, — The tissues, — Plant Tissue System, , 104-121, — Anatomy of Dicot and Monocot, , Plants, — Secondary Growth in Plants, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 122-151, , 7. Structural Organisation in Animals, — Tissue, , — Neural Tissue, , — Epithelial Tissue(By Ruysch), , — Earthworm, , — Connective Tissue, , — Cockroach, , — Muscular Tissue, , — Frog, , 8. Cell : The Unit of Life, — Cell, , 152-166, — Structure and Components of, , Eukaryotic Cell, , — Cell Theory, , — Components of a Cell, , 9. Biomolecules, — How to Analyse Chemical, —, —, —, —, , Composition?, Biomolecules, Carbohydrates(Saccharides), Proteins, Lipids, , 167-188, — Nucleic Acids, — DNA, — RNA, — Enzymes, — Metabolites, , 10. Cell Cycle and Cell Division, , 189-194, , — Cell Cycle, , — Amitosis, , — Dividing or M-phase, , — Significance of Cell Cycle, , 11. Transport in Plants, — Process Involved in Passive, , 195-206, — Upward Water Movement in a, , Transport, — Plant-Water Relation, , Plant, — Uptake and Transport of Mineral, , Nutrients, , — Long Distance Transport of Water, — Absorption of Water by Plants, , — Translocation and Storage of Food, , in Plants (Phloem Transport), , 12. Mineral Nutrition in Plants, , 207-214, , — Classification of Mineral Nutrients, , — Hydroponics, , — Deficiency Symptoms of Essential, , — Metabolism of Nitrogen, , Mineral Nutrients, , 13. Photosynthesis in Higher Plants, , 215-227, , — Chemistry and Thermodynamics, , — Photorespiration, , of Photosynthesis, — Chloroplast : Photosynthetic, Organ of Cell, , — Factors Affecting Photosynthesis, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 14. Respiration in Plants, , 228-238, , — Cellular Respiration, , — Anaerobic Cellular Respiration, , — Aerobic Respiration, , — Factors Affecting Respiration, , — Pentose Phosphate Pathway (PPP), , 15. Plant Growth and Development, — Growth, , 239-248, , — Seed Dormancy, , — Development, , — Photoperiodism, , — Plant Hormones/Phytohormones/, , — Abscission of Plant Parts, , Plant Growth Regulators (PGRs), , 16. Digestion and Absorption, , 249-264, , — Human Digestive System, , — Digestive Enzymes, , — Alimentary Canal, , — Digestive Hormones, , — Digestive Glands, , — Disorder of Digestive System, , — Physiology of Digestion, , 17. Breathing and Exchange of Gases, — Respiration, , 265-275, , — Transport of Gases, , — Human Respiratory System, , — Regulation of Respiration, , — Lungs, , — Disorders of Respiratory System, , — Exchange of Gases, , 18. Body Fluids and Circulation, — Body Fluids, , 276-296, — Human Circulatory System, , — Blood, , — Blood Vascular System, , — Lymph, , — Portal System, , — Circulatory System, , 19. Excretory Products and Their Elimination, — Excretion, , 297-306, , — Regulation of Kidney Function, , — Excretory Products, , — Micturition, , — Human Excretory System, , — Role of Other Organs in Excretion, , — Mechanism of Filtrate, , Concentration, , 20. Locomotion and Movement, , 307-329, , — Locomotion, , — Skeletal System, , — Movement, , — Joints, , — Muscle, , — Disorders of Muscular and, , — Specialised Muscle Phenomena, , Skeletal System, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 21. Neural Control and Coordination, , 330-359, , — Human Neural System, , — Nerve Impulse, , — Central Nervous System, , — Synapse, , — Brain, , — Sense Organs, , — Brain Ventricles, , — The Visual Sense-The Eye, , — Spinal Cord, , — Human Ear-Organ of Hearing and, , — Reflex Action, , Balance, , — Reflex Arc, , 22. Chemical Coordination and Integration, , 360-370, , — Glands, , — Regulation of Hormone Action, , — Hormones, , — Major Hormones of Human, , — Human Endocrine System, , Endocrine System, , — Mechanism of Hormone Action, , 23. Reproduction in Organisms, — Reproduction in Plants, — Reproduction in Animals, , 371-375, — Events in Sexual Reproduction of, , Both Plants and Animals, , 24. Sexual Reproduction in Flowering Plants, — Flowers, , 376-390, , — Fertilisation, , — Pre-fertilisation : Structures and, , — Post-fertilisation Events, , Events, — Pollination, , — Development of, , Embryo/Embryogenesis, , 25. Human Reproduction, , 391-414, , — Male Reproductive System, , — Fertilisation, , — Female Reproductive System, , — Implantation, , — Gametogenesis, , — Embryonic Development, , — Spermatogenesis, , — Foetal Development, , — Structure of Sperm, , — Placenta, , — The Menstrual Cycle, , — Lactation, , 26. Reproductive Health, — Problems Related to Reproductive, , Health, , 415-425, — Acquired Immuno Deficiency, , Syndrome, , — Population Explosion, , — Infertility, , — Strategies to Improve, , — Assisted Reproductive Technology, , Reproductive Health, — Medical Termination of Pregnancy, — Sexually Transmitted Diseases, , — Detection of Foetal Disorders, , during Early Pregnancy, , www.aiimsneetshortnotes.com
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Telegram, @neetquestionpaper, 27. Principles of Inheritance, and Variation, 426-449, — Heredity, , — Sex-Determination, , — Variations, , — Linkage, , — Gregor Johann Mendel, , — Mutation, , — Mendel's Laws of Inheritance, , — Pedigree Analysis, , — Chromosomal Theory of, , Inheritance, , 28. Molecular Basis of Inheritance, , 450-468, , — DNA as Genetic Material, , — Wobble Hypothesis, , — DNA, , — Regulation of Gene Expression, , — RNA, , — Human Genome Project, , — Gene Expression, , — DNA Fingerprinting, , — Genetic Code, , 29. Evolution, — Origin of Universe, , 469-499, — Mutation Theory, , — Origin of Life, , — Mechanism of Evolution, , — Evidences of Evolution, , — Evolution of Human, , — Theories of Evolution, , — Human and Other Primates, , — Darwinism, , 30. Human Health and Diseases, — Human Health, — Common Diseases in Humans, — Immunity and Immune System, , 500-521, — Acquired Immuno Deficiency, , Syndrome, — Cancer, , — Complement System, , — Drugs, , — Vaccination and Immunisation, , — Addiction, , — Allergies, , — De-addiction, , — Autoimmunity, , — Adolescence, , 31. Strategies for Enhancement in Food Production, , 522-537, , — Animal Husbandry, , — Apiculture/Bee-Farming, , — Improvement of Animals through, , — Sericulture, , Breeding, — Pisciculture/ Fish Farming/ Culture, , Fishery, , — Lac Culture, — Plant Breeding, — Single Cell Protein, , 32. Microbes in Human Welfare, , 538-547, , — Microbes in Household Products, , — Bioherbicides, , — Microbes in Industrial Products, , — Bioinsecticides, , — Biopesticides, , — Microbes in Sewage Treatment, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 548-561, , 33. Biotechnology : Principles and Processes, — Principle of Biotechnology, , — Gel Electrophoresis, , — Genetic Engineering/Recombinant, , — Bioreactors, , DNA Technology, — Tools of rDNA Technology, , — Downstream Processing, , 34. Biotechnology and Its Applications, — Types of Biotechnology, — Applications of Biotechnology in, , 562-574, , — Applications of Biotechnology in, , Industry and Environment, , Plant Tissue Culture, — Applications of Biotechnology in, Medicine, , 35. Organisms and Population, , 575-585, , — Organism and its Environment, , — Population and Community, , — Responses to Abiotic Factors, , — Characteristics of Population, , — Adaptations, , 36. Ecosystem, , 586-603, , — Ecosystem, , — Features of Ecosystem, , — Components of Ecosystem, , — Food Chain, , — Ecosystem: Structure and, , Characteristics, , — Food Web, — Ecosystem Services, , 37. Biodiversity and Conservation, — Levels of Biodiversity, , 604-617, — Loss of Biodiversity, , — Patterns of Biodiversity, , — IUCN and Red List Categories, , — Importance of Biodiversity, , — Biodiversity Conservation, , 38. Environmental Issues, , 618-639, , — Pollution, , — Ozone Layer Depletion, , — Greenhouse Effect, , — Degradation by Improper, , — Global Warming, — Acid Rain, , Resource Utilisation and, Maintenance, , Appendix, , www.aiimsneetshortnotes.com, , 640-644
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Telegram @neetquestionpaper, , 1, The Living World, Life is a characteristic quality that differentiates inanimate (non-living), objects from the animate (living) forms., , Characteristics of Living Beings, Catabolism, Process of breakdown, of complex substances, into simpler ones,, e.g., respiration., , Anabolism, , Short-term Adaptations, , Process of formation, of complex substances, from simpler ones,, e.g., photosynthesis., , Temporary changes to, respond to changing, environment,, e.g., hibernation and, aestivation., , Long-term Adaptations, Permanent changes in, response to changing, environment,, e.g., humming birds., , Growth, Living organisms, grow with increase, in mass and number, of individuals/cells., , Heat Stroke, Increase in body, temperature above the, normal level., , A series of chemical, processes catalysed, by enzymes, occurring, within the body, of living beings., , Metabolism, , Adaptation, Genetic mechanism of, an organism to survive,, thrive and reproduce by, constantly enhancing, itself., , Characteristics, of, Living Beings, , Conciousness, , Reproduction, , Ability of an, organism to, sense its, environment., , Process of producing, young ones by, living things., , Hypothermia, Decrease in body, temperature below the, normal level., , Thermoregulation, Process that allows, your body to maintains, its core internal, temperature, , Cellular Organisation, Composition and, arrangement of, ·cells in body., , Asexual Reproduction, Irritability, Ability of an organism to, react against external stimuli,, e.g., movement of an, organism towards the light, source., , Does not involve the, fusion of gametes or, sex cells, e.g., Amoeba., , Sexual Reproduction, Involves the fusion of, gametes, e.g., humans., , Multicellular Organisms, Organisms with multiple, cells of various type,, e.g., Hydra., , Unicellular Organisms, Organisms having a, single cell,, e.g., Amoeba., , www.aiimsneetshortnotes.com
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2, , Telegram @neetquestionpaper, , Handbook of Biology, , Biodiversity, It is the degree of variability among living organisms. It includes all, the varieties of plants and animals. It encompasses all the ecological, complexes (in which the diversity occurs), ecosystem, community, diversity, species diversity and genetic diversity. It comprises all the, millions of species and the genetic differences between them., , Systematics, It is the study of the biodiversity. It attempts to classify the diversity of, organisms on the basis of following four fields viz, identification,, classification, nomenclature., , 1. Identification, It aims to identify the correct name and position of an organism in the, already established classification system. It is done with the help of, keys. Key is a list of alternate characters found in organisms. An, organism can be identified easily by selecting and eliminating the, characters present in the key., , 2. Classification, It involves the scientific grouping of identified organisms into, convenient categories or taxa based on some easily observable, and fundamental characters. The various categories which show, hierarchical arrangement in decreasing order are, Kingdom → Phylum → Class → Order → Family → Genus → Species, , 3. Nomenclature, After classification, organisms are subjected to a format of two-word, naming system called binomial nomenclature. It consists of two, components, i.e., generic name and specific epithet. For example, in, Mangifera indica, ‘Mangifera’ is the generic name and ‘indica’ is the, specific name of mango. This system was proposed by C Linnaeus, (a Swedish Botanist) in (1753) in his book Species Plantarum., Polynomial system of nomenclature is a type of naming system, containing more than two words. Trinomial system is a component of, polynomial system and contains three words. Third word represents, the sub-species and first two-words remain the same as in binomial, system., , Codes of Biological Nomenclature, There are five codes of nomenclature which help to avoid errors,, duplication and ambiguity in scientific names., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The Living World, 3, These codes, ICBN, ICZN, ICVN, ICNB, ICNCP, , are as follows, International Code of Botanical Nomenclature, International Code of Zoological Nomenclature, International Code of Viral Nomenclature, International Code for Nomenclature of Bacteria, International Code for Nomenclature for Cultivated Plants, , Types of Specification in Nomenclature, The ICBN recognises following several types are given below, Syntype, , Holotype, Prototype specimen from, which description of a new, species is established., , Any of the two or more, specimens cited by an, author when there is, no holotype., , Specification, in, Nomenclature, , Isotype, It is the same as, holotype., , Paratype, Specimens described, along with the holotype., , Neotype, , Lectotype, , New nomenclature type, when the holotype is, not available., , Specimen selected from, original material when, there is no holotype., , Taxonomy, It deals with the principles and procedures of identification,, nomenclature and classification of organisms. It reflects the natural, and phylogenetic relationships among organisms. It also provides the, details of external and internal structures, cellular structure and, ecological information of organisms. The term taxonomy was coined by, AP de Candolle, 1813., Various Branches of Taxonomy, Taxonomic Field, , Basis, , Alpha (α) Taxonomy, , Morphological traits, , Artificial Taxonomy, , Habit and habitat of organisms, , Natural Taxonomy, , Natural similarities among organisms, , Chemotaxonomy, , Presence or absence of chemicals in cells or tissues, , Cytotaxonomy, , Cytological studies, , Numerical or Phenetic Taxonomy, , Number of shared characters of various organisms, , Phylogenetic or Omega (ω) Taxonomy Based on phylogenetic relationships, , www.aiimsneetshortnotes.com
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4, , Telegram @neetquestionpaper, , Handbook of Biology, , Classical Taxonomy, It is also known as old taxonomy. In classical taxonomy, species is the, basic unit and it can be described on the basis of one or few preserved, specimens. Organisms are classified on the basis of some limited features., , Modern Taxonomy/New Systematics, The concept of modern taxonomy was given by Julian Huxley (1940)., According to it, species are dynamic and ever-changing entity. Studies, of organisms are done on a huge number of variations. It includes, cytotaxonomy, numerical taxonomy, chemotaxonomy, etc., , Taxonomic Categories, Classification is not a single step process. It involves hierarchy of steps, in which each step represents a rank or category. Since, the category is, a part of overall taxonomic arrangement, it is called the taxonomic, category., The taxonomic categories, which are always used in hierarchical, classification of organisms are called obligate categories., The sub-categories like sub-species, sub-class, sub-family, etc., which, facilitate more sound and scientific placement of various taxa are, called intermediate categories., Arrangement of taxonomic categories in a descending order during the, classification of an organism is called taxonomic hierarchy. It was, first introduced by Linnaeus (1751) and hence, it is also known as, Linnaean Hierarchy., Taxonomic Categories, , For Plants, Kingdom, , For Animals, Kingdom, , Division, , Phylum, , Class, , Class, , Order, , Order, , Family, , Family, , Genus, , Genus, , Species, , Species, , Taxonomic categories showing hierarchical, arrangement in ascending order, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The Living World, 5, Taxon represents the rank of each category and referred to as a unit, of classification. The term ‘Taxon’ was first introduced by ICBN during, 1956. According to Mayr (1964), taxon is a group of any rank that is, sufficiently distinct to be worthy of being assigned a definite category., In simple words, taxon refers to a group of similar, genetically related, individuals having certain characters distinct from those of other, groups., (i) Kingdom It is the highest category in taxonomy. A kingdom, includes all the organisms which share a set of distinguished, characters., (ii) Phylum or Division (Cuvier, Eichler) It is a taxonomic, category higher than class and lower in rank to kingdom. The, term ‘Phylum’ is used for animals, while ‘Division’ is commonly, employed for plants. It consists of more than one classes having, some similar correlated characters., (iii) Class (Linnaeus) It is a major category, which includes related, orders., (iv) Order (Linnaeus) It is a group of one or more related families, that possess some similar correlated characters, which are, lesser in number as compared to a family or genera., (v) Family (John Ray) It is a group of related genera with less, number of similarities as compared to genus and species. All the, genera of a family have some common or correlated features., They are separable from genera of a related family by, important differences in both vegetative and reproductive, features., (vi) Genus (Term given by John Ray) It comprises a group of related, species, which has more characters common in comparison to, species of other genera. In other words, genera are the, aggregates of closely related species., (vii) Species Taxonomic studies consider a group of individual, organisms with fundamental similarities as a species, (John Ray). It is the lowest or basic taxonomic category, which, consists of one or more individuals of a population., , www.aiimsneetshortnotes.com
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6, , Telegram @neetquestionpaper, , Handbook of Biology, , Taxonomical Aids, They include techniques, procedures and stored information that are, useful in identification and classification of organisms., Some of the taxonomical aids are as follows, Herbarium, Storehouse of collected, plant specimens that are, dried, pressed and, preserved on sheets., , Museums, Place for the collection, of preserved plants and, animal specimens., , Manuals and Catalogues, Provide information for, identification of names, of species found in an area., , Taxonomical Aids, , Keys, Used for identification of, plants and animals based, on their similarities and, dissimilarities., , Monographs, Contain information, on any one taxon., , Botanical and Zoological Parks, Contain the living collection of, plants and animals in the, conditions similar to their, natural habitat., , Importance of Taxonomical Aids, l, , l, , These aids help to store and preserve the information as well as, the specimens. The collection of actual specimens of plant and, animal species is essential and is the prime source of taxonomic, studies., These are also essential for training in systematics which is used for, the classification of an organism. Hence, taxonomic aids facilitate, identification, naming and classification of organisms using actual, specimens collected from the fields and preserved as referrals in the, form of herbaria, museums, etc., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 2, Biological, Classification, Biology : Nature and Scope, Biology (L. bios – life; logos – knowledge) is the branch of science,, which deals with the study of living organisms and their life processes., Aristotle is called the Father of Biology, but the term ‘Biology’ was, first coined by Lamarck and Treviranus in 1802. It has two main, branches, i.e., Botany (study of plants) and Zoology (study of animals)., Father of Botany Theophrastus, Father of Zoology Aristotle, l, , l, , Classification of Living Organisms, Classification is an arrangement of living organisms according to their, common characteristics and placing the group within taxonomic, hierarchy., The branch of science which deals with description, nomenclature,, identification and classification of organisms is called taxonomy., Some major branches of taxonomy are, (i) Numerical taxonomy It is based on all observable, characteristics. Number and codes are assigned to characters, and data is processed through computers., (ii) Cytotaxonomy In this taxonomy, the detailed cytological, information is used to categorise organisms., (iii) Chemotaxonomy The chemical constituents are taken as, the basis for classification of organisms., , www.aiimsneetshortnotes.com
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8, , Telegram @neetquestionpaper, , Handbook of Biology, , On the basis of reference criteria, the classification of living organisms can be, of three types, Classification of Living Organisms, Artificial, or, Prior Classification, , Natural, or, Phenetic Classification, , Phylogenetic, or, Cladistic Classification, , 1. Artificial or Prior Classification, In this system of classification one or very few characters are, considered as the key feature of classification. This classification, system never throws light on affinities or relationships between the, organisms., , 2. Natural or Phenetic Classification, The classification system in which organisms are classified on the basis, of their permanent vegetative characters. In this classification system,, the grouping of heterogenous groups (unrelated) of organisms is, avoided., , 3. Cladistic or Phylogenetic Classification, This classification may be monophyletic (i. e. , one ancestry),, polyphyletic (i. e. the organism derived from two ancestors) and, paraphyletic (i. e. , the organism does not include all the descendents of, common ancestor)., Cladistics is a method of classification of organisms based upon their, genetic and ancestral relationships, which are more scientific and, natural., The most accepted, five kingdom system of classification of living, organisms was proposed by RH Whittaker. These five kingdoms are, Monera, Protista, Fungi, Animalia and Plantae., , Other Classification Systems, l, , l, , Two kingdom system–Carolus Linnaeus (Animalia and Plantae)., Merits Photosynthetic organisms were included into plant kingdom, and non-photosynthetic organisms were included into animal, kingdom., Demerits Some organisms do not fall naturally either into plant or, animal kingdom or share characteristics of both., Three kingdom system–Ernst Haeckel (Protista, Animalia and, Plantae)., Merits Created a third kingdom which includes unicellular, eukaryotic microorganisms and some multicellular organisms., Demerits Monerans were not placed correctly., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biological Classification, 9, l, , l, , Four kingdom system–Copeland (Monera, Protista, Animalia and, Plantae)., Merits Monerans were placed separately along with other kingdoms., Demerits Monerans were not subdivided in Archaebacteria and, Eubacteria., Six kingdom system–Carl Woese (Archaebacteria, Eubacteria,, Protista, Fungi, Animalia and Plantae)., Merits Archaebacteria and Eubacteria were separately placed., , A. Kingdom–Monera (Prokaryotic, Unicellular Organisms), It includes all prokaryotes such as bacteria, archaebacteria,, mycoplasma, actinomycetes, cyanobacteria and rickettsia., , 1. Bacteria, These unicellular, prokaryotic organisms contain cell wall (feature of, plant cells only). These are approximately 4000 species of bacteria,, with cosmopolitan occurrence. Bacteria can be regarded both friends, and foes on the basis of interaction with human beings., An average weight human (~ 70 kg) has about 2.5 kg of bacteria in the, form of gut microflora to supplement the proper digestion and other, metabolic functions., Details to bacteria can be visualised in a nutshell as, Bacteria, Archaebacteria, (primitive bacteria), , Methanogens, (methane producing, bacteria), , On the basis, of structure, , Bacilli, (capsule), , Spirillum, (spiral), , On the basis, of nutrition, Autotrophic, • Photosynthetic, bacteria, , Gram-Negative, Bacteria, , Gram-Positive, Bacteria, , Non-motile, , Thermoacidophiles, (present in acidic, sulphur springs), , Halophiles, (salty/marine, bacteria), , On the basis, of staining behaviour, , Cocci, (rounded), , Eubacteria, (true bacteria), , Vibrio, (comma-like), , Motile, , www.aiimsneetshortnotes.com, , • Purple-sulphur, bacteria, Heterotrophic, • Saprophytic, • Symbiotic, • Parasitic
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10, , Telegram @neetquestionpaper, , Handbook of Biology, , (i) Archaebacteria, These are the group of most primitive prokaryotes. They have a cell, wall, made up of protein and non-cellulosic polysaccharides. The, presence of 16 srRNA, makes them unique and helps in placing in a, separate domain called archaea between bacteria and eukarya., Archaebacteria can live under extreme hostile conditions like salt, pans, salt marshes and hot sulphur springs. They are also known as, living fossils, because they represent the earliest form of life on earth., Archaebacteria can be used for, (a) Experimentation for absorption of solar radiation., (b) Production of gobar gas from dung and sewage., (c) Fermentation of cellulose in ruminants., , (ii) Eubacteria, Eubacteria are ‘true bacteria’ which lack nucleus and membrane bound, organalles like mitochondria, chloroplasts, etc. Eubacteria are usually, divided into five phylums– Spirochetes, Chlamydias, Gram- positive, bacteria, Cyanobacteria and Proteobacteria., The structural detail of a typical eubacterial cell is given as follows, Inclusions, These are reserve food, deposits found in prokaryotic, and eukaryotic cells. These, may be of glycogen, starch,, lipid and sulphur granules., , Plasma Membrane, Its structure and functions, are similar to eukaryotic, plasma membrane., It is also the site of some, respiratory enzymes., Mesosome, Complex localised infolding, of membrane which serves, as respiratory organ,, i.e., centre of respiration., , Fimbriae, These are short, filamentous structures, composed of protein, pilin. These are, evenly distributed and used for, attachment rather than motility., Flagellum, Long, filamentous appendage consisting of, filament, hook and basal body. It is rotatory, in function and contains flagellin protein., , Capsule, It is made up of gelatinous polysaccharide, and polypeptide. It protects the bacteria,, from pathogens and desiccation. It helps, in adherance to any surface., Cytoplasm, It contains 80% water, protein,, carbohydrate, lipid, organic ions, etc., Ribosomes, 70 S type of ribosomes, consists, of r RNA and proteins., Cell Wall, It is rigid due to the presence of, murein. Cell wall contains Mg2+, ions which bind to teichoic acid., This binding protects the bacteria, from thermal injuries., Nuclear Area (Nucleoid), It is amorphous lobular mass of, fibrillar chromatin type material, which occupies 10-20% area of, cell., Plasmid, Small, circular, self-replicating, extrachromosomal DNA, having, few genes., , Detailed structure of a bacterium, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biological Classification, 11, Nutrition in Bacteria, The process of acquiring energy and nutrients., is called nutrition., On the basis of mode of nutrition, bacteria are of two types–, autotrophic and heterotrophic. About 1% bacteria show autotrophic, mode of nutrition and the rest are of heterotrophic habit., Chemosynthetic bacteria oxidise various inorganic substances such as, nitrates, nitrites and ammonia and use the released energy for their, ATP production., Autotrophic (i.e., photosynthetic) bacteria and heterotrophic, bacteria with their related details are mentioned in following tables., Some Photosynthetic Bacteria, Group, , Main Habitats, , Cell Wall, , Representatives, , Prochlorobacteria, , Live in tissues of marine, invertebrates., , Gram-negative, , Prochloron, , Purple or green, bacteria, , Generally anaerobic and, reside on sediments of, lakes and ponds., , Gram-negative, , Rhodospirillum, and Chlorobium, , Some Heterotrophic Bacteria, Group, , Main Habitats, , Cell Wall, , Representatives, , Spirochetes, , Aquatic habitats,, parasites of animals, , Gram-negative, , Spirochaeta and, Treponema., , Aerobic rods and, cocci, , Soil, aquatic habitats,, parasites of animals, and plants, , Gram-negative, , Pseudomonas,, Neisseria,, Nitrobacter,, Azotobacter and, Agrobacterium, , Facultative, anaerobic rods, (enterobacteria), , Soil, plants, animal gut Gram-negative, , Salmonella,, Shigella, Proteus,, Escherichia and, Photobacterium, , Sulphur and, sulphate reducing, bacteria, , Anaerobic muds,, sediments, (as in bogs, marshes), , Gram-negative, , Desulfovibrio, , Myxobacteria, , Decaying plant and, animal matter, bark of, living trees, , Gram-negative, , Myxococcus and, Chondromyces, , www.aiimsneetshortnotes.com
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12, , Telegram @neetquestionpaper, , Handbook of Biology, Group, , Main Habitats, , Cell Wall, , Representatives, , Mycoplasmas, , Parasites of plants, and animals, , Cell wall absent, , Mycoplasma, , Gram-positive, cocci, , Soil, skin and mucous, membranes of animals, , Gram-positive, , Staphylococcus, and, Streptococcus, , Gram-positive, , Bacillus and, Clostridium, , Endospore-forming Soil; animal gut, rods and cocci, Non-sporulating, rods, , Fermenting plant and, Gram-positive, animal material,, human oral cavity, gut,, vaginal tract, , Chemoautotrophes Soil, aquatic habitat, , Gram-negative, , Lactobacillus and, Listeria, , Halothiobacillus, and, Acidothiobacillus, , Respiration in Bacteria, Respiration occurs in the plasma membrane of bacteria. Glucose is, broken down into carbon dioxide and water using oxygen in aerobic, cellular respiration and other molecules such as nitrate (NO3 ) in, anaerobic cellular respiration., , Reproduction in Bacteria, Bacteria reproduce asexually and sexually both., , Asexual Methods, Asexually, bacteria reproduce by following methods, Fission Bacteria divide both laterally and longitudinally., Budding Vegetative outgrowths result into new organisms after, maturity., Spore formation Non-motile spores like conidia, oidia and, endospores are formed., l, , l, , l, , Sexual Methods, Although sexes are not differentiated in bacteria, following methods of, genetic recombination are categorised under sexual reproduction in, bacteria., Transformation F Griffith (1928), Genetic material of one, bacteria is transferred to other through conjugation tube., l, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biological Classification, 13, l, , l, , Conjugation Lederberg and Tatum (1946), Transfer of genetic, material occurs through sex pili., Transduction Zinder and Lederberg (1952), Transfer of genetic, material occurs by bacteriophage., , Economic Importance of Bacteria, Economically, some bacteria are useful in producing various useful, substances like curd, cheese, antibiotics and vinegar, etc. While other, bacteria cause several chronic diseases in humans, plants and other, animals, etc., , Other Monerans, These are as follows, 1. Mycoplasma, It was discovered by Nocard and Roux in 1898. These are cell wall, less, aerobic and non-motile organisms. Due to the absence of cell wall, and pleomorphic nature, they are commonly called as jokers of living, world., The mycoplasmas are also known as Pleuro Pneumonia Like, Organisms (PPLO). These are the smallest living cells, yet, discovered, can survive without oxygen and are typically about, 0.1 µm in diameter., l, , l, , Lipoprotein membrane, (3 layers), Ribosomes, , DNA, , Soluble RNA, , Structure of Mycoplasma, , 2. Actinomycetes, The members of a heterogeneous group of Gram-positive, are, generally anaerobic bacteria noted for a filamentous and branching, growth pattern. It results in most forms in an extensive colony or, mycelium., l, , www.aiimsneetshortnotes.com
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14, l, , l, , l, , Telegram @neetquestionpaper, , Handbook of Biology, , Morphologically, they resemble fungi because of their elongated cells, that branch into filaments or hyphae. During the process of, composting, mainly thermophilic and thermotolerent Actinomyces, are responsible for the decomposition of the organic matter at, elevated temperature., Generally, Actinomycetes grow on fresh substrates more slowly than, other bacteria and fungi. During the composting process, the, Actinomycetes degrade natural substances such as chitin or, cellulose., Natural habitats of thermophilic Actinomycetes are silos, corn mills,, air conditioning systems and closed stables. Some Actinomycetes are, found responsible for allergic symptoms in the respiratory tract,, e.g., Extrinsic Allergic Alveolitis (EAA)., , 3. Cyanobacteria/Blue-Green Algae (BGA), They are Gram-negative photosynthetic prokaryotes which perform, oxygenic photosynthesis. These can live in both freshwater and, marine habitats and are responsible for ‘blooms’ in polluted water, (eutrophication)., They have photosynthetic pigments, chlorophyll-a, carotenoids, and phycobilins and food is stored in the form of cyanophycean, starch, lipid globule and protein granules., Cyanobacteria have cell wall formed of peptidoglycan, naked DNA,, 70S ribosomes and the absence of membrane bound organelles like, endoplasmic reticulum, mitochondria, Golgi bodies, etc., The red sea is named after the colouration provided by red coloured, cyanobacteria i.e., Trichodesmium erythraeum., Cyanobacteria can fix atmospheric nitrogen through a specific, structure called heterocyst. These are modified cells in which, photosystem-II is absent hence, non-cyclic photophosphorylation, does not take place. Nitrogen-fixation is performed through enzyme, nitrogenase, present in it., l, , l, , l, , l, , l, , 4. Rickettsia, These are small, aerobic and Gram-negative bacteria. They belong to, phylum–Proteobacteria, which are capable of growing in low level of, nutrients and have long generation time relative to other, Gram-negative bacteria., Rocky Mountain Spotted Fever (RMSF) is a tick borne human, disease caused by Rickettsia rickettsii, an obligate, intracellular, bacteria., l, , l, , www.aiimsneetshortnotes.com
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16, , Telegram @neetquestionpaper, , Handbook of Biology, , 2. Chrysophytes, These include diatoms and desmids. Diatoms are mostly aquatic, and sometimes present in moist terrestrial habitat. They are very, good pollution indicator., The diatoms do not decay easily as their body is covered by siliceous, shell. They pile up at the bottom of water body and form diatomite or, diatomaceous earth (can be used as fuel after mining)., , 3. Euglenoids, These are Euglena like unicellular flagellates found mostly in stagnant, freshwater. Instead of a cell wall, they have a protein rich layer called, pellicle, which makes their body flexible., They have two types of flagella, (i) Long Whiplash, (ii) Short Tinsel, The food is stored in proteinaceous granules called pyrenoids., Photosynthetic euglenoids, behave like heterotrophs in dark, this mode, of nutrition is called mixotrophic., The chief member of this group, i.e., Euglena is regarded as connecting, link between animals and plants., , Fungi-Like Protists (Slime Moulds), They possess the characters of both animals and fungi therefore,, combinedly called as fungus-animals. They show saprophytic food, habit and consume organic matter. Under suitable conditions, they, form Plasmodium. On the basis of occurrence of Plasmodium, these are, of two types, (i) Acellular/Plasmodial slime moulds, e.g., Physarum, Fuligo, septica, etc., (ii) Cellular slime moulds, e.g., Dictyostelium, Polysphondylium, etc., , Animal-Like Protists (Protozoans), The most primitive relatives of animals, protozoans are heterotrophic, (predator or parasitic) organisms, divided into four major groups, (i) Amoeboid protozoans They live in freshwater, moist soil, and salt water as parasite. They move with the help of, pseudopodia as in Amoeba., Other members of this group are, Entamoeba histolytica and E. gingivalis cause various digestive, and oral diseases when engulfed through polluted water., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biological Classification, 17, (ii) Flagellated protozoans They are either free-living or, parasitic in nature. Chief members are, (a) Trypanosoma sp.–carried by tse-tse fly and causes African, sleeping sickness., (b) Leishmania sp. carried by sand fly and causes kala-azar or, dum-dum fever., (c) Giardia sp. causes giardiasis., (d) Trichomonas vaginalis causes leucorrhoea., (iii) Ciliated protozoans They are aquatic and move actively due, to the presence of cilia. They show nuclear dimorphism (macro, and micronucleus), e.g., Paramecium, etc., (a) Macronucleus/Vegetative nucleus Controls metabolic, activities and growth., (b) Micronucleus/ReproductivenucleusControls reproduction., (iv) Sporozoans They have an infectious, spore-like stage in their, life cycle. All are endoparasites. Locomotory organs are cilia,, flagella and pseudopodia, e.g., Plasmodium, Monocystis, etc., , C. Kingdom–Fungi (Eukaryotic, Heterotrophic Organisms), Fungi are a group of eukaryotic, achlorophyllous, non-photosynthetic, and heterotrophic organisms., The basic features of fungi include, (i) Fungi lack chlorophyll, hence they are heterotrophic., (ii) They cannot ingest solid food, but absorb it after digestion., The digestive enzymes are secreted on food, then they (fungi), absorb it., (iii) On the basis of food sources, they may be saprophyte or, parasites. Cell wall in fungi is made up of nitrogen containing, polysaccharides, chitin. Reserved food material is glycogen or, oil. Along with certain bacteria, saprotrophic fungi function as, the main decomposers of organic remains., With the exception of yeasts (unicellular, fungi and filamentous), fungi, bodies consist of long, slender, thread-like structures called hyphae., Mycelium is the network of hyphae. Some are called coenocytic hyphae, (continuous tubes filled with multinucleated cytoplasm) and others, have cross walls (septae) in their hyphae. Cell walls of fungi are, composed of chitin and polysaccharides., , www.aiimsneetshortnotes.com
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20, , Telegram @neetquestionpaper, , Handbook of Biology, , (ii) Life Cycle of Yeast, The diagrammatic representation of sexual cycle of Saccharomyces, cerevisiae is as follows, Dwarf strain, yeast cells, , B, , Budding, , +, C, , A, , +, Gametangia, , –, , Germinate, –, Plasmogamy, Ascospore, , L, , D, , Ha, pl, op, h, Di, (, n) ase, pl, op, (2 has, n), e, , Karyogamy, , Ascospores, Mature, ascus, K, , Young, ascus, , Zygote, E, Germination, , Large strain, yeast cell, F, , Ascus mother, cell, , J, Meiosis, , Bud, , G, I, , Budding, , H, , Life cycle of Saccharomyces cerevisiae, , Heterothallism, The phenomenon of having two genetically different and compatible, sexual strains in two different thalli is called heterothallism. It was, discovered by Blakeslee in Mucor., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biological Classification, 21, Mushroom and Fairy Rings, Agaricus compestris is an edible mushroom. It is also called white, button mushroom. The fruiting body of Agaricus, arises in concentric, rings (called fairy rings or fungal flowers) from the mycelium present, in the soil., , Lichens, They have composite structure and consist of two dissimilar organisms, forming a symbiotic relationship between them., Lichens are formed by, Algal Part — Phycobiont — Provide food to fungi, Fungal part — Mycobiont — Provide shelter to algae, l, , l, , Lichens are of three types on the basis of their structure, (i) Crustose lichens These are point-like, flat lichens, e.g., Caloplaca., (ii) Foliose lichens These lichens have leafy structure,, e.g., Hypogymnia physodes., (iii) Fruticose lichens These are branched lichen, form filamentous, branching, e.g., Cladonia evansii, Usnea australis, etc., Various forms of lichens are given below, Fungal fructification, , Graphis, (crustose), , Cora, (foliose), Attaching disc, , Parmella, (foliose), , Pendent, branches, , Usnea, (fruticose), , Podetia, Early, foliose, part, Fungal, fructification, , Cladonia, (fruticose), , Forms of lichens, , Mycorrhiza, It is a symbiotic association between a fungus and a plant. Plants, prepare organic food and supply them to fungus and in return, fungus, supplies water and mineral nutrients to plants., , www.aiimsneetshortnotes.com
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22, , Telegram @neetquestionpaper, , Handbook of Biology, , D. Kingdom–Plantae (Eukaryotic, Chlorophyllous Organisms), These are chlorophyllous and embryo forming organisms. Mostly, non-motile and function as the producers in ecosystem as they can fix, solar energy into chemical energy through the process of, photosynthesis. The cell wall in plants is cellulosic and stored food, material is in the form of starch., A detailed account of plant kingdom is given in chapter 6., , E. Kingdom–Animalia (Multicellular, Eukaryotic Organisms), The heterotrophic, eukaryotic organisms which are multicellular and, lack cell wall, present in this kingdom. Animals have advanced level of, tissue organisation, in which the division of labour is highly specific., The two main groups among animals are Non-chordata and Chordata,, divided on the basis of the presence of notochord in them., A detailed account of animal kingdom is given in chapter 7., , Viruses and Viroids, 1. Viruses, The term ‘Virus’ means poisonous fluid. The word was coined by, Louis Pasteur. Viruses are very small (0.05-0.2 µm), infective,, nucleoprotein particles, which can be called as living because of the, presence of nucleic acid as genetic material and ability to produce their, own copy-viruses. They show only some properties of living beings,, otherwise they behave like non-livings. Hence, these are referred to as, the connecting link between living and non-living., On the basis of nature of genetic material, the viruses are of two types, (i) Adenovirus DNA containing, e.g., HIV, etc., (ii) Retrovirus RNA containing, e.g., Rous sarcoma virus, etc., On the basis of their host, the viruses can be categorised as, (i) Animal virus (Zoophagineae), e.g., HIV, sarcoma, etc., (ii) Plant virus (Phytophagineae), e.g., TMV, etc., (iii) Bacterial viruses (Phagineae), e.g., T4 phage, etc., , Characteristics of Viruses, Characteristics of viruses are as follows, , Living, l, , l, , l, , l, , They can replicate., In host body, they can synthesise protein., They cause diseases like other living organisms., Similar gene mutation as living organism., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biological Classification, 23, Non-living, l, , l, , l, , l, , Do not have protoplasm, and do not perform metabolism., These can be crystallised., They do not respire., In vitro culture is not possible., , Structure of Viruses, (i) Viruses are non-cellular and ultramicroscopic., (ii) Virus has two components, (a) A core of nucleic acid called nucleoid., (b) A protein coat called capsid., , Capsomeres, together form, capsid, a protein coat, usually highly symmetrical., , Envelope, only in, some larger viruses., Genetic material,, DNA or RNA, , Core region, inside capsid, , Structure of a virus (generalised), , 2. Viroids (RNA without a Capsid), TO Diener (1917) introduced the term as ‘Subviral pathogens’. Viroids, are 100 times smaller than smallest virus. They are known to be, infectious for plants only (no animal), e.g., potato spindle tuber caused, by viroids., , Virion, An intact, inert, complete virus particle capable of infecting the host, lying outside the host cell in cell free environment is called virion., , Virusoids, These are like viroids, but located inside the protein coat of a true, virus. Virusoid RNA can be circular or linear. These are non-infectious, as they are replicated only in their host., , Prions/Slow Virus, The prions are smallest, proteinaceous infectious particles, i.e., disease, causing agents that can be transmitted from one animal to another., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 3, Plant Kingdom, Plants : Producers of the Ecosystem, Plants are multicellular, photoautotrophic and embryo forming, (excluding algae) organisms placed in kingdom–Plantae. They have, cell wall, which is made up of cellulose and reserve food material in the, form of starch (sometimes fat as in seeds)., Plants are referred to as producers, because they have unique ability to, fix solar energy in the form of chemical energy, through the process of, photosynthesis. They supply the energy in ecosystem to other living, organisms, hence they are referred to as producers., The plant kingdom is classified as, Plant Kingdom, , Phanerogamae (flowering), , Cryptogamae (non-flowering), Thallophyta, (plant body is not divided, into root, stem and leaves), Algae, Bryophyta, (these are, (non-embryophytes,, embryophytes, lack seeds and, without vascular, vascular tissue.), tissues.), , Gymnosperms, (naked seeded plants), , Pteridophyta, (these are embryo, bearing plants which, form seed and contain, vascular tissue as well.), , Angiosperms, (covered seed), , Monocotyledons Dicotyledons, , Ferns, Liverworts Hornworts Mosses, , Algae (L. Alga–sea weeds), These are eukaryotic, autotrophic (holophytic), chlorophyll containing,, non-vascular thallophytes. These are characterised by the absence of, embryonic stage and presence of non-jacketed gametangia. Mostly,, they are of aquatic habitat (both freshwater and marine)., The branch of Botany which deals with the study of algae is termed as, ‘Algology or Phycology’. FE Fritsch is known as ‘Father of Algology’., (Prof. MOP Iyengar is regarded as Father of Indian Algology)., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Plant Kingdom, 27, Life Cycle of Algae, Various algae show different types of life cycles. Life cycles of, Spirogyra and Ulothrix are discussed here., Life cycle of Spirogyra It is a green alga of filamentous shape., The detailed life cycle is given below., Aplanospore, Azygospore, Akinete, Asexual reproduction, , Chloroplast, Cytoplasm, , s, id, Nucleus, no, e, r, Py all, 1, ll w, Ce, Vegetative cell, , 11, 10, , Vegetative, filament, Three degenerating nuclei, Functional, nucleus, , 9, , 2, , Sexual reproduction, Haploid phase (n), , Four haploid nuclei, 8, Diploid, phase (2n), , Male, gamete, (n ), , Conjugation, tube, Female, gamete, (n), , ), sis, ei, o, (M, , 3, , S, co cala, nj rif, ug o r, at m, io, n, , 7, , Zygote (2n), 6, 5, Zygospore (2n), , 4, , Life cycle of Spirogyra, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Plant Kingdom, 29, Economic Importance, Algae can be both useful and harmful. Several useful algal species with, their uses are mentioned here, As Food, , As Medicine, , Ulva, Sargassum, Laminaria,, Porphyra, Nostoc and Laurencia., , In Industries, , Chlorella gives chlorellin, (antibiotic), Nitella is used, as mosquito repellent., , Algae, , Diatoms, Chondrus,, Polysiphonia, Gracilaria, are used in paints, cosmetics, etc., , In Agriculture, , Source of Minerals, Laminaria, Polysiphonia and, Ascophyllum are used in, extraction of minerals., , In Biological Research, , Nostoc, Anabaena, help in, nitrogen-fixation, hence, used as biofertilisers., , Chlorella,Scenedesmus and, Acetabularia are used as tools, for biological research., , Ecological Significance, Algae like planktons are used as, food by others and stabilise, the ecosystem., , Useful applications of algae, , Algin, Carrageenan and Agar, l, , l, , l, , Algin, used as artificial fibre to control blood flow in surgery and, in production of non-inflammable films, is extracted from marine, brown algae., Carrageenan, extracted from seaweeds is used in cosmetics, boot, polish, ice cream, paints, etc., Agar, extracted from Gelidium and Gracilaria is used in culture, medium, biscuits for diabetic patients, etc., – Sargassum is used as food and fodder., – Laminaria, Fucus are used in extraction of iodine, bromine and, potash., , Harmful Algae, Group of algae like Microcystis, Oscillatoria and Anabaena cause water, blooms (eutrophication) and death and reduction of aquatic organisms., , Bryophyta (L. Bryon–leaf-like; phyton–plant body), It is the simplest and primitive group of land plants. They are also, known as amphibians of plant kingdom because of their habitat, adaptability in both aquatic and terrestrial environment. They are the, connecting link between algae and pteridophytes. Bryophytes, , www.aiimsneetshortnotes.com
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32, , Telegram @neetquestionpaper, , Handbook of Biology, , Economic Importance, Bryophytes have limited economic importance, they can be used in, following ways, (i) They help in soil formation (pedogenesis) and act as agent, for biological succession., (ii) Peat from Sphagnum can be used as fuel and in preparation of, ethyl alcohol., (iii) They help in protecting soil from erosion., (iv) Some bryophytes are used as fodder for cattle., (v) Due to high water retention capacity, Sphagnum can be, used in preserving living materials and used in grafting of, plants., , Pteridophyta ( L. pteron–feather; phyton–plant), Pteridophytes are seedless, vascular cryptogams. They reproduce by, means of spores and can reach to the tree-like heights (30-40 feets)., , General Characteristics, (i) The plant body is differentiated into root, stem and leaves., (ii) The stem may be aerial or underground and is generally, herbaceous, rarely solid and stout., (iii) Vascular tissues consist of xylem (without vessels) and phloem, (without companion cells)., (iv) Alternation of generations is found here, gametophyte is, autotrophic and independent., (v) Sporangia containing leaves are called sporophylls., (vi) Antherozoids (flagellated male gametes) are formed in, antheridia., (vii) Reproduction is of both vegetative and sexual types., (viii) On the basis of development of sporangia, they are of two, types, (a) Eusporangiate From a group of superficial initial cells., (b) Leptosporangiate From a single superficial initial cell., , www.aiimsneetshortnotes.com
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34, , Telegram @neetquestionpaper, , Handbook of Biology, , Reproduction, Pteridophytes reproduce by vegetative, asexual and sexual methods., , Vegetative Reproduction, It takes place by two methods, (i) Death and decay of older tissues lead to separation of new, branches, which can grow into new plants., (ii) Adventitious buds develop from petiole and later on rooting, takes place and get separated., , Asexual Reproduction, It occurs by meiospores, When pteridophytic plants get mature, the special spore bearing, structures develop under the surface of pinnules., These structures are, (i) Sporangium These are differentiated into capsule and the, stalk. Capsule has a single layer of thick wall, which consists of, specialised cell along with the normal wall cells., (ii) Spores These are minute, bilateral bodies of brown, colour. The spore coat is two layered, i.e., thick exine and thin, intine., , Sexual Reproduction, It is of advanced type, in which the multicellular sex organs, (i.e., antheridia and archegonia) are borne on the underside of, prothallus. The mucilaginous substance oozes out from archegonia,, which contains malic acid. After diffusing into water, it attracts, antherozoids through chemotaxis. The male nucleus fuses with the, egg nucleus and forms zygote., , www.aiimsneetshortnotes.com
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36, , Telegram @neetquestionpaper, , Handbook of Biology, , The differentiation between male and female gametophytes ensures, cross fertilisation. This set of conditions occurs in Marsiliaceae and, Salviniaceae., , Economic Importance, Pteridophytes are economically important group of plants., Some of them are, (i) Pteridophytes are used in horticulture, since they resist, wilting so can be used in cut flower arrangements., (ii) Some ferns are used in handicrafts and basketery., (iii) Pteridium leaves are used in making green dyes., (iv) Club mosses are used for making industrial lubricant since, their spores contain non-volatile oils. These spores are also used, as fingerprint powder in forensic investigation., (v) Some pteridophytes are used as biofertiliser (Azolla) due to, their nitrogen-fixing ability., (vi) Some pteridophytes are eaten as food., , Gymnospermae (L. gymnos – naked; sperma – seed), Gymnosperms are naked seeded plants, which evolved earlier than the, flowering plants. They have their seeds exposed on the, megasporophylls, i.e., carpels. Probably, they are the first surviving, seed plants (evolved during Jurassic period)., , General Characteristics, (i) Plants are sporophytic, differentiated into root, stem and leaves., (ii) Always heterosporous, i.e., contains two types of spores, (one spore (microspore) produces male gametophyte and other, (megaspore) produces female gametophyte after germination)., (iii) Root system is well-developed, i.e., tap root system, some have, coralloid roots (e.g., Cycas)., (iv) Form various structures through symbiotic relationships,, i.e., coralloid root (with algae) and mycorrhizae (with fungi)., (v) Leaves are dimorphic. They are of two types, (a) Foliage leaves Green, simple, needle-shaped and pinnately, compound., (b) Scaly leaves, , Minute and deciduous., , (vi) Flowers are unisexual, simple, reduced and naked, i.e., without, perianth (except Gnetum)., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Plant Kingdom, 37, Classification of Gymnospermae, Classification of gymnosperms was described by A Arnold (1948) and, modified by Pilger and Melchior (1954)., Division–Gymnospermae, , Cycadopsida, , Coniferopsida, , Gnetopsida, , [monoxylic wood,, large frond (a type of leaf), and bipinnately compound, leaves] e.g., Cycas and, Zamia., , (large tree of sporophytic, nature, produce cones in, reproductive phase), e.g., Pinus and Cordaites., , (include both extinct, and extant genera), e.g., Gnetum and Ephedra., , Reproduction, Gymnosperms reproduce by both vegetative and sexual methods., , Vegetative Reproduction, This is done by bulbils, which commonly arise on trunk. These bulbils, get separated from plants and germinate into new plants., , Sexual Reproduction, The life cycle of gymnosperms is also characterised by alternation of, generations. The green leafy part of the plant is the sporophyte while,, the cones contain the male and female gametophytes., Upon landing on the female cone, the tube cell of the pollen forms the, pollen tube, through which the generative cells migrate towards the, female gametophyte., The generative cells split into two sperm nuclei, one of which, fuses with the egg, while the other degenerates. After fertilisation of, the egg, the diploid zygote is formed, which divides by mitosis to form, embryo., The seed is covered by a seed coat, which is derived from the female, sporophyte. No fruit formation takes place as gymnosperms do not, have true seed covering., , Life Cycle of Gymnosperms, The gymnosperms are higher plants with advanced life cycle., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Plant Kingdom, 39, Economic Importance, Food, , Academic, , • Tuber and seeds of Cycas., • Seeds of Gnetum sp., • Chilgoza from Pinus sp., , Both extinct and extant species, of gymnosperms help in, studying the process of evolution., , Medicines, • Resin of C. rumphii is, used to treat ulcers., • Ephedrine from Ephedra, (treatment of asthma)., • Resin of Pinus is used in, stomach problem and, to treat gonorrhoea., , Industrial Products, • Paper from pulp of Pinus sp., • Methyl alcohol, terpentine and, resin from Pinus sp., • The fossilised resin of, Pinus excelsa is known as amber,, used in jewellery and X-ray sheets., , Gymnosperms, , Ornamentals, , Furniture, , Almost all gymnosperms, are grown for ornamentation, purpose., , • Wood of Pinus., • Wood of Ephedra and, Gnetum are also used., , Angiospermae, (Gk. Angion–vessel; sperma–seed), Angiosperms constitute a distinct group of flowering plants, which form, covered seeds. With about 2,50,000 species, it can be regarded as the, most successful group of plants. They arose in middle of Cretaceous, period., , General Characteristics, (i) Angiosperms range from microscopic Wolffia to the largest tree, such as Eucalyptus., (ii) The pollen grains and ovules develop in their flowers and the, seeds are formed within the fruits., (iii) Nutritionally, they may be autotrophic (wheat, corn, etc.),, parasitic (Cuscuta, Santalum, etc.), saprophytic (Monotrapa,, etc.) and insectivorous (Drosera, Utricularia, etc.)., (iv) They may be herb, shrub and trees., (v) Their lifetimes may be ephemeral, annual, biennial and, perennial., (vi) Angiosperms are adapted to various habitats, as they may be, hydrophytes, xerophytes and mesophytes., (vii) A flower is a modified shoot comprising of four whorls, i. e. ,, sepal, petal, androecium and gynoecium., , www.aiimsneetshortnotes.com
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40, , Telegram @neetquestionpaper, , Handbook of Biology, , Classification of Angiosperms, A natural system of classification was given by George Bentham and, JD Hooker in 1862-63 in his book Genera Plantarum (3 volumes) in, Latin., The outline of the above mentioned classification is as follows, Phanerogamia, (seed plants in which sex organs are evident), Classes, Dicotyledonae, Sub-classes, Polypetalae, , Gymnospermae, , Monocotyledonae, , Sub-classes, , Gamopetalae Monochlamydeae Cycadaceae Coniferae Gnetaceae, , Some important plant families with their representative genera are, as follows, Ranunculaceae, Brassicaceae (e.g., mustard), Malvaceae, (e. g. , gurhal), Asteraceae (e.g., sunflower), Lamiaceae (e.g., tulsi),, Solanaceae (e.g., potato), Leguminosae (e.g., pea), Cucurbitaceae,, Euphorbiaceae, Orchidaceae, Palmae (e.g., cashewnut), Poaceae, (e.g., paddy) and Liliaceae (e.g., onion), etc., , Reproduction in Angiosperms, Angiosperms are plants that bear fruits and flowers. These flowers are, plant’s reproductive structures. Reproduction in angiosperms (mostly, sexual type) occurs when the pollen from an anther is transferred to, stigma., When the ovules get fertilised, they will develop into seeds., Non-reproductive structures like petals, sepals etc. of the flowers fall, off leaving only the ovary behind, which will develop into a fruit., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 41, Plant Kingdom, Economic Importance, Aesthetic/Sacred, Several plants have, sacred importance,, e.g.,tulsi, peepal, etc., Furniture, Wood from, angiosperms., , Food, Grain, cereals and, fruits., , Ornamental, Angiosperms, • Flowering plant., • Decoration material., , Vegetables, • Important food component., • Protein source., , Industrial, • Paper industry., • Cosmetics., • Baking industries., , Environment, Medicines, • Antibiotics, • Alkaloids, , • Biodiversity, • Air purification., , Useful applications of angiosperms, , Alternation of Generations, It can also be termed as ‘Patterns of life cycle’. Plants divide mostly, through mitotic divisions and form different plant bodies (these may be, haploid or diploid)., The interconversion of the haploid and diploid plant body in alternate, manner is called alternation of generations. Generally, it is of three, types, , Plant Life Cycles, (i) Haplontic Sporophytic generation is not prominent,, e.g., algae, etc., Gametophytic, plant, Germination, , Meiospores, , Gametangia, Haploid phase, (n ), , Zygotic meiosis, , Gametes, , Syngamy, Diploid phase, (2n), Zygote, , Diagrammatic outline of a haplontic life cycle, , www.aiimsneetshortnotes.com
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44, , Telegram @neetquestionpaper, , Handbook of Biology, , Phylum–Chordata, (True coelomates with enterocoelic type of coelom), , Three sub-phyla, Cephalochordata, , Urochordata (Tunicates), , • Notochord is restricted, , Vertebrata (Craniata), , • Notochord is replaced, , • Notochord is extended, , in the posterior part, of the body (tail region)., • Notochord is present in, larval stage only., • Body is unsegmented,, e.g., Herdmania., , in the head region., , by vertebral column., , • Notochord is present, , • Notochord is present in, embryonic stage only., , throughout the life., , • Body is either, , • Body is segmented,, , segmented or, unsegmented., , e.g., Amphioxus., , Two divisions, , Agnatha (Jawless), , Gnathostomata (Bear jaws), , • Mouth does not possess jaws., • Notochord persists throughout life., • Paired appendages are absent., • Single nostril is present., • Internal ear has two or one, , • Mouth bears jaws., • Embryonic notochord is replaced in, , semicircular canals., • 8-10 pairs of cranial nerves,, are present., , • Nostrils are paired., • Internal ear has three semicircular canals., • There are 10-12 pairs of cranial nerves., , adults by a vertebral column., , • Paired appendages (fins or limbs), are present., , Two classes, Ostracodermi, , Cyclostomata, , • Extinct class,, , • Contains 1-16 pairs of gill slits., • Head and brain are poorly developed., • Endoskeleton is cartilaginous., • Two-chambered heart., • Fertilisation is external and, , e.g., Pteraspis,, , development is indirect,, e.g., Petromyzon (lamprey),, Myxine (hagfish)., , Two super-classes, Pisces, , Tetrapoda, , • Fins are present., • Respire by gills., • Do not have internal nares, (except lungfish)., , • Heart is two or three-chambered., • They have internal ears., , • Limbs are present., • Respire by lungs, gills and skin., • They have internal nares., • Heart is three or four-chambered., • They have internal, middle and, external ears (except snakes)., , Three classes, , Chondrichthyes, (Cartilaginous fishes), , Placodermi, (Extinct), , Four classes, , Osteichthyes, (Bony fishes), , Amphibia, , Reptilia, , Classification of Phylum Chordata, , www.aiimsneetshortnotes.com, , Aves Mammalia
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Telegram @neetquestionpaper, Animal Kingdom, 45, Basis of Classification, There are few fundamental common features to various animal groups,, which form the basis of classification. These features are as follows, , 1. Level of Organisation, Though, all the members of kingdom–Animalia are multicellular, yet, all of them do not exhibit the same pattern of cellular organisation., Different levels of organisation are discussed below, Levels of Organisation, , Acellular or, Protoplasmic Level, , Cellular Level, , Tissue Level, , Body consists of Group of similar, cells forms tissues, many cells, Body consists of, which either forms which serves, mass of protoplasm., specific functions,, All activities are performed an aggregate or, e.g., coelenterates., by different cell organelles a colony. It is of, two types, and confined within the, limit of plasma membrane, (i) Cellular aggregate, e.g., Protozoa., Porifera (sponges),, where cells are not, organised into tissue., , Organ Level, Some tissues, , Organ-System, Level, , join and function, as a unit of a, organ,, e.g., Stomach, (one of digestive, organs) contains, all tissues, e.g.,, Platyhelminthes., , Group of, organs working, together to forms, organ system,, e.g., Organs such, as stomach,, intestine, etc., aid, in digestion and, constitute digestive, system, e.g.,, Nemathelminthes, to chordates., , (ii) Cellular colony, Protists and some, algae., , 2. Symmetry, It refers to the correspondence of body parts in all major respect like, size, shape, position, etc., with the parts on opposite side when divided, from the central axis., Types of symmetry found in animals are, (i) Radial symmetry In radial symmetry, the animal gets, divided into two ‘identical halves’ when any plane passes, through the central axis, e.g., coelenterates, echinoderms., (ii) Bilateral symmetry In bilateral symmetry, body is divided, into two ‘identical halves’ only when a plane passes through, the median longitudinal axis, e.g., annelids, arthropods, etc., , 3. Germ Layers, These are the groups of cells behaving as a unit during early stages of, embryonic development. On the basis of number of germ layers,, animals are placed in two groups, i.e., diploblastic and triploblastic., These groups are divided at the gastrulation stage., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Animal Kingdom, 47, 5. Segmentation, It is the serial repetition of similar parts along the length of an animal., It is of two types, (i) Pseudosegmented (strobilisation) Body is divided into number of, pseudosegments (proglottids) which are independent of each other,, e.g., tapeworms., (ii) Metameric Linear repetition of body parts (somites), e.g.,, annelids, arthropods and chordates., , 6. Notochord, It is a rod-like structure present on the dorsal side of the animal body., It is derived from the embryonic mesoderm. Based on its presence, and absence, animals are non-chordates (phylum–Porifera to, Echinodermata) and chordates (phylum–Chordata)., Major differences between Chordata and Non-Chordata are as follows, Chordata, , Non-Chordata, , Bilaterally symmetrical., , Asymmetrical, radially symmetrical or, bilaterally symmetrical., , True metamerism., , Non-segmented, false segmented or true, metamerically segmented., , True coelomates., , Acoelomate, pseudocoelomate or true coelomates., , Post-anal tail usually present., , It is usually absent., , Triploblastic animals., , Cellular, diploblastic or triploblastic animals., , Alimentary canal is always ventrally, placed to nerve cord., Heart is ventrally placed., , It is always dorsally placed to the nerve, cord., Heart is dorsal or absent., , Central nervous system is hollow,, dorsal and single., , Central nervous system is ventral, solid, and double., , Pharynx is perforated by gill slits., , Gill slits are absent., , Phylum–Porifera, Poriferans bear numerous minute pores called ostia on the body wall,, which leads into a central cavity called spongocoel or paragastric, cavity. The spongocoel opens to outside by osculum., , www.aiimsneetshortnotes.com
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48, , Telegram @neetquestionpaper, , Handbook of Biology, , Majority of poriferans (sponges) are marine and sedantry. They are, diploblastic animals and contain an outer dermal layer of pinacocytes, and inner gastral layer of choanocytes., Flagellum, (create water current), Microvilli, Collar microvillus, (filter particles, from water), , Flagellum, , Collar, , Basal granule, , Contractile, vacuole, , Rhizoplast, , Food vacuole, , Blepharoplast, Nucleus, , Mitochondrion, Nucleus, , Cytoplasm, , Endoplasmic, reticulum, , Protoplasmic processes, , (a), , (b), , Choanocyte : (a) Light microscopic view, (b) Electron microscopic view, , Canal System (Aquiferous system), It is a system of interconnected canals through which water circulates, and helps in a number of metabolic activities of a sedentary sponge. In, sponges, canal system is of three types, i. e. , asconoid, syconoid and, leuconoid., Different Types of Canal System, Asconoid Canal, System, , Syconoid Canal, System, , Leuconoid Canal, System, , Simplest type with thin, walls., , Complex type with thick, walls., , Much complex type with, highly folded thick walls., , Spongocoel is large and, spacious., , Spongocoel is narrow., , Spongocoel is either reduced, or absent., , www.aiimsneetshortnotes.com
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50, , Telegram @neetquestionpaper, , Handbook of Biology, , Common and Scientific Names of Some Members of Porifera, Common Species of, Porifera, , Scientific, Name, , Common Species of, Porifera, , Scientific, Name, , Glass rope sponge, , Hyalonema, , Venus flower basket, , Euplectella, , Bath sponge, , Euspongia, , Bowl sponge, , Pheronema, , Freshwater sponge, , Spongilla, , Dead man’s finger sponge, , Chalina, , Boring sponge, , Cliona, , Urn sponge, , Scypha, , Economic Importance, l, , l, , They are used commercially for bathing/cleaning sponges., They help to clean-up the ocean floor by boring into dead shells and, corals releasing chemicals to break them down., , Phylum–Coelenterata (Cnidaria), Coelenterates are the animals bearing a special body cavity called, coelenteron (gastrovascular cavity). They exhibit dimorphism and, display two major forms namely polyp (sedentary) and medusa, (swimming). They also exhibit trimorphism (e.g., Siphonophora) and, polymorphism (e.g., Porpita)., , Body Wall, They are diploblastic animals and their body wall contains several, types of cells, e.g., stinging cells (cnidoblast/nematocyst), interstitial, cells (totipotent cells), sensory cells, nerve cells, etc., Everted, thread, Barbules, Shaft or butt, , Cnidocil, , Barb, Shaft or butt, , Cnidocil, Barbules, , Operculum, Operculum, , Nematocyst, Barb, Coiled thread, Muscular, fibrils, Nucleus, , Lasso, , Nematocyst, Muscular, fibrils, Nucleus, , Lasso, , Nematoblast, (a), , (b), , Cnidoblast Cells : (a) Undischarged (b) Discharged, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Animal Kingdom, 51, Skeleton, In coelenterates, skeleton may be endoskeleton, exoskeleton or absent., Endoskeleton e.g., Alcyonium (fleshy mesogloea), Pennatula (axial, rod of calcified horn)., Exoskeleton e.g., Millipore (coenosteum), Gorgonia (gorgorin),, Madrepora (corallum)., Absent e.g., sea anemones., l, , l, , l, , Metagenesis, It is like the alternation of generations between the sexual (medusa), and asexual (polyp) forms. In contrast to alternation of generation in, metagenesis, it is difficult to distinguish between asexual and sexual, forms as both individuals are diploid., , Reproduction, It occurs both by sexual and asexual means., (i) Asexual reproduction, , By external budding., , (ii) Sexual reproduction By sexual medusae. The development, is usually indirect which occurs through ephyra, planula and, hydrula larvae., , Classification of Coelenterata, Phylum–Coelenterata, Three classes, , Hydrozoa, , Scyphozoa, , • Both polyp and medusa, present. Polyp stage dominant,, medusa stage reduced, or absent., • Velum is present., • Gonads are epidermal in origin., • Larva hydrula, planula,, , • Medusa form is dominant., Polyp represented as, scyphistoma stage., • Pseudovelum is present., • Gonads are endodermal, in origin., • Larva ephyra., , Anthozoa (Actinozoa), • Medusa form is absent., • Velum is absent., • Gonads, if present are, endodermal in origin., • Corals and sea anemone., , Common and Scientific Names of Some Coelenterates, Common Names of, Coelenterates, Sail-by-wind, , Scientific, Name, Valella, , Common Names of, Coelenterates, Organ-pipe coral, , Scientific, Name, Tubipora, , Portuguese man of war, , Physalia, , Stag horn coral, , Madrepora, , Stinging coral, , Millipora, , Mushroom coral, , Fungia, , Sea anemone, , Metridium, , Star coral, , Astraea, , Dead’s man finger coral, , Alcyonium, , www.aiimsneetshortnotes.com
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52, , Telegram @neetquestionpaper, , Handbook of Biology, , Economic Importance, l, , l, , l, , They take part in the formation of coral reefs, e.g., Millipora, (stinging coral)., Their skeleton has medicinal value, e.g., Tubipora (organ-pipe coral)., They have ornamental value, e.g., Astraea (star coral)., , Phylum–Ctenophora, The members of this phylum are generally marine, solitary,, free-swimming or pelagic. They are diploblastic animals and acoelomates., , Peculiar Characteristics, A gelatinous mesoglea is present between epidermal and gastrodermal, tissue layers. They are also called comb plates. Colloblast cells are, the sensory and adhesive cells., , Reproduction, Sexes are not separate. All are hermaphrodites. Gonads develop from, endosperm. Fertilisation is internal. Development is indirect through, cydippid larva., , Classification of Ctenophora, Phylum–Ctenophora, Two classes, , Tentaculata, • Possesses tentacles, • Contains two long aboral tentacles, • e.g., Ctenoplana, Velamen, etc., , Nuda, • Does not possess tentacles., • Have a highly branched gastrovascular cavity., • e.g., Beroe, etc., , Common and Scientific Names of Some Ctenophores, Common Name of Ctenophores, , Scientific Name, , Venus Girdle, , Velamen, , Sea walnut, , Pleurobrachia, , Swimming eye of cat, , Beroe, , Economic Importance, l, , l, , They reproduce quickly and are good predators., They can bring down an ecosystem., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Animal Kingdom, 53, Phylum–Platyhelminthes, They are dorsoventrally flat animals having either unsegmented and, leaf-like (e.g., flukes) or segmented and ribbon-like (Taenia) body. They, are the first animals to have bilateral symmetry and to undergo, cephalisation., , Habitat, They are mostly found as free-living forms, but few of them are, parasitic in their habitat., Platyhelminthes, , Free-living forms, , Freshwater, , Marine, , Parasitic forms, , Terrestrial, , (e.g., Dugesia (e.g., Convoluta, and Planaria) and Thysanozoon), , (e.g., Bipalium, and Geoplana), , Ectoparasites, (e.g., Diplozoon and, Gyrodactylus), , Endoparasites, (e.g., Echinococcus, and Taenia), , Peculiar Features, These are the first animals with triploblastic layers in body wall and, organ system organisation. They are acoelomates due to the, presence of a mesodermal connective tissue, parenchyma, in between, the visceral organs. These animals have ladder-type nervous system, and peculiar cells called flame cells or protonephridia for, excretion. These cells are modified mesenchymal cells., Nucleus, Pseudopodia, Globules of, excretion, Basal granules, , Cell lumen, Ciliary flame, Termination of, capillary duct, , Flame cell (Solenocyte), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 54, , Handbook of Biology, , Reproduction, These animals are generally bisexual. Cross- fertilisation occurs in, trematodes, while self-fertilisation occurs in cestodes. Fertilisation is, always internal. Turbellarians reproduce by transverse fission., , Life Cycle of Taenia solium, Adult, tapeworm in, human gut, , Rostellar, hooks, Neck, showing, strobilation, , Each cysticercus develops, into young tapeworm in the, Sucker human gut., , Fertilised ova (zygotes) in the mature, proglottids capsules containing, zygotes in gravid proglottids., , Scolex, , Bladder, (Cysticercus), , Hooks, , Cysticercus, Hexacanth reaches heart via liver, and finally muscles tongue,, shoulder, neck, thigh and settles, to develop into next larval stage, called cysticercus or bladder, worm within 10 days of infection, of the secondary host., It is the infective stage of human, when they feed infected meat., , Onchosphere (larvae) in the, gravid proglottids. It contains, all embryonic membranes, along with a hexacanth, (structure with 6 hooks)., , Bladder, Germ layer, (Oncosphere), , Onchospheres in human, faeces (outside the body)., Faeces containing, onchospheres is eaten by, pig., Hexacanth, It is the six-hooked larval, stage containing a pair of, penetration glands., , The graphical representation of life cycle of Taenia solium depicting different, larval stages and adult form in the primary and secondary hosts, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Animal Kingdom, 55, Life Cycle of Fasciola hepatica, Adult Fasciola in the liver of sheep, , Large number of eggs in faecal matter, of sheep. Development of egg into, next larval stage miracidium., , Metacercaria This is the, encysted infective stage of, the Fasciola and now infects, vertebrate host (sheep)., , Miracidium First larval stage freely swim, in water with the help of cilia present all, over body. Penetrate secondary host, snail reaches to salivary gland and forms, second larval stage sporocysts., , Cercaria It escapes from the, secondary host through, pulmonary sac. Its tail help in, swimming of the larvae in water., After 2-3 days, it loses its tail, and becomes incepted on grass, or aquatic plant and is now, called letacercaria., , Sporocyst It is the second larvae of, Fasciola living in pulmonary tissues, of snail and obtaining nutrition from it, and develops into 5-8 rediae., , Rediae It is the most important larval stage and it, bears an anterior end with a ring of collar, a birth pore, and pair of projections (lappets or procruscula)., During Summer, It replicates giving, rise to the same form,, i.e., daughter rediae., , During Winter Every rediae, produces, 14-20 cercaria, (next larval stage)., , Graphical representation of life cycle of Fasciola hepatica, depicting polyembryony along with different larval stages, , Classification of Plathelminthes, Phylum–Platyhelminthes, Three classes, , Trematoda, , Turbellaria, , • Mostly non-parasitic and, • Ecto or endoparasites., free-living., • Unsegmented and flat, leaf-like., • Unsegmented and flat leaf-like., Body wall contains, • Body wall contains, cuticular spines,, • syncytial epidermis with, rod-shaped rhabditis, e.g., Planaria. e.g., Fasciola., , Cestoda, • Exclusively endoparasites, • Segmented and, ribbon-like., • Body wall is lined by microvilli., e.g., Taenia., , Common and Scientific Names of Some Platyhelminthes, Common Names of, Platyhelminthes, Liver fluke, Planarian, , Scientific, Name, Fasciola, hepatica, Dugesia, , Common Names of, Platyhelminthes, , Scientific, Name, , Pork tapeworm, , Taenia solium, , Hydatid worm or dog, tapeworm, , Echinococcus, granulosus, , www.aiimsneetshortnotes.com
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56, , Telegram @neetquestionpaper, , Handbook of Biology, , Economic Importance, l, , l, , Fasciola causes fascioliosis or liver rot which is characterised by hepatitis., , Echinococcus causes hydatid disease which is characterised by, enlargement of liver., , Phylum–Aschelminthes, They are long, cylindrical, unsegmented and thread-like animals with, no lateral appendages, so these are commonly called roundworms,, bagworms or threadworms., , Peculiar Features, Body wall of these pseudocoelomate animals is composed of complex, cuticle, syncytial epidermis and only longitudinal muscles. They have, tube-within-tube plan of digestive system., They have fixed number of cells in every organ of the body (eutylic condition)., Excretory system is H-shaped and contains rennete cells., , Reproduction, Sexual dimorphism is present and males are smaller than females., Fertilisation is internal and it may be direct or indirect., Adults, ↑, , Lungs, , (4th moult), Back to intestine, ↑, In stomach, ↑, In oesophagus, ↑, Swallowed into gullet, ↑, In pharynx, ↑, In trachea, ↑, In bronchi, ↑, In bronchioles, ↑, Fourth stage juvenile, (3rd moult), ↑, Third stage juvenile, (2nd moult), ↑, Bores into lung alveoli, (stays for 10 days), ↑, In lung capillaries, , Females → Ova →, Males → Sperms →, , Fertilised eggs, out with, host faeces, ↓, , Spiral, determinate cleavage, ↓, First stage juvenile or rhabditiform larva (first moult), ↓, Life cycle, Second stage juvenile, of Ascaris, ↓, Embryonated egg, (Primary, swallowed by, Migration), human host, ↓, Egg hatches out, in intestine, ↓, Bores through intestinal, wall into blood capillaries, ↓, In mesenteric vein, ↓, 3-4 days, In hepatic portal vein, ↓, In liver capillaries, Liver, ↓, 3-4 days, In hepatic vein, , (Secondary, Migration), , 5 days, , ↓, ↑, In pulmonary artery ← Right auricle ← In posterior vena cava, , Heart, , A graphical representation of life cycle of Ascaris, , www.aiimsneetshortnotes.com
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58, , Telegram @neetquestionpaper, , Handbook of Biology, , Peculiar Features, l, , l, , l, , l, , l, , These animals show metameric segmentation, i.e., the external, division of the body by annuli corresponds to internal division of, coelom by septa., These are the first animals to have circulatory system., Locomotory organs are minute rod-like chitinous setae or suckers, which are embedded over parapodia., A characteristic circumoesophageal ring is present in the anterior, part of CNS., Special structures called nephridia are present for excretion., , Reproduction, Asexual reproduction By fragmentation is seen in some polychaetes., Sexual reproduction Sexes are either united (e.g., oligochaetes) or, separate (e.g., polychaetes). Fertilisation is internal (e.g., Hirudinaria), or external (e.g., earthworm). Development is direct in monoecious, form and indirect in dioecious form involving a free-swimming, trochophore larva., , Classification of Annelida, Phylum–Annelida, Three classes, , Oligochaeta, , Polychaeta, • Marine, fossorial, or tubicolous., • Distinct head bearing, tentacles, palps and, eyes., • Bristle-like setae and, parapodia for locomotion, • Clitellum is absent., • Unisexual,, e.g., Aphrodite and, Chaetopterus., , • Terrestrial, freshwater, • Distinct head with eyes, (palps and tentacles are, absent)., • Locomotion by peristalsis,, parapodia is absent., • Permanent clitellum, is present., • Bisexual,, e.g., Pheretima and, Tubifex., , Hirudinea, • Mostly freshwater,, few marine., • No cephalisation, • Locomotion by anterior, and posterior suckers., • Clitellum appears during, breeding season., • Bisexual,, e.g., Hirudinaria and, Acanthobdella., , Common and Scientific Names of Some Annelids, Common Names, of Annelids, , Scientific, Names, , Common Names, of Annelids, , Scientific, Names, , Earthworm, , Pheretima posthuma Paddle worm, , Clam worm, , Nereis, , Blood worm, , Glycera, , Polalo worm, , Eunice, , Skate sucker, , Pontobdella, , Sea mouse, , Aphrodite, , Lung worm, , Arenicola, , Chaetopterus, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Animal Kingdom, 59, Economic Importance, l, , l, , l, , l, , Earthworms are used as fish-baits and for improving the soil fertility., Polynoe shows bioluminescence and this phenomenon is used in, self-defence., Tubifex has putrefaction ability and is grown in filtre beds of sewage, disposal plants., Pontobdella causes huge food loss to man when present in large number., , Phylum–Arthropoda, It is the largest phylum of Animalia which includes insects with, jointed legs and sclerotised exoskeleton. Their body is divided into, three parts or tegmata, i.e., head, thorax and abdomen. They are, haemocoelomates, i.e., true coelom is replaced by haemocoel, (pseudocoel with blood). The body appendages are variedly modified in, different arthropods to perform various functions., Running, e.g., cockroach, , Swimming, e.g., belostoma, , Body, Appendages, , Pollen Collection, e.g., in honeybee, , Grasping the Prey, e.g., raptorial, prolegs in, praying mantis, , Jumping, e.g., saltatory legs, in grasshopper, , Digging, e.g., Forficula, , Peculiar Features, l, , l, , l, , l, , They are the first animals to have an endoskeleton and voluntary, muscles in their body wall., They have well-developed sensory organs which include antennae,, sensory hair, simple or compound eyes, auditory organs and statocyst., They have well-developed endocrine system containing glands like, corpora cardiaca, corpora allata, etc., Mouth is always surrounded by mouth parts of different types in, different animals., Mouth Parts of Insects, , Piercing and, Sucking Type, e.g., mosquito, , Chewing, Type, e.g., beetle, , Rasping, Type, e.g., thrips, , Siphoning, Type, e.g., butterfly, , www.aiimsneetshortnotes.com, , Sponging and, Sucking Type, e.g., housefly
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60, , Telegram @neetquestionpaper, , Handbook of Biology, , Arthropods have special respiratory and excretory structures as follows, Antennary or green, glands, e.g.; crustaceans, , Respiratory Structures, Trachea, Book Lungs, Book Gills, Gills, e.g., insects e.g., scorpions. e.g.,prawns e.g., king crab., and some, and crabs., spiders., , l, , Excretory, Structures, , Malpighian tubules, e.g.; insects, Coxal glands, e.g.; scorpions and, most spiders, , Their nervous system possesses all the three types, i.e., central,, peripheral and autonomic., , Reproduction, Sexes are separate and fertilisation is internal. These animals are, generally oviparous or ovoviviparous., Development may be direct (e.g., cockroach) or indirect. Some, arthropods undergo parthenogenesis, e.g., drones of honeybee., , Classification of Arthopoda, Phylum–Arthropoda, Three sub-phyla, Trilobitomorpha, Chelicerata, Mandibulata, • Body is divided into, • Body is divided into, • Extinct group, cephalothorax and abdomen., cephalothorax (prosoma), and abdomen (opisthosoma),, • One or two pairs of antennae present., • One pair of mandible presents., cephalothorax is covered by a carapace., Antennae are absent., • Mandible absents., Three classes, Mesostomata, • Aquatic (marine), • Abdomen ends into, a spike-like telson,, e.g., Limulus and, Eurypterus., , Arachnida, Pycnogonida, • Mostly terrestrial,, • Marine, some parasitic., • Abdomen is reduced,, • Abdomen lacks, e.g., Pycnogonum., locomotory appandages., e.g., Aranaea, Palamnaeus, Four classes, , Crustacea, Chilopoda, • Terrestrial, • Mostly aquatic,, few are terrestrial • Body is divisible, or parasitic., into two part, i.e., head, • Body is divisible, and trunk., into two parts, i.e., • Exoskeleton is, cephalothorax, uncalcified., and abdomen., • One pair of Malpighian, • Exoskeleton is, tubule is present,, calcified., e.g., Scolopendra and, • Excretion by, Lithobius., green glands,, e.g., Cyclops and Sacculina., , Diplopoda, Insecta, • Terrestrial, • Found in all habitats., • Body is divisible into • Body is divisible, three parts, i.e., head,, into three parts, i.e.,head,, thorax and abdomen., thorax and abdomen., • Calcified, • Uncalcified, • Two pairs of Malpighian • Two to many, tubules present,, pairs of Malpighian, e.g., Julus and, tubules are present,, Glomeris., e.g., Mantis and, Lepisma., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Animal Kingdom, 61, Common and Scientific Names of Some Arthropods, Common Names, of Arthropods, , Scientific, Name, , Common Names, of Arthropods, , Scientific, Name, , Walking worm, , Peripatus, , Grasshopper, , Poecilocercus, , Prawn, , Palaemon, , House cricket, , Gryllus, , Spiny lobster, , Palinurus, , Praying mantis, , Mantis religiosa, , Brown crab, , Cancer, , Earwig, , Forficula, , Root-headed barnacle, , Sacculina, , Dragon fly, , Sympetrum, , Hermit crab, , Eupagurus, , Silkmoth, , Bombyx mori, , Goose-barnacle, , Lepas, , Yellow wasp, , Polistes, , Rock barnacle, , Balanus, , Honeybee, , Apis indica, , Silverfish, , Lepisma, , Millipede, , Thyroglutus, , Cockroach, , Periplaneta, , Centipede, , Scolopendra, , Desert locust, , Schistocerca, , Horseshoe crab, , Limulus, , Economic Importance, l, , l, , l, , l, , l, , Limulus is a living fossil., Honeybee produces wax and honey., Peripatus acts as a connecting link between Arthropoda and, Annelida., Prawn and lobster are used as food in many countries., Microtreme (white ant-termite) causes loss to furniture and other, wooden articles., , Phylum–Mollusca, Phylum–Mollusca is the second most abundant phylum which contains, soft-bodied animals usually protected by a calcareous shell and a, ventral muscular foot. The study of molluscs is called Malacology,, while study of molluscan shell is called Concology., , Peculiar Features, l, , l, , l, , l, , l, , They generally have an exoskeleton of calcareous shell which may, be internal or absent., Body is divisible into three parts, i.e., head, foot and mantle cavity., A glandular fold called mantle or pallium is present in the body wall., A rasping organ called radula is present in buccal cavity of most of, molluscs., A peculiar sense organ called osphradium check the quality of water., , www.aiimsneetshortnotes.com
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62, , Telegram @neetquestionpaper, , Handbook of Biology, , Respiration occurs by the following structures, Respiratory Structures, , Pulmonary sac, e.g., Limax., , Gills/Ctenidia,, e.g., Pila, Patella, , Gills + Pulmonary sac,, e.g., Pila., , Excretion occurs by 1 or 2 pairs of metanephridial tubules called, kidneys or organs of Bojanus. Pelecypods also have a large,, reddish-brown Keber’s organ in front of pericardium for excretion., Nervous system is formed of 3-paired ganglia, i.e., cerebral, pedal and, visceral ganglia., , Reproduction, Sexes are usually dioecious, but some are hermaphrodite, e.g., Doris,, Limax, etc. Most forms are oviparous, but only a few are viviparous, (e.g., Pecten). Fertilisation is external (e.g., Patella) or internal (e.g., Pila)., Development is either direct (e.g., all pulmonates and cephalopods) or, indirect including trochophore, (e.g., Chiton) or glochidium (e.g.,, Unio) or velliger (e.g., Dentalium) larvae., , Classification of Mollusca, , Monoplacophora, • Limpet-shaped shell, formed of single value., • Head bears tentacles,, but eyes are absent., • Radula is present., • Foot is broad and flat, and has 8 pairs of pedal, retractor muscles,, e.g., Neopilina., Amphineura, • Shell is formed of 8 plates., • Head is reduced and lacks, tentancles and eyes., • Radula is usually present., • Foot is large, flat and muscular., • Absent in some forms,, e.g., Chiton., , Scaphopoda, • Tusk-like shell opens at both sides., • Head is absent., • Radula is present., • Foot is conical-shaped for digging., e.g., Dentalium., Pelecypoda (Bivalvia), • Two-valved shell., • Head is absent., • Radula is absent., • Foot is wedge-shaped, and muscular for, Phylum–Mollusca, creeping or burrowing., • Absent in sedentary forms., e.g., Pecten., , Gastropoda, • Spirally coiled shell,, but absent in pulmonates., • Head bears both eyes, and tentancles., • Radula is present., • Foot is large and, flat for creeping, and attachment,, e.g., Pila., , Cephalopoda (Siphonopoda), • Externally spiral shell., • Well-developed, internal or, absent., • Head bears a pair of large, complex eyes., • Radula is present., • Foot is partially modified, into 8-10 suckers and, partially into siphon or funnel., e.g., Octopus., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Animal Kingdom, 63, Common and Scientific Names of Some Molluscs, Common Names of, Molluscans, , Scientific, Name, , Common Names of, Molluscans, , Scientific, Name, , Sea mussel, , Mytilus, , Sea lemon, , Doris, , Edible oyster, , Ostrea, , Grey slug, , Limax, , Cockle, , Cardium, , Squid, , Loligo, , Rock-borer, , Pholas, , Cuttlefish, , Sepia, , Razor clam, , Solen, , Devil fish, , Octopus, , Scallop, , Pecten, , Pearly nautilus, , Nautilus, , Ear shell, , Haliotis, , Tusk shell, , Dentalium, , True limpet, , Patella, , Coat of mail shell, , Chiton, , Sea hare, , Aplysia, , Economic Importance, l, , l, , l, , l, , Molluscans like oyster, squid and cuttlefish are used as food in, many countries., Shell of many molluscans is of ornamental value., Dentalium is used as decorative piece., Sepia ink has medicinal value., , Phylum–Echinodermata, It is a group of exclusively marine, spiny-skinned animals. These, triploblastic animals form the only phyla (except Chordata) which, contains true endoskeleton (mesodermal origin)., , Peculiar Features, l, , l, , l, , Adults with pentamerous radial symmetry, while larval forms with, bilateral symmetry., Great power of autotomy and regeneration., Body surface of five symmetrical radiating areas or ambulacra and, alternating between interambulacra. Ambulacra have tube feet for, locomotion, respiration, etc., , www.aiimsneetshortnotes.com
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64, l, , Telegram @neetquestionpaper, , Handbook of Biology, , The presence of water vascular system of coelomic origin., Ring-like vessel lying, around oesophagus, above peristome., Perforated by several, Madreporite, minute pores and, acts as water, inlet system., , Tube Feet Ampulla, Podium, Help in, locomotion Sucker, , Pentagonal, ring canal, , Rounded, yellowish, Tiedemann’s, body, glandular sacs,, total 9 in number in, Asterias, Filtering device., , Stone canal, Radial canal, , Lined by cilia or, flagella movement, of which draws, water into the canal., Bears tubefeet,, 5 in number., , Lateral, canals, , Connects tube feet, with radial canals., , Water vascular system in Asterias, , Degenerate Characters, l, , l, , l, , l, , Head, respiratory pigment and excretory organs are absent., Sense organs are poorly developed., Nervous system is formed of nerve plexi., Circulatory system is of open type., , Classification of Echinodermata, Phylum–Echinodermata, Five classes, , Asteroidea, , Ophiuroidea, , Echinoidea, , • Star-shaped, • Star-shaped, • Spherical, oval, or heart-shaped, body with, body with, body., pentagonal disc., rounded disc., • 5-50 arms, • 5-7 arms, • Arms are, absent., are present., are present., • Bipinnaria larva, • Pluteus, • Echinopluteus, larva,, e.g., Asterias., larva,, e.g., Echinus., e.g., Ophiothrix., , Holothuroidea, • Elongated and, cylindrical body., • Arms are absent., • Auricularia larva,, e.g., Holothuria., , www.aiimsneetshortnotes.com, , Crinoidea, • Contains mostly, extinct forms,, e.g., Antedon.
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Telegram @neetquestionpaper, Animal Kingdom, 65, Common and Scientific Names of Some Echinoderms, Common Names, of Echinoderms, , Scientific, Name, , Common Names, of Echinoderms, , Scientific, Name, , Starfish, , Asterias, , Basket star, , Gorgonocephalus, , Sea urchin, , Echinus, , Feather star, , Antedon, , Brittle star, , Ophiothrix, , Economic Importance, l, , l, , l, , Antedon is supposed to be a living fossil., Eggs of sea urchin are used for embryological studies., Sea cucumber is used as food in many countries., , Phylum–Hemichordata, It includes acorn worms or tongue worms. These are commonly called, half chordates or pre-chordates. They are exclusively marine,, mostly tubicolous, primitive chordates. They are bilaterally, symmetrical, triploblastic and enterocoelic true coelomates., , Peculiar Features, l, , l, , l, , l, , Body is divided into three regions, i.e., proboscis, collar and trunk., Their foregut gives out a thick and stiff outgrowth called, stomochord or buccal diverticulum., Excretion occurs by a proboscis gland or glomerulus present in the, proboscis in front of heart., Nervous system is of primitive type containing sub-epidermal nerve, plexus., , Reproduction, They mainly reproduce by sexual reproduction. Sexes are usually, separate and number of gonads varies from one to several pairs., Fertilisation is external. Development is direct or indirect with a, free-swimming tornaria larva., , Economic Importance, They show affinities with annelids, echinoderms and chordates., , Phylum–Chordata, Animals belonging to phylum–Chordata are characterised by the, presence of notochord, dorsal tubular nerve cord, gill-clefts and, post-anal tail. These four structures are found in the embryological, stages of all chordates., , www.aiimsneetshortnotes.com
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66, , Telegram @neetquestionpaper, , Handbook of Biology, , Notochord, It serves as a primitive internal skeleton. It may persist throughout, life, as in cephalochordata, cyclostomata and some fishes. It may be, replaced partially or completely by a backbone or vertebral column., , Dorsal Tubular Nerve Cord, It lies above the notochord and persists throughout life in most, chordates, but in a few it degenerates before maturity., , Gill Clefts, They appear during the development of every chordate, but in many, aquatic forms, they are lined with vascular lamellae which form gill for, respiration., , Post-anal Tail, An extension of the body that runs past the anal opening., In terrestrial chordates which never breathe by gills, traces of gill, clefts are present during early development, but disappear before adult, life., , Classification of Chordata, The various sub-phyla and divisions are already explained in the, chapter starting., Major classes of Chordata are discussed below, Pisces, Three classes, Chondrichthyes, , Osteichthyes, , Placodermi, , • Bony endoskeleton., • Cartilaginous endoskeleton., • Includes earlier fossils, • Exoskeleton comprises, • Exoskeleton is of placoid, • Body is with an external, cycloid, ctenoid or ganoid, protective armour of, scales (dermal origin)., scales (mesodermal origin)., bony scales or plates, • Mouth is placed ventrally., • Mouth is terminal., • Jaws are primitive with teeth,, • External nares are ventral, • External nares are dorsal, e.g., Climatius,, to head., to head., Palaeospondylus., • Caudal fin is heterocercal., • Caudal fin is homocercal., • 5-7 pairs of gills are present., • Four pairs of gills are present., • Swim bladder is absent., • Swim bladder is present., • Gills are not covered by, operculum., • Gills are covered by operculum., • Electric organs all absent, • Electric organs (e.g., Torpedo), • Mostly oviparous,, and poison sting (e.g., Trygon), e.g., Labeo (rohu), Clarias (magur),, are present., Pterophyllum (angel fish),Betta, • Mostly viviparous,, (fighting fish), Catla and Exocoetus (flying fish)., e.g., Scoliodon (dog fish),, Pristis (saw fish),, Trygon (sting ray), Carcharodon, (great white shark), Chimaera (rabbit fish) and Rhinobatos., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Animal Kingdom, 67, Tetrapoda, Four classes, Reptilia, , Amphibia, • Cold-blooded., • Skin is smooth ., , Aves, , • Cold-blooded., • Skin is cornified and, , • Warm-blooded., • Skin is covered, , Mammals, • Warm-blooded., • Skin is covered by, , and glandular., , covered with scales., , by feathers,, , epidermal hairs., , • Heart is with two, , • Heart consists of two., , • Heart contains, , • Heart contains two, , auricles and one, ventricle., • Respiration, occurs by lungs,, buccopharyngeal, cavity, skin and gills., • RBCs are nucleated., • They have largest, RBCs of animal, kingdom., • Two pairs of limbs,, each with five-toes., • Skull is dicondylic., • Fertilisation is, external,, oviparous., , auricles and partly, divided ventricle., , • Respiration occurs, by lungs., , • RBCs are nucleated., • Two pairs of, pentadactyl limbs,, each with 5 digits, bearing claws, corneoscutes. In, snakes, limbs are, absent., • Skull is monocondylic., • Thecodont teeth., • Fertilisation is, internal,, oviparous., , two auricles and, two ventricles., , auricles and two, ventricles., , • Respiration occurs, , • Respiration occurs, , by lungs provided, by air sacs., • RBCs are nucleated., • Forelimbs are modified, to wings and hindlimbs, are modified for walking,, swimming and pearching., • Hindlimbs bear claws, and scales., • Skull is monocondylic., • Teeth are absent and, upper and lower jaws, are modified into beak., • Fertilisation is internal,, oviparous., , by lungs., , • RBCs are, enucleated., , • Quadruped limbs, whose digit ends, with claws or nails, or hooves., • In whales and, dolphins, limbs, are absent., • Skull is dicondylic., • Thecodont, heterodont, and diphyodont teeth., • Fertilisation is internal,both, oviparous and viviparous., , Amphibia, Class-Amphibia consists of two sub-classes, i.e., Stegocephalia, (extinct) and Lissamphibia (modern living amphibians). In contrast, to Stegocephalia whose skin bears scales and bony plates,, Lissamphibians do not possess bony dermal skeleton., Lissamphibia is further divided into three orders as follows, Lissamphibia, Three orders, Apoda/Gymnophiona/Caecillians, • Also called limbless amphibians., • Long worm-like, burrowing, dermal, scales present in skin., , • Tail short or absent, cloaca terminal., • Skull compact, roofed with bone., • Males have protrisible copulatory organ., • Larva has 3 pairs of external gills,, gills also present in adult stage., • e.g., lchthyophis (blindworm),, Ureotyphus., , Anura/Salientia, , •, •, •, •, •, •, •, •, •, , Urodela/Caudata, • Also called tailed amphibians., , Also called tail-less amphibians., Commonly includes frogs and toads., Forelimbs shorter than hindlimbs., Adults without gills., Skin loosely fitting, scaleless, teeth, present only on upper jaw or absent., Vertebral column very small of 5-9 procoelous., Vertebrae and a slender urostyle., Fertilisation always external., Full metamorphosis without neotenic forms, e.g., Rana, Bufo, Hyla and Rhacophorus., , Lizard-like, limbs two pairs of weak and equal size., , • Commonly called newts and salamanders., • Skin devoids of scales and tympanum., • Possesses largest RBC., • Gills permanant or lost in adults., (Necturus, Proteus, Siren and Axolotl larva have external gills)., Fertilisation is internal., • Larva aquatic, adult-like with teeth,, • e.g., Nectunes, Salotrandra and Ambystoma., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Animal Kingdom, 69, Their sternum is large and bears a keel for the attachment of flight, muscles. They do not possess skin glands except the cutaneous oil, glands or green glands (or uropygial glands) that are located at the, root of the tail. These glands are absent in parrot and ostrich., Class–Aves is further divided into sub-classes and orders as follows, Class–Aves, Two sub-classes, , Archaeornithes, (Gk. archios–ancient;ornithes–bird), Includes extinct (in Mesozoic era) birds,, homodont (same type of teeth) teeth in, both the jaw, long tapering tail, weak,, vertebrae are amphicoelous, keeled, sternum, non-pneumatic bones, hand, with clawed fingers wings are primitive, with little power of flight, e.g., Archaeopteryx, lithographica (ancient or lizard bird) and, Archaeornithes., , Odontognathae, , Palaeognathae, , (Extinct cretaceous, birds), jaw bears teeth, •, for catching fish., e.g., Hesperornis,, Ichthyornis., , (Flight less running, birds), Wings vestigial or, rudimentary, feathers, without any interlocking, mechanism., Oil gland is absent, except in Tinamus, and kiwi., Sternal keel is, vestigial, flat or, raft-like., Pygostyle is penis, or reduced., Syrinx is absent., Male has a penis,, e.g., Struthio camelus, (African ostrich),, Rhea americana, (American ostrich),, Dromaeus (emu),, Casurarius (cassowary), Apteryx (kiwi), Tinamus, (tinamou)., , •, , •, , •, •, •, , Neonithes, (Includes extinct as well as living birds), Teeth absent except in some fossil birds,, wings are well-developed and adapted, for flight, tail short and reduced, fingers of, the wings are without claw., , Four super-orders, Impennae, , Neognathae (Carinatar), , • The super-order, includes modern, aquatic flightless, birds with paddlelike wings or flippers., • Feet are webbed., • The skeleton is solid,, air sacs are absent., • The integument is a, fatty insulating layer,, e.g., Aptenodytes, (emperor penguin),, Eudyptes, (rock hopper penguin)., , • Modern flying birds,, with well-developed, wings and feathers with, interlocking mechanism., • Sternum with, developed keel., • Males have no, copulatory organ., • Some important order, of flying birds are, Gaviiformes,, e.g.,divers., Procellariiformes,, e.g., albatross., Anseriformes,, e.g.,swans, geese, and ducks., Falconiformes,, e.g.,vultures, eagles,, hawks and falkons., Gruiformes., e.g., pheasants., Columbiformes,, e.g., pigeons., Psittaciformes,, e.g., parrots., Cuculiformes,, e.g.,cuckoo., Coraciiformes,, e.g., kingfishers., Passeriformes,, e.g., crow and thrashers., , www.aiimsneetshortnotes.com
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70, , Telegram @neetquestionpaper, , Handbook of Biology, , Flight Adaptation in Birds, In birds almost every system is modified to support flight as given, under, The feathers constitute very smooth covering over the body to reduce, the friction of air. Due to non-conducting nature of these, body, temperature is maintained. Feathers of tail (rectrices) form fan-like, structure and steer the body during flight., Wings (remiges) act as main organ of flight with association of, feathers. They are responsible for supporting the bird during the, flight. Remiges are attached by ligament or directly to the bone., The bones are light, hollow and provide more space for the muscle, attachment., l, , l, , l, , Types of Feathers, Body in birds is covered by feathers made up of keratin protein. An, arrangement of feathers on the body of birds is called pterylosis. An, outline of these feathers are as follows, 1. Contour feathers These are small feathers that cover the body,, wings and tail. Each contour feather has a central axis and a vane., 2. Flight feathers or Quills These are useful in flights and can be of, following types, (i) Remiges These are large wing feathers and further, categorised to, (a) Primaries which are attached to the bones of the hand., (b) Secondaries which are attached to the bones of the, forearm., (c) Tertiaries which are attached to the humerus of upper, arm bone., (ii) Retrices These are large tail feathers., (iii) Coverts These are found at the edge of remiges and, rectrices., 3. Filoplumes These are hair-like feathers scattered over body surface, and lie between the contour feathers. These act as sensory organs,, registering pressure and vibration., 4. Bristles Modified filoplumes found in certain birds near nostrils and, eyes. These are used as a touch sensor or funnel that makes the bird, reflexively snap up food., 5. Down feathers Found only in the newly hatched birds. These form, their first feathery covering, which provides insulation., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Animal Kingdom, 71, Mammalia, Class–Mammalia is considered to be superior of all animal groups., This class is further divided into two sub-classes., The detailed classification of class–Mammalia is as follows, Class–Mammalia, Sub-classes, , Prototheria, , Theria, , (Most primitive mammals), • Oviparous, • No pinna, • No nipples, • No marsupial pouch, • Digestive and urinogenital, tracts open into a cloaca,, cloacal opens outside, through cloacal aperture, • Corpus collosum is feebly, developed or absent, • Testes abdominal, no, scrotum., • No placenta ., Order, , Monotremata, (connecting link between, reptile and mammals), e.g., Ornithorhynchus, (duck-billed platypus),, Tachyglossus or Echidna, (spiny anteater)., , Infra-classes, , Metatheria, (Australian mammals), • Viviparous, • Pinna presents, • Nipples abdominal, • Marsupial or abdominal, pouch often present., • Anus and urinogenital, aperture open into a shallow, cloaca surrounded by a, common sphincter., • Corpus callosum is not, developed or absent., • Testes extra abdominal, scrotum, lies anterior to penis., • Placenta is less developed., , Eutheria, (Placental mammals), • Viviparous, • Pinna usually presents, • Nipples abdominal or thoracic, • Marsupial pouch absent, • Digestive and urinogenital, tracts open out be separate, apertures., • Corpus callosum is well developed., • It connects two hemisphere, internally., • Testis extra abdominal, scrotum, lies below to penis., • Placenta is less developed., , Order, , Marsupialia, (pouched mammals), e.g., Macropus (kangaroo),, Phascolarctos (kolabear),, Didelphys (opossum)., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 5, , Morphology of, Flowering Plants, Plant Morphology : An Overview, Flowering plants or angiosperms show large diversity in external, structures or morphology. A generalised morphology of these plants is, as follows, Contains shoot apical, meristematic tissue, which, helps in apical dominance., , Shoot tip, (apical bud), , Reproductive organ,, contains four whorls as,, sepal, petal, androecium, and gynoecium, serves the, Flower purpose of reproduction., , Lateral bud, , Grows in underside of leaf, bases, forms new branch., Stem, Leaf Seeds, Fruit, , The main erect axis of, plant, bears almost all, organs like leaf, fruit,, flowers etc., , Photosynthetic organ,, possesses chlorophyll,, mainly of two types–, simple and compound,, lamina and petiole are, main parts., Fertilised ovary,, protects the seeds and, carry out the pollination., , Node, Internode, , Tap root of plant, carries, the lateral roots and root, Primary root, Secondary root, Also called fibrous, Root tip, root, supports the, Contains root apical, main root., meristem, a tissue of, meristematic nature., , Root hair, , Thread-like structures, in root to absorb water, Root cap, and minerals., Protects root tip, from damage., , A typical flowering plant, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Morphology of Flowering Plants, 75, Various components of plant’s morphology and their structures are, discussed here., , Root, It is generally a non-green, underground, positively geotropic,, positively hydrotropic and negatively phototropic, descending, cylindrical axis of the plant body which develops from the radicle of, the embryo. It is without node, internode, leaves, buds, flowers and, fruits. Its main function includes anchorage to the plant along with, water and mineral absorption., , Structure of Root, Generally, the root in plants is divided into three main regions. These, are, , 1, Region of, maturation, , It is also known as zone of, differentiation. The cells from, this region develop into, permanent tissue., These have root hair around them., , Root hair, , 2, Region of, elongation, , 3, Region of, meristematic, activity, , Root cap, , The region is just above the, meristematic zone. The cells, of this region are elongated and, contain large vacuole., It is also known as meristematic, zone. The cells are in active state, of division. These are thin-walled,, have dense cytoplasm, and large nucleus., , The regions of the root-tip, , Root cap A smooth cap-shaped structure to provide protection to the, young apical cells against soil particles is called root cap., , Types of Root, There are two types of root, (i) Tap root Primary root further branches into secondary and, tertiary roots, e.g., dicotyledonous root., (ii) Adventitious root In this, the radicle dies immediately after, germination, hence these roots arise from different portions of, the plant, e.g., monocotyledonous root., , www.aiimsneetshortnotes.com
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76, , Telegram @neetquestionpaper, , Handbook of Biology, , Modifications of Roots, Both, tap roots and fibrous roots are modified, according to their need., , 1. Modifications of Tap Roots, , Tap root, Tuber root, , Secondary root, , Tuberous, e.g., Mirabilis, etc., , Fusiform, e.g., radish, etc., , Nodule, , Storage root, , Nodulated, , Tap Root, , Conical, e.g., carrot, etc., , e.g., gram, pea,, peanuts, arhar, etc., , Napiform, e.g., turnip, sugarbeet, etc., , Secondary root, , Pneumatophores, e.g., Rhizophora, etc., , Stem, , Pneumatophores, , Pores, , Storage roots, Secondary root, , Respiratory roots, Various modifications of tap root, l, , l, , Pneumatophores are present in plants of coastal habitat. These, roots absorb oxygen., Nodulated roots in leguminous plants form nodules after, combining with nitrogen-fixing bacteria. They are meant for, nitrogen-fixation., , 2. Modifications of Adventitious Roots, (i), (ii), (iii), (iv), , Tuberous From the nodes of the stem, e.g., sweet potato., Fasciculated Arise in bunches, e.g., Asparagus, Dahlia., Beaded root Swell at different places, e.g., Vitis,. bitter gourd, etc., Nodulose Apical portion swells up, e.g., Curcuma, maranta etc., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Morphology of Flowering Plants, 77, (v) Annular Ring structure formed, e.g., Psychortia, cephaelis., (vi) Prop roots Roots hang from branches and penetrate into soil,, e.g., Ficus, banyan., (vii) Stilt Roots They arise from stem and enter into soil, e. g., maize,, sugarcane, etc., (viii) Climbing roots Arise from nodes, e.g., Pothos, piper bettle., (ix) Buttress roots Arise from basal part of main stem, e.g., Bombax., (x) Contractile roots Underground and fleshy, e.g., onion, etc., (xi) Sucking roots In parasites, e.g., Cuscuta., (xii) Epiphytic roots Found in epiphytes, e.g., orchids., (xiii) Floating roots Arise from nodes, help in floating, e.g., Jussiaea., (xiv) Photosynthetic roots Have chlorophyll, e.g., Trapa, Tinospora., (xv) Reproductive roots Develop vegetative buds, e.g., Trichosanthes, dioica., (xvi) Mycorrhizal roots With fungal hyphae, e.g., Pinus., (xvii) Thorn roots Serves as protective organ, e.g., Pothos., (xviii) Clinging roots Arise from node and pierce into host plant,, e.g., Orchid, Ivy etc., (xix) Leaf roots From margin of leaves, e.g., Bryophyllum., , Stem, It is the ascending cylindrical axis of plant body which develops from, the plumule of the embryo and grows by means of terminal bud. This, is usually negatively geotropic and positively phototropic. Its major, function is to conduct water, minerals and photosynthates and to, support the plant body., , Stem Branching, There are two types of branching, Stem Branching, Dichotomous, , Lateral, , (two similar branches arise), 3 3, 3, , (two different branches arise), 2, , 3, , 2, , 2, 3, , 2, , 2, , 2, , 2, 3, 3, 1, , 1, , Branching patterns in stem, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 78, , Handbook of Biology, , Types of Stem, Stems are of three types, 1. Aerial, 2. Sub-aerial 3. Underground, Different types of stems, actually are the modified stem. The, modifications are to serve various purposes like perennation,, vegetative reproduction and storage of food., , 1. Aerial/Epiterranean Stem Modifications, These are of following types, (i) Stem tendril In weak plants with weak stem, the apical bud, is modified into tendril for climbing, e.g., Vitis, Passiflora, etc., (ii) Phylloclade In this, the stem is modified into flat, fleshy and, green leaf-like structure, e.g., Opuntia, Cocoloba, Ruscus, etc., (iii) Stem thorn Axil of the leaf or apex of the branch is modified, into pointed structure called thorn, e.g., Citrus, Bougainvillea,, etc., (iv) Cladode Stem is modified into leaf-like structure, e.g.,, Asparagus., (v) Bulbil A multicellular structure functions as organ of, vegetative reproduction, e.g., Oxalis, Dioscorea, etc., Stem tendril, (axillary), Thorn, , Spiny, leave, , Leaf, Weak stem, , Fleshy stem, (a), , (b), , (c), , Spines, , Leaf, , Stem, , (d), , Bulbil, , (e), , Aerial stems : (a) Stem tendril in Vitis, (b) Phylloclade of Opuntia,, (c) Stem thorn of Bougainvillea, (d) Cladode in Asparagus,, (e) Bulbil in Dioscorea, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 79, Morphology of Flowering Plants, 2. Sub-Aerial/ Prostrate Stem, These are of following types, Internode, , Lamina, Spongy, petiole, , Leaf, , Offset, , Offset, , Roots with, pocket, , Adventitious, roots, , Runner, , Stem (runner), , e.g., Cynodon, Oxalis, Hydrocotyle, , Adventitious roots, e.g., Pistia, Eichhornia, etc., , Sucker plant, , Stem, , Mother plant, Leaves, , Internode, , Stolon, , Aerial, shoot, , Sucker, , Stolon, Node, , Node, , Scale, , Sucker, , Crownleaf, , Adventitious, roots, , e.g., Colocasia, strawberry, etc., e.g., rose, mint and Chrysanthemum, , Sub-aerial modifications in stem, , 3. Underground/Subterrannean Stem, These are of following types, Scaly leaves, Base of scape, Tunic, , Buds, , Bulb, , Adventitious, Roots, e.g., onion, garlic, lilies, etc., , Bulb, , Stem, , Node, Internode, Scale leaf, Corm, Daughter, corm, Adventitious, roots, e.g., Colocasia, etc., , Rhizome, , Corm, , Adventitious, Nodes, roots, e.g., ginger, turmeric, lotus, etc., , Young shoot, Eyes, Germinating, eye buds, , Tuber, , Roots, e.g., potato, , Underground modifications in stem, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 80, , Handbook of Biology, , Leaf, It is an exogenous, lateral, generally flattened outgrowth that arises, from the node of the stem and bears a bud in its axil. The leaves are, the most important vegetative organs for photosynthesis and also, perform gaseous exchange and transpiration., , Parts of Leaves, A typical leaf has three main parts, (i) Leaf base, , Part of leaf attached to the stem by the leaf base., , (ii) Petiole Part of leaf that connects lamina to stem., (iii) Lamina or leaf blade Flattened part of the leaves, which, contains veins., Leaf apex, Leaf margin, Leaf blade, Leaf lamina, , Vein, Midrib, Veinlet, Petiole, Stipule, , Node, , Leaf base, Stem, , Typical leaf with its parts, , Leaf Venation, The arrangement of veins in lamina is known as venation., Venation, , Pinnate, (single midrib giving, rise to lateral veins), , Palmate, (multiple midribs dividing, into veinlets giving an, extensively reticulated pattern), , 123, In dicots, , Parallel, (veins run parallel, to each other within, a lamina), , In monocots, , Different venation patterns in leaves, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Morphology of Flowering Plants, 81, Types of Leaves, On the basis of incision of lamina, leaves may be of two types, , 1. Simple Leaves, In this, there is a single lamina, which is usually entire, e.g., mango,, guava, Cucurbita, etc. fig. (a)., , 2. Compound Leaves, In this type of leaves, the incision of lamina, reaches up to midrib or, petiole, e.g., rose, neem, lemon, etc., These are of two types, (i) Pinnately compound leaves (a number of leaflets present on, rachis representing midrib of the leaf) fig. (b)., (ii) Palmately compound leaves (leaflets attached at a common, point, i.e., at the tip of petiole) fig. (c)., , Midrib, Leaflet, Lateral bud, , (a) Simple leaf of lilac, , (b) Pinnately compound leaf, of neem, , Petiole, Stipule, , (c) Palmately compound, leaf of strawberry, , Types of leaves, , www.aiimsneetshortnotes.com
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82, , Telegram @neetquestionpaper, , Handbook of Biology, , On the basis of origin and function, leaves are of the following types, Leaves, Cotyledonary, Leaves, e.g., Riccinus, Geranium, , Bract Leaves, or, Hypophylls, e.g., Euphorbia,, Bougainvillea, , Scale Leaves, or, Cataphylls, e.g., ginger, , Bract leaves, , Cotyledonary, leaves, , Scaly, leaves, Prophylls, e.g., Agave, , Floral Leaves, or, Sporophylls, e.g., sepals, petals, etc., in most angiosperms., , Foliage Leaves, e.g., green, photosynthetic, leaves in almost, all plants., , Floral leaves, , Foliage leaf, , Types of different functional leaves, , Phyllotaxy, Arrangement of leaves on main stem or branches is known as, phyllotaxy. There are 5 main types of phyllotaxies, reported in plants., The various phyllotaxies can be understood through following figures, , (a), , (b), , (c), , (d), , (e), , Types of phyllotaxy (a) Cyclic (b) Alternate (c) Opposite, decussate, (d) Opposite superposed (e) Whorled or verticillate, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Morphology of Flowering Plants, 83, Modifications of Leaves, Leaflet, , Lid, , Leaf bladder, , Stem, Pitcher, , e.g., Nepenthes,, Sarracenia, etc., , e.g., Utricularia ,etc, , Phyllode, (Petiole), , e.g., Australian Acacia,, Parkinsonia, etc., , Pitcher, leaves, , Bladder, shaped, leaves, , Phyllode, Leaf tendril, , Leaves, , Leaf hooks, , Leaf tendril, e.g., Pisum,, Lathyrus, etc., , e.g., Bignonia,, Asparagus, etc., Leaflets, , Fleshy leaves, Scale leaves, Leaf thorn, Stolon, , Scale, Leaf, e.g., Hydrilla,, Vallisnaria, etc., , Fleshy, leaves, , Leaf, thorn, , e.g., Onion,, garlic, etc., , e.g., Acacia, Cactus, etc., , Various leaf modifications, , Inflorescence, The Shoot Apical Meristem (SAM) changes into floral meristem to form, a flower and this flower bearing branch is called peduncle. The, arrangement of flowers on floral axis is termed as inflorescence., It can also be defined as ‘system of branches bearing flower.’, , www.aiimsneetshortnotes.com
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86, , Telegram @neetquestionpaper, , Handbook of Biology, , Special Inflorescence, These are of unique type of inflorescences., Male flowers, Female flower, , Nectar gland, , Cyathium Pedicel, , Hypanthodium, , Bracteoles, Involucre, of bracts, , Receptcle become pear shaped., e.g., banyan, peepal, fig, etc., , Special, Inflorescence, , Peduncle, In this, five involucre become, fused and form a cup-like structure, e.g., Euphorbiaceae., , Verticillaster, , Coenanthium, , Leaf, Bracts, Flowers, , Verticillaster, Stem, In this, the receptacle become saucer-shaped,, e.g., Dorstenia benguellensis, etc., , It is a modified condensed dichasial cyme,, e.g., Salivia, Ocimum, Coleus, etc., , Various types of special inflorescences, , Flower, It is the reproductive part of an angiospermic plant. It develops in the, axis of a small leaf-like structure called bract., , Structure of a Flower, A complete flower is a modified condensed shoot, which is situated on, receptacle (thalamus). It is a beautiful, reproductive organ that serves, the purpose of attracting pollinators., Petal (corolla), , Pistil Stigma, (Gynoecium) Style, , Anther, Stamen, Filament (Androecium), , Sepal (calyx), Pedicel, , Ovary, , A flower showing detailed structure, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Morphology of Flowering Plants, 87, Parts of a Typical Flower, Every flower normally has four floral whorls, i.e, calyx, corolla,, androecium and gynoecium. All whorls are arranged on the swollen, ends of the stalk, called thalamus., The details of these parts are as follows, , 1. Calyx (Sepals), It is the outermost whorl of floral leaves and the individual segment is, called sepal. Mostly they are green in colour, but sometimes they are, coloured like petals (petaloid)., Sepals free from each other – Polysepalous, Sepals fused with each other – Gamosepalous, l, , l, , Modifications of Sepals, Sepals undergo following modifications, (a) Pappus Hair-like modified sepals particularly for the dispersal, of fruits, e.g., sunflower, Tagetes, Tridex., (b) Spinous Spine-like, e.g., Trapa., (c) Tubular Tube-like, e.g., Datura., (d) Spurred A tubular outgrowth called spur, arises at the base of, one of the sepals, e.g., Delphinium (larkspur)., (e) Campanulate Bell-shaped, e.g., China rose., (f) Leaf One sepal becomes leaf-like, e.g., Mussaenda., (g) Hooded One sepal becomes hood-like, e.g., Aconitum., (h) Cupulate Cup-like, e.g., Gossypium., (i) Bilabiate Like two lips of mouth, e.g., Salvia, Ocimum., (j) Infundibuliform Like funnel-shapped, e.g., Atropa., (k) Ureolate Urn-like, e.g., Silene., , 2. Corolla (Petals), This is the second whorl which arises inner to the calyx. The petal and, sepal together form the floral envelope., Note Both petals and sepals combinely called perianth. When petals and, sepals are not differentiated clearly, it is called tepal., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Morphology of Flowering Plants, 89, 3. Androecium (Male Reproductive Organ), This is the third whorl of floral appendages, that arises inner to, corolla. Individual appendage is called stamen which represents the, male reproductive organ., There are different types of stamens, on the basis of various criteria, Types of Stamens, Cohesion of, Stamens, , 1. Polyandrous, , On the Basis of, Fixation of Filament, , 1. Adnate, , Length of Stamens, , 1. Didynamous, Stamen, Among 4, two stamens are small and, 2 are large., , Stamens are free,, e.g. mustard, radish., , 2. Adelphous, , 2. Basifixed, , 2. Tetradynamous, Stamen, , Filaments fused but, anthers are free,, e.g., Malvaceae, etc., , Among 6, two stamens are small and, 4 are large., , 3. Synandrous, 3. Dorsifixed, Stamens are united, in whole length, e.g., Cucurbitaceae., , 4. Syngenesious, Anthers united but, filaments are free,, e.g., Compositae., , 4. Versatile, , Various types of stamens, , www.aiimsneetshortnotes.com
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90, , Telegram @neetquestionpaper, , Handbook of Biology, , 4. Gynoecium (Female Reproductive Organ), It is the innermost floral whorl which acts as female reproductive, organ of the flower. On the basis of number of carpels and their, arrangement, the gynoecium is of following types, Types of Gynoecium, , Apocarpous, , (with free or, separate carpels), , Semicarpous, , Syncarpous, , (with fused, ovaries, of adjacent, carpel and, free style and, stigma), , (with fused, carpels), , Synovarious, , Synstylovarious, , (ovaries of, adjacent, carpels, are fused,, but their, style and stigma, are separate), , Unicarpellous, , (ovaries, and, style are, fused,, stigma, separate), , (Stylodious), , Terms Related to Flower Structure, 1. Actinomorphic flower When the flower is regular, and radially symmetrical, it is termed as actinomorphic,, e.g., mustard (Cruciferae), onion (Liliaceae), brinjal (Solanaceae)., 2. Asymmetric flower Flowers, which cannot be divided into, two equal halves by any vertical division, e.g., Canna., 3. Zygomorphic flower When the flower is bilaterally, symmetrical, i.e., divisible into only two equal halves by a single, vertical plane, it is termed as zygomorphic, e.g., Adhatoda, pea,, larkspur, Ocimum., , (a), , (b), , Symmetries in flowers (a) Actinomorphic (b) Zygomorphic, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Morphology of Flowering Plants, 91, 4. Hermaphrodite or intersexual or bisexual or monoclinous, flower A flower is called bisexual when it contains both male, and female reproductive organs, e.g., China rose, mustard, etc., 5. Unisexual or dioecious flowers A flower is called unisexual, when it has only one essential floral whorl, either androecium, (staminate or pistalloide) or gynoecium (pistillate or, staminoide), e.g., Morus alba, papaya, Cucurbita, etc., 6. Complete and incomplete flowers A flower is called complete, when it contains all the floral whorls, i.e., calyx, corolla,, androecium and gynoecium, e.g., Solanum, mustard. While the, flower in the absence of any one of these four floral whorls, is, called incomplete flower, e.g., Cucurbita., 7. Regular and irregular flowers When the flowers of a plant, have same size, shape, colour and arrangement of various floral, whorls/organs, then the flowers are called regular. If flower of a, plant shows dissimilarity in any of its part or trait, then the, flowers are called irregular., 8. Cyclic and acyclic flowers When the floral parts of a flower, are arranged in a whorl, the flower is called cyclic,, e. g. , Solanum. If the floral part of a flower are arranged spirally, and not in whorls, the flower is called acyclic, e.g., Ranunculus,, Opuntia, Nymphaea., 9. Achlamydeous, monochlamydeous and dichlamydeous, flowers In achlamydeous flowers, the accessory floral whorls, (calyx and corolla) are absent, e.g., Piper sp. (Piperaceae)., When a flower contains only one accessory whorl (either calyx, or corolla) or perianth (a collective term given to a, group of undifferentiated calyx and corolla), it is called, monochlamydeous, e.g., Polygonum (Polygonaceae), onion, (Liliaceae)., The condition dichlamydeous is used when both the accessory, whorls (calyx and corolla) are present, e.g., in most of the, flowers., 10. Isomerous and heteromerous flowers When the parts of a, floral whorl are found in a particular basic number or its, multiple, the situation is called isomery and the flower is, isomerous., , www.aiimsneetshortnotes.com
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92, , 11., , 12., , 13., , 14., , Telegram @neetquestionpaper, , Handbook of Biology, , An isomerous flower may be dimerous (2 or multiple of 2),, e. g. , poppy or trimerous (3 or multiple of it), e.g., Argemone or, tetramerous (4 or multiple of 4), e.g., Solanum. A flower is, called heteromerous, when different parts of different floral, whorls have different basic number of its multiple., Hypogynous, perigynous and epigynous ovary A flower is, called hypogynous, when the innermost floral whorl, (gynoecium) occupies the highest position (superior) while, corolla and calyx successively arise below it (inferior). e.g.,, Brassica, China rose, Papaver, Citrus, Solanum, cotton, etc., In perigynous flower, all the floral whorls occurred at the same, level of height on the thalamus so, they are called half superior, or half inferior, e.g., rose, peach, Prunus., In an epigynous flower, the innermost whorl, i.e., gynoecium is, covered by the elongated margins of thalamus., Thus, its position is inferior in relation to other floral whorls,, which arise above the ovary and thus superior, e.g., sunflower,, Cucurbita, coriander, etc, Bracteate and ebracteate flowers Bract is a small leaf-like, structure, whose axil bears a pedicel (flower stalk). A flower, containing bract is called bracteate, e.g., Adhatoda and without, bract it is called ebracteate, e.g., Solanum., Bracteolate and ebracteolate A pedicel sometimes bears a, pair of bracteoles, which are often green, sepal-like structures. A, flower with bracteoles, is called bracteolate and without, bracteoles, it is termed as ebracteolate., Epicalyx It is an additional whorl of bracteole-like structures,, which are found exterior to the sepals, e.g., China rose, cotton, (Malvaceae)., , Placentation, The arrangement of ovules within the ovary is called placentation. The, placenta is a tissue which develops along the inner wall of the ovary., The ovule remains attached to the placenta., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Morphology of Flowering Plants, 93, It is of following types, Ovary wall, Locule, , Placenta, , Ovule, , Septum, Ovules, , Locule, , Superficial, , Marginal, , Ovary wall, , Locule, , Locule, Ovule, , Placenta, , Placenta, , Basal, , Parietal, Ovule, , Free central, Ovary wall, Locule, Ovule, , Placenta, Central axis, , Axile, Ovule, Central axis, Placenta, Locule, Ovary wall, , Types of placentations in flowering plants, , Fruit, After fertilisation of ovary, ovule is changed into seed and ovary into, fruit. The fruit is a characteristic feature of the flowering plants., A true fruit is a ripened ovary. At this stage, the perianth and stamens, fall off, the gynoecium is rearranged and ovary becomes extended., Generally the fruit consists of a wall or pericarp and seeds., Sometimes this pericarp is differentiated into three layers, 1. Outer – Epicarp 2. Middle – Mesocarp 3. Inner – Endocarp, On the basis of their development, the fruits are of two types, 1. True Fruits These fruits develop from the ovary of flower, e.g.,, mango, orange, etc., 2. False Fruits The floral parts other than ovary develop into, fruit, e.g., apple and pears, etc., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Morphology of Flowering Plants, 99, These are of following types, , Sorosis, , Syconus, , Ostiole, , Crown of, scale leaves, , e.g., pineapple,, mulberry, etc., , Female, flower, , Gall, flower, , Male, flower, , Multiple fruits, e.g., Anjir, peepal, banyan, etc., , Seed, It is a small embryo enclosed in a covering called seed coat, usually, with some stored food. The formation of seed completes the process of, reproduction in seed plants., , Parts of a Seed, A seed contains an embryo, an endosperm and a seed coat., Embryo It represents an embryonic plant. It consists of an axis, called tigellum to which embryonic leaves or cotyledons are, attached., Endosperm If present, acts as the food storage tissue of a seed., Seed coat It is a protective covering of the seed made up of one or, two layers. The outer layer is called testa and inner is called, tegmen. A minute opening called micropyle is present in seed, coat., l, , l, , l, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Morphology of Flowering Plants, 101, Semi-technical Description of a Typical Flowering Plant, Various morphological features of a plant, need to be described in a, scientific language. Following table clearly explains almost every sign, used in floral description, Br, , Bracteate, , CA, , Epipetalous stamens, , Ebr, , Ebracteate, , PA, , Epiphyllous stamens, , Brl, , Bracteolate, , Std, , Staminodes, , Ebrl, Epi, , Ebracteolate, Epicalyx, , G4, , Tetracarpellary, free carpels,, apocarpous, , G (4 ), , Tetracarpellary, syncarpous, , 0, Absence of a particular whorl, (zero), ∝, , Indefinite number, , ⊕, , Actinomorphic, , (superior), K (n ), , Calyx united (gamosepalous), , G (4) − Tetracarpellary, syncarpous, (semi inferior), , %, , Zygomorphic, , C (n ), , Corolla united (gamopetalous), , %, , Male flower, , G (4), , Tetracarpellary, syncarpous ovary, inferior (epigynous), Tetracarpellary, syncarpous,, , O, +, , Female flower, , %, +, , Bisexual flower or hermaphrodite, condition, , G (4), , Kn, , Calyx, where n = number of sepals, , Pistd., , Pistillode, , Cn, , Corolla, where n = number of petals, , AG, , Androecium and gynoecium are, united, , ovary either superior or inferior, , A(n), , P, , Perianth, , An, , Androecium, where n = number of, stamens, , 2+4, , 2 in one set and 4 in another, , Gn, , Gynoecium, where n = number of, carpels, , 2– 4, , 2 or 4, , (), , Cohesion of floral parts in a whorl, , X, , Variable, , Androecium with fused stamens, , Floral Formula, It represents the structure of as flower using numbers, letters and, various symbols., , Floral Diagram, It represents the number of organs of a flower, their arrangement and, fusion. It is useful for flower identification., , Description of Some Important Families, Various workers have divided both monocots and dicots into several, families. For proper understanding of these families, the comparative, account of 5 families is presented here., , www.aiimsneetshortnotes.com
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The family is also termed, as pea family. It is, distributed all over the, world., , Tree, shrub, herb., , Root with root nodules., , Erect or climber., , Alternate, pinnately, compound or simple,, venation reticulate., , Racemose, , Bisexual, zygomorphic., , Five, gamosepalous,, imbricate., , Five, polypetalous,, papilionacous., , Plant structure, , Root structure, , Stem structure, , Leaves, , Inflorescence, , Flower, , Calyx, , Corolla, , Fabaceae, , General, Description, , Characteristics, , www.aiimsneetshortnotes.com, Five united valvate., , Five united,, persistent, valvate., , Bisexual,, actinomorphic., , Solitary, axillary or, cymose., , Alternate, simple, exstipulate, venation, reticulate., , Malvaceae, , Annual, biennial and, perennial herbs., , Erect, branched sturdy, with trichomes, sometimes, decumbent., , —, , 6 tepals arranged in, two whorls (3 + 3)., Free or rarely united, valvate., , Bisexual,, actinomorphic., , Solitary/cymose often, umbellate clusters., , Four, polypetalous, cruciform., , Four, polysepalous in, two whorls., , Bisexual, actinomorphic, (may be zygomorphic)., , Raceme or corymb., , 5 petals, free but baselly, adnate., , Calyx-like whorl called, epicalyx., , Bisexual, actinomorphic,, pentamerous., , Cymose or Raceme., , Mostly basal, alternate, Simple, alternate, rarely Simple, palmately lobed,, linear, parallel, opposite, reticulate, reticulate venation., venation., venation., , Herbaceous stem with, pungent watery fluid., Have stellate hairs., , Profusely branched, taproot., , All herb, shrub and trees., , It is known as mustard Also known as mallow, family or Brassicaceae. family. Present in tropic, Mainly distributed in, and subtropics., tropics., , Cruciferae, , Root with underground Taproot, fusiform and, bulb, corm and, napiform., rhizomes., , Perennial herb., , Commonly called as, lily family. It is a, representative of, monocots., , Liliaceae, , Herbaceous, rarely, Stem may be, woody, hairy, hollow, underground partially., underground (potato)., , Taproot system., , Herb, shrub and, small trees., , Commonly known as, potato family. It is, distributed in tropics, and subtropics., , Solanaceae, , Description of Some Important Families, , 102, Handbook of Biology, , Telegram @neetquestionpaper
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Telegram @neetquestionpaper, , 6, Anatomy of, Flowering Plants, Anatomy (Gk. ana − up; tome − cutting) is the study of internal, structures of an organism. There is a large variety of plants having, diverse structures both morphologically and anatomically., Cell is the basic unit of organisation of all organisms and these are, organised into tissues and above level of structure. The plant body is, made up of various categories of tissues to comply the division of, labour., , The Tissues, A group of cells having a common origin and cooperating with one, another to perform a similar function is described as a tissue. The term, ‘tissue’ was coined by N Grew., The cells constituting a tissue are connected together by, plasmodesmata for proper coordination among them. The study of, tissues is called histology. On the basis of constitution of cells, the, tissues are of two types, i.e., simple and complex. A simple tissue is, made up of similar cells, which carry out the same function, whereas, the complex tissue is made up of two or more than two types of cells, which carry out the similar functions. Tissues can be conveniently, grouped into two categories, 1. Meristematic tissues, , 2. Permanent tissues, , Given flow chart shows the outlines of various tissues and their, components in plants., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 105, Anatomy of Flowering Plants, Tissues, , Permanent Tissue, , Meristematic Tissue, , Based on origin Based on, and Development Position in, Plant Body, Promeristem, (Pri-mordial, or, Embryonic, Meristem), , Apical, Meristem, , Primary Meristem, , Lateral, Meristem, , Based on Function, , Intercalary, Meristem, , Secondary Meristem, , Simple Tissue, Protoderm, , Parenchyma, , Ground, Meristem, Procambium, , Collenchyma, , Complex Tissue, Xylem (wood), , Sclerenchymatous fibres, , Stone Cells, , Glandular, Tissue, , Pholem (bast), , Tracheids, Vessels, (tracheae), Xylem Fibres, (xylem, sclerenchyma), Xylem, Parenchyma, , Sclerenchyma, , Special Tissue, , Sieve, Elements, Companion, Cells, Phloem Fibres, (phloem, sclerenchyma), Phloem, Parenchyma, , Laticiferous, Tissue, Latex, Cells, , Latex, Vessels, , External Glands Internal Glands, , Glandular, Hairs, , Digestive Glands, (enzyme secreting, glands), , Secreting Glands, (nectaries), , Oil, Gland, , Resin, Gland, , Water Secreting, (hydathodes or, water stomata), , 1. Meristematic Tissues, A meristem or meristematic tissue (Gk. meristos – divided) is a simple, tissue composed of ‘a group of cells that are in continuous state of, division resulting in new cells or retain their power of division’., The term ‘meristem’ was coined by C Nageli (1858) to designate, dividing cells., The chief characteristics of these tissues are, (i) Rounded, oval, polygonal or rectangular immature cells of small, size., (ii) Intercellular spaces are absent between meristematic cells., (iii) They do not store reserve food material and are in active state, of metabolism., (iv) They have abundant and dense cytoplasm with small, endoplasmic reticulum and simple mitochondria., (v) Plastids are present in proplastid stage., (vi) Nucleus is large and conspicuous., , www.aiimsneetshortnotes.com
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106, , Telegram @neetquestionpaper, , Handbook of Biology, , (vii) Vacuoles absent in protoplasm or if present, they are very small, in size., (viii) The cells of cambium are highly vacuolated and they are large in size., (ix) Cell walls are thin, elastic and made up of cellulose., The meristematic tissues can be classified on the basis of origin and, development, functions and the position in plant body., , Classification on the Basis of Origin and Development, Meristem, , Promeristem or, Primordial Meristem, It is also known as urmeristem or, embryonic meristem. It is situated, at the apices of root and shoot., It consists of thin-walled, isodiametric, cells with dense cytoplasm and large, nuclei., , Primary Meristem, , Secondary Meristem, , It is the first derivative of, promeristem and forms, the fundamental parts of, the plant. The cells of, these tissues divide in, all possible planes., , It develops in the later stages, of development and is always, lateral in position., This meristem develops either, at emergency or to affect, secondary growth or the, formation of cork cells., , Classification on the Basis of Function, Meristem, , Protoderm, , Procambium, , It is the outermost, meristematic layer of young, growing region. It develops, into epidermis, stomata, and root hairs., , It is composed of narrow, elongated cells. It develops, into primary vascular tissue., , Ground Meristem, It is the precursor of ground, tissue system and has large, and thin-walled cells., These meristems develop into, hypodermis, cortex, pericycle,, pith and medullary rays., , Classification on the Basis of Location in Plant Body, Meristem, , Apical Meristem, These meristems are present, at the apices of primary and, secondary shoots and roots, of the plant. These meristems, are responsible for the, increasing plant length and all, the primary tissues of plant, body, originate from them., , Intercalary Meristem, These meristems lie between, the regions of permanent, tissues. They may be present, either at nodes or at the base, of leaf. These are also known, as detached meristem, as, they originate from the apical, meristem., , Lateral Meristem, These meristems are, present along the side of, the organs. They divide only, in radial direction. These, meristems are responsible, for the increasing girth of, stem and roots., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 107, Anatomy of Flowering Plants, Apical meristem, Intercalary meristem, , Lateral meristem, , (a), , (b), , Position of meristems : (a) Longitudinal view (b) Cross-section, , Various theories have been proposed to explain the organisation of, both root and shoot apical meristems. (RAM and SAM) respectively., The important theories among these are discussed here., Chief Theories related to SAM and RAM, Tunica-Corpus Theory, (Schmidt, 1924), It states that there are two, Shoot Apical Meristem, distinct zones present in, (SAM) Theories, shoot apices–tunica (outer), and corpus (inner)., , Apical Cell Theory, (Hofmeister, 1857), It states that a single apical, cell is the structural and, functional unit of apical, meristems and it regulates, the whole process of, primary growth., , Histogen Theory, (Hanstein, 1870), According to this, there are three distinct meristematic, layers called as dermatogen, periblem and plerome, ., , Quiescent Cell Theory (Frederick, 1953), He observed cytogenerative centre which is the region of, an apical meristem from which all future cells are derived., It is a group of cells, up to 1,000 in number, in the form of hemisphere,, with the flat face toward the root tip., Apical Cell Theory, , Korper-Kappe Theory, (Schuepp, 1917), According to this, the root, apices divide in two planes., First a cell divides transversally, then two daughter cells divide, longitudinally. This sequence, is termed as T-division., , Root Apical Meristem, (RAM) Theories, , (Nageli, 1858), He observed a single, tetrahedral apical cell in the, root apices of a number of, vascular cryptogams like, algae, bryophytes, etc., , Histogen Theory, (Hanstein, 1870), It is similar to histogen theory of SAM., Each of the following three layers has a specific purpose, (a) Dermatogen—Epidermis, (b) Periblem—Cortex, (c) Plerome—Vascular cylinder, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 108, , Handbook of Biology, , Note, Haberlandt (1914) proposed the name protoderm, ground meristem and, procambium respectively to histogens., , 2. Permanent Tissues, These tissues are formed as a result of division and differentiation in, meristematic tissues. These have assumed a definite, shape, size and, function and have temporarily or permanently lost the power of, division. The cells of these tissues are either living or dead, thin-walled, or thick-walled., Permanent tissues are of following three types, (i) Simple tissues, (ii) Complex tissues, (iii) Special tissues, , (i) Simple (Permanent) Tissue, A group of similar permanent cells that perform a common function is, called simple permanent tissue. These are classified as, (a) Parenchyma, (b) Collenchyma, (c) Sclerenchyma, , (a) Parenchyma, It (Gk. para–beside; enchyma–tissue) is the most abundant and, common tissue of plants made up of thin-walled, usually living cells, possessing distinct nucleus. Typically, the cells are isodiametric (all, sides equal)., These may be oval, rounded or polygonal in outline. The cell wall, is made up of cellulose. These cells may or may not have, intercellular spaces. Parenchyma is morphologically or physiologically, unspecialised tissue that forms the ground tissue in various parts of, the plants., Note On the basis of their origin, the intercellular spaces are of two types, l, , l, , Schizogenous formed by the splitting of middle lamella., Lysogenous by the breakdown of cells., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Anatomy of Flowering Plants, 109, Types of Parenchyma, , Parenchyma cells are modified to perform various functions., These functions are mentioned in following figure, Water and food storing parenchyma., Stores starch and protein, etc., Cutinised cells to Epidermal, protect epidermis. parenchyma, , Storage, Parenchyma, Prosenchyma, , Fibre-like elongated,, thick-walled cells,, provides protection., , Chlorenchyma, Non-cutinised Epiblema, cells to protect Parenchyma, the roots., , Parenchyma, Aerenchyma, , Contains chloroplast,, carry out photosynthesis., Cells containing, large air spaces to, float, e.g., in aquatic, plants., , Xylem, Parenchyma, Idioblasts, Phloem, Often thickened cells, Large and non-green cells,, parenchyma, to store food and lateral, contain tannins and oils, etc., conduction of water., Elongated parenchyma cells., Helps in storage and translocation of food., , (b) Collenchyma, It (Gk. kolla – glue; en, cheein–to pour in) is a specialised, supporting,, simple permanent tissue. These cells have uneven thickening of, cellulose, pectin and hemicellulose on their walls. Schleiden (1839), discovered and coined the term ‘collenchyma’. These cells are often, elongated, circular, oval or angular in transverse section. Collenchyma, is found below the epidermis in the petiole of leaves and stems., Collenchyma provides both mechanical strength and elasticity to the, plants, hence it is also known as living mechanical tissue., Types of Collenchyma, Collenchyma is of three types on the basis of structure of wall, thickenings, Collenchyma, Lamellar Collenchyma, Deposition of heavy thickenings in, tangential than in the radial cell, walls. e.g., stem of Raphanus., , Lacunar Collenchyma, , Angular Collenchyma, , Deposition of thickenings are, primarily around the, intercellular spaces., e.g., aerial root of Manstera., , Deposition of thickenings, takes place at the corners or, angles of the cells. e.g., stem, of Datura., , Lacunate, thickenings, , Lamellar, thickenings, , Air spaces, , Angular, thickenings, , www.aiimsneetshortnotes.com
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110, , Telegram @neetquestionpaper, , Handbook of Biology, , (c) Sclerenchyma, It (Gk. scleros–hard; en, cheein–to pour in) is a considerable, thick-walled, lignified, supportive tissue characterised by the absence, of living protoplast. Mettenius (1805) discovered and coined the, term ‘sclerenchyma’., Thick, secondary, wall, Pointed end, wall, Lumen, Primary, wall, Cross-section, , Long-section, , Structure of sclerenchyma, , Types of Sclerenchyma, , These are as follows, Sclerenchyma fibre These are specialised cells being long,, narrow, thick and lignified with pointed or blunt ends. They have, great tensile strength, elasticity and flexibility., Sclereids The term ‘sclereid’ was given by Tscherch (1885)., These are also known as stone cells or sclerotic cells. They are, dead cells with small lumens., l, , l, , Differences between Parenchyma, Collenchyma, and Sclerenchyma, Collenchyma, , Sclerenchyma, , Cells are living and filled, with protoplasm., , Cells are living and filled, with protoplasm., , Cells are dead and empty., , No wall thickening., , Wall thickenings not, uniform and consists of, cellulose., , Wall thickenings uniform, and consists of cellulose,, lignin or both., , Found in both the outer, and inner parts of plant., , Restricted to the outer, parts of plant., , Found in both the outer, and inner parts, restricted, to the areas, which have, stopped elongation., , Provides mechanical, strength only when they, are fully turgid., , Provides mechanical, strength as well as, elasticity., , Provides only mechanical, strength., , Parenchyma, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Anatomy of Flowering Plants, 111, Parenchyma, , Sclerenchyma, , Collenchyma, , No high refractive index, , High refractive index., , Ability to dedifferentiate, Have ability to, dedifferentiate and produces is almost absent., secondary meristem., , Comparatively low, refractive index., No dedifferentiation at all., , (ii) Complex (Permanent) Tissues, A complex permanent tissue is the collection of different types of cells, that perform or help to perform a common function. These are the, conducting tissues and classified as xylem and phloem., , (a) Xylem (Gk. xylos – wood; Nageli, 1858), It is a complex permanent tissue mainly performing the function of, conduction of water and solutes from the roots up to the top of plants., Simultaneously, it provides strength to the plants., Apical meristem, , Primary xylem, , Procambium, Vascular cambium, , Secondary (wood) xylem, , • Tracheid, • Vessel, • Xylem fibre, • Xylem parenchyma, , Xylem: origin and components, , Components of Xylem, The components of xylem are discussed below, Bordered pits, , Ray cells, , Xylem Parenchyma, These are thin-walled living cells,, store food material and help in, lateral conduction of water. Ray, parenchyma cells help in, conduction of water., Xylem, Components, Xylem Fibres, Also known as xylem, sclerenchyma. They are, long, narrow and tapering, at both the ends. These, provide mechanical support, and have wall pits (simple)., , Tracheids, These are 5-6 mm long dead cells, with wide lumen. The inner walls, have various thickenings to provide, mechanical strength. It constitutes, 90-95% wood in gymnosperms and, 5% wood in angiosperms., , Pitted secondary wall, Tracheae (xylem vessels), These cells perform same, functions as tracheid, but they, are much elongated. These are, formed by the fusion of short wide, and thick-walled vessel elements., , Xylem components, , www.aiimsneetshortnotes.com, , Rim around, inner side of, vessel (which, is the remains, of the oblique, simple perforation, plate), Pitted secondary, wall
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112, , Telegram @neetquestionpaper, , Handbook of Biology, , Types of Xylem, l, , On the basis of the time of origin, Xylem, , Protoxylem, , Metaxylem, , It develops first from, procambial strands,, consists of smaller, tracheids and vessels., , l, , It develops in later, stage. It consists of, large tracheids and, vessels., , On the basis of position of protoxylem with respect to metaxylem, Xylem, , Exarch, , Mesarch, , Centrarch, , Endarch, , Protoxylem, , Protoxylem, , Metaxylem, , Metaxylem, , Protoxylem lying, outside the, metaxylem., , Protoxylem in, middle of, metaxylem., , Protoxylem in, centre of, metaxylem., , Protoxylem lies, inside the, metaxylem., , (b) Phloem (Gk. phlois – inner bark ; Nageli, 1858), It is a complex permanent tissue which principally transports organic, food in plants. It is also known as bast, because fibres of some plants, are used for binding purpose., It consists of four components. A new cell type called transfer cells, has recently been reported from phloem. Transfer cells are much folded, cells adjacent to sieve cells. They provide large area for the transfer of, solutes., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 113, Anatomy of Flowering Plants, Sieve Tube, These are formed by the, fusion of sieve cells, (syncytes). Nucleus is, present in young cells, but, disappear in mature one., , Phloem Parenchyma, These are living tissues, present in most dicot and, pteridophytes., It is absent in monocots., These cells help in storage of, food and collection of organic, substances like tannins,, resins, etc., , Companion Cell, Thin walled elongated cells., Only present in angiosperms., These are living and possess, cytoplasmic content with, conspicuous nucleus., , Phloem Fibres/Bast Fibre, These are sclerenchymatous, elongated cells. They have lignified, walls and simple pits., These may be living or non-living, at maturity., Sieve Plate, They possess sieve pores which are, involved in the movement of food., , Components of phloem, , Protophloem and Metaphloem, Protophloem is first formed part, which develops in parts that, are undergoing enlargement. During elongation the protophloem, elements get stretched and become non-functional., Metaphloem is formed in the organs when they stop enlargement., l, , l, , (iii) Special Tissues (Secretory Tissues), These cells or tissues are specialised to secrete or excrete products. The, secreted substances may be useful for plants or may not be useful., These tissues are of two types, , (a) Glandular Tissues, These are present in form of glands (a gland is a group of specialised, cells, which have capacity to secrete or excrete products)., The glandular tissues are of two types, External glands, Internal glands, l, , l, , www.aiimsneetshortnotes.com
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114, , Telegram @neetquestionpaper, , Handbook of Biology, , External Glands, , Glandular Hairs, , Digestive Glands, , These are present in, epidermis. They may be, unicellular or multicellular., These may be, stinging hair,, oil glands hair., , (enzyme secreting glands), Insectivorous plants, possess such hairs to, digest proteins from the, body of insects., , Secreting Glands, (nectaries), These secrete nectars and, present mostly on flowers., These may be, Floral nectaries–on flower and, extra floral nectaries–on leaves., , Internal Glands, , Oil Secreting, , Resin Secreting, , Water Secreting, , They secrete oil, of aromatic and volatile, nature, e.g., Eucalyptus,, Citrus, Cinnamomum, etc., , Resin and mucilage of, nutritional quality is, secreted from these ducts,, e.g., Pinus, Cycas, etc., , Hydathodes or ‘water, stomata’ exude water in, the form of drops, e.g.,, in Colocasia., , (b) Laticiferous Tissues, This tissue is mainly composed of thin-walled elongated, branched and, multinucleate tube-like structures that contain colourless milky or, yellow-coloured fluid called latex., They are scattered throughout the ground tissue of the plant and, contain stored organic matter in the form of starch, rubber, tannins,, alkaloids, mucilage, enzymes, proteins, etc., This tissue is of two types, Latex cells These are uninucleate cells, may be branched or, unbranched. These cells are also known as non-articulated laticifers,, e.g. Euphorbia, Thevetia, etc., Latex vessels These are formed by large number of cells placed, end to end with their transverse wall dissolved so as to form long, vessels, e.g., Papaver, Hevea, etc., l, , l, , Plant Tissue System, The functions of the tissues depend on their location in plant body. The, tissues or a group of tissues which perform a common function,, constitute the tissue system., The principal tissues of a plant can be categorised into three important, tissue systems (Sachs; 1875)., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Anatomy of Flowering Plants, 115, These are as follows, , 1. Epidermal Tissue System (Dermal Tissue System), It is derived from protoderm. It performs several functions like, mechanical support, absorption, excretion, etc., in plants., Following flow chart provides the detail account of these tissues in, plants, Epidermal Tissue System, , Cuticle, It is a continuous layer, of cutin. It is deposited, on outer wall of epidermis., The cuticle is reinforced by, a layer of wax in extremely, dry conditions. In cereals,, it allows the deposition of, silica to protect them from, grazing., , Epidermis, , Epidermal, , Outgrowths, It is the outermost, layer of cells. It is made, up of continuous,closely, arranged living cells.The, root epidermis is referred, to as epiblema or, piliferous layer, because, it has root hairs., , Stomata, Epidermis of all green, aerial parts of plants, contains minute openings, called stomata. It is, surrounded by kidney-shaped, guard cells. Stoma guard cells, and neighbouring subsidiary, cells are collectively termed, as stomatal apparatus., , Emergences, (multicellular outgrowths), e.g., prickles that help in, climbing, protection, etc., Root Hairs, Scales or, Squamiform Hairs They originate from, Disc-like plate and, trichoblasts of epiblema., multicellular in structure., Trichomes, , Hairs, Secretory in, function, , Glandular, , Unicellular, , Non-glandular, , Multicellular, , 2. Ground Tissue System (Fundamental Tissue System), It is partly derived from the periblem and partly from plerome., It constitutes the main bulk of the body. It consists of, simple permanent tissues like parenchyma, collenchyma and, sclerenchyma., , www.aiimsneetshortnotes.com
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116, , Telegram @neetquestionpaper, , Handbook of Biology, , Following flow chart presents the detailed view of ground tissue system, in plants, Ground Tissue System, , Monocotyledons, , Stem, , Dicotyledons, , Root, , Root, , Stem, , 1444444442444444443, , Hypodermis, , Cortex, , It consists of collenchyma, or sclerenchyma cells that lie, below epidermis. It provides, mechanical strength and, rigidity., , It is the main zone lying between the epidermis, and pericycle. In monocots, it is homogenous,, but in dicots, it is differentiated into hypodermis,, general cortex and endodermis., , Pericycle, , Parenchyma, , It is the outermost boundary of vascular strand,, one to several cells in thickness. It may be, parenchymatous or sclerenchymatous., , These are non-vascular areas, which occur between vascular, bundles for lateral conduction., , Medulla or Pith, The parenchymatous, central part of the ground, tissue, which is often parenchymatous. Due to, radial expansion, it becomes hollow as in Cucurbita., , 3. Vascular Tissue System (Fascicular Tissue System), The tissues derived from the procambium are called the vascular or, fascicular tissue system. It consists of number of strands or bundles, called vascular bundles., Vascular Bundles (Components), , Xylem Element, , Cambium, , Phloem Element, , The chief conducting tissues., Consists of tracheids,, vessels, xylem fibre and, xylem parenchyma., , The tissue, concerned with, the conduction of food, materials. It consists of, sieve cells, sieve tubes,, companion cells, phloem, parenchyma and phloem, fibres., , Protophloem, (primarily differentiated), , It is a lateral meristem, that gives rise to secondary, xylem and phloem and, occurs in the form of thin strip., Cambium consists of, two type of cells, 1. Fusiform initials, 2. Ray initials, , Metaphloem, (later differentiated), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Anatomy of Flowering Plants, 117, The vascular bundles are classified into three categories on the basis of, relative positions of xylem and phloem., Vascular Bundles, , Conjoint, , Radial, These are mostly found, in roots. The separate, bands of phloem and, xylem are present., , Concentric, , These are mostly found in stem and, leaves. Both the xylem and phloem are, situated at the same radius, as they are, produced by layer division in, vascular cambium., , Phloem, , In this, either xylem, surrounds the phloem, completely or, phloem surrounds the, xylem completely., , Amphivasal, , Amphicribral, Phloem, , Xylem, , Xylem, , Collateral, Closed, , Bicollateral, Open, , Phloem, Vascular, cambium, Xylem, , Outer phloem, Outer cambium, Xylem, Inner cambium, Inner phloem, , Anatomy of Dicot and Monocot Plants, Various plant organs (i.e., root, stem, leaves, etc.) have characteristic, structures., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 121, Anatomy of Flowering Plants, Secondary Growth in Dicot Root, The secondary growth in dicot roots takes place in both stelar, (by vascular cambium) and in extrastelar region (by cork cambium)., The whole process can be discussed as under, Source, , Apical, meristem, , Primary, Meristems, , Primary, Tissues, , Protoderm, Ground, meristem, Procambium, , Cortex, , Lateral, Meristems, , Secondary, Tissues, , Cork, cambium, , Periderm, (replaces epidermis), , Epidermis, , Pericycle, Vascular, cambium, Primary phloem, Primary xylem, , Secondary phloem, Secondary xylem, , Summary of primary and secondary growth of root in a vascular plant, , Secondary Growth in Dicot Stem, Secondary xylem produced by cambial ring is called wood. The wood, formed in a single year is called annual ring or growth ring. The, whole process of growth can be discussed as under, Source, , Apical, meristem, , Primary, Meristems, , Primary, Tissues, , Protoderm, Ground, meristem, , Procambium, , Lateral, Meristems, , Secondary, Tissues, , Cortex, , Cork, cambium, , Periderm, (replaces epidermis), , Pith, , Vascular, cambium, , Epidermis, , Primary phloem, Primary xylem, , Secondary phloem, Secondary xylem, , Summary of primary and secondary growth in stem of a vascular plant, , Types of Wood, On the basis of time of formation, Wood, , Spring Wood/Early Wood, (xylem vessels with wider, cavities are produced), Sapwood/Alburnum, (consists of living cells,tracheids and, vessels not plugged by tyloses), , Autumn Wood or Late Wood, (xylem vessels with narrow, cavities are produced), Heartwood/Duramen, (living cells absent, tracheids, and vessels plugged by tyloses), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 7, Structural, Organisation in, Animals, In unicellular organisms, all vital cellular functions like digestion,, respiration, excretion, etc., are performed by a single cell. The, multicellular animals have complex body organisation, e.g., Hydra., , Tissue (By Bichat; Father of Histology), It is a group of one or more cell types and their intercellular substances, that perform a particular function., Based on structure, function and location, animal tissues are of, four types, Epithelial Tissue, Origin Ectoderm, mesoderm and endoderm., Function Protection, secretion, reproduction,, absorption and excretion., , Muscular, Tissue, Origin Mesoderm., Function Movement, and locomotion., , Types of, Tissues, , Nervous, Tissue, , Connective, Tissue, Origin Mesoderm., Function Attachment,, support, storage,, transport and protection., , Origin Ectoderm., Function Control and, coordination by nerve impulse., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Structural Organisation in Animals, 123, 1. Epithelial Tissue (By Ruysch), It consists of a sheet of tightly packed cells with the minimum of, intercellular material and rest upon a non-cellular basement, membrane or lamina propria., Common junctions between epithelial cells include tight junctions, gap, junctions, desmosomes, intercellular bridges and interdigitations., These occur at many points of cell to cell and cell to matrix junctions., Epithelial tissues are of two types, , (i) Simple Epithelium, It consists of a single cellular layer and all the cells rest on the, basement membrane. It covers the surface with little wear and tear, activity. It performs secretory, absorptive and protective functions., Squamous, , Simple Epithelia, , • Large flat cells., • Centrally placed flat nuclei., • Help in protection, gas exchange,, excretion, secretion, etc., • Found in blood vessels (endothelium), coelom (mesothelium), etc, Nucleus, , Cytoplasm, , Cuboidal, • Squarish cuboidal cells., • Centrally placed round nuclei., • Helps in protection, secretion,, gamete formation, etc., • Found in ovaries and seminiferous, tubules (germinal epithelium),, salivary ducts, etc., Cytoplasm, Nucleus, Basement membrane, , Basement, membrane, , Pseudostratified, • Unequal columnar cells., • Centrally placed oval nuclei in long, cells and round nuclei in small cells., • Helps in protection, movement of, secretion, etc., , Ciliated, • Cilia bearing cells., • Centrally placed round nuclei., • Helps to maintain CSF,, urine and mucus flow in, one direction., , Ciliated Columnar, , Ciliated Cuboidal, , • Columnar cells., • Cuboidal cells., • Found in Fallopian tube, • Found in certain, brain ventricles, etc., parts of kidneys., , Pseudostratified, Columnar, , Pseudostratified, , Columnar Ciliated, • Cilia bearing cells, • Columnar cells, • Found in olfactory mucosa, • Found in trachea,, large bronchi, etc., male urethra, etc., , Columnar, Columnar, epithelial, cells, Elongated, nuclei, Basement, membrane, , •, •, •, •, , Elongated cells., Elongated nuclei near the base., Helps in protection, secretion, etc., Found in various glands, (glandular epithelium),, stomach, pancreatic lobules, etc., , Types of simple epithelium, , www.aiimsneetshortnotes.com
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124, , Telegram @neetquestionpaper, , Handbook of Biology, , (ii) Compound Epithelium, It consists of multicellular layers and the cells of deepest layer rest on, the basement membrane. It covers the surfaces with maximum wear, and tear activity. It performs protective functions., Compound Epithelium, , Transitional, Epithelium, (urothelium), , Stratified, Epithelium, • Consists of two to many layers of cells., , • Consists of 4-6 layers of cells., Surface layer, Intermediate layer, (polyhedral cells), Basal layer, (columnar or cuboidal cells), , Four types, , Stratified Squamous Stratified Cuboidal, Stratified Columnar Stratified Ciliated, • Outer layer, • Both the outer and, • Outer layers is of, • Outer layer, possesses cuboidal inner layer, squamous cells, consists of ciliated, cells and basal layer comprises columnar, and inner layer is, columnar cells and, comprises, of columnar cells, cells., basal layer is of, columnar cells., which undergoes, columnar cells., • It lines epiglottis,, continuous mitotic • It forms the, mammary gland, • It lines the larynx, epidermis, of, fishes, division, hence,, ducts and parts of, and upper part of, and urodeles. It also urethra., this layer is called, the soft palate., lines sweat gland, germinative layer., ducts and larger, • It forms epidermis, salivary and, of land vertebrates,, pancreatic ducts., lines oral cavity,, vocal cords, etc., , Stratified squamous epithelium is further of two types, (a) Keratinised Stratified Squamous Epithelium Keratin is, present in the dead superficial cells. It is impermeable to water, and forms well protective covering against abrasions. It forms, epidermis of skin of land vertebrates., (b) Non-keratinised Stratified Squamous Epithelium Its, superficial cells are living and keratin is absent. It is permeable, to water and forms moderately protective covering against, abrasions. It lines the buccal cavity, pharynx, oesophagus, etc., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Structural Organisation in Animals, 125, Squamous, layers, , Horny layer, Squamous, layers, Intermediate, layers, Germinative, layer, Basement, membrane, , Intermediate, layers, Germinative, layer, Basement, membrane, , (b), , (a), , (a) Keratinised epithelium (b) Non-keratinised epithelium, , (iii) Glandular Epithelium, Some of the columnar or cuboidal cells get specialised for secretion and, form the glandular epithelium. They are mainly of two types, Unicellular Consisting of isolated glandular cells, e.g., goblet cells, of the alimentary canal., Multicellular Consisting of cluster of cells, e.g., salivary gland., l, , l, , 2. Connective Tissue, Most abundant and widely spread tissue, link and support other, tissues of the body. Basic components of connective tissue are, (i) Cells embedded in the matrix including fibroblast, adipose, cells, macrophages, mesenchyme cells, plasma cells, etc., (ii) Matrix is a mixture of carbohydrates and proteins. The common, mucopolysaccharide in matrix is hyaluronic acid., (iii) Fibres including collagen fibres of white collagen protein,, reticular fibres of reticulin protein and elastic fibres of yellow, elastin protein., Macrophage, , Mast cells, , Collagen, fibres, Fat cell, , Plasma cell, Elastin, fibres, , Amorphous, ground, substance, , Fibroblast, , Smooth, muscle cell, , Endothelial cell, of capillary, , Blood vessel, Capillary, Connective tissue (generalised), , www.aiimsneetshortnotes.com
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www.aiimsneetshortnotes.com, , White (Yellow) Fat, Monolocular, i.e., single, large fat globules, present, less energetic., Brown Fat, Multilocular, i.e., several small, fat globules present, iron, containing cytochrome pigment, is present, more energetic., , Adipose/Fatty Tissue, Contains fat storing adipocytes,, acts as shock-absorber,, produces blood corpuscles,, etc., , Blood, Mobile connective tissue, containing plasma and blood, corpuscles. Platelets are, present., , Lymph, Pale yellow tissue, containing plasma and WBC,, platelets are absent., , Vascular Connective Tissue, Different cells suspended in the liquid, matrix, fibres are absent., , Yellow Elastic, Connective Tissue, Contains loose network, of yellow fibres, elastic, and branched, e.g.,, ligaments., , White Fibrous, Connective Tissue, Collagen is dominant,, tough and inelastic,, e.g., tendon., , Dense Irregular, Dense Regular, , Dense Connective Tissue, Compactly arranged cells and, fibres in matrix., , Loose Connective Tissue, Loosely arranged cells and, fibres in matrix., , Areolar Tissue, Contains small spaces, (areolar) in between the fine, threads. Forms the basic, framework of body., , Pigmented Connective Tissue, Consists of irregular pigment cells, or chromatophores., , Reticular Connective Tissue, Consists of star-shaped, reticular cells., , Connective Tissue Proper, More intercellular material than cells, number of fibres,, intercellular material of structural glycoprotein and, glycoaminoglycans, matrix is soft containing cells and fibres., , Types of Connective Tissue, , Calcified Cartilage, Matrix contains granules of calcium carbonate,, hard, found in vertebral column of shark., , Elastic Cartilage, Matrix contains yellow fibre, found in pinna,, eustachian tube, etc., , White Fibrocartilage, Firm matrix containing white fibres, strongest, cartilage, found in intervertebral discs., , Hyaline Cartilage, Clear, elastic matrix with less fibres, most, prevalent cartilage, found in articular surfaces,, embryonic skeleton, etc., , Cartilage, Soft, avascular tissue containing, chondrocytes, chondrin (matrix), and aggrecan (core protein)., , Bone, Hard, non-pliable tissue containing, osteoblasts, osteocytes and, osteoclasts matrix contain 62% in, organic phase and 38% organic, phase (ossein)., , Skeletal Connective Tissue, Forms endoskeleton, support and protect, the body, rigid matrix enclosing few cells, and fibres., , 126, Handbook of Biology, , Telegram @neetquestionpaper
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Telegram @neetquestionpaper, Structural Organisation in Animals, 127, 3. Muscular Tissue, Contractile tissue containing numerous fine fibrils called myofibrils, in the cytoplasm (sarcoplasm). Muscle cells (myocytes) develop from, myoblasts. Muscles have the capacity to respond to a stimulus, (irritability) by two basic phenomena, i.e., response to a stimulus and, conductivity., Muscular tissues are of following three types, , Sarcolemma, , Striations, Smooth Muscular, • Uninucleate, • Involuntary, • Do not get fatigue, • Slow contraction, • Spindle-shaped and, unstriped, , •, •, •, •, •, , Skeletal Tissue, Multinucleate, Voluntary, Soon get fatigue, Very rapid contraction, Cylindrical and striped, , Dark bands, Light bands, , Nucleus, , Nucleus, Muscular, Tissue, , Striations, Nucleus, Cardiac Muscular, • Uninucleate, • Involuntary, • Never get fatigue, • Rapid contraction, • Cylindrical and striped, , Junction, between, adjacent, cells, , Light bands, Types of muscles, , 4. Neural Tissue, This tissue is the second specialised tissue with the property of, exicitability and conductivity. It consists of nerve cells and glial cells., Neurons are the structural and functional units of neural (nervous), tissue., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Structural Organisation in Animals, 129, Dendrites, (conduct impulse, towards cyton), •, •••, •, ••, • • • ••, •, •, •, •, •, •, •••••• ••••, ••••••••, ••, •• • • • ••••••••, ••• ••• •, •, •• •, ••, ••••, •••• ••, •, ••, • ••• •••••••••, ••, •••, ••, •, •, •, •, •, •• •••, •••, •, •, , Nissl’s Granules, (protein synthesis), , Myelin Sheath, (insulating layer,, carry impulse faster), Axon, (conduct impulse, away from cyton), , Nucleoplasm, Nucleus, , Axon Hillock or Axis cylinder, (part of cyton from where axon arises), , Schwann Cells, (myelin forming cells), , Nodes of Ranvier, (areas where myelin, sheath is interrupted), , Telodendria, (slender, knobbed, terminal of axon), , Structure of a neuron, , Types of Neurons, On the basis of structural nature, neurons are of following four types,, i.e.,, (i) Apolar Neurons, i.e., neurons without polarity. Here, the, fibres of neuron are not differentiated into axon and dendrites., All the fibres are of same nature and can carry information, towards or away from the cell body, e.g., neurons of Hydra., (ii) Unipolar Neurons, i.e., neurons with unidirectional flow, of information. These have one axon or one dendrite only. Most, sensory neurons are unipolar. These are common in, invertebrate and vertebrate embryos., (iii) Bipolar Neurons, i.e., neurons with unidirectional flow of, information, but with one dendron and one axon at opposite, poles. These occur in the retina of eyes, olfactory epithelium, etc., (iv) Multipolar Neurons, i.e., neurons with unidirectional flow of, information, but with one axon and many dendrites. They occur, in the nervous system of adult vertebrates., , www.aiimsneetshortnotes.com
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130, , Telegram @neetquestionpaper, , Handbook of Biology, , Neurons can also be classified according to their functions as, (i) Sensory or Afferent neurons, i.e., these connect sensory or, receptor cells or organs to the CNS and conduct sensory, impulses. Branched or unbranched and naked or encapsulated, free endings of numerous sensory neurons found scattered in, skin epidermis. These serve as cutaneous sense organs or, exteroceptors. Similar endings scattered in skeletal muscles,, bone joints, ligaments and tendons serve as interoceptors., (ii) Motor or Efferent neurons, i.e., these connect the CNS to, effectors (muscles and glands) and conduct motor impulses., (iii) Internuncial or Interneurons These occur only in the CNS, and serve to connect two or more neurons for distant, transmission of impulses., Similarly, nerve fibres can be categorised as, Nerve Fibres, , On the basis of Structure, , Non-medullated, , Medullated, • Covered by myelin, • Carry impulse faster, • Nodes of Ranvier, are present, • White in colour, , • Do not cover by myelin, • Carry impulse slower, • Nodes of Ranvier are, absent, • Grey in colour, , On the basis of Function, , Afferent, • Sensory, • Carries impulse, from sense organ, to CNS, , Efferent, • Motor, • Carries impulse, from CNS to, effector organs, , Earthworm, It is a reddish-brown terrestrial invertebrate that inhabits the upper, layer of the moist soil. The common Indian earthworms are Pheretima, and Lumbricus., , Morphology, Bilaterally symmetrical with elongated, narrow and cylindrical body., It appears brown due to the presence of porphyrin pigment in the body, wall. Dorsal body surface is demarcated by the ventral surface due to, the presence of dark mid-dorsal line. Their body is metamerically, segmented., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 131, Structural Organisation in Animals, Prostomium, Peristomium, , 1, , First segment of the body, (buccal segment)., , 2, , Dorsal fleshy lobe-like process,, overhanging the mouth-like a, hood., , 3, 4, 5 6 97, , Spermathecae, , 8, , Four pairs of ventrolateral,, intersegmental grooves between, segments 5/6, 6/7, 7/8 and 8/9., , 9, 10, , 11, 12, 13, , Setae, An equatorial annular row of, about 80-120 minute, S-shaped,, yellowish, chitinous structure., Found in each segment except, the first, the last and the clitellar, region. These assist in, locomotion., , 14, , Female Genital Pore, Clitellum, , 15, , Girdle-like glandular, thickening of body wall, forms, egg or cocoons in breeding, , 16, , Single, minute, located in, mid-ventral line of 14th segment., , 17, , Genital Papillae, Small, conical ventrolateral, copulatory papillae which, helps in copulation, present in, 17th and 19th segment., , 18, , Male Genital Pore, , 19, , Pair of crescentric apertures located, ventrolaterally upon 18th segment., , 20, , External structure of an earthworm, , Metamerism, It is the repetition of organs and tissues at intervals along the body of, an animal, thus dividing the body into a linear series of similar parts, or segments (metamers). It is an internal mesodermal phenomenon, and helps in more efficient locomotion., , www.aiimsneetshortnotes.com
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132, , Telegram @neetquestionpaper, , Handbook of Biology, , Anatomy and Physiology, , l, , l, , The body wall of the earthworm is covered externally by a thin, non-cellular cuticle below which is epidermis, two muscular layers, and an innermost coelomic epithelium. The epidermis is made up of, a single layer of columnar epithelial cells which contain secretory, gland cells., Locomotion It is brought about by a coordinated contraction and, relaxation of circular and longitudinal muscles of body wall, assisted, by setae, mouth and the hydrostatic pressure of coelomic fluid., Digestive System Earthworm possesses a straight alimentary, canal from mouth to anus. The canal is differentiated into six, regions–buccal chamber, pharynx, oesophagus, gizzard, stomach and, intestine., 1, 2, 3, , Anterior opening of the body, , 4, , Buccal Chamber, , Mouth, Pharynx, , 5, , Thin-walled, small, protrusible, chamber (1st - 3rd segment)., , 6, , Thick-walled, muscular, structure, contains small, unicellular chromophil cells, (4th segment)., , 7, 8, , Oesophagus, 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34, , Long narrow tube, does, not contain any gland, (5th -7th segment)., , {, , Stomach, Tubular structure containing, calciferous glands to neutralise, humic acid of humus., (10th -14th segment)., , Typhlosole, Large, prominent fold hangs, internally into intestinal lumen, from the mid-dorsal line,, increases absorptive surface, area. Between (25th-95th, segment) of intestine., , Gizzard, Thick-walled, hard due to, thick circular muscle layer,, helps in food grinding, (8th - 9th segment)., , {, , l, , Pre-typhlosolar Region, (15th - 26th segment), , Intestinal Caecum, Pair of short and conical, lateral outgrowths on 26th, segment., Lymph gland, , Typhlosolar, part of intestine, Intestinal lumen, , Alimentary canal of an earthworm, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Structural Organisation in Animals, 133, Circulatory System Closed circulatory system, haemoglobin or, erythrocruorin dissolved in blood plasma. Three main blood vessels, in body are dorsal, ventral and sub-neural. Dorsal blood vessel is, the largest blood vessel of the body. Blood glands are present on, the 4th, 5th and 6th segments and they produce blood cells and, haemoglobin. Blood cells are phagocytic in nature. Their heart do, not have any kind of pulsative activity., , l, , Dorsal blood vessel, , Supraoesophageal, vessel, , Valves, , Valves, , (a), , Valves blood, vessel, , (b), , Heart of Pheretima : (a) Lateral heart (7th and 9th segments), (b) Lateral oesophageal heart (12th and 13th segments), , The number, nature and arrangement of blood vessels are very, different in the first 13th segments from that in the rest of the body., Lateral, hearts, , Dorsal vessel, , 1, , 2, , 3 4, , 5, , 7, , 6, , 8, , Supraoesophageal, vessel, , 9 10 11 12, , Lateral oesophageal, hearts, , 13, , 14, , 15, , Dorsointestinal, vessels, , 16, , Commissural, vessel, Ventro-intestinal, vessel, Septo-intestinal, vessel, , Lateral, oesophageal, vessel, , Ventral, vessel, , Anterior, loops, , Ventro-tegumentary vessels, (supply blood to sepia,, body wall, nephridia and, reproductive organs), , Subneural, vessel, (bifurcated), , Pattern of blood vascular system in first 13th segments, , www.aiimsneetshortnotes.com
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134, , Telegram @neetquestionpaper, , Handbook of Biology, Posterior, face of septum, , DorsoCommissural intestinal, vessel, vessels, , Anterior face, of septum, , Dorsal vessel, Supra-intestinal, excretory ducts, , Transverse vessel, Intestine, , Ventro-intestinal, vessel, , Typhlosolar vessel, Septo-intestinal, branch, , Ventral nerve, cord, Septo-nephridial, branch, , Ventral vessel, Subneural vessel, , Integumentary, capillaries, Ventrotegumentary, vessel, , Body-wall, , Pattern of blood vascular system behind 13th segment, Dorsal Vessel, Pharynx, oesophagus, pharyngeal, nephridia, , Dorsointestinal, , Gizzard, , Intestinal, wall, , Lateral oesophageal, Lateral, hearts, 7, 9, , Anterior, loops, Supra, oesophageal, , Lateral, oesophageal, hearts, 12, 13, , Ring, vessels, , Septointestinal, , Subneural, , Septa, genital, organs, anterior, body wall, nephridia, Ventrotegumentary, vessels, , Commissural, vessels, Posterior, body wall, nephridia, Ventrointestinal, , Ventral vessel, , Complete circulation plan of earthworm, l, , l, , Respiratory System The animal is aerobic and gaseous exchange, takes place through general body surface., Excretory System It is made up of segmentally arranged, nephridia of three types., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Structural Organisation in Animals, 135, Mouth, , Buccal Cavity, Ducts of Pharyngeal, Nephridia, , Tufts of Pharyngeal Nephridia, , Pharynx, , Present on either side of pharynx, and oesophagus in, 4th-6th segment, exonephric type., (open to outside at body surface), (III), , Integumentary Nephridia, 200-250 nephridia lying along, the entire inner surface of, body, number increases in, clitellar rigion, appear 7th, segment onwards,, enteronephric type., (I), , Septal Nephridia, Largest nephridia arranged, sidewise the intersegmental, septum, appear from 15th-16th, segment. Enteronephric type, (open into alimentary canal)., (II), , Forest of Integumentary, Nephridia, , Types of nephridia, l, , Nervous System Metamerically segmented, divisible into three, sections, viz., central, peripheral and autonomic. All nerves are, mixed, having both sensory and motor fibres., Peripheral Nervous system, , Autonomous Nervous System, , Includes all nerves that connect, the brain and nerve cord with, various body parts., , Includes the nerve plexuses, located in the gut wall and other, internal organs., , Nervous, System, , Central Nervous System, , Brain Ring, , Nerve Cord, , Oblique ring around pharynx in 3rd, and 4th segments. It has three parts, , Pair of slender cords arises from, the subpharyngeal ganglia,, extends behind upto posterior end, of body. From 5th segment, behind, it has a ganglionic, swelling in the posterior part of, each segment (segmental, ganglion)., , Cerebral or, Suprapharyngeal, Ganglia, Mid-dorsal part,, small paired and, fused structure., , Subpharyngeal, Ganglia, , Mid-ventral part,, small paired and, fused structure., , Circum or, Peripharyngeal, Connectives, Loop-like structure,, connect dorsal and, ventral ganglionic parts., , www.aiimsneetshortnotes.com
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136, l, , Telegram @neetquestionpaper, , Handbook of Biology, , Reproductive System Earthworm is hermaphrodite (bisexual) and, reproduces only sexually., MALE REPRODUCTIVE SYSTEM, , FEMALE REPRODUCTIVE SYSTEM, , Testis, Pair of small, whitish and lobed, 1, structure which hang down in testis 3 2, sac present in 10th and 11th 4, 5, Spermiducal Funnel, 6, Pair of large, ciliated funnel7, like structure, posterior to, 8, each testis sac which lead to, 9, vasa deferentia. Testes Sac, 10, Large, bilobed, thin-walled, structure on the ventral side, 11, of stomach in 10th and 11th, , Spermathecae, Ventro-lateral, large, flaskshaped structure in, Ovary, Small, whitish structure on each, side of nerve cord, consists of, several finger-like processes, Oviducal Funnel, Small, ciliated funnel behind, , 12, , Seminal Vesicle, Two pairs of large, white, structure on sides of stomach, in 11th and 12th segment., Vesicle of 11th segment is, Vasa Deferentia, Long, narrow, internally, ciliated duct which runs up, , 13, , Oviduct, Short, conical, ciliated structure., In 14th segment, both oviducts, , 14, 15, 16, , Female Genital Pore, Opening of oviducts in, , 17, 18, , Segmental Ganglion, , 19, 20, , Prostate Gland, Large, flattened and 21, asymmetrically lobulated, structure spread in the, 17th-20th segment Common male duct, Short and thick duct, which opens out by, , Male Genital Pore, Opening of male, Ventral Nerve Cord, , Accessory Gland, Mass of small, glandular cells, contained in ventrolateral genital, papillae in 17th and 19th, , Reproductive system of earthworm, Copulation, In 2-3 weeks, developing, embryo becomes young, adult worm., , Worm wriggles out completely, through cocoon and left free in, the moist soil., , Sperms reach in, spermatheca, Secretion of clitellum, forms cocoon, Mature ova discharge, into cocoon, , With advancement, it receives, albuminous secretion of, epidermal gland cells., , Worm wriggles backward and, cocoon slips towards the, spermathecal segments, Cocoon receives, numerous eggs in, spermathecal segments., , Events of reproduction in earthworm, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Structural Organisation in Animals, 137, Economic Importance of Earthworm, l, , l, , l, , l, , They are used as bait for fishing., Their burrowing habit increases the fertility of soil. This is called, vermicomposting., Their burrows cause the loss of water by seepage from ditches in, irrigated lands., They are easily obtained and are of convenient size for dissections in, laboratories., , Cockroach, They are brown or black-bodied animals that are included in, class–Insecta of phylum–Arthropoda. The most common species of, cockroaches in India is Periplaneta americana., , Morphology, Nocturnal, bilateral symmetrical invertebrate, distinctly segmented, and covered by a shining brown exoskeleton. Their dorsal body surface, is covered by dark brown wings. When wings are removed, the three, regions of the body–head, thorax and abdomen become visible., Compound eyes, , Head, , Separate visual unit of photoreception,, contains about 2000-2500 units, called ommatidium (ectodermal origin),, outer surface is convex and consists, of hexagonal areas called facets., , Small, triangular, perpendicular to, body axis (hypognathous conditon),, contains 6 embryonic segments., , Antenna, , Forewings or tegmen, , Thread-like, tactile, olfactory and, thermal receptor. Formed of small, segment-podomeres. Scape is basal, and pedicle is second podomere., , Narrow, thick, hard and, leathery. Also called wing, covers/elytra /tegmina,, used for protection., , 1, 2, 3, 4, 5, 7 6, 7, , Broad, thin, soft and, membranous. Remain folded, during rest under forewings., Useful for flying., , Spiracle, Ten pairs of small,, slit-like respiratory apertures,, occur dorsoventrally upon the, body surface., , Anal cercus, Pair of sensory, 15 segmented, structure which probably, represents the 11th embryonic, segment. It bears several, minute hairs sensitive to, sound and other vibrations., , 9, , Prothorax, Mesothorax, Metathorax, , 123, , Thorax, Hindwings, , Abdomen, , Its 3 segments are, covered by thick, and large tergites, or nota. Prothorax, possesses largest terga., , Contains 10 segments, possesses, (thin sclerities. 5th and 6th tergites are, joined by arthrodial membrane, which possess glands., Coxa, , Anal style, Unjointed, thread-like, structure present on the, 9th sternum of male, and absent in female., , Femur, , Tibia, , (a), (b), , Trochanter, Tarsus (5 segmented), Plantulae (adhesive pad), Pulvillus or arolium, Claws, , External features of cockroach : (a) Complete body (b) One walking leg, , www.aiimsneetshortnotes.com
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138, l, , Telegram @neetquestionpaper, , Handbook of Biology, , Sclerites Small plate-like structures, which forms the exoskeleton., These structures are joined together by soft, intersegmental, flexible, membrane called arthrodial membrane., The dorsal sclerites are called tergites, ventral one are sternites,, while the lateral ones are called pleurites., , Anatomy and Physiology, l, , l, , l, , l, , l, , Body Wall The body wall contains cuticle, epidermis and basement, membrane., Body Cavity Cockroaches are coelomate animals. But, true coelom, occurs only in embryonic stage. In adults, it is found in small, cavities only around the gonads., Endoskeleton Certain processes of exoskeleton extend into the, body and form endoskeletal elements. These provide attachment to, the muscles and hence called apodemes., Locomotion Cockroaches are good runners, but poor fliers as the, muscles associated with the jointed legs are much more developed, than those associated with the wings., Digestive System The mouth in animal is surrounded by, well-defined appendages, which can be seen as, Sensory setae, , Muscles, Denticles, , Condyl, , Epipharynx, Prostheca, Labrum, Mandible, , Mandible, , Salivary, duct, Hypopharynx, , Maxillary palp, , Ligulae, , Labial palp, , Glossa, , Lacinia, , Galea, Palpifer, , Paraglossa, Stipes, , Prementum, Palpiger, , Cardo, First maxilla, , Submentum, , Mentum, Ligulae, , First maxilla, , Labium, Mouth parts of cockroach, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Structural Organisation in Animals, 139, Alimentary canal is complete and well-differentiated in accordance, with omnivorous mode of feeding. It is divisible into following parts, Mouth, Opening of digestive, system containing, biting mouth parts., Foregut, About onethird anterior, most part of, alimentary, canal., Internally lined, by cuticle and, ectodermal, epithelium, because it is, derived from, embryonic, stomodaeum., , Pharynx, Contains dilatory, muscles which, contract and, expand tentorium, and sclerites of, head capsule, Oesophagus, Long and narrow, tube which aids in, passage of food,, its wall is folded, internally., Crop, Flexible and thinwalled due to the, presence of, muscles and, several internal, folds. It helps in, food digestion., , Gizzard, Thick-walled and hard, due to the presence of, thick circular muscles., Helps in food grinding., Its anterior part called, armarium contains, six large chitinous teeth., , Brain, , Salivary Glands, Large, whitish structure on each side., Each gland includes a flattened, glandular part and a long, sac-like, receptacle. Their secretion helps to, throughly mix and lubricate the, chewed food particles. Its enzymes, amylase, chitinase and zymase help, in food digestion., Hepatic Caeca, These are 8 small,, tubulalr, finger-like, blind processes. It, helps to absorb the, fully digested, nutrients., Malpighian Tubules, These are about 60150, long, slender,, yellow, blind, tubules., They are mainly, associated with, excretory, function., , Rectum, Small, oval chamber having Colon, internally raised 6 longitudinal Long, thick and coiled part, folds called rectal papillae wall is internally folded., , Midgut, About one, third middle, part. It is a, narrow tube of, uniform, thickness. Its, epithelium, contains, glandular and, absorptive, cells. Its outer, wall, possesses, longitudinal, and circular, muscles. It is, endodermal in, origin., , Ileum, Short, narrow, thin and, internally folded walls, cuticle, bears spines., , Hindgut, Thick and internally lined by cuticle and ectodermal epithelium., Derived from embryonic proctadaeum (ectodermal in origin)., , Digestive system of cockroach, , www.aiimsneetshortnotes.com
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140, l, , Telegram @neetquestionpaper, , Handbook of Biology, , Respiratory System Every tissue of body is in direct, communication with atmospheric air due to the absence of, respiratory pigment in the blood., It consists of following components, (a) Trachea or Air Tubes Numerous, shiny, transparent,, branched tubes formed by extensive invagination of the, hypodermis of skin (ectodermal in origin). There are six, longitudinal tracheal tubes (2 dorsal, 2 ventral and 2 lateral), which are interconnected by transverse commissures., (b) Spiracle or Stigmata Ten pairs of slit-like apertures through, which air enters and escapes from the trachea, located on, lateral side of body, surrounded by a ring-like peritreme., , l, , There are 2 thoracic pairs (larger than abdominal spiracle) and, 8 abdominal pairs (first pair is dorso-lateral upon tergite and, rest seven are upon the pleurites of 2nd - 8th segments)., Circulatory System Cockroach possesses open type of circulatory, system with blood flowing in the blood spaces or lacunae. The blood, is without respiratory pigment and called haemolymph (possesses, plasma and haemocytes). Body consists of three sinuses mainly with, one head sinus., , The flow of blood within the body looks like, , Pericardial sinus, (contains heart), , h, oug, T hr a r t, e, h, Head, Sinus, , Through diaphragm, Perivisceral sinus, Through diaphragm, , Perineural sinus, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Structural Organisation in Animals, 141, Antenna, , Pulsatile Ampulla, Located near the antennal base, which are interconnected by a, large transverse muscle and, associated blood vessels., , Valves, They check the flow of haemolymph, from pericardial sinus to heart, but, not vice-versa, muscles are not seen., , Nerve Cord, Double nerve cord containing a, pairs of segmental ganglia, , Abd 1 Th 3 Th 2, , Heart, 13-chambered, pulsative structure., Flow of blood in it is unidirectional,, i.e., from posterior to anterior end., , Th 1, , Anterior Aorta, Small, narrow, anterior part of dorsal, vessel which extends into the head., , Perineural Sinus, Contains nerve cord, also, called sternal sinus., Perivisceral Sinus, Contains gut or alimentary, canal., , Pericardial Sinus, Contains heart., , Dorsal Diaphragm, Partition between pericardial and, perivisceral sinuses., , Ab, , Muscles, Triangular, fan-like muscles in the, floor of pericardial sinus in each, segment to reinforce dorsal vessel., , 0, d1, , Ostia, They are guarded by valves and allow, the flow of haemolymph from pericardial, sinus to heart, but not vice-versa., , Ventral Diaphragm, Partition between perivisceral and, perineural sinuses., , Circulatory system of cockroach, l, , Excretory System The animal is uricotelic and excretion occurs, through the following structures, Fat Body, It has urate cells, which obtain nitrogenous waste from haemolymph and stores, it in the form of uric acid. Mycetocyte cells of fat body contain symbiotic, bacteria which decompose uric acid into protein during protein deficiency., , Cuticle, Helps in removing excess salt, and nitrogenous wastes, probably at the time when cuticle, is removed during moulting., , Excretory, System, , Malpighian Tubules, Uric acid of haemolymph, +, Potassium + H2O, bicarbonate Gut, , Potassium + H2O, urate, , Mushroom Glands, These are long tubules, i.e., uricose gland in male, cockroach. They store and discharge uric acid, over the spermatophore during copulation., , Potassium+ H O + CO, 2, 2, urate, , Distal, sccretory portion, , Excretory system in cockroach, , www.aiimsneetshortnotes.com, , Potassium + H2O + Uric, acid, bicarbonate, , Proximal, absorptive portion
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142, l, , Telegram @neetquestionpaper, , Handbook of Biology, , Nervous System It is well-developed and divided into following three, types, (i) Central Nervous System It includes a brain, one, suboesophageal or subpharyngeal ganglion and a doublet, ventral nerve cord., (ii) Peripheral Nervous System It includes the nerves that, connect the various ganglia of CNS to different body parts., Optic Nerve, Arises from protocerebrum, supplies, into eyes., Antennary Nerve, Arises from deuterocerebrum,, supplies into antennal., Sub-pharyngeal Ganglion, Formed by the fusion of three, ganglia of head., , Brain or Supraesophageal Ganglion, Bilobed mass, located in head,, represents three fused ganglia, protocerebrum, deuterocerebrum and, tritocerebrum., Circum-pharyngeal Connective, Prothoracic Ganglion, 1st ganglion of thoracic region, from which six pairs of nerves, arise., Mesothoracic Ganglion, Second thoracic ganglion from, which five pairs of nerves arise., , First abdominal Ganglion, A pair of single nerve arises, from first five abdominal, ganglia., , 6th Abdominal Ganglion, Formed by the fusion of several, small ganglia, three pairs of, nerves arise from it., , Metathoracic Ganglion, Last thoracic ganglion from, which five pairs of nerves arise., , Double Nerve Cord, Extends along the mid-ventral, line, contains nine pairs, of segmental ganglia, three in, thorax and six in abdomen., , Central and peripheral nervous system of cockroach, , (iii) Autonomic Nervous System It is of sympathetic type and also, called visceral nervous system. It performs both nervous and, endocrine functions., It is divided into three parts, 1. Caudal NS Includes certain fine nerves that arise from last, abdominal ganglion and innervate hindgut, reproductive organs, and anal appendages., 2. Spiracular NS Includes certain fine paired nerves which arise, from the ganglia of nerve cord and innervate the spiracles., 3. Somatogastric NS Includes certain fine nerves which arise, from five ganglia and innervate the anterior parts of the gut., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Structural Organisation in Animals, 143, l, , Reproductive System Sexes are separate and sexual dimorphism, is also seen, Female Cockroach, , Male Cockroach, , Body relatively larger and thicker., , Body relatively smaller and more flattened., , Abdomen has seven distinct segments., , Abdomen has nine distinct segments., , Hind end of abdomen is blunt and, boat-shaped., , Hind end of abdomen is somewhat, pointed., , Seventh sternite is divided., , Seventh sternite is undivided., , Anal styles are absent., , A pair of anal styles is articulated with 9th, abdominal sternite., , Wings are smaller, extend only up, to the hind end part of body., , Wings are relatively large, extend, somewhat beyond the hind end of body., , FEMALE REPRODUCTIVE SYSTEM, , MALE REPRODUCTIVE SYSTEM, Testes, One pair, dorsolateral, three-lobed, situated from 4th-6th, , Terminal filament, , abdominal segment in fat body, contain numerous, small, white follicles., , Germarium, , Phallic or Conglobate, Gland, , Ovary, , Long, multilobed, flattened accessory, gland., , One pair of, elongated, structure situated, from 2nd to 6th, segment within, the fat bodies,, consists of, 8 ovarioles., , Mushroom Gland, Large, accessory gland in, the junction between, ejaculatory duct and vasa, deferentia., , Vas Deferens, Paired structure, arise from, each testes and run posteriorly, to open into ejaculatory duct, in 8th segment., , Collaterial Gland, Pair of white, highly, branched accessory, gland. Left gland is, larger than the right, gland and their, secretions also differ., , Ejaculatory Duct, Elongated, contractile duct,, internally lined by thin cuticle., , Genital Pouch, Male Genital Pore, Gonapophyses or Phallomeres, , Oviduct, Pedicles of 8 ovarioles join, together to form a small, thick and, muscular oviduct., Spermatheca, Pair of small structure, left, spermatheca is large pyriform, and right one is short, narrow duct., , Vagina, 2 oviducts join in 7th segment to, form a thick vagina., , Three asymmetrical chitinous structures,, represent male external genitia., , Female, Gonopore, Ovipositor Processes, Three pairs of chitinous, processes, hanging from, the roof of oothecal,, chamber represents, female’s external genitalia., , Reproductive system of cockroach, , www.aiimsneetshortnotes.com
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144, l, , l, , l, , l, , l, , l, , Telegram @neetquestionpaper, , Handbook of Biology, , Suspensory Filament Thin, thread-like terminal filament formed, of a syncytial chord of cytoplasm. It is terminally inserted upon, dorsal body wall and serves to suspend the ovarioles into the, perivisceral sinus., Germarium A small, multicellular structure in which oogonia, forms and matures into oocytes., Vitellarium A long and narrow structure which receives the, actively growing oocytes from germarium. It appears beaded due to, gradually growing sizes of contained oocytes., Egg Chamber A small, thick and elliptical structure which, contains, at a time, a single, large, mature ovum., Pedicel A small, hollow structure which unites to form oviduct., Spermatophore It is a three-layered, pear-shaped, tough structure, which centrally contains spermatozoa in the nourishing fluid, secreted by small tubules or utriculi breviores of male’s mushroom, gland., , Physiology of Reproduction, Wings and reproductive, organs appear., , Copulation, , Nymph undergoes, 10-12 moults or ecdyses., , Male discharges sperms in, the spermatheca of the, female., , Ootheca ruptures and small, light coloured, wingless nymphs, hatches out., , Fertilisation occurs in the, genital pouch of female., , Deposited in dark and, dry places., , 16 ova and sperms are, discharged into the genital, pouch., , Form egg case or, Ootheca, , Sperms fertilise ova., , Brownish scleroprotein, , Milk protein, (from left gland), , Secretion from, collaterial glands, , Watery dihydroxyphenol, (from right gland), , Process of reproduction in cockroach, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Structural Organisation in Animals, 145, Economic Importance of Cockroach, l, , l, , They can be used as tools for the research of insect physiology and, toxicology., They do not sting or bite, transport human pathogens., , Frog, They are called amphibians because they can live both on land and in, freshwater. The most common species of frog is Rana tigrina., , Morphology, Frog is a dorsoventrally flattened and streamlined animal, adapted for, an amphibious mode of life. Its body is divisible into head and trunk., Brow Spot, Located mid-dorsally between two eyes,, believed to be the remnant of a functional, pineal eye of remote ancestors of frogs., Tympanic Membrane, Small, deeply pigmented, circular patch of tough, skin, represents the outer, limit of middle ear,, receives sound waves., , Head, Flat and triangular, bears terminal, mouth, cheeks and lips are absent., Nictitating Membrane, Thin and transparent cover that, protects the eyes when animal is in, water or mud., , Forelimb, Short, possesses, four digits, thumb (pollex) is, absent. Helps in directional, orientation during, locomotion and bears the, shock of body weight on, landing after a leap. Claws, or nails are absent., , Hindlimb, Long, bears five digits,, claws and nails are absent., , Cloacal Aperture, Common vent for the discharge of, faeces, urine and reproductive products., , Webbed Feet, All toes of hindlimb are, joined together by a, web of skin fold, adaptation, for leaping and swimming., , External structure of frog, l, , Croaking During the rainy season or breeding season, frogs make, peculiar sound with the help of their vocal cords to attract females, for mating. The male frogs croak louder than the females., , www.aiimsneetshortnotes.com
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146, l, , l, , Telegram @neetquestionpaper, , Handbook of Biology, , Metachrosis It is the capability of frog to change its body colour, with the change in its surroundings and climatic conditions., Nuptial Pad It is a dark swelling on the inner finger of the male, frog which helps the male frog in mating., , Anatomy and Physiology, l, , Digestive System Frogs are holozoic and carnivorous. Their, alimentary canal is short, coiled tube consisting of following, structures, Tongue, Fixed in front and hinder end is free, and bilobed, Which can be thrown, out and retracted backward after, catching the prey, , Gullet, Dorsal large aperture of pharyngeal, cavity which open into oesophagus., , Glottis, A slit like opening which opens, into the laryngotracheal, chamber. Present ventrally in, the pharyngeal cavity., , Oesophagus, It is a short tube due to the, absence of neck. Its wall is, highly distensible due to the, presence of longitudinal, internal folds., , Gall Bladder, Muscular, rounded structure, which receives bile from the, liver, givs rise to cystic duct., , Liver, Largest gland, two lobed,, structure, secretes bile., , Pancreas, Branched, flat gland made up, of lobules and inner core of islet, of Langerhans. Produces, pancreatic juices and cells of, inner core secrete insulin., , Stomach, Thick-walled, divided into, cardiac and pyloric part., , Duodenum, Anterior part of small intestine,, receives common bile duct in its, proximal end. Possess large, number of villi on the inner side of, wall., , Rectum, It is large intestine. Its proximal parts, has more longitudinal folds than the, distal part. It stores faecal matter and, water is absorbed by its wall., , Common Bile Duct, Formed by the union of, bile duct and pancreatic duct,, opens into the duodenum., , Ileum, Posterior part of small intestine,, highly coiled, numerous villi on, internal side., Anus, Aperture at the end of alimentary, canal, guarded by anal sphincter,, faeces expelled out through it., , Digestive system of frog, l, , Respiratory System Respiration in frog occurs through three, modes, (a) Cutaneous Respiration Frog’s skin is ideally adapted for the, process of gaseous exchange. It is without exoskeleton, highly, vascularised skin, always remain moist due to the secretions of, mucous glands. It is most common mode, especially during, hibernation and aestivation., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Structural Organisation in Animals, 147, (b) Buccopharyngeal Respiration Mucosa of buccopharyngeal, cavity is highly vascularised which aids in gaseous exchange., By showing oscillatory movements of the floor of buccal cavity, and keeping the mouth, gullet and glottis closed, breathing, process is carried out. Sternohyal and pterohyal muscles help, in the oscillatory movements. It is carried out in water and, on land., (c) Pulmonary Respiration It involves the lungs, which are, positive pressure type with hollow, highly distensible walls., They are endodermal in origin. Inspiration and expiration, involves gulping movements in between oscillatory motion of, buccopharyngeal respiration., Pulmonary Respiration, , Inspiration, , Expiration, , Contraction of sternohyal muscles, , Contraction of sternohyal muscles, , Lowering of floor of buccal cavity., , Air from lungs rushes to, buccopharyngeal cavity., , Air rushes into buccopharyngeal cavity., Relaxation of submental muscles, opens the external nostrils., Contraction of submental muscles of, lower jaw closes the external nostrils+, Contraction of pterohyal muscles, raises the floor of buccal cavity., , Air leaves the buccopharyngeal, cavity., , Air moves inside the lungs., l, , Circulatory System It consists of blood vascular system of closed, type which represents the incomplete double circulation. i.e., both, oxygenated and deoxygenated blood enters the heart and get mixed, in the ventricle. Blood vascular system comprises blood, heart and, blood vessels. Their heart is myogenic., , www.aiimsneetshortnotes.com
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148, , Telegram @neetquestionpaper, , Handbook of Biology, , Aortic trunks, Near the front end of the atrium, conus, arteriosus splits into right and left aortic trunks., They convey oxygenated blood to the whole body., , Pulmonary Veins, Bring oxygenated blood, from lungs to left atrium., Openings are small and, oblique which prevent, backflow of blood., Left Atrium, Thin-walled, receives, oxygenated blood through, pulmonary veins from the, lungs., , Ventricle, Receives oxygenated and, deoxygenated blood from, auricles through auriculoventricular aperture., Posterior Vena Cava, Large vein that carries, deoxygenated blood, from the lower half of, the body into the right, atrium., , Anterior Vena Cava, Vein with large diameter, carries deoxygenated blood, from the upper half of the, body to the right atrium., Right Atrium, Thin-walled, receives mixed blood, from sinus venous., Coronary Sulcus, Divides atrium and ventricle., Sinus Venosus, Large, triangular, thin-walled, opens, into right atrium, three thick veins, open into it, two precaval veins and, postcaval vein. It is a chamber in, which blood from the various, parts of body collected first., In higher animals (like mammals),, it is incorporated as SA node (pacemaker), within the right auricle. The origin of, pulse is attributed to this structure., , Circulatory system of frog, , (i) Conus or Truncus Arteriosus This accessory chamber is, present towards the ventral side. It contains a spiral valve, inside because of which its cavity is divided into cavum, pulmocutaneum and cavum aorticum., (ii) Pylangium The proximal, more muscular and longer portion, of conus arteriosus. It is also called as bulbus arteriosus. It, contains pulsative cardiac muscles., (iii) Synangium The distal, less muscular portion of conus, arteriosus. It is also called as ventral aorta., (iv) Columnae Carneae These are the major muscle columns of, ventricle. These columns are connected with the flaps of valves, through elastic chords of fibres called chordae tendineae., , l, , Mixed blood is pumped by frog’s heart due to incomplete double, circuit (i.e., due to the presence of only one ventricle)., Lymphatic system It consists of lymphatic capillaries, sinuses,, lymph hearts and lymph., (i) Lymph Mobile connective tissue containing plasma with less, number of proteins and corpuscles, containing numerous, leucocytes, but no erythrocytes., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Structural Organisation in Animals, 149, (ii) Lymph sinuses Thin-walled spaces around the tissues and, between the organs. Subcutaneous and subventral sinuses are, most common., (iii) Lymph hearts Two pairs of thin-walled and muscular structure., (iv) Lymph capillaries They end blindly in contact with the body, cells and tissue spaces. Thin-walled, irregular and permeable to, colloids, water and crystalloids., l, , l, , Excretory System It consists of two kidneys, ureter, urinogenital, ducts and urinary bladder. The kidneys are of mesonephric, type, i.e., it develops from the middle part of intermediate mesoderm., The nephron is not much differentiated. In embryonic conditions,, nephrostomes are functional and in adults, they get replaced by, glomerulus. Frog is ureotelic., Nervous System It comprises CNS, PNS and ANS, (i) Central nervous system It comprises brain and spinal, cord. Brain is enveloped by two membranous meninges, i.e.,, Pia arachnoid (inner, soft, highly vascularised) and Dura mater, (outer, tough, collagen fibre covering)., Cerebral Hemisphere, Small, without fissure, and corpus callosum, convolutions occur in, thinner cortical layer of, gray matter., Pineal Body, Knob-like, glandular, structure. Believed to be, the remnant of third eye., , Olfactory Nerve, Free anterior part of, olfactory lobe, Olfactory Lobe, Relatively small, contains an, oval cavity called rhinocoel., Posterior parts are fused medially., Anterior Choroid Plexus, It is the roof of diencephalon., Provides O2 and nutrients to, CSF., Optic Lobe, One pair, large, possess a, cavity called optocoel which, join together and open into, iter. They are also called, corpora bigemina., , Diencephalon, Small, unpaired part located, between cerebral hemisphere, and midbrain. Its cavity is, third ventricle. Its dorsal wall, is epithalamus and ventral wall, is hypothalamus., Cerebellum, Thin, narrow, solid and, transverse band in hind brain., (pons varolii is absent), , Pineal Stalk, Streak-like outgrowth, along mid-dorsal line, of diencephalon., , Medulla Oblongata, Posterior most and, simplest part of brain stem., It has large 4th ventricle., Its posterior part continues, as spinal cord., Spinal cord, Central canal, , Posterior Choroid Plexus, Dorsal wall of medulla, oblongata along with, pia-arachnoid mater forms this, irregular and highly vascularised, structure. It also provides O2 and, nutrients to CSF., First spinal nerve, , Nervous system of frog, , www.aiimsneetshortnotes.com
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150, , Telegram @neetquestionpaper, , Handbook of Biology, , Exceptions to frog’s brain as compared to humans are, Rhincnceptialon is anterior in position, but not in humans., Optic lobes are one pair, whereas they are two pairs in humans., Corpus striatum is present upon the floor of cavities of cerebral, hemisphere in frog., Hippocampi, corpus callosum and pons Varolii are absent in frogs., Frog’s vision is monolocular and it is binocular in humans., (ii) Peripheral Nervous System It is represented by cranial and, spinal nerves., There are 10 pairs of cranial nerves in frog., Spinal accessory nerves and hypoglossal nerves are absent in it., The number of spinal nerves in frog is 10 pairs, i.e., 20., l, , l, , l, , l, , l, , (iii) Autonomic Nervous System It controls the involuntary, activities such as homeostasis. It comprises two antagonistic parts, (a) Sympathetic NS It generally acts to stimulate the body to, cope with stress. Its nerve endings are cholinergic and, adrenergic., (b) Parasympathetic NS It functions to calm the body. Its, nerve endings are cholinergic., (iv) Endocrine system Endocrine glands secrete hormones for, chemical coordination of various organs of body. The prominent, endocrine glands found in frog are pituitary, thyroid, parathyroid,, thymus, pineal body, pancreatic islets, adrenals and gonads., (v) Skeletal system In frog, exoskeleton is absent. the endoskeleton, has two parts, (a) Axial skeleton includes skull in the head and vertebral, column in trunk., (b) Appendicular skeleton indudes limb bones in the arms and, legs and girdles that connect the limb bones with vertebral, column., (vi) Reproductive System Sexes are separate and sexual dimorphism, can be seen. The vocal sacs and nuptial pad can be observed in, male frogs in breeding season., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 151, Structural Organisation in Animals, Reproductive System, Fat Bodies, Large and yellow structure,, acts as food reserve during, hibernation and aestivation., Testis, Pair of compact, whitish or, yellowish, elongated structure, surrounded by peritoneum,, mesorchium suspends each, testis from ventral to anterior, part of kidney., Contains seminiferous tubules, or ampulla and developing, germ cells., , Oviduct, Long, slender, whitish structure, suspended by dorsal wall by, double-walled peritoneum., Their internal lining, is ciliated and glandular., Ovary, Yellow, flower-like structural,, formed of (7-12) lobes, large, and asymmetrical due to the, presence of developing ova, in large number., , Vasa Efferentia, 10-14 slender ductless, emerges, out from the testes and open into, urniferous tubules or directly into, bidder's canal (convey sperm)., , Urinogenital Duct, These are the common duct, for conveying urine and sperms., Before gut open into cloaca,, they becomes enlarged and, known as seminal vesicle., , Ovisac, Posterior part of oviduct, dilated, and thin-walled opens distally, into cloaca. They are independently, developed Mullerian ducts., Cloacal Aperture, Unified opening of alimentary, canal and reproductive system., , Reproductive system in frog, , Economic Importance of Frog, l, , l, , They control bugs and help keep the ecosystem in balance., They maintain the balance in food chain and food web by acting as, consumers., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 8, , Cell :, The Unit of Life, Cell, It is the basic structural, functional and biological unit of all known, living organisms., Robert Hooke (1665) observed honey-comb-like dead cells in a thin, slice of cork and named them ‘cell’. Anton van Leeuwenhoek (1667), was the first to describe a living cell., The properties of a living organism depend on those of its individual, cells. Cells contain DNA which is found specifically in the chromosome, and RNA found in the cell nucleus and cytoplasm., All cells are basically same in chemical composition in the organisms of, similar species. Energy flow occurs within cells through metabolism, and biochemical reactions., , Cell Theory (Magna Carta of Cell Study), MJ Schleiden; 1838 and Theodor Schwann; 1839., The postulates are, All living beings are made up of cells. Cell is the smallest, independent unit of life., All cells arise from pre-existing cells (Omnis cellula-e-cellula,, Rudolf Virchow)., l, , l, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Cell : The Unit of Life, 153, Shapes and Size of Cell, Cells differ greatly in shape. They may be amoeboid, cuboid,, thread-like, polygonal, disc-like or columnar., Size of biological cell is generally too small to be seen without a, microscope. There are exceptions as well as considerable range in the, sizes of various cell types., Relative size of different cells are given below, , PPLO m), µ, (0 . 5, , Lipids ), nm, (43-5, 0.1nm, , 1µm, , 10nm, , 1nm, , n RBC, Huma µm), -1, (5 0, , 100µm, 10µm, , 100nm, , Proteins, (48-10 nm), , C, n WB, Huma, µm), 0, 3, 5, (2, , Bacteria, (0.7 µm), , egg, Frog, m), (~1 m, , 10mm, 1mm, , Human egg, (0.1 mm), , 100mm, , Chicken, egg (~50mm), , 1m, , Ostrich, egg (~120mm), , Relative size of different cells, , Types of Cells, Cells are classified into two types, i.e., prokaryotic and eukaryotic cells., Prokaryotic cells have incipient nucleus and lack double membrane, bound cellular organelles, whereas eukaryotic cells have true or, advanced nucleus and possess many organelles., 6, Reproduction, , By binary fission, Circular, naked DNA, 2, Cell wall, composed, of murein, , Incipient, nucleus, , 4, , Mainly, unicellular, , True, nucleus, , 1, , Prokaryotic, Cell, 3, , By mitosis and meiosis, , By, Mesosomes, , 7, Respiration, , 5, Few, organelles, , 8, , By, Mitochondria, , Linear DNA in, nucleus with, histones, , 1, 2, Cell wall, Eukaryotic, 3 composed, Cell, of cellulose, 5, 4, Mainly, Many, organelles multicellular, , Protein, By 70 S, By 80 S, Synthesis, ribosomes, ribosomes, Differences between prokaryotic and eukaryotic cell, , www.aiimsneetshortnotes.com
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154, , Telegram @neetquestionpaper, , Handbook of Biology, , Structure and Components of Eukaryotic Cell, (Plant and Animal), Plasmodesmata, Connection between two plant cells,, allows free movement of material., Cell Wall, Non-living rigid layer composed, of cellulose, maintains cell, shape and provide protection., Mitochondria, Double layer bounded granular structure,, outer layer smooth and inner cristae layer possess, ATP synthase particles, semiautonomous., Cytoplasm, Living substance of the cell,, contains vital substances., Ribosomes, Granular structures containing RNA and, proteins. Exists in two forms–70 S, (in prokaryotes) and 80 S (in eukaryotes),, synthesises proteins., Peroxisome, Contains enzymes for peroxide, biosynthesis. Detoxifies various, molecules and helps breakdown of, fatty acids to produce acetyl groups., , Vacuole, Single membrane bound vesicle containing water,, ions and nutrients. It degrades macromolecules, and helps in cell elongation during growth., , Chloroplast, Green coloured plastids containing chlorophyll,, double layered, carry out photosynthesis., , Structure of a plant cell, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Cell : The Unit of Life, 155, Microvilli, Outgrowth of plasma membrane,, increase absorptive surface area., , Plasma Membrane, Quasifluid, elastic cell membranes,, control movement of molecules in and out of, the cell, aids in cell-cell signalling and cell-adhesion., , Golgi Apparatus, Densely stained reticular structures consists of sacs and, cisternae. Process and sort lysosomal, secreted and, membrane proteins to release their content., , Centriole, Present in centrosome as a paired structure, lying, perpendicular to each other., Form basal bodies of cilia and flagella., Nuclear Envelope, Double membrane with perinuclear space., Outer membrane is continuous with RER,, possesses nuclear pores., , Lysosomes, Membrane bound vesicular structures, contain, hydrolytic enzymes, degrade worn-out, material, active at acidic pH., Nucleus, Filled with chromatin, composed of DNA and, proteins synthesises mRNA and tRNA in, dividing cells., Smooth ER, Do not possess ribosomes, major site of lipid synthesis., Nucleolus, Nuclear compartments where most of rRNA is, synthesised., Rough ER, Possess ribosomes on their surface, synthesise,, process and sort secreted and lysosomal proteins., , Structure of an animal cell, , www.aiimsneetshortnotes.com
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156, , Telegram @neetquestionpaper, , Handbook of Biology, , Components of a Cell, Cell Wall, It was first discovered by Robert Hooke (1665). It is a rigid and, non-living structure. It is present just below the glycocalyx (outermost, glycoprotein covering) or murein in all eubacteria and cyanobacteria. It, is absent in animal cell., A typical cell wall consists of four layers namely, (i) Middle lamella Outermost cementing layer between the cells,, made up of Ca and Mg pectates, absent in outer free spaces and, ruptures to create intercellular spaces., (ii) Primary cell wall Thin, elastic, capable of growing cells and, diminishes as the cells mature possesses more hemicellulose, and less cellulose in their cell wall, only cell wall in meristematic, and parenchymatous cells., (iii) Secondary cell wall Formed by accreration, they have more, cellulose, found in collenchyma, sclerenchyma and xylem, vessels; it is rigid and non-elastic, contains pits at intervals., (iv) Tertiary cell wall It is present occasionally, purely cellulosic, and sometimes contains xylem found in the tracheids of, gymnosperms., , Growth of Cell Wall, The growth and formation of cell wall occurs by two ways, (i) By intussusception It is the deposition of wall material in, the form of fine grains., (ii) By apposition In this method, the new cell wall material, secreted by protoplasm is deposited by definite thin plates one, after other., , Functions of the Cell Wall, l, , l, , It maintains the shape of plant cell and protects it from mechanical, injury., It wards off the effect of pathogens., , Plasma Membrane, It contains about 58-59% proteins, 40% lipids and 1-2% carbohydrates., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Cell : The Unit of Life, 157, To explain the structure of plasma membrane, various models were, proposed by different scientists which are discussed below., Sandwich Model, , Unit Membrane Model, , (By Danielli and Davson; 1935), Plasma membrane is made up of three, layers, i.e., a lipid layer of undefined, thickness is sandwiched between two, layers of hydrated globular proteins., Hydrated, protein, Non-polar, tail, , Lipid, bilayer, , Polar, head, , (By Robertson; 1959), The pattern of molecular organisation, remains the same for all membranes., The unit membrane was considered, trilaminar., , Models of, Plasma, Membrane, Structure Hydrophilic, head, , Outer, protein, layer, Lipid, bilayer, , Hydrophobic tail, Inner, protein, layer, , Fluid Mosaic Model, (By Singer and Nicolson; 1972), Bimolecular lipid membrane is interrupted by proteins of different, types (mosaic nature) and these proteins float in the phospholipid, bilayer (fluid nature)., Extrinsic protein, (attached at polar, surface of lipids), , Hydrophilic, head, Lipid bilayer, ( 7 mm thick), Hydrophobic, tail, Tunnel protein, , Intrinsic protein, (membrane spanning), , Models of plasma membrane structure, , Functions of Plasma Membrane, l, , l, , l, , l, , The cell membranes cause compartmentalisation as they, separate the cells from their external environment and organelle, coverings. They also allow the cell organelles to maintain their, identity, internal environment and functional individuality., Plasma membrane protects the cell from injury., The membranes allow the flow of materials and information, between different organelles of the same cell as well as between one, cell and another., As plasmodesmata and gap junctions, the biomembranes provide, organic connections between adjacent cells., , www.aiimsneetshortnotes.com
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158, , Telegram @neetquestionpaper, , Handbook of Biology, , Nucleus, Nucleus or karyon was first discovered by Robert Brown (1831), in the cells of orchids roots. It is darkly stained, spherical and the, largest cell organelle whose composition is as follows : 9-12% DNA,, 15% histones (basic proteins), 15% enzymes, 5% RNA, 3% lipids, 65%, acid and neutral proteins., Nucleus has an outer double layered nuclear membrane with nuclear, pores, a transparent granular matrix (nucleoplasm/karyolymph),, chromatin network composed of DNA and histones and a directly, stainable spherical body called nucleolus., , Chromosomes, They are rod-shaped and thread-like condensed chromatin fibres,, which appear during karyokinesis. Each chromosome has two halves, called chromatids, which are attached to each other by centromere, or primary constriction., Telomere, , Secondary Constriction II, Location is constant for a, particular chromosome, found on, the long arms of 1, 10, 13, 16, and Y-chromosome of humans., Primary Constriction, (centromere), Central constricted region, containing specific DNA sequence, to which a disc of protein called, kinetochore is bounded., Spindle fibres attach to it during, cell division, chromatids are, held together at this point., Secondary Constriction I, (nucleolar organiser), Contains rDNA and present, on chromosome, no. 13, 14, 15, 21, 22, and Y in humans., , Acts as origin of replication,, prevents breakage of DNA ends, and sticking of chromosomal ends, and attaches to nuclear envelope., , Chromonema, Coiled chromatin, containing a, single molecule of DNA duplex., , Nucleolus, Formed by nucleolar organiser during the, reconstruction phase after mitosis., , Satellite, Short part of chromosome,, does not contain thymine in, their nucleic acid., Chromosomes containing satellite, are called SAT chromosomes., , Structural outline of a typical chromosome, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Cell : The Unit of Life, 159, Types of Chromosomes, Chromosomes, Depending upon, the position of, centromere, , Depending upon, the number of, centromere, , Submetacentric, , Metacentric, , Sub-medially, placed centromere., , Medially placed, centromere., , Acrocentric, , Telocentric, , Subterminally, placed centromere, , Terminally placed, centromere, rare., , Monocentric, , Acentric, , Single centromere,, common., , No centromere,, does not take, part in cell division., , Polycentric, , Dicentric, , Many centromeres occur,, diffused along the, entire length., , Two centromeres,, appear as a result, of translocation., , Besides, chromosomes can also be categorised on the basis of their, specific properties. These are, Chromosomes, , Supernumery or, B-chromosomes, Genetically, unnecessary, smaller, than normal, chromosomes. Found, commonly in plants, than animals., Reported in two, species of flatworms, and many species of, angiosperms., , S and E-chromosomes, Somatic or S-type are, found in both germ line, and somatic cell., Eliminative or E-type are, found in germ cells only., Reported in the, family–Cecidomyiidae., , Limited or L-chromosomes, Large and limited to germ, line cell only. Reported in the, family–Sciaridae of, order–Diptera., , Polytene or Salivary, Gland Chromosomes, (Giant chromosomes), Somatic, chromosomes visible, during interphase,, possess darkly stained, bands and lightly, stained interbands., First observed by, Balbiani (1881) in the, salivary gland of, Chironomous., , Minute or, M-chromosomes, Small size, seen during, meiosis, reported in, bryophytes and bugs, of family–Coreidae of, order– Heteroptera., , Lampbrush, Chromosomes, (Giant chromosomes), Elastic chromosomes, seen during extended, diplotene in meiosis-I,, consist of an axis having, a row of dense granules., First observed by, Flemming (1882) in, amphibian oocyte., , Mega chromosomes, Heterochromatic large, chromosomes, may be, mono, di or acentric, not, transmitted through, gametes. Found in few, species of Nicotiana hybrids., , On the basis of genes they possess, the chromosomes can be of, following types, (i) Autosomes These are the somatic chromosomes which do not, take part in fertilisation process. These are also called, allosomes. They are 44 in number in human body., , www.aiimsneetshortnotes.com
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160, , Telegram @neetquestionpaper, , Handbook of Biology, , (ii) Sex chromosomes These are involved in fertilisation process, and helps to pass information from one generation to another., These are also called heterosomes and are two in number in, human body., , Functions of Chromosomes, l, , l, , l, , l, , They carry hereditary information in the genes from parents, to offspring., The SAT (stands for Satellite or Sine Acid Thymonucleonics means, where thymine containing acid is absent) chromosomes form, nucleoli in daughter cells at nucleolar organiser regions., Sex chromosomes (X and Y) play role in sex-determination., They undergo crossing over and mutations and thus, contribute to, the evolution., , Mitochondrion, It is a spherical or rod-shaped, two-layered granular structure. It was, first seen by Kolliker (1850) in the striated muscles and called, sarcosome. Because of the formation of ATP, they are also called as, powerhouses of the cell., Outer Membrane, Smooth and straight, limiting membrane., , Matrix, Contains soluble enzymes of, Krebs’ cycle and one or more, circular DNA molecules,, RNA and ribosomes., , Cristae, Simple or branched tubular, ridges, which are incomplete., Their density indicates the intensity, of respiration., , DNA, It is naked, commonly, circular, makes the, mitochondrion, semiautonomous., , Inner Membrane, Infolded, form number, of plate-like septa, called cristae., , Ribosomes, They resemble prokaryotic, ribosomes,, i.e., 55 S to 70 S type., (a), Crista, , Inner membrane, , F0-F1 particles, Numerous, regularly spaced,, club-shaped elementary particles, (or oxysomes or Racker’s, particles). They function as, ATPase and hence, act as, ATP synthesis site., , (b), , Outer membrane, , Mitochondria (a) Internal structure of a mitochondria (b) One crista magnified, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Cell : The Unit of Life, 161, Each F0 - F1 particle posseses head, a stalk and a base. These are shown, in the figure below, , OSCP, , ADP + Pi, , Cytosolic, medium, , Head, Identified as, coupling factor, 1(F1), contains, 5 subunits,, contains ATPase, inhibitor protein., , H+, , Exoplasmic, medium, Proton half-channel, , c, , c c, , 123, , 321, , Stalk, Contains Oligomysin, Sensitivity Conferring, Protein (OSCP),, necessary for, binding F1 to, inner mitochondrial, membrane., , ATP, , 123, , 100 nm, , c, , H+, Proton bound, to aspartate, , Base, Isolated as F0,, present within, inner mitochondrial, membrane,, provides the proton, channel., , Rotation of, C ring, , Structure of ATP synthase, , Functions of Mitochondria, l, , l, , Synthesise and store ATP during aerobic respiration., Contain many lipid synthesising enzymes., , Plastids, These are the small bodies found free in most plant cells. They are not, found in fungi, some bacteria, algae and multicellular animals. These, double membrane bound structures are semiautonomous organelles, having their own DNA., Based on the type of pigment, they are of three types, (i) Chromoplasts They are yellow or red in colour due to the, presence of carotenoids. They are found in fruits, flower and, leaves., (ii) Leucoplasts They are colourless plastids, which generally, occur near the nucleus in non-green cells. They are further, of three types depending upon the type of food stored,, e.g., amyloplasts (starch), aleuroplasts (proteins) and elaioplasts, (lipids)., , www.aiimsneetshortnotes.com
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162, , Telegram @neetquestionpaper, , Handbook of Biology, , (iii) Chloroplasts These are green coloured plastids containing, chlorophylls and carotenoids. These double membranous, structures contain thylakoids in their stroma. The stroma also, contains enzymes required for the synthesis of carbohydrates, and proteins., , Functions of Plastids, l, , l, , l, , Chromoplast traps electromagnetic radiations., Leucoplast stores food material., Chloroplasts are the centres of photosynthesis., , Endoplasmic Reticulum (ER), These are membrane bound channels, which are seen in the form of a, network of delicate strands and vesicles in the cytoplasm. These were, first observed by Porter, Claude and Fullam (1945)., They are not found in mature erythrocytes and prokaryotes. Two basic, morphological types of ER are Rough Endoplasmic Reticulum (RER), and Smooth Endoplasmic Reticulum (SER)., RER is granular, whereas SER is agranular depending on the basis of, presence or absence of ribosomes on their surface. The ER membranes, may assume the shape of cisternae, tubules or vesicles., , Morphology of the endoplasmic reticulum, , Functions of ER, l, , l, , l, , RER is involved in protein synthesis and secretion., SER is the major site for the synthesis of lipids., The SER membrane shown to possess enzyme system with, detoxification activities., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Cell : The Unit of Life, 163, Golgi Apparatus, These are the flattened stacks of membranes found within the, endomembrane system. This complex cytoplasmic structure is made up, of cisternae, vesicles and vacuoles., They are absent in prokaryotic cells, sieve tubes of plants, sperms of, bryophytes, pteridophytes and RBCs of mammals. Golgi bodies were, first described by Camillo Golgi in 1989. Perroncito (1910) used the, term ‘Dictyosomes’ for smaller dividing units of Golgi apparatus., Mollenhauer and Whaley (1963) suggested the polarised nature of, Golgi complex. According to them, the margins of cisternae are slightly, curved. So, each cisternae has a convex cis (forming face) facing, towards nucleus and a concave trans (maturing face) facing towards, the plasma membrane., cis face, Forming face, facing, towards nucleus, receives, vesicles from nuclear, membrane, and ER., , Cisternae, Stacks of 4-8 membrane, bound saccules, possess, smooth membrane,, frequently curved to provide, polarity to Golgi apparatus., , trans face, Maturing face, facing, towards plasma membrane,, new vesicles are budded, off from this portion., , Transport vesicle, Small sacs, arise from, cisternae by budding, or pinching off., , Structure of Golgi apparatus, , Functions of Golgi Apparatus, l, , l, , l, , Helps in the formation of acrosome of sperms., Important sites for the formation of glycoproteins and glycolipids., Studies by autoradiographic 3 H glucose and 3 H galactose labelling, have provided direct evidence of polysaccharide synthesis in Golgi, apparatus., , Ribosomes, They are large, non-membranous RNA-protein complexes, which are, necessary for protein synthesis. These dense granules are found either, in free state or attached to the outside of cytoplasmic membrane, through ribophorins., , www.aiimsneetshortnotes.com
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164, , Telegram @neetquestionpaper, , Handbook of Biology, , These are also called Palade particles as they were first observed by, George Palade in 1955. In plants, they were reported by Robinson, and Brown in the bean roots., , Types of Ribosomes, Ribosomes are of two basic types, i.e., 70 S and 80 S, where ‘S’ refers to, Svedberg unit of sedimentation coefficient., 21 Proteins, , 33 Proteins, 30 S, , 16 S RNA, 5 S RNA, , 40 S, , 18 S RNA, 5 S RNA, , 60 S, , 50 S, , 23 S RNA, , 5.8 S RNA, , 28 S RNA, , 34 Proteins, , 40 Proteins, (a), , Ribosomes : (a) 70 S (in prokaryotes), , (b), , (b) 80 S (in eukaryotes), , Functions of Ribosomes, l, , l, , They are the sites for polypeptide or protein synthesis (protein, factories)., They provide enzymes (peptidyl transferase) and factors for, condensation of amino acids to form polypeptides., , Lysosomes, They are single membrane bound structures, supposed to contain, hydrolytic enzymes in them. Therefore, they are known as suicidal, bags of the cell. They were first observed by C de Duve (1949) in the, liver cells. They were reported in plant cells by P Matile., There are two basic types of lysosomes namely primary lysosomes, and secondary lysosomes. Primary lysosomes are further, categorised to phagosomes, autophagic vacuoles and residual bodies., Autolysis is the phenomenon of self destruction of a cell with the help, of lysosomes. Because of close relationship between Golgi complex, ER, and lysosomes, Novikoff et al. (1961-64) denoted endomembrane, system as GERL system, i.e., Golgi complex, ER and lysosome system., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Cell : The Unit of Life, 165, Residual bodies, They are secondary lysosomes with indigestible, material. They are important in cell ageing., , Secondary lysosomes, , Primary lysosomes, Formed either directly, from ER or indirectly, from Golgi complex., Contain a definite, enzyme type., , Pinocytosis, Secondary, lysosome, , Phagocytic or pinocytic vacuole, which has the tendency to associate, with primary lysosome., Exocytosis, Autophagosome, , Phagocytosis, Golgi complex, Nucleus, , Outline sketch representing the dynamic aspects of the GERL system., Observe the relationship between the processes of phagocytosis,, pinocytosis, exocytosis and autophagy., , Functions of Lysosomes, l, , l, , l, , They help in intracellular and extracellular digestion., They help in secretion of thyroid hormones and regulation of, hormone secretion in mammotrophs., Acrosome of sperm is considered as a giant lysosome. It contains, hyaluronidase and proteases, which are helpful in dissolving the, covering of ovum. It is formed by the modification of Golgi body., , Vacuoles, About 90% of plant cells is occupied by a single membrane bound, vacuole. They store biomolecules including ions, sugars, amino acids,, proteins and carbohydrates. Tonoplast membrane covers the vacuole., , Functions of Vacuoles, l, , l, , l, , Important contribution to the osmotic properties of the cell., Storage of various substances including waste products., Function as contractile vacuoles, food vacuoles, gas vacuoles, etc., , Centrosome (Centrioles), It was introduced by Boveri in 1888. Centrosomes are present in, animal cells and absent in plant cells. It contains the organelles called, as centrioles., , Functions of Centrioles, These are the structures concerned with spindle formation during, cell division. They are found in pairs, oriented at right angles to each, other., , www.aiimsneetshortnotes.com
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166, , Telegram @neetquestionpaper, , Handbook of Biology, , Microbodies, They are small, single membrane bound cell organelles which absorb, molecular oxygen and take part in oxidation. They were first seen by, Rhodin (1954) in mouse kidney tubule cells., They are of two types, (i) Peroxisomes They contain enzymes for peroxide biosynthesis., They are found in both plant and animal cells in close, association with ER, mitochondria and chloroplasts. Despite, the absence of DNA, they are believed to be able to replicate like, plastids and mitochondria., (ii) Glyoxysomes They contain enzymes for β-oxidation of fatty, acids and glyoxylate pathway. They usually occur in fat rich, plant cells. They are more prominent in plant seedlings and, generally found in yeast and Neurospora cells. They are, considered to be special peroxisomes. They were first reported, by Beevers in 1969 in the endosperm of germinating seeds., , Functions of Microbodies, l, , l, , l, , Peroxisomes can metabolise unusual substances or xenobiotics., Glyoxysomes metabolise acetyl Co-A in glyoxylate cycle to produce, carbohydrates., Peroxisomes are associated with lipid metabolism in animal cells in, particular the oxidation of amino acid and uric acid., , Cytoskeletal Elements, These consist of following types, (i) Microtubules They are unbranched, hollow tubules made up, of tubulin protein. They contain 13 protofilaments and are 25nm, in diameter (Roberts and Franchi). They occur in centrioles,, basal bodies, cilia/flagella, astral rays, spindle fibres, etc. They, are non-contractile in nature., (ii) Microfilaments They are long, narrow, cylindrical rods made, up of actin protein. They are contractile, solid structures having, diameter of about 7nm. They occur below cell membrane and at, the interphase of plasmagel-plasmasol., , Functions of Cytoskeletal Elements, l, , l, , Microtubules help in the movement of nuclei during division., Microfilaments are responsible for cellular movements like, contraction, crawling, pinching during division and formation of, cellular extensions., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 9, , Biomolecules, Chemistry is the foundation of biology. A number of chemicals (over, 5000) are found in cells with a great quantitative and qualitative, variations. These chemicals and their interactions are responsible for, the formation of all the biological molecules or compounds which, primarily have carbon as one of its constituents. These biological, molecules can be collectively termed as biomolecules., A quantitative (in percentage) account of four main organic compounds, present in protoplasm of animal and plant cell is shown in figure (pie, diagram) below., Proteins 15%, , Water 75%, , Fats and other 1%, Proteins 2%, Mineral solids 2%, , Fats 13%, , Water 67%, , Mineral solids 4%, , Carbohydrates 20%, (a), , Carbohydrates, and other 10%, (b), , Chemical constituents of the protoplasm : (a) Plants (b) Animals, , Before discussing the biomolecules in detail, we need to take a look on, the methods of chemical analysis to determine the composition of any, cell or tissue in living state., , How to Analyse Chemical Composition?, We generally perform the chemical analysis to get an idea about the, molecular formula and probable structure of a compound., There are two general methods of analysis, (i) The living matter grinded in trichloroacetic acid and, then filtered result in two fractions–filtrate/acid soluble, fraction (micromolecules) and pellet/acid insoluble fraction, (macromolecules)., , www.aiimsneetshortnotes.com
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168, , Telegram @neetquestionpaper, , Handbook of Biology, , (ii) All the oxidisable compounds oxidise and inorganic compounds, remain in the form of ash through which composition can also be, confirmed., A comparative account of elements present in living and non-living, matters is given in following table, Composition of Earth’s Crust and Human Body, % Weight of, , Elements, , Earth’s Crust, , Human Body, , Hydrogen (H), , 0.14, , 0.5, , Carbon (C), , 0.03, , 18.5, , Oxygen (O), , 46.6, , 65.0, , Nitrogen (N), , Very little, , 3.3, , Sulphur (S), , 0.03, , 0.3, , Sodium (Na), , 2.8, , 0.2, , Calcium (Ca), , 3.6, , 1.5, , Magnesium (Mg), , 2.1, , 0.1, , Silicon (Si), , 27.7, , Negligible, , Biomolecules, The collection or sum total of different types of biomolecules,, compounds and ions present in a cell is called the cellular pool. A, comprehensive account of various components of cellular pool are given, below, The following flow chart provides a glance view of biomolecules, Biomolecules, Large Molecules, , Small Molecules, , (Biomacromolecules), Include proteins,, nucleic acids, polysaccharides, and lipids., , (Biomicromolecules), ., Primary Metabolites, Directly involved in growth and, reproduction (enzymes and, small peptides), , Secondary Metabolites, Indirectly involved in growth, process (antibiotics, pigments,, alkaloids, etc)., , Bonds Involved in Biomolecules, Despite having several basic bondings between their structure, some, modified bonds and linkages are also involved in the organisation of, biomolecules., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biomolecules, 169, Some of them are briefly discussed here., Name, Peptide bond, , Occurrence / Formed, between, , Diagram / Detail, , Protein / Two amino, acids, , O, —C, , N—, , Peptide H, bond, , Glycosidic bond Carbohydrate / Two, monosaccharides, , CH2OH, O H, , CH2OH, O, , H, , OH, , OH, O, , HO, , OH, , Sugar, , OH, Glycosidic, bond, , Phosphodiester Nucleic acid / Phosphate, and hydroxyl group of, bond, sugar, , OCH2, , Sugar, , OH, , Thymine, , O, , O, O==P—OH Phosphodiester, bond, O, CH2, , Hydrogen bond Nucleic acid / Two, nitrogenous bases, , O, , Guanine, , Hydrogen, bonds, , O, CH2, , O, , Guanine, , Cytosine, , Protein / Two non-polar, side chains of neutral, amino acids, , Disulphide, bonds, , Protein / Two sulphur, containing molecules, , CH2, , O, , O, , O, , Hydrophobic, interaction, , O, , The interaction formed between two molecules, as a strategy to avoid the contact with water., SS, Disulphide, bond, , www.aiimsneetshortnotes.com
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170, , Telegram @neetquestionpaper, , Handbook of Biology, , Carbohydrates (Saccharides), These are among the most widely distributed compounds both in, plants as well as in animal kingdom. These are defined as polyhydroxy, aldoses, ketoses and their condensation products., These organic substances have carbon, hydrogen and oxygen where, oxygen and hydrogen occur in ratio of 1 : 2. The carbohydrate shows, the general formula Cn (H 2O)n or (CH 2O)n ., On the basis of the products of hydrolysis, the carbohydrates are, divided into three major groups, Monosaccharides Such carbohydrates, which on, (Gr. mono-single;, further hydrolysis give compounds, saccharon-sugar) other than carbohydrates., , Carbohydrates, , Oligosaccharides Such carbohydrates, which on further, hydrolysis yield 3 to 9 monosaccharide units., (Gr. oligo – few;, saccharon – sugar)., , Polysaccharides, , Such carbohydrates, which give many, monosaccharide units on hydrolysis, , (Gr. poly – many;, saccharon – sugar)., , 1. Monosaccharides, These are the simplest sugars, which cannot be hydrolysed further., These can be trioses (3C), tetroses (4C), pentoses (5C), hexoses, (6C) and heptoses (7C). On the basis of presence of aldehyde group, (i.e., C H ) and ketone group (i.e., C ), these may be, ||, ||, O, O, aldoses and ketoses, respectively., On reacting with alcoholic and nitrogen group of other organic, compounds, the aldoses and ketoses form a bond called glycosidic, bond (C O C or C N C )., Pentoses and hexoses exist in both open chain as well as ring forms., 6, , H2COH, H, 3, , 4, , HO, , O, , H, OH, , H, , 3, , H, , (a), , 6, , 5, , 2, , OH, , (b), B, , H, , 5, , 1, , OH, , H, , 1, , O, , H2COH, , CH2OH, 2, , H, 4, , 3, , HO, , H, , H, , OH, , (c), C, , Structure of monosaccharides : (a) Open chain glucose (6C), (b) Pyranose ring form (6C) (c) Furanose ring form (5C), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 172, , Handbook of Biology, , (iv) Hexoses (C6H12O6 ), l, , l, , l, , l, , D-glucose This is the most widely distributed sugar in, plants and animals. It is also known as blood sugar. It is a, component of sucrose (another component is fructose)., D-galactose This is found in glycolipids and glycoproteins of, brain and other nervous tissues. It is a component of milk, sugar (lactose)., D-mannose This is widely distributed as mannans in plants., In small amounts, it is also present in some glycoproteins. It, is converted to glucose in animals., D-fructose This is sweetest of all the sugars. It is found in, fruit juices, honey and seminal fluid., , (v) Heptoses (C7H14O7 ) Sedoheptuloses act as intermediates in, Calvin cycle., , 2. Oligosaccharides, These are the compounds, which are formed by condensation of, 2-9 monosaccharide units. These units are joined with the help of, specialised glycosidic linkages., , Reducing and Non-Reducing Sugar, The sugars which have unlinked aldehyde group at their first C-atom, are called as reducing sugars and those which have aldehyde group, in linked condition are called as non-reducing sugars., , HO, 4, , 6, , 6, , CH2OH, , CH2OH, , 5, , H, OH, , H, , 3, , 2, , H, , OH, , H, , 5, , H, , O, , Free —CHO, group at C-1, OH, , O, , H, , O 4, , 1(β), , H, , Galactose, , 1(β), , OH, , H, , 3, , 2, , H, , OH, , H, , Glucose, , Reducing sugar : Lactose (β-1, 4-linkage), —CHO group in, bonding state, , 6, , CH2OH, H, 4, , 5, , O, , H, , 1, HOCH2, , 1(α), , OH, , H, , 3, , 2, , HO, H, , H, , OH, Glucose, , O, , 2 (β), , O, , H, 5, , H, 3, , HO, 4, , CH2OH, 6, , OH, H, Fructose, , Non-reducing sugar : Sucrose (α-1, 2-linkage), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biomolecules, 173, Examples of Oligosaccharides, (i) Lactose or Milk sugar It is present in milk of mammals, and made up of one glucose and one galactose units. It is a, reducing sugar. Souring of milk is due to the conversion of, lactose to lactic acid by the action of Lactic Acid Bacteria (LAB)., (ii) Maltose or Malt sugar It is named because of its occurrence, in malted grain of Barley. Mostly found in germinating seeds, and tissue where starch is broken down. It is a reducing sugar, and formed by condensation of 2 glucose units., (1, 4-glycosidic bond), Glycosidic linkage, Glucose, , Glucose, 6 CH2OH, , 6 CH2OH, , O, , H, 4, , H, OH, 3, , HO, H, , H, , 1, , H, , 4, , 1, , OH, , O, , 2, , H, , O, , H, , H, , H, OH, OH, , H, , OH, , Maltose, , (iii) Sucrose or Table sugar It is also known as cane sugar or, invert sugar. In this, fructose occurs in pentagon form, while, glucose is in hexagon form. It is a non-reducing sugar., Glycosidic linkage, (1, 2-glycosidic bond), 6, , CH2OH, 5, , H, 4, , 6, , O, , H, OH, , HO, 3, , H, , H, 2, , CH2OH, , O, , H, 1 O, , 2, , H, OH, , HOH2C, , 1, , OH, 3, , H, , OH, , 5, , H, 4, , OH, , Sucrose, , (iv) Raffinose (C18H32O16) It is a trisaccharide, contains glucose,, galactose and fructose., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 174, , Handbook of Biology, , 3. Polysaccharides, The term is usually employed to polymers containing minimum ten, monosaccharide units. Polysaccharides are further categorised to, Homo, i.e., these containing similar monosaccharide units and Hetero,, i.e., these containing different saccharide units., Examples of polysaccharides are, (i) Glucans, i.e., which contain only glucose units, e.g., starch,, glycogen, cellulose, chitin, etc., (ii) Galactans, i.e, which contain galactose units only, e.g., agarose,, pectin, galactan., (iii) Mannans, i.e, which contain only mannose units, e.g., yeast, mannan., (iv) Xylans, i.e, which contain xylose units, e.g., hemicellulose, xylan., (v) Fructans, i.e, those with fructose monomers, e.g., inulin., , Starch, Starch (C6H10O5 )n is a polymer of D-glucopyranose units linked by, α -1, 4-glycosidic linkages. It consists of a mixture of amylose (linear,, 200-500 glucose units) and amylopectin (branched, more than, 1000 glucose units) in 1 : 4 ratio, respectively. It is a reserve food, material in plants., The structure of amylose and amylopectin are as follows, 6, , 6, , CH2OH, , CH2OH, , 5, , H, 4, , O, , 6, , CH2OH, O, , H, OH, , 2, , OH, , Glucose, , 5, , H, 4, , 1, , H, , 3, , H, , H, , O, , O, , H, OH, , 4, , O, , 2, , OH, , Glucose, , 5, , H, , 1, , H, , 3, , H, , H, , O, , H, OH, , H, H, , 3, , n, , H, , 2, , OH, , Glucose, , Structure of amylose, , www.aiimsneetshortnotes.com, , H, 1, , O
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Telegram @neetquestionpaper, Biomolecules, 175, 6, , 6, , CH2OH, , CH2OH, , 5, , H, , 5, O, , H, , O, , 5, , H, , H, , 44, , OH, , H, , 1, , 2, , 3, , H, , 1, , OH, , O, , H, 2, , 3, , OH, , H, , O, , H, , H, , C1—C6 α linkage, , O, , OH, , 6, , 6, , CH2OH, 5, , 5, , O, , H, 4, , O, , H, , H, , H, OH, 3, , H, , CH2OH, , CH2, , 4, , H, , 5, , O, , O, , 2, , H, OH, 3, , OH, , H, , H, , H, , 1, , H, , O, , H, , O, , 2, , OH, , OH, 3, , H, , H, O, , H, 2, , OH, , C1—C4, α linkage, , Structures of amylopectin, , Glycogen, About 5,000-15,000 glucose units make up glycogen (C6H10O5 )n . It is, extensively branched and forms the reserve food material in animals, hence, also called as animal starch., , Cellulose, It is a linear polymer of β-D-glucose units connected through, β -1, 4-glycosidic linkage. It is an important structural component of the, cell wall of plants., , Chitin, It is the second most abundant organic substance. It is a complex, polymer of N-acetylglucosamine. It is the structural component of, fungal walls and exoskeletons of arthropods., , Properties of Carbohydrates, Enantiomers, Optical isomers which are mirror images of each other. The d (+) and, l (−) forms of carbohydrates are classified on this basis. The sugar, solution which rotates the axis of plane polarised light clockwise called, d ( + ) isomers, while those rotates it to anticlockwise termed as l ( − ), isomers., , www.aiimsneetshortnotes.com
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176, , Telegram @neetquestionpaper, , Handbook of Biology, , Diastereomers, The isomers which are not the mirror images of each other. These are, of following two types, (i) Epimers The diastereomers which have configurational, change at a single interstitial C-atom., (ii) Anomers These are specialised diastereomers which show, configurational change at terminal carbon called anomeric, carbon (the carbon which is involve in ring formation and, contains functional group). Two anomers of glucose are defined,, i.e., α-form and β-form., , D and L Isomers, These are classified on the basis of direction of —OH group on, farthest chiral carbon from the functional group., O, , H, C, , H—C, , C, OH, , HO—C—H, — OH group at, right side, , O, , H, , HO—C—H, H—C—OH, , H—C—OH, , HO—C—H, , H—C—OH, , HO—C—H, , CH2OH, , D-isomer, , — OH group at, left side, , CH2OH, , L-isomer, , Proteins, The word protein (Gk. proteios – first or foremost) was first coined by, Berzelius (1838) and first used by Mulder (1838). It constitutes about, 15% of our body by mass and involved in various functions like, structural, storage, transport, signalling, movement, etc., These are natural heteropolymer of substances like amino acids., To understand the detailed structure of protein, we first take a close, view of amino acids., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biomolecules, 177, Amino Acids, The compounds which contain both amino (—NH 2 ) and acid, (—COOH ) groups in them., The generalised structure is as follows, R Alkyl / aryl group, , Amino group → H 2N C COOH Carboxylic group, , H, To form peptide (or proteins), amino acids get linked serially by, peptide bonds ( CO NH ) formed between amino group of one, amino acid and the carboxylic group of the adjacent one., , , , , , , , , , , R, R, , , N—C—CO, HN— C—COOH, , , , , , R, R, H, H, , , N—C—COOH, →, N—C—CO, OH, +, , , H, H, H, H, H, H2 O, Amino acid-1, Amino acid-2, H, , H, , H, Peptide, bond, , Following flow chart indicates the physiological nature of amino acids, Amino Acids, Side chain charged at physiological, pH (about 6.0), , Hydrophobic, , All Hydrophilic, , Basic, Lysine, Arginine, Histidine, , Side chain uncharged at pH 6.0, , Acidic, Aspartic acid, Glutamic acid, , Glycine, Serine, Threonine, Asparagine, Glutamine, Cysteine, Methionine, , Hydrophilic, Alanine, Valine, Leucine, Isoleucine, Phenylalanine, Tyrosine, Tryptophan, Proline, , Amino acids and their physiological nature, , There are 20 amino acids, which form proteins. These are called, proteinous amino acids. Amino acids have both three letter and one, letter code for convenient study. Following table gives information, about the chemical nature and codes for amino acids., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biomolecules, 179, Structural Level of Proteins, There are four structural levels in proteins, (i) Primary structure This includes number of polypeptides,, number and sequence of amino acids in each polypeptide., (ii) Secondary structure There are three types of secondary, structures α-helix, β-pleated sheet and collagen helix., The turns of helices and sheets are attached by hydrogen, bonds., (iii) Tertiary structure Tertiary structure is stabilised by several, types of bonds-hydrogen bonds, ionic bonds, van der Waals’, interaction, covalent bonds and hydrophobic bonds. It gives 3-D, conformation to protein., (iv) Quaternary structure Found only in multimeric protein,, where two tertiary structures join as a subunit., , Lipids, They are chemically diverse group of compounds which are, characterised by their relative insolubility in water and solubility in, organic solvents. These are defined as the esters of fatty acids and, alcohol. The lipids have wide distribution in both animal and plant, kingdom., , Classification of Lipids, On the basis of their chemical structure, the lipids are classified into, following classes, Lipids, Simple Lipids, Waxes, , Neutral Fats/, Triglycerides, (Composed of glycerol, and fatty acids, , Derived Lipids, , Compound Lipids, , (have higher melting, point than neutral fats), , Phospholipids, (glycerol have two fatty acids, and one phosphoric acid), , Steroids, , Sterol Glycosides, , (derived from complex, ring structure), , (majorly act, as signal sequence, in protein transport), , Lipoproteins, , Glycolipids, (glycerol is replaced by, amino alcohol sphingosine), , (protein complex, of lipids), , www.aiimsneetshortnotes.com
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180, , Telegram @neetquestionpaper, , Handbook of Biology, , The detailed explanation of these classes of lipids is given below, , Triglycerides (Neutral Fats), Neutral fats such as butter and vegetable oils are mostly triglycerides., Each has three fatty acids linked to a glycerol (glycerine or trihydroxy, propane). In fats, when all three fatty acids are similar, they are called, as pure fats and when these fatty acids are dissimilar, they are, termed as mixed fats., , Waxes, These are long chains of fatty acid linked to long chain of alcohol or, carbon ring. All waxes have firm consistency and repel water., In plants, it covers the surface of leaf and other aerial surfaces to avoid, excess transpiration. In animals, cutaneous glands secrete wax,, lanolin for forming a protective water insoluble coating on animal fur., , Glycolipids, The lipids linked to monosaccharide unit through a glycosidic bond are, called as glycolipids, e.g., glycerolipids, sphingolipids., CH3(CH2)12 HC, , CH—CH— OH, , CH2OH, O, , HO, H, OH, , HC—N— C — R, H, , —O— CH2, , H, H, , H, H, , O, , R = Alkenyl, , OH, , Glycosphingo lipids (Cerebrosides, ceramides), , Phospholipids (Common Membrane Lipids), , 123, , These are triglyceride lipids with one fatty acid replaced by phosphoric, acid which is often linked to additional nitrogenous group like choline,, ethanolamine, etc., , HC —COO, –, O, HC —O—P—O, , 123, , HC —COO, , Non-polar/hydrophobic, hydrocarbon tail, , polar/hydrophilic head, , O, , Phospholipids, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biomolecules, 181, Lipoproteins, These are the complex of lipids and proteins and are present in blood,, milk and egg yolk. On the basis of compactness, these can be divided into, (i) LDL Deposition of bad cholesterol, (ii) HDL Removal of bad cholesterol, , Steroids, The group of complex lipids that possess a rigid backbone of four fused, carbon rings. Sterols are the components of every eukaryotic cell, membrane. The most common type in animal tissue is cholesterol., Chemically these contain cyclopentanoperhydrophenanthrene nucleus., Cyclopentanoperhydrophenanthrene, nucleus, , 3, 4, 4, 4, 2 Hydrophobic part of molecule, , 4, 4, 4, HO123, 1, Hydrophilic part of molecule, , Terms Related to Lipids, (i) Emulsion Due to its insolubility in water, lipids form a, colloidal complex and get dispersed uniformly in water in the, form of minute droplets, called emulsions., (ii) Oils Oils are those fats, which are liquid at room temperature, of 20°C, e.g., groundnut, cotton seed oil, etc., (iii) Hydrogenation The process of conversion of unsaturated, fatty acids to saturated form is called hydrogenation., (iv) Wax-D Tuberculosis and leprosy bacteria produce a wax, called wax-D. It is a major factor for their pathogenicity., (v) Amphipathic The lipids which contain both the hydrophilic, and hydrophobic groups are called amphipathic., , Functions of Lipids, Lipids generally perform following functions, Functions, Energy Storage, , Animals, • Fats (triglycerides), • In adipocytes, , Thermal Insulation, , Buoyancy, , • In plants, the leaf and, Plants, Plants, Animals, • Oils, • As fats in form • Protective covering stem have lipid covering, over leaf and stem; to avoid wetting of plant, other than, • In seeds and, and maintain buoyancy., provides heat, other tissues. triglycerides., protection., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 182, , Handbook of Biology, , Nucleic Acids, These are long chains which are formed by end to end polymerisation, of large number of units called nucleotides. The two most important, nucleic acids, present in living cells are Deoxyribonucleic Acid (DNA), and Ribonucleic Acid (RNA)., , Components of Nucleic Acids, Nucleic Acid, Nitrogenous Base, , Pentose Sugars, , Phosphoric Acid Group, , Deoxyribose, (in DNA), , Ribose, (in RNA), HOH2C, , O, H, , OH, , HOH2C, , H, , H, , O, , OH, , H, , H, , OH, , H, , H, , H, OH, , H, , OH, , Purines, (pyrimidine ring fused, with imidazole ring), , Pyrimidines, (6 membered, aromatic ring), , Adenine, NH2, , Guanine, O, , C, , C, , N, , N, , C, , HC, , C, , N, , HN, , C, , C, , C, , CH, , CH, N, H, , N, , H 2N, , N, H, , N, , O, , Cytosine, NH2, , C, , C, , Thymine, , HN, O, , H3PO4, O–, |, —O— P == O, |, O–, , C, , C, CH, , N, H, (In DNA only), , O, , O, C, , CH, , N, , CH3, , Uracil, , CH, , C, , O, , N, H, , HN, , CH, , C, , CH, , N, H, (In RNA only), , Components of nucleic acid, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 183, Biomolecules, DNA, The DNA molecule is a polymer of several thousands pair of nucleotide, monomers. A nucleotide is formed by the union of a phosphate group, with a nucleoside., Nucleoside = Nitrogenous base + Sugar, Nucleotide = Nucleoside + Phosphate group, DNA forms a double helical structure in which two strands are bonded, through hydrogen bonds and are antiparallel to each other. The coiling, pattern and antiparallel structure of DNA, can be seen as, 2 nm, 5′, , 3′, A T, , 3′ end, 3′, , T A, , 5′, G, C, , G, , G, , 3′, , 3.4 nm, , C, , T, , A, , 5′, , A, G, , 3′ P, 5′, S, , S, , C, , G, , C, , S, , P 3′, 5′, , S, , 5′ 5′, , S, , T, , P 3′, , T A, , 5′, , C, , P, , A T, , 0.34 nm, , T A, , Major, groove, , S, 5′ end, , C, , P, 5′, S, 3′ P, 5′, S, 3′ P, 5′, S, 3′ P, 5′, S, , P 3′, , Minor, groove, G, , 4.7A°, , P 3′, , C, , T A, , S, , 5′ end, , 3.3A°, , 3Å, 11Å, 20Å, , 5′, , 3′, , 3′, , 3′ end, , (b), G, C, , C, , G, , T A, G, , C, , (a), , DNA structure : (a) Coiling of two strands, (b) Antiparallel strands and bond details, , RNA, It is a single-stranded genetic material present in lower organisms., In higher organisms, it is present with DNA and performs various, functions., , www.aiimsneetshortnotes.com
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184, , Telegram @neetquestionpaper, , Handbook of Biology, , The main types of RNAs are, (i) mRNA (messanger RNA), (ii) tRNA (transfer RNA), (iii) rRNA (ribosomal RNA), (iv) hnRNA (heteronuclear RNA), (v) mtRNA (mitochondrial RNA), (vi) cpRNA (chloroplastidal RNA), , Enzymes, An enzyme is a specific protein produced within the organism that is, capable of catalysing specific chemical reactions. As they are of, biological origin and catalyse various reactions, they are also called, biocatalysts., The term ‘Enzyme’ was coined by Kuhne (1878) for catalytically active, substances previously called ferments. Protein nature of the enzyme, was first found out by Sumner (1926). Like catalysts, the enzymes do, not start a chemical reaction or change its equilibrium, but enhance, the rate of reaction., , Chemical Nature of Enzymes, All enzymes are globular proteins with the exception of recently, discovered RNA enzymes. Some enzymes may additionally contain a, non-protein group., There are two types of enzymes on the basis of composition, 1. Simple enzyme The enzyme which completely made up of, protein, e.g., pepsin, trypsin, urease, etc., 2. Conjugate enzyme It is the enzyme formed by two parts, Conjugate Enzyme, , Non-protein Part, , Protein Part, , (cofactor), , (apoenzyme), , Inorganic, , Organic, , (minerals), e.g., calcium, iron, copper,, zinc, etc., , Coenzyme, (easily separable), , Prosthetic Group, (firmly attached), , Enzymes and their constituents, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biomolecules, 185, Classification of Enzymes, On the basis of reaction they performed, enzymes are classified into, six categories, (i) Oxidoreductases Oxidase, reductase and dehydrogenases, are included in this class of enzymes., (ii) Transferases These enzymes perform group transfer reaction., (iii) Hydrolases These enzymes induce hydrolysis, e.g., amylase,, lactase, etc., (iv) Lyases They induce the cleavage without hydrolysis and, addition of double bond takes place, e.g., aldolase., (v) Isomerases Rearrangement of molecular structure,, e.g., isomerase, epimerase, mutase, etc., (vi) Ligases/Synthetases These enzymes induced the bonding of, two molecules after taking energy from ATP., , Nomenclature of Enzymes, Enzymes are named by adding the suffix-ase after the substrate, (e.g., lipase, amylase, maltase, etc.) or chemical reaction (e.g., succinate, dehydrogenase). Some old names also persist as pepsin, trypsin, etc., , Mechanism of Enzyme Action, The general mechanism of enzyme action has two steps, , 1. Formation of Enzyme-Substrate Complex, When an enzyme acts upon a substrate, it forms an enzyme-substrate, complex. Subsquently, this complex decomposes the substrate,, undergoes chemical change and the enzyme is regenerated afterwards., E + S → ES, ES → E + P, Following two models have been put forth to explain the formation of, ES complex, (i) Lock and key model Proposed by Emil Fisher in 1894. He, states that both the components (i.e., enzyme and substrate), have strictly complementary structure., , www.aiimsneetshortnotes.com
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186, , Telegram @neetquestionpaper, , Handbook of Biology, , (ii) Induced fit model Proposed by D Koshland in 1958., According to this, when enzyme binds to substrate, the change, in the shape of active sites of enzyme takes place., , 2. Lowering of Activation Energy, All chemical reactions have a potential energy barrier that must be, overcome before the reactants can be converted into products., The energy required to break this barrier is equivalent to activation, energy., The enzyme lowers the energy of activation during its complexing with, substrate. After the combination of enzyme and substrate, the energy, level of substrate gets raised, and it reacts faster., The diagrammatic representation of the process is as follows, (Z), Transition state, , Activation energy of the, uncatalysed reaction, , E, , Energy of system, , Activation energy in the, Ec presence of an enzyme, X, (initial state), , Overall free energy change,, D G°. This amount of free energy, may be used for work, Product (y), (final state), Progress of reaction, , Graphical representation of enzyme catalysis, , Turnover Number, Being large sized protein molecule, enzyme exists as colloid. Substrate, molecule changed per minute into product is called turn over, number, e.g., 36 millions for carbonic anhydrase, 5 millions for, catalase, etc., , Factors Affecting Enzyme Activity, The activity of an enzyme can be affected by a change in the conditions, which can alter the tertiary structure of the protein., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biomolecules, 187, , Rate of reaction (max rate), , 1. Substrate concentration Enzyme activity increases with, increase in concentration of the substrate to a maximum and, then it levels off., Saturation of active sites, , All active sites, not occupied, Substrate concentration, , Rate of reaction, , 2. Enzyme concentration In general, the rate of reaction will, increase with increasing enzyme concentration, due to, availability of more active sites for reaction., , Enzyme concentration, , 3. Temperature and pH In most of the enzymatic reactions, rise, of 10°C in the temperature doubles the rate of reaction, between 5-40°C. Enzymes are denatured (secondary and above, level of structures degraded) at higher temperature due to, proteinaceous nature and rate of reaction drops., , Rate of reaction, , Enzyme activity, , Optimum temperature, , 10, , 20, , 30, 40 50, Temperature (°C), , pH, , 4. Redox potential Enzymes are sensitive to redox potential of, the cell also. Many enzymes are affected by redox potential due, to the presence of oxidisable SH-group., , www.aiimsneetshortnotes.com
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188, , Telegram @neetquestionpaper, , Handbook of Biology, , Enzyme Inhibition, Reduction or stoppage of enzyme activity due to certain adverse, conditions or chemicals is called enzyme inhibition., Enzyme Inhibition, On the basis of nature of inhibition, , On the basis of cause of inhibition, , Reversible, Inhibition, , Irreversible, Inhibition, , (the effect of inhibitor, is temporary), , (the effect of inhibitor, is permanent), , Competitive, Inhibition, , Non-competitive, Inhibition, , (substance which is similar to, substrate occupies the active, sites and inhibits the activity), , (this is caused by the, alternation of conformation, of the active sites), , Metabolites, Plants and animals produce thousands types of chemicals. Some of the, organic compounds like carbohydrate, fat, protein, nucleic acid,, chlorophyll and heme, etc., are required for basic metabolic processes, and found in the whole plant and animal kingdom. These are called, primary metabolites., Many plants, fungi and microbes synthesise a number of organic, substances, which are not involved in primary metabolism i.e.,, (respiration, reproduction, photosynthesis, protein and lipid, metabolism) and seen to have no direct function in growth and, development of these organisms, called secondary metabolites., These are as follows, Class of Secondary, Metabolites, , Examples, , Chief Functions, , Pigments, , Carotenoids, anthocyanins,, etc., , Attract pollinators and help in, seed dispersal., , Alkaloids, , Morphine, codeine, etc., , Defence against herbivores and, pathogens., , Terpenoides, , Monoterpenes, diterpenes,, etc., , Provide characteristic smell to, plants., , Essential oils, , Lemon grass oil, etc., , Protection against pathogens., , Toxins, , Abrin, ricin, , To kill pathogens., , Drugs, , Vinblastin, curcumin, etc., , Stop the growth of bacteria and, other pathogens., , Polymeric substances, , Rubber, gums and cellulose, , To inhibit the entry of pathogens., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 10, , Cell Cycle and, Cell Division, Cell Cycle, , (Howard and Pelc; 1953), , It is a genetically controlled series of events occurring in a co-ordinated, manner in newly formed cell by which it undergoes growth and divides, to form two daughter cells. The cell cycle is divided into two parts,, i.e., interphase and dividing or M-phase., , Interphase, It is the phase of the cell cycle in which the cell prepares itself for the, initiation of cell division. It comprises G1, S and G2-phase. It represents, the stage between two successive M-phase. The cells are actively, involved in metabolic activities during this phase., Note G0 -Phase (Quiescent stage), It is the quiescent phase during which the cell cycle is arrested for an indefinite, period. Bone, muscle and nerve cells remain in this phase permanently. The, cells remain metabolically active, but do not proliferate., , Dividing or M-phase, It is achieved in two major phases, viz., karyokinesis and cytokinesis., (i) Karyokinesis It involves the division of the nucleus. In, karyokinesis, a nucleus can divide either through mitosis, (equational division) or through meiosis (reductional division),, (a) Mitosis (Flemming, 1882) It is the frequent process of, nuclear division in somatic cells by which two daughter, nuclei are produced, each identical to the parent nuclei. It is, divided into four phases, i.e., prophase, metaphase,, anaphase and telophase., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 191, Cell Cycle and Cell Division, Significance of Mitosis, Growth through repeated, mitosis in organisms., Nucleocytoplasmic, ratio maintenance, in cells., Maintenance of, chromosome number, by replication., , Regeneration of a part or whole body., , Significance, of, Mitosis, , Reproduction in, unicellular organisms., , Maintenance of, surface/volume, ratio., Cancer is caused, due to uncontrolled, mitotic divisions., , Repair and healing, by mitotic division., , (b) Meiosis (Farmer and Moore; 1905) It is a type of indirect, division, which occurs in diploid sex cells and gives rise to four, haploid cells, each having half number of chromosomes as, compared to parent cell., It consists of two divisions, Meiosis-I, Meiosis-II, , l, , l, , Heterotypic, , Reductional, , Meiosis-I, , Homotypic, , Meiosis, , Number of chromosomes get reduced to half, , Meiosis-II, , Equational, , Number of chromosomes remains the same, , Important processes seen during meiosis are, Synapsis (Montgomery; 1901) It is the side-by-side pairing of, homologous chromosomes during the zygotene phase of meiosis, prophase-I., Depending upon the place of origin of pairing, it is procentric, (starting from centromere), proterminal (starting from the ends), and intermediate (starting at various places). Synapsis is assisted, by the formation of a complex known as synaptonemal complex, and the complex formed by pair of homologous chromosomes, (synapsed) is called a bivalent., Crossing over It is a recombinase-mediated process of exchange, of genetic material or chromatid segments between two homologous, chromosomes occurring during the pachytene phase of meiosis-I., The temporary joints or points of attachment between chromosomes, during crossing over are called chiasmata. Formation of these, structures is an indication of completion of crossing over & beginning, l, , l, , l, , l, , www.aiimsneetshortnotes.com
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Nucleolus, , Telophase-I, , Chromosome reaches to, poles and composed of, two chromatids, nucleoli, and nuclear envelope reappear., , Spindle fibres, , www.aiimsneetshortnotes.com, Diakinesis, , Stages of meiosis, , Telophase-II, 4 daughter cells are formed, chromosomes, uncoil, lengtheness and spindle fibres disappear,, centriole replicates, nuclear envelope and, nucleolus re-form., , Anaphase-II, The centromere divides first, and the spindle fibres, pull the chromatids to, opposite poles., , Metaphase-II, Chromosomes line up, separately around the, equator of the spindle., , Prophase-II, , (Prophase-I ends), , Chromosomes become, more condensed,, nucleoli and nuclear, envelope disappear., , Chromatin shorten and thicken,, centriole moves to opposite poles,, nucleoli and nuclear envelope, disperse or degenerate, , Metaphase-I, Bivalents arrange around, the equator., , Anaphase-I, Chromosome number, becomes half, homologous, chromosomes move towards, opposite poles., , Bivalent showing, crossing over in two, places, , Meiosis-I, , Centrioles moving, to opposite poles, , Spindle, formation, , Chromosomes, elongate, proteins, and RNA synthesise,, necessary for bringing, true haploidy., , Interkinesis, , Chiasma forms, chromosomes, begin to separate, terminalisation, of chromosomes occurs., , later stage., , Crossing over occurs in, , (b), , Zygotene, , (a), , syneptonemal complex, begins to appear., , Pair of sister, chromatids, , Synaptonemal, complex, , Synapsis occurs to form bivalents,, , a, , a, , Pair of sister, chromatids, , Leptotene, , A, , B, , c, , Chromosomes shorten, become visible as, slender threads., , A, , Chiasma, , b, B b, , c, , Diplotene, , Nuclear envelope, , Bivalent, , Centromeres, , C C, , Pachytene, , Paternal, chromosomes, (from father), , Pair of homologous, chromosomes = a, bivalent, , }, , (Prophase-I begins), , Maternal, chromosomes, (from mother), , Nuclear, envelope, , 192, Handbook of Biology, , Telegram @neetquestionpaper, , of separation of chomosomes, i. e. , process of terminalisation. In, the process of terminalisation, chiasmata start moving towards their, terminals. The complete process in pictorial view is given below., Meiosis-II
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Telegram @neetquestionpaper, Cell Cycle and Cell Division, 193, Significance of Meiosis, Crossing over to introduce new, combination of traits or variations., Formation of gametes, that are essential for, sexual reproduction., , Assortment of maternal and, paternal chromosomes, independently., , Significance, of, Meiosis, , Maintenance of, chromosome number, by halving the same., , Mutations by irregularities, of meiotic division., , Evidence of basic relationship, of organisms as the details of, meiosis are essentially similar, in majority of organisms., , Differences between Mitosis and Meiosis, Mitosis, , Meiosis, , G2 -period of interphase is normal., , G2 -period is short or non-existent., , Division phase of one or two hours., , Division phase lasts several days to several, years., , Occurs in most body (somatic) cells., , Occurs only in germ cells in the gonads., , Accounts for the growth of body, repair, and regeneration of injured parts and, embryonic development., , Accounts for the formation of gametes in, sexual reproduction., , One chromosomal duplication is followed, by one cell division, producing two diploid, daughter cells., , One chromosomal duplication is followed, by two consecutive divisions, producing, four haploid daughter cells., , Resultant daughter cells are genetically, similar to each other and to the parent, cell., , Resultant daughter cells are genetically, dissimilar to each other and to the parent, cell., , Prophase relatively short and less, complicated., , Prophase of first meiosis very long and, complicated., , No synapsis, chiasmata formation and, crossing over between homologous, chromosomes., , Synapsis, chiasmata formation and crossing, over between homologous chromosomes in, prophase of first meiosis., , It is always the chromatids that segregate, into resultant daughter cells., , It is the homologous chromosomes that, segregate into resultant daughter cells in, first meiosis and chromatids in the second., , Cytokinesis includes a single equatorial, furrow around the parental cell., , Cytokinesis includes two furrows at right, angles around the parent cell., , Occurs in body throughout the life., , Occurs in gonads only when these are, mature for sexual reproduction., , www.aiimsneetshortnotes.com
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194, , Telegram @neetquestionpaper, , Handbook of Biology, , (ii) Cytokinesis It involves the division of cytoplasm. It normally, starts towards the middle anaphase and is completed, simultaneously with the telophase. It is different in animal and, plant cell. In animals, it occurs by cleavage furrow method,, whereas in plants, it is carried out by cell plate method., , Amitosis (Remak; 1855), It is a direct cell division by simple cleavage of nucleus and cytoplasm, without the formation of chromosomes. It is seen in few monerans., Cytoplasm Nucleus, , Dividing nucleus, , Daughter cells, , Cell membrane Constriction, , Stages of amitosis, , Control of Cell Cycle, The checkpoints involved in the cell cycle regulation are as follows, (i) G1-checkpoint at G1/S boundary, (ii) G2 -checkpoint at G 2/M boundary, (iii) Metaphase- checkpoint at metaphase/anaphase boundary, , Significance of Cell Cycle, (i) It helps to maintain, controlled proliferation of cells., (ii) Deregulation of cell cycle may lead to tumour formation., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Transport in Plants 195, , 11, Transport in, Plants, In plants, substances like growth regulators, nutrients, water, food,, etc., have to be transported from one plant part to another., Transport of Substances, Short Distance, , Long Distance, (Xylem and phloem take part), , Transport by, Facilitated Diffusion, Carrier, Protein/, Transporters, , Simple Diffusion, It is a short distance, transport of passive, nature. No energy, In this type of, expenditure takes, transport, carrier, place in this., protein binds to, the substance, and traverses it to, the other side of, membrane., , Active, Transport, , Membrane, , Passive Transport, Transport by, Diffusion, , Channel, Proteins, ATP, , ADP + Pi, , In this transport, the energy is, used to pump, molecule against, concentration, gradient., , Ion Channels, These generally, require more, than one subunit, to form a membrane, passageway. These, span the membrane, with α-helices., , Porins, Aqueous channels, that accelerate, passive diffusion of, small hydrophilic, molecules across, the membrane., , Several methods of transport of substances, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 196, , Handbook of Biology, , Protein Mediated Transport, , Cotransport, (Two molecules, can move together), , Uniport, (The movement of, molecule is, independent, from other molecules), Carrier, protein, A, , Symport, , Antiport, , (Both molecules, cross the membrane, in same direction), , (Both molecules, move in, opposite direction), , Membrane, A, B, , A, Membrane, , B, Membrane, , Types of protein mediated transport, , Processes Involved in Passive Transport, Passive transport of water and solutes in plants may take place via, diffusion, osmosis, plasmolysis, etc., , Diffusion, The tendency of even distribution of solid, liquid or gaseous molecules, in available space is called diffusion. It is driven by random kinetic, motion. Diffusion is defined as the movement of particles of substance, from the region of their higher concentration., Diffusion Pressure (DP) The pressure exerted by the even, distribution of particles, DP ∝ concentration of diffusing particles, , 341, , Temperature, (Rate of diffusion, ∝ Temperature), , Density, 1, Rate of diffusion = —, d, d=relative density, , 143, , Factors Affecting Diffusion, , Diffusion, , 1, Rate of diffusion = —————, Density of, the medium, , www.aiimsneetshortnotes.com, , 143, , 341, , 341, , 1, Rate of diffusion = —————, Difference in, DP at two ends, , Permeability of, Medium, , 143, , Diffusion Pressure, Gradient (DPG)
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Telegram @neetquestionpaper, Transport in Plants 197, Osmosis, It is a special type of diffusion of solution/water that occurs through a, semipermeable membrane., The phenomenon of osmosis was discovered by Nollet in 1748., , Plasmolysis, When the protoplasm shrinks and leaves the cell wall due to, exosmosis, the cell is called plasmolysed and phenomenon is called, plasmolysis., , Imbibition, It is the absorption of water by the solid particles of an adsorbent, causing it to enormously increase in size without forming a solution,, e.g., swelling of dry seeds in water., (i) Solid substance or adsorbent is called imbibant and the liquid, which is imbibed, is known as imbibate., (ii) The swelling imbibant also develops a pressure called, imbibition pressure (matric potential)., , Plant-Water Relation, Maintains the temperature, of plant tissues, It affects transpiration,, seed germination, and respiration,, etc., Oxidises during, photosynthesis, and O2 is, produced, Medium for absorption and, translocation of substances, , Changes the morphology, and anatomy of plants, , Water, in, Plants, , Formation of, protoplasm, , Acts as reactant in, various chemical, reactions, It maintains the, turgidity of plants, , Roles of water in plants, , Components of Plant-Water Relations, 1. Osmotic Pressure (OP; Pfeffer, 1750), The actual pressure, that develops in a solution, when it is separated, from pure water by means of semipermeable membrane., OP depends upon– • Concentration, • Ionisation, • Hydration, • Temperature, , www.aiimsneetshortnotes.com
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198, , Telegram @neetquestionpaper, , Handbook of Biology, , It is measured in terms of atmosphere (atm), 1 atm = 14.7 pounds/inch2, = 760 mmHg, = 1.013 bar, Mpa, = 01013, ., = 1.013 × 105 Pa, Osmotic Pressure OP = m i R T, where, m = Molar concentration, i = Ionisation constant, R = Gas constant, T = Temperature, , 2. Chemical Potential, It is a quantitative expression of the free energy associated with water., ‘It is the difference between the potential of a substance in a given, state and the potential of same substance in standard state.’, , 3. Water Potential (Stalyer and Taylor, 1960), The total kinetic energy of water molecules present in a system is, known as its water potential. Hence, the pure water will have the, highest water potential., ‘It is the difference in the free energy or chemical potential per unit, molal volume of water in a system and that of pure water at the same, temperature and pressure., Chemical potential of pure water at normal temperature and pressure, (NTP) is zero. It is represented by ψ (psi) or more accurately ψw ., Unit of ψw = bars or pascal (1 Mpa = 10 bars), ψw = ψs + ψp + ψg, ↑, , ↑, , ↑, , ↑, , Water Solute, Pressure Potential, potential potential potential due to gravity, , Water potential is a tool which informs us about the plant cells and, tissues. The lower the water potential in a plant cell or tissues, the, greater is its ability to absorb water., , 4. Osmotic Potential (OP)/Solute Potential (ψs ), ‘It is the decrease in chemical potential of pure water due to the, presence of solute particles in it.’, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Transport in Plants 199, It can be calculated by, ψs = C × R × T, where, C = Concentration of solute particles, R = Gas contant, T = Temperature, It always have negative value., , 5. Turgor Pressure (TP)/Hydrostatic, Pressure/Pressure Potential ( ψp ), This can be understood by following schematic diagram, A living, plant cell/tissue, , Placed in hypotonic, solution, , Cell/tissue, becomes turgid, , Water enters, into the cell/tissue, by osmosis, , This pressure presses the, protoplasm against the, cell wall, , Pressure is, developed in cell, sap, , This pressure is called turgor pressure., , 6. Diffusion Pressure Deficit (DPD; Meyer, 1938), The difference between the diffusion pressure of the solution and its, solvent at a particular temperature and atmospheric condition is called, DPD. It determines the direction of net movement of water., DPD has a positive value., DPD ∝ Concentration of solution, It is also known as suction pressure, as it is a measure of the ability, of a cell to absorb water., DPD/SP = OP – WP, WP = TP, DPD = OP – TP, Now-a-days the term ‘Water potential’ is used which is equal to DPD., , Long Distance Transport of Water, Long distance transport of substances within a plant cannot be, accomplished by diffusion alone. Special systems are necessary to move, substances across long distance and at a much faster rate., , www.aiimsneetshortnotes.com
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200, , Telegram @neetquestionpaper, , Handbook of Biology, , Water, minerals and food are generally moved by a mass or bulk flow, system., , Mass Flow System, According to this theory, ‘An increase in transpiration increases the, rate of absorption of ions’. The bulk flow of substances through, vascular system is called translocation., , Absorption of Water by Plants, Water is absorbed along with mineral solutes by the root hairs, purely, by diffusion. Once water is absorbed, it can move through different, pathways., There, (i), (ii), (iii), , are three pathways for the movement of water in plants., Apoplast pathway, Symplast pathway, Transmembrane pathway, , Epidermal cell, Transmembrane, Water travels through, cell by crossing, membranes., , Cortical parenchyma cell, Casparian strip, Endodermis, , Apoplast, Water moves through, the cell wall without, crossing any, membrane., , Symplast, Water travels, from one cell, Root hair to next via, plasmodesmata., , Xylem, vessel, , Pericycle, , Epidermis, , Cortex, , Stele, (vascular cylinder), , Three routes of lateral transport in plant tissues or organ, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Transport in Plants 201, Mechanism of Water Absorption, Water absorption is of two types, Water Absorption, , Active, , Passive, , (root cells play an active role), , (water is transported by, the tension created by, transpiration), , Osmotic absorption, , Non-osmotic absorption, , (in this, the OP of cell, sap of root hair is higher, than that of soil water.), , (this type of absorption is against, the concentration gradient and also, known as active non-osmotic absorption.), , Factors Affecting the Rate of Water Absorption, Concentration, of CO2, , (rate of absorption is, inversely proportional to, the concentration of CO2), , Amount of, Water in Soil, , Water, Absorption, , Concentration, of Soil Solution, , (higher concentration, of soil solution reduces, absorption of water), , (more water leads to, more absorption), , Temperature, , (low temperature inhibits, water absorption), Concentration of O2, , (more O2 concentration, reduces water absorption), , Upward Water Movement in a Plant, For distribution to various parts of the plant, water has to move, upward in a stem against gravity. There are two forces which provide, the energy for this movement of water. These are, , Root Pressure, , Transpiration Pull, , It refers to positive, hydrostatic pressure, that develops in xylem, sap of root which can raise, the water to a certain, height in the xylem., , This can be explained by, cohesion–tension–transpiration, pull model., According to which, the transpiration, from leaves generates a pull for water, to reach to the leaves., , www.aiimsneetshortnotes.com
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202, , Telegram @neetquestionpaper, , Handbook of Biology, , Guttation, It is the loss of water in the liquid state from uninjured parts of plants,, usually from tips and margins of leaves. In this, water exudes from the, group of leaf cells called hydathodes., A hydathode is an opening or pore in the leaf epidermis, around which, are grouped several thin-walled parenchyma cells. It occurs during, night or early morning when there is high atmospheric humidity and, transpiration is less., , Transpiration, It is an evaporative loss of water by plants, which occurs mainly, through stomata. Transpiration reduces the water level in soil, but it is, necessary for water and mineral absorption, i. e. , ascent of sap., Therefore, it is also known as necessary evil., The transpiration driven ascent of xylem sap depends mainly on the, following physical properties of water, Cohesion Mutual attraction between water molecules., Adhesion Attraction of water molecules to polar surfaces (such as, the surface of tracheary elements)., Surface Tension Water molecules are attracted to each other in, the liquid phase more than to water in the gas phase., l, , l, , l, , Types of Transpiration, (i) On the basis of part of the plant in which it takes place, Transpiration, Foliar Transpiration (90%), , Cauline Transpiration (10%), , (transpiration through leaves), , (transpiration through stem), , (ii) On the basis of surface of plant, Transpiration, , Stomatal, , Cuticular, , (85-90%), These are small, pores present on, leaf surface, surrounded, by bean-shaped cells, called guard cells., , (3-8%), Also known as, peristomatal, transpiration., It continues, throughout day, and night., , Bark, , Lenticular, (1-2%), Lenticels are, small pores present, on the woody trunk, beneath the bark., , (~1%), Bark transpiration, is very little, but, its measured rate, is higher than, lenticular transpiration., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Transport in Plants 203, Advantages of Transpiration, (i) Ascent of sap It mostly occurs due to transpiration pull exerted, by transpiration of water. This pull also helps in the absorption, of water., (ii) Removal of excess water It has been held that plants absorb, far more amount of water than is actually required by them., Transpiration, therefore removes the excess of water., (iii) Cooling effect Transpiration, by evaporating water, lowers, down their temperature by 10 -15° C., (iv) Mechanical tissue The development of mechanical tissue,, which is essential for providing rigidity and strength to the, plant, is favoured by the increase in transpiration., (v) Distribution of mineral salts Mineral salts are mostly, distributed by rising column of sap., (vi) Increasing concentration of mineral salts The loss of water, through transpiration increases the concentration of mineral, salts in the plant., (vii) Root system Transpiration helps in better development of root, system which is required for support and absorption of mineral, salts., (viii) Quality of fruits The ash and sugar content of the fruit, increase with the increase in transpiration., (ix) Resistance Excessive transpiration induces hardening and, resistance to moderate drought., (x) Turgidity Transpiration maintains the shape and structure of, plant parts by keeping cells turgid., (xi) Photosynthesis Transpiration supplies water for photosynthesis., Disadvantages of Transpiration, (i) Wilting Wilting or loss of turgidity is quite common during, noon due to transpiration rate being higher than the rate of, water absorption. Wilting reduces photosynthesis and other, metabolic activities., (ii) Reduced growth Transpiration reduces availability of water, inside the plant. As reported by Tumarov (1925), a single, wilting reduces growth by 50%., (iii) Abscisic acid Water stress produces abscisic acid. Abscisic, acid prevents several plant processes and promotes abscission of, leaves, flowers and fruits., (iv) Wastage of energy Since most of the absorbed water is lost in, transpiration, it is wastage of energy., , www.aiimsneetshortnotes.com
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204, , Telegram @neetquestionpaper, , Handbook of Biology, , Factors Affecting Transpiration, Internal Factors, , External Factors, , Leaf surface area +, , Relative humidity –, , Sunken stomata –, , Temperature +, , Transpiration, , Light +, Wind +, , Thick cuticle –, Mesophyll –, , Soil water +, , ⊕ = increase the transpiration with increase in related factor., s = decrease the transpiration with increase in related factor., , Uptake and Transport of Mineral Nutrients, (i) Mineral salt absorption Earlier, scientists had opinion that, inorganic salts are passively carried into plants with the, absorption of water and the absorbed salts are translocated to, the different parts of the plant through transpiration stream., Now-a-days, it has been established that mineral salt, absorption is an active process rather than passive, as it was, considered earlier., (ii) Active mineral absorption The absorption of ions against, the concentration gradient or with the help of metabolic energy, is known as active absorption., Following theory have been proposed to explain the, phenomenon of active absorption., The carrier concept (Vanden Honert, 1937) According to, this theory, ‘The carrier molecules of ions combine with ions in, outer free space to form carrier-ion complex. This complex, moves through intermediate space into inner space where it, releases ions. The carrier compound can return back to outer, space, but ions cannot’., The observations like isotopic exchange, saturation effect, and specificity, greatly support the carrier concept of active, absorption of mineral salts., , Translocation of Mineral Ions, The translocation of mineral salts/ions takes place both by xylem and, phloem. The upward movement usually occurs through xylem while, bidirectional movement occurs through phloem., pH, , Decrease — Leads to absorption of anions, Increase — Leads to absorption of cations, , The chief sinks for the mineral elements are the growing regions of the, plant such as apical and lateral meristem, young leaves, etc., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Transport in Plants 205, Translocation and Storage of Food in Plants, (Phloem Transport), Food, primarily sucrose, is transported by the vascular tissue, phloem, from source to a sink. The transport of food from the production centre, (leaves) to the consumption centre (apices, roots, fruits, tubers) is, called translocation of organic solutes., , Routes of Translocation, Solutes are translocated in various directions within the plants., These may be, (i) Downward translocation of organic solute – From leaves to root, and other parts of plant., (ii) Upward translocation of organic solute – Roots to leaves or other, apical regions., (iii) Upward translocation of mineral salts – Occurs through xylem, by active transport., (iv) Upward movement of solute – Movement of salts to the leaves., (v) Lateral translocation of solutes – Translocation in tangential, direction in woody stems., , Mechanism of Translocation, There are several theories that have been put forward to explain the, mechanism of organic solute movement., The most accepted theory which explains the mechanism of, translocation is Mass Flow Theory. Some of the theories including, mass flow are as follows, , Diffusion Theory (Mason and Maskell, 1928), Translocation through transpiration stream., , Mass or Pressure Flow Theory (Ernst Munch, 1930), It is also known as pressure flow hypothesis or Munch, hypothesis. According to this hypothesis, the organic solute, translocates in following steps, (i) Phloem loading is an active transport mechanism. It is carried, out by a specific carrier protein molecules in the cell surface, membrane of companion cells that uses energy of ATP. This, energy is obtained from the photosynthesising mesophyll cells., Transportation occurs to the sieve tubes by the veins of a leaf., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 206, , Handbook of Biology, , (ii) Long distance transport of sucrose in the stem and root, phloem., (iii) Phloem unloading is a passive transport mechanism from the, sieve tubes to the cells at the root tip. It takes place passively, down a concentration gradient of sucrose. The transfer cells are, often present at unloading sites. Phloem unloading also requires, metabolic energy, that is used by sink organs for respiration and, biosynthetic reactions., Source, (e.g., leaf), , High pressure, Solutes, +, Water, , Xylem vessel, Companion, cell (transfer, cell), Sieve tube, Sieve tubes, , Mass flow, of solution, , Stem, , Solutes + Water, Low pressure, , Sink, (e.g. root), , Loading of sieve tubes takes place, here. Photosynthetic cells make, sugars, particularly sucrose and, other organic solutes. Companion, cells use energy to collect solutes by, active transport. As solute, concentration increases in the, Minor companion cells, water enters by, vein osmosis. A pressure is created,, which pushes the solutes through, plasmodesmata into the sieve tubes., Translocation Pressure inside sieve, tubes is greatest at the source and, lowest at the sink. It pushes sucrose,, etc., from source to sink., Unloading of the sieve tubes takes, place at the sink. Solute is removed, for use, thus maintaining the, pressure gradient in the sieve tubes., Sinks are any region where solutes, are being used, e.g., roots, fruits,, storage organs and regions of, growth., , Movement of solutes such as sucrose through the phloem of a plant., Three stages are involved, namely movement of solutes from, photosynthetic cells to sieve tubes (loading), translocation in, phloem and unloading at a sink., , Transcellular Streaming Theory (Thaine; 1962, 1969), Translocation through peristaltic movements in continuous tubular, strands in sieve tubes., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 12, Mineral Nutrition, in Plants, Almost all organisms require several elements to perform various, functions in their body. The elements are of biological importance and, their absorption is the theme of mineral nutrition., , Classification of Mineral Nutrients, On the basis of their essentiality in body, the minerals can be, categorised into, (i) Essential Mineral Elements (17 in number) These elements, have specific structural or physiological role. These are, indispensable for plants to complete their life cycle, e.g.,, nitrogen, phosphorus, etc., (ii) Non-Essential Mineral Elements (other than 17 essential), These elements are required in some plants, but not all. Their, absence does not produce any major deficiency symptoms in, plants, e.g., cobalt, silicon, sodium, etc., On the basis of their occurrence in dry matter of living organisms,, minerals are of following types, (i) Micronutrients/Microelements/Trace elements (equal to, or less than 100 mg/kg of dry matter) These act as cofactors or, activators for the functioning of enzymes. These are eight in, number, e.g., Zn, Mn, B, Cu, Mo, Cl, Ni and Fe., (ii) Macronutrients/Macroelements (1000 mg/ kg of dry matter), These are involved in the synthesis of organic molecule. These, are nine in number, e.g., C, H, O, N, S, P, K, Mg and Ca., , www.aiimsneetshortnotes.com
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208, , Telegram @neetquestionpaper, , Handbook of Biology, , Macroelements, , Microelements, Iron, , C, H, O, , It plays a role in synthesis, of chlorophyll and other pigments., It is the activator of various enzymes., , These are protoplasmic, constituents and building, blocks of body., , Manganese, , Nitrogen, , It leads to photolytic evolution, of oxygen. It also acts as electron, donor for chlorophyll-b., , Required for synthesis, of several biomolecules, as proteins, vitamins, etc., , Molybdenum, , Phosphorus, , It plays a role in nitrogen metabolism,, ascorbic acid synthesis and other, oxidation-reduction reactions., , It is needed for, synthesis of nucleic, acid, cell membrane, and some proteins., , Boron, It is essential for meristematic, tissues, helps in uptake of water., It leads to cell elongation and cell, differentiation., , Copper, , Potassium, Minerals, The inorganic, elements present, in soil., , Chiefly acts as coenzyme, for about 40 enzymes., Plays a role in active, transport and Na+/K+, pump., , Calcium, , It is involved in electron transport, and chlorophyll synthesis., Maintenance of nitrogen balance., , Zinc, It is the constituent of several plant, growth substances. Helps in the, utilisation and evolution of CO2., , Chlorine, Essential for O2 evolution in, photosynthesis. It is required, for cell division and production, of fruits., Nickel, It plays a role in metabolism, of urea and ureids., , It helps in proper development, of cell walls. It is also required for, cell division and enlargement, of cell., , Magnesium, It is a part of chlorophyll, and ribosome. Helps in, metabolism of fats and, phosphate., , Sulphur, It induces the root, development and, nodule formation., It is the constituent, of several biomolecules as, amino acid, vitamins, etc., , On the basis of their diverse functions, the essential elements can be, classified into four different categories, (i) As components of biomolecules, e.g., carbon, hydrogen,, oxygen and nitrogen., (ii) As components of energy related compounds, e.g., Mg in, chlorophyll and P in ATP., (iii) Regulator of osmotic potential, e.g., potassium controls the, opening and closing of stomata., (iv) As regulator of enzyme activity, e.g., Mg 2+ activates, RuBisCO, Zn 2+ activates alcohol dehydrogenase., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Mineral Nutrition in Plants, 209, Deficiency Symptoms of Essential Mineral Nutrients, These symptoms appear in plant when the mineral supply of an, essential element becomes limited. The minimum concentration at, which plant growth is retarded is termed as critical concentration., A detailed account of certain symptoms is as follows, Little Leaf, White Bud, The young buds, become whitish due to, the loss of chlorophyll., , Leaves are quite, small and, numerous., , Chlorosis, Non-development or loss, of chlorophyll. It is, due to the deficiency of, N, K, Zn, etc., , Necrosis, Dieback, Death of root apex,, leads to stunted, growth., , Rot, Softening or, rotting of internal, tissues, external, cracks., , Deficiency, Symptoms, , Death of tissues. It, is due to the deficiency, of Ca, Mg, Cu, etc., , Mottling, , Wilting, Loss of turgor leads, to curling of leaves., , Patches of green and, non-green areas produced, in leaves., , Abscission, Premature fall of, leaves, fruits and flowers., , Deficiency symptoms of essential mineral elements, , Toxicity of Micronutrients, (i) The moderate increase in the concentration of micronutrients, causes its toxicity., (ii) Any mineral ion concentration in tissues which reduces dry, weight of tissue by 10% is called ‘toxic concentration’., (iii) The critical toxic concentration is different for different, micronutrients as well as different plants., (iv) The toxicity of one mineral, mostly leads to the inhibition of, absorption of other micronutrients., , Hydroponics, In 1860, Julius von Sachs demonstrated for the first time that plant, could be grown to maturity in a defined nutrient solution in complete, absence of soil., The soilless production of plants is called hydroponics. It is also, known as soilless culture or solution culture (Georick; 1940)., , www.aiimsneetshortnotes.com
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210, , Telegram @neetquestionpaper, , Handbook of Biology, , There are three methods for growing plants with nutrient solutions, , Dacron (cotton), , Aerating tube, Nutrient solution, , Funnel for adding water, and nutrients, , (i) Hydroponic Culture Using nutrient solution in this culture,, an airtight container is supplied by air through a tube and, nutrients through a funnel., , A typical tube for nutrient solution culture, , (ii) Slop Culture Nutrient solution using sand. In this, the, plants are grown on sand column, the nutrient solution is, poured at regular intervals from upside., (iii) Nutrient Film Technique The nutrient solution drains, through plant roots, through a channel. In this process, the, plant roots do not have any substratum but they are bathed, regularly with nutrient solution., , Roots of plant bathed, in nutrient solution, , Nutrient solution, Pump, , Hydroponic film growth system, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 211, Mineral Nutrition in Plants, Metabolism of Nitrogen, Nitrogen exists as two nitrogen atoms joined by a very strong triple, bond. It is needed by plant for the production of protein, nucleic acid,, chlorophyll and many other vitamins., , Nitrogen Cycle, It is an example of gaseous biogeochemical cycle, which leads to the, cycling of nitrogen in various pools (i.e., atmosphere, soil and living, organisms)., Nitrogen in the Atmosphere, (N2), Nitrogen-fixing, bacteria, in roots, , Haber process, , Lightning, and rain, , Excretion, and, decay, , Ammonia, Decay, , Feeding, , Plant, Compounds, , Decay, , Nitrite, (NO2– ), Chemical, fertiliser, , Animal, Compounds, , Plant growth, , Nitrifying, bacteria, , Nitrogen-fixing, bacteria in, soil, , Denitrifying, bacteria, , Nitrate in Soil, (NO3– ), , Nitrogen cycle, , A regular supply of nitrogen to the plant is maintained through, nitrogen cycle. Plants obtain nitrogen from soil as NO3– (nitrate),, NH +4 (ammonium) and NO–2 (nitrite) ions., , Nitrogen-Fixation, It is the conversion of free nitrogen into nitrogenous compounds, to make it available for absorption by plants., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Mineral Nutrition in Plants, 213, , Infection, thread, containing, bacteria, Inner cortex and pericycle, cells under division, , (d) Mature nodule, , (c) Formation of infection thread, , Development of root nodules in soybean, , Biochemistry of Nitrogen-Fixation, Schneider et al. (1960) and Carnahan et al. (1960) studied the, nitrogen-fixation by radiolabelling and confirmed the conversion of, nitrogen into ammonia., Basic, (i), (ii), (iii), (iv), (v), (vi), (vii), , requirements for N 2-fixation are as follows, Nitrogenase and hydrogenase enzyme., A mechanism which protects nitrogenase from oxygen., Ferredoxin., Constant supply of ATP., Coenzymes and cofactors like TPP, Co-A, iP and Mg+2., Cobalt and molybdenum., A carbon compound to trap released ammonia., , The most important requirement of N 2-fixation is nitrogenase enzyme, which has two sub-units. These are, Fe containing unit Dinitrogen reductase., Mo containing protein Dinitrogenase., l, , l, , The enzyme nitrogenase is highly sensitive to molecular oxygen (O2 ), and gets inactivated when exposed to it. The nodule formation is to, provide anaerobic condition to this enzyme., Decomposition of organic nitrogen of dead plants and animals into, ammonia is called ammonification., Ammonia is oxidised to nitrite which is further oxidised to nitrate, called nitrification., l, , l, , www.aiimsneetshortnotes.com
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214, l, , Telegram @neetquestionpaper, , Handbook of Biology, , The nitrate in soil is reduced to nitrogen by the process of, denitrification., The basic nitrogen-fixing reaction is as follows, Dinitrogenase, enzyme complex, , N 2 + 8e + 8H + 16ATP → 2NH3 + 2H + + 16ADP + 16Pi, –, , +, , The chemically fixed nitrogen is used by both plants and animals to, synthesise various biomolecules of diverse uses., , Fate of Ammonia, Ammonia produced combines with organic acids to produce amino, acids by following methods., Reductive Amination Ammonia formed combines with keto acid, to form amino acid in the presence of a reduced coenzyme and, enzyme dehydrogenase., Transamination Transfer of amino groups from an amino acid, with carboxyl group of a keto acid is transamination., l, , l, , Soil as Reservoir of Essential Elements, Soil acts as the most stable reservoir for both nutrients and organisms, to harbour in it. Various inorganic salts and ions derived from, rock minerals present in soil are known as mineral nutrients., Natural process like weathering and humification enrich the, nutritional content of soil, while some artificial processes like, fertilisers (i.e., chemical and organic) also lead to nutritional, enrichment of soil., , www.aiimsneetshortnotes.com
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13, , Telegram @neetquestionpaper, , Photosynthesis, in Higher Plants, Photosynthesis is the only mechanism of energy input into living, world. Only exceptions are chemosynthetic bacteria that obtain energy, by oxidising inorganic substances., The synthesis of organic compounds like carbohydrates or glucose by, the cells of green plants in the presence of sunlight with the help of, CO2 and H 2O is called photosynthesis., Photosynthesis is sometimes called as carbon assimilation and is, represented by following equation,, Light energy (686 kcal), , 6CO2 + 6H 2O , → C6H12O6 + 6O2, Green plants, , The whole process can be demonstrated as, Light, , Starch, , Chlorophyll, , H 2O, OH–, , H+, , P, , ADP, NADP, , NADP, , ADP, , O2, , P, , NADPH2 + ATP, Assimilatory, power, Grana, Light Phase, , Sugar, phosphate, , (X), , CO2, , Stroma, Dark Phase, , Chloroplast, , Demonstration of light dependent and light independent, phases during photosynthesis, , www.aiimsneetshortnotes.com
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216, , Telegram @neetquestionpaper, , Handbook of Biology, , Chemistry and Thermodynamics of Photosynthesis, Photosynthesis is a chemical oxidation-reduction process in which, water molecules are oxidised to form O2 and CO2 molecules are, reduced to form carbohydrate. It is an enzyme regulated, anabolic, process of producing organic compounds., The annual CO2 fixation is about 70 billion tonnes which, requires about 1.05 × 1018 kcal of energy. The total solar energy falling, on the earth is 5 × 1020 kcal/year. The plants are thus able to utilise, only 0.2% of the solar energy received by the surface of the earth., , Historical Timeline of Photosynthesis, Only green plants, have the capacity of, purifying foul air in the, presence of sunlight., Ingenhousz, , Sachs, , 1779, , 1877, , Crystallisation of, photosystem of purple, sulphur bacteria., Huber, Michel, and Deisenhofer, , 1985, , Reported the role, of chloroplast, and found starch as, the first product, of photosynthesis., , Reported C4 cycle, for carbon-fixation., , Photosynthesis is a, photochemical, reaction in which, CO2 is fixed by using, the product, of light reaction., , Demonstrated, the photolysis, of water in, light reaction., Robin Hill, , Blackmann, , 1905, , Explained the Z-scheme, for light reaction., , Hatch and Slack, , Hill and Bendall, , 1967, , 1960, , 1939, Traced the path of, carbon in, photosynthesis and, gave details about, C3 cycle., Malvin Calvin, , 1954, , Landmark discoveries related to photosynthesis, , Chloroplast : Photosynthetic Organ of Cell, Chloroplasts are the green plastids which occur in all green parts of, the plants. These are the actual sites of photosynthesis., These occur mostly in chlorenchymatous cells (particullary in, mesophyll) of leaves and young stem. It is a double membranous, organelle in which the envelope encloses a liquid proteinaceous matrix, called stroma., It is a semi-autonomous organelle as it contains its own DNA and is a, characteristic feature of plant cells only. As complete food synthesis, takes place in chloroplast, it is also known as kitchen of the cell., , www.aiimsneetshortnotes.com
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218, l, , l, , l, , Telegram @neetquestionpaper, , Handbook of Biology, , Both chlorophyll-a and β-carotene are universal photosynthetic, pigment., The heaviest pigment of chloroplast is chlorophyll-b and the, lightiest one is carotene., Chlorophylls are directly involved in trapping of sunlight, while, carotenes protect the chlorophyll from photo-oxidation by bright, sunlight., , Mechanism of Photosynthesis, The process of photosynthesis is distinctly divided into two phases, 1. Photochemical phase, 2. Biosynthetic phase, , 1. Photochemical Phase/Light Reaction/Hill Reaction, It occurs inside the thylakoids. The function of this phase is to produce, assimilatory powers (i.e., ATP, NADPH, etc). It occurs in grana of, chloroplast., It includes following events, (i) Light absorption, (ii) Splitting of water, (iii) Release of oxygen, (iv) Formation of high energy chemical intermediates, Several complexes of protein and other pigments are involved in light, reaction or photochemical phase., (i) Light Absorption, The molecule which is responsible for absorption of light is a protein, based complex called Light Harvesting Complex (LHC), which is, organised into PS-I and PS-II., (a) Photosystem-I or Pigment System-I The reaction centre in, this pigment system is P700, which absorbs the light of wavelength, 700 nm. It has more of chlorophyll-a, chlorophyll-b and carotenoids, are comparatively less., PS-I can carry on cyclic photophosphorylation independently. The, PS-I with electron carriers is located on both the non-appressed, part of grana thylakoid and stroma thylakoids., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Photosynthesis in Higher Plants, 219, (b) Photosystem-II or Pigment System-II P680 functions as, reaction centre in this photosystem. The photons of lower, wavelength are absorbed by this photosystem. It is located, in appressed part of thylakoid and carries out non-cyclic, photophosphorylation with PS-I., PS-II has chlorophyll-a, b and carotenoids (according to some, physiologists, xanthophyll also functions as antenna in this, system)., (ii) Photolysis of Water/Splitting of Water, In photosynthesis, water is used as a source of hydrogen required for, the reduction of CO2 to form carbohydrate., Light, CO2 + 2H 2O , → CH 2O + H 2O + O2, Chlorophyll, , Light, 4H 2O , → 2H 2O + 4H + + 4e– + O2, Chlorophyll, , The first demonstration of photolysis of water was done by R Hill, (1937) and it was described by Van Niel (1931)., As a result of photosynthesis, the oxygen is released., (iii) Formation of High Energy Chemical Intermediate, These intermediates are reduced molecules which provide energy, during biosynthetic phase. There are various intermediates such as, NADPH 2 , NADPH and ATP., These are produced by two types of reaction, (a) Photophosphorylation, (b) Chemiosmosis in chloroplast, (a) Photophosphorylation, , The formation of ATP molecule from ADP and H3PO4 in the presence, of light and chlorophyll-a is called photophosphorylation., Light, , → ATP, ADP + H3PO4 Chla, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Photosynthesis in Higher Plants, 221, Only PS-I is involved in this phosphorylation., Primary, acceptor, No non-cyclic photophosphorylation, Fd, , Cytochrome, complex, , Light, , Pc, Energy for, chemiosmotic, synthesis of, , ~683 nm, Photosystem-I, P700, , ATP, , Diagrammatic representation of the cyclic photophosphorylation process, , This occurs when activity of PS-II gets ceased or non-cyclic, photophosphorylation is stopped due to certain reasons. The electron, emitted after illumination of PS-I returns back to its original place via, several electron carriers which ultimately lead to the synthesis of, NADPH., , Three Diverse Methods of Synthesising ATP, Process, , Energy Source, , Site, , Photophosphorylation, , Sunlight, , Chloroplast, , Substrate level phosphorylation, , Reaction not involving oxygen, , Cytosol, , Oxidative phosphorylation, , Oxidation with oxygen, , Mitochondria, , (b) Chemiosmosis in Chloroplast, , Like respiration, in photosynthesis too, ATP synthesis is linked to, development of a proton gradient across a membrane., , 2. Biosynthetic Phase (Dark Reaction/Blackmann’s Reaction), It occurs in stroma and the chief function of this phase is to produce, carbohydrate by using the assimilatory powers (i.e., products of light, reaction)., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Photosynthesis in Higher Plants, 223, In this cycle, 6 molecules of CO2 are used and one molecule of, fructose-6-P is produced as a byproduct at the expense of 12 molecules, of NADPH and 18 molecules of ATP., The overall reaction is expressed as, 6 CO2 + 12 NADPH + 12 H + + 18 ATP + 11 H 2O →, F-6-P + 12 NADP + + 18 ADP + 17Pi, (ii) C4 Pathway or Hatch-Slack Cycle, This cycle is present in those plants, which are adapted for hotter, climatic regions. Plants also possess a specific anatomy called Kranz, anatomy to fulfil the structural demand for C4 pathway., Upper epidermis, Mesophyll cells, , Bundle sheath, , Vascular bundle, , Bundle sheath, chloroplast, Mesophyll chloroplasts, , Kranz Anatomy : Part of C4 -plant leaf, showing mesophyll and bundle sheath cells, , These plants have Oxaloacetic Acid (OAA) as their first CO2 fixation, product. Through processes like fixation, decarboxylation and, regeneration, the carbohydrate is synthesised in bundle sheath cells of, leaf., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Photosynthesis in Higher Plants, 227, Factors Affecting Photosynthesis, , Light intensity, , Chlorophyll content, , Light, , Chlorophyll content, , Internal, Factors, , Byproducts, accumulation, , Amount of byproduct, After getting accumulated,, byproducts act as inhibiting, agent for photosynthesis., , Temperature, Rate of photosynthesis, , Rate of photosynthesis, , There are multiple, factors but the nature, of effect is not known., , CO2, , External, Factors, , Photosynthesis, , Structure, of leaf, , CO2 conc., , Water, Rate of photosynthesis, , Protoplasmic, , Initially CO2 increases the, rate of photosynthesis, but, after optimum level, it acts, as reducing factor., , Rate of photosynthesis, , Rate of photosynthesis, , The nature of effect, is not known., , Initially the rate, of photosynthesis, increases with light, intensity, but later it has, no significance over it., Rate of photosynthesis, , The rate of, photosynthesis, is increasing with, increased, chlorophyll content., , Temperature, After reaching to optimum, temperature (35-40°C),, further increase in, temperature reduces the, rate of photosynthesis., , Water content, Increased water, availability causes, steady increase in the, rate of photosynthesis., , Law of Limiting Factors (Blackman; 1905), If a chemical process is affected by more than one factors, then its rate, will be determined by the factor which is nearest to its minimal value., It is the factor which directly affects the process., , www.aiimsneetshortnotes.com
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228, , Telegram @neetquestionpaper, , Handbook of Biology, , 14, Respiration in, Plants, Respiration is the most important, cellular, enzymatically controlled,, catabolic process which involves the liberation of energy by oxidative, breakdown of food substances inside the living cells. The term, respiration was coined by Dutrochet., It has two phases, i.e., first phase involves gaseous exchange between, environment and organism through body surface or special respiratory, organs and second phase is cellular respiration., , Cellular Respiration, In this process, the oxidation of organic food takes place inside living, cell for the liberation of energy. On the basis of requirement of oxygen,, this may be categorised as, Cellular Respiration, , Aerobic Respiration, Organic food is completely, oxidised with the help of oxygen., It takes place in mitochondria, and the products are CO2 and water., (~ 673 kcal/mol, energy released), Enzymes, , C6H12O6+6O2, , 6CO2+6H2O, , Anaerobic Respiration, Organic food is broken down, incompletely to release energy in the, absence of oxygen. The products are, CO2 , ethyl alcohol and lactic acid., (~ 21 kcal/mol, energy released), C6H12O6, , Enzymes, , 2CO2+2C2H5OH+59 kcal/247 kJ, (ethyl alcohol), , +686 kcal/2810 kJ, C6H12O6, , Enzymes, , 2C3H6O3+36 kcal/150 kJ, (lactic acid), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Respiration in Plants 229, Respiratory Substrate, The substrates which are used as fuel in respiration are called, respiratory substrates. The main respiratory substrates are, carbohydrates and fat, but proteins can also be used in special, circumstances. The most common respiratory substrate is glucose., On the basis of respiratory substrate, respiration is of two types, (i) Floating respiration Carbohydrate and fat are used as, respiratory substrate., (ii) Protoplasmic respiration Protein is used as respiratory, substrate., , Respiratory Quotient, It is the ratio of volume of CO2 released to the volume of oxygen, absorbed. The value can be zero, one, less than one or more than one., RQ can be calculated as, RQ =, RQ, RQ, RQ, RQ, RQ, , =, >, =, =, =, , Volume of CO2 evolved, Volume of O2 absorbed, , 0, in succulents, 1, in anaerobic respiration, 1, Carbohydrates, 0.9, Proteins, 0.7, Fats, , Aerobic Respiration, It is stepwise catabolic process of complete oxidation of organic food, into CO2 and water with oxygen acting as a terminal oxidant., It is completed in two pathways—Common pathway and Pentose, Phosphate Pathway (PPP)., Aerobic respiration consists of three steps, 1. Glycolysis, 2. Krebs’ cycle, 3. Electron transport chain and terminal oxidation., , 1. Glycolysis (Gk. Glycos – sugar; lysis – dissolution), Glycolysis was discovered by three German scientists Embden,, Meyerhof and Paranas, so also called as EMP Pathway. Glycolysis, occurs in cytoplasm., Glycolysis is a major pathway for ATP synthesis in tissues lacking, mitochondria, e.g., erythrocytes, cornea, lens, etc., , www.aiimsneetshortnotes.com
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230, , Telegram @neetquestionpaper, , Handbook of Biology, , Net reaction of Glycolysis, Glucose + 2NAD+ + 2ADP + 2H3PO4 →, 2 Pyruvate + 2NaOH + 2H + + 2ATP, , Schematic Representation of EMP Pathway, Glucose, 1, , Mg2+, , Hexokinase, , ATP, ADP, , 1. It is an irreversible reaction in which terminal, phosphate of ATP is transferred to an acceptor, nucleophile. Hexokinase is present in all cells of, organisms. In liver cells it is called as, glucokinase. It is the first priming reaction., , Glucose-6- P, , 2. This is a reversible reaction which can, proceed in either directions by small change in, standard free energy., , 2, , Phosphohexose, Isomerase, , Mg2+, , Fructose-6- P, Phosphofructo, kinase, , 3, , Mg2+, , ATP, ADP, , Fructose1, 6-biphosphate, 4, , Aldolase, , 3. It is the second priming reaction of, glycolysis and first ‘committed’ step. Some, bacteria and protists have a, phosphofructokinase that use Pi not ATP as the, phosphoryl group donor., 4. This reaction is an example of reversible, aldol condensation. Zn 2+ is the cofactor which, cleaves the fructose 1, 6 biphosphate into two, 3-carbon units., , 5, , Glyceraldehyde-3- P, , Pi, , Glyceraldehyde Phosphate, Dehydrogenase, , 6, , Dihydroxy Acetone -3- P, Triose Phosphate, Isomerase, 5. As only glyceraldehyde-3-(P) can proceed in, further reactions of glycolysis, the dihydroxy, acetone phosphate is converted reversibly into, glyceraldehyde-3-(P). It is the last reaction of, preparatory phase., , NAD, , 6. The first step of payoff phase that, eventually leads to the formation of ATP. This, NADH + H reaction is irreversibly inhibited by Mg 2 + ., , 2×1, 3 biphosphoglycerate, 7, ATP, Phosphoglycerate Mg2+, Kinase, ADP, 2×3- phosphoglycerate, Phosphoglycerate, Mutase, , 8, , Mg2+, , 2×2- phosphoglycerate, 9, , 2+, Enolase Mg, H 2O, 2× phosphoenol pyruvate, 10, ADP, Pyruvate Mg2+, K+, Mn2+, Kinase, ATP, 2× pyruvate, , 7. It is an exergonic reaction which is in, combination with step-(6) and constitutes an, energy coupling process. It is an example of, substrate level phosphorylation., 8. In this reaction the enzyme,, phosphoglycerate mutase catalyses a reversible, shift of phosphoryl group between C 2 and C 3., 9. The enzyme enolase promotes reversible, removal ofH2O molecule from 2 phosphoglycerate, to produce phosphoenol pyruvate., 10. In this substrate level phosphorylation,, the product first appears in its enol form that, rapidly and non-enzymatically changes to its, keto form at pH 7., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Respiration in Plants 231, Net Result of Glycolysis, l, , l, , l, , l, , Two, Two, Two, Two, , molecules, molecules, molecules, molecules, , of pyruvic acid, of ATP, of NADH 2, of H 2O, , ATP released 4 ATP, From 2 NADH 2 6 ATP, Total released 10 ATP, Total ATPs consume 2 ATP, 8 ATP Net yield of glycolysis, , 2. Krebs’ Cycle or Tricarboxylic Acid Cycle, l, , l, , l, , l, , l, , It is also known as citric acid cycle because citric acid, (tricarboxylic acid) is the first product of this cycle., In eukaryotic organisms, all the reactions of Krebs’ cycle takes place, in matrix of mitochondria because enzymes of this cycle are present, in matrix except succinic dehydrogenase (situated in inner, membrane of mitochondria)., In prokaryotes, the Krebs’ cycle occurs in cytoplasm. It is basically a, catabolic reaction, as it oxidises acetyl Co-A and organic acid into, CO2 and H 2O., It acts as an amphibolic pathway because it serves in both, catabolic and anabolic processes. It is a series of 8 reactions which, occur in aerobic environment., The overall reaction of aerobic degradation of pyruvic acid is as, follows (This includes oxidative decarboxylation and TCA), Pyruvic Acid + 4NAD+ + FAD + 2H 2O + ADP + Pi →, 3CO2 + 4NADH + 4H + + FADH 2 + ATP, , www.aiimsneetshortnotes.com
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232, , Telegram @neetquestionpaper, , Handbook of Biology, , The scheme of reactions with their detail are explained as follows, Step 1. Acetyl Co-A adds its two-carbon fragments, to oxaloacetate, a four-carbon compound., The unstable bond of acetyl Co-A is, Pyruvic acid, broken as oxaloacetate displaces the, +, NAD, coenzyme and attaches to the acetyl group., NADH2, The product is six-carbon citrate., S–Co-A, Co-A is then free to prime another two-carbon, Step 8. The last oxidative step, |, fragment derived from pyruvate., produces another molecule, C=O, Notice that oxaloacetate is regenerated by, of NADH and regenerates, |, the last step of the cycle., oxaloacetate, which accepts, CH3, Step 2. A molecule of water is, a two-carbon fragment from, Acetyl Co-A, –, removed and another is, acetyl Co-A for another turn COO, Co-A–SH, |, COO–, added back. The net result, of the cycle., O=C, is the conversion of citrate, CH2, |, NADH, to its isomer, isocitrate., 1, CH2, –, –, HO C COO, COO, H2O, +H+, |, –, +, COO, CH2, CH2, NAD, 8, –, –, –, 2, COO, HC–COO, COO, Oxaloacetate, HO, , CH, , Citrate, , HO–CH, –, , CH2, , COO, , A, –, , Isocitrate, , COO, , Malate, H 2O, , Step 3. The substrate, , CO2, , Three inhibitors, , 7, , 3, , –, , COO, , NAD+, , loses a CO2, molecule and, the remaining, five-carbon, compound is, oxidised,, reducing NAD+, to NADH., , B, –, NADH+H+, CH, COO, C, substrate are, Fumarate, rearranged in HC, CH, 2, Co-A–SH, this step by, –, CH2, α-ketoglutarate, COO, the addition, –, COO, –, of a water, C=O, COO, 6, 4, molecule., Co-A–SH, CH2, CH2, COO–, FADH2, CH2, CO2, CH2, +, 5, NAD, FAD, C=O, –, COO, Step 6. In another, NADH, oxidative step, Succinate GTP GDP+Pi S–Co-A, +, +H, two hydrogens, Succinyl Co-A, are transferred, Step 4. This step is catalysed by a, to FAD to form, ADP, multienzyme complex very, FADH2., similar to the one that, ATP, converts pyruvate to acetyl, Co-A. CO2 is lost, the, remaining four- carbon, Step 5. Substrate level phosphorylation occurs in, compound is oxidised by, this step. Co-A is displaced by a phosphate, the transfer of electrons to, group, which is then transferred to GDP to, NAD+ to form NADH and is, form Guanosine Triphosphate (GTP). GTP is, then attached to coenzyme–A, similar to ATP, which is formed when GTP, by an unstable bond., donates a phosphate group to ADP., , Step 7. Bonds in the, , The Krebs’ cycle, , The enzymes involved in these reactions are, 1., 2., 3., 4., 5., 6., 7., 8., , Citrate synthase, Aconitase, Isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, Sunccinyl Co-A synthetase, Succinate dehydrogenase, Fumerase, Malate dehydrogenase, , Three inhibitors are, A. Fluoroacetate, B. Arsenic dehydrogenase, C. Malonate, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Respiration in Plants 233, Output of Krebs’ Cycle, One molecule of pyruvic acid after entering into mitochondria, undergoes three decarboxylations and five oxidations. One, molecule of pyruvic acid through Krebs’ cycle yields an equivalent of, 15 ATP molecules., , 3. Electron Transport Chain (ETC), Electron Transport Chain (ETC) or Respiratory Chain (RC) is present, in the inner membrane of mitochondria. When the electrons pass from, one carrier to another in electron transport chain, they are coupled to, ATP synthase for the production of ATP from ADP and inorganic, phosphate., A diagrammatic representation of electron flow via various electron, carrier complexes is shown in figure., Cytosol, Outer Membrane, Intermembrane Space, , H+, , H+, , H+, , cyt. c (Fe2+), red, , Complex, I, ox, , red, , ox, UQH2, , Complex, II, , Complex, III, , Inner, Complex, Membrane, IV, , ox, , NAD+, , H+, , ox, , red, , UQ, , NADH, +, H+, , cyt. c (Fe3+), , red, , FADH2 FAD, H+, , 1/2 O2, +, 2H+, , H+, , H 2O, , ATP, Synthase, , H+, ADP, , Mitochondrial matrix, , ATP, , red = reduced,, ox = oxidised, , Electron transport chain in plants, , The enzymes of inner membrane appear to exist as components of, these five complexes. The first four members among these complexes, constitute the electron transport system, while the 5th complex is, connected with oxidative phosphorylation, i.e., conservation and, transfer of energy with ATP synthesis. These complexes are, (i), (ii), (iii), (iv), (v), , Complex I — NADH/NADPH : CoQ reductase, Complex II — Succinate : CoQ reductase, Complex III — Reduced CoQ (CoQH 2) Cytochrome-c reductase, Complex IV — Cytochrome-c oxidase, Complex V — ATP synthase, , www.aiimsneetshortnotes.com
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234, , Telegram @neetquestionpaper, , Handbook of Biology, , The complex V is ATP synthase complex which has a head piece, stalk, and a base piece. Out of these, the head piece is identified as the, coupling factor 1 (F1) by Racker (1965). It contains 5 subunits namely, — α (MW 53000), β (MW 50000), γ (MW 33000), δ (MW 17000) and, ε (MW 7000). In addition to these, an ATPase inhibitor protein is also, seen in this portion., The stalk portion contains OSCP (i.e., Oligomyosin Sensitivity, Conferring Protein) and is necessary for binding F1 to the inner, mitochondrial membrane. The base piece is isolated as F0 and present, within the inner mitochondrial membrane. It provides the proton, channel. Thus, the complete complex looks like, 100 nm, , ATP, , OSCP, , ADP + Pi, , Cytosolic, medium, H+, , a, Exoplasmic, medium, , c, , c c, , c, , Rotation of, H+, base piece (c) ring, Proton bound, Proton half-channel, to aspartate, , F0 − F1 complex ( γ , ε and c constitute the, rotatory part), , Oxidation phosphorylation was discovered in 1939. There are three, hypotheses regarding the mechanism of oxidative phosphorylation. These are, The chemical coupling hypothesis, The chemiosmotic hypothesis, The conformational hypothesis, l, , l, , l, , The most accepted mechanism among these hypotheses is the, conformational hypothesis., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Respiration in Plants 235, According to conformational coupling hypothesis, the membrane of, cristae is found to assume different forms during functional states of, mitochondrion as shown in the following figures, , Energy–120°, rotation of γ, , 1, b, , T, , i, , β3, , O, , 2, , H 2O, , L, γ, , T, , β2, O, , Energy–120°, rotation of γ, , 3, , β3, ADP+Pi, , β1, , P, AT, , T, , ADP+Pi, , ADP+Pi, β1, , ATP, formation, β2 in T site, , P, AT, , β3, , β2, , L, γ, , T, , O, β3, , γ, , β2, L, , AD, P+, Pi, , O, , L γ, , β1, , Pi, P+, AD, , P, P+, AT, , c, , ADP+Pi, , AT, P, , β1, , a, , AT, P, , ADP+Pi, , The binding change mechanism of ATP synthesis from ADP and Pi, is carried out by the F0-F1 complex., The β subunits of head piece are designated as β1 , β 2 and β3 as, shown. Look at the middle γ subunit structure which shows different, appearance in three different β subunits as, (i) Darker pointed portion indicating open conformation (O), of β-subunit with suppressed margins so that, ADP and Pi can, attach easily., (ii) Lighter pointed portion indicating tight conformation (T), with elevated tight margins helpful in converting ADP + Pi to, ATP., (iii) Lighter rounded portions indicating low conformation, (L) is intermediate of above two conformations, binds ADP and, Pi loosely., The movement of γ subunit is possible only with the help of energy., See the conformational changes step by step with ATP formation., The energy provided for γ subunit movement is through proton, translocation as shown in first diagram., A formation of 3 ATP molecules occurs for every 360° rotation of γ., , The conformational hypothesis does not affect the central theme of, Mitchell’s chemiosmotic hypothesis. Mitchell (1976) himself, considered the involvement of conformational changes in, chemiosmotic coupling. Infact Mitchell’s hypothesis becomes more, convinced when coupled with conformational processes., , Oxidative Phosphorylation, The aerobic respiration is ended with the oxidation of 10 molecules of, NADH + H + and 2 molecules of FADH 2 generated from a molecule of, glucose. In this, the oxygen from atmosphere is used for the, oxidation of reduced coenzyme and it is called as terminal, oxidation. The production of ATP with the help of energy liberated, during oxidation of reduced coenzyme and terminal oxidation is, called oxidative phosphorylation., , www.aiimsneetshortnotes.com
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236, , Telegram @neetquestionpaper, , Handbook of Biology, , Summary of Aerobic Respiration, 1. Glycolysis produces 2ATP molecules and 2 NADH +2 H + ., 2. Pyruvate oxidation yields 2 NADH + 2H + ., 3. Krebs’ cycle produces 2GTP molecules, 6 NADH + 6H + and, 2 FADH 2., 4. Electron transport system, (i) 2 NADH + 2 H + molecules from glycolysis yield 4 ATP, molecules via route-2 of ETC (glycerol-phosphate shuttle) or, six ATP molecules via route-1 (malate-aspartate shuttle)., (ii) 2 NADH + 2H + molecules from pyruvate oxidation yield, 6ATP molecules via route-1 of ETC., (iii) 6 NADH + 6H + molecules from TCA (Krebs’ cycle) yield, 18 ATP molecules via route-1 of ETC., (iv) 2 FADH 2 molecules from TCA cycle yield 4 ATP molecules, via route-2 of ETC (Electron Transport Chain)., Hence, ETS alone produces 32 or 34 ATP molecules., 2ATP + 2GTP + 32 / 34 ATP → 38 / 36 ATP, (Glycolysis), , (TCA cycle), , (ETS/ ETC), , 34 or 36 ATP + 2 GTP molecules are produced from one glucose, molecule., A cytoplasmic enzyme nucleoside diphosphate kinase readily, converts the GTP formed in TCA cycle to ATP., In prokaryotic cells, oxidation of glucose molecule always yields, 38 ATP molecules as NADH + H + molecules are not to enter, mitochondria, which are absent here., , Overall Result of Aerobic Respiration, Complete oxidation of one molecule of glucose results into the following, products, Release of 6 carbon dioxide molecules., Utilisation of 6 oxygen molecules., Formation of 12 H 2O molecules., So, overall process of aerobic respiration may be shown by the following, equation, C6H12O6 + 6O2 + 10H 2O → 6CO2 + 16H 2O + 686 kcal energy., l, , l, , l, , Pentose Phosphate Pathway (PPP), This pathway is a major source for the NADPH required for anabolic, processes. There are three distinict phases – Oxidation, isomerisation, and rearrangement. Gluconeogenesis is directly connected to the PPP., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Respiration in Plants 237, Pentose phosphate pathway (Warburg-Lipman-Dickens cycle) is an, alternate method of aerobic respiration, which occurs in the cytoplasm, of mature plant cells. This pathway accounts for 60% total respiration, in liver cells. In this, for every six molecules of glucose, one molecule is, completely oxidised in CO2 and reduced coenzymes, while five, molecules are regenerated., Glucose-6-phosphate, Glucose-6NADP+, phosphate, NADPH, dehydrogenase, , Ribulose-5-phosphate, (Pentose phosphate epimerase), , Pentose phosphate, isomerase, , Ribulose-5-phosphate, 6-phosphogluconate, NADP+, CO2, NADPH, Gluconate-6phosphate, dehydrogenase, , Xylulose-5-phosphate, , Transketolase, , Glyceraldehyde- 3-phosphate, , Ribulose-5-phosphate, , Sedoheptulose-7-phosphate, Transaldolase, , Hexose phosphate, isomerase, Erythrose4-phosphate Transketolase, Glyceraldehyde-3-phosphate, , Fructose-6-phosphate, , Reactions of the oxidative pentose phosphate pathway in higher plants, , The Pentose Phosphate Pathway (PPP) is an alternate path to, generate ATP beside glycolysis and Krebs’ cycle., , Anaerobic Cellular Respiration, This type of respiration has fermentation as its main process., , Fermentation, It is the general term for such processes which extract energy (as ATP),, but do not consume oxygen or change the concentration of NAD+ or, NADH. It is similar to anaerobic respiration., Generally, the fermentation is of four types, Fermentation, Alcoholic, Fermentation, It is common in yeast, in which breakdown, of the substrate takes, place outside the cell., The end products are, ethyl alcohol, CO2, and energy., , Butyric Acid, Fermentation, This pathway is common, in Clostridium butyricum., This type of fermentation, normally occurs in, rotten butter due to, which it gives fowl smell., , Lactic Acid, Fermentation, It is common in, lactic acid bacteria., Enzyme involved in, fermentation is lactic, acid dehydrogenase., Here only lactic acid,, NAD and energy are, produced., , Acetic Acid, Fermentation, This pathway is, common in acetic, acid bacteria., The oxygen is used, in this fermentation, process. The end, products are ethyl, alcohol and acetic acid., , www.aiimsneetshortnotes.com
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238, , Telegram @neetquestionpaper, , Handbook of Biology, , Krebs’ Cycle (Respiration) as Amphibolic Pathway, This pathway involves both breakdown (catabolism) and formation, (anabolism) of biomolecules. Krebs’ cycle is amphibolic in nature, as its, intermediates are used in other anabolic processes., A general representation of amphibolic pathway is as follows, Respiratory Substrate, , Carbohydrate (major), , Fat (minor), Breakdown, , Protein (minor), , Breakdown, Glucose, , Fatty acid, , Amino acids, , Glycerol, Glucose-6–Phosphate, , Fructose 1, 6- bis phosphate, , F, DHAP, , G3P, Pyruvic acid, Acetyl Co–A, Krebs’, cycle, CO2, , Amphibolic pathway of respiration, , Factors Affecting Respiration, Tissue Injury, Directly proportional, Minerals, Directly proportional, , Amount of oxygen, Directly proportional, , Respiration, Dehydration, Inversely proportional, , Light Intensity, Directly proportional, Temperature, Directly proportional, , Conclusively, respiration is a vital phenomenon in almost all, living organisms, involved in breakdown of different substances,, i.e., respiratory substrates. In all of the organisms, it is involved in, both catabolism and anabolism. Respiration and its strategies are also, the determining factor for several physical, physiological and, geographical adaptations in animal and plant varieties., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Plant Growth and Development, 239, , 15, Plant Growth and, Development, Every living organism shows growth, which can either be in size or in, number. Hence, we can say that the growth is a characteristic feature, of all living forms of life., , Growth, It can be defined as ‘an irreversible permanent increase in size of an, organ or its part or even a cell’. It is accomplished by metabolic, processes that utilise energy obtained by nutrition. The development, is actually the sum of two processes, i.e., growth and differentiation., During growth, anabolic processes exceed catabolic processes or growth, is final end product of successful metabolism. Characteristically, the, growth is intrinsic in living beings., , Types of Growth, The growth in an organism can be divided on the basis of various, criteria. These growths can be understood through following flow chart, Growth in Plants, On the basis of, sequence of growth, • Primary growth, The division is at, the root and, shoot apex., • Secondary growth, The growth is in, diameter because, of cambium., , On the basis of, continuity of growth, • Unlimited growth, The growth of root and, stem in length in plants., • Limited growth, The growth of leaves,, fruit and flower after, obtaining certain size., , On the basis of, growing plant organ (morphogenesis), • Vegetative growth, The growth of, vegetative parts, like leaves,, stem and roots., • Reproductive growth, The growth of flower,, fruits and other, reproductive parts of, plants., , www.aiimsneetshortnotes.com
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240, , Telegram @neetquestionpaper, , Handbook of Biology, , Types of Growth Curves, By plotting the size or weight of an organism against time, the growth, curve can be obtained. On the basis of their shapes, these curves can, be — J-shaped curve and S-shaped curve. Through these curves,, the pattern of growth in an organism can be traced out., Biotic, Environmental Carrying, potential resistance, capacity, , Population, J- shaped curve, It is also known as, geometric growth curve., In this type of growth,, the progeny retains the, 0, ability to divide and, continues to do so., Mostly shown by unicellular, organisms algae and insects., , S- shaped curve, It is also known as sigmoid, growth curve., It is a typical growth curve of, most living organisms in their, natural habitat. This is divided, into four phases–lag phase, log, phase, phase of diminishing, growth and stationary phase., It is shown by higher plants and, animals., , Time, , Phases of Growth, The sigmoidal growth curve can be categorised into four distinct, phases. These growth phases and their details are discussed in the, following figure, Phase of diminishing growth, , Size/weight of the organ, , The growth gets slowed down during, this phase, e.g., growth of plant, after getting vegetative maturity., , 3, , 123, , 44, , 44, 24, 34, 0, , Log phase, , Stationary phase, The growth completely, stops. It is also known as, senescent or steady phase,, e.g., mature tissues., , The growth is very rapid. Also called as grand, phase by Sachs. The growth is constant,, e.g., fruiting regions of plants., , 123, Lag phase, , 1, , 2, 1, , Time, , The growth is slow. The growth, is continuously increasing,, e.g., the growth of root apex, and shoot apex region., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Plant Growth and Development, 241, Measurement of Growth, (i) The growth can be measured by horizontal microscope and an, instrument called auxanometer, (ii) Bose developed an instrument called crescograph for, measuring growth. It magnifies growth up to 10000 times., (iii) Growth can also be measured by calculating increase in cell, number, weight, volume and diameter., , Growth Rate, ‘The increase in growth per unit time is called as growth rate.’, With the passage of growth phases of an organism, the growth rates, show increase or decrease, which may be arithmetic or geometric., The increasing pattern of growth rates can be understood through, following description., Growth, Arithmatic Growth, In such growth pattern, after mitotic, cell division only one cell continues, to divide, while the other differentiate, and mature, e.g., constantly elongating root., , It can be represented, mathematically as, Lt = L0 +rt, , Geometric Growth, Here both the progeny cells resulted, after mitosis, continue to divide., However, with limited nutrient supply the, growth slows down and becomes stationary., , It can be represented, mathematically as, W1 = W0 ert, , Lt = Length at time ‘t’, , W1 = Final size (weight, height, number), , L0 = Length at time ‘zero’, , W0 = Initial size, , r = Growth rate, , r = Growth rate, t = Time of growth, e= Base of natural logarithms., , Here, r is the relative growth rate and also the measure of the ability of, plant to produce new plant material, often referred to as efficiency index., The quantitative comparisons between the growth of living systems can, be made by, (i) Absolute growth rate which is the measurement of total, growth per unit time., (ii) Relative growth rate which is the growth per unit time per, unit initial parameter., , www.aiimsneetshortnotes.com
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242, , Telegram @neetquestionpaper, , Handbook of Biology, , Differentiation, Dedifferentiation and Redifferentiation, The three phases of cellular growth are cell division, cell, enlargement and cell differentiation, which bring maturity to the, cells., (i) Differentiation It is the permanent qualitative change in, structure, chemistry and physiology of cell wall and protoplasm, of cells, tissues and their organs. It is the result of repression of, genes, e.g., to form a tracheary element, the cells would lose, their protoplasm., (ii) Dedifferentiation It is the process of despecialisation of, differentiated cells so that they regain the capacity to divide, and form new cells, e.g., formation of interfascicular cambium, from parenchymatous cell during secondary growth., (iii) Redifferentiation It is the structural, chemical and, physiological, specialisation, of, cells, derived, from, dedifferentiated meristematic cells, e.g., secondary phloem,, secondary cortex, etc., , Development, The sequence of events from seed germination to senescence of a plant, is called development., Death, , Cell division, , Senescence, , Meristematic, cell, , Plasmatic, growth, , Differentiation, , Expansion, (elongation), , Maturation, , Mature, cell, , Sequence of the developmental process in a plant cell, , Every organism has capacity to adapt to its environment by making, some changes among themselves in response to prevalent, environmental conditions. The capacity to change under the influence, of environmental conditions is called plasticity., , Plant Hormones/Phytohormones/, Plant Growth Regulators (PGRs), A plant hormone is an organic compound synthesised in one part of a, plant and translocated to another part, where its low concentration, causes a physiological response., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Plant Growth and Development, 243, Plant hormones can be broadly divided into two groups based on their, functions in a living plant body. One group is involved in growth, promoting activities, e.g., auxin, gibberellins and cytokinin. The, other group is involved in growth inhibiting activities, e.g., abscisic, acid, ethylene, etc., , 1. Auxins, The term ‘Auxin’ (Gk. auxein –to increase) was first used by Frits, Went. These hormones are found in meristematic regions of plant,, e.g., in coleoptile tips, in buds, etc., Chemically the auxin is Indole 3-Acetic Acid (IAA). Kogl and, Haagen-Smit (1931) isolated the active compound of molecular weight, 328 from human urine, which was called as auxin-A (Auxanotriolic, acid)., Auxins, , Naturally Occurring, •, •, •, •, •, •, , Indole Acetic Acid (IAA), Phenyl Acetic Acid (PAA), Indole Butyric Acid (IBA), Indole acetaldehyde, Indoleacetonitrile, Indole ethanol, , Synthetic Auxins, • Naphthalene Acetic Acid (NAA), • 2, 4 - Dichlorophenoxyacetic acid, • 2, 4, 5 - Trichlorophenoxy, • MCPA, • IPAC, , The natural auxin in plant is synthesised by the amino acid, tryptophan., Auxins are applied in very low concentration for good results. Higher, concentration inhibits growth and exerts toxic effects in plants., , 2. Gibberellins, These growth regulators were discovered from a fungus called, Gibberella fujikuroi that causes foolish seedling disease of rice., The first pure Gibberellic Acid (GA) was isolated by Cross (1954) and, Borrow et al. (1955) in Britain., The GAs are diterpenoid acids derived from the tetracyclic diterpenoid, hydrocarbon, ent-Kaur 16-ene having 20-carbon atoms., , 3. Cytokinins, Miller et al. (1954) isolated the third growth substance from, autoclaved herring sperm DNA. Because of its cell division activity on, tobacco pith callus, it was called as kinetin., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 244, , Handbook of Biology, , Chemically, it is a derivative of adenine with a furfuryl group at C-6, and is called as 6-furfurylaminopurine., The kinetin is formed from deoxyadenosine, a degradation product of, DNA., , 4. Abscisic Acid, It is the most recently discovered plant hormone. Okhuma et al., (1965) first isolated it from young cotton fruits. Abscisic acid is, sesquiterpene. It inhibits the action of auxin, gibberellins and, cytokinin, hence it is also known as a growth inhibitor., , 5. Ethylene, It is a ripening hormone and is produced in traces in the form of gas by, almost all tissues. The secretion of ethylene can be detected by gas, chromatography., These are synthesised by amino acid methionine as, Oxidative, , deamination, Methionine , → Methionol → Ethylene, , The plant hormones, their functions and location in plants are given in, the following table, , Plant Hormones, their Functions and Location, Hormone, , Major Function, , Location in Plant, , Auxin (IAA), , Promotion of stem elongation and, growth; formation of adventitious, roots; inhibition of leaf abscission;, promotion of cell division (with, cytokinins); inducement of ethylene, production; promotion of lateral bud, dormancy (apical dominance)., , Apical meristems; other, immature parts of plants., , Cytokinins, , Stimulation of cell division; but only, in the presence of auxin, promotion, of chloroplast development; delay of, leaf ageing; promotion of bud, formation., , Root apical meristems;, immature fruits., , Gibberellins, , Promotion of stem elongation (bolting, in cabbage), stimulate enzyme, production in germinating seeds., , Roots and shoot tips; young, leaves; seeds., , Ethylene, , Promotion of fruit ripening, control of, leaf, flower and fruit abscission., , Roots, shoot apical, meristems; leaf nodes;, ageing, flower, ripening fruits., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Plant Growth and Development, 245, Hormone, , Major Function, , Location in Plant, , Abscisic acid, , Leaves, fruits, root caps,, Inhibition of bud growth; control of, stomatal closure; some control of seed seeds., dormancy; inhibition of effects of, other hormones., , Brassinosteroids, , Overlapping function with auxins and, gibberellins., , Oligosaccharides Pathogen defence, possibly, reproductive development., , Pollen, immature seeds,, shoot, leaves., Cell walls, , Other plant hormones are, Florigen, – Flowering hormone, Vernalin, – Vernalisation hormone, Anthesins, – Flowering hormone, Calines, – Formative hormone, Traumatic acid – Wound healing hormone, , Applications of Phytohormones, (i) Stem elongation It is induced by auxin, cytokinin and, gibberellins. The process is extensively used in horticulture and, other vegetative growth. The increased plant height helps in, the production of increased biomass wherever required., The process of stem elongation is mainly accomplished by, apical dominance, which helps in proper growth of plant. In, the absence of apical dominance, the plants require physical, support for growth and development., (ii) Delay of leaf ageing and promotion of chloroplast, development It is induced by cytokinin. It helps to improve, productivity as the chloroplasts in leaf are the sites of food, production., (iii) Formation of adventitious roots This is performed by auxin., More adventitious roots help in vegetative propagation of, several plants., (iv) Promotion of lateral buds development It is induced by, hormone cytokinin. Lateral bud development has significance, in production of bushy plants, which can be equally used in, horticultural and ornamental plants., , www.aiimsneetshortnotes.com
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246, , Telegram @neetquestionpaper, , Handbook of Biology, , Seed Dormancy, The inhibition of seed germination of a normal or viable seed due to, internal factors, even when it is placed under favourable conditions, required for germination, is called seed dormancy., The dormancy period for a seed may vary from days to years, e.g., the, seeds of mangroves lack dormancy period and in most cereal grains it, is of several months long., , Causes of Seed Dormancy, Specific light, requirement, , Rudimentary, embryo, , Seed, Dormancy, , Required time for, ripening of embryo, , Impermeability of, seed coat (H2O and O2), , Hard seed coat, , Germination inhibiting, substance inside the seed, e.g., phenolic compounds., , Processes to Break Seed Dormancy, Following processes are employed to break seed dormancy, (i) Scarification Mechanical or chemical breakdown of seed, coat., (ii) Stratification Exposure of seed to well-aerated, moist, condition., (iii) Alternating temperature, high temperature., , Treatment of seed with low or, , (iv) Light Exposure of suitable (red or far-red) light to seed., (v) Pressure Exposure of high hydraulic pressure (~2000 atm) at, low temperature., (vi) Growth regulator application Kinetin and gibberellins are, used to induce germination., , Biological Significance of Seed Dormancy, (i) It allows storage of seeds in viable state for longer duration., (ii) It helps to retain seed viability in extreme conditions as well., (iii) It helps in distant spreading of seeds., (iv) It is useful in desert conditions for the postponement of seed, germination., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Plant Growth and Development, 247, Photoperiodism, Effect or requirement of relative length of day and night on flowering, is called photoperiodism., The phenomenon of photoperiodism was first discovered by Garner and, Allard. Their experimental material was ‘Maryland mamoth’ a mutant, variety of tobacco. They manipulated the photoperiod for these plants., Due to this change in flowering time was observed. Thus, they, concluded that plants differ in their requirements for day length. Most, plants flower only when they are subjected to a light phase for less or, more than a critical period. A critical period is the period of light or, darkness required by the plant to induce flowering., Depending upon the duration of photoperiod, plants have been divided, into following categories, 1. Short-day plants (SDP) Photoperiod of these plants is lesser, than the critical photoperiod. Thus, they require shorter, photoperiod in order to initiate flowering, e.g. Xanthium, (cocklebur), Chrysanthemum, Cosmos, Dahlia, rice, sugarcane,, strawberry, tobacco, Glycine max (soyabean), etc., 2. Long-day plants (LDP) These require a light period more than, the critical length. Thus, they require longer day light period for, flowering. Long night period may prevents flowering in LDP., These are sometimes also called as short-night plants,, e.g. Hyoscyamus niger (henbane), Spinacia (spinach), Beta, vulgaris (sugarbeet), wheat, oat, raddish, lettuce, etc., 3. Day neutral plants (Indeterminate plants) These plants, flower in all photoperiods. Thus, the floral initiation in them is, independent of photoperiodism. These can blossom throughout, the year, e.g. tomato, cotton, maize, sunflower, cucumber, etc., 4. Long-short day plants (L-SDP) These are short-day plants., These plants require long photoperiods for floral initiation and, short photoperiod for blossoming, e.g. Bryophyllum., 5. Short-long day plants These are long-day plants. They, require short days for floral initiation and long day for, blossoming, e.g. certain varieties of wheat (Triticum) and rye, (Secale)., , Vernalisation, It is the promotion of flowering by low temperature treatment., Spraying gibberellins is a substitute to cold treatment and biennials, can be made to flower in one year without the cold treatment., , www.aiimsneetshortnotes.com
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248, , Telegram @neetquestionpaper, , Handbook of Biology, , Vernalisation stimulus is perceived by the apical meristem. This, stimulus is believed to be a hormone called vernalin., , Conditions Necessary for Vernalisation, These are as follows, (i) Actively dividing cells, (iii) Aerobic condition, (v) Proper nourishment, , (ii) Low temperature, (iv) Water, , Mechanism of Vernalisation, G Melcher, studied vernalisation. He believed that stimulus of, vernalisation is a hormone. This hypothetical hormone was named as, ‘‘vernalin’’. The stimulus is received by the actively dividing cells of, shoot or embryo tip. In the presence of vernalin induces a physiological, change is induced in the plant which leads to flowering. It is believed, that during vernalisation, gibberellins increases in amount., , Uses of Vernalisation, These are as follows, Vernalisation shortens the vegetative period of plant. Thus, crops, can be grown earlier., It increases yield of the plant., It increases resistance to cold and diseases., l, , l, , l, , Abscission of Plant Parts, Abscission can be selectively used to control the growth of some parts, of plants. It can also help in timely harvesting of fruits and other, products and to enhance productivity., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 16, , Digestion and, Absorption, Human Digestive System, The organ system of human body responsible for breaking our complex, food into simple food particles, so that, it can be utilised by our cells. In, humans, it consists of two main parts, i.e., alimentary canal and, digestive glands., , Alimentary Canal, It is the first visceral organ to evolve. It is the tube responsible for the, conversion of intracellular mode of digestion to extracellular mode. It is, the tubular passage of mucous membrane and muscles extending, about 8.3 m from mouth to anus., The structural and functional classification of alimentary canal is as, follows, Anterior, Mouth buccal, cavity, , Zone of, ingestion, , Foregut or Stomodaeum, (ectodermal origin), , Pharynx, , Alimentary canal, , Oesophagus, , Conducting, zone, , Stomach, Intestine, , Colon, Rectum, Anus, , Digesting, zone, , Zone of, egestion, , Midgut or Mesenteron, (endodermal origin), , Hindgut or Proctodaeum, (ectodermal origin), , Posterior, , www.aiimsneetshortnotes.com
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250, , Telegram @neetquestionpaper, , Handbook of Biology, , Digestive System, Upper lip, , Uvula, , Phlitrum, (median cleft), , Teeth, , Palatopharyngeal arch, (posterior, arch), , Soft palate, (posterior part of palate), Hard palate, (ant. wall of palate), Posterior wall of, pharynx, Tongue, , Palatine tonsil, Palatoglossal arch, (anterior arch), , Parotid Salivary Gland, Largest salivary gland, open, near the upper second molar, in the buccal cavity,, zymogenic in nature, secrete, serous fluid and enzyme, salivary amylase or ptyalin., Their duct is called Stenson’s, duct., , Lower lip, , Oral Cavity, It is the opening on the ventral side and guarded by two, movable lips. It contains teeth, tongue and palate. Palate forms, the roof and tongue forms its floor., Sublingual, Smallest salivary glands, open at the floor of buccal cavity, through ducts of Rivinus., Sub Mandibular Salivary Gland, Medium-sized glands, open in buccal cavity near, the lower central incisors through Wharton’s duct. They, secrete mucus and some enzymes, also called, submaxillary glands., Liver, Largest gland containing phagocytic Kupffer cells., Divided into two lobes covered by Glisson’s capsule., Its cells, i.e., hepatocytes secetes bile, heparin, etc., Processess like glycogenesis, deamination, lymph, and blood protein synthesis, etc., occurs in it., , Gall Bladder, Pear-shaped, sac-like structure, store bile, absent is rat and, horse., , Hepatopancreatic Ampulla, It receives bile duct from the liver and main pancreatic duct, from the pancreas. Also called ampulla of vater and open, in duodenum., Jejunum, Thick walled, vascular, middle part of small intestine. Its, diameter is about 4cm., Caecum, Pouch-like structure, walls contain prominent lymphoid, tissue. It is normally intraperitoneal., Appendix, Outgrowth of caecum, vestigeal part, slightly coiled blind, tube., , Anus, Opening to exterior., , www.aiimsneetshortnotes.com
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Telegram, @neetquestionpaper, Digestion and Absorption, 251, , Portal vein, Hepatic duct, Cystic duct, Common bile duct, , Common, hepatic artery, Coeliac artery, Body and tail, of pancreas, Aorta, , Gall bladder, , Tongue, Highly muscular structure containing voluntary, muscles. Rests upon hyoid bone and attached to, the floor of buccal cavity by a connective tissue, fold called fernulum linguae. It possesses taste, buds. It helps in tasting the food, process of, speech, etc., Radix linguae, , Interior of, duodenum, , Bitter, , Hepatopancreatic, Pancreatic duct, ampulla, Pancreas and Duodenum, , Corpus, linguae, , Sour, Salt, Sweet, , Apex linguae, , Oesophagus, Highly muscular, long, conducting tube lined by stratified squamous, epithelium. Its opening is called gullet. Its upper and lower ends are, guarded by sphincters., Stomach, J-shaped dilated sac, consists of two curvatures, 4 parts, and longitudinal folds formed of mucous membrane, (sugar). It contains chief or peptic cells, oxyntic cells and, mucous cells., Fundus, Oesophagus, , Cardiac orifice, Lesser curvature, , Body or corpus, Rugae, Greater curvature, Pyloric antrum, Pyloric sphincter, , Duodenum, Pancreas, Soft, lobulated gland, both endocrine and exocrine, contains, alpha, beta, delta cells and pancreatic polypeptide cells., , Duodenum, C-shaped structure containing foliate villi. It mainly absorbs, iron, Brunner’s glands are present in it., Colon, It has 3 longitudinal bands called taeniae coli and small, pouches called haustra. It is divided into 4 regions, ascending, transverse, descending and sigmoid., lleum, Thin-walled, longest part of small intestine, contains, clustered lymphatic nodules in groups called Payer’s, patches which produce lymphocytes., Rectum, Terminal part of large intestine and digestive tract. Composed of, two parts, i.e., pelvic part containing ampulla of rectum and, perineal part containing anal canal., , www.aiimsneetshortnotes.com
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252, , Telegram @neetquestionpaper, , Handbook of Biology, , Rest of the components of digestive system are discussed below, , Zygomatic Glands, These are the fourth type of major salivary gland (rest 3 are parotid,, submadibular and sublingual). These are also the compound racemose, gland and pour their secretion into the mouth. These are not seen in, humans and rabbit. These are present below the eyes in dogs and cats, and hence called infraorbital glands., , Ebner’s Glands, These are zymogenic or enzyme secreting accessory glands. These, secrete minute quantities of salivary lipase. They are found in the, mucous membrane of lips (labial), cheeks (buccal), tongue (lingual) and, palates (palatine)., Mucus secreting minor or accessory glands are Unicellular goblet, cells, Nuhn’s glands and Weber's glands., , Tonsils, The lymphoid tissue of pharynx and oral cavity is seen as lymph nodes, called tonsils. Within the pharynx, tonsils are arranged in the form of a, ring Waldeyer’s ring from top to bottom. This ring consists of following, tonsils, (i) Lingual tonsils Irregular masses of lymphoid tissue near the, basal part of the tongue., (ii) Palatine or faucial tonsils These are present as two masses, in the lateral walls of oropharynx., (iii) Tubal tonsils These are present near the opening of, eustachian tube as a collection of lymphoid tissue., (iv) Nasopharyngeal tonsils These are present in the porterior, wall of nasopharynx. These tonsils may get enlarged in children, and cause an obstruction in normal breathing. This condition is, called adenoids., , Circopharyngeal Sphincter, It is the upper sphincter of oesophagus, which prevents the air passing, into the oesophagus during inspiration and expiration of oesophageal, content., , Cardiac Sphincter, It is the lower sphincter of oesophagus, which prevents the reflux of, acidic contents of gastric juice into the oesophagus., , www.aiimsneetshortnotes.com
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Telegram, @neetquestionpaper, Digestion and Absorption, 253, Valves of Kerkring, These are the circular folds of the mucous membrane present along the, entire small intestine. These are more prominent in the jejunum and, increase the absorptive surface area considerably. These are also called, plicae circulares., These contain villi over their exposed surface. A single villus on the, other hand contains brush bordered cells or microvilli over it, thus, increasing the absorptive surface area many folds., Epithelial cell, , Lacteal, , Villi, Mesenterium, , Muscularis, , Plicae, circulares, , Microvilli, , Mucus, Producing cell, , Submucosa, , Arteriole, Venule, , Valves of kerkring, , Serosa, , Vilum, , Villi, , Valves of kerking showing arrangement of villi and microvilli, , Dentition, Dentition pertains to the development of teeth and their arrangement, in the mouth. It accounts the characteristic arrangement, kind and, number of teeth in a given species at a given age., Depending upon the appearance of teeth, dentition is of two types, (a) Homodont dentition All the teeth in the jaw are alike, e.g., alligator., (b) Heterodont dentition Teeth differ in general appearance, throughout the mouth, e.g., human., A tooth with its structure looks like, Dentine, Hard, ivory-like substance, which lines the pulp cavity., Secreted by odontoblast, cells. It grows throughout, the life and shows, incremental lines of, Von Ebner., Root Canal, Narrow extensions of, the pulp cavity in the, root region., Apical Foramen, Opening of root canal,, does not contain cells., , Enamel, Hardest substance of human body,, secreted by ameloblast cells., It covers the dentine in the crown., Pulp Cavity, In the centre of the tooth; containing, mass of cells, blood vessels,, lymph vessels and nerves for nourishment, of teeth., Cement, Formed of cementum, bone-like structure, having cellular and acellular regions., Its cells are cementocytes. It increases, irregularly with age and form cemental annuli., , Internal structure of tooth, , www.aiimsneetshortnotes.com
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254, , Telegram @neetquestionpaper, , Handbook of Biology, , Few important terms related to teeth structure are given below, , Peridontal Ligament, It is a layer of thick collagen fibres, which helps in the fixation of teeth, within the sockets. These collagen fibres are called Sharpey’s fibres., , Closed Pulp Cavities, This condition is seen in humans where apical foramen closes after the, teeth is fully grown and no cell type is present in this region., , Open or Rootless Pulp, This condition can be seen in rabbit, rat, etc., where apical foramen of, some teeth like incisors, contains a group of ameloblast cells. Such, teeth grow throughout life, but their size remains constant., , Different Classes of Teeth, On the basis of their persistance, teeth are of two types, (i) Deciduous teeth These are temporary or milk teeth which, erupt in early stages of life. These have thinner layers of enamel, and dentine. These do not possess premolars and number of, molars present is two. These are 20 in number in humans and, soon replaced by permanent teeth., (ii) Permanent teeth These are stronger than milk teeth and, persist for a longer period. They possess premolars and three, molars., However, on the basis of attachment and appearance the teeth, may be, Monophyodont, , Acrodont, , Appears once in a lifetime,, e.g., 3rd molar and all, premolars of humans., , Attached to the, crest of bone, e.g.,, snake., , Pleurodont, Attached to the, medial side of bone,, e.g., lizard., , On the basis, of their, attachment, , Types of, Teeth, , On the basis, of their, appearance, , Diphyodont, Appears twice in lifetime,, e.g., incisors, canines,, first and second molars, of humans., , Polyphyodont, , Thecodont, Attached to the, bony socket, e.g., alligator., , Appears many times in, lifetime, e.g., in most lower, vertebrates., , www.aiimsneetshortnotes.com
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Telegram, @neetquestionpaper, Digestion and Absorption, 255, Teeth in Mammals, On the basis of their position in mouth, , Posterior Teeth, , Anterior Teeth, Found anteriorly in the buccal, cavity., , Incisors, , Canines, , Used for cutting, or clipping., , Used for holding, or tearing or, puncturing., , Found posteriorly in the, buccal cavity. Also, called cheek teeth., , Premolars, , Molars, , Used for crushing or, grinding food., , Molars, On the basis of length of crown and root, the molars can be of two types, (i) Hypsodont Teeth are long, crown with short roots, e.g., horses., (ii) Brachydont Teeth are short, crown with deep roots, e.g., humans., , Cusps, Cheek or molariform teeth have specialised medial depressions over, their crowns known as cusps., According to the food and feeding habits, the cheek teeth are of various, types depending upon the shape of cusps., Types of molars on the basis of shape of cusp, l, Secodont They have pointed cusp margins forming sharp cutting, crowns, e.g., carnivorous animals., l, Bunodont They have small, separate and rounded cusp margins for, grinding, e.g., man, pigs, monkeys., l, Lophodont They have multicuspid condition with cusp margins are, irregularly drawn as ridges, e.g., horses, rhinoceros, elephant., l, Selenodont They have multicuspid condition with cusp margins, arranged in the form of concentric rings to form ridges, e.g., cattles,, camels, deer, etc., , Dental Formula, The number and kinds of teeth in mammals are represented by an, equation called dental formula. Since, two halves of each jaw are, identical hence, the teeth of only one side are recorded., Dental formula is represented as, ICPm M, ICPm M, where, I = Incisors, C = Canines, Pm= Premolar, M = Molar, Total number of teeth = Number of teeth in dental formula × 2, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 256, , Handbook of Biology, , Dental Formula of Some Animals, Dental, Formula, , Animals, , Dental, Formula, , Pig and, Mole, , 3143, × 2 = 44, 3143, , Cow, Sheep, and Goat, , 0033, × 2 = 32, 3133, , Opossum, , 5134, × 2 = 50, 4134, , Cat, , 3131, × 2 = 30, 3121, , Dog, , 3142, × 2 = 42, 3143, , Rabbit, , 2033, × 2 = 28, 1023, , Animals, , Lemur, Kangaroo, Man, , 2133, × 2 = 36, 2133, 3124, × 2 = 34, 1024, 2123, × 2 = 32, 2123, , Squirrel, Rat, Elephant, , 1023, × 2 = 22, 1013, 1003, × 2 = 16, 1003, 1003, × 2 = 14, 0003, , Digestive Glands, They include salivary glands, gastric glands (containing chief cells,, oxyntic cells and mucous cells), liver, pancreas (containing alpha cells,, beta cells, delta cells and pancreatic polypeptides) and intestinal, glands (crypts of Lieberkuhn and Brunner’s gland). Salivary glands, and liver have already been discussed earlier in this chapter., The other glands are, , 1. Pancreatic Glands, These consist of two parts, i.e., exocrine part and endocrine part., (i) Exocrine part This part consists of rounded lobules (acini), that secrete an alkaline pancreatic juice with pH 8.4. It contains, sodium bicarbonate and 3 proenzymes namely trypsinogen,, chymotrypsinogen and procarboxypeptidase. It also contains, some enzymes such as lipase, elastase, α-amylase, DNase,, RNase, etc. The pancreatic juice helps in the digestion of starch,, proteins, fats and nucleic acids., (ii) Endocrine part This part consists of groups of Islets of, Langerhans. It is most numerous in the tail of the pancreas., They consist of following types of cells, (a) Alpha (α) cells Most numerous towards the periphery of, the Islet and constitute about 15% of the Islet of Langerhans., They produce glucagon hormone., (b) Beta (β) cells Most numerous towards the middle of the, Islet and constitute 65% of it. They produce insulin hormone., , www.aiimsneetshortnotes.com
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Telegram, @neetquestionpaper, Digestion and Absorption, 257, (c) Delta (δ) cells They are found towards the periphery of, Islet and constitute 5% of it. They secrete somatostatin, hormone., (d) Pancreatic Polypeptide (PP) cells They constitute, about 15% of the Islet of Langerhans and secrete pancreatic, polypeptides, which inhibit the release of pancreatic juice., These are also called F-cells., , 2. Gastric Glands, They are microscopic, tubular glands formed by the epithelium of the, stomach. They contain chief cells, oxyntic cells, mucous cells and, endocrine cells (G cells and Argentaffin cells)., , 3. Intestinal Glands, They are formed by the surface epithelium of small intestine. These, are of two types, i.e., crypts of Lieberkuhn and Brunner’s gland., Crypts of Lieberkuhn consists of Paneth cells and Argentaffin cells, at its base., Oxyntic Cells (Parietal cells), Large and most numerous on the side walls, of the gastric glands, against the, basement membrane. They secrete HCl and, Castle intrinsic factor. They stain strongly with, eosin., , Chief Cells, Also called peptic cells or zymogenic cells as, they secrete digestive enzymes as proenzymes, or zymogens, pepsinogen and prorennin., They also produce gastric amylase and lipase., They are basal in location., , Mucous Neck Cells, They are present throughout the epithelium, and secrete mucus. Their secretions make, the gastric juices acidic (pH 1.5-2.5)., , Argentaffin Cell, These endocrine cells produce serotonin,, somatostatin and histamine., , Gastrin (G) Cells, These endocrine cells are present in the pyloric, region and secrete and store gastrin hormone., , Gastric glands, , www.aiimsneetshortnotes.com
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258, , Telegram @neetquestionpaper, , Handbook of Biology, , Villi, Finger-like projections of the mucosa, in small intestine. They are absent over, Payer’s patches. They are covered with, epithelium and contains a lymph capillary, and blood capillaries. They increases the, surface area of small intestine., , Crypts of Lieberkuhn, Tubular structures, occur throughout small intestine, between villi. They possess goblet cells (mucous), and enterocytes (secrete water and electrolytes)., , Argentaffin Cells, They synthesise secretin hormone and, 5-hydroxytryptamine., , Paneth Cells, They are rich in zinc and contain acidophilic granules., They are capable of phagocytosis and secrete lysozyme., Found in duodenum., , Brunner’s Gland, They secrete little enzyme and mucus. The mucus, protects the duodenal wall from getting digested., , Intestinal glands, , Physiology of Digestion, The process in which large macromolecules of food are broken up into, smaller usable molecules with the help of enzymes is called digestion., The process or physiology of digestion begins with the following, processes, (i) Mastication It is process of biting and grinding the food in mouth, with the help of teeth so as to make it soft enough to swallow., (ii) Deglutition It is the process of swallowing, i.e., the collection of food, or bolus is pushed inward through the pharynx into the oesophagus., Swallowing is controlled by swallowing centre located in the medulla, oblongata and lower pons Varolii of the brain., (iii) Peristalsis It is wave of contraction and relaxation produced by, the involuntary contraction of circular muscles in the oesophagus, and simultaneous contraction of longitudinal muscles., , Digestive Enzymes, These are present in digestive juices and secreted by various, components of alimentary canal. Depending upon their functional site,, they are categorised as exo and endoenzymes., (i) Exoenzymes They require a terminus for their functional, ability, i.e., cut the substrate from its end., (ii) Endoenzymes They do not require any stimulus for their, functioning, i.e., cut the substrate interstitially., , www.aiimsneetshortnotes.com
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Telegram, @neetquestionpaper, Digestion and Absorption, 261, Digestive Hormones, These hormones are involved in the regulation of digestive secretions., , Gastrointestinal Hormones, Hormone, , Source, , Target Organ, , Action, , Gastrin, , Pyloric region of, stomach, , Stomach, , Stimulates gastric glands to, secrete and release the gastric, juice. It also stimulates gastric, mobility and HCl secretion., , Enterogastrone, (Gastric, Inhibitory, Peptide–GIP), Secretin first, hormone, discovered by, scientists, , Duodenum, epithelium, , Stomach, , Inhibits gastric secretion and, motility (slows gastric, contraction)., , Duodenum, (epithelium), , Pancreas, liver, and stomach, , Releases bicarbonates in the, pancreatic juice. Increases, secretion of bile. Decreases, gastric secretion and motality., , Cholecystokinin- Small intestine, Pancreozymin, (entire epithelium), (CCK-Pz), , Gall bladder and, pancreas, , Contracts the gall bladder to, release bile. Stimulates, pancreas to secrete and, release digestive enzymes in, the pancreatic juice., , Duocrinin, , Duodenum, (epithelium), , Duodenum, , Stimulates the Brunner’s glands, to release mucus and enzymes, into the intestinal juice., , Enterocrinin, , Small intestine, (entire epithelium), , Small intestine, , Stimulates the crypts of, Lieberkuhn to release enzymes, into the intestinal juice., , Vasoactive, Intestinal, Peptide (VIP), Villikinin, , Small intestine, (entire epithelium), , Small intestine, and stomach, , Small intestine, (entire epithelium), Delta cells of lsets, of Langerhans of, pancreas., , Small intestine, , Dilates peripheral blood, vessels of gut. Inhibits gastric, acid secretion., Accelerates movements of, villi., Inhibits the secretion of, glucagon by alpha cells and, insulin by beta cells. It also, inhibits absorption of nutrients, from the gastrointestinal tract., Supresses the release of, hormones from the digestive, tract., Inhibits the release of, pancreatic juice from the, pancreas., , Somatostatin, (SS), , Pancreatic, Polypeptide, (PP), , Pancreas and, gastrointestinal, tract, , Argentaffin cells of Gastrointestinal, gastric and, tract, intestinal glands, Pancreatic, Pancreas, polypeptide cells of, Islet of Langerhans., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 262, , Handbook of Biology, , Neutralises HCl, thus, imparting alkalinity to, chyme so that, intestinal, enzymes can act upon it., , Removal of waste, products of blood, like toxins, excess, cholesterol, bilirubin,, etc., , Functions, of, Bile, , Converts chylomicrons of, lipids to micelles thus,, helps in its absorption., , Emulsification of fats so that,, lipases can easily act upon the, lipids of food., l, , Bile is alkaline in man, but in cats and dogs, it is acidic in nature., , Absorption of Nutrients, Absorption of, Amino Acids, Protein, Lumen of, small, intestine Amino acids, , Absorption of, Fatty Acids, , Absorption of, Monosaccharides, , Bile salts, , Carbohydrate, , +, , Monosaccharides, , Fat globules, (triglycerides), , Emulsified, droplets, Free fatty acids, (monoglycerides), , Epithelial, cells of, small, intestine, , Microvilli, Smooth, Endoplasmic, reticulum, Chylomicrons, Lymphatic, capilary, (lacteal), , Blood, capillary, Absorbed by active, transport coupled, with active sodium, transport., Absorbed in the, blood capillaries., , Absorbed either by, active transport, (glucose and, galactose or facilitated, diffusion fructose)., Absorbed in the, blood capillaries., , Absorbed in a simple, diffusion., , Absorbed in the, lymph capillaries, (lacteals)., , Micelles These are the small, spherical, water soluble molecules., The products of fat digestion are incorporated into them with the help, of bile salts and phospholipids. Hence, the fat molecules are absorbed, into the intestinal cells in the form of micelles and reach directly to, lymph in lymph vessels (lacteals)., , www.aiimsneetshortnotes.com
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Telegram, @neetquestionpaper, Digestion and Absorption, 263, Chylomicrons These are the products of fat digestion, which are, used for synthesising new fats. These are released by the intestinal, cells into the lymph, in the form of droplets. Hence, the synthesised, fats are liberated from the intestinal cells in the form of, chylomicrons., , Absorption in Different Parts of Digestive System, (i) Oral Cavity Certain drugs, alcohol, etc., (ii) Stomach Water, alcohol, some salts, drugs like aspirin, simple, sugars, etc., (iii) Small Intestine Principal organ of absorption, absorb glucose,, fructose, fatty acids, glycerol, amino acids, etc., (iv) Large Intestine Water, some minerals, drugs, products of, bacterial digestion (amino acids + vitamin-B complex +, vitamin-K), etc., l, , l, , l, , Chyle The lacteals after absorption of lipids contain white-coloured, liquid inside them known as chyle., Assimilation The process of utilisation of the absorbed substances, that finally reach the tissues is called assimilation. The tissues, further perform various metabolic activities like storage, synthesis,, breakdown, transport, etc., Egestion The digestive wastes, solidified into coherent faeces in the, rectum initiate a neural reflex causing an urge or desire for its, removal. The process of removal or expulsion of faeces to the outside, through the anal opening is called egestion. It is a voluntary, process carried out by a mass peristaltic movement., , Disorders of Digestive System, Deficiency Diseases, They include Protein Energy Malnutrition (PEM) and disorders due to, the deficiency of vitamins, iodine, etc., PEM is of two types, i.e., kwashiorkor and marasmus., Deficient Nutrient, , Name of Deficiency, , Protein (PEM), , Kwashiorkor (usually, observed in children, in the age group of, 1-5 years), Marasmus (it usually, affects infants below, age of one year), , Protein and calorie, (PEM), , Deficiency Symptoms, Thin limbs, retarded growth of body, and brain, swelling of legs due to, retention of water (oedema), reddish, hair, pot belly and diarrhoea., Impaired growth and replacement of, tissue proteins, thin limbs and prominent, ribs (very less fat in the body), dry,, wrinkled and thin skin, diarrhoea., , www.aiimsneetshortnotes.com
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264, , Telegram @neetquestionpaper, , Handbook of Biology, , Deficient Nutrient, , Name of Deficiency, , Vitamin-A, Vitamin-D, , Nyctalopia (night, blindness), Rickets, , Vitamin-E, , Macrocytic anaemia, , Vitamin-K, Vitamin-B1 (thiamine), , Hypoprothrombinemia, Beri-beri, , Vitamin-B2 (riboflavin, or vitamin-G), Vitamin-B3 (niacin), , Dermatitis, , Vitamin-B5, Vitamin-B7 (vitamin-H), , Achromotrichia, Acne vulgaris, , Vitamin-B10 (vitaminM or folic acid), Vitamin-B12, , Sprue, , Vitamin-C, (ascorbic acid), , Pellagra, , Pernicious anaemia, Scurvy, , Deficiency Symptoms, Difficulty to see in night due to the, deficiency of retinol., Pigeon breast, bow legs, knock knee due, to low calcification of developing bones., Increased fragility and haemolysis of, RBCs., Deficiency of prothrombin in blood., Retarded growth, degeneration of bones, and muscles., Rough, dry and scaly skin., 3D disease as its symptoms include, dermatitis, diarrhoea and dementia., Premature greying of hairs., Appearance of pimples and boils in, young people., Ulceration of mouth, diarrhoea, etc., Large, oval and fragile RBC formation, in bone marrow., Swelling and bleeding of gums., , Vomiting, Ejection of stomach content through the mouth. This reflex action is, controlled by the vomiting centre located in the medulla oblongata., , Ulcerative Colitis, This inflammatory disease affects the large intestine, diarrhoea occurs, when waste products move through the large intestine quickly and, constipation occurs when this movement is too slow., , Constipation, It is infrequent or difficult defecation caused by decreased motility of, the intestines. Due to the prolonged collection of faeces in the colon,, excessive water absorption occurs and faeces become dry and hard., Due to this, their egestion becomes difficult., , Cirrhosis, It is the scarring of the liver due to the loss of liver cells. Alcohol and, viral hepatitis-B and C are the common causes of cirrhosis. It may, cause weakness, loss of appetite, jaundice, etc. Jaundice is, characterised by yellowish colouration of the sclerae, skin and mucous, membrane due to the accumulation of yellow compound called, bilirubin., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 17, Breathing and, Exchange of Gases, Respiration, It is the oxidation reaction process in cellular metabolism that involves, the sequential degradation of food substances and generation of, energy., Based on the mode of oxidation of nutrients respiration is of following, two types, 1. Aerobic respiration It occurs when the cells utilise molecular, oxygen for oxidising nutrient. It occurs in the mitochondria of, the cells. It produces a lot of ATP per glucose molecule. It is done, under normal circumstances by an animal, when heart rate and, breathing rates are normal., 2. Anaerobic respiration It occurs, when nutrients are oxidised, without using molecular oxygen. It is also called fermentation., It occurs in the cytoplasm of the cells. It produces less ATP per, glucose molecule. It is done during oxygen deficient situations,, i.e. like the first 1-2 minutes of exercise., , Human Respiratory System, The special features of mammalian respiratory system are presence of, a nose, elongation of nasal passage and its complete separation from, buccal passage through palate, long windpipe due to the presence of, well-defined neck, spongy and solid lungs., , www.aiimsneetshortnotes.com
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266, , Telegram @neetquestionpaper, , Handbook of Biology, , External Nose, These are paired openings that open into nasal cavities. The portion, inside nose is called vestibule which contains mucous lining and hair, epithelium., Epiglottis, Nasal Cavities, External nostrils open into 2 nasal, cavities which are separated, from each other by a thin,, cartilaginous medial vertical, partition called nasal septum., , Hyoid bone, Thyrohyoid, membrane, Thyrohyoid, ligament, Thyroid, cartilage, Cricothyroid, ligament, Cricoid, cartilage, Trachea, (b), , Larynx, It is the uppermost portion of trachea made up of nine cartilages in, humans. Its opening is glottis, which is covered by cartilaginous, epiglottis. It is called as voice box and is more prominent in man, (Adam’s apple)., , Cut end of ribs, , Right Lung, It has 3 lobes and 2 fissures. It is, broader, larger and heavier than the left, lung., , Superior Lobe, Divided by, horizontal fissure, Middle Lobe, Divided by, oblique fissure, Inferior Lobe, , Diaphragm, It is a muscular partition that separates the, abdominal and thoracic cavities., Mediastinum, Partition between the two lungs, includes the pleura of, both sides. Contains heart, oesophagus, etc., , (a) Respiratory system in humans (b) A magnified larynx, , www.aiimsneetshortnotes.com, , (a)
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Telegram @neetquestionpaper, Breathing and Exchange of Gases, 267, , Pharynx, It provides the passage to both air and food. It comprises nasopharynx,, oropharynx and laryngopharynx (hypopharynx)., , Trachea, Air conducting tube with non-collapsible walls due to the presence of, cartilaginous C-shaped, incomplete rings. Their number is 16-17 in, humans. It enters into the lungs after their first branching. It helps in, the conduction of air as it is lined by pseudostratified ciliated, columnar epithelium bearing mucous glands., , Superior Lobe, Divided by, horizontal fissure, Cardiac Notch, (accommodates, heart), , Pleurae, Two membranes that cover the lungs., These membranes enclose a pleural cavity, containing pleural fluid., , Left Lung, Smaller, lighter and narrower than right lung., Possesses two lobes and a cardiac notch., Trachea, Left principal, (primary), bronchus, , Inferior Lobe, , Lobar, (secondary), bronchi, Segmental, (tertiary), bronchus, , Alveoli, Basic functional unit of lungs, approx 300, million in number in humans, specialised, air-filled sacs which are richly supplied, with blood capillaries., , Leading after, several, successive, divisions to, Terminal, bronchus, Lobular, bronchiole, Terminal, bronchiole, , Bronchus, Trachea enter into lungs after their, branching into bronchus. They are further, divided into bronchioles (lobular, terminal, and respiratory) which further ends into, alveolus., , Respiratory, bronchiole, Alveolar duct, Atrium, Alveolar sac, Alveolus, Alveolus (in sections), (c), , (c) A magnified bronchus, , www.aiimsneetshortnotes.com, , Respiratory cum conducting zone Conducting zone only, , Parietal Pleura, Outer membrane, Pleural Cavity, Contains pleural fluid, Visceral Pleura, Inner membrane
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268, , Telegram @neetquestionpaper, , Handbook of Biology, , Respiration is carried out in different forms with the help of specialised, gaseous exchange devices, which are of two types, (i) Diffusion devices Exchange of gases with environment, takes place through the process of diffusion, e.g., diffusion lungs, found in Pila (pulmonary sac), spiders (book lungs), etc., (ii) Ventilating devices Gaseous exchange structures are not in, direct contact with the environmental air. The air is taken to, the gaseous apparatus with the help of specialised tubular, network, e.g., trachea or windpipe, ventilating lungs, etc., , Lungs, These are the organs associated with the gaseous exchange. They are, also called pulmones. It is the characteristic feature of vertebrates., These can operate through diffusion (diffusion lungs of Pila, spiders,, etc.) or operate through ventilation (ventilating lungs as of, vertebrates)., Ventilating lungs are of two types, (i) +ve Pressure Lungs In this, the pressure inside the lungs is, +ve in comparison to the atmospheric pressure at the time of, inspiration. Thus, in take of air requires pumping action, e.g.,, frog (hollow lungs)., (ii) –ve Pressure Lungs In these, the pressure inside the lungs is, –ve as compared to atmospheric pressure at the time of, inspiration. Thus, intake of air is spontaneous, e.g., humans, (solid lungs)., , Breathing, It is the process of exchange of oxygen (O2) from the atmosphere with, carbon dioxide (CO2 ) produced by the cells., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Breathing and Exchange of Gases, 269, Physiology of Breathing, Breathing is associated with the inflow (inspiration) and outflow, (expiration) of air between atmosphere and the alveoli of the lungs., Contraction of, diaphragm, and external, costal muscles, , Relaxation of diaphragm, and external intercostal, muscles, , Inspiration, , Breathing, , Expiration, Contraction of, rectus abdominis, , Relaxation of rectus, abdominis, , Air entering lungs, Air expelled from lungs, , Ribs and, sternum, raised, , Volume of, thorax, increased, Lungs, expanded, , Rib cage, , Volume of, thorax, decreased, , Ribs and sternum, returned to original, position, (lowered), , Lungs return, to original, position, Diaphragm, relaxed, and arched, upwards, , Diaphragm, contracted, , (b) Expiration, , (a) Inspiration, , Sternum, Rib, Vertebral, column, Diaphragm, Position after inspiration (with definite line), Position after expiration (with dotted line), , Process of breathing in human, , Movement of fresh air into the lungs is as follows, External nares → Nasal cavities → Internal nares, Bronchi ← Trachea ← Larynx ← Glottis ← Pharynx ←, →Bronchioles → Alveolar duct → Alveolar sac → Alveoli, Movement of foul air out of the lungs occurs in reverse pathway, i.e., from, alveoli to external nares., , www.aiimsneetshortnotes.com
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270, , Telegram @neetquestionpaper, , Handbook of Biology, , Lung Volume and Capacities, Terms, , Symbols, , Vital Capacity, , Descriptions, , VC, , Maximal volume of air exhaled after forced, inspiration (includes TV, IRV and ERV)., , Tidal Volume, (500 mL), , TV, , Volume of air inhaled or exhaled during, quiet breathing., , Inspiratory Reserve Volume, (2500-3000 mL), , IRV, , Maximal air that can be inhaled after a, quiet inspiration., , Expiratory Reserve Volume, (1000-1100 mL), , ERV, , Maximal air that can be expelled out after, quiet expiration., , Residual Volume, (1100-1200 mL), , RV, , Volume of air remaining in lungs after full, expiration., , Inspiratory Capacity, (3000-3500 mL), , IC, , Maximal volume of air inspired with, maximum effort, , Expiratory capacity, (1500-1600 mL), , EC, , Maximal volume of air that can be expired, after a normal expiration., , Forced Expiratory Volume, per, time interval in seconds, , FEV, , Volume of air exhaled in a given period, during a complete forced expiration (FVC)., , Functional Residual Capacity, (2500 mL), , FRC, , Amount of air remaining in the air passages, and alveoli after normal expiration, , Total Lung Capacity, (5800-6000 mL), , TLC, , Total volume of air in lungs at the end of a, forceful inspiration., , (3500-4500 mL), , Dead Space, In lungs, the volume occupied by gas which does not participate in, gaseous exchange is called dead space. A fixed quantity of each tidal, volume goes to the dead space., Anatomical, Dead Space, , Dead, Space, , Tha portion of respiratory passage,, in which incoming, and outgoing air is completely locked., This air is not used in gaseous, exchange and can be calculated as, , Physiological or Total, Dead Space, Anatomical dead space + oxygen, in excess supplied by the body, demand + oxygen trapped in blind, alveoli (alveoli where gaseous exchange, does not take place)., No dead space is seen in the lungs of birds., , [CO2% in alveolar air – CO2% in expired air], , TV × ———————————————————, CO2% in alveolar air, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Breathing and Exchange of Gases, 271, Exchange of Gases, In the process of respiration, gaseous exchange occurs at two level,, i.e., (i) between alveoli and blood (external respiration) and (ii) between, blood and tissue cells (internal respiration)., (i) Exchange of gases between alveoli and blood., Oxygen, Alveoli, , Diffusion of gases along, the concentration gradient, , • High pO2, , • Low pO2, , Carbon Dioxide, , (104 mm Hg), , Deoxygenated Blood, , (40 mm Hg), , • Low pCO2, , • High pCO2, (45 mm Hg), , (40 mm Hg), , (ii) Exchange of gases between blood and tissue cells., Carbon Dioxide, Diffusion of gases along the, concentration gradient, , Capillary, Blood, , • High pO2, , Oxygen, , (95 mm Hg), • Low pCO2, (40 mm Hg), , Tissue Cells, , • Low pO2, (40 mm Hg), , • High pCO2, (45 mm Hg), , The whole process of gaseous exchange can be summarised as, CO2—46 mm of Hg, O2 —40 mm of Hg, CO2, , Arterial End, O2—90-100 mm of Hg, CO2—40 mm of Hg, O2 content, 19-20 mL as O2 Hb, 0.30 mL in plasma, , O2, , Alveoli of lung, , O2, , CO2, , Venous End, O2—40 mm of Hg, CO2—40 mm of Hg, O2 content, 14-15 mL as O2 Hb, 0.15 mL in plasma, CO2—40 mm of Hg, O2—100 mm of Hg, , Transport of Gases, Blood carries oxygen from the lungs to tissue cells for oxidation and, carbon dioxide from the tissue cells to the respiratory surface for, elimination., , (i) Transport of Oxygen, Oxygen enters the venous blood in the lungs and leaves the blood, stream in the tissue capillaries and goes to the tissue cells., , www.aiimsneetshortnotes.com
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272, , Telegram @neetquestionpaper, , Handbook of Biology, , Oxygen is carried in the blood in the following forms, (a) As dissolved gas Under normal conditions of temperature, and pressure, about 0.30 mL of O2 is carried in physical solution, in 100 mL of arterial blood., (b) As chemical compound Oxygen is carried in combination, with haemoglobin as oxyhaemoglobain., • High pO2; low pCO2, • Low temperature, • Low H+concentration, • Low DPG concentration, , Fe, , , , Fe — Heme — Fe + O2, , , , in tissues, , HbO2, Oxyhaemoglobin, , • High pCO2; low pO2, • High temperature, • High H+ concentration, • High DPG concentration, , Fe, Haemoglobin, , where,, , in lungs, , Fe = Iron (have strong affinity for oxygen)., DPG = Diphosphoglyceraldehyde, , O 2 -Hb Dissociation Curve, This curve is the graphical representation of per cent saturation of, haemoglobin at various partial pressure of oxygen., % saturation of haemoglobin, , 100, Arterial point, , 90, 80, 70, 60, 50, , Venous point, , 40, 30, 20, 10, 0 10 20 30 40 50 60 70 80 90 100, O2 partial pressure (mm Hg), , where,, , 1 = At room temperature with CO2., 2 = At body temperature without CO2., 3 = At body temperature + 20 mm of Hg CO2., 4 = At body temperature + 40 mm of Hg CO2., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Breathing and Exchange of Gases, 273, Following interpretations can be made from the given curve, (a) The curve is sigmoid or S-shaped under normal condition., (b) With increased CO2 levels and increased temperatures, the, curve is shifted towards right and vice versa., (c) The curve is completely sigmoid for strong electrolytes, while it, is hyperbolic for weak electrolytes., (d) The curve for foetal haemoglobin is towards the left hand side as, compared to maternal haemoglobin. It shows that foetal, haemoglobin have greater affinity for oxygen as compared to, that of mother., (e) Oxyhaemoglobin dissociation curve for myoglobin is rectangular, hyperbola with more towards left end side., (f) The partial pressure of oxygen at which 50% saturation of, haemoglobin takes place is called p50 value., p50 value ∝, l, , l, , l, , 1, Affinity of blood for O2, , Under normal body conditions, whatsoever increase occurs in partial, pressure of O2 (even upto 100 mm of Hg), the haemoglobin is never, fully saturated because of the presence of CO2 and temperature, conditions in body., The entry of CO2 in blood helps in the dissociation of, oxyhaemoglobin and to increase acidity (decreased pH) of blood, which promotes the lesser affinity of blood for oxygen (Bohr’s effect)., The entry of O2 in blood (i.e., more and more formation of, oxyhaemoglobin) is more responsible for more and more replacement, of CO2 from the venous blood., , (ii) Transport of Carbon Dioxide, Transportation of CO2 is much easier due to its high solubility in, water. CO2 is transported in three ways, As Carbamino, Compounds, CO2 binds directly with Hb to form, an unstable compound (carbamino, compounds) (CO2 HHb); 23% CO2 is, , In Dissolved State, , Transport of CO2, , Under normal temperature, and pressure, about 7% of, CO2 is carried by physical, solution., , transported in this form., , As Bicarbonate Ions, CO2 reacts with water to form carbonic, acid (H2CO3) in the presence of carbonic, anhydrase in RBC. (H2CO3) dissociates, into hydrogen and bicarbonate ions (HCO3)., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Breathing and Exchange of Gases, 275, Carotid body, Carotid sinus, Common carotid, arteries, , Each of these bodies, contains 2 types of cells, type-I (glomus cells) and, type-II (glia-like cells), , Aortic bodies, Aortic arch, , Heart, , Carotid and aortic bodies, , Carotid bodies and aortic bodies are the peripheral chemoreceptors,, whereas these located in brain are called central chemoreceptors., Peripheral, chemoreceptors, , Chemoreceptors, , Stimulated by decreased, pO2 and increased, H+ concentration, , Central, chemoreceptors, Stimulated by increased, pO2 in brain’s extracellular, fluid, , Disorders of Respiratory System, (i) Bronchitis Inflammation of the bronchi caused by irritants, such as cigarette smoke, air pollution or infection. The, inflammation results in the swelling of mucous membrane, lining of bronchi, increased mucus production and decreased, movement of mucus by cilia which impairs the ventilation process., (ii) Emphysema It results in the destruction of the alveolar walls, due to the decreased respiratory surface, which decreases, gaseous exchange. Its symptoms include shortness of breath, and enlargement of thoracic cavity. The progress of emphysema, can be slowed, but there is no cure., (iii) Asthma It is associated with the periodic episodes of, contraction of bronchial smooth muscles, which restricts the air, movement. It results from allergic responses to pollen, dust, animal dander or other substance., (iv) Pulmonary fibrosis It is an occupational lung disease. It, involves the replacement of lung tissue with fibrous connective, tissue, making the lungs less elastic and breathing more, difficult. Its common causes include the exposure to silica,, asbestos or coal dust., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 18, Body Fluids and, Circulation, Body Fluids, They are the medium of transport in the body. They may be either, intracellular or extracellular fluid. The intracellular fluid contains, large amount of potassium ions, phosphate ions and proteins., Extracellular fluid includes blood, lymph, cerebrospinal fluid, etc., , Blood, It is the most common body fluid in higher organisms, consisting of, plasma, blood corpuscles, etc. This extracellular fluid is slightly, alkaline having pH 7.4., It is composed of a watery fluid called plasma and floating bodies, called formed elements (blood cells)., , Blood Plasma, Crystallo-colloidal mixture, makes 55-60% of blood, contains 90-92% of, water and 0.9% salts, slightly alkaline, constitutes about 5% of the, body weight., Heparin, , Amino acids, , Anticoagulants, , Glucose, , Immunoglobulins, , Digested nutrients, and excretory, substances, , Lipids, Creatinine, Urea, , Components of, Blood Plasma, , Ammonia Albumin, , Defence, compounds, , Lysozyme, , Properdin, Proteins, , Prothrombin, , Globulin, Fibrinogen, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 277, Body Fluids and Circulation, Functions of Plasma Proteins, (i) Fibrinogen, globulins and albumins are the major proteins., (ii) Fibrinogen is required for blood coagulation., (iii) Globins are primarily involved in defense mechanisms of the, body., (iv) Albumins help to maintain osmotic balance., , Blood Cells, They constitute about 40-45% of the blood. They have specific gravity, of about 1.09, i.e., these are slightly heavier than the plasma., The three types of cellular elements in blood are, Blood Platelets, or, Thrombocytes, , Red Blood Cells, or, Erythrocytes, Haemoglobin containing, cells that carry oxygen in, the blood (non-nucleated, in humans)., , Blood, Cells, , Non-nucleated, discshaped fragments of bone, marrow cells, involved in, blood coagulation., , White Blood Cells, or, Leucocytes, Colourless, motile, nucleated, cells, involved in body, defense mechanism. Also, called PMNCs, i.e., Poly, Morpho Nuclear Corpuscles, , Agranulocytes, (Granules are not found, in cytoplasm), Lymphocytes, 20-25%, Large rounded, nucleus, Non-phagocytic, They produce, antibodies, , Granulocytes, (Contains granules in, their cytoplasm), , Monocytes, , Eosinophils, , Basophils, , 2-10%, Bean-shaped, nucleus, Phagocytic, They engulf, bacteria and, cellular debris, , 2-3%, Bilobed, nucleus, Non-phagocytic, Play role in, allergy and, hypersensitivity reactions, (correspond to, lysosomes), , 0.5-1%, Three-lobed, nucleus, Non-phagocytic, Contain heparin,, histamine and, serotonin, (correspond to, mast cells), , www.aiimsneetshortnotes.com, , Neutrophils, 60-65%, Multi-lobed, nucleus, Phagocytic, Correspond to, macrophages
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278, , Telegram @neetquestionpaper, , Handbook of Biology, , Major characteristics of blood cells are as follows, Characteristic, Features, , Erythrocytes, , Leucocytes, , Thrombocytes, , Number, , 4.5-5 million mm 3, of blood, , 6000-8000 mm 3 of, blood, , 1,50,000-3,50,000, mm 3 of blood, , Shape, , Biconcave and, circular, , Rounded or irregular, , Rounded or oval, disc-like bodies., , Size, , 7-8 µm in diameter, 1-2 mm thick, , 12-20 µm in diameter, , 2-3 µm in diameter, , Colour, , Red (due to the, presence of, haemoglobin), , Colourless (due to the, absence of, haemoglobin), , Colourless (due to, the absence of, haemoglobin), , Formation, , Erythropoiesis occurs, in liver and spleen, (before birth) and in, bone marrow (after, birth)., , Leucopoiesis occurs in, bone marrow, lymph, nodes, spleen, thymus,, tonsils and Peyer’s, patches., , Thrombopoiesis, occurs from very, large cells of bone, marrow,, i.e., megakaryotes., , Lifespan, , About 120 days, , Few hours to few days About 8-10 days., (granulocytes) or few, months (agranulocytes)., , B-Cells and T-Cells, Lymphocytes exist in two major groups, i. e. , B-lymphocytes and, T-lymphocytes., B-lymphocytes (B-cells) and T-lymphocytes (T-cells), B-Cells, , T-Cells, , They form a part of the humoral immune, system., , They form a part of the cell-mediated, immune system., , They are processed in the liver or bone marrow., , They are processed in the thymus gland., , They release antibodies which finally enter, the blood., , They do not release antibodies., , They produce antibodies to kill the antigens., , The whole cell directly attacks the antigens., , They defend the body against invading, bacteria/virus. They do not reach against, transplants and cancerous tissues., , They defend the body against pathogens,, but also attack the transplants and the, cancerous cells., , Blood Groups, There are more than 30 antigens on the surface of blood cells that give, rise to different blood groups. During agglutination, reaction occurs, between antigens (agglutinogens) in red blood cells and antibodies, (agglutins) in blood plasma., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Body Fluids and Circulation, 279, Two types of blood grouping are widely used all over the world namely;, ABO blood group and Rh (rhesus) blood group., , 1. ABO Blood Groups, A, B and O blood groups were reported first time by Karl, Landsteiner in human beings. ABO blood group is based on the, presence or absence of two antigens on the RBCs, i.e., A and B., , Phenotype, , Genotype, , Can, Receive, Blood, From, , Antigen on RBC Antibody, Membrane, In Plasma, , Can Donate, Blood To, , A (40%), , IA IA or IA Io, , A antigen, , Anti-B, antibodies, , A, O, , A, AB, , B (10%), , IB IB or IB Io, , B antigen, , Anti-A, antibodies, , B, O, , B, AB, , AB (4%), , IA IB, , A antigen, B antigen, , No, antibodies, , A, B, AB, O, (universal, AB, acceptor), , O (46%), , Io Io, , Anti-A and, Anti-B, antibodies, , O, , No antigen, , A, B, AB, O, (universal, donor), , I represents isoagglutinin gene possessing 3 alleles– IA , IB , IO., , 2. Rhesus (Rh) Blood Group, It was discovered by Landsteiner and Wiener in the blood of rhesus, monkey. Depending upon the presence or absence of rhesus antigen, on the surface of red blood corpuscles, individuals are categorised as, Rh positive (Rh+ ) and Rh negative (Rh− ), respectively. Rh + is dominant, to Rh − ., Rh Incompatibility During Pregnancy, It is seen when father’s blood is Rh + and mother’s blood is Rh − ., Rh + being a dominant character expresses in the foetus and causes a, serious problem., , www.aiimsneetshortnotes.com
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280, , Telegram @neetquestionpaper, , Handbook of Biology, , The first child of Rh − mother will not suffer, but Rh + blood of foetus, stimulates the formation of anti-Rh − factors in the mother’s blood., , %, , Rh+, , &, , Rh–, , +, , Rh+ foetus, , In the subsequent pregnancies with foetus,, the anti-Rh antibodies in the mother’s blood, destroy the foetal RBCs and result in, Haemolytic Diseases of the Newborn, (HDN) or erythroblastosis foetalis., , Rh Incompatibility During Blood Transfusion, The first transfusion between Rh+ and Rh− blood causes no harm,, because Rh− person develops anti Rh antibodies in his blood. But in, the second transfusion of Rh+ blood to Rh− blood, the anti Rh, antibodies in the latter’s blood destroy the RBCs of the donor., , Coagulation of Blood, Coagulation or clotting is one of the characteristic feature of blood. It is, defined as ‘conversion of normal viscous blood fluid into jelly-like mass, within 3-10 minutes after its exposure to air’., The pathways of mechanism of blood clotting are as follows, Extrinsic Pathway, , Intrinsic Pathway, Damage to the, blood vessel, , Damage to tissue, outside the vessel, , Platelets cofactors, , Plasma factors, (IV, V, VII, X), , +, , Plasma factors, (IV, V, IX, X, XI, XII), , Tissue thromboplastin, , Ca, , 2+, , and proteins, , Platelet thromboplastin, (platelet factor 3), Inactive, factor X, , Ca, , 2+, , and proteins, , Active factor X + Factor V, Vitamin-K, Prothrombinase, Inactivates, heparin, Prothrombin, Ca, , 2+, , Thrombin, , Fibrinogen, , Fibrin, Factor, XII, , Serum, , www.aiimsneetshortnotes.com, , Blood clot
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282, , Telegram @neetquestionpaper, , Handbook of Biology, , Functions of Blood, (i) Helps in transportation of respiratory gases (i.e., O2, CO 2, etc.),, hormones from endocrine glands to target organs and body, wastes from different body parts to kidney., (ii) Maintains body pH, water, ionic balance and normal body, temperature., , Lymph (Tissue Fluid), It is an interstitial mobile connective tissue comprising lymph plasma, and lymph corpuscles. It contains little O2, but lot of CO2 and metabolic, waste., Fewer blood, proteins, , WBCs are present, Platelets are, absent, , Corpuscles, RBCs are absent, , Lymph, , Plasma, , Globulin protein, , High glucose, concentration, , Infact, when blood flows from arterial end to venous end of a capillary,, most of its contents move into tissue (at the arterial end). 90% of these, constituents return back at the venous end, while remaining, 10% constitute the lymph., , Lymphoid Organs, These are the lymph secreting/accumulating organs. They include, lymph nodes, tonsils, thymus, spleen and Peyer’s patches. The spleen, is the largest lymphoid organ in the body., , Functions of Lymph, l, , l, l, , Its white blood corpuscles help in defence mechanism, tissue repair, and healing., It is an important carrier for nutrients, hormones, etc., It helps in the absorption of fats in the lacteals present in the, intestinal villi., , Circulatory System, This system is primarily concerned with the circulation of substances, through body fluids like blood and lymph., The two types of circulatory system found in animals are, 1. Open Circulatory System Blood pumped by the heart passes, through large vessels into open spaces or body cavities called, sinuses. It is found in arthropods and molluscs., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Body Fluids and Circulation, 283, 2. Closed Circulatory System Blood pumped by the heart, circulates through a closed network of blood vessels. It is found, in annelids and chrodates., The general vertebrate closed circulatory systems can be, (a) Single circuit or single circulation, (b) Double circuit (complete or incomplete) or double circulation, Single Circulations, Two-chambered heart., Single circuit circulation, i.e., heart, always receives deoxygenated, blood which passes through it, for once only, , y, , Bo d, , LV, RA LA, , 321, , 2-chambered heart, , Ventricle, , Deoxygenated, blood, , Truncus or conus arteriosus, , Auricle, Oxygenated, blood loop, Sinus, venosus Fishes, , RV, , Gills, Oxygenated blood, , Body parts, , Sinus, Venosus, , RA, Mixed, Birds and Circulatory, blood, Amphibians Body, Mammals Circuits, Mixe, and Heart, , Oxygenated blood, , LA, , Lung, , s, , Mixed blood, Deox, Lungs, ygen, CACP Conus arteriosus, d, b, a, lood, bloo, (Cavum, d loo ted, (cavum, p, pulmocutaneum), Reptiles, aorticum), Four-chambered heart., Three-chambered, heart., Sinus venosus and truncus, Sinous venosus and truncus, d, arteriosus are absent., LA, e, SV RA, at, arteriosus are well-developed., Complete double circulation,, en, yg lood Lungs Incomplete double circulation,, De, x, V, i.e., oxygenated and,, oxy, O b, g, i.e., oxygenated and, blo enat, Mixed, deoxygenated blood, od ed, deoxygenated blood gets, blood, do not get mixed and, Mixed, y, d blood, mixed in the ventricles., distributed to different, Bo, Double Circulation (Incomplete), parts separately., Double Circulation, (Complete), , Mixed, Less oxygenated, More oxygenated, blood, More deoxygenated, Less deoxygenated, Three-chambered heart., Incomplete double circulation., Sinus venosus is present, truncus, arteriosus is absent., Foramen of panizzae connects, the two main arches., Double Circulation (Incomplete), , Circulatory circuits and heart, , www.aiimsneetshortnotes.com
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284, , Telegram @neetquestionpaper, , Handbook of Biology, , Types of Heart, Heart can be classified into different types on the basis of origin of, impulse for contraction and their structure., Heart, Groups, On the basis of origin of, impulse for contraction, , Myogenic heart, (genic-genesis (origin)myo-muscle), Muscles are responsible for origin of, impulse, e.g., vertebrate., , Tubular, Muscle responsible, for impulse, generation is external,, e.g., heart of cockroach, which beats with the help, of alary muscles., , On the basis, of structure, , Neurogenic heart, Nerves are responsible, for origin of impulse, e.g., heart of cockroach, and most other invertebrates, , Pulsatile, Muscle, responsible for, impulse generation, is situated, within heart, e.g.,, heart of earthworm., , Ampullary, Ampullary heart is situated, below the appendages, like antennae, wing, etc., Ampullary heart, is found in insects., , Chambered, Chambered heart founds, in vertebrates,, e.g., fishes, amphibians,, aves, mammals., , Human Circulatory System, It constitutes the closed type of blood vascular system and lymphatic, system., (i) Blood vascular system comprises heart, blood and blood, vessels., (ii) Lymphatic system comprises lymph, lymphatic capillaries,, lymphatic vessels, lymphatic nodes and lymphatic ducts., , Human Heart, It is a hollow, fibromuscular organ of somewhat conical or pyramidal, form with upper broad part, the base and the lower narrow apex which, is slightly directed to the left., Histologically, the heart consists of three layers, (i) Pericardium Outermost smooth coelomic epithelium., (ii) Myocardium Thick muscular middle layer, composed of, cardiac muscle fibres., (iii) Endothelium Innermost layer consisting of simple squamous, epithelial cells., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 285, Body Fluids and Circulation, Left subclavian, artery, Supplies blood to, arms., , Common, carotid artery, Supplies oxygen-rich, blood to the body., , Ligamentum arteriosum, Remnant of embryonic, structure between pulmonary, trunk and aorta., , Branchiocephalic, artery, Superior vena cava, Carries deoxygenated blood, from the upper region of the, body to right atrium., , Supplies blood to, brain and head., , Left pulmonary artery, It supplies deoxygenated, blood to the right lung., , Right pulmonary artery, , Pulmonary artery trunk, , It supplies, deoxygenated, blood to the left lung., , Conveys deoxygenated blood, from right ventricle to right and, left pulmonary arteries., , Pulmonary semilunar valve, Separates right ventricle from, pulmonary aorta, one way valve., , Left pulmonary veins, ng, Openi l, of pu, y, monar, veins, , Right pulmonary veins, Bring oxygenated blood from, right lobe of lungs to left atrium., , Right atrium, Receives deoxygenated blood from body, through superior and inferior vena cava ., , Aortic arch, Branches off from the, first portion of ascending, aorta. 3 major anteriorbranchiocephalic, left, common carotid and left, subclavian arises from it,, It carries oxygenated blood., , Precaval, opening, Postcaval, opening, , Bicuspid valves, Mitral valves between left, atrium and left ventricle,, have 2 flaps, one way valve., , Found between right atrium and right, ventricle. One way valves, have 3 flaps., , Aortic semilunar valve, , Chordae tendineae, , Right ventricle, Receives deoxygenated blood, from right atrium through, tricuspid valves, walls are, thinner than left ventricle, opens, into pulmonary artery through, pulmonary valves., , Left atrium, Receives oxygenated blood from, lungs through pulmonary veins., , Opening guarded by tricuspid valves, , Fibrous chords attached to the flaps of, bicuspid and tricuspid valves on the, ventricular side, i.e., the lower chamber., , Bring oxygenated blood from, left lung to left atrium., , Ascending aorta, Receives oxygenated, blood from left ventricle, and take it to system, of arteries., , Decending aorta, , Separates left ventricle from, aortic arch. As ventricle, contracts, it allows oxygenated, blood to flow throughout the, body, one way valve., , Left ventricle, Receives oxygenated blood, from left atrium through mitral, valves, thicker than the right, ventricle, open into aorta, through aortic valves., , Carries oxygenated blood, from left ventricle to, thorax and abdomen, Papillary muscle, region of the body., Inferior vena cava, Muscle tissue which, Brings deoxygenated blood, project inwards from, from the lower part of the body, the walls of ventricle,, to right atrium., they give rise to chordae, tendineae., , Internal human heart, , Other components of heart which are not shown in the figure are, described below, (i) Grooves (Sulci) These are partitions that separate the, various components of the heart. These are, (a) Interatrial groove or sulcus The left and right atria are, separated by this shallow, vertical groove., (b) Atrioventricular sulcus, ventricle., , It divides the atria from the, , www.aiimsneetshortnotes.com
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286, , Telegram @neetquestionpaper, , Handbook of Biology, , (c) Interventricular sulcus It divides the right and the left, ventricles., (d) Coronary sulcus, , It separates atria and ventricles., , (ii) Coronary sinus It delivers deoxygenated blood into the right, atrium through coronary veins. Its opening is guarded by, coronary valves or thebesian valve., (iii) Fossa ovalis It is an oval depression present in the, interauricular septum within the right auricle. This depression, is present as an oval foramen in embryo and known as foramen, ovale. This foramen ovale helps in the communication of blood, from right auricle to left auricle in embryo., Conducting System of Heart, The human heart has an intrinsic system whereby the cardiac muscles, are automatically stimulated to contract without the need of a nerve, supply from the brain. But this system can be acclerated or depressed, by nerve impulses initiated in the brain and by circulating chemicals, (hormones)., The conducting system possesses the following components, Superior Vana Cava, , Purkinje Fibres, These are the fine fibres of, AV bundle in the, ventricular myocardium., They convey impulse of, contraction from AV node, to the apex to myocardium, and bring ventricular, contraction., , SA Node, Sinoatrial node is a small, mass of specialised cells in, the wall of the right atrium, near the opening of superior, vena cava., It is called pacemaker of, the heart because it initiates, the impulses more rapidly, than other neuromuscular, cells., , Atrioventricular (AV), Bundle (bundle of His), , AV Node, Atrioventricular node is a small mass, of self-excitatory muscular tissue, situated in the wall of atrial septum, near the atrioventricular valves. It is, stimulated by impulses that sweep, over atrial myocardium. It is capable of, initiating own impulses, but at slower, rate. It is called pacesetter of heart., , Mass of specialised fibres, originating from AV node. It, separates atria and ventricle, and at the upper end of, ventricular septum, it is, divided into left and right, bundle branches., , Components of heart’s conducting system, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Body Fluids and Circulation, 287, Cardiac Cycle, It is the event during which one heartbeat or one cycle of contraction, and relaxation of cardiac muscle occurs., The time of cardiac cycle is in reverse ratio of the rate of heartbeat. In, man, the heart rate is about 72 times/min, therefore time of a cardiac, cycle is 60/72 = 0.8 sec approx., Atria, Time, Taken, , Ventricle, , Systole, , Diastole, , Systole, , Diastole, , 0.1 sec, , 0.7 sec, , 0.3 sec, , 0.5 sec, , It is the last filling phase during, which ventricle filling is very, slow. With the completion of this, phase, ventricle diastole ends, and atrial systole commense, again., , L, , Di, a, , t Ra, p, 0.1 id Filln, sec, g, E, , nt., co, m. sec, Iso .05, 0, , st, as, 0. is (, 16 sl, 7 ow, se fi, c. llin, g, , ), , Las, , O, , T, , Atria contract after, stimulating by SA node., Bicuspid and tricuspid valves,, Atrioventricular valves (AVV), are open and blood is forced, into ventricles., , A, Systrial, tole, , E, , L, ling, id Fil, Rap, c, First 0.113 se, , S, I, , A, T, S, , I, , se, , o, S.L und, .V., Clo, , ds, 2n, , Ventricles rel, ax,, ventricular pre intra, ssure, falls below, that of atria, and AV valve, s open., , A, D, , Proto, Diasto, lic, Period, 0.04, sec, , Iso, m, 0. et, 08 . R, se ela, c x., , en, Op, , O, , It is, bet the in, t, w, beg een t erval, and ining he, o, f, c, losu dias, lun, a, pro r valv re of s tole, e, d, e, hea uces s whic mirt s, s, oun econ h, d, d., , The outflow of, blood is very, rapid out of the, ventricles in the, first phase of, ejection period,, , n, tio, jec, dE c, ce se, du 4, Re 0.1, , V, AV, , Maximum Ejection, 0.11 sec, , D, Atrial blood, begins to flow, in ventricle., The first part, of filling, is very rapid., , Ventricles, begin to, contract due, to wave of, contraction,, stimulated by AV, node. Closure of, AVV produces first, heart sound., , in i.e.,, wn d., do erio urs, s, o, p, low on e p a., d s cti tricl ort, loo of eje ven nd a, b, o f se, ich k a, low ha wh run, utf d p ng ry t, e o con duri ona, h, e, T, s iod ulm, the per to p, the od in, blo, , Abbrevations, AVV = Atrioventricular Valve, SLV = Semilunar Valve, Isom cont. = Isometric contraction, Isom relax. = Isometric relaxation, , Cardiac cycle, , www.aiimsneetshortnotes.com
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288, , Telegram @neetquestionpaper, , Handbook of Biology, , Heart Sounds, The beating of heart produces characteristic sounds which can be, heard by placing the ear or stethoscope against the chest. The two, sounds are produced per heartbeat, i.e., ‘lubb’ and ‘dubb’., Differences between First and Second Heart Sounds, First Heart Sound, , Second Heart Sound, , It is produced by the closure of bicuspid, and tricuspid valves., , It is produced by the closure of aortic and, pulmonary semilunar valves., , It is low pitched, less loud and of long, duration., , It is higher pitched, louder and of short, duration., , It lasts for 0.15 sec., , It lasts for 0.1 sec., , Heartbeat, It is the rhythmic contraction and relaxation of the heart. Each heart, beat includes a contraction phase (systole) and a relaxation phase, (diastole) to distribute and receive blood to and from the body., Adult healthy heart beats 72 times per minute (average) to pump, approximately 5 litres of the blood., , Regulation of Heartbeat, The rate of heartbeat is regulated by two mechanism, (a) Neural regulation Medulla oblongata is the cardiac centre, which is formed of cardio-inhibitor and cardio-accelerator parts., They decrease and increase the rate of heartbeat respectively., Medulla, Oblongata, , Carotid body, Carotid sinuses, Carotid arteries, Aorta, , Sympathetic nerve, It connects cardio-accelerator, to the heart., Superior vena cava, Impulses received by, it increase the heart rate., , 123, , Vagus nerve, Connects the cardio-inhibitor, to heart and carries parasympathetic nerve fibres., Impulses, received by these, structures decrease, the heart rate., , = Motor nerve, = Sensory nerve, Heart, , Neural regulation of heartbeat, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Body Fluids and Circulation, 289, (b) Hormonal regulation Hormones secreted by the medulla, region of adrenal gland help in regulating the heartbeat., Adrenal Gland, Epinephrine, (adrenaline), , Norepinephrine, (nor-adrenaline), , +ve, , +ve, , Heartbeat, Accelerate under, normal conditions, , Accelerate at the, time of emergency, +ve, , Increases, , Increases Oxidative Metabolism, , Thyroxine, , Thyroid Gland, , Hormonal regulation of heartbeat, , Cardiac Output, It is the amount of blood pumped by heart per minute, Cardiac output = Normal heart rate of an adult per minute ×, Amount of blood pumped by heart per minute, = 72 per minute × 70 mL, = 5040 mL per minute (5 L/min)., , Electrocardiogram (ECG), It is a graphic record of the electric current produced by the excitation, of the cardiac muscles., Electrocardiograph It is the machine by which the electrocardiogram, is recorded., Waller (1887) first recorded the ECG, but Einthoven (1903), studied ECG in detail and got Nobel Prize in 1924 for the, discovery of electrocardiography. He is also considered ‘Father of, Electrocardiography’., , www.aiimsneetshortnotes.com
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290, , Telegram @neetquestionpaper, , Handbook of Biology, , A human electrocardiogram shows the following, 5 consecutive waves, i.e., P Q R S T, , 2.0, , R, , 1.5, P-R segment, Atrial Complex, , mV, , 'P', being of, atrial origin, , Ventricular Complex, , Q-T interval, , 1.0, , T, , P, 0.5, P-R interval, , U, , P, , 'QRST’, being of, ventricular origin, , Isoelectric line, , Q, S S-T segment, , 0, , QRS interval, 0, , 0.2, , 0.4, , 0.6, , 0.8, , Time in second, , Reading an ECG, There are two isoelectric periods in ECG, (a) The shorter one, between P and Q., (b) The longer one, between S and T., Waves involved in ECG are described below, (i) P-wave Represents atrial depolarisation,impulse is, originating at SA node, there is no defect of conduction., (ii) Q-wave Caused by the activity of septum. It is small, negative,, often inconspicuous deflection., (iii) R and S-wave R is the most constant and conspicuous wave, having tallest amplitude, represents first positive deflection, during ventricular depolarisation, ‘S’ is downward deflection,, constant and inconspicuous., (iv) T-wave Broad, smoothly rounded deflection, caused by the, contraction of the basal part of ventricles, represents, ventricular repolarisation., (v) U-wave This wave is often seen just after the T-wave. It is, possibly due to slow repolarisation of the intraventricular, conducting system., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Body Fluids and Circulation, 291, Significance of ECG, Significance of different intervals involved in ECG, l, R-R interval Rhythmical depolarisation of ventricles., l, P-P interval Rhythmical depolarisation of atrium., l, P-R interval Measures conduction time of the impulse from SA, node to the ventricles. It varies from 0.13-0.16 sec., l, Q-R-S interval Measures total ventricular depolarisation time. It, varies from 0.08-0.1 sec., l, Q-T interval Measures the ventricular total systolic time. It is, about 0.36 sec., l, T-P interval Measures the diastolic period of the heart., Abnormalities in ECG and their significance, (i) Inverted P-wave Indicates that SA node fails to initiate the, impulse and atrial muscles depolarised by the impulse, originating in AV node., (ii) Enlarged P-wave Enlargement of the atria., (iii) Absent Q-wave Infants suffering from congenital patency of, the septum., (iv) Abnormal T-wave Serious myocardial damage, cardiac, hypoxia., (v) Enlarged P-R interval Inflammation of atria and AV node., (vi) Repressed S-T segment Heart muscles receive insufficient, oxygen., , Blood Vascular System, It consists of a system of vessels that supply the blood throughout the, body. Oxygenated and deoxygenated blood is transported to different, body parts through different vessels namely arteries and veins,, respectively., , www.aiimsneetshortnotes.com
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292, , Telegram @neetquestionpaper, , Handbook of Biology, , The walls of artery and veins consist of 3 coats as follows, Tunica Externa, Middle coat, formed, of smooth muscle, fibres and elastic, connective tissue., , Endothelium, Formed of flat, squamous, epithelial cells., , Lumen, Innermost empty, space lined by, endothelium of, tunica interna., , Elastic Membrane, Formed of elastic, tissue of yellow fibres., , 123, , Outermost coat, formed, of connective tissues,, also called tunica, adventitia., , Tunica Media, , Tunica Interna, innermost coat, made up of,, 2 parts., , TS of artery and veins, , Arteries, , Veins, , They distribute blood from the heart to the, different parts of the body., , They collect blood from different parts of, the body and pour it into the heart., , Tunica media is thick, having more, muscle fibres., , Tunica media is thin, having fewer muscle, fibres., , Tunica interna has strong elastic, membrane and more elongated endothelial, cells., , Tunica interna has simple, elastic, membrane and elongated endothelial cells., , The walls of the arteries are thick and, muscular., , The walls of the veins are thin and, non-muscular., , Arteries are not collapsible as they have, thick walls., , Veins are collapsible because they have, thin walls., , Arteries have no valves., , Veins have valves which prevent backward, flow of blood., , The flow of the blood is fast as the blood, in them is under great pressure., , The flow of blood in veins is not so fast, because the blood in veins is under low, pressure., , Except the pulmonary arteries, all the, arteries carry oxygenated blood., , Except pulmonary veins, all the veins, carry deoxygenated blood., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Body Fluids and Circulation, 293, Some Major Arteries and Veins of Human Body, , www.aiimsneetshortnotes.com
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294, , Telegram @neetquestionpaper, , Handbook of Biology, , Portal System, It is a part of venous circulation which is present between the two, groups of capillaries, i.e., it starts in capillaries and ends in capillaries., Portal vein It is the vein that drains blood into organs other than, heart. This vein along with other small veins constitutes a portal, system., , 1. Renal Portal System, This system supplies blood from the posterior region of the body to the, kidneys by renal portal vein to remove the waste products before, sending it to the heart. It is present in fishes and amphibians, reduced, in reptiles and birds, and is absent in mammals., , 2. Hepatic Portal System, The hepatic portal system or portal venous system consists of, numerous veins and tributaries, including the hepatic portal vein., Heart, , Inferior vena cava, , Abdominal aorta, , Hepatic veins, , Hepatic artery, , Liver, , Hepatic portal, vein, Superior, mesenteric, vein, , Tributaries from, small intestine and, portions of large, intestine, stomach, and pancreas, , Splenic, vein, , Tributaries from the, portions of stomach,, pancreas and large, intestine, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Body Fluids and Circulation, 295, Significance of Hepatic Portal System, (i) Proper action of various drugs on the body by activating them, by liver before reaching to other organs., (ii) Takes most of the absorbed nutrients from digestive tract to, liver for their processing., (iii) Neutralise many toxic materials absorbed from digestive tract., (iv) Venous drainage from the pancreas and spleen., , 3. Hypophyseal Portal System, This system carries blood from the hypothalamus of the brain to the, anterior lobe of pituitary gland. It allows the endocrine communication, between the two structures., Hypophyseal artery, Hypothalamus, and hypothalamic, neurons, , Components, of Hypophyseal, Portal System, , Hypophyseal vein, , Hypothalamichypophyseal, veins, , Anterior pituitary, , Significance of Hypophyseal Portal System, (i) It allows a fast communication between pituitary gland and, hypothalamus., (ii) The fenestral structure of the hypophyseal portal system needs, only a small amount of hormones to tolerate a rapid exchange, between two structures., , Disorders of Circulatory System, (i) Angina It is also called angina pectoris means chest pain., In this disease, enough oxygen does not reach the heart muscles., The patient experiences pain in chest., (ii) Arteriosclerosis It refers to the hardening and loss of, elasticity of the arteries. In arteriosclerosis, calcium salts, precipitate with the cholesterol which forms plaques., Calcification of the plaques makes the walls of the arteries stiff, and rigid. The affected arteries lose their elasticity and their, walls may get ruptured. The blood coming out of the ruptured, walls may clot and block the blood flow which further may lead, to heart attack., , www.aiimsneetshortnotes.com
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296, , Telegram @neetquestionpaper, , Handbook of Biology, , (iii) Coronary Artery Disease (CAD) or Atherosclerotic heart, disease It is the deposition of fatty substances specially, cholesterol and triglycerides in the tunica interna and smooth, muscles of arteries. Such a deposition is called atheromatous, plaque which deforms the arterial wall. These plaques reduce, the lumen of artery which interfere with the blood flow to the, heart. This may result in heart stroke or heart attack., (iv) Fibrillation It is a condition in which the heart muscles, contract very rapidly, but in uncoordinated fashion. There are, atrial and ventricular fibrillations. Ventricular fibrillation is life, threatening unless it can be stopped by defibrillation., V4, , Ventricular fibrillation, , (v) Heart attack (Myocardial infarction) It is the death of a part of, heart muscle following cessation of blood supply to it. It is an, acute heart attack. The heart muscles suddenly get damaged by, inadequate blood supply., (vi) Heart failure It is the condition when heart does not pump, blood effectively enough to meet the need of the body. It is, sometimes called congestive heart failure because, lung, congestion is one of the main symptom of this disease., (vii) Ventricular premature beat or extra-systole The series of, ventricular premature beat or extra-systole are shown in the, figure given below. Sometimes, a portion of the myocardium, becomes irritable and ectopic beat occurs before the expected, next normal beat. This ectopic beat causes transient, interruptions of the cardiac rhythm. This type of ectopic beat, is known as ventricular extra-systole or premature beat., VPB, , II, , Ventricular premature beat, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 19, Excretory, Products and, Their Elimination, Excretion, It is the elimination of metabolic waste products from the animal body, to regulate the composition of the body fluids and tissues., Various types of metabolic waste (excretory) products in animals are, nitrogenous waste material, mineral salts, vitamins, hormones, etc., , Excretory Products, Depending upon the type of nitrogenous waste excreted, animals are of, three types, 1. Ammonotelic Ammonotelism involves the excretion of, ammonia, occurs in aquatic animals as ammonia is highly toxic, and highly soluble in water, e.g., protozoans, sponges, tadpole,, etc., 2. Ureotelic Ureotelism involves the excretion of urea, occurs in, semi-aquatic animals as urea is less toxic and less solube in, water, e.g., cartilaginous fishes, frogs, toads, mammals, etc., 3. Uricotelic Uricotelism is the excretion of uric acid, occurs in, animals living in dry conditions to conserve water in their, bodies, uric acid crystals are non-toxic and almost insoluble in, water, e.g., land crustaceans, land snails, birds, etc., , www.aiimsneetshortnotes.com
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298, , Telegram @neetquestionpaper, , Handbook of Biology, , Other excretory products in different animals include, (i) Allantoin is the oxidation product of uric acid. The name given, to this compound is because of the fact that it is excreted, through the extraembryonic membrane allantois., (ii) Hippuric acid is seen among the excretory products only when, benzoic acid is present in diet. This benzoic acid reacts with, glycine to form the hippuric acid. It is present in traces in, human urine., (iii) Amino acids are excreted in certain invertebrates like Unio,, Limnaea (molluscans) and Asterias (echinoderm). These, animals are called aminotelic and the phenomenon is called, Aminotelism., (iv) Guanine is the excretory material of spiders. The mode of, formation of guanine is not clear. It is excreted in almost solid, form., (v) Creatine is seen as excretory product in foetus, pregnant and, the lactating women. It is most probably associated with the, processes of histolysis and histogenesis going on in above, written examples., (vi) Creatinine is the end product of creatine metabolism., , Human Excretory System, It functions to remove waste products from the human body. This, system consists of specialised structures and capillary networks that, assist in the excretory processes. It includes two kidneys (possessing its, functional unit, the nephron), two ureters, urinary bladder and urethra., Aorta, Kidney, Dark red, bean-shaped, structure. Right one, is slightly lower than, the left one. Metanephric,, retroperitoneal in position., , Ureter, Narrow, tubular structure,, opens into urinary bladder, and pour urine into it., Composed of transitional, epithelium., , Urethra, Canal-like structure which, opens to exterior by urethral, orifice. It is much longer in males., , Brings oxygenated blood, to kidneys., , Inferior Vena Cava, Carries deoxygenated blood, from kidneys., , Urinary, Bladder, Reservoir of urine in the, pelvic cavity, inner lining is, composed of transitional, epithelium., , Human urinary system, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 299, , Excretory Products and Their Elimination, , Kidney, Renal Fascia, Anchor kidney to, abdominal wall., , Renal Column of Bertini, Projections of cortex into medulla., Minor Calyces, Fine branches originating, from major calyx., , Adipose Capsule, Fat layer which protect, the kidney., , Major Calyx, Branches of renal pelvis., Renal Capsule, Fibrous connective tissue, lining of kidney., , Renal Pelvis, Proximal part of ureter, breaks, into 2-3 branches towards kidney, called major calyx., , Cortex, Outer dark region., Medullary Pyramids, Medulla is subdivided into, number of conical areas to, form medullary pyramids., , Renal Papilla, Serves as the opening of medullary, pyramids in the lumen of minor calyx., , Longitudinal section of kidney, Proximal Convoluted Tubule, , Malpighian, Corpuscle, , Glomerulus, Bowman’s, Capsule, , Lined by single layer cuboidal cells, bearing microvilli, in between microvilli, apical canaliculi occur which are, involved in the cellular mechanism of, protein from the filtrate., , Collecting Duct, 20 mm long tube, lined by, cuboidal cells. Several, collecting tubes join to, form the duct of Bellini., , Descending Limb, Lined by simple cuboidal, epithelium with few cells, and small microvilli, , Distal Convoluted Tubule, Situated in the cortex region of kidney,, lined by cuboidal epithelium without, true brush border, , Ascending Limb, Length of cells increases, in this region, cells are, not brush bordered, , Main Loop, Length of cells is minimised, in this region, , Nephron showing blood vessels, duct and tubule, , www.aiimsneetshortnotes.com
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300, , Telegram @neetquestionpaper, , Handbook of Biology, , Types of Nephrons, On the basis of location and size, nephrons are of two types, (i) Cortical nephrons These nephrons mainly lie in the renal, cortex; form about 85 per cent of total nephrons and the loop of, Henle is too short and extends only very little into the medulla., (ii) Juxtamedullary nephrons These nephrons lie in the inner, margin of cortex; form about 15 per cent of total nephrons, and the loop of Henle is very long and runs deep into the, medulla., Afferent Arteriole, , Efferent Arteriole, Narrow and long capillaries which, form a fine peritubular capillary, network around renal tubule, a, part of which forms vasa rectar, (run parallel to Henle loop), , Short and wide capillaries,, which break up into 20-50, glomerular tufts., , Bowman’s, Capsule, , Glomerulus, Capillary tuft present in the, concavity of Bowman’s, capsule, capillaries have, arterial parts at both the ends., Blood pressure in glomerulus, is much higher than else, where in the body, , Double walled epithetial sac, consisting of outer parietal, and inner visceral layer., Parietal layer consists of, squamous epithelium and, visceral layer bears podocyte., , Malpighian body, , Urine Formation, Urine formation in human beings occurs in following two steps, , 1. Urea Formation within the Liver, The centre process of urea formation takes place with the cycle called, ornithine cycle or Kreb-Henseleit cycle., Urea, , Step-4, , Step-1, , Arginine, Fumaric, acid, , Carbamoyl, phosphate, , Ornithine, , Citrulline, , Step-3, , Step-2, Arginino, succinic, acid, , Aspartic, acid, , Urea cycle, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 301, , Excretory Products and Their Elimination, 2. Formation of Urine by the Kidney, It can, (i), (ii), (iii), , be divided into following three sub-categories, Glomerular filtration or ultrafiltration, Selective reabsorption, Tubular secretion, , 1. Ultrafiltration, Carried out due to very high pressure in the glomerular, capillaries due to its semipermeable membrane., Glomerular filtrate contains large amount of water and, essentially all constituents of blood except blood cells,, proteins, pigments, certain drugs (if present in blood), etc., It is a complete passive force and main force for filtration is, Glomerular Hydrostatic Pressure (GHP)., , Afferent arteriole, , Isotonic, glomerular, filtration, of amino acids,, glucose, water,, urea, NH3 and, other salts, , Efferent arteriole, , (Na++ H2O by, osmosis), , PCT, , 2. Tubular Reabsorption, , It occurs when glomerular filtrate, enters the PCT. It involves both, passive and active transport of, selected material from the filtrate, into blood across tubular epithelium., Filtrate is almost isotonic to plasma., Reabsorption of various components, Peritubular occurs here as follows Na+ and, capillary, K+ = Active transport Glucose and, amino acids = Passive transport, Water = Osmosis , Cl–, urea and, other, Solutes = Simple diffusion, , 3.Tubular Secretion, It is the removal of selected, components from the blood of the, peritubular blood capillaries into the, nephric filtrate. It involves the active, DCT, transport of ammonia, urea, uric acid,, Hypotonic creatine, hippuric acid, drugs like, penicillin, etc., , urine, , Hypertonic, filtrate, Descending, limb, , Loop of Henle, , Collecting, duct, , Hypertonic, urine, , Processes involved in urine formation by kidney, , Glomerular Filtration Rate (GFR), It is the quantity of glomerular filtrate formed per minute in all the, nephrons of both kidneys. In normal person, GFR is 125 mL/min or, about 180 litres per day., , www.aiimsneetshortnotes.com
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302, , Telegram @neetquestionpaper, , Handbook of Biology, , Filtration Fraction, It is the fraction of the renal plasma which becomes the filtrate. It is, the ratio between the renal plasma flow and glomerular filtrate which, is expressed in percentage. The normal filtration fraction varies from, 15-20%., Glomerular filtration rate, Filtration fraction =, × 100, Renal plasma flow, 125, =, 650 − 700, = 17.8 − 19.2%, (The renal plasma flow is about 650-700 mL/m or about 940 litres/day.), , Pressures in the Renal Circulation, During renal circulation, pressure varies at different regions of nephron, as follows, 100 mmHg, , Blood Colloidal Osmotic, 18 mmHg Pressure (BCOP), Pressure exerted by plasma, proteins in the glomeruli,, which are not filtered through it., It is about 30-32 mm of Hg., , 18 mm Hg, , Glomerular Blood, 13 mm Hg, Hydrostatic Pressure, (GHP), 10 mm Hg, It is the pressure of blood, inside the glomerular, capillaries which bring, about the process, of ultrafiltration. It is, about 60-75 mm of Hg., , Capsular Hydrostatic, Pressure (CHP), , 8 mm Hg, 10 mm Hg, , It is the pressure created, by the filterate within the, Bowman’s capsule against, the filteration membrane., It is about 18-20 mm of Hg., 0 mm Hg, , Pressures at different points in the vessels and tubules of nephron, , Effective Filtration Pressure (EFP), It is the total pressure that promotes filtration (as both BCOP and, CHP oppose the process of filtration)., It can be calculated as, EFP = GHP − (BCOP + CHP), = 60 mmHg − (30 mmHg + 18 mmHg), = 12 mmHg, Thus, a pressure of about 12 mmHg causes a normal amount of blood, plasma to filter from the glomerulus into the Bowman’s capsule., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 303, , Excretory Products and Their Elimination, , Mechanism of Filtrate Concentration, Mammals have the ability to produce a concentrated or hypertonic, urine. The different phases through which the urine becomes, hypertonic in relation to body fluids have been studied by Wirz and, associates (1951) and later on by Bray (1960)., It is a complex process and related to the anatomical distribution of, tubules along with Na+ ion concentration at different depths from the, cortex towards the medulla of kidney., Glomerulus, , 123, , Cortex, , DCT, , Glomerular filterate, enters the descending, limb of Henle’s loop, in isotonic state., , Due to the action of ADH, in this region, the filtrate, becomes isotonic., , Na+, , Collecting Duct, Due to ionic and water, exchange between the, tubular fluid and medullary, tissue fluid, the filtrate, become hypertonic., , H2 O, , Descending, Henle Loop, , 123, , Medulla, , Na+, +, , Passive diffusion of Na, ion from the surrounding, hypertonic tissue fluid into, the tubule makes the, filtrate hypertonic., , Na+, H2O, Na+, , H2 O, , Ascending, Henle‘s loop, , Hypertonic, Urine, , As this region of Henle’s loop is, impermeable to water and due to, active transport of Na+ ions, from the surrounding, the filtrate, becomes hypotonic., , Mechanism of tubular reabsorption and secretion, , Counter-current Mechanism, The theory of countercurrent mechanism was given by Berliner et. al., (1958). According to this theory, the role of vasa recta is very important, in urine concentration., The flow of the filtrate in the two limbs of vasa recta is in opposite, direction similarly as in the two limbs of Henle’s loop., , www.aiimsneetshortnotes.com
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304, , Telegram @neetquestionpaper, , Handbook of Biology, , The arrangement of vasa recta and Henle’s loop can be seen as follows, Direction of blood flow, , Direction of filtrate flow, , lons, , H 2O, , lons, , Vasa recta, (blood is flowing), , Henle’s loop, (filtrate is flowing), , Arrangement of vasa recta and Henle’s loop, , As the descending limb of vasa recta gradually enters deep into the, medulla, some water diffuses out from it and more ions are taken in. In, the ascending limb, on the other hand, the diffusion process is just in, opposite direction, thus isotonic blood leaves the medulla., The counter exchange reduces the rate of dessipation, thus reduces the, rate at which the countercurrent multiplier must pump Na + to, maintain any given gradient., , Regulation of Kidney Function, The functions of kidneys are regulated by following three mechanisms, 1. Control by JGA Juxta Glomerular Apparatus works through, RAAS, i.e., renin-Angiotensin-Aldosteron-system when the, blood pressure is decreased. In response, Renin enzyme is, released from JG cells.Rennin acts upon plasma protein, angiotensinogen and convert it to a protein angiotension II., Angiotensin II increases blood pressure by constricting the, arterioles, by increasing water and NaCl reabsorption in PCT, and by stimulating adrenal gland to secrete aldosterone which, work on DCT for the same cause., 2. Control by ANF Atrial natriuretic factor opposes the RAAS., ANF is released by atrial walls in response to increased blood, pressure. It inhibits the release of renin from JGA, reduces, aldosterone release from adrenal gland and inhibit NaCl, reabsorption by collecting duct., 3. Control by ADH Antidiuretic hormone is produced by, hypothalamus and secreted by posterior lobe of pituitary gland., When osmolarity of blood increases above 300 mos mL −1, in, response, osmoreceptors of hypothalamus promote thirst., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 305, , Excretory Products and Their Elimination, , Micturition, The expulsion of urine from the urinary bladder is called micturition., It is a reflex process, but in grown up children and adults, it can be, controlled voluntarily., Trigone, Consists of 3 openings, 2 of, ureters and one through which, urethra leaves the bladder., , Ureter, Detrusor muscle, Muscular layer of, urinary bladder., , Internal Sphincter, Modification of circular, smooth muscles., , External Sphincter, Made up of skeleton muscles which is, under voluntary control of nervous system., , 321, , Sympathetic, nerves, , L1, L2, , Sympathetic, chain, , Causes relaxation of, Urinary, detrusor muscles, bladder, Inferior, and constriction of, mesenteric, internal sphincter,, hence, filling of the ganglion, urinary bladder, Hypogastric, nerve, Internal sphincter, Urethra, External sphincter, , S2, S3, S4, , 123, , The urinary bladder and the internal sphincter are supplied by both, sympathetic and parasympathetic nerves whereas, the external, sphincter is supplied by the somatic nerve., , Pelvic, nerve, Hypogastric, ganglion, , Parasympathetic, nerves, Causes contraction of, detrusor muscles and, relaxation of internal, sphincter, hence emptying, of urinary bladder, , S2, S3, S4, , Somatic nerve, Maintains tonic contraction, of the skeleton muscles. During, micturition, it is inhibited, , Nerve supply to urethra and urinary bladder, , Role of other Organs in Excretion, Apart from kidneys, some other organs are also involved in the process, of excretion they are as follows, (i) Lungs These help in the elimination of CO2 (~18 L/day) and, water as water vapour (~400 mL/day.), , www.aiimsneetshortnotes.com
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306, , Telegram @neetquestionpaper, , Handbook of Biology, , (ii) Liver It plays a vital role in elimination of urea and bile, containing substances., (iii) Skin It excretes NaCl, glucose and fats with the help of sweat, and sebaceous glands., (iv) Intestine It eliminates salts, glucose and minerals like calcium, and iron., (v) Salivary glands It helps in the excretion of heavy metals., , Disorders of Excretory System, (i) Glomerulonephritis It is also called Bright’s disease which, is caused by the injury to the kidney, by congenital kidney, defects or by an allergic reaction to the toxins of bacteria such as, Streptococcus. The glomeruli become inflamed and engorged, with blood. Proteins and red blood cells enter the filtrate., (ii) Kidney stone The stone in the kidney gives rise to severe, colic pain starting in the back and radiating down to the front of, the thigh. It may come down in the bladder and would cause, frequent and painful urination and blood in urine., (iii) Pyelonephritis It is inflammation of the renal pelvis and the, medullary tissue of the kidney. It is usually caused by bacteria, that reaches the kidney by the way of urethra and ureter. It, usually affects countercurrent mechanism in the medulla., Affected person has inability to concentrate his urine., (iv) Renal tubular acidosis In this condition, the person is unable, to secrete the adequate quantities of hydrogen ions and as a, result, large amount of sodium bicarbonate are continuously lost, into the urine., , Artificial Kidney, In patients with damaged kidneys, urea and other nitrogenous wastes, are removed from the blood by an artificial kidney. The process is, called haemodialysis. Dialysis works on the principle of diffusion of, solutes and ultrafiltration of fluids across a semipermeable membrane., The pores of the membrane allow the passage of nitrogenous wastes in, dialysing fluid based on concentration gradient. The blood is thus, cleared of the nitrogenous wastes., , Renal Transplantation, It is a process of transplanting a functional and compatible kidney into, a patient with kidney failure. The donor should be a close relative of, the patient to avoid rejection by the immune system. Some special, drugs are also used to suppress the immune system in order to prevent, rejection., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 20, , Locomotion and, Movement, Locomotion, It is the self-propelled movement or the ability of an individual to move, from one place to another. An animal cannot locomote without, movement., , Movement, It refers to the change of position that does not entail the change of, location. Movements are brought about by internal or external forces., The movement of a non-living object is induced (due to external force),, while the movements of living things are autonomic (self-sustained)., Following types of movements are shown by the different cells of the, human body, Amoeboid, Affected by pseudopodia, and cytoskeletal elements, like microfilaments,, occurs in macrophages, and leucocytes in blood., , Muscular, It is carried by the contractive, property of muscles. Movement, of limbs, jaws, tongue, etc., are, muscular movements., , Ciliary, , Types of, Movements, , Occurs in most of internal, tubular organs, which are, lined by ciliated epithelium,, e.g., trachea, female, reproductive tract,etc., , Flagellar, Propulsion of flagella, helps the human, sperms to move, towards the ovum., , www.aiimsneetshortnotes.com
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308, , Telegram @neetquestionpaper, , Handbook of Biology, , Muscle, It is a specialised contractile tissue that brings about the movement of, different body parts. It is mesodermal in origin and contributes to, 40-50% of the body weight., Based on their location, muscles are of 3 types, i.e., striated, non-striated, and cardiac., Striated, , Non-striated, , They are present in the, limbs, body walls, tongue,, pharynx and beginning of, oesophagus., , They are present in the, oesophagus (posterior part, only), urinogenital tract,, urinary bladder, vessels, iris, of eye, dermis of skin and, arrector pili muscles of hair., , Cardiac, , Cylindrical., , Spindle-shaped., , Cylindrical., , Fibres unbranched., Multinucleate., Bounded by sarcolemma., , Fibres unbranched., Uninucleate., Bounded by plasmalemma., , Fibres branched., Uninucleate., Bounded by sarcolemma., , Light and dark bands, present., No oblique bridges and, intercalated discs., Nerve supply from central, nervous system., , Light and dark bands, absent., No oblique bridges and, intercalated discs., Nerve supply from, autonomic nervous system., , Blood supply is abundant., Very rapid contraction., They soon get fatigued., Voluntary., , Blood supply is scanty., Slow contraction., They do not get fatigued., Involuntary., , Faint light and dark bands, present., Oblique bridges and, intercalated discs present., Nerve supply from the, brain and autonomic, nervous system., Blood supply is abundant., Rapid contraction., They never get fatigued., Involuntary., , They are present in the, wall of the heart,, pulmonary veins and, superior vena cava., , Birds and mammals have two kinds of striated muscle fibres, in, their skeletal muscles, i.e., red (or slow) and white (or fast) muscle, fibres., , Red and White Muscle Fibres, Red muscle fibres are those striated muscle fibres, which are thinner, but dark red in colour. The dark red colour is due to the accumulation, of myoglobin. These are rich in mitochondria. They perform, slow contractions. Because of this, they are also known as slow, muscle fibres. However, they can perform sustained contraction over, long periods without getting fatigued. The reason for this is, non-accumulation of lactic acid., Red muscle fibres are more abundant in athletes like long distance, runners and cyclists. Extensor muscles present on the back of human, , www.aiimsneetshortnotes.com
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Telegram, @neetquestionpaper, 309, Locomotion and Movement, body are rich in red muscle fibres because these are required to, undergo prolonged contraction for the maintenance of erect posture, against the force of gravity. Avial flight muscles used in prolonged slow, flying (e.g., kite) are also rich in red muscle fibres., White muscle fibres are a type of striated muscle fibres which are, thicker and of pale-yellow colour. These muscle fibres do not contain, myoglobin and mitochondria are fewer in number. These muscle fibres, contract very quickly, but for short durations that’s why these are also, termed as fast muscle fibres., These fibres mostly perform anaerobic glycolysis for the liberation of, energy. Therefore, these fibres get fatigued quickly. These muscle, fibres are more abundant in short distance runners and other athletes., Muscles which move our eyeballs are rich in white fibres. Similarly,, avial flight muscles used in short distance, but fast flying (e.g.,, sparrow) have white fibres only., , Structure of Skeletal Muscle, Sarcolemma, , Blood capillaries, , Plasma membrane that, lines muscle fibres, , Muscle fibres (enlarged), Fascia, Collagenous connective, tissue layer which held, the fascicles together., , Muscle bundle, (fascicles), Contains a number, of muscle fibres, , (a), H-zone, Comparatively less dark zone,, the centre of A-band, called, Hensen’s zone, , A-band, Dark band/anisotropic band, , Myofibril, , I-band, Light band/isotropic band, , M-line, Mittleschiebe line in, the centre of H-zone, , Z-line, Dobie’s line/Krause’s membrane, or Zwischenschiebe line at the, centre of I-band, , (b), , (a) Muscle bundles and Muscle fibres, (b) Structure of myofibril, , www.aiimsneetshortnotes.com
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310, , Telegram @neetquestionpaper, , Handbook of Biology, , The part of myofibril between two successive Z-lines is sarcomere, (functional unit of myofibril)., I-band (light band), , M-line, , N-band N-band, , Thick myofilament, Consists of myosin, each myosin, is splitted into LMM and HMM by, trypsin; possess cross-bridges;, thicker, but longer, found only in, A-band., , Thin myofilament, , Z -line, , H-zone, A-band (dark band), One sarcomere, , Consists of 3 proteins-actin,, tropomyosin and troponin; free, Z-line, at one end; do not possess cross, bridges; thinner, but shorter, found, Zone of, overlap (O-band) in A and I-bands., , (a), Head, Contains, ATPase enzyme., Formed by one, heavy chain and, two light chains, each., , TpI, , Actin Binding Sites, Binds to E-actin during, muscle contraction., , Inhibits F-actin-myosin, interaction., , TpC, , TpT, , Calcium binding, polypeptide., , Binds to tropo, myosin and other, two troponins., , 123, Tail, Myosin, Composed of 6 polypeptide chains,, 2 identical heavy chain and 4 light, chains. 2 heavy chains wrap spirally, to form a double helix whose one, end forms 2 globular heads and, other elongated end forms tail., (b), , Tropomyosin, Double-stranded, α-helical rod., In resting state,, they coverup the, active sites of actin., , F-actin, Fibrous form of actin formed, by the polymerisation of, globular form (G-actin), in the presence, of Mg2+ ions., Tp = Troponin, , (c), , Muscle structure : (a) A sarcomere (enlarged) (b) Myosin filament, (c) Actin filament, , www.aiimsneetshortnotes.com
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Telegram, @neetquestionpaper, Locomotion and Movement, 311, Mechanism of Muscle Contraction, Sliding filament theory proposed by Huxley and Hanson (1954) best, explains the mechanism of muscle contraction. The essential features of, this theory are, During the process of muscle contraction, the thin myofilaments, show sliding inward towards the H-zone., The sarcomere shortens, without changing the length of thin and, thick myofilaments., The cross bridges of the thick myofilaments connect with the, portions of actin of the thin myofilaments. These cross bridges move, on the surface of the thin myofilaments resulting in sliding of thin, and thick myofilaments over each other., The length of the thick and thin myofilaments does not change, during muscle contraction., l, , l, , l, , l, , A-band, , I-band, , I-band, , M-line, , Relaxed, , Z-line, , H-zone, Cross-bridge, , Thin, Z-line, myofilament, , Thick myofilament, , Maximally, contracting, , Contraction in a sarcomere of muscle, , Electrical and Biochemical Events in Muscle Contraction, These events have been worked out by Albert Szent Gyorgyi and, others and involve sliding filament procedures as well., , www.aiimsneetshortnotes.com
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312, , Telegram @neetquestionpaper, , Handbook of Biology, , These are as follows, , 123, , Axon terminal, , Nerve impulse, causes the, Synaptic vesicle, release of, acetylcholine, Acetylcholine, from synaptic, vesicles into the, synaptic cleft., , 2 Acetylcholine, , Synaptic cleft, Receptor, sites of motor, end plate, , 321, , 1 Nerve impulse, , present in synaptic, cleft binds to receptor, sites of motor end plate, and causes its, depolarisation which, creates an action, potential., , Action Potential, , 3 Action potential reaches to, sarcoplasmic reticulum, of muscle fibre and causes, the release of calcium ions, into sarcoplasm., , Sarcoplasmic, reticulum, , 4 Calcium ions bind to troponin, ADP+Pi ATP, , Ca2+, , Active transport of, Ca2+ and inhibition, of contraction, , Ca, , 2+, , Diffusion, , and changes its shape which in, turn changes the shape of, tropomyosin and exposes the, active sites on the F-actin., , Troponin, Tropomyosin, ATP, , F-actin, Movement of, cross-bridge, , Thick myofilament, (myosin), , able to bind to these active sites., , 6 In the presence of myosin, , 9 ATP binds to myosin head,, causing dissociation from, actin and muscle relaxes., , 5 Myosin cross-bridges are then, , ATP, , ATPase,Ca2+ ions and Mg2+, ions, ATP breaks down to, ADP and phosphate and, energy is released in, the head., , 7 Energised myosin head, 8 Loss of energy causes, the myosin to move back, to its original position., , binds to actin filament., The cross-bridge moves, and causes the thin, filament to slide along, the thick myofilament., , www.aiimsneetshortnotes.com
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Telegram, @neetquestionpaper, Locomotion and Movement, 313, Types of Muscle Contraction, A skeletal muscle contraction may be any of several types., These are as follows, Isotonic, Tone or tension within a muscle, remains the same, but muscle, length changes (shortens),, producing movement., , Fibrillation, , Convulsions, , Individual fibres contract, asynchronously, producing, a flutter of muscle, but, no movement., , Isometric, Muscle tension increases,, while the muscle length, remains the same., , Twitch, Quick, jerky contraction in, response to a single, stimulus., , Abnormal uncoordinated, tetanic contractions of, varying groups of muscles., , Types of Muscle, Contraction, , Tonic, Small number of total muscle, fibres in a muscle contract,, producing a toutness of muscle, rather than a recognisable, contraction and movement., , Tetanic, Sustained contraction, produced by a series of, stimuli bombarding the, Increasingly stronger, muscle in rapid succession., twitch contractions occur, in response to constant-strength, stimuli repeated at the rate of, about once or twice a second., , Treppe, , Muscle Relaxation, After contraction, the calcium ions are pumped back to the sarcoplasmic, cisternae, blocking the active sites on actin myofilaments. The Z-line, returns to original position, i.e., relaxation of muscle fibre takes place., , Specialised Muscle Phenomena, Certain specialised phenomena associated with muscles are as follows, , All-or-None Law (Bowditch’s Law), It is a principle which states that response of a muscle/nerve to a, stimulus is not proportionate to the intensity of stimulus, but is either, present in full strength or completely absent., A single muscle fibre (striated, unstriated or cardiac) does not show, any gradation in contraction in relation to the degree to stimulus, i.e.,, like a nerve fibre, a muscle fibre does not respond to a stimulus till it is, equal to or above a minimum (threshold) value., , www.aiimsneetshortnotes.com
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314, , Telegram @neetquestionpaper, , Handbook of Biology, , The degree of contraction also shows independence with the intensity, of stimulus. At or above all the threshold value, a muscle fibre will, always contract with the maximum force irrespective of the strength of, the stimulus., However, the force of contraction may increase or decrease with the, change in pH, temperature, stretching of muscle fibre, etc., though, even under such condition increase or decrease in the value of stimulus, would not alter the force of contraction. Further, the entire muscle does, not follow the all-or-none rule., , Oxygen Debt, It is the extra oxygen required by the body muscles during relaxation, or recovery period over the resting state. During strenuous exercise,, the requirement of oxygen and hence, energy far exceeds its, availability through breathing., Therefore, other sources are tapped. These include oxygen from, oxymyoglobin, dephosphorylation of creatine phosphate, etc. After, their exhaustion, the muscles begin to respire anaerobically along with, aerobic respiration., Muscle contraction or activity under anaerobic conditions is termed as, anaerobic contraction. The lactic acid produced here accumulates in, the muscles. When exercise is stopped, the recovery process starts., During recovery, extra oxygen is required for which deep breathing, continues., The extra oxygen (extra to normal aerobic breathing) is used in, (i) Regeneration of oxymyoglobin., (ii) Oxidation of accumulated lactic acid., (iii) Restoration of depleted ATP., (iv) Restoration of creatine phosphate., Oxygen debt decreases with regular exercise because the regular, exercise increases oxymyoglobin content of the muscles and allows, sufficient deep breathing during exercise to perform aerobic, contractions., , Cori’s Cycle, A cyclic process involving the formation of lactic acid in the muscles, and regeneration of glycogen from it (in the liver) in order to reduce, accumulation of lactic acid in muscles and continued supply of glucose, to them., , www.aiimsneetshortnotes.com
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Telegram, @neetquestionpaper, Locomotion and Movement, 315, This cycle was discovered by Cori. The lactic acid formed in the muscle, passes into the bloodstream and reaches the liver where roughly 4/5 of, it is changed to glycogen, while rest 1/5 is oxidised to CO2 and H 2O., Afterwards, this glycogen is hydrolysed to form glucose that passes, into the bloodstream and reaches the muscles for the liberation of, energy and the production of fresh lactic acid., Importance With the help of Cori’s cycle, lactic acid is not allowed, to accumulate beyond a certain concentration within the muscles., This protects the neuro-muscular junction which is sensitive to lactic, acid. The cycle also replenishes glucose/glycogen in the muscles., Muscle, glycogen, , Blood, glucose, , Energy, , Blood, lactic acid, , Liver glycogen, (80%), , Liver lactic acid, , 20% oxidised to CO2 + H2O, , Cori’s cycle, , Muscle Fatigue, The decrease in the force of contraction of a muscle after prolonged, stimulation is called muscle fatigue., Cause A muscle is able to contract for a short time in the absence of, oxygen. But, it gets fatigued sooner because in the absence of oxygen,, the metabolic products of glycolysis (mainly lactic acid) accumulate, around it., This accumulation leads to muscle fatigue. Normally, pain is, experienced in the fatigued muscle. The site of fatigue is the, neuromuscular junction., , Rigor Mortis, Just few hours after death, muscles stiffen and become hard. This, condition is called rigor mortis. It first appears in lower jaw and then, appears in all body muscles. It occurs due to permanent irreversible, contraction between actin and myosin, which in turn occurs due to, exhaustion of ATP from blood., , www.aiimsneetshortnotes.com
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316, , Telegram @neetquestionpaper, , Handbook of Biology, , Functional Classification of Skeletal Muscles, Type of, Skeletal Muscle, Flexors, Extensors, Abductors, Adductors, , Function, , Example, , Muscles which bend one part of, the body over the other., Muscles which extend or, straighten the limbs., Muscles which pull a limb away, from the median line., Muscles which bring a limb, towards the median line of the, body., , Biceps bending forearm, towards upper arm., Triceps extending forearm and, is antagonous to biceps., Deltoides of shoulder., , Depressors, , Muscles which lower some parts., , Elevators, , Antagonistic to depressors as they, raise a body part., , Pronators, , The muscle that turns the palm, downward or backward., Antagonistic to pronator, i.e.,, turns the palm upward or, forward., Decreases the size of an opening, and close it., The muscles around the, openings, which increase their, size and open them. Antagonistic, to sphinctors., Associated with rotatory, movements of a body part., , Supinators, , Sphinctors, Dilators, , Ratators, , Latissimus dorsi which draw, the whole forelimb towards the, body and is antagonous to, deltoides., Depressor mandibularis lowers, the lower jaw (similarly, pectoralis major is the, depressor muscle for the wings, of birds)., Masseter which lifts the lower, jaw (similarly pectoralis minor, is the elevator muscle for the, wings of birds)., Pronator teres in mammalian, limbs., Supinator in human forelimbs., , Pyloric sphincter of alimentary, canal., Iris., , Pyriformis which raises and, rotates the thigh., , Skeletal System, It consists of a framework of bones and cartilages. They form the, internal framework (endoskeleton) of the body. Tendons and ligaments, are also associated connective tissues of the skeletal system., , www.aiimsneetshortnotes.com
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Telegram, @neetquestionpaper, Locomotion and Movement, 317, Components of Skeletal System, Bone, Hardest tissue, homeostatic reservoir of calcium, magnesium,, phosphorus, etc. It is the major component of vertebrate endoskeleton., Types of Bones, A. On the basis of shape, there are following categories of bone, Long Bones, , Short Bones, , Possess an elongated shaft (diaphysis), and 2 expanded ends (epiphyses),, shaft has a central medullary cavity, e.g., femur, ulna, etc., , Pneumatic Bones, , Broad, short, can be of, any shape, e.g., carpals,, tarsals, etc., , Types of Bones, , Sesamoid Bones, , Irregular, contain large air spaces, which make them light, e.g., sphenoid,, ethmoid of skull., , They are in the form of nodules, embedded in tendons and joint, capsules, ossification occurs, after birth, e.g., patella., , Irregular Bones, , Flat Bones, Resemble shallow plates and form, boundaries of certain body cavities,, e.g., scapula, ribs, sternum, etc., , Completely irregular in shape,, e.g., hip bone, vertebral,, bones in the base of skull, etc., , B. On the basis of development, bones are of three types, Membranous Bones, , Cartilaginous Bones, , Ossify from mesenchymal, condensations, intra-membranous, ossification occurs, e.g., bones, of skull, facial bones., , Ossify from perforated cartilage, models, intra-cartilaginous, ossification occurs, e.g., bones, of limbs, vertebral column., , Developmental, Basis of Bone, , Membrocartilaginous Bones, Ossify partly from cartilage and partly, from mesenchymal condensations,, e.g., clavicle, temporal, etc., , C. Based on their histological structure, there are two major types of bone, (i) Compact bone It forms most of the diaphysis (shaft) of long, bones and the thinner surfaces of all other bones. Their lamella, is surrounded into sets of concentric ring, with each set, surrounding a Haversian or central canal., (ii) Spongy bone It is mainly located in the epiphysis (ends) of, long bones. It forms the interior of all other bones. It consists of, delicate inconnecting rods or plates of bone called trabeculae,, which add strength to bone without adding the weight., , www.aiimsneetshortnotes.com
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318, , Telegram @neetquestionpaper, , Handbook of Biology, , Various components of the bone and their arrangements is shown in the, figure below, Outer circumferential zone, Thin peripheral zone of compact, bone between haversian zone and, periosteum. Its lamellae of bone, matrix run parallel to long axis of, the bone., , Inner circumferential, zone, Thin zone between haversian, zone and endosteum. It also, comprises longitudinal lamellae., , Periosteum, Outermost layer of bone made, up of fibres and fibroblasts, has, rich supply of blood vessels and, lymphatics. It limits the bone growth., , Bone marrow, Fatty network of connective, tissue, fills bone cavities, very, nutritious., , Haversian zone, Also called zone of osteons,, contains haversian canals and, their related Lamellae, in 4-20 concentric layers, around them., , Endosteum, Also called cambium, participates in, bone formation (osteogenic layer)., Haversian canal, , Haversian system, Required due to large sizes, of mammalian bones as, superficial supply of blood, is insufficient to provide, essential requirement to, osteocytes., Interstitial zone, Irregular, narrow gaps. remnants of former, lamellae or osteons formed when osteones, are continously reabsorbed and, formed again and again during bone, remodelling in some bones., , Vertical canals present, parallel to the length of, compact bone region., , Lamellae, Highly complicated system, in which the matrix of, mammalian bone is laid down, so as to provide the ostrocytes, with maximum chemical, exchange facility., Arteriole, Venule, Nerve, , Conaliculi, Branching, processes,, interconnect, two lacunae, , Canaliculi, , Lacuna, Contains one, osteocyte, per lacunae., , Osteocyte, , Osteocytes, Bone cells, remain in permanent Go phase, of cell cycle. Cementing lines of Ebner, separate one osteon from another., , Generalised internal structure of bone, , Cartilage, It is a semi-rigid dense connective tissue composed of cells called, chondrocytes dispersed in a firm gel-like ground substance called, matrix. It is non-vascular and does not contain blood vessles., , www.aiimsneetshortnotes.com
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Telegram, @neetquestionpaper, Locomotion and Movement, 319, Nutrients are diffused through the matrix enriched with, glycosaminoglycans, proteoglycans and macromolecules that interact, with collagen and elastic fibres., Types of Cartilage, Hyaline, It has crystal clear matrix with, less fibres, forms articular, surfaces at the joints of long, bones., , Elastic, , Fibrous, , It has numerous yellow, elastic fibres, found in ear, pinna, external auditory meatus,, eustachian tube, etc., , It has numerous white, fibres, found in pubis, symphysis and sterno, clavicular joints., , Perichondrium It is a fibrous membrane that surrounds the, cartilage. It contains chondroblasts with the potential of cartilage, formation. Articular cartilage that covers the bones of movable joints is, devoid of perichondrium., , Types of Skeletal System, On the basis of the position of the skeletal structures in the body, the, endoskeleton is of two types, Skeletal System, Axial Skeleton, Present on the median longitudinal, axis of the body. It consists of skull,, vertebral column, sternum and ribs., , Appendicular Skeleton, Present at the lateral sides which extend outwards, from the principal axis. It consists of pectoral and, pelvic girdle and bones of arms and legs., , 1. Axial Skeleton, It consists of 80 bones. The various components of axial skeleton are as, follows, Bones, Axial Skeleton, Skull, Braincase, Paired, Unpaired, , Face, Paired, , Unpaired, , Numbers, , Parietal, Temporal, Frontal, Occipital, Sphenoid, Ethmoid, , 2, 2, 1, 1, 1, 1, , Maxilla, Zygomatic, Palatine, Nasal, Lacrimal, Inferior nasal concha, Mandible, Vomer, , 2, 2, 2, 2, 2, 2, 1, 1, , www.aiimsneetshortnotes.com
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320, , Telegram @neetquestionpaper, , Handbook of Biology, Bones, , Numbers, Total Skull Bones, , 22, , Malleus (outer), Incus (middle), Stapes (inner), Total Auditory Ossicle Bones, , Auditory Ossicles, , 2, 2, 2, 6, , Hyoid, Vertebral Column, Cervical vertebrae, Thoracic vertebrae, Lumbar vertebrae, Sacrum, Coccyx, , 1, 7, 12, 5, 1 (5), 1 (4), , Total Vertebral Column Bones, Thoracic Cage, Ribs, Sternum (3 parts, sometimes considered 3 bones), , 26 (33), 24 (12 × 2), 1, , Total bones of thoracic cage, Total bones of axial skeleton, , 25, 80, , (i) Skull, The skull of human beings is tropibasic, i. e. , the eyes are not situated, much apart and the brain and eyes are present at different planes in, the skull in well-defined sockets. Human skull is dicondylic, i. e. , with, two occipital condyles, which connect the skull with the vertebral, column., Coronal suture, Parietal bone, , Frontal bone, Sphenoid bone, Lacrimal bone, Nasal bone, Nasolacrimal bone, Ethmoid bone, , Squamous suture, Temporal bone, Occipital bone, , Zygomatic bone, Mandibular condyle, External auditory canal, Mastoid process, Styloid process, Condylar region, , Maxilla, Mental foramen, Mandible, Zygomatic arch Coronoid process, , Human skull showing its various components, , Functions of Skull, l, , l, , This bony covering protects the brain from injuries., The skull bears jaws (craniostylic suspension), which help the, animal for cutting and masticating the food., , www.aiimsneetshortnotes.com
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Telegram, @neetquestionpaper, Locomotion and Movement, 321, (ii) Vertebral column, It is the main bony region present at the axis of an individual body., Vertebral centrum is the portion which contains the vestiges of, notochord. Hence, the centrum is the main identifiable part of a, vertebrae., Various types of centrum in different animal groups are as follows, , Procoelous, (some fishes and, amphibians), , Amphicoelous, (8th vertebra of frog), , Acoelous, (9th vertebra of frog), , Opisthocoelous, (some lower amphibians, and most fishes), , Heterocoelous, (also called keeled, centrum in birds), , Amphiplyton, (characteristic of, mammals), , Types of centrum, , Structure of a Typical Vertebra, Basic components of a typical vertebrae include neural canal, neural arch,, centrum, neural spine and various processes. These structures in outline, diagrammatic view are as follows, Neural Spine, Backwardly projecting low ridge,, raised from neural arch., Neural Arch, Posterior portion of, vertebra which encloses, the spinal cord, bony-ring,, thick and rod-like., , Neural Canal, The hole formed, by neural arch., , Centrum, Large, disc-like, anterior,, flattened portion of vertebra,, also called body., , Zygapophyses, Flattened processes, that help the, articulation of vertebrae, with one another., , Haemal canal, Haemal Spine, , Haemal Arches, , Typical vertebra, , www.aiimsneetshortnotes.com
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322, , Telegram @neetquestionpaper, , Handbook of Biology, , Cervical region, (curved anteriorly), , Cervical vertebrae, First cervical vertebra (atlas) have very small bodies,, Second cervical vertebra, except for atlas,which has, (axis), no body. They have split, spinous processes., Seventh cervical vertebra, First thoracic vertebra, , Thoracic region, (curved posteriorly), , Body, Intervertebral disc, Twelfth thoracic vertebra, , Thoracic vertebrae possess, long, thin spinous processes, and have extra articular, facets on their lateral surfaces, that articulate with the ribs., , First lumbar vertebra, Lumber region, (curved anteriorly), , Inter vertebral foramina, Transverse process, Spinous process, Fifth lumbar vertebra, , Lumbar vertebrae have, large, thick bodies and, heavy, rectangular, transverse and, spinous processes., , Sacral promontory, Sacrum, Sacral and, coccygeal region, (curved posteriorly), , Sacrum is formed by the, fusion of 5 sacral vertebrae., Coccyx is formed by the, fusion of 4 vertebrae., , Coccyx, , Vertebral column (right lateral view), , (iii) Thoracic Cage, It consists of sternum and ribs. The sternum or breastbone is a flat, bone which is made up of 8 skeletal elements (sternebrae)., Suprasternal notch, Clavicular notch, For 1st costal cartilage, Manubrium (first sternebrae), For 2nd costal cartilage, For 3rd costal cartilage, Body, For 4th costal cartilage, For 5th costal cartilage, For 6th costal cartilage, For 7th costal cartilage, Xiphoid process (last sternebrae), , The sternum (posterior view), , www.aiimsneetshortnotes.com
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Telegram, @neetquestionpaper, Locomotion and Movement, 323, In mammals, the number of thoracic ribs are equal to the number of, thoracic vertebrae, i.e., humans has 12 number of thoracic ribs., A generalised rib consists of a vertebral (dorsal) part and a sternal, (ventral) part., 12, , 3, , Tubercular Part, Attaches itself with the, transverse process of, the vertebrae., , Vertebral Part, Bony part, attaches the rib, with the vertebral column., Further divided into capitular, and tubercular part., , Capitular Part, Attaches itself with the, centrum of vertebrae., , 1, , 2, , 3, , Sternal Part, Cartilaginous in nature,, attaches the rib with the, sternum., , Generalised structure of a rib, , Thoracic ribs of humans are double headed and classified as true ribs,, false ribs and floating ribs. The attachment and arrangement of ribs, and sternum looks like, Seventh cervical vertebra, First thoracic vertebra, Jugular notch, Sternal, angle, Costal, cartilage, , Manubrium, Body, Xiphoid, process, , False Ribs, (8-10), Indirectly attached, to sternum, , Floating Ribs (11-12), Not attached with the sternum, , The sternum and ribcage, , www.aiimsneetshortnotes.com, , 123, , True Ribs, (1-7), Directly, attached, to sternum, , Sternum
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324, , Telegram @neetquestionpaper, , Handbook of Biology, , 2. Appendicular Skeleton, It consists of total 126 bones. The various components of it are as follows, Bones, , Number, , Appendicular Skeleton, Pectoral Girdle, Scapula, Clavicle, Upper Limb, Humerus, Ulna, Radius, Carpal bones, Metacarpal bones, Phalanges, , 2, 2, , Total bones of pectoral girdle and, forelimbs, Pelvic Girdle, Coxal bone, Lower Limb, Femur, Tibia, Fibula, Patella, Tarsal bones, Metatarsal bones, Phalanges, , 2, 2, 2, 16 (8 × 2), 10 (5 × 2), 28 (14 × 2), 64, , 2, , Total bones of pelvic girdle and, hindlimb, Total bones of appendicular skeleton, Total bones, , 2, 2, 2, 2, 14 (7 × 2), 10 (5 × 2), 28, 62, 126, 206, , (i) Pectoral girdle, It is divided into separate right and left halves. Each half is composed, of two bones, i.e., scapula and clavicle., Coracoid Process, Present below the clavicle and provides the, attachment for arm and chest muscles., , Spine, A ridge that runs across the, posterior surface of scapula., , Clavicle, Collarbone which articulates with scapula at, acromian process. Its proximal end is, attached to the sternum. It is the first bone to, begin ossification in the foetus., , Acromian Process, A projection that extends from scapular, spine to form the point of the shoulder., , Glenoid Cavity, Fourth fossa of scapula where the, head of humerus connects to it., , Scapula, Shoulder blade, flat, triangular bone with, 3 large fossae where muscles extending, to the arm are attached., , Components of pectoral girdle, , www.aiimsneetshortnotes.com
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Telegram, @neetquestionpaper, Locomotion and Movement, 325, (ii) Bones of arm or Forelimb, It consists of total 60 bones including the humerus, ulna, radius,, carpals, metacarpals and phallanges., , Lesser, tuberosity, , Humerus, A long bone, Deltoid, with rounded, tuberosity, head, av-shaped, ridge and a flat, lower end., Epicondyle, Capitulum, Trochlea, , Ulna, It has a large olecranon process, at its upper end, a trochlear notch, and a radial notch. Its distal end, has 2 eminences and articulates, with wrist bones., Radius, It is lateral and shorter, than ulna. Its head can, rotate against humerus, and ulna, it does not, attach as firmly to, humerus as ulna does., Carpals (8), Metacarpals (5), Phalanges (14), , Head, , Anatomical, neck, , Coronoid, fossa, Medial, epicondyle, Trochlea, , Greater, tuberosity, Lesser, tuberosity, Bicipital, groove, Surgical neck, , Lateral supra, condylar ridge, Radial fossa, Lateral, epicondyl, Capitulum, , Scaphoid, Lunate, Trapezoid, Triquetrum, Trapezium, Pisiform, Capitate, Hamate, Metacarpals, , 123, , Greater, tuberosity, , Carpals, , Phalanges, , Bones of forelimb, , (iii) Pelvic girdle, Each half of pelvic girdle is known as coxal or innominate bone. The, right and left coxal or hip bones join each other anteriorly and the, sacrum posteriorly to form a ring of bone called the pelvic girdle., Each coxal bone is formed by three bones fused to one another to form, a single bone. The ilium is the most superior, the ischium is inferior, and posterior and the pubis is inferior and anterior., Acetabulum It is the socket of the hip joint. All the three bones,, i. e. , ilium, ischium and pubis participate equally in the formation of, acetabulum., , www.aiimsneetshortnotes.com
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326, , Telegram @neetquestionpaper, , Handbook of Biology, , Posterior superior iliac spine, Pelvic inlet, Sacrum, , Iliac crest, Sacroiliac, joint, Anterior superior, iliac spine, Anterior inferior, iliac spine, Coccyx, Pubic tubercle, Obturator foramen, Pubic symphysis, , Ilium, Ischial spine, Acetabulum, Pubis, Ischium, Subpubic angle, , Anterosuperior view of pelvis, , (iv) Bones of leg or hindlimb, It consists of total 60 bones including femur, tibia, fibula, patella,, tarsals, metatarsals and phallanges., Greater, trochanter, , Head, , Longest bone, of the body with, 3 projections, at anterior end, and 2 condyles, at distal end., , 321, , Femur, , Head, Greater, trochanter, , Quadrate, tubercle, , Trochanteric, crest, Lesser, trochanter, , Lesser, trochanter, , Shaft, , Facet for lateral, condyle of femur, , Medial, epicondyle, Lateral, epicondyle, , Strip of medial facet,, in contact with femur,, only in extreme flexon, , Patella, It is kneecap, located, within the major tendon, of anterior thigh muscle, and enables the tendon, to bent over the knee., , Tibia, , Tarsals, , Fibula, Shorter, thin and located, more laterally., , 5 432 1, , Metatarsals (5), Phallanges (14), , 34241, , Longer, thicker and, lies more medially., It is the main weight, bearing bone., , Tarsals (7), , Trochanteric, fossa, , Neck, , Facet for medial, condyle of femur, , Talus, Calcaneum, Navicular, Cuboid, 3rd cuneiform, 2nd cuneiform, 1st cuneiform, Metatarsals, Phalanges, 5, 4, , 3, , Bones of hindlimb, , www.aiimsneetshortnotes.com, , 2, , 1
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Telegram, @neetquestionpaper, Locomotion and Movement, 327, Joints, A joint or an articulation is a place where two bones of the skeletal, system meet. Arthrology is the science of joint structure, function and, dysfunction., Based on the degree of motion, joints are of following types, Synchondroses, , Syndesmoses, Bones are separated, by some distance and, held together by ligaments,, e.g., fibrous membrane, connecting distal parts, of radius and ulna., , Synarthroses, Fibrous, immovable joints., Adjacent bones are bound, by collagen fibres., , Gomphoses, It consists of pegs fitted, into the sockets and held, in place by ligaments,, e.g., joint between tooth, and its socket., , Cartilaginous, slightly, movable joints., Adjacent bones are, linked by cartilage., , Types of, Joints, Diarthroses, , Bones are bound by hyaline, cartilage, e.g., attachment of, first rib to the sternum by a, hyaline costal cartilage., , Symphyses, Bones are joined by fibro, cartilage, e.g., pubic, symphysis in which right, and left pubic bones are, joined by the cartilaginous, inter-pubic disc., , Freely movable, synovial joints., Structurally most complex type, of joints., , Sutures, Fibrous joints between, the bones of the skull., They occur nowhere, else in the body, except skull., , Amphiarthroses, , Multiaxial, , Biaxial, , Monoaxial, , They can move in any, 3 fundamental, mutually perpendicular, planes (x, y and z),, e.g., ball and socket joint., , They are able to move, in only two planes,, e.g., condylar, saddle, and plane joints., , They can move in only, one plane, e,g., hinge, joint and pivot joint., , Structure of Synovial Joints (Diarthroses), Synovial membrane, Composed of secretory, epithelial cells (which, secrete synovial fluid), and macrophages (that, remove debris from the, joint cavity)., , Articular cartilage, A layer of hyaline cartilage,, which covers the ends of, bones. It is about 2-3 mm, thick., , Synovial fluid, Ligament, It joins the two, bones together., , Thick sticky fluid rich in albumin, and hyaluronic acid. It nourishes, articular cartilage and makes the, movement at these joints, almost friction-free., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 328, , Handbook of Biology, , Types of Synovial Joint, Various type of synovial joints and their respective position in the body, is given in the following figure, Head of humerus, , Ball and, socket joint, , Pivot joint, , Head of one, bone fits into, cup-like depression, Humerus, of another., , Scapula, Radius, , Hinge joint, Able to flex, and extend in, only one plane., , Saddle joint, , Projection of, one bone fits, into ring-like, ligament of, another allowing, one bone to, rotate., , Ulna, , Carpal, bones, Carpal, bone, , Ulna, , Each bone, surface is, saddle-shaped., , Metacarpal bone, , Gliding joint, Plane joint with, slight concave, or convex bone, surfaces that, slide over each, other., , Condylar joint, Metacarpal bone, of thumb, Phalanx, , Oval convex, surface of one bone, articulates with an, elliptical depression, of another., , Different types of synovial joints in human forelimb, , Disorders of Muscular and Skeletal System, 1. Arthritis It refers to the group of inflammatory and, degenerative conditions that cause stiffness, swelling and pain, in the joints., There are several different types of arthritis, each having, different characteristics., (i) Osteoarthritis It most often involves the knees, hips and, hands and usually affects middle-aged and older people., (ii) Rheumatoid arthritis It is a damaging condition that, causes inflammation in joints and in other body tissues, such, as heart coverings, lungs and eyes. It affects individual of all, age groups., , www.aiimsneetshortnotes.com
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Telegram, @neetquestionpaper, 329, Locomotion and Movement, 2. Bursitis It is the inflammation of the bursae present within, the synovial joints as small membrane bound sockets which hold, the synovial fluid. It mainly occurs due to an injury or pressure, on a joint for a long duration., 3. Muscular dystrophy It is a genetic disease that damages the, muscle fibres. Its symptoms include weakness, loss of mobility, and lack of coordination. It can occur at any time in a person’s, life and has no cure., 4. Myasthenia gravis It is characterised by weakness and, rapid fatigue of skeletal muscles. It is a chronic autoimmune, neuromuscular disorder in which the body produces antibodies, that block the muscle cells from receiving messages from the, nerve cells., 5. Spondylitis It is a chronic and developed form of arthritis, that affects vertebrae. It is found in a person who keeps bending, their neck for several hours., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 21, Neural Control, and Coordination, Nervous system is the master controlling and communicating system, of the body through which the activities of the animal and its, awareness and reaction to outside environment are coordinated., Neurons or nerve cells are the functional unit of nervous system., , Human Neural System, Humans have highly integrated nervous (or neural) system and for the, convenience of study it can be divided into two principal parts., Human Neural System, Central Nervous System, , Peripheral Nervous System, , Dorsally placed structure lying along, the mid-dorsal axis of the body., It is the integrating and command, centre of the nervous system., , Brain, , This system consists of nerves, that extend from the brain and, spinal cord and known as cranial, nerves and spinal nerves, respectively., , Spinal Cord, , Anterior most part, lodged, in the cranial cavity of skull., , Posterior part, run mid-dorsally, within vertebral column., , Sensory or Afferent Division, Consists of nerve fibres that convey, impulses to CNS from sensory, receptors located in the body., , Motor or Efferent Division, Consists of nerve fibres that transmit, impulses from the CNS to effector, organs, i.e., muscles and glands., , Autonomic Nervous System (ANS), Consists of visceral motor fibres that regulate the activities of smooth, muscles, cardiac muscles and glands (involuntary nervous system)., , Parasympathetic Nervous System, , Sympathetic Nervous System, , This system conserves energy and, promotes non-emergency functions., , It mobilises body during, emergency situations., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Neural Control and Coordination, 331, Central Nervous System, It consist two major divisions, i.e., brain and spinal cord., , Brain, It is the highly coordinated centre of the human body which weighs, about 1220 to 1400 grams., The human brain is covered by three membranes or meninges (sing., meninx) namely piamater, arachnoid membrane and duramater., 4 Epidural Space, Space between duramater, and cranium; contains, fatty connective tissue., , 1 Duramater, Outer tough, fibrous, collagenous layer,, inserted in periosteum, of cranium., , 5 Subdural Space, Space present between, duramater and arachnoid., It is filled with fatty connective, tissues., 6 Subarachnoid Space, Space between arachnoid, and piamater;filled with, Cerebrospinal Fluid (CSF)., , 2 Arachnoid, , Membrane, Middle layer,, non-vascularised,, also called spider web., , 3 Piamater, Innermost layer, highly, vascularised, soft of all., , Meninges and spaces of brain : 1, 2, 3 in the figure are meninges, and 4, 5, 6 are spaces of brain, , The human brain is divisible into three parts as follows, Rhinencephalon or olfactory lobes, Prosencephalon, or, Forebrain, , Vertebrate, Brain, , Telencephalon or cerebrum, Thalmencephalon or diencephalon, , Mesencephalon, or, Midbrain, , Optic lobes, , Rhombencephalon, or, Hindbrain, , Pons Varolii, , Cerbellum, , Medulla oblongata, , 1. Forebrain, (i) Rhinencephalon Anterioventral part of forebrain, functionally, related to smell, consists of olfactory lobes as paired, fused, posterior portion., , www.aiimsneetshortnotes.com
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332, , Telegram @neetquestionpaper, , Handbook of Biology, , The variations in rhinencephalon in different animal groups is shown, in the figures below, Olfactory region, relatively smaller, major, part is formed by, olfactory lobes, anterior, most portion runs as, olfactory nerves into, nasal chambers., , Olfactory nerve, Olfactory lobe, , (a), Olfactory tract, , Olfactory lobe, Rhinal fissure, Cerebral hemisphere, Optic nerves (2nd), Sylvian, fissure, , Hippocampal, lobe, , (b), , Olfactory region, relatively larger, lobes, Dorsomedian are smaller, major part, is formed by olfactory, fissure, tract, a rhynial fissure, separates both lobes, from cerebral lobes., , Front lobe, , Olfactory tract, Olfactory bulb, , Anterior portion is lost,, hence the lobes look, ventral in position as, olfactory bulbs., , Optic nerve, , Optic tract, (c), , Olfactory lobes : (a) Frog, (b) Rabbit (c) Human, , (ii) Telencephalon Most developed part in humans, performs, specialised functions like intelligence, learning skills, memory,, speech, etc. It has shown maximum development during, evolution, in particular its roof (pallium) in vertebrates other, than mammals., Neopallium, Highly developed pallium in, mammals containing folds (gyri), and depression (sulci)., , Allocortex, , Neocortex, , Centralised old portion, of pallium., , Circumcentric newly, developed portion of, pallium., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Neural Control and Coordination, 333, Lobes of Cerebrum, Cerebrum consists of two lobes, i.e., right and left, which are separated, by a deep longitudinal fissure., Each hemisphere has a thick central core of white matter containing, bundles of myelinated axons., Cerebral cortex forms the thin outer layer of grey matter., containing the cell bodies of the neurons., l, , White matter, Cerebral cortex, (grey matter), , Corpus callosum, , Caudate nucleus, , Lateral ventricles, , Putamen, Thalamus, Globus pallidus, Third ventricle, , Subthalamic nucleus, (body of luys), Hypothalamus, , Substantia nigra, (found in midbrain and associated, with the secretion of dopamine), , Transverse section of brain showing white matter,, grey matter and components of basal ganglion, l, , l, , l, , Basal ganglion (or nuclei) These are the scattered masses or, bulges of grey matter, which are submerged into the white matter, (subcortex) of cerebrum., They constitute the five structures namely, caudate nucleus,, putamen, globus pallidus, subthalamic nuclei and substantia, nigra. The main function of basal nuclei is to control and regulate, stereotypic (3D) movements., Corpus striatum It is the structure formed by the association of, caudate nucleus, putamen and globus pallidus. In mammals, it is, present in frontal lobe and both corpora striata are connected with, the help of a nerve fibre band called anterior commissure., Corpus callosum It is the largest bundle of fibres which connect, the two hemispheres of cerebrum. Most of the fibres of corpus, callosum arise from the parts of neocortex of one cerebral, hemisphere and terminate in the corresponding parts of the opposite, cerebral hemisphere. It is a unique feature of mammals., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 335, Neural Control and Coordination, Specialised Regions Present in Cerebral Hemisphere, The cerebral cortex has three principal functions, (a) Receiving sensory input, (b) Integrating sensory information, (c) Generating motor responses., These functions are performed by special areas in cerebrum, which are, described in the figure below, Motor area, (precentral), , Central, sulcus, , Premotor area, (coordination of, complex movements), Frontal area, , Sensory area, (procentral area), Sensory speech area, Wernicke’s area, (speech, understanding), , Motor speech area, (Broca’s motor area), Taste area, Olfactory area, , Auditory area, (centre of hearing), , Visual area (sensory), (centre of sight), , Cerebral hemisphere, , The three major specialised regions of the cerebrum are, (a) The primary motor cortex It occupies a single ridge on each, hemisphere in front of central sulcus., The pathway of voluntary movements carried out by primary, motor cortex is as follows, Conscious, thought, , Stimulation of neurons, in primary motor cortex, Impulse generation, Reaches to, , Muscle contraction, , Transmit impulse, to muscles, , Motor neurons of, spinal cord, , (b) The primary sensory cortex It lies just behind the central, sulcus as a ridge of tissue running parallel to the primary motor, cortex. It is the final destination of many sensory impulses, travelling to the brain. It receives the sensory information from, the body., , www.aiimsneetshortnotes.com
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336, , Telegram @neetquestionpaper, , Handbook of Biology, , (c) Association cortex It consists of large regions of cerebral, cortex where integration occurs. Here, information is, interpreted, made sense of, and acted upon. It also carries out, more complex functions., Neuron of Cerebral Cortex, Cerebral cortex is composed of two major types of neurons, i.e.,, Neurons of Cerebral Cortex, , Pyramidal Cells, , Stellate Cells, They possess spheroidal, cell bodies (soma) having, dendrite projections in all, directions for short distances., , They are tall and conical cells, having their apex pointed towards, the brain surface. They have thick, dendrites with many branches and, small knobby dendritic spines., , Limbic system The medial border of temporal lobe is called limbic, system. It is a loop of cortical structures, surrounding the corpus, callosum and thalamus. Its four major components are hippocampus,, amygdala, septal nuclei and mammillary bodies., Fornix, , Septal Nuclei, , Pathway of nerve fibres, that transmit information, from limbic areas, to mamillary bodies., , Located within septal, areas, associated with, sexual emotions., , Cingulate Gyrus, Together with parahippocampal, gyrus and olfactory bulbs,, it comprises limbic cortex which, modifies behaviour and emotions., , Hippocampus, Mammillary Body, Tiny nucleus, acts as relay, centre, transmits information, to and from the fornix and, thalamus., , Seahorse-shaped structure, located inside temporal lobe,, plays major role in converting, short term memory to long, term memory. It is present as, the curved band of grey matter., , Amygdala, Almond-shaped structure,, associated with normal, emotions like anger, sexual, interest, etc., , Parahippocampal Gyrus, With other structures, it helps, to modify the expression of, emotions such as rage and fright., , Limbic system and its associated structures, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Neural Control and Coordination, 337, (iii) Diencephalon It is the posterioventral part of the brain and, formed by three structures as follows, Diencephalon, Epithalamus, , Optic Thalami, , Hypothalamus, , (forms the roof of diencephalon) (forms the sides of diencephalon) (forms the base of diencephalon), , In case of humans, only two parts of diencephalon are defined, Thalamus includes roof (epithalamus) and upper portion with, medial portions of side walls. It is present just beneath the, cerebrum. It is a relay centre. It receives all sensory inputs, except, for smell and then relays it to the sensory and association cortex., Hypothalamus includes floor along with lower side walls. It is, present beneath the thalamus. It consists of many groups of nerve, cells called nuclei which control a variety of autonomic functions, and helps to maintain homeostasis (such as appetite, body, temperature, blood pressure, etc). It also regulates the functioning of, pituitary gland., l, , l, , Anterior Choroid Plexus, Formed by the association of, epithalamus and piamater., , Optic Chiasma, Formed by the crossing, of optic nerves which, come from the eyes, in front of hypothalamus., , Pineal Body, Associated with, epithalamus roof, with the help of, pineal stalk., , Infundibulum, Stalk which connects, hypothalamus and, pituitary gland (or, hypophysis)., , Hypophysis, Endocrine gland, which secretes, hormones., , Posterior Choroid, Plexus, Produces the, cerebrospinal fluid in, the ventricles of the, brain., Mammilary Body, Pair of rounded eminences, present behind the infundibulum., , Components of diencephalon, , 2. Midbrain, The midbrain contains optic lobes. These lobes are two in case of frog, and called as corpora bigemina (hollow structures)., In case of humans, they are four in number and called as corpora, quadrigemina (solid structures)., , www.aiimsneetshortnotes.com
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338, , Telegram @neetquestionpaper, , Handbook of Biology, , In humans, the four lobes are defined in two pairs as superior and, inferior colliculus., Superior Colliculus, Associated with vision, , Inferior Colliculus, Associated with, auditory functions, , Crus Cerebri, Two bundles of fibres, lie on lower surface of, midbrain, connects forebrain and hindbrain,, contains dopamine secreting nuclei called, substantia nigra., , Posterior view of brain showing the components of midbrain, , The functions performed by superior and inferior colliculi are originally, taken up by cerebrum. Crus cerebri functions to relay impulses back, and forth between the cerebrum, cerebellum, pons and medulla., , 3. Hindbrain, It basically consists of cerebellum (metencephalon), medulla oblongata, (myelencephalon) and pons Varolii. Collectively, these three structures, form the brain stem., (i) Cerebellum, It is the second largest part of brain and considered as small brain or, little cerebrum. From birth with the age of 2 yrs, it grows faster than, the rest of the brain., It consists of 2 cerebellar hemispheres with a central worm-shaped, vermis. The various structural components of cerebellum are as follows, (a) Arbor vitae It is the tree of life present in the internal region, of cerebellum. It is the profuse ramifications of white matter, into the grey matter. Externally, its surface contains gyri and, sulci., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Neural Control and Coordination, 339, (b) Cerebellar peduncles These are the bundles of fibres, connecting the cerebellum with the underlying brainstem. On, the basis of their position, they are of three types, l, Caudal cerebellar peduncle Connects cerebellum with, medulla, contains afferent and efferent axons, also called, restiform bodies., l, Middle cerebellar peduncle Connects cerebellum with, pons, contains only afferent axons, also called branchia, points., l, Rostral cerebellar peduncle Connects cerebellum with, midbrain, contains predominantly efferent axons, also called, branchia conjunctiva., (c) Cerebellar cortex It is the surface grey matter of the, cerebellum. It consists of three layers as follows, l, Molecular layer Most superficial, consisting of axons of, granule cells and dendrites of Purkinje cells., l, Purkinje cell layer Middle layer, consisting of a single, layer of large neuronal cell bodies of Purkinje cells., l, Granule cells layer Deepest layer next to white matter, consisting of small neurons called granule cells., Cerebellar cortex also contains various cell types as follows, l, Purkinje cells These are the only output neuron from the, cerebellar cortex; it utilises the neurotransmitter GABA, (Gamma Amino Butyric Acid) to inhibit neurons in deep, cerebellar nuclei. These flask-shaped Purkinje cells are, considered as one of the largest and most complex neurons., l, Granule cells These are the intrinsic cells of cerebellar, cortex; they use glutamate as an excitatory transmitter; they, excite Purkinje cells via axonal branches called parallel, fibres., l, Basket cells These are the inhibitory interneurons, they, utilise GABA to inhibit Purkinje cells., Functions, Maintenance of balance and posture., Coordination of voluntary movements by modulating timing and, force of muscle groups., Motor learning through adaptation and fine-tuning in solving a, motor problem., Cognitive functions associated with language., l, , l, , l, , l, , www.aiimsneetshortnotes.com
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340, , Telegram @neetquestionpaper, , Handbook of Biology, , (ii) Pons Varolii, It is present at the axis of brain in front of cerebellum below the, midbrain and above medulla oblongata. It is considered as a link, between upper portion of brain and spinal cord through medulla, oblongata., It contains nerve fibres which form a bridge called pons bridge in, between the two cerebellar hemispheres., Function, It contains pneumotoxic centre and helps in regulating breathing, movements., (iii) Medulla Oblongata, It is the triangular part of the brain. Its roof is associated with, overlying piamater to form the posterior choroid plexus., Functions, , (i) It receives and integrates signals from spinal cord and sends, them to cerebellum and thalamus., (ii) It regulates heart rate, blood pressure, swallowing, salivation,, vomiting and some other involuntary movements., , 321, , Cerebellar Peduncles, , Midbrain, Anterior lobe, Arbor vitae, Superior cerebellar, peduncle, , Pons, Cerebellar nucleus, Cerebellar cortex, , Middle cerebellar, peduncle, , Posterior lobe, , Inferior cerebellar, peduncle, , Choroid plexus of, the fourth ventricle, Medulla, oblongata, , Spinal cord, , Lateral view of brain showing the components of hindbrain, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Neural Control and Coordination, 341, Brain Ventricles, The ventricles consist of four hollow, fluid-filled spaces inside the, brain. These are as follows, 1 Two Lateral Ventricle, Also called paracoel, lies, inside each cerebral, hemisphere., Septum Pellucidum, Thin membrane that, separates the lateral, ventricles anteriorly., , Interventricular Foramen, Also called foramen of monro,, connects lateral ventricle with, diocoel,, , Cerebral Aqueduct, Also called aqueduct of, sylvius or iter, connects, third and fourth ventricle, (along with optocoel)., , 2 Third Ventricle, Also called diocoel, consists of, a narrow channel between the, cerebral hemispheres through, the area of the thalamus., , Central Canal, Central region of, spinal cord., , 3 Fourth Ventricle, It is continuous with the central, canal of the spinal cord,, contains 3 openings on its, roof-foramina of Luschka, (on 2 lateral sides) and a, median foramen of Magendie., , Ventricles of brain, , Cerebrospinal Fluid (CSF), It is the watery liquid that is found between the inner and outer layers, of meninges. It also fills the internal cavities in the brain and spinal, cord. CSF is secreted by anterior and posterior choroid plexus. It is, similar in composition to blood plasma and interstitial fluid., Functions of CSF, (i) Protection of brain and spinal cord CSF protects the, delicate brain and spinal cord by providing shock-absorbing, medium. It acts as cushion jolts to the central nervous system., (ii) Buoyancy to the brain Since, the brain is immersed in the, CSF, the net weight of the brain is reduced from about 1.4 kg to, about 0.18 kg. Thus, the pressure at the base is reduced., (iii) Excretion CSF carries harmful metabolic wastes, drugs and, other substances from the brain to the blood., (iv) Detection of infections As CSF bathes the CNS, examining, small amounts of CSF can provide physicians a means of, detecting infections in the brain, spinal cord and meninges., Samples of CSF are obtained by inserting a needle between 3rd, and 4th lumbar vertebrae (lumbar puncture)., , www.aiimsneetshortnotes.com
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342, , Telegram @neetquestionpaper, , Handbook of Biology, , Spinal Cord, It is the part of dorsal nerve cord present in continuation with brain. It, lies in the neural canal of the vertebral column. Like brain, it is also, surrounded by 3 meninges namely piamater (inner), arachnoid, membrane (middle) and duramater (outer)., Dorsal Horn of, Grey Matter, , Middle Dorsal Septum, Divides the spinal cord, into left and right halves., , Contains neurons that, process the sensory, signals (i.e., sensory, neurons)., , Lateral Funiculus, Lateral white column, of the spinal cord lying, on either sides between, the dorsal and ventral roots., , White Matter, , Grey Matter, , Peripheral region containing, sensory and motor neurons., , Internal, butterfly-shaped, region containing cell, bodies of neurons., , Central Canal, , Ventral Horn of Grey Matter, , Central to grey matter,, anatomic extension of, brain ventricles, contains, CSF., , Contains somatic, efferent motor neurons., , TS of spinal cord, , Horns These are the projections of grey matter into the white matter, and their presence gives a butterfly appearance to the TS of spinal cord., Conus terminalis or medullaris It is the termination point of the, spinal cord. In humans, this point is situated in L-2 region., Filum terminale It is a long slender filament at the end of the, spinal cord in the caudal region. It consists of vascular meninges,, i.e., piamater or pia arachnoid matter. It anchors the spinal cord, within the vertebral column., In the TS of spinal cord, certain tracts are also seen. These tracts are, meant for the vertical communication of spinal cord with brain.These are, (i) Ascending tracts They take information to the brain., (ii) Descending tracts They bring information from the brain., , Peripheral Nervous System (PNS), The PNS transmits information to and from the CNS and plays a, major role in regulating movements and internal environment., It consists of cranial and spinal nerves., Cranial nerves They originate in the brain and terminate mostly in, the organs of the head and upper body. Mammals have 12 pairs of, cranial nerves., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Neural Control and Coordination, 343, Cranial Nerves in Humans, Types of Cranial, Nerves, , From, , To, , Nature, , I. Olfactory, , Olfactory, lobe, , Olfactory epithelium, , S, , II. Optic, , Optic, chiasma, , Eye retina, , S, , III. Oculomotor, , Crus, cerebrum, , Four muscles of eyeball, iris,, ciliary body, , Mo, , IV. Trochlear (smallest, nerve), , Midbrain, , Superior oblique muscles of eye, , Mo, , V. Trigeminal (largest, nerve), , Pons, Varolii, , Mix, , V1- Ophthalmic, , Eye, eyelids, snout, , S, , V2- Maxillary, , Upper jaw, cheeks and lower, eyelids, , S, , V3- Mandibular, , Lower jaw, lip, tongue, external, ear, , Mix, , Lateral rectus muscles of eye, , Mo, , VI. Abducens, , Pons, , VII. Facial, , Pons, , Mix, , VII1- Palatinus, VII 2- Tympani, , Palate, , S, , Tongue, salivary gland, taste, buds, , S, , VII 3- Hyomandibular, , Lower Jaw, pinna, neck, hyoid, , Mix, , VIII. Auditory, , Medulla, , VIII1- Vestibular, VIII 2- Cochlear, IX. Glossopharyngeal, , S, , Cochlea, , S, , Medulla, , IX1- Lingual, IX2- Pharyngeal, X. Vagus, , S, Internal ear, , Mix, Tongue, pharynx, , Mix, , Pharynx, salivary gland, , Mix, , Medulla, , X1 - Superior laryngeal, , Laryngeal muscles, , Mix, , X2 - Recurrent laryngeal, X3- Cardiac, X4 - Pneumogastric, , All muscles of larynx, Cardiac muscles, Lungs, oesophagus, stomach,, ileum, Diaphragm, , Mo, Mo, Mo, Mix, , X5- Depressor, XI. Spinal accessory, , Medulla, , Pharynx, larynx, neck, shoulder, , Mo, , XII. Hypoglossal, , Medulla, , Tongue, hyoid, , Mo, , S — Sensory, Mo — Motor, Mix — Mixed., , www.aiimsneetshortnotes.com
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344, , Telegram @neetquestionpaper, , Handbook of Biology, , Spinal Nerves They originate in the spinal cord and extend to the, different body parts below the head. There are 31 pairs of spinal, nerves in humans. All spinal nerves contain axons of both sensory and, motor neurons., , Cervical, Nerves, C1-C8, , Thoracic, Nerves, T1-T12, , 1, 2, 3, 4, 5, 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, , Lumbar, Nerves, L1-L6, Sacral, Nerves, S1-S6, , 12, 1, , Cerebral Plexus, , Branchial Plexus, , Spinal Cord, , End of, Spinal, Cord, , Lumbar Plexus, , 2, 3, 4, 5, 1, 2, 3, 4, 5, , Cauda, Equina, Sacral plexus, Filum, Terminale, , Coccygeal, Nerves, (1 pair), , Spinal nerves in human, , Autonomic Nervous System (ANS), The ANS regulates the internal environment of the animal’s body by, controlling smooth and cardiac muscles and other involuntary actions., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Neural Control and Coordination, 345, Autonomic Nervous System, Sympathetic Nervous System, , Parasympathetic Nervous System, , Vasoconstriction in general and vasodilation, (brain, heart, lungs and skeletal muscles), , Vasodilation of coronary vessel, , Dilates pupil, , Constricts pupil, , Increases lacrimal gland’s secretion, , Inhibits lacrimal gland’s secretion, , Inhibits salivary and digestive glands, , Stimulates them, , Accelerates heartbeat, , Retards heartbeat, , Dilates trachea, bronchi, lungs, , Constricts these organs, , Inhibits gut peristalsis, , Stimulates gut peristalsis, , Contracts anal sphincter, , Relaxes anal sphincter, , Relaxes urinary bladder, , Contracts urinary bladder, , Reflex Action, It is a spontaneous automatic mechanical response to a stimulus, involuntarily (without the will)., It is of following types, Simple Reflexes, These are present in an organism, starting from birth., Also called unconditioned/inborn, reflexes, e.g., sweating, breathing,, peristalsis, etc.,, , Acquired Reflexes, These develop in an organism, after birth through learning,, experience, etc., Also called, conditioned reflexes, e.g., writing,, reading, driving a vehicle, etc., , Reflex Action, , Spinal Reflexes, These are controlled by spinal cord., , Cranial Reflexes, These are controlled by brain., , Reflex Arc, It is the pathway covered by nerve impulses (generated at the receptor, due to the stimulus) to reach the effector organ during a reflex action., It has following five components, (i) Receptor It is a cell/tissue/organ, which receives an external, or internal stimulus, e.g., skin, eye, ear., (ii) Sensory/Afferent nerve fibres They carry the sensory, nerve impulses generated by the receptor to the central nervous, system., , www.aiimsneetshortnotes.com
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346, , Telegram @neetquestionpaper, , Handbook of Biology, , (iii) Part of central nervous system It may be spinal cord or, brain or ganglion., (iv) Motor/Efferent nerve fibres These carry the motor nerve, impulse generated in the CNS to the specific effector organs., (v) Effector organ It may be organ/muscle/gland which on being, activated by a motor nerve impulse, helps to deal with the, stimulus., Sensor, , Excitatory interneuron, , Thermal pain, receptor in finger, , Ascending, pathway, to brain, , Afferent, pathway, , Stimulus, Inhibitory, interneuron, Biceps, (flexor), , Efferent pathway, Triceps, (extensor), , Integrating Center, Spinal cord, , Effector, Arm muscles, , Response, , Reflex action and reflex arc, , Importance of Reflex Arc, (i) Controls a number of body activities., (ii) Response to harmful stimulus is fast., (iii) Response to stimulus is accurate and useful., (iv) Coordinate body activities., , Nerve Impulse, It may be defined as wave of depolarisation of the membrane of the, nerve cell. It travels along a neuron or across a synapse (junction),, between one neuron and another, or between a neuron and an effector,, such as a muscle or gland., , Membrane Theory of Nerve Impulse, This theory was proposed by English neurophysiologists Hodgkin and, Huxley in the late 1930s. This theory states that electrical events in, the nerve fibre are governed by the differential permeability of its, membrane to sodium and potassium ions and that these permeabilities, are regulated by the electric field across the membrane., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Neural Control and Coordination, 347, The interaction of differential permeability and electric field makes a, critical threshold of charge essential to excite the nerve fibre., According to this theory, the process of nerve impulse conduction is, divisible into two main phases, i.e., resting membrane potential of, nerve and action membrane potential of nerve., , Membrane Potential, Positive Over Potential, , Resting Membrane Potential, (Polarised state), , It is the small action potential, generated following the, termination of spike. It consists of, an initial negative deflection, followed by a positive deflection, both being of smaller amplitude, than action potential Represented, by ‘d’ in the graph below., , It is about 90 mV for a resting large, resting nerve fibre, i.e., potential inside, the fibre is 90 mV more negative than, the potential in the extracellular fluid on, the outside of the fibre. Represented, by ‘a’ in the graph below., , Membrane, Potential, , Action Membrane Potential, It is responsible for transmitting the nerve, signals. Action potential is generated due, to rapid changes in membrane potential, when a threshold stimulus is applied. The, membrane potential changes from, negative to positive., , Depolarisation Stage, , Repolarisation Stage, , Normal 90 mV polarised stage is, lost, potential rises rapidly to, positive direction due to, tremendous inflow of Na+ ions, inside the axion. Represented by, ‘b’ in the graph below., , Caused due to excessive diffusion of, K+ ions to exterior which establish, normal negative resting membrane, potential. Represented by ‘c’ in the, graph below., , 60, Membrane potential in mV, , 40, 20, 0, –20, , b, , c, , –40, –60, –80, a, , a, , –90, , d, , 0, 1, , 2, , 3, , 4, , 5, , Time in s–1, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 348, , Handbook of Biology, , Causes of Membrane Potential, Small Subunit, , 1, Na, , +, , (+61 mV), , Electrogenic pump, (Na+ – K+ pump), , Diffusion through, (Na+ – K+ Leak Channels), K, , +, , β, , ECF, , 2, 2K, , +, , 2, , +, K (–86 mV), (–94 mV), , Causes of, Membrane, Potential, , Contribution of K+ ions to, , 3, , 3, 2, , Cytoplasm, ATP, , membrane potential is more than, Na+ ions due to their greater, permeability. They contribute about, –84 mV to membrane potential., , +, 3Na, 4, ADP+Pi, , 5, , 1, Large Subunit of, carrier protein, , For every 3 Na+ ions to be, transported outside, 2K+ ions are, imported and ATP is converted to, ADP. This pump contributes about, –4mV to membrane potential., , Voltage Gated Channels, , 3 Voltage gated Na+ Channels, , 4, , (with 2 gates ), , Activation Gate, Remains closed during resting, stage, conformational, activation is brought about by, shift in potential to positive, value (–90 mV to +35 mV)., Their opening allows the entry, of Na+ ions into the cell., Inactivation Gate, Remains opened during resting, stage (–90 mV) due to potential, change they begin to close but, with slower face. Their closure, recovers the resting stage., , Na, , +, , Voltage gated K+ Channels, (with 1 gate only), , K+Channel, It remains closed, during resting stage, (–90 mV) and K+ ion, movement across the, membrane is hindered., Membrane potential, changes bring about, its conformational, change, thus opening, it. K+ions then diffuse, outside the membrane., , •, K+, , Causes of membrane potential (1) and (2) for resting potenial, (3) and (4) for action potential, , Calculation of Nernsth Equation and Nerve Potential, The potential level across the membrane that will exactly prevent net, diffusion of an ion in either direction through a membrane is called, Nernst potential of that particular ion. Its magnitude can be, determined by the ratio of ion concentration on the two sides of the, membrane., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Neural Control and Coordination, 349, The following equation called Nernst equation is used to calculate, the Nernst potential for any univalent ion at normal body, temperature of 37°C., Concentration inside, EMF (milli volts) = ± 61 log, Concentration outside, When using this formula, it is assumed that the potential outside the, membrane always remains exactly at zero and Nernst potential is, calculated in the potential membrane., Diffusion potential occurs when membrane is permeable to, several different ions. In this condition, the diffusion potential that, develops, depend upon three factors, (i) The polarity of electric charge of each ion., (ii) The permeability of membrane (P) of each ion., (iii) The concentration (C) of respective ions on the inside (i) and, outside (o) to the membrane., Thus, the following formula called the Goldman equation or, Goldman-Hodgkin-Katz equation gives the calculated membrane, potentials when the Na + , K + , Cl− ions are involved. The equation is, EMF (milli volts), = − 61 log, , C[Na + ]i . P[Na + ]i + C[K + ]i P[K + ]i + C[Cl− ]O. P[Cl− ]O, C[Na + ]O . P[Na + ]O + C[K + ]O . P[K + ]O + C[Cl− ]i . P[Cl− ]i, , Here, C is the concentration of respective ion, P is the partial pressure, and permeability of concerning ion, i represents inside, o represents, outside., , Synapse, It is formed by the membranes of a pre-synaptic neuron and a, post-synaptic neuron which may or may not be separated by a gap, called synaptic cleft. There are two types of synapses, (i) At electrical synapse, the membranes of pre and post-synaptic, neurons are in very close proximity. Electrical current can flow, directly from one neuron to the other, across these synapses., Impulse transmission across an electrical synapse is always, faster than that across a chemical synapse. Electrical synapses, are rare in our system., (ii) At chemical synapse, the membranes of pre and post-synaptic, neurons are separated by a fluid-filled space called as synaptic, cleft., , www.aiimsneetshortnotes.com
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350, , Telegram @neetquestionpaper, , Handbook of Biology, , Conduction Through Synaptic Cleft, The pre-synaptic neuron synthesises the neurotransmitter and, packages it in synaptic vesicles which are stored in the neuron’s, synaptic terminals. Hundreds of synaptic terminals may interact with, the cell body and dendrites of a post-synaptic neuron., When an action potential reaches a synaptic terminal, it depolarises, the terminal membrane, opening the voltage-gated calcium, channels in the membrane. Calcium ions (Ca 2+ ) then diffuse into the, terminal and the rise in Ca 2+ concentration in the terminal causes, some of the synaptic vesicles to fuse with the terminal membrane,, releasing the neurotransmitter., The neurotransmitter diffuses across the synaptic cleft, a narrow gap, that separates the pre-synaptic neuron from the post-synaptic neuron., The released neurotransmitter binds to the specific receptors, present, on the post-synaptic neuron. This binding open the ion channels, allowing the entry of ions which can generate a new potential in the, post-synaptic neuron., Axon, Direction of, impluse, Presynaptic, knob, , Synaptic, vesicles, , Mitochondrion, , Pre-synaptic, membrane, , e, , Synaptic cleft, , Ach Ache, , Neurotransmitter, molecules, , tyl, Ace, , n, oli, , ch, , Receptor proteins, Postsynaptic, membrane, , Transmission of nerve impulse at a chemical synapse, , Neurotransmitters, These are chemical messengers secreted by the axon terminals for, transmitting impulses to the next neuron. At most synapses,, information is passed from the transmitting neuron (pre-synaptic cell), to the receiving cell (post-synaptic cell) by neurotransmitters. Each, neurotransmitter binds to its own group of receptors. Some, neurotransmitters have many different receptors, which can produce, different effects in the post-synaptic cell., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Neural Control and Coordination, 351, Various kinds of neurotransmitters are listed below, (i) Acetylcholine is a common neurotransmitter present in the, neuromuscular junctions, voluntary neural synapses, synapses, of pre-ganglionic nerve fibres, synapses of post-ganglionic, parasympathetic nerve fibres. Cholinergic nerve fibres release, acetylcholine. It has excitatory effect on the skeletal muscles, and excitatory or inhibitory effect at other sites., (ii) Nor-epinephrine (nor-adrenaline) is formed at synapses and, neuromuscular junctions of the post-ganglionic sympathetic, nerve fibres. The nerve fibres are called adrenergic. It has, excitatory or inhibitory effects., Peripheral nervous system generally uses acetylcholine,, nor-adrenaline and adrenaline., (iii) Glycine, Dopamine and Gamma Amino Butyric Acid, (GABA) are inhibitory transmitters., (iv) Glutamate is excitatory in function., (v) Serotonin inhibits pain pathways of spinal cord. It generally, controls mood and induces sleep., , Sense Organs, The human body contains receptors that monitor numerous internal, and external stimuli essential for homeostasis and our well-being., These receptors are located in the skin, internal organs, muscles, etc., They detect stimuli that gives rise to general senses like pain,, pressure, etc., The human body is also endowed with five additional special senses,, i.e., taste, smell, sight, hearing and balance., , www.aiimsneetshortnotes.com
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352, , Telegram @neetquestionpaper, , Handbook of Biology, , General and Special Senses, Sense, , Stimulus, , General senses, , Special senses, , Receptor, , Pain, , Naked nerve endings, , Light touch, , Merkel’s discs; naked nerve endings around hair, follicles; Meissner’s corpuscles; Ruffini’s, corpuscles, Krause’s end-bulbs, , Pressure, , Pacinian corpuscles, , Temperature, , Naked nerve endings, , Proprioception, , Golgi tendor organs; muscle spindles; receptors, similar to Meissner’s corpuscles in joints, , Taste, , Taste buds, , Smell, , Olfactory epithelium, , Sight, , Retina, , Hearing, , Organ of Corti, , Balance, , Crista ampularis in the semicircular canals,, maculae in utricle and saccule, , Receptors in humans, involved in the general and special senses fall, into five categories as follows, Receptors, Thermoreceptors, , Chemoreceptors, , Mechanoreceptors, , Activated by heat, and cold., , Activated by chemicals, in the food, air,, blood, etc., , Activated by mechanical, stimulus like touch, or pressure., , Photoreceptors, , Nociceptors, , Activated by light., , They are pain receptors, activated by pinching,, tearing or burning., , Based on kinds of stimulus, the sensory receptors fall into following two, categories, (i) Exteroceptors These receive external stimuli., (ii) Interoceptors These receive internal stimuli coming from the, internal body organs, changes in muscles and joint movements., , The Visual Sense–The Eye, Human eye is one of the most extraordinary product of evolution. It, contains a patch of photoreceptors that permit us to perceive the, diverse and colourful environment., , www.aiimsneetshortnotes.com
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www.aiimsneetshortnotes.com, , Vitreous Chamber, Space between lens and retina,, contains vitreous humor which, maintains the intraocular pressure, and shape of eyeball, it is, transparent and gel-like., , Optic Disc (Blind spot), Devoid of receptor cells,, optic nerve arises, from this spot., , Optic Nerve, Transmits impulses from, the retina to the brain., , Fovea Centralis, Shallow depression in the middle of, yellow spot, contains cells; nerve, fibres from light-sensitive cells leave, the eyeball here only., , Retina, Also called nervous tunic, contains, neural and sensory layers, contains, photoreceptor cells, i.e, rods and, cones, converts light to nerve., , Choroid, Contains numerous blood vessels, provides, nourishment to retina,, contains pigmented cells that absorb light., , Lens, Transparent, flexible structure,, attached to ciliary body, focuses, image on retina., , Ora Serrata, Special structure which demarcates, the sensitive part of retina, from its neurosensory part., , Posterior Chamber, Located between the iris, and lens., , Sclera, Outermost fibrous layer, contains, collagen fibres, protects and, maintains the shape of eyeball., , Iris, Coloured portion of eye, contains, circular and radial muscles that, regulate the diameter of pupil., , Pupil, Present at the centre of iris, it opens, and closes reflexively in response to, light intensity., , Cornea, White portion of the eye, transparent,, lacks blood supply and absorbs O2, from air, helps to focus light entering, the eye., , Anterior Chamber, It is located between the cornea and, iris, contains aqueous humor, secreted by ciliary body which, provides O2 to the lens., , Ciliary Body, Contains smooth muscle fibres that, control the shape of lens. It consists of, two muscles, circular and meridional., , Suspensory Ligaments, Responsible for the maintenance of, the curvature of eye., , Telegram @neetquestionpaper, Neural Control and Coordination, 353, , Anatomy of Eye
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354, , Telegram @neetquestionpaper, , Handbook of Biology, , Various layers of retina are as follows, Choroid, , Layer of Rods and Cones, Rods are sensitive to, dim light; contain rhodopsin;, cones are sensitive to bright, light, contain iodopsin,, cyanopsin and porpyrosin., , Pigment Cell Layer, Consists of pigment, cells-retinal and opsin., Rod, , Outer, segment, Inner, segment, Nucleus, of cone, Nucleus, of rod, , External Plexiform Layer, contain nerve fibres of, rods and cones which, synapse with the dendrites, of bipolar neurons., , Cone, , External Nuclear, Layer Contain cell, bodies and nuclei of, rods and cones., , Horizontal, neuron, , Gliocyte, , Bipolar, neuron, , Internal Plexiform Layer, Contain synapsing nerve, fibres of bipolar, horizontal, and amacrine neurons., , Layer of Optic, Nerve Fibres, Contain axons of, ganglion cells that, form optic nerve., , Pigmented, processes, , Internal Nuclear, Layer contains cell, bodies of bipolar,, horizontal and, amacrine neurons., , Amacrine, cell, , Layer of Ganglion, Cells contain cell, bodies of ganglion, cells., , Ganglion, cell, Optic, nerve, fibres, , Vitreous humour, , Layers of retina, l, , l, , l, , Rhodopsin pigment (visual purple) is formed by combining retinene, with scotopsin in the presence of energy., Iodine is the main constituent of iodopsin pigment (visual violet)., On the basis of sensitivity to a particular colour, the cones are of, three types., Erythrolable Cones, Sensitive to red colour., , Chlorolable Cones, Sensitive to green colour., , Cone, Cells, , Cyanolable Cones, Sensitive to blue colour., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Neural Control and Coordination, 355, Rest of the colours are detected by the combination of these basic, colours., , Few Important Terms Related to Eye, (i), , (ii), , (iii), (iv), (v), , Uvea It is the name given to the vascular layer (tunic) of the eye which, comprises posterior choriodeal, intermediate ciliary body and an anterior iris,, perforated with pupil., Canal of Schlemm Aqueous humor secreted by ciliary body is continuously, drained to anterior part of eye through this canal. Its blockage may cause, glucoma or kala motia., Tapetum Lucidum It is the refractive layer of guanine particles in the iris of, many mammals and elasmobranch fishes., Tapetum Fibrosum It is the tapetum containing glistening white fibres of, tendon type in marsupials, elephant, whale and hoofed mammals., Tapetum Cellulosum It is the tapetum composed of cellulose like, crystalline material instead of guanine in carnivore mammals, seals and lower, primates., , Accessory Organs of the Eye, The eye is a delicate organ which is protected by several structures,, i.e., eyebrows, eyelids, eyelashes, lacrimal apparatus, etc., Lacrimal Gland, Situated on the lateral sides of eye, in frontal bones behind suborbital, margins, composed of secretory, epithelial cells, secrete tears, water, antibodies and lysozyme, (a bactericidal enzyme)., , Eye ball, Eyelid Margins, Contains modified sebaceous, gland called Meibomian glands, (tarsal glands), These glands, secrete oily material which keeps, the eyes wet and delays, evaporation of tears., , Eye Brows, 2 arched ridges of suborbital, margins of the frontal, possess, numerous hairs which protects, the eyes from sweat, dust, etc., , Lens, Conjunctiva, Transparent membrane, lines the, eyelids, consists of highly vascular, columnar epithelium, protects the, cornea and front of the eye., , Eyelids, Also called palpebrae, movable, folds of tissue, possess eyelashes, (short curved hairs)., , Accessory structures of human eye, , www.aiimsneetshortnotes.com
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356, , Telegram @neetquestionpaper, , Handbook of Biology, , Mechanism of Vision, Light rays from, outside, , Focus on retina, Light induces dissociation, of retinal and opsin, , Potential difference is, generated in photoreceptor, cells., Action potential is generated, in ganglionic cells through, bipolar neurons., Image is recognised, , Structure of opsin changes, , Action potential is transmitted to, visual cortex in occipital lobe by, optic nerve., Neural impulses are analysed, , Accommodation It is the automatic adjustment in the curvature of, lens as it focuses on different objects., Accommodation for Distant Objects, , Accommodation for Near Objects, , Retina, , Retina, , Focal point, , Focal point, , Light rays are parallel from the distant, objects when they strike the eye., , Light rays are divergent from the near, objects when they strike the light., , Lens is pulled thin., , Lens is allowed to shrink., , Suspensory ligament is stretched tightly., , Suspensory ligament’s tension is relaxed., , Ciliary muscles are stretched., , Ciliary muscles are contracted., , Binocular vision When both the eyes can be focused, simultaneously on a common object, it is called binocular vision, e.g.,, humans., Monocular vision In this vision, eye focuses its own object and both, the eyes cannot focus on one object, e.g., rabbit., , Common Diseases of the Eye, (i) Myopia It occurs due to the convexity of lens or longer eyeballs,, which results in image of distant objects being formed in front of, the retina. It can be corrected by wearing concave lenses., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Neural Control and Coordination, 357, (ii) Cataract An eye disease generally occurring in older people, (lens becomes opaque). It can be treated by laser treatment,, removing opaque lens and wearing spectacles., (iii) Hypermetropia Also called long-sightedness. The image of, nearer objects becomes blurred. It can be corrected by wearing, convex lenses., (iv) Presbyopia The loss of elasticity in the eye lense occurs so that, near objects are not correctly visible. It can be corrected by, bifocal lenses., , Human Ear-Organ of Hearing and Balance, It is an organ of special senses. It serves two functions; it detects sound, and enables us to maintain balance., , Anatomys of Ear, 6 Incus, 5 Malleus, Middle,anvilOuter hammershaped bone., shaped bone, lies, next to tympanum., 1 Auricle (pinna), Irregularly-shaped piece of, cartilage covered by skin., 2 External Auditory Canal, Short tube that transmits, airborne sound waves to the, middle ear, lined by, ceruminous (wax) glands., 3 Earlobe, Flap of skin, that hangs down, from the auricle., 4 Tympanum, Also called eardrum, its central, part is umbro, vibrates when, struck by sound waves, separates, external ear and middle ear., , 7 Stapes, Inner smallest bone, lies next to oval windows., 8 Semicircular, Canals Three ring-like, structures set at right, angles to one another., , 9 Vestibule Bony chamber, lying between cochlea, and semicircular canals., Contains receptors that, respond to body position, and movement., 10 Cochlea Snail shell-shaped, structure; contains hearing, receptors., Fenestra Ovalis, Opening of the inner ear,, closed by the membrane., , Human Ear: (1), (2), (3), (4) = External ear; (5), (6), (7) = Middle ear;, (8), (9), (10) = Internal ear, , www.aiimsneetshortnotes.com
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358, , Telegram @neetquestionpaper, , Handbook of Biology, , Structure and Function of Cochlea, The cochlea is a hollow structure containing 3 fluid-filled canals, sound, receptors (organ of Corti) and a basilar membrane., Tectorial Membrane, , Scalae Vestibuli, , Overhangs the sensory hair in, the scala media, determines, the patterns of vibration of, sound waves., , Upper canal; filled, with perilymph, , Reissner’s Membrane, Upper membrane of, scala media., , Scala Media, Middle canal, filled with, endolymph., , Basilar Membrane, Lower membrane of scala, media, bears organ of, Corti., , Organ of Corti, Receptor for sound,, contains numerous hairs, and various cell types., , Scala Tympani, Lower canal, filled, with perilymph., , Cross-section through the cochlea, , Function It is the main organ of hearing which converts the fluid, waves to nerve impulses., The Vestibular Apparatus, It consists of two parts-the semicircular canals and the vestibule. Both, are involved in proprioception., The semicircular canals The three semicircular canals are filled, with a fluid (endolymph). These are anterior, posterior and lateral, semicircular canals or ducts., Semicircular Canals, Fluid-filled canals, detect head movements., Lateral Posterior, Anterior, , Utricle, Dorsally placed structure, to which all the, semicircular canals are, connected, contains, maculae., , Ampulla, Swollen ends of the semicircular, canals, contains crista which, further contains sensory and, supporting cells, crista which is, involved in dynamic equilibrium., , Saccule, Ventrally placed structure, joined with, utriculi by a narrow utriculosaccular, duct, contains maculae., Cochlea, It is the major part associated with, hearing., , Membranous labyrinth of internal ear, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Neural Control and Coordination, 359, Maculae It is concerned with the static equilibrium and responds to, linear acceleration and tilling of the head., , Mechanism of Hearing, Sound waves from, external source., , Reach to tympanic, membrane., , Ear ossicles amplify the sound, waves and transform them into, shorter and powerful movements., , Vibration of tympanic membrane, transports sound waves to ear ossicles., , Powerful waves reach the fluid, that fills the cochlea., , Pressure waves cause the, basilar membrane to vibrate., , All these changes stimulate, dendrites at the base of hair, cells and a nerve impulse is, generated., , Vibrations stimulate hair cells of, organ of Corti and contract the, tectorial membrane., , Impulse travels to auditory, area of brain via vestibulocochlear, nerve., , Sound is detected by the brain., , Common Diseases of the Ear, (i) Meniere’s syndrome It is a hearing loss due to the pathological, distension of membranous labyrinth., (ii) Tympanitis It is due to the inflammation of eardrum., (iii) Otalgia Pain in the ear., (iv) Otitis media Acute infection in the middle ear., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 22, Chemical, Coordination and, Integration, Glands, They are the group of cells that are specialised for the secretion of a, particular substance. They can be classified as follows, , Types of Glands, 1. Exocrine glands The secretion of these glands are carried by, the ducts to a particular organ, e.g., salivary glands, liver, etc., 2. Endocrine glands These glands do not possess ducts and they, pour their secretions directly into the blood, e.g., hypothalamus,, thyroid, etc., (i) Holocrine glands They secrete only hormones, e.g., thyroid,, adrenal, etc, (ii) Heterocrine glands They have dual functions, i.e.,, secretion of hormones and other physiological functions, e.g.,, testes, pancreas, etc., , Hormones (Bayliss and Starling; 1903), These are the chemical substances that are produced or released by, cells or group of cells that form the endocrine (ductless) glands., Target cells are the cells affected by a hormone. These target cells are, selective or exclusive to a hormone due to the presence of protein, receptors on them., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 361, , Chemical Coordination and Integration, , Types of Hormones, (i) Hormones fall into two broad categories, (a) Tropic hormones These hormones stimulate other, endocrine glands to produce and secrete hormones,, e.g., Thyroid Stimulating Hormone (TSH) produced by, pituitary gland stimulates the release of thyroxine, hormone from thyroid gland. Thyroxine in turn stimulates, metabolism in many types of body cells. Thus, TSH is a, tropic hormone (thyroxine is a non-tropic hormone)., (b) Non-tropic hormones These hormones stimulate vital, cellular processes including metabolism, but do not, stimulate the release of other hormones, e.g., prolactin, secreted by anterior pituitary stimulates the production of, milk in a woman’s breast tissue., (ii) According to their chemical composition, hormones can be, classified into following groups, (a) Steroid hormones Derivative of cholesterol, e.g.,, aldosterone, cortisol, sex corticoids, oestrogen, etc., (b) Proteins and peptide hormones Largest group of, hormones, they are the long chains of amino acids,, e.g., insulin, hCG, hypothalamic hormones, GH, etc, (c) Amine hormones Smaller molecules derived from, amino acid tyrosine, e.g., thyroxine, catecholamines, etc., (iii) Local hormones These are secreted by the cells, but not by, glands and widely dispersed in the body. These are considered, as tissue hormones or non-endocrine hormones., Different types of local hormones are as follows, (a) Histamine Synthesised by mast cells in tissues and, basophils, released in response to inflammation, increases, capillary permeability and dilation., (b) Leukotrienes Released from mast cells, assist in promoting, allergic response cause vasoconstriction, attract neutrophils, to the site of inflammation present in large quantity in, rheumatoid joints., (c) Cytokines Polypeptide hormones, help in defence, mechanism, elicit effects on same cells and nearby cells,, important cytokines are interleukins and interferons., (d) Thromboxanes Synthesised by platelets, cause, vasoconstriction and platelet aggregation, thus contribute to, the process of blood coagulation., , www.aiimsneetshortnotes.com
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362, , Telegram @neetquestionpaper, , Handbook of Biology, , Human Endocrine System, Neurosecretory neurons, of hypothalamus, , Anterior, pituitary, Venous, outflow, , Capillary bed, Hypophyseal, Vein, Portal, Capillaries in, System, anterior pituitary, An anatomical connection, Posterior, between nervous, endocrine, pituitary, and circulatory system., , 123, , Arterial, inflow, , Pituitary Gland, Master gland of the body, lying in hypophysial, fossa or sella turcica, contains two parts,, i.e., adenohypophysis (anterior) and, neurohypophysis (posterior). Adenohypophysis, is formed from embryonic buccal, cavity (Rathke’s pouch) and neurohypophysis, develops from diencephalon., , Parathyroid, These are the four small nodules of, tissue embedded in the back side of, thyroid gland; develop as epithelial buds, from third and fourth pairs of pharyngeal, pouches, contain chief (principal) cells, which secrete hormones and oxyphil, (eosinophil) cells which are considered, as degenerated chief cells. Its hormones, are called parathormones, or collips hormone., , Adrenal Gland, Perched on top of the kidneys;, consists of an inner medulla and, outer cortex, each of which releases, several hormones. Its cortex region is, mesodermal in origin, whereas, medulla is ectodermal., Medulla secretes emergency, (or flight or fight) hormones., , Pancreas, Dual purpose organ, produces, digestive enzymes and hormones,, its acini meets the exocrine, functions, whereas Islet of, Langerhans perform, endocrine functions., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 363, , Chemical Coordination and Integration, Pineal Body, Also called epiphysis,located on the dorsal, side of forebrain; it is stalked, small, rounded, and redish–brown gland, secretes hormones, like melatonin (derivative of tryptophan) and, neurotransmitters like serotonin, histamine,, somatostatin, etc., , Hypothalamus, Contains neurosecretory cells (nuclei), that produce hormones to control the, pituitary functioning. It synthesises both, tropic and inhibitory hormones., , Thyroid Gland, Contains follicles which synthesise hormones., The follicles are formed of cuboidal epithelial, cells, secrete 3 hormones namely triiodothyronin, (T3), thyroxine (T4) and calcitonin., , Thymus Gland, Endodermal origin, develops from, the epithelium of outer part of third, gill pouch, lobular structure lying on, dorsal side of the heart and aorta,, contains lymphoid tissues that take, part in proliferation and maturation of, T-lymphocytes and release peptide, hormones that are referred to as thymosins, (humoral factors) and are important during, puberty., , Ovaries, , Testes, Male gonad, perform dual functions,, i.e., synthesise sperms and release, hormone, their hormones are called, androgens., , Female gonad, perform dual, functions, i.e., production of, ova and hormone release., , www.aiimsneetshortnotes.com
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364, , Telegram @neetquestionpaper, , Handbook of Biology, , Major Hormones of Human Endocrine System, Gland, Hypothalamus, , Hormone, , Type, , Action, , Oxytocin, , Peptide, , Moves to posterior pituitary for, storage., , Antidiuretic Hormone, , Peptide, , (Vasopressin), , Moves to posterior pituitary for, storage., , Regulatory Hormones, (RH and IH) of, anterior pituitary gland, , Act on anterior pituitary to, stimulate or inhibit the, hormone production., , Pituitary gland, Anterior, (i) Pars distalis, , Growth Hormone (GH) Protein, , Stimulates body growth., , Prolactin, , Protein, , Promotes lactation., , Follicle-Stimulating, Hormone (FSH), , Glycoprotein Stimulates follicle maturation, and production of oestrogen;, stimulates sperm production., , Luteinizing Hormone, (LH), , Glycoprotein Triggers ovulation and, production of oestrogen and, progesterone by ovary,, promotes sperm production., , Thyroid-Stimulating, Hormone (TSH), , Glycoprotein, , Stimulates the release of T3, and T4 ., , Adrenocorticotropic, Hormone (ACTH), , Peptide, , Promotes the release of, glucocorticoids and androgens, from adrenal cortex., , (ii) Pars, intermedia, , Melanocyte-Stimulating, Hormone (MSH), , Peptide, , Maintenance of lipid content in, body., , Posterior, , Oxytocin Vasopression, (ADH), , Peptide, , Initiates labor, initiates milk, ejection, controls osmotic, concentration of body fluids in, particular water reabsorption, by kidneys., , Thyroid gland, , T3 (Triiodothyronine), , Amine, , Increases metabolism and, blood, pressure, regulates, tissue growth, five times more, potent than T4 ., , T4 (Thyroxine), , Amine, , Increases metabolism and, blood pressure, regulates tissue, growth., , Calcitonin, , Peptide, , Childhood regulation of blood, calcium levels through uptake, by bone., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 365, , Chemical Coordination and Integration, Gland, , Hormone, , Type, , Action, , Parathyroid, gland, , Parathyroid hormone, (parathormones or collip, hormones)., , Peptide, , Increases blood calcium, levels through action on, bone, kidneys and intestine., , Pancreas, , Insulin (a-cells), , Protein, , Reduces blood sugar level, by regulating cell uptake., , Glucagon (b-cells), , Protein, , Increases blood sugar levels., , Adrenal glands, , Epinephrine, , Amine, , Adrenal medulla, , (Adrenaline), , Affects PNS either by, stimulating or inhibiting it,, increases respiration rate,, heart rate and muscle, contraction., , Amine, , Stress hormone, increases, blood pressure, heart rate, and glucose level., , Glucocorticoids (cortisol), , Steroid, , Long-term stress, response–increased blood, glucose levels, blood volume, maintenance, immune, suppression., , Mineralocorticoids, (Aldosterone), , Steroid, , Long-term stress, response-blood volume and, pressure maintenance,, sodium and water retention, by kidneys., , Norepinephrine, (Nor-adrenaline), Adrenal cortex, , Gonads, Testes, , Androgens (Testosterone) Steroid, , Reproductive maturation,, sperm production., , Ovaries, , Oestrogen, , Steroid, , Stimulates hypothalamus to, release GnRH before, ovulation, maintains, follicular growth., , Progesterone, , Steroid, , Maintains pregnancy and, uterus wall thickening,, inhibits the release of, oestrogen., , Pineal gland, , Melatonin, , Amine, , Circadian timing (rhythm)., , Thymus, , Thymosin, , Peptide, , Development of, T-lymphocytes., , www.aiimsneetshortnotes.com
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366, , Telegram @neetquestionpaper, , Handbook of Biology, , Mechanism of Hormone Action, Hormones are mainly of two types, i.e., water soluble (e.g., amino, acid derivatives, peptide and protein hormones) and lipid soluble, (e.g., steroid hormones)., Water soluble hormones require extracellular receptors and generate, second messengers (e.g., cAMP) for carrying out their activity., Lipid soluble hormones can pass through cell membranes and directly, enter the cell., (i) Steroid Hormone Action through Intracellular Receptors, These hormones easily pass through the cell membrane of a target cell, and bind to specific intracellular receptors (protein) to form a hormone, receptor complex., , Uterine cell, membrane, Hormone, (e.g., oestrogen), , 2 Hormone-receptor, complex binds to, transcription factor, Nucleus which further binds, to DNA., , Genome, 1 Steroid hormone, binds to receptor, to form receptor, hormone complex, in the nucleus., , Proteins, , 4 Physiological responses, like tissue growth and, differentiation are elicited., , 3 A particular gene, is activated and, Receptor-Hormone Complex, transcribed., , Mechanism of steroid hormone action, , (ii) Peptide Hormone Action through Extracellular Receptors, These hormones act at the surface of target cell as primary, messengers and bind to the cell surface receptor forming the, hormone-receptor complex., This mechanism was discovered by EW Sutherland in 1950 for which, he got the Nobel Prize., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 367, , Chemical Coordination and Integration, Adrenaline Hormone, 1 Binding of hormone to receptor, form hormone receptor complex., Membrane, , Adrenaline Receptor, , a, G-Protein, , GDP, , 2 Hormone receptor, complex induces the GDP, release of GDP to from, G-protein which releases, l and b subunits of, G-Protein., 5 cAMP molecules bind to, inactivated protein kinase, A and activate it., , g, b, , g, b, , 3 g and b subunits, activate the, adenyl cyclase., ATP, , Protein Kinase A, (inactive), , Extracellular, , a, GTP, , Activated Adenyl, Cyclase, 4 Activated adenyl cyclase, catalyses the formation of, cAMP from ATP., , Protein Kinase A, (active), , 6 Every activated, Phosphorylase Kinase, molecule, (inactive), Phosphorylase Kinase activates, (active), inactivated, Glycogen, molecules, Phosphorylase, (Cascade effect)., (inactive), Glycogen Phosphorylase, (active), , 7 Activated glycogen phosphorylase Glycogen, convert glycogen to glucose-1 phosphate, which changes to glucose, , Glucose, , Membrane, , Cytoplasm, , Glycose-1, Phosphate, , Outside, , Mechanism of protein hormone action, , Hence, single molecule of adrenaline may lead to the release of, 100 million glucose molecules., , Regulation of Hormone Action, Both hypoactivity and hyperactivity of an endocrine gland produces, structural or functional abnormalities. Hence, the normal functioning, of endocrine glands and the level of hormones in the body needs to be, regulated., , www.aiimsneetshortnotes.com
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368, , Telegram @neetquestionpaper, , Handbook of Biology, , This is possible by feedback mechanisms. Feedback mechanism, works on a simple principle that a hormone will be synthesised only, when it is needed. Thus, feedback mechanism may be positive or, negative and may operate in following ways, , 1. Feedback Control by Hormones, The hyposecretion of a hormone is sometimes dependent upon the, hormones secreted by other glands. For example, hypothalamus is, stimulated by some external stimulus and produces releasing, hormones., , 2. Feedback Control by Metabolites, The levels of metabolites also affect the secretion of certain hormones., For example, after a meal, glucose level of blood rises which stimulates, secretion of insulin to act on it., , 3. Feedback Control by Nervous System, An emotional stress stimulates the sympathetic nervous system. In, turn, sympathetic nerves of adrenal gland stimulate adrenal medulla, to produce adrenaline hormone. This leads to increase in blood, pressure, heartbeat and rate of respiration., , Control of Hormone Action, Hormones help to control many homeostatic mechanisms. Their, production and release are generally controlled by positive or negative, feedback loop., l, In positive feedback loop, hormones released by one gland, stimulate the other gland which further leads to even more, significant changes in the same direction. It acts as self-amplifying, cycle that accelerates a process., l, While in negative feedback loop, the end product of a biochemical, process inhibits its own production., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 369, , Chemical Coordination and Integration, Endocrine Disorders, , (i) Acromegaly It is caused by the hypersecretion of GH after, bone growth has stopped., Its symptoms include skin and tongue thickening, enlarged, hands and feet, facial features become coarse., (ii) Addison’s disease It is caused due to the decreased, production of hormones from adrenal gland usually due to, autoimmune reactions., Its symptoms include loss of weight and appetite, fatigue,, weakness, complete renal failure., (iii) Cushing’s syndrome It is caused due to the hyposecretion of, hormones from adrenal glands., In this disease, face and body become fatter, loss of muscle mass,, weakness, fatigue, osteoporosis., (iv) Cretinism (Hypothyroidism) The retarded mental and, physical development is associated with the hyposecretion of, thyroid hormones. The child receives hormones from the mother, before birth, so appears normal at first, but within a few weeks, or months it becomes evident, the physical and mental, development are retarded., Symptoms are disproportionately short limbs, a large, protruding tongue, coarse dry skin, poor abdominal muscle tone, and an umbilical hernia., (v) Diabetes insipidus It is caused due to the hyposecretion of, ADH and characterised by excessive thirst, urination and, constipation., (vi) Diabetes mellitus It is caused due to the insufficient insulin, production in body. It can be of two types, i.e., Type 1 or Insulin, Dependent Diabetes Mellitus (IDDM) and Type 2 or, Non-Insulin Dependent Diabetes Mellitus (NIDDM)., It is characterised by poor wound healing, urinary tract, infection, excess glucose in urine, fatigue and apathy., (vii) Eunuchoidism It is a hormonal disorder due to the deficient, secretion of testosterone in males. In this case, the secondary, male sex organs, such as prostate gland, seminal vesicle and, penis are underdeveloped and non-functional. The external, male sex characters like beard, moustaches and masculine voice, fail to develop, sperms are not formed., , www.aiimsneetshortnotes.com
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370, , Telegram @neetquestionpaper, , Handbook of Biology, , (viii) Grave’s disease (Hyperthyroidism) It is caused due to the, hypersecretion of thyroxine., Its symptoms include protrusion of eyeballs (exopthalamus),, excessive fat near the eyes, weight loss, nervousness, excess, sweating., Toxic nodular goitre (Plummer’s Disease) It is caused due, to the excess secretion of T3 and T4 and is characterised by the, presence of glandular tissue in the form of lumps., Simple goitre It is caused due to the deficient secretion of T3, and T4 hormones which results in the enlargement of thyroid, gland., (ix) Gigantism It is caused by the excess of growth hormone from, early age. It is characterised by large and well-proportioned, body., (x) Gynaecomastia It is the development of breast tissue in, males. Gynaecomastia occurs mainly due to the disturbance in, oestrogen and testosterone ratio., (xi) Hyperparathyroidism It is caused due to the excessive, parathromones secretion usually due to tumour in parathyroid, gland., Its symptoms include kidney stones, indigestion, depression,, loss of calcium from bones, muscle weakness., (xii) Hypoparathyroidism (Tetany) It is caused due to the, hyposecretion of parathyroid hormones., Its symptoms include muscle spasm, dry skin, numbness in, hands and feet., (xiii) Hypogonadism It occurs due to the defect in hypothalamus,, pituitary, testes or ovaries. In males, less production of, testosterone occurs affecting the development of male secondary, sexual features. In females, deficient production of oestrogen, occurs resulting in very less development of secondary sex, characters., (xiv) Simmond’s disease It is caused due to the atrophy or, degeneration of anterior lobe of pituitary gland. In this disease,, the skin of face becomes dry and wrinkled and shows premature, ageing., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Reproduction in Organisms, 371, , 23, Reproduction in, Organisms, Reproduction is the process of producing offspring similar to itself. It is, a characteristic feature of living organisms., Biologically it means the multiplication and perpetuation of the, species., According to the conditions available in environment, organisms have, adapted the processes of reproduction. Generally, two types of, reproduction mechanisms are present in organisms., Reproduction, , Asexual Reproduction, • Uniparental (single parent involved)., • Gamete formation does not occur., • Syngamy (gametic fusion) is absent., , Sexual Reproduction, • Biparental (both parents involved)., • Gamete formation always occurs., • Syngamy characteristically occurs., , Reproduction in Plants, Plants also reproduce by both asexual and sexual methods., , Asexual Reproduction in Plants, The asexual reproduction in plants is also known as vegetative, propagation., , www.aiimsneetshortnotes.com
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372, , Telegram @neetquestionpaper, , Handbook of Biology, , In both lower and higher plants, it occurs by following methods, (i) Vegetative propagules There are various vegetative, propagules involved in asexual reproduction.These are, discussed in chapter 19. These may be tuber, runner, sucker,, corm, stolons, offset, bulbil and rhizome, etc., (ii) Fragmentation This method is common in algae, fungi and, lichens. The small fragments of plant body led to the formation, of new individuals., (iii) Fission This process of reproduction is found in yeast, algae, and bacteria. The organism divides into two or more halves., (iv) Budding Mostly occurs in yeasts. Small protruding vegetative, outgrowths, develop into new organism after detaching from, the mother plant., (v) Spores Algae, fungi, bryophytes and pteridophytes reproduce, by this method. Spores are usuallymicroscopic structures., (vi) Conidia Series of rounded structures in several fungi and, algae called conidia. After detaching, these germinate into new, plants., , Sexual Reproduction in Plants, The plants also reproduce sexually in which fertilisation of male and, female gametes takes place and zygote is formed. Gametic cells (i.e.,, sperm and egg) are produced by the meiotic division., In lower plants, these gametes fuse directly through their cells and, show isogamy (fusion between similar gametes), anisogamy (fusion, between dissimilar gametes) and oogamy (fusion between, well-defined gametes)., In bryophytes and pteridophytes, these gametes are formed in welldefined structures like antheridia (for male gametes) and archegonia, (for female gametes), while in phanerogams, these are situated inside, more pronounced structures like androecium (for male gametes) and, gynoecium (for female gametes)., , Reproduction in Animals, Animals reproduce by both asexual and sexual methods., , Asexual Reproduction in Animals, It is the primary means of reproduction among the protists,, cnidarians and tunicates., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Reproduction in Organisms, 373, The process of asexual reproduction can occur through following methods, (i) Regeneration It is the formation of whole body of an organism, from the small fragment of parent body, e.g., Planaria, Hydra, etc., (ii) Fission The parent body is divided into two or more, daughter cells, which become new individual, e.g., planarians,, protozoans, etc., (iii) Budding Small projections or outgrowths in protozoans and, sponges. Projection is called bud, later bud develops into new, organisms, e.g., yeast and coelenterates., (vi) Fragmentation The parent body breaks into two or more, fragments. Each fragment becomes, new organism, e.g.,, sponges and echinoderms., (v) Strobilisation In this, the ring-like constrictions are developed, and organisms look like a pile of minute saucers, e.g., Aurelia., (vi) Spore formation The propagules which germinate to form, new individual, e.g., Funaria, Claviceps, Toxoplasma gondii, etc., (vii) Gemmules These are the asexual? reproductive structures, present in several sponges. These are internal buds, e.g., Spongilla lacustris., , Sexual Reproduction in Animals, In animals, the sexual reproduction occurs by the fertilisation of, haploid sperm and haploid egg, to generate a diploid offspring., In most individuals (i.e., dioecious), females produce eggs (i.e, large, non-motile cells containing food reserve) and males produce sperms, (i.e., small, motile cells and have almost no food reserve)., In other individuals (i.e., monoecious) such as earthworm and, many snails, single individual produces both sperms and egg. These, individuals are called as hermaphrodite. The union of sperm and egg, occurs in variety of ways depending on the mobility and the breeding, environment of individual, sexual reproduction is of two types, Sexual Reproduction, Syngamy, Permanent fusion of male, and female gametes., , Conjugation, Temporary fusion of male and, female parents of the same species, for exchange of nuclear material,, e.g., bacteria and Paramecium., , On the basis of no. of parents involved., Exogamy, It is the fusion of gametes, produced by two different, parents, e.g.,dioecious, individuals., , On the basis of structure of fusing gametes., Isogamy, Fusion of morphologically, Endogamy, similar gametes, e.g.,Monocystis., It is the fusion of gametes, produced by the same parent,, e.g.,monoecious individuals., , Anisogamy, Fusion of two dissimilar gametes,, e.g., frog, rabbit, etc., , www.aiimsneetshortnotes.com
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374, , Telegram @neetquestionpaper, , Handbook of Biology, , Other Modes of Sexual Reproduction, (i) Autogamy Fusion of male and female gametes produced by, same individual, e.g., Paramecium., (ii) Hologamy Fusion of entire mating individuals acting as, gametes, e.g., Chlamydomonas., (iii) Paedogamy Fusion of young individuals, e.g., Actinosphaerium., (iv) Merogamy Fusion of small and morphologically dissimilar, gametes., (v) Macrogamy Fusion of two macrogametes takes place., (vi) Microgamy Fusion of two microgametes takes place., (vii) Cytogamy Fusion of cytoplasm of two individuals, but no, nuclear fusion, e.g., P. aurelia., (viii) Plasmogamy Fusion of related cytoplasm, e.g., fungi., (ix) Karyogamy Fusion of nuclei of two gametes, e.g., Mucor., (x) Automixis Fusion of gamete nuclei of the same cell, e.g.,, phasmids., , Events of Sexual Reproduction in, Both Plants and Animals, The events of sexual reproduction are though lengthy and complex, but, follow a regular sequence. For easy understanding of the process, the, process of sexual reproduction (i.e., fertilisation) can be divided into, three distinct stages., These are as follows, (i) Pre-fertilisation events, (ii) Fertilisation, (iii) Post-fertilisation events., , 1. Pre-Fertilisation Events, The events which occur before the fertilisation (i.e., gametic fusion), are included in this. These include gametogenesis and gamete transfer., , Gametogenesis, The process of gamete formation is known as gametogenesis. The gametes, are generally of two kinds, male gametes and female gametes., In some lower organisms, both male and female gametes are, morphologically similar and are called isogametes or homogametes., In higher organisms, both male and female gametes are, morphologically distinct and are called heterogametes., Heterogametes, , Small—Microgamete/Male gamete—Spermatozoa, Large— Macrogamete/Female gamete—Ova, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Reproduction in Organisms, 375, The gametes are usually formed by meiotic division, therefore they are, haploid in nature., , Gamete Transfer, In most of the organisms, male gamete is motile and the female, gamete is non-motile. The male gametes are produced in large, number because large number of male gametes are failed to reach, female gamete. In flowering plants through the process of pollination,, male gametes reach to female gamete., , 2. Fertilisation Events, In this stage, the most important event is the fusion of gametes, (haploid) and formation of diploid zygote. This process is called, syngamy or fertilisation., The process of fertilisation may occur outside the body of organisms,, called external fertilisation (e.g., algae, amphibians, fishes, etc)., If the syngamy occurs inside the body of organisms, it is called internal, fertilisation (e.g., fungi, reptiles, birds, higher animals and plants)., In organisms like rotifers, honeybees, lizard and some birds, the female, gametes form new organisms without fertilisation. This phenomenon, is called parthenogenesis., , 3. Post-Fertilisation Events, These are the events which take place after fertilisation and are, majorly described under zygote and embryogenesis., Zygote The zygote is formed in all sexually reproducing organisms., Further, the development of zygote depends upon the type of life, cycle and the environment of organism., Embryogenesis The process of development of an organism before, birth is termed as embryogenesis. It involves gastrulation, formation, of primary germinal layers to give rise to the entire body of, organisms., Oviparous Organisms which lay eggs, to hatch out their young one, are called oviparous animals, e.g., reptiles, birds, amphibians, etc., Viviparous Organisms which give birth to newborn young ones are, termed as viviparous animals, e.g., primates, non-primates, etc., l, , l, , l, , l, , www.aiimsneetshortnotes.com
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376, , Telegram @neetquestionpaper, , Handbook of Biology, , 24, Sexual, Reproduction in, Flowering Plants, All flowering plants show sexual reproduction and to comply this, they, have adopted various features in the form of coloured flowers, minute, pollen grains and nector, etc. Before discussing sexual reproduction in, flowering plants, we must take a close look of the most pivotal, structure for sexual reproduction, i.e., a flower., , Flowers, Flowers are formed in mature plants in response to hormone induced, structural and physiological changes on shoot apices., Following flow chart will provide the detailed information about flower, Complete Flower, , Non-essential Whorls, Outermost, whorl called, Calyx, Sepals, To protect inner, whorls in bud, condition., , Essential Whorls, , Inner to, calyx is, Corolla, Petals, , Anther, , Androecium, , Gynoecium, , Stamens, , Carpels, , Connective Filament, Ovary Style Stigma, , To help in pollination, and protection of, inner whorls., Helps in reproduction, as, male reproductive organ., , Helps in reproduction, as, female reproductive organ., , Floral whorls and their functions, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 377, , Sexual Reproduction in Flowering Plants, , The whole process of sexual reproduction in flowering plants can be, divided into following steps, , Pre-Fertilisation : Structures and Events, These are discussed below, , Male Gametophyte, Stamen is male reproductive part of a flower. Each stamen is composed, of anther and filament., , Structure of an Anther, Pollen grains are formed in pollen sacs of anther. The anther is bilobed, and the lobe encloses four pollen sacs or microsporangia. The four, pollen sacs in a dithecous anther appear to lie in its four corners, thus, a typical anther is tetrasporangiate., Anther develops from a homogenous mass of hypodermal cells. These, cells contain a prominent nucleus and abundant protoplasm., These cells are called archesporial cells. Archesporial cells divide by, periclinal division and produce parietal cells on outer side and, sporogenous cells on inner side., Pollen Grain, It works as male, gametophyte, in plants., Anther, Pollen Sacs, These are the, spaces where, pollens are, formed,nourished, and get matured, , Line of Dehiscence, After maturity,, anther bifurcates, from this line and, releases pollen grains, , Filament (stalk), , (a), , (b), , (a) A typical stamen; (b) three-dimensional cut section of an anther, , www.aiimsneetshortnotes.com
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378, , Telegram @neetquestionpaper, , Handbook of Biology, , Structure of Microsporangium, It is surrounded by following four layers, Microsporangium, Layers, Epidermis, , Endothecium, , Middle layer, , Tapetum, , (Single layer,, provides, protection)., , (Single layer,, cells have fibrous, thickenings)., , (One to three, layers)., , (Single layer, multinucleate cells with, dense cytoplasm provides nourishment, to developing pollen grains)., , Development of Pollen Grain (Male Gametophyte), Epidermis, Endothecium, Middle layers, Microspore, mother cells, , Hypodermal Cell of Anther, Differentiation/, Specialisation, Archesporial Cell, (prominant nucleus and, abundent protoplasm), , (Provide, protection), , Tapetum, , Periclinal division/, Layering division, , Microsporangium, (nourishes the developing pollen grain), , Microspore mother cell, Parietal Cells, (outer), Anticlinal, division, 2-5 layers of anther, wall and tapetum, , Sporogenous Cells, (inner), Specialisation, Microspore Mother Cells (MMCs), or Pollen Mother Cells (PMCs), Meiosis, , Microspore, tetrad, , Microspore or Pollen Grain, (In form of tetrad), , Generative cell, (small), , Dehydration, Separated Pollen Grain, Mitotic division in, generative cell, Pollen Grain, , Vegetative cell, (bigger with abundant, food material), Nucleus of, tube cells, Sperm cells, , Maturation, Sperm cells, Mature Pollen Grain, Tube cell, nucleus, , Microsporogenesis, , Stages of maturation of, microspore into pollen grain, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 379, , Sexual Reproduction in Flowering Plants, , Note About 60% angiosperms shed their pollen in 2-celled stage and remaining, shed the pollen in 3-celled stage., , Microspores or Pollen Grains Arrangement, The newly formed microspores are arranged mostly in tetrahedral, manner with following arrangements, , (a) Tetrahedral, , (b) Isobilateral, , (c) Decussate, , (d) T-shaped, , (e) Linear, , Different types of microspore tetrads, , Tectum, , Bacculum, , 123, , Foot layer, , 1442443, , Pollen Wall, , Intine, , It is chiefly made up, of sporopollenin, which is the most resistant, Exine known biological material., It is discontinuous at some, places, these are called, germ pores., The pollen tube germinates, through germ pores., , It is made up of cellulose and, pectin material., , Pollenkitt is the matter produced by tapetal cells, which provide, specific colour and odour to pollen grains and help in attracting, pollinating insects., , Female Gametophyte, Female reproductive part of a flower is as follows, , Pistil/Gynoecium, It is the innermost essential whorl of a bisexual flower. Its main parts, are, l, l, l, Stigma, Style, Ovary, Structure of Megasporangium (Ovule), An individual ovule comprises of a nucellus invested by one or two, integuments. They help in encircling the ovule, except the tip at, micropylar end and a stalk called funiculus or funicle., , www.aiimsneetshortnotes.com
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382, , Telegram @neetquestionpaper, , Handbook of Biology, , Degenerating, megaspores, 2 nuclei formed, 1, , Further nuclear, division, , 4 nuclei formed in, total (2 at each ends), 2, , Further nuclear, division, , 8 nuclei formed, (4 at each end), 3, (1 nucleus from each, end moves to centre), , Micropylar end, Synergids, 3 nuclei remains, at each end, , 4, , Egg, Central, cell, 2-polar, nuclei, , Antipodals, , Wall formation, and vacuole, development, , Chalazal end, Antipodals, 5, 3 cells at micropylar end form egg, apparatus and remaining 3 cells at, chalazal end form antipodals., The central nuclei form central cell., , Polar nuclei, Central cell, Egg, Egg apparatus, (2 synergids +, 1 egg cell), , Micropylar end, , Embryo sac formation, , www.aiimsneetshortnotes.com, , Synergids, Filiform, apparatus
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Telegram @neetquestionpaper, 383, , Sexual Reproduction in Flowering Plants, , Pollination, It is the transfer of pollen grains from the anther of a flower to the, stigma of the same or another flower., It is of two types, 1. Self-pollination, , 2. Cross-pollination, , 1. Self-Pollination (Autogamy), It is the transfer of the pollen grain from the anther of a flower to the, stigma of either the same or genetically similar flower., Adaptations for Self-Pollination, Autogamy, , Geitonogamy, , Cleistogamy, , Transfer of pollen to, the stigma occurs in, the same flower,, e.g., rice., , Pollens of one flower are, deposited on the stigma of, another flower of the same, plant., , Flowers never open., The pollen from anther, lobe falls on the stigma, of the same flower,, e.g., Commelina, bengalensis., , Direct contact of, anther and stigma, occurs by bending of, filaments and style, of the two organs, respectively, e.g.,, Mirabilis jalapa., , This transfer involes a, pollinator, hence functionally,, it is a cross-pollination., Genetically, it is similar to, autogamy since the pollen, grains come from the same, plant., , Anthers do not, dehisce; germinated, pollen tube pierces, anther wall and enter, the stigma of same, flower., , 2. Cross-Pollination (Xenogamy), It is the deposition of pollen grain from anther of a flower to the stigma, of a genetically different flower of another plant of same or different, species. It is also known as allogamy., , www.aiimsneetshortnotes.com
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384, , Telegram @neetquestionpaper, , Handbook of Biology, , Certain adaptations to facilitate xenogamy are as follows, Adaptations for Cross-Pollination (Outbreeding Devices), Dichogamy, , Dicliny, , Herkogamy, , The condition,, where maturation, time of stigma and, anthers is such, that either stigma, becomes receptive, before anthers get, mature (protogyny), or the anthers, become ready for, the dehiscence, before stigma, becomes receptive, (protandry), e.g.,, in Aristolochia and, Scrophularia,, protogyny occurs, and in rose,, sunflower,, Impatiens, etc.,, protandry condition, is found., , The presence of only, one kind of, reproductive whorl in, a flower is called, dicliny or unisexuality., A plant may be, monoecious, i.e.,, carrying male and, female flowers on the, same plant. In such, case, both cross and, self-pollinations can, occur., In dioecious plants,, i.e., plants either with, male or female flowers, are borne on different, plants, in such a case, cross-pollination is the, only way of, pollination., , In some flowers, a, mechanical barrier, exists between the, compatible pollen, and stigma so that, self-pollination, becomes, impossible., Sometimes, a, hood-like, covering, covers the stigma, as in Iris and in, Calotropis. The, pollens are, grouped in pollinia, and stick to the, surface till they, are carried away, by the insects., , Self-Sterility or, SelfIncompatibility, The pollen of a, flower has no, fertilising effect, on the stigma of, the same flower,, e.g., Thea, sinensis (tea),, Passiflora, etc., , Agents of Pollination, The pollination can occur through following agents, Various Agencies of Pollination, Pollinating, Agency, , Process, , Agent, , Examples, , Anemophily, , Wind, , Grasses, maize and gymnosperms, , Hydrophily, Entomophily, , Water, Insects, , Vallisneria and Hydrilla, Rose, poppy and Salvia, , Ornithophily, , Birds, , Erythrena and Marcgravia, , Abiotic agents, , Biotic agents, , Cheiropterophily, , Bats, , Baobab tree (Adansonia), , Malacophily, , Snails, , Chrysanthemum and Lemma, , Myrmecophily, , Ants, , Myrmecophilus acervorum, , Anthrophily, , Human, , Various ornamental plants, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 385, , Sexual Reproduction in Flowering Plants, , Flowering plants have adapted various features to support their, pollinators in the process of pollination as insect pollinating plants, have strong nectariferous glands to attract the insects. On the other, hand, wind pollinating plants have very light and non-sticky pollen, grains to fly freely in air., Note, , l, , l, , Pollen-pistil interaction refers to the events from the deposition of pollen on, the stigma till the entry of pollen tube into the ovule. It determines compatibility, and incompatibility of pollen and pistil., Artificial hybridisation has been used by the plant breeders for crop, improvement programme. It includes emasculation (removal of anther from, bud before anther dehisces, if female parent bears bisexual flowers) and, bagging., , Fertilisation, Through the process of pollination, the pollen lands on the stigma of a, female flower. Pollen grain germinates and tube cell elongates and, grows down into style towards the ovule in ovary., , Double Fertilisation, It was discovered by Nawaschin in 1898. It is a complex process of, fertilisation in flowering plants which involves a female gametophyte, and two male gametes., , Entry of Pollen Tube into Ovule, The pollen tube can enter in ovule through three alternate ways., These are, (i) Porogamy Entry through micropyle., (ii) Mesogamy Entry through integuments., (iii) Chalazogamy Entry through chalazal end., Embryo sac, , Chalazal pole, , Pollen tube, , Antipodals, Integuments, Polar nuclei, Egg, Egg, apparatus Synergids, Micropylar pole, Pollen tube, , Funiculus, , (a) Porogamy, , (b) Mesogamy, , (c) Chalazogamy, , Various routes of pollen tube entry into the ovule, , www.aiimsneetshortnotes.com
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386, , Telegram @neetquestionpaper, , Handbook of Biology, , The process of fertilisation is presented diagrammatically below, Mature pollen grain, Sperm cells, Tube cell nucleus, , Generative, cell, Tube, cell, Antipodal, cells, Ovule, , Empty pollen grain, Tube cell, Sperm cells (male gametes), Tube cell nucleus, , Pollen grain, Stigma, Style, , Carpel, Pollen tube, , Embryo sac, , Ovary, , Growth of, Embryo, sac, , pollen tube, Secondary nucleus, containing two nuclei, , Further elongation, , Pollen germination and tube, Pollination, entry into style. The two nuclei of pollen tube, The landing of pollen grain on stigma,, into style., also move into pollen tube., i.e., pollination., Primary endosperm, , Mother cell after, triple fusion, Secondary, nucleus, , 1st male gamete, , Egg cell, 2nd male gamete, Syngamy + triple fusion, Double Fertilisation, , Pollen tube, , Synergids, , Release of sperm cells or male, gametes within the embryo sac, , Double fertilisation in which one male, gamete fuses with egg cell and other fuses, with central cell to form endosperm., Rest, all cells are degenerated., , The process of fertilisation and double fertilisation, , Post-Fertilisation Events, The major post-fertilisation events include development of endosperm, and embryo, maturation of ovules into seed and ovary in fruit. They, take place soon after the double fertilisation., , Development of an Endosperm, As a result of triple fusion, a triploid structure called Primary, Endosperm Mother Cell (PEMC) is formed that finally produces a, mass of nutritive cell called endosperm through mitotic division., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 387, , Sexual Reproduction in Flowering Plants, On the basis of development, endosperms are of three types, , (i) Cellular endosperm, Every division of endosperm nucleus is followed by cytokinesis. Occurs, in about 72 families, e.g., Balsam, Datura, Petunia, etc., , (ii) Nuclear endosperm, It is the most common type of endosperm (about 161 families) Primary, endosperm nucleus divides repeatedly without wall formation, hence, large number of free nuclei are present, e.g., wheat, maize, rice, etc., , (iii) Helobial endosperm, It occurs mostly in monocots. The endosperm is of intermediate type, between cellular and nuclear endosperm, e.g., Asphodelus., , Functions of Endosperm, The important function of endosperm is to provide nutrition to the, embryo and support its growth., , Development of an Embryo/Embryogenesis, Before going into detail of embryogenesis, we first understand the, embryo., , Embryo, The embryo of a plant is a miniature plant tucked into a foetal position, in the seed. It is actually one of the earliest stage in the development of, a plant, where nutrients which are provided to the seed enable it to, germinate into a plant., Dicot embryo consists of an embryonal axis and two cotyledons., Embryo of monocots possesses only one cotyledon at one end., The embryogenesis is the series of specialisation and differentiation of, cells., , www.aiimsneetshortnotes.com
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388, , Telegram @neetquestionpaper, , Handbook of Biology, , The whole process of embryogenesis can be understood through, following flow chart, Zygote, Close to micropylar, pole, , Divides by a, Towards chalazal pole, transverse division, but far from it, , Basal cell, , Terminal cell, , 3 to 5 transverse, divisions, , One longitudinal, division, , 6 to 10-celled, suspensor, , Two terminal, cells, Two longitudinal, divisions, , Terminal (distal), Proximal cell, cell becomes enlarged, is called, and forms vasicular, hypophysis, cell of suspensor, One transverse, division followed, by two vertical, divisions at right, angle to the previous, , 4-celled, quadrant, Four transverse, divisions, 8-celled, octant, Eight periclinal, divisions, , Embryonic, root and, root cap, , 8 inner cells, , 8 outer cells, = dermatogen, , Periclinal, division, , Anticlinal, divisions, , Initial of Initial of, plumule cotyledons, , Epidermis of, embryo, , Embryonic, Two, shoot, cotyledons, , Embryo development in dicots, , Seed, ‘A seed typically consists of seed coat, cotyledons and an embryo axis.’, In angiosperms, it is the final product of sexual reproduction and they, are formed inside fruit., Although in most of the species, fruits are the result of fertilisation,, some species develop fruit without fertilisation. Such fruits are called, parthenocarpic fruits, e.g., banana., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 389, , Sexual Reproduction in Flowering Plants, , Fruits, These are mature or ripened ovaries developed after fertilisation,, containing seeds inside them., Help in dispersal, of seeds, , Sometimes provide, nutrition to developing, seedlings, , Source of energy, , Significance, of fruits, , Source of nutrients, like sugar, vitamin, etc., , Protect seed from, environmental conditions, , Post-Fertilisation Changes in Ovary Leading to, Fruit and Seed Formation, Ovary, – Fruit, Ovary wall, – Pericarp, Ovule, – Seed, Outer integument – Testa, Seed coat, Inner integument – Tegmen, Synergids, – Degenerate, Egg cell, – Oospore (embryo), , Additional Terms, 1. Parthenocarpy, It is the process of producing fruits without fertilisation., On the basis of its causes, it is of three types, (i) Genetic parthenocarpy Parthenocarpic fruits are produced, because of hybridisation or mutation., (ii) Environmental parthenocarpy The environmental, condition like fog, frost, high temperature and freezing led to, non-functioning of reproductive organ and results into, parthenocarpy., (iii) Chemical induced parthenocarpy The artificial, application of IAA, α-NAA, gibberellin leads to production of, parthenocarpic fruits., , www.aiimsneetshortnotes.com
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390, , Telegram @neetquestionpaper, , Handbook of Biology, , 2. Apomixis, The term ‘Apomixis’ was introduced by Winkler (1908)., ‘Apomixis is the substitution of sexual reproduction, which does not, involve meiosis and syngamy.’, It is of two types, (i) Vegetative reproduction It is a type of asexual reproduction,, mostly in plants when a plant part is detached and produces new, progeny., (ii) Agamospermy Process which involves sex cells but takes place, without fertilisation or meiosis., mitotic, , mitotic, , (a) Diplospory MMC → Embryo sac → Embryo, ( 2n ), , division, , ( 2n ), , division, , ( 2n ), , (b) Adventitive embryony The nucellar or integumentary cells, produce diploid embryo., (c) Apospory Cell, outside the embryo sac produces aposporic, embryo sac., , 3. Polyembryony, The process of occurrence of more than one embryo in a seed is, known as polyembryony. It was first observed by Antonie van, Leeuwenhoek in 1917 in orange seed., On the basis of originating cell, it is of two types, (i) Gametophytic polyembryony (arises from haploid cells of, embryo sac), (ii) Sporophytic polyembryony (embryo arises from diploid, structures), , 4. Xenia, The term ‘Xenia’ was coined by Wilhelm Olbers Focke in 1881., It is the effect of pollen on maternal tissues including seed coat and, pericarp. When one allele in the pollen is able to mask the effect of, double dose of other, the former is called xenia over the latter., , 5. Metaxenia, It is a condition during hybridisation where the alleles of one locus, behave as a double dose for the other and make it as a recessive., This condition is found in aneuploids where segregation is prevented., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 25, Human, Reproduction, Human beings show sexual reproduction and they have separate sexes, (unisexual). As we can identify male and female from their physical, appearance means sexual dimorphism is also present. The secondary, sexual characters of man and woman are as follows, Secondary Sexual Features in Man and Woman, Character, , Man, , Woman, , General build up, , More muscular, , Less muscular, , Aggressiveness, , More marked, , Less marked, Absent, , Hair growth, (i) Facial, , Beard, moustache present, , (ii) Axillary, , Present, , Present, , (iii) Pubic, , Hair distribution more lateral, and upwards towards umbilicus, , Upward growth not so marked, and is more horizontal, , (iv) Chest, , Present, , Absent, , Mammary glands, , Undeveloped, , Well-developed, , Pelvis, , Not broad, , More broad, , Larynx, , More apparent, , Less apparent, , Voice, , Low pitched, , High pitched, , Breathing, , Predominantly abdominal, , Predominantly thoracic, , BMR, , High due to greater activity, , Not so high as compared to man, , Male Reproductive System, The male has two visible sex organs, the testes and penis, which can, be seen from the outside. The testes are the primary male sexual, organ in males, whereas prostate, seminal vesicles, vas deferentia, and penis are the secondary sexual organs., , www.aiimsneetshortnotes.com
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www.aiimsneetshortnotes.com, , Corpora, cavernosa, , Artery, , TS of Penis, , Urethra Corpus, spongiosum, , Dorsal veins, , LS of Penis, , Prepuce, Foreskin which covers, the glans penis, , Spongy Erectile, Tissue, 3 cylindrical, masses–2 dorsal, corpora covernosa, and 1 ventral corpus, spongiosum, , Urethra, Provides common, pathway for, sperms and urine,, its opening, possesses 2, sphincters, its, external opening is, called urethral, meatus., , Testes, Primary sex organ,, produce sperms and male, sex steroids, suspended, in the scrotum by the, spermatic cords called, gubernaculum, lined by, mesorchium, which, protects the testis., , Epididymis, Long, narrow, coiled tubule lying along the inner side of, the testis, it stores sperms, secretes fluid, which, nourishes the sperms., , Bulbourethral Gland, Also called Cowper’s gland, secretes alkaline fluid,, called seminal plasma which is rich in fructose, calcium, and certain enzymes; it also secretes mucus that helps, in the lubrication of penis., , Seminal Vesicle, One pair of sac-like structure near the base of the bladder,, produces alkaline secretion which forms 60% of semen, volume, its fluid pH is 7.4, contains fructose, prostaglandins, and clotting factors. The fructose provides energy to semen., , Ureter, Convey the urine from kidneys to urinary bladder., , Male reproductive system, , Glans penis, Corpus spongiosum, enlargement at the, end of penis, , Penis, Male copulatory, organ,, conduct both urine, and semen., , Urinary Bladder, Muscular structure that stores the urine., Vas Deferens, Emerges from cauda epididymis,leaves scortal sac and, enters abdominal cavity, they are thick, 2 in numbers, possess many stereocilia, carry sperms from, epididymis to ejaculatory ducts., Prostate Gland, Single large gland that surrounds the urethra, produces, milky secretion with pH 6.5 which forms 25% of semen, volume, its secretion contains citric acid, prostaglandins,, and enzymes like amylase, pepsinogen, etc. Due to the, presence of citric acid, semen is slightly acidic., Prostaglandins cause the uterus muscles to contract., Ejaculatory Duct, 2 short tubes, each formed by the union of duct from seminal, vesicle and vas deferens, it passes through prostate gland, and joins the urethra; composed of fibrous, muscular,, columnar epithelium, function to convey sperms., Scrotum, Pouch of deeply pigmented skin, contains testis, its, temperature is 2-2.5°C lower than the normal body, temperature which favours the production of sperms,, remains connected to abdomen by inguinal canal., , 392, Handbook of Biology, , Telegram @neetquestionpaper
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Telegram @neetquestionpaper, 393, Human Reproduction, The testis in transverse section shows different cell types at various, stages., Nerve, Blood vessels, Vas deferens, , Epididymis, Connective, tissue, Seminiferous, tubules, Testis, Sertoli or Subtentacular Cells, Found between germinal epithelium, cells singly and elongated, they provide, nourishment to developing spermatozoa, or sperms, secrete Androgen, Binding Proteins (ABPs) that concentrate, testosterone in seminiferous tubules., , Leydig or Interstitial Cells, Endocrine portion of testis,, present in between the, seminiferous tubules in, the connective tissue, secrete, androgens (e.g., testosterone), , Secondary, Spermatocytes, Spermatids, Spermatozoa, , Seminiferous Tubules, Highly coiled tubules, present in each testicular, lobule, contain a basement, membrane, Sertoli cells, and male germ cells at, different stages., , 123, , Germinal Epithelium, Single layer, contains Sertoli, cells (at some places), and cuboidal epithelium, cells called male germ cells., Spermatogonium Different, Primary, cellular, Spermatocytes, types in testis, undergoing, different, processes., , TS of testis, , Female Reproductive System, It consists of ovaries which are the primary sex organs in human, female. The secondary sex organs in human female are Fallopian tubes, (oviducts), uterus, vagina and mammary glands., , www.aiimsneetshortnotes.com
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www.aiimsneetshortnotes.com, Fornix, Superior portion of the vagina., , Perimetrium, Outer thick layer of uterus., , Myometrium, Middle thick layer of smooth muscle fibres of uterus. It, shows strong contractions during the delivery of baby., , Endometrium, Inner glandular layer of the uterus, it undergoes cyclic, changes during menstrual cycle. Implantation of, blastocyst takes place here only., , Fimbriae, Finger-like projections of oviducts, towards the ovary. They help in the, collection of ova after ovulation from, ovary to oviduct., , Ovary, Paired, almond-shaped organs located in, female’s pelvic cavity; it produces ova and, reproductive hormones primary sex organs., , Uterine Fundus, Upper dome-shaped part of uterus above, the opening of oviducts., , Fallopian tubes or, Oviducts, Two hollow, muscular, tubes which convey the, ova released by ovary to, uterus by peristalsis., Fertilisation of ova, occurs here only., , Female reproductive system, , Vagina, Distensible, tubular organ which extends from cervix to, outside, it possesses numerous muscles that allow it to, expand during birth; it serves as receptable for sperms, during copulation., , Internal OS, It is an interior narrowing of the uterine cavity., Cervix, Small tubular structure in between the body uterus and, vagina., External OS, Small aperture on the rounded extremity of the vaginal, portion of the cervix., , Ampulla, Widest and longest, part, fertilisation, occurs here only., Infundibulum, Dilated opening,, possesses fimbriae., , Isthmus, Short narrow, thickwalled portion., , Ovarian Ligament, It attaches the ovary to the uterus., , Uterus, Also called metra/hystera/womb, hollow muscular structure, lies, between urinary bladder and rectum. It houses and nourishes the, developing foetus., , 394, Handbook of Biology, , Telegram @neetquestionpaper, , Various components of female's internal reproductive system are shown, in the given figure
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Ovarian, stroma, Consists of, cortex and, medulla, , Tunica Albuginea, Connective tissue, layer underlying, ovarian stroma, Corpus Luteum, Follicle containing lutein, (yellow pigment) formed, after ovulation, it secretes, progesterone and relaxin, hormones., , Cortex, Dense outer layer, Medulla, Less dense inner layer, , Corpus Albicans, Degenerated part of, corpus luterum,, white body, , Germ Cell, Oogonia or egg mother, cells which are not formed, after birth., , Follicular Antrum, Fluid filled cavity containing, liquor folliculi., , Secondary Oocyte, , Cumulus Oophoricus, Follicullar cells surounding, ovarian follicle, Zona Pellucida, Homologous membrane, covering the oocyte, , Membrane Granulosa, Follicular cells that surround, the zona pellucida., , Theeca Interna, , Theca Externa, , Early Antral Follicle, Surrounded by more layers, also called secondary follicle,, large in size, antrum (fluid-filled, cavity) begins to develop., , 123, , Graffian Follicle, Mature follicle which, undergoes ovulation., Contains secondary, oocute surrounded, by several layers, and a large follicular, antrum, , 321, , www.aiimsneetshortnotes.com, TS of ovary, , Ovulated Oocyte, Ovulation, Ovulation product which, It involves the release of, further preceeds for fertilisation, secondary oocyte from, journey., the ovary, occurs due to, rupturing of graffian follicle., , Primary Follicle, Germ cells divide by, mitosis to form primary, oocyte, smaller in size,, a large number degenerate, during puberty,, surrounded by single layer., , Telegram @neetquestionpaper, Human Reproduction, 395, , The primary sex organs of human females, i.e., ovaries consist of a, dense outer layer called cortex and a less dense inner portion called, medulla. A section of ovary shows the growing follicles at different, stages.
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396, , Telegram @neetquestionpaper, , Handbook of Biology, , The external genitilia or vulva of female consists of following parts., Labia Majora, Longitudinal lip-like folds, on the sides of vestibule,, contain sebaceous glands,, homologous to male, scrotum., , Mons Pubis, Also called mons veneris,, cusion of fatty tissue, covered, by pubic hairs., Clitoris, Small erectile organ, contains, numerous nerve endings, highly, sensitive, homologous to male, glans penis., , Labia Minora, Smaller and thinner than labia, majora, enclose vestibule,, homologous to male penis,, urethra., , Urethral Orifice, Small opening of urethra below, clitoris through which urine is, excreted. Also called urinary, meatus, , Vaginal Orifice, Opening of vagina through, which menstrual flows out, and into which penis is, inserted, partially covered, by hymen in virgin women., , Bartholin’s, Gland Opening, , Fourchette, Formed by the fusion, of labia minora posteriorly,, contain sebaceous glands., , Also called greater vestibular, glands lying on the sides of, vaginal orifice, homologous, to male’s cowper’s gland., Anus, Opening of rectum, to outside through, which faecal material, is expelled out., , Perineum, Area which extends, from fourchett to anus., , External genitalia of female, , Gametogenesis, It involves the formation of male and female reproductive cells, i.e.,, sperms and ova under the influence of hormones., Process of formation of sperms is called spermatogenesis and that of, ova is called oogenesis., , Spermatogenesis, The formation of sperms occurs in the seminiferous tubules of the, testis. Sperms are formed from the special cells present in the, periphery of tubules, known as spermatogonia., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Human Reproduction, 397, 2n, , Spermatogonium, (Stem cell), , Mitosis, , Contains 46 single-stranded, unreplicated chromosomes., , 2n, , Occurs in spermatogonia,, produces a constant supply, of new cells need to, 2n, produce sperms., , Growth, Primary Spermatocytes, , Some spermatogonia, actively grow by, obtaining nourishment, from the Sertoli, cells and become, primary spermatocytes., , Contain 46 double-stranded, replicated chromosomes., 2n, , Meiosis-I, Primary spermatocytes, undergo meiotic-I, division (reductional), to form 2 haploid, secondary spermatocytes., , Secondary Spermatocytes, n, , n, , n, , n, , Contain 23 double-stranded, chromosomes., , Meiosis-II, Secondary spermatocytes, undergo second, maturation division, (equivalent to mitosis), to form 4 haploid, spematids., , n, , n, , Spermatids, Contain 23 single-stranded, chromosomes., , Spermiogenesis, It is the transformation of spermatids, to spermatozoa(sperms) by, differentiation. During this process,, nucleus condenses and cytoplasm, is eliminated, whip-like tail forms, centriole. This process is also, known as spermateleosis., , Spermatozoa, Contain 23 single-stranded, unreplicated chromosomes., , Spermiation, Sperm heads become embedded in the, Sertoli cells and are finally released from, the seminiferous tubules., , Stages in spermatogenesis, , www.aiimsneetshortnotes.com
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398, , Telegram @neetquestionpaper, , Handbook of Biology, , Structure of Sperm (Spermatozoan), The sperms are microscopic and motile cells. They remain alive and, retain their ability to fertilise the ovum from 24 to 48 hours after being, entered in the female reproductive tract., Acrosome, Formed of Golgi bodies,, contains hyaluronidase,, proteolytic enzymes., , Head, Contains small anterior, acrosome and large, posterior nucleus., , Proximal Centriole, Plays a role in the first, cleavage of the zygote., , Distal Centriole, Neck, , Gives rise to the, axial filament of the sperm., , Very short, present, between head and middle, piece, contains proximal, and distal centrioles., , Mitochondrial Spiral, , Middle Piece, , Mitochondria coiled around axial, filament, provides energy for, sperm movement., , Contains mitochondrial spiral, and ring centriole (annulus)., , Ring Centriole, Presents at the end middle, piece, its function is not known., , Tail, Very long, contains axial filament surrounded, by a thin layer of cytoplasm, helps the sperm to swim., , Human sperm, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Human Reproduction, 399, Hormonal Control of Male Reproductive System, The growth, maintenance and functions of male reproductive organs, are under the control of steroid hormones–mainly testosterone. These, hormones, in turn are controlled by negative feedback mechanisms., Stimulates, Hypothalamus, GnRH, , Inhibits, Anterior Pituitary, , ICSH, FSH, , Testosterone, , Inhibin, , GnRH released from, hypothalamus stimulates anterior, pituitary to release FSH and LH, (ICSH in males). ICSH acts upon, interstitial cells to secrete, testosterone and FSH acts upon, the Sertoli cells. Both FSH and, testosterone promote, spermatogenesis in, seminiferous tubules., , Negative Feedback Control, The secretion of GnRH and, ICSH is controlled by the, testosterone in a negative, To target tissues feedback loop. Dip in the, testosterone level in the blood, Sertoli Cell, increases the production of, Seminiferous Tubule GnRH and ICSH, whereas, when the testosterone level, becomes normal, GnRH release, subsides, as does ICSH level., Similarly, FSH secretion is, controlled by inhibin by negative, feedback loop. When the excess, Spermatogenesis FSH level is detected in blood,, Sertoli cells secrete inhibin which, in turn inhibits the release of, FSH from anterior pituitary., , Interstitial Cells, , Testosterone, , Androgenblinding, protein, , Hormonal control of male reproductive system, , www.aiimsneetshortnotes.com
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400, , Telegram @neetquestionpaper, , Handbook of Biology, , Oogenesis, It is the process of formation of a mature female gamete (ovum),, occurring in the primary female gonads, i.e., ovaries., Ovarian Events, , Meiotic Events, , Before Birth, Nucleus, Oogonium, , 34444444444244444444444441, , Oocyte, , Mitosis, Primary, Oocyte, Growth, Ovary Inactive, during Childhood, , Each month from, Meiosis-I puberty to menopause, primary oocytes begin, to grow, , 344444424444444444441, , Meiosis-II, , Follicle Cells, , Cytoplasm, , Primary Oocyte, (arrested in, prophase), , Growing, Follicles, , Primary Oocyte, (still in, prophase-I), , Antral Follicles, Meiosis-I Cell Division, Secondary oocyte, (arreseted in, metaphase-II), , First Polar body, , Ovulation, Sperm, Polar bodies, usually do not, divide, , Meiosis-II completed, (when sperm cell, contacts plasma, membrane), Ovum, , Polar bodies, (polar body, degenerates), , Second, Polar Body, , Process of oogenesis, , www.aiimsneetshortnotes.com, , Ovulated, Tertiary, Follicles
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Telegram @neetquestionpaper, Human Reproduction, 401, Hormonal Control of Female Reproductive System, The growth, maintenance and functions of the female reproductive, organs are under the hormonal control as described below, GnRH is secreted by the hypothalamus which stimulates the anterior, lobe of pituitary gland to secrete LH and FSH. FSH stimulates the, growth of the ovarian follicles and also increases the development of, egg/oocyte within the follicle to complete the meiosis-I to form, secondary oocyte. FSH also stimulates the formation of oestrogens. LH, stimulates the corpus luteum to secrete progesterone. Rising level of, progesterone inhibits the release of GnRH, which in turn, inhibits the, production of FSH, LH and progesterone., Hypothalamus, GnRH, , Positive Feed Back, , Anterior Lobe of, Pituitary Gland, , Negative Feedback, , LH/FSH, , Ovary, , Oestrogen, Progesterone, , Uterus, , Hormonal control of female reproductive system, , The Menstrual Cycle, Women of reproductive age undergoes a series of anatomical and, physiological changes each month known as the menstrual cycle., These changes occur in three areas–hormone levels, ovarian structure, and uterine structure., On average, the menstrual cycle repeats itself every 28 days. Ovulation, usually occurs approximately at the midpoint of the 28 day cycle,, i. e. , at day 14., The average length of menstrual cycle is 28 days which may vary in, different or even in the same women., , www.aiimsneetshortnotes.com
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402, , Telegram @neetquestionpaper, , Handbook of Biology, , Phases of the, ovarian cycle, , Follicular phase Ovulation, , Luteal phase, , LH, Gonadotropic, hormone, levels, FSH, , Ovarian, cycle, Primary, follicle, , Ovarian, hormone, levels, , Theca Antrum, , Corpus Mature Corpus, luteum corpus, Ovulation formation, luteum albicans, Progesterone, , Oestrogen, (surge at 12-13 day), Inhibin, , Uterine, endometrium, , Uterine, cycle, , Phases of the, uterine cycle, , Follicular or, Proliferative phase, , Menses, , Luteal or secretory phase, , 36.7, Basal body, temperature, (°C) 36.4, DAYS, , 28/0, , 7, , 14, , 21, , 28/0, , The menstrual cycle, , Menopause, It is the complete cessation of the menstrual cycle, which occurs, between the age of 40-50. All the follicles present in the ovary gets, degenerated or ovulated, decline in oestrogen production and vaginal, secretions occur. It results in temporary behavioural changes such as, irritability and depression. It can also lead to osteoporosis., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Human Reproduction, 403, Fertilisation, It is the first step in human development where union of sperm and, ova occurs to form a diploid zygote., It occurs in the ampullary-isthmic junction of the oviduct., Copulation, Formation of, zygote, , Secondary meiotic division, of egg is completed, , Sperm encounters, with secondary, oocyte or egg, , Sperm discharges, into vagina, , Travels into, the oviducts, , Although many millions of sperms are deposited in the vagina, only a, tiny fraction makes it into the oviducts. The rest are killed by the, acidic secretions of the vagina or fail to find their way into the cervix., , Steps of Fertilisation Process, These are as follows, , Sperm Capacitation, It is the process, in which the sperm acquires the capacity to fertilise, the egg by the secretions of the female genital tract., It involves the removal of coating substances present on the surface of, sperms, so that the receptor sites on acrosome are exposed and sperm, become active to penetrate the egg., It takes about 5 to 6 hours., , Acrosome Reaction, It involves the release of various chemicals (sperm lysins) contained in, the acrosome of capacitated sperm., Acrosome reaction occurs in three steps which are carried out by three, different sperm lysins as follows, (i) Hyaluronidase acts on the ground substances of the follicle, cells., , www.aiimsneetshortnotes.com
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404, , Telegram @neetquestionpaper, , Handbook of Biology, , (ii) Corona penetrating enzyme dissolves the corona radiata, (radiating crown) cells that surround the female gamete., (iii) Zona lysins (acrosin) digests the zona pellucida (the clear, zone), a clear gel-like layer immediately surrounding the oocyte., , The Block to Polyspermy, Polyspermy is the entry of more than one sperm into the oocyte., To prevent polyspermy and to ensure monospermy (entry of one sperm, into oocyte), following events occur, (i) Fast block to polyspermy Rapid depolarisation of the egg's, plasma membrane as soon as first sperm contracts the plasma, membrane., (ii) Slow block to polyspermy (cortical reaction) Just after the, penetration of sperm into egg, cortical granules (present, beneath the plasma membrane of egg) fuse with the plasma, membrane and release cortical enzymes., These enzymes harden the zona pellucida and converts it into, the fertilisation envelope hence, blocking other sperm from, reaching the oocyte., Sperm, , Cells of the, corona radiate, Zona, pellucida, , Sperm acrosome, , Perivitelline space, , Acrosomal enzymes, Zona pellucida, Extracellular space, Oocyte plasma, membrane, , Fertilisation envelope, , Cortical granules, Sperm nucleus is, engulfed by oocyte., , Ocyte cytoplasm, Sperm plasma membrane, fuses with plasma membrane, of oocyte, , Release of cortical, enzymes, , Series of events occurring in development of fertilisation envelope, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Human Reproduction, 405, Zygote Formation, Sperm contact with the plasma membrane of the oocyte triggers the, second meiotic division and converts the secondary oocyte to ovum,, which rapidly converts into zygote after the entry of the sperm, nucleus., Zygote contains 46 chromosomes, one set from each parent., , Pre-Embryonic Development, It involves all the changes that occur from fertilisation to the time just, after an embryo implants in the uterine wall., This process starts with cleavage., , Cleavage, It is a series of rapid mitotic divisions of the zygote which converts the, zygote into a multicellular structure (blastocyst or blastula). The, pattern of cleavage in human is holoblastic., Significance of Cleavage, (i) Distribution of the cytoplasm amongst the blastomeres and, (ii) Restoration of the cell size and nucleocytoplasmic ratio., Detailed events occurring in pre-embryonic development are shown, below, Egg is activated, i.e.,, Rapid cellular division converts, metabolism in the zygote, the zygote into a solid ball, and protein synthesis, of cells called morula, increases, (b) 4-cell stage (c) 8-cell stage, Morula is nourished by the, (a) 2-cell stage, Zona pellucida, (d) Morula secretions produced by uterine, Polar body, tubes and enters the uterus in, about 3 to 4 days after ovulation, (e) Blastocyst (early) Accumulation of fluid in, morula converts it to blastocyst, (hollow space of cells)., Fertilisation, Blastocyst remains unattached, in uterus for 2 to 3 days., Zona pellucida begins, to degenerate, Ovulation, , (f) Blastocyst (late), Inner cell mass, which will become the, embryo, , Ovary, Endometrium, Implantation, Uterus, , Trophoblast, Flattened cells which nourish, the blastocysts and give rise to, placenta., , Development of morula and blastocyst, , www.aiimsneetshortnotes.com
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406, , Telegram @neetquestionpaper, , Handbook of Biology, , Implantation, It is the attachment of blastocyst to the uterine lining and digesting its, way into the thickened layer of uterine cavity using enzymes released, by the cells of blastocyst., It occurs 6 to 7 days after fertilisation., The process involves, (a) Cells of trophoblast contact the endometrium, if it is properly, primed by oestrogen and progesterone, cells of uterine cavity at, the contact point enlarge and thicken. Blastocyst usually, implants high on the back wall of the uterus., (b) Trophoblast cells release enzymes, digest a hole in the thickened, endometrial lining and blastocyst bores its way into deeper, tissue of uterine cavity. During this process, blastocyst feeds on, nutrients released from the cells it digests., (c) By day 14, the uterine endometrium grows over the blastocyst,, enclosing it completely. Endometrial cells produce certain, prostaglandins which stimulate the development of uterine, blood vessels. Soon after that, placenta develops., Implantation fails to occur in the following conditions, (i) If endometrium is not properly primed by oestrogen and, progesterone., (ii) If endometrium is not ready or is ‘unhealthy’ because of the, presence of an IUD, use of a “morning after pill” or an, endometrial infection., (iii) If the cells of blastocyst contain certain genetic mutations., Unimplanted blastocysts are absorbed (phagocytised) by the cells of, uterine lining and are expelled during menstruation., , Embryonic Development, It involves the transformation of the blastocyst into the gastrula by the, process called gastrulation. The formation of the primary germ layers, marks the beginning of embryonic development., Gastrulation involves the cell movements called morphogenetic, movements which help the embryo to attain new shape and, morphology. These movements result in the formation of three germ, layers namely ectoderm, mesoderm and endoderm., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 408, , Handbook of Biology, , The primary germ layers of the embryo gives rise to the organs in a, process called organogenesis., Various organs derived from different germ layers are as follows, End Products of Embryonic Germ Layers, Ectoderm, , Mesoderm, , Endoderm, , Epidermis, , Dermis, , Lining of the digestive, system, , Hair, nails, sweat glands, , All muscles of the body, , Lining of the respiratory, system, , Brain and spinal cord, , Cartilage, , Urethra and urinary, bladder, , Cranial and spinal nerves Bone, , Gall bladder, , Retina, lens, and cornea, of eye, , Blood, , Liver and pancreas, , Inner ear, , All other connective tissues Thyroid gland, , Epithelium of nose,, mouth, and anus, , Blood vessels, , Parathyroid gland, , Enamel of teeth, , Reproductive organs and, kidneys, , Thymus, , Role of Extraembryonic Membranes (Foetal Membranes), The growing foetus develops 4 associated membranes called foetal, membranes or extraembyonic membranes which are specialised to, perform different functions., Chorion, Completely surrounds, the embryo, protects it,, takes part in the formation, of placenta., , Allantois, Small and non-functional, in humans except for, furnishing blood to the, placenta., , Foetal, Membranes, , Amnion, Contains amniotic fluid which, prevents desiccation of the, embryo and acts as a protective, cushion that absorbs shocks., , Yolk Sac, Non-functional in humans, except it functions as the site, of early blood cell formation., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Human Reproduction, 409, Foetal Development, It involves the continued organ development and growth and changes, in body proportions. It begins in the eight week of pregnancy and ends, during parturition., , Gestation Period and Parturition, Gestation period is the time period during which the foetus remains in, the uterus. In humans, this period is about 280 days (38-40 weeks)., Parturition is the process of giving birth to a baby. It begins with mild, uterine contractions. During labour pains, contractions increase in, strength and frequency until the baby is born., Following factors play a major role in parturition, (i) Increased level of hormone oxytocin from the foetus and the, mother., (ii) Increase in oxytocin receptors by oestrogen., (iii) Blocking of calming influence of the progesterone by oestrogen., (iv) Expansion of cervix by hormone relaxin., The stepwise approach with oxytocin feed back mechanism in birth is as, follows, Step 1. Baby moves further into mother’s vagina., Step 2. Receptors in cervix get excited., Step 3. Impulses sent to hypothalamus., Step 4. Hypothalamus sends impulses to posterior pituitary., Step 5. Posterior pituitary releases stored oxytocin to blood which, stimulates mother’s uterine muscles to contract., Step 6. Uterine contractions become more vigrous (labour pains)., The cyclic mechanism continues until the birth of the baby., Stages of Childbirth, Childbirth consists of three stages namely, dilation, expulsion and, placental stages., , www.aiimsneetshortnotes.com
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410, , Telegram @neetquestionpaper, , Handbook of Biology, Urinary bladder, Pubic bone, , Vagina, Placenta, Placenta, , Rectum, , Partially dilated, cervix, , Dilation stage, Uterine contractions push the foetal, head lower in the uterus and cause, the relaxin–softened cervix to dilate., , Expulsion stage, Foetus is expelled through, the cervix and vagina., , Uterus, , Umbilical cord, , Placental stage, Placenta is expelled by, uterine contractions, usually within 15 mins, after childbirth., , Placenta, It is the intimate connection between the foetus and the uterine wall of, the mother., It develops from chorion., Chorionic villi are the number of finger-like projections which, develop from the outer surface of chorion and penetrate the uterine, walls to form placenta., The foetal part of placenta is chorion and the maternal part is, decidua basalis., , Types of Placenta, The placenta can be classified into different types on the following basis, (i) Nature of Contact, On the basis of nature of contact, placenta is of two types indeciduate, and deciduate., (a) Indeciduate placenta Chorionic villi are simple, lie in contact, with uterus, they have loose contact, and there is no fusion. At, the time of birth, uterus is not damaged, e.g., Ungulates,, Cetaceans, Sirenians, Lemurs, etc., (b) Deciduate placenta The allantochorionic villi penetrate into, the uterine villi. They are intimately fused. Hence, at the time of, birth, the uterus is damaged and bleeding occurs, e.g., Primates,, Rodentia, Chiroptera, etc., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Human Reproduction, 411, (ii) Distribution of Villi, On the basis of villi distribution, placenta is of five types as follows, Diffused, , Villi are distributed uniformly on the, blastocyst surface except at extreme, ends, e.g., Pig, horse (indeciduate type)., , Zonary, , Cotyledonary, , Villi are arranged in groups,, each group is called cotyledon, which fits into the caruncles, (maternal contact sites) of uterus,, e.g., sheep, cow, deer, (indeciduate type)., , Placental Types, on the Basis of, Villi Distribution, , Intermediate, , Villi are in the form of transverse, bands or zones and penetrate, in the uterus wall, e.g., cat, dog,, bear, elephant, carnivores., (deciduate type)., , Discoidal, , Rare type, shows free villi on, cotyledons, indeciduate, type; e.g., camel, giraffe., , Villi are present as disc on the entire, surface of blastocyst when embryo, grows, it moves away from the uterus, hence, it looks like a disc, deciduate type,, e.g., rat, bat, rabbit., , (iii) Histology, Placenta is classified into 5 types on the basis of number of layers, present between the foetus and uterus., The six layers in between foetal and maternal parts are (i), endothelium of mother blood vessel, (ii) maternal syndesmose, connective tissue, (iii) maternal epithelium, (iv) chorion of foetus, (v), foetus syndesmose connective tissue, (vi) endothelium of foetal blood, vessel., The five placental types are as follows, Epithelio-chorial, , Contains all the six layers,, foetal chorion is in contact, with uterus epithelium,, e.g., pig, horse, lemurs., , Hemoendothelial, Foetus floats in, the mother’s blood,, e.g., rat, rabbit, etc., , Hemochorial, Chorion of foetus in the blood, pool of mother’s uterus,, e.g., bat man, primates, etc., , Syndesmose-chorial, , Placental Types, On the Basis of, Histology, , Allantochorionic villi pierce into, uterus and chorion comes in, contact with syndesmose of uterus,, e.g., sheep, cow., , Endothelio-chorial, Chorion of foetus is in contact, with the endothelium of uterus,, e.g., dog, other carnivores., , www.aiimsneetshortnotes.com
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412, , Telegram @neetquestionpaper, , Handbook of Biology, , Human placenta is deciduate and hemochorial type and it produces, various hormones whose functions are as follows, Hormones Produced by the Placenta, Hormone, , Function, , Human Chorionic, Gonadotropin (hCG), , Maintains corpus luteum during pregnancy,, , Oestrogen (also secreted by, corpus luteum during, pregnancy), , Stimulates growth of myometrium, increasing uterine, strength for parturition (childbirth)., , Progesterone (also secreted, by corpus luteum during, pregnancy), , Suppresses uterine contractions to provide quiet, environment for foetus., , stimulates secretion of testosterone by developing, testes in XY embryos., , Helps prepare mammary glands for lactation., , Promotes the formation of cervical mucous plug to, prevent uterine contamination., Helps prepare mammary glands for lactation., , Human chorionic, somatomammotropin, , Helps prepare mammary glands for lactation., , Relaxin (also secreted by, corpus luteum during, pregnancy), , Softens cervix in preparation of cervical dilation at, parturition., , Believed to reduce maternal utilisation of glucose so, that greater quantities of glucose can be shunted to, the foetus., , Loosens connective tissue between pelvic bones in, the preparation for parturition., , Other functions performed by placenta are listed below, (i) Nutrition It helps to supply all the nutritive elements from, the maternal blood to pass into the foetus., (ii) Excretion The foetal excretory products diffuse into maternal, blood through placenta., (iii) Barrier Placenta serves as an efficient barrier and allows, only necessary material to pass into foetal blood., (iv) Storage Placenta stores glycogen, fat, etc., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Human Reproduction, 413, Summary of Human Pregnancy from Fertilisation to, Birth of the Baby, Week 1, , Week 2, , Week 3, , Fertilisation, cleavage, to form a blastocyst, 4-5 days after, fertilisation. More, than 100 cells., Implantation 6-9, days after, fertilisation., , The three basic layers of the, embryo develop, namely, ectoderm, mesoderm and, endoderm. No research, allowed on human embryos, beyond this stage., , Woman will not have a, period. This may be the first, sign that she is pregnant., Beginning of the backbone., Neural tube develops, the, beginning of the brain and, spinal cord (first organs)., Embryo about 2 mm long., , Week 5, , Week 6, , Week 4, Heart, blood vessels,, blood and gut start, forming. Umbilical, cord developing., Embryo about 5 mm, long., , Brain developing. ‘Limb, Eyes and ears start to form., buds’, small swellings which, are the beginnings of the, arms and legs. Heart is a, large tube and starts to beat,, pumping blood. This can be, seen on an ultrasound scan., Embryo about 8 mm long., , Week 7, , By Week 12, , By Week 20, , All major internal, organs developing., Face forming. Eyes, have some colour., Mouth and tongue., Beginnings of hands, and feet. Foetus is, 17 mm long., , Foetus fully formed, with all, organs, muscles, bones, toes, and fingers. Sex organs, well-developed. Foetus is, moving. For the rest of the, gestation period, it is mainly, growing in size. Foetus is, 56 mm long from head to, bottom. Pregnancy may, begin to show., , Hair beginning to grow,, including eyebrows and, eyelashes. Fingerprints, developed. Finger nails and, toe nails growing. Firm hand, grips. Between 16 and 20, weeks baby usually, felt moving for first time., Baby is 160 mm long from, head to bottom., , Week 24, , By Week 26, , By Week 28, , Eyelids open. Legal, limit for abortion in, most circumstances., , Has a good chance of, survival, if born prematurely., , Baby moving vigorously., Responds to touch and loud, noises. Swallowing amniotic, fluid and urinating., , By Week 30, , 40 Weeks (9 months), , Usually lying head Birth, down ready for birth., Baby is 240 mm from, head to bottom., , www.aiimsneetshortnotes.com
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414, , Telegram @neetquestionpaper, , Handbook of Biology, , Lactation, The production and release of milk after birth by woman is called, lactation. The first milk which comes out from the mother's, mammary glands just after childbirth is known as colostrum., Colostrum is rich in proteins and energy along with antibodies that, provide passive immunity for the new born infant. Milk synthesis is, stimulated by pituitary hormone, prolactin., The release of milk is stimulated by a rise in the level of oxytocin when, the baby begins to nourish. Milk contains inhibitory peptides, which, accumulate and inhibit milk production, if the breasts are not fully, emptied., , The Lactating Breast, The glandular units enlarge considerably under the influence of, progesterone and prolactin. Milk is expelled by contraction of, muscle-like cells surrounding the glandular units. Ducts drain the, milk to the nipple., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 26, Reproductive, Health, According to World Health Organisation (WHO), reproductive health, means a total well-being in all aspects of reproduction, i.e., physical,, emotional, behavioural and social., , Problems Related to Reproductive Health, There are various factors which may lead to reproductive health, problems. These are as follows, Pregnancy, , Complications, of Abortions, , Infertility, , Reproductive, Health, Problems, , Delivery, , Menstrual, Problems, , Health of Mothers, , STDs, Contraception, , Population Explosion, It is the rapid increase of a population attributed especially to an, accelerating birth rate, decrease in infant mortality and an increase in, life expectancy., , www.aiimsneetshortnotes.com
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416, , Telegram @neetquestionpaper, , Handbook of Biology, , Reasons for High Population Growth, (i) Spread of education People of the country are being, educated about the diseases., (ii) Control of diseases Control of various communicable, diseases is in practice., (iii) Advancement in agriculture Farmers are educated to, develop high yielding crops., (iv) Storage facilities A good quantity of grains can be stored, easily., (v) Better transport This protects from famines., (vi) Protection from natural calamity It decreases death rate., (vii) Government efforts Government is making efforts to, provide maximum informations to the farmers., Effects of Population Explosion, Overpopulation leads to the number of national and individual family, problems. These are as follows, Poverty, Energy Crisis, , Education, Problem, , Unhygienic, Condition, , Scarcity of Food, , Effects of, Population, Explosion, , Unemployment, , Housing Problem, Pollution, , It may also lead to socio-economic problems due to the shortage of, space, food, educational and medical facilities., , Strategies to Improve Reproductive Health, These are as follows, , 1. Reproductive and Child Healthcare (RCH) Programmes, They aim to create awareness among people about various, reproduction related aspects and provide facilities and support for, building up a reproductively healthy society., This programme is a part of family planning programme which was, initiated in 1951., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Reproductive Health, 417, The various parameters of these programmes are as follows, RCH Programmes, , Knowledge of Growth of, Reproductive Organs, and STDs, Proper information about reproductive, organs, adolescence, safe and hygienic, sexual practices, Sexually Transmitted, Diseases (STDs) etc, would, help to lead a reproductively healthy life., , Medical Facilities, Better awareness about sex related, problems, prenatal care of mother,, medically assisted deliveries and, postnatal care of mother and infant, decreases maternal and infant mortality., Better detection and cure, of Sexually Transmitted Diseases (STDs), and increased medical facilities for, sex-related problems, etc., indicate, improved reproductive health of male, and female individuals and children., , Sex Education, It should be introduced in schools, and encouraged to provide right, information about myths and, misconceptions about sex-related, aspects., , Prevention of Sex Abuse, and Sex Related Crime, Awarness of problems due to, uncontrolled population growth,, social evils like sex abuse and, sex-related crimes, etc., need to, be created, so that people should, think and take up necessary, steps to prevent them and thereby, build up a reproductively healthy, society., , 2. Research in Reproductive Health Area, It should be encouraged and supported to find out new methods., ‘Saheli’, a new oral contraceptive for the females was developed by our, scientists at Central Drug Research Institute (CDRI) in Lucknow,, India. It is a non-hormonal contraceptive., , 3. Birth Control, It refers to the regulation of conception by preventive methods or, devices to limit the number of offsprings., Contraception It includes the contraceptive methods, i.e., the, methods which deliberately prevent fertilisation., , www.aiimsneetshortnotes.com
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418, , Telegram @neetquestionpaper, , Handbook of Biology, , The various methods of birth control are listed in the following table, Methods of Contraception and Birth Control, Methods, , Basis of Action, , Note on Uses, , Relative, Disadvantages, , Barrier Methods, Condom, , A thin, strong rubber, sheath, prevents the, sperm to enter the, vagina., , Placed over erect, penis just before, sexual intercourse., , Not as reliable as, the pill., Relies on male., May tear or slip off., , Femidom, , Female condom-a thin, rubber or polyurethane, tube with a closed end,, which fits inside vagina, and open end has two, fixable rings, one on, each end, to keep it in, place., , Inserted before, intercourse and, removed any time, later., , Difficult to insert., Can break or, leak. Expensive, than male, condom., , Diaphragm/Cap, , A flexible rubber dome, which fits over the cervix, and prevents entry of, sperm to uterus. Used, with a spermicidal, cream or jelly (a, spermicide is a chemical, which kills sperms)., , Inserted before, intercourse. Must, be left in place, at least, 6 hours after the, intercourse., , Suggestion of, doctor is must for, proper size, selection., , Spermicide, , Chemical which kills, sperm., , Placed in vagina to, cover the lining of, vagina and cervix., Effective for about, 1 hour., , High failure rate,, if used on its, own., , Sponge, , Polyurethane sponge, impregnated with, spermicide, fits over, cervix, disposable., , Fits up to 24 hours, before intercourse., Leave in place for, at least 6 hours after, intercourse., , High failure rate., , www.aiimsneetshortnotes.com, , Its training is, required to fit., Occasionally, causes abdominal, pain. It should, not be left for, more than 30, hours as it may, cause toxic shock, syndrome., Examination, required after every, 6 months that cap, is of right size.
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Telegram @neetquestionpaper, Reproductive Health, 419, Methods, , Relative, Disadvantages, , Basis of Action, , Note on Uses, , Contains the female sex, hormones-oestrogen, and progesterone., Prevents development of, eggs and ovulation by, inhibiting the secretion, of FSH. Acts on cervical, mucus to prevent the, penetration of sperm., , One taken orally, each day during, first 3 weeks of, cycle. After week 4,, menstruation starts, and the pill is, started again., , Short-term side, effects, may, include nausea,, fluid retention and, weight gain., Long-term side, effects not fully, understood, but, increased risk of, blood clotting may, occur in some, women. Not, recommended for, older women., , Hormonal Methods, Pill, , Prevents the blastocyst, implantation., , Minipill, , Contains progesterone, only. Ovulation may, occur, but cervical, mucus is thickened,, preventing entry of, sperms., , Must be taken, within 3 hours, after intercourse, everyday., , May cause, headache,, nausea, weight, gain., , IUD (IntraUterine Device), or Coil, , Ist generation, (non-medicated, e.g.,, lippes loops, rings)., , It is placed in, cervix, acts as, spermicide within, the uterus., , May cause, bleeding and, discomfort. IUD, may slip out., , 2nd generation (copper, devices, e.g., copper, T-220)., 3rd generation, (hormonal devices, e.g.,, progestasert)., , Natural Methods (NFP stands for Natural method of Family Planning), Abstinence, , Avoid sexual intercourse., , —, , Restricts emotional, development of a, relationship., , Rhythm method, , Avoid sexual intercourse, around the time of, ovulation (total abstinence, for about 7-14 days)., , —, , High failure rate,, even higher if, periods are irregular., Requires good, knowledge of body, and good recordkeeping. Requires a, period of, abstinence., , www.aiimsneetshortnotes.com
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420, , Telegram @neetquestionpaper, , Handbook of Biology, , Methods, , Relative, Disadvantages, , Basis of Action, , Note on Uses, , Temperature, method, , Note the rise in, temperature at ovulation, (due to rise in, progesterone) and avoid, sexual intercourse at, these times., , —, , As above., , Coitus, interruptus, (withdrawl), , Penis is withdrawn from, vagina before ejaculation., , —, , HIgh failure rate., Requires much, self-discipline., Penis may leak, some sperms, before ejaculation., , Lactational, amenorrhea, , Sucking stimulus, prevents the generation, of normal preovulatory, LH surge hence,, ovulation does not occur., , Effective only for, initial three four, months., , —, , Sterilisation (Surgical methods), Vasectomy, , Vas deferens are severed, and tied., , —, , Very difficult to, reverse. Need to, use alternative, method upto, 2 to 3 months, after vasectomy, , Tubectomy, , Both oviducts are severed, and tied (now laproscopic, method are used)., , —, , Even more, difficult to reverse, than vasectomy., , Termination (Its not a part of contraception), Morningafter Pill, , Contains RU486, an, antiprogesterone., , Taken within, 3 days of sexual, intercourse., , For use only in, emergencies., Long-term effects, not known., , Abortion, (discussed later, in this chapter, as MTP), , Up to 24 weeks, , Premature, termination of, pregnancy by, surgical, intervention., , Risk of infertility, and other, complications., Emotionally, difficult and, ethically wrong., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Reproductive Health, 421, Medical Termination of Pregnancy (MTP), MTP or induced abortion is the termination or removal of embryo from, the uterus by using pharmacological or surgical methods. It is, considered safe during the first trimester, i.e., up to 12 weeks of, pregnancy., MTP, Significance, , Drawbacks, , • Plays significant role, , • Misused to abort, , in decreasing human, population., • Helps in getting rid, of unwanted and, harmful pregnancies., , the normal female, foetuses., • Raises many emotional,, ethical, religious and, social issues., , Sexually Transmitted Diseases (STDs), These are the diseases or infections which are transmitted through, sexual intercourse. They are also called Veneral Diseases (VD) or, Reproductive Tract Infections (RTI)., Various STDs are as follows, (i) Syphilis Caused by bacterium Treponema pallidium which, grows and multiplies in warm, moist area of reproductive tract,, causes skin lesions, swollen joints, heart trouble, etc., (ii) Gonorrhoea Caused by bacterium Neisseria gonorrhoea and, mainly affects women, causes pain around genitalia,, pus-containing discharge, etc, (iii) Genital herpes Caused by Herpes simplex virus, causes, vesiculopustular lesions, ulcers over external genitalia, vaginal, discharge, etc., (iv) Chlamydiasis Caused by bacterium Chlamydia trachomatis,, causes inflammation of Fallopian tubes, cervicities,, mucopurulent, epididymitis, urethritis, etc., (v) Trichomoniasis Caused by protozoan Trichomonas vaginalis,, causes vaginitis, foul smelling and burning sensation in, females. Causes urethritis, epididymitis and prostatis in males., , www.aiimsneetshortnotes.com
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422, , Telegram @neetquestionpaper, , Handbook of Biology, , Other STDs are as follows, STDs, , Pathogen, , Symptoms, , Chancroid, , Haemophilus ducreyi bacterium, , Ulcers over external genitalia., , Genital warts, , Human Papilloma Virus (HPV), , Warts over external genitalia,, vaginal infection., , Hepatitis-B, , Hepatitis–B Virus (HBV), , Fatigue, jaundice, cirrhosis, etc., , Candidiasis, , Candida albicans (vaginal yeast), , Inflammation of vagina, thick,, cheesy discharge etc., , Acquired Immuno Deficiency Syndrome (AIDS), It is a fluid transmitted disease with possibility of transmission, through body fluids like blood, semen, etc., As sexual intercourse is the best suitable mode of fluid transmission, that’s why it is misleaded to be one of the STDs. Other transmission, modes include blood transfusion, use of same syringes and needles, etc., , Preventive Measures (Prophylaxis) of STDs, Prevention of sexually transmitted diseases can be done by the simple, practices given below, (i) Avoid sex with unknown partners/multiple partners., (ii) Always use condoms during coitus., (iii) Use sterilised needles and syringes., (iv) Education about the sexually transmitted diseases should be, given to the people., (v) Any genital symptoms such as discharge or burning during, urination or unusual sore or rash could be a signal of STDs and, the person should seek medical help immediately., (vi) Screening of blood donors should be mandatory., , Infertility, It is the failure to achieve a clinical pregnancy after 12 months or more, of regular unprotected sexual intercourse. The reason for this could be, physical, congenital diseases, drugs, immunological or psychological., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Reproductive Health, 423, Primary Infertility, If the conception has never occurred, the condition is called primary, infertility., , Secondary Infertility, If the patient fails to conceive after achieving a previous conception,, the condition is called secondary fertility., Alcoholism, Causes defective, spermatogenesis., , Cryptorchidism, , Reasons of, Infertility in, Males, , Erection, Dysfunctioning, Male penis unable to erect, or erect for shorter period., , Faulty, Spermatogenesis, Due to genetic disorder or, drug use, sperm formation, process is interrupted., , Oligospermia, Low sperm count due to the, infection of seminal vesicle,, raised scrotal temperature, etc., , Testes are unable to, descend in scrotal sac., , Gonadotropin, Deficiency, Low secretion of, hormones supporting, spermatogenesis, (LH and FSH)., , Obstruction of, Efferent Ducts, Sperm conducting tubes are, blocked due to vasectomy or, some diseases., , Chromosome, Deletion, Male chromosome, i.e.,, Y-chromosome may get, deleted due to genetic, disorders., , Reasons of infertility in males, Anovulation, Vaginal and, Cervical Infection, , No formation of, Corpus luteum., , Blockage of, Fallopian Tube, Fallopian tubes may get blocked, due to inflammation (salpingitis),, congenital tubule obstruction, etc., , Polycystic Ovary, Presence of multiple, cysts in ovary., , Irregular Menstrual Cycle, Menstrual cycle may get disturbed, due to polycystic ovary,, endometriosis, stress, etc., , Bacterial, fungal infections, like gonorrhoea, chlamydia, may cause infertility., , Reasons of, Infertility in, Females, , Ectopic, Pregnancy, Embryo implants, outside the uterus., , Fertilisation and, Implantation Failure, It may be caused due to, endometrial damage,, drug use, etc., , Gonadotropin, Deficiency, Hormones supporting the, process of ovulation are, deficent (LH and FSH)., , Reasons of infertility in females, , www.aiimsneetshortnotes.com
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424, , Telegram @neetquestionpaper, , Handbook of Biology, , Assisted Reproductive Technology (ART), These are the applications of reproductive technologies to solve, infertility problems., They include the following techniques, 1. In Vitro Fertilisation (IVF), It is used as a remedy for infertility. A woman’s egg cells are combined, with sperm cells outside the body in laboratory conditions to become, fertilised. The fertilised egg (zygote) is then transferred to the patient’s, uterus. Hence, IVF refers to any biological procedure that is performed, outside the organism’s body., 2. Intracytoplasmic Sperm Injection (ICSI), In this technique, sperm is injected into the cytoplasm of an egg using, microinjection. It is effective when sperms are unable to penetrate the, egg on its own due to low sperm count, abnormal sperms, etc., 3. Intra Uterine Transfer (IUT), It involves the transfer of an embryo to the uterus when it is with more, than 8 blastomeres. Similarly, when the zygote is placed in the, Fallopian tube, the technique is known as Zygote Intra Fallopian, Transfer (ZIFT)., 4. Gamete Intra Fallopian Transfer (GIFT), In this technique, eggs are removed from the ovaries and placed in one, of the Fallopian tubes along with the sperm. This allows the, fertilisation to occur within the woman’s body (in vivo fertilisation)., , 5. Artifcial Insemination (AI), In this technique, the semen collected either from husband or a, healthy donor is artificially introduced either into the vagina or into, the uterus (IUI–Intra-Uterine Insemination) of the female. It is, commonly used in cases where male partners are unable to inseminate, the female due to very low sperm counts., , Detection of Foetal Disorders During, Early Pregnancy, No one wants to pass on any abnormality to the next generation, but, all the pregnancies carry some degree of risk. Fortunately, it is now, possible to detect hundreds of genetic mutations and chromosomal, abnormalities very early in the course of development using invasive, and non-invasive techniques., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Reproductive Health, 425, 1. Invasive Techniques, These involves the insertion of an instrument into the body. It involves, amniocentesis, Chronic Villi Sampling (CVS), etc. Amniocentesis (also, referred to as Amniotic Fluid Test or AFT) is a medical procedure, used in prenatal diagnosis of chromosomal abnormalities and, foetal infections. A small amount of amniotic fluid, which contains, foetal tissues is extracted from the amnion or amniotic sac surrounding, the developing foetus and the foetal DNA is examined for genetic, abnormalities. Using this process, the sex of a child can be determined, and hence, this procedure has some legal restrictions in some gender, biased countries., , 2. Non-Invasive Techniques, These techniques do not involve the introduction of any instruments, into the body. It involves ultrasound imaging, maternal blood, sampling, etc., In ultrasound imaging, high frequency sound waves are utilised to, produce visible images from the pattern of the echos made by, different tissues and organs., Maternal blood sampling technique is based on the fact that few foetal, blood cells leak across the placenta into the mother’s bloodstream., A blood sample from the mother provides enough foetal cells that can, be tested for genetic disorders., , www.aiimsneetshortnotes.com
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426, , Telegram @neetquestionpaper, , Handbook of Biology, , 27, Principles of, Inheritance and, Variation, Through the process of reproduction, all organisms produce offspring, like themselves. The transfer of characters from one generation to the, next generation is the central idea of this chapter., , Heredity, It is the study of transmission of characters from parents to offspring, or from one generation to the next. Thus, the transmission of, structural, functional and behavioural characteristics from one, generation to another is called heredity., , Basis of Heredity, Mendel (1866) proposed that inheritance is controlled by paired, germinal units or factors, now called genes. These represent small, segments of chromosome., The genetic material present in chromosomes is DNA. Genes are, segments of DNA, called cistrons. Therefore, DNA is regarded as the, chemical basis of heredity., , Inheritance, It is the process by which characters or traits pass from one generation, to the next. Inheritance is the basis of heredity., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Principles of Inheritance and Variation, 427, Variations, It is the difference in characteristics shown by the individuals of a, species and also by the offspring or siblings of the same parents., Variations, , Somatic, or, Somatogenic variations, (These variations affect the somatic, cells of organisms. These are also, known as modifications of acquired, characters.), , Germinal, or, Blastogenic variations, (These are inheritable variations, in germinal cells. These may, arise due to mutations.), These are of two types, , These can be caused by, , Environmental factors, Environmental factors such, as light, temperature and nutrition affect, the physical features of both animals and plants., , Continuous, These are fluctuating, variations, which are, caused due to rare, variety and species., , Discontinuous, Use and disuse of organs, Continuous use and disuse make, the body organ stronger and, weaker, respectively., , These are sudden, but inheritable, changes, originating, due to mutation, etc., , Conscious efforts, Animals with intelligence, show such processes,, e.g., education, slim bodies, etc., , Terms Related to Genetics, 1. Characters It is a well-defined morphological or physiological, feature of an organism., 2. Trait It is the distinguishing feature of a character., 3. Gene Inherited factor that determines the biological character, of an organism., 4. Allele A pair of contrasting characters is called alleles or, alternate forms of genes are called alleles., 5. Dominant allele The factor or an allele which can express, itself in both homozygous and heterozygous state., 6. Recessive allele The factor or allele which can express itself, only in homozygous state., 7. Wild allele The allele which was originally present in the, population and is dominant and widespread., , www.aiimsneetshortnotes.com
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428, , Telegram @neetquestionpaper, , Handbook of Biology, , 8. Homozygous condition The state in which organism has, two similar genes or alleles of a particular character, e.g., TT, or tt., 9. Heterozygous condition In this, the organism contains two, different alleles for a particular character, e.g., Tt., 10. Monohybrid cross When only one allelic pair is considered in, cross breeding., 11. Dihybrid cross When two allelic pairs are used in crossing, it, is called dihybrid cross., 12. Genotype Genetic constitution of an individual is called, genotype., 13. Phenotype External features of an organism., 14. Punnet square It is a checker board which was invented by, RC Punnett and used to show the result of a cross between two, organisms., 15. Polyhybrid cross Involvement of more than two allelic pairs, in a cross is called polyhybrid cross., 16. F1 or First Filial generation The second stage of Mendel's, experiment is called F1-generation., 17. Hybrid vigour or heterosis The superiority of hybrid over, either of its parents in one or more traits., 18. Gene pool All the genotypes of all organisms in a population, are combinely called gene pool., 19. Genome It is the complete set of chromosomes where every, gene is present singly as in gamete., 20. Pureline or pure breeding line It is a strain of individuals, homozygous for all genes considered. The term was coined by, Johannsen., 21. Haploid, diploid and polyploid cell A single genome is, present in haploid, two in diploid and many genomes are, present in polyploid cells., 22. Test cross The cross of F1 offsprings with their recessive, parents is called test cross., 23. Back cross The cross of an organism with the organism of its, previous generation is known as back cross., 24. Reciprocal cross A cross in which same two parents are used, in such a way that, if in one experiment ‘A’ is used as female, parent and ‘B’ is used as the male parent, in other experiment ‘A’, will be used as male parent and ‘B’ is used as female parent., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 429, Principles of Inheritance and Variation, Gregor Johann Mendel, He was born on July 22, 1822 in Austria. He graduated from, Gymnasium in 1840. In 1843, Mendel was admitted to the Augustinian, Monastery at Brunn, where he took the name Gregor. From 1851-53, he studied mathematics and natural science., In spring of 1856, he began experimenting with pea plants. In 1866,, his paper ‘Experiment on Plant Hybridisation’ published in volume, IV of the proceedings of the natural society. He died on January 6,, 1884 and was buried in Brunn central cemetery., Mendel’s experiments involved four steps, 1. Selection The selection of characters for hybridisation is the, first and an important step., 2. Hybridisation The pollination and hybridisation between, the individuals of two different /contrasting characteristics., 3. Selfing It is the specific hybridisation between the organisms, of same origin (siblings)., 4. Calculation The counting and categorising the products on, the basis of character identified takes place in calculation., Mendel performed his experiments on pea plant and chose seven, contrasting characters in it for observation., These, (i), (ii), (iii), (iv), (v), (vi), (vii), , are, Colour of seed, Shape of seed, Flower colour, Colour of pod, Shape of pod, Position of flower, Height of plant, , www.aiimsneetshortnotes.com
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430, , Telegram @neetquestionpaper, , Handbook of Biology, , These characters and their inheritance patterns are given in the, following table, Character or, Trait Studied, , Parent forms, Crossed (F1 Cross), , F1 Phenotype, , Total, F2 Products, Dominant form,, Recessive form, , Actual, Ratio, , Chromosome, Location, , All yellow, , 6022 yellow,, 2001 green, , 8023 3.01 : 1, , 1, , Shape of seed, , All round, , 5474 violet,, 1850 wrinkled, , 7324 2.96 : 1, , 7, , Flower colour, , All violet, , 705 violet,, 224 white, , 929, , 3.15 : 1, , 1, , All green, , 428 green,, 152 yellow, , 580, , 2.82 : 1, , 5, , All inflated 882 inflated,, 1181 2.95 : 1, 299 constricted, , 4, , Colour of seed, , ×, Green, Yellow, (cotyledon), , ×, , Violet, , White, , Colour of pod, Green, , ×, Yellow, , Shape of pod, Inflated, , ×, Constricted, , Position of, flower, , All axial, , 651 axial,, 207 terminal, , 858, , 3.14 : 1, , 4, , All tall, , 787 tall,, 277 dwarf, , 1064 2.84 : 1, , 4, , ×, Axial, , Terminal, , Height of plant, , Tall, , Dwarf, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Principles of Inheritance and Variation, 431, Emasculation and Bagging, Mendel required both self and cross-fertilisation within the plants for, his experiments. Due to its self-fertilising nature, the anthers of pea, plants require removal before maturity (emasculation) and the stigma, is protected against any foreign pollen (bagging). Through the process, of emasculation and bagging, the pollen of only selected parent can be, used for cross-fertilisation., , Inheritance of One Gene/Monohybrid Cross, Mendel performed several experiments on pea by considering one, character at a time., It is a cross made to study simultaneous inheritance of a single pair of, Mendelian factors., The schematic presentation of the monohybrid cross is as follows, Parents, , &, , Tall Plant, (TT), , F1 -generation, , %, , × Dwarf Plant, (tt), Cross-pollination, , All Tall Plants, (Tt Tt), (selfing/self-cross), , F2 -generation, , Tall, , Tall, , (TT), , Tall, (Tt), , Dwarf, , (Tt), , (tt), , Selfing, All tall, (TT), , 3 2 1, , F3 -generation, , 3 Tall : 1Dwarf 3 Tall : 1Dwarf, (tt), (tt), (Tt), (Tt), , All dwarf, (tt), , Monohybrid cross in pea plant, , Mendel’s Laws of Inheritance, From the three laws of inheritance (i.e., Law of dominance, Law of, segregation and Law of independent assortment), the first two laws are, based on the monohybrid cross., , www.aiimsneetshortnotes.com
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432, , Telegram @neetquestionpaper, , Handbook of Biology, , These are explained in detail below, , 1. Law of Dominance, According to this law, ‘when a cross is made between two homozygous, (pure line) individuals considering contrasting trait of simple character, then the trait that appears in F1 hybrids is called dominant and the, other one that remains masked is called recessive trait’., In pea plant, out of the 7 characters, Mendel studied the dominant and, recessive traits. These characters are discussed earlier., The dominant and recessive traits are also found in other animals, e.g.,, Cat, , Cattle, , Dog, Drosophila, , Salamander, , (a) Skin colour, , Tabby colour is dominant over black or, blue., , (b) Length of hair, , Short hair are dominant over long hair, (Angora)., , (a) Colour of face, , White face colour is dominant over coloured, face., , (b) Horn, , Polled or hornless are dominant over, horned cattle., , (a) Skin colour, , Grey colour is dominant over black colour., , (b) Tail, , Stumpy tail is dominant over normal tail., , (a) Eye colour, , Red colour is dominant over white., , (b) Wings, , Flat and yellow wings are dominant over, curled and white., , (c) Body colour, , Grey body colour is dominant over white., , Body colour, , Dark body colour is dominant over light., , The law of dominance explains why individuals of F1-generation, express the trait of only one parent and the reason for occurrence of 3:1, ratio in F2 individuals., , Exceptions to Law of Dominance, These are as follows, (i) Incomplete Dominance/Blending Inheritance (Correns, 1903), It is also known as Intermediate or Partial or Mosaic inheritance., When F1 hybrids exhibit a mixture or blending of characters of two, parents, it is termed as blending inheritance., It simply means that the two genes of allelomorphic pair are not, related as dominant or recessive, but each of them expresses, themselves partially, e.g., 4 O'clock plant (Mirabilis jalapa),, snapdragon (Antirrhinum) and homozygous fowl. In 4 O’clock, plant when a cross is made between dominant (red) and recessive, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 433, Principles of Inheritance and Variation, (white) variety, the result of F2-generation shows deviation from, Mendel’s predictions., Here, both phenotypic and genotypic ratios came as 1 : 2 : 1 for, Red : Pink : White., (ii) Codominance, The phenomenon of expression of both the alleles in a heterozygote is, called codominance., The alleles which do not show dominant-recessive relationship and are, able to express themselves independently when present together are, called codominant allele, e.g., coat colour in short horned, cattles and MN blood group in humans., In short horned cattle, when a cross is made between white (dominant), and red (recessive) variety, appearence of all Roan offsprings in, F1-generation and then white, roan and red in 1 : 2 : 1 ratio in, F2-generation show codominance of both the colours in roan., The roan coloured F2 individuals in above cross have both red and, white hairs in the form of patches but no hair is having the, intermediate colour., (iii) Pleiotropic Gene, The ability of a gene to have multiple phenotypic effects, because it, influences a number of characters simultaneously, is known as, pleiotropy and such genes are called pleiotropic genes., It is not essential that all traits are equally influenced, sometimes it is, more evident in case of one trait (major effect) and less evident in other, (minor effect), e.g., in garden pea, the gene controlling flower colour,, also controls the colour of seed coat and the presence of red spot on leaf, axil., , 2. Law of Segregation/Law of Purity of Gametes, According to this law, ‘In F1 hybrid, the dominant and recessive, characters though remain together for a long time, but do not, contaminate or mix with each other and separate or segregate at the, time of gamete formation. Thus, the gamete formed receives either, dominant or recessive character out of them.’, For proper understanding of Mendel's law of segregation, the, formation of hybrid is considered from pureline homozygous parents, through monohybird cross given before first law., As the purity of gametes again established in F2-generation, it is called, law of purity of gametes., , www.aiimsneetshortnotes.com
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434, , Telegram @neetquestionpaper, , Handbook of Biology, , Inheritance of Two Genes/Dihybrid Cross, These crosses are made to study the inheritance of two pairs of, Mendelian factors or genes., The schematic representation of the dihybrid cross is as follows, Green wrinkled, pea plant, yyrr, , Gametes, , yr, , F1- generation, , Yellow round (Dihybrid), (Yy Rr), Selfing, , %, &, , YR, , Yr, , YYRR, YR (Yellow round), , YYRr, (Yellow round), , yR, YyRR, (Yellow round), , yr, YyRr, (Yellow round), , Yr, , YYRr, YyRr, YYrr, Yyrr, (Yellow round) (Yellow wrinkled) (Yellow round) (Yellow wrinkled), , yR, , YyRR, (Yellow round), , yr, , yyrr, Yyrr, yyRr, YyRr, (Yellow round) (Yellow wrinkled) (Green round) (Green wrinkled), , yyRR, YyRr, (Yellow round) (Green round), , yyRr, (Green round), , 3, , YR, , Parents, , 2, , ×, , 1, , Yellow round, pea plant, YYRR, , F2- generation, Phenotypic ratio, Yellow round : 9, Green round, :3, Yellow wrinkled : 3, Green wrinkled : 1, , Dihybrid cross in pea plant, , Exceptions to Law of Segregation, These are as follows, (i) Complementary Genes, The two pairs of non-allelic dominant genes, which interact to, produce only one phenotypic trait, but neither of them (if present, alone) produces the trait in the absence of other. It shows the, phenotypic ratio of 9 : 7., , www.aiimsneetshortnotes.com
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436, , Telegram @neetquestionpaper, , Handbook of Biology, , 3. Law of Independent Assortment, This law states that, ‘the inheritance of one character is always, independent to the inheritance of other character within the same, individual’. The dihybrid cross of Mendel can be a very good example of, independent assortment., , Exceptions to Law of Independent Assortment, These are as follows, (i) Supplementary Genes, Two independent dominant gene pairs, which interact in such a way, that one dominant gene produces its effect irrespective of the presence, or absence of other, e.g., the coat colour in mice. The cross is, represented as, Albino, cc aa, , Agouti, CC AA, , ca, , CA, , P1 -generation, , Gametes, , Agouti, Cc Aa, , F1-generation, , Gametes, , CA, , cA, , Ca, , ca, , Cc AA, cA (Agouti), 5, , cc AA, (Albino), 1, , Cc Aa, cc Aa, (Agouti) (Albino), 2, 6, , CC Aa, Ca (Agouti), 7, , Cc Aa, (Agouti), 8, , CCaa, (Black), 1, , ca, , Cc Aa, (Agouti), 9, , cc Aa, Cc aa, (Albino) (Black), 3, 3, , Cc aa, (Black), 2, cc aa, (Albino), 4, , F2- generation, Phenotypic ratio, , 1 2 3, , Gametes, , CC AA Cc AA, CC Aa, Cc Aa, CA, (Agouti) (Agouti) (Agouti) (Agouti), 3, 1, 2, 4, , Agouti : 9, Black : 3, Albino : 4, , Interaction of supplementary genes in mice for coat colour, , Here, the presence of gene C produces black colour which along with, gene A changes its expression in agouti colour. Thus in all,, combinations with at least one C and one A produce agouti colour., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Principles of Inheritance and Variation, 437, (ii) Duplicate Gene, The two pairs of genes which determine same or nearly same, phenotype, hence either of them is able to produce the character. The, duplicate genes are also called pseudoalleles, e.g., fruit shape in, Shepherd’s purse., The inheritance can be seen as, Triangular, TT DD, , Elongated, tt dd, , TD, , td, , P1 -generation, Gametes, , F1- generation, , Triangular, Tt Dd, , Td, , tD, , td, , TD, , TT DD, , TT Dd, , Tt DD, , Tt Dd, , Td, , TT Dd, , TT dd, , Tt Dd, , Tt dd, , tD, , Tt DD, , Tt Dd, , tt DD, , tt Dd, , td, , Tt Dd, , Tt dd, , tt Dd, , tt dd, , (elongated), , 123, , TD, , F2- generation, Phenotypic ratio, , 1 2 3, , Gametes, , Gametes, , Triangular : 15, Elongated : 1, , Interaction of duplicating genes in Shepherd’s, purse for seed pod’s shape, , (iii) Collaborator Gene, In this, the two gene pairs which are present on separate locus,, interact to produce totally new trait or phenotype, e.g., inheritance of, comb in poultry., , www.aiimsneetshortnotes.com
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438, , Telegram @neetquestionpaper, , Handbook of Biology, Rose comb, RRpp, , Pea comb, rrPP, , Rp, , rP, , P -generation, Gametes, , Walnut comb, RrPp, Gametes, , Rp, , rP, , RRPP, , RRPp, , RrPP, , RrPp, , (Walnut), , (Walnut), , (Walnut), , (Walnut), , 2, , 3, , 4, , RRPp, , RRpp, , RrPp, , Rrpp, , (Walnut), , (Rose), , (Walnut), , (Rose), , 5, , 1, , 6, , RrPP, , RrPp, , 1, , Gametes, , Rp, , rP, , (Walnut), , rp, , (Walnut), , 8, , 7, , rp, , 2, rrPp, , rrPP, , (Pea), , (Pea), , 1, , 2, , RrPp, , Rrpp, , rrPp, , rrpp, , (Walnut), , (Rose), , (Pea), , (Single), , 9, , 3, , 3, , 1, , F2- generation, Phenotypic ratio, , 1 2 3, , RP, , 123, , RP, , F1- generation, , Walnut, Rose, Pea, Single, , :9, :3, :3, :1, , Inheritance of rose and pea comb in poultry, , Multiple Allelism, It is the presence of more than two alleles for a gene, e.g., ABO blood, group in human beings is controlled by three alleles, but only two of, these are present in an individual., Polygenic Inheritance, Genes when acting individually have a small effect but that collectively, produce a significant phenotypic expression are called polygenes, e.g.,, genes for height or weight. The polygenes show polygenic inheritance., , Chromosomal Theory of Inheritance, Walter Sutton and Theodore Boveri in 1902 united the knowledge, of chromosomal segregation with Mendelian principles and called it, chromosomal theory of inheritance., According to this theory,, (i) All hereditary characters are carried with sperms and egg cells,, as they provide bridge from one generation to the other., (ii) The hereditary factors are carried in the nucleus., (iii) Chromosomes are also found in pairs like the Mendelian alleles., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Principles of Inheritance and Variation, 439, (iv) The two alleles of a gene pair are located on homologous sites on, the homologous chromosomes., (v) The sperm and egg have haploid sets of chromosomes, which, fuse to re-establish the diploid state., (vi) The genes are carried on the chromosomes., (vii) Homologous chromosomes synapse during meiosis and get, separated to pass into different cells. This is the basis for, segregation and independent assortment., G1, , Meiosis-I, anaphase, , G2, , Meiosis-II, anaphase, , Germ cells, , Bivalent, , Meiosis and germ cell formation in a cell with four chromosomes, , Sex-Determination, It is the method by which the distinction between male and female is, established in a species. It is usually under genetic control of specific, chromosomes called sex chromosomes or allosomes., There are five main genetic mechanisms of sex-determination, , (i) XX-XY Method, Parents, Gametes, , Male, AA+XY, A+X, , Offsprings AA+XX, Female, , ×, , A+Y, , AA+XX, Female, , Female, AA+XX, A+X, , AA+XY, Male, , A+X, , AA+XY, Male, , Examples are mammals (as in humans)., , www.aiimsneetshortnotes.com
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440, , Telegram @neetquestionpaper, , Handbook of Biology, , (ii) XX-XO Method, In this, female has XX chromosomes and produces homogametic eggs,, while male has only one chromosome and produces two types of, sperms, e.g., gynosperms (with X) and androsperms (without X),, e.g., insects and roundworms., Parents, Gametes, , Male, AA+XO, A+X, , A+X, , A+O, , Offsprings AA+XX, Female, , Female, AA+XX, , ×, , AA+XX, Female, , AA+XO, Male, , A+X, , AA+XO, Male, , (iii) ZW-ZZ Method, In this, the male is homogametic and female is heterogametic,, e.g., certain insects, fishes, reptiles and birds., , (iv) ZO-ZZ Method, In this, female is heterogametic while the male is homogametic,, e.g., moths and certain butterflies., , (v) Haploid-Diploid Method, In this method, the unfertilised egg develops into male (Arrhenotoky), while fertilised egg develops into female. This type of sex-determination, is the characteristic feature of insects like honeybees, ants, etc., Male, (n), , Female, (2n), , Mitosis, Sperms (n), , Meiosis, Egg (n), , Sex-Determination in Humans, The human shows XY type of sex-determination. Out of total (23 pairs), chromosomes, 22 pairs are exactly similar in both males and females,, known as autosomes., The female contains a pair of X-chromosome and male contains both, X and Y-chromosomes. The sex is determined by the genetic make up, of sperm., During spermatogenesis among males, two types of gametes are, produced, 50% of the total sperms carry X-chromosomes and the rest, 50% carry Y-chromosomes., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Principles of Inheritance and Variation, 441, Linkage (Exception to Independent Assortment), It is the phenomenon of certain genes staying together during, inheritance through generations without any change or separation., In other words, ‘It is the tendency of genes staying together during, inheritance.’, Morgan (1910) clearly proved and defined linkage on the basis of his, breeding experiments on fruitfly, Drosophila melanogaster., Linked genes are inherited together with the other genes as they are, located on the same chromosome., Linkage group are equal to the number of chromosomes pair present, in cells, e.g., humans have 23 linkage groups., According to Morgan et. al., the linkage can be, (i) Complete or Perfect In this, genes remain together for at, least two generations., (ii) Incomplete or Imperfect In this, genes remain together, within the same chromosome for less than two generations., , Sex-Linked Inheritance, Sex-linked characters are governed by the genes located on sex, chromosomes. The phenomenon of the inheritance of such characters is, known as sex-linked inheritance, e.g., haemophilia, colour blindness,, etc., The sex-linked genes located on X-chromosomes are called X-linked, genes, while these present on Y-chromosomes are called holandric, genes., Few examples of sex-linked inheritance in human beings are given, below, (i) Haemophilia It is a sex-linked recessive disease. It is, transmitted from an unaffected carrier female to some of the, male progeny. In this disease, a protein involved in the clotting, of blood is affected due to which a small cut results in profuse, bleeding and sometimes may lead to death., A heterozygous female (carrier) for haemophilia may transmit, the disease to sons (50% chances), if she marries a normal male., The possibility of female becoming haemophilic is extremely, rare because mother of such a female has to be at least carrier, and the father should be haemophilic., , www.aiimsneetshortnotes.com
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442, , Telegram @neetquestionpaper, , Handbook of Biology, , (ii) Colour blindness It is also a sex-linked recessive disorder. It, is due to defect in either red or green cone of eye resulting in, failure to discriminate between red and green colour. The defect, occurs due to mutation in certain genes present in the, X-chromosomes. The son of a woman who is carrier for the, disease has 50 per cent chance of being colourblind., The carrier mother is not colourblind herself because the gene, is recessive. The daughter will be colourblind only if the mother, is at least carrier and father is colourblind., (iii) Duchenne Muscular Dystrophy (DMD) is also a sex-linked., , Crossing Over/Recombination, Those genes which show non-linkage, result into non-parental, combinations in F1-generation. Presence of such combinations indicates, that in these genes, the process of interchange of alleles within, non-sister chromatids of homologous chromosomes takes place, this is, known as crossing over., The crossing over can be of two types, , Somatic / Mitotic Crossing Over, • Very rare in occurrence., • The crossing over which occurs in, somatic cells of organisms., • First reported by C Stern in, somatic cells of Drosophila., , Single Cross Over, Crossing over at, only one point., , Germinal / Meiotic Crossing Over, • Universal in occurrence., • The crossing over occurs, in germinal cells of organisms, during meiosis., , Double Cross Over, Crossing over at, two points., , Multiple Cross Over, Crossing over at, many points., , The mechanism of crossing over is explained by various theories, some, of them with their propounders are listed below, 1. Copy choice theory — J Lederberg (1955), 2. Precocity theory — C D Darlington (1931), 3. Belling hypothesis — Belling, 4. Break and exchange theory — Stern and Hotta (1969), 5. Hybrid DNA Model — R Holliday (1964), , Linkage Maps/Genetic Maps/Chromosomal Maps, ‘It is the graphic representation of the relative distance between the, genes in a linkage group’., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 443, Principles of Inheritance and Variation, The first linkage map was given by Sturtevant and Morgan in 1920s., In linkage maps, the intergenic distances can be explained through, arbitory unit of measurement called, map unit to describe the, distance between linked genes., 1 map unit =1% of crossing over, One map unit is now referred as cM (centiMorgan) in the honour of, Morgan’s contribution., , Steps to Construct Genetic Map, Step 1 Determination of linkage group and total number of genes, By hybridising wild and mutant strains, we can determine the, total number of genes and link groups in an organism., Step 2 Determination of map distance, For determining map distances, the test crosses are, performed. The relative distance can be calculated according, to the percentage of crossing over, as cross over frequency is, directly proportional to the distance between the genes., Step 3 Determination of gene order, After determining the relative distance, the genes can be, placed in proper linear order., Step 4 Combining map segments, Finally different segments forming linkage group of a, chromosome, are combined to form genetic map., Thus, chromosomal map of chromosome number 2 of Drosophila, melanogaster can be seen as, Red Straight, eyes wings, , Straight Long, wings wings, , Normal, Red, eyes, , Grey, body, , Long, legs, , Long, wings, , Long, aristae, , 5 tarsi, , 104, , 99.2, , 75.5, , 67, , 54.5, , 48.5, , 31, , 13, , 0, , bw, , a, , c, , vg, , pr, , b, , d, , dp, , al, , 4 tarsi, , Brown arc bent, eyes wings, , Curved Vestigial, wings wings, , Purple, eyes, Mutant, , Black, body, , Dachs, (short legs), , Dumpy, Aristaless, wings (short aristae), , The genetic map of chromosome number-2 of Drosophila melanogaster, , www.aiimsneetshortnotes.com
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444, , Telegram @neetquestionpaper, , Handbook of Biology, , Cytoplasmic Inheritance/Extranuclear Inheritance, The total self-replicating hereditary material of cytoplasm is called, plasmon and cytoplasmic units of inheritance are described as plasma, genes., Cytoplasmic inheritance have two distinct features, (i) It is maternal inheritance, i.e., only maternal parent contributes, for inheritance., (ii) The reciprocal crosses are not same due to the participation of, female parents only, e.g., sigma particle inheritance in, Drosophila, Kappa particle inheritance in Paramecium and, breast tumor in mice, etc., In Drosophila, one strain shows more sensitivity towards CO2 (these, are comparatively easily immobilised by exposing them to CO2). This, more sensitivity was discovered by L Heritier and Teissier. The, sensitive trait is regulated by a heat labile substance present in, cytoplasm called sigma., The inheritance of sensitive fly can be seen as, CO2 sensitive female, , ×, , Normal male, , All sensitive flies, Similarly, Normal female, , ×, , CO2 sensitive male, , All normal flies, , Results of reciprocal crosses clearly indicate the inheritance of more, CO2 sensitivity through females. The mammary cancer or breast, tumour in mice has been found to be maternally transmitted. It was, noted by JJ Bitiner. He performed following crosses regarding cancer, in mice, Female, (with breast cancer), , ×, , Male, (without breast cancer), , About 90% offsprings susceptible to cancer, Similarly, Female, (without breast cancer), , ×, , Male, (with breast cancer), , All normal offsprings, , Such a difference in reciprocal crosses suggests the presence of, maternal inheritance., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Principles of Inheritance and Variation, 445, Mutation (Hugo de Vries; 1901), A sudden inheritable discontinuous variation which appears in an, organism due to permanent change in their genotypes., Mutation, Chromosomal mutation/, Chromosomal aberration, , Gene mutation/, Point mutatiion, , Change that occurs in the morphology, of chromosomes, resulting in change of, number or sequence of gene without, change in ploidy., , The sudden stable change in the structure, of a gene due to change in its nucleotide, type or nucleotide sequence is called gene, mutation., , Change in chromosome number, , Change in chromosome structure, , It is called heteroploidy., , The structure of chromosome is, changed because of several reasons., , Monoploidy/Haploidy, , Polyploidy, , (organisms contain only, one set of chromosomes), , (organisms contain several, sets of chromosomes), , Hyperploids, Aneuploidy, , Euploidy, , Allopolyploidy, , (i) Trisomics (2n+1), (ii) Double Trisomics (2n+1+1), (iii) Tetrasomic (2n+2), (iv) Pentasomic (2n+3), , Autopolyploidy, , The polyploids in which the, chromosome sets are, non-homologous and are, derived from two different, species., , The polyploid in which all the, chromosomes are homologous., These are produced by treating, cell with colchicine., , Hypopolyploids, (i) Monosomic (2n –1), (ii) Double monosomic (2n–1–1), (iii) Nullisomic (2n–2), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 446, , Handbook of Biology, , Change in Chromosomal Structure, , G H, , F, , Deletion, , F G H, , A B C E, , It is of two types, 1. Terminal 2. Interstitial, It leads to the loss of genes., A, , B, , C D E, , F, , G H, , A B C B, , F, , C D E, , G H, , Duplication, , The presence of one block of gene more, than once in a haploid complement., A B, , F, , C D E, , G H, , A D C B E, , F, , G H, , Inversion, , A B, , C D E, , F, , G H, , M N O C, , D E, , F, , G H, , Reciprocal, translocation, M N, , O P Q, , R, , A B P Q, , R, , 123, , In this, a section of chromosome, becomes changed after rotation, through 180°., , 321, , Translocation, , C D E, , A B, , Inversion, , Duplicaiton, , Deletion or, Deficiency, , The variations occur due to following four processes, , It is a kind of rearrangement in, which a block of genes from one, chromosome is transferred to other, non-homologous chromosomes., , Diagram showing the forms of chromosomal mutations, , Gene Mutation, The intragenic or point mutations involve alterations in the structure, of gene by altering the structure of DNA. It is of two types, Gene Mutation, , Base pair substitution, In which one nitrogenous, base is substituted by other., , Transitions, In which, the purine, base is replaced by, another purine and, pyrimidine base, is replaced by, another pyrimidine., , Transversions, In which, the purine, base is replaced by, pyrimidine and vice, versa., , Frameshift mutation, The shift in reading frame occurs,, either forward or backward., , Deletion, In this, one or, more nitrogenous, bases are removed, hence, the reading, frame is shifted, towards right., , www.aiimsneetshortnotes.com, , Insertion, Here, the addition, of one or more, nitrogenous bases, takes place and, reading frame is, shifted to left.
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Telegram @neetquestionpaper, Principles of Inheritance and Variation, 447, All these mutations cause various genetic disorders. A list of some, important genetic disorders is given below., Disorder, Sickle-cell, anaemia, , Dominant/ Autosomal/ Sex, Recessive, linked, , Symptom, , Effect, , Recessive, , Autosomal, gene on, chromosome 11, , Aggregation of, Abnormal, erythrocytes, more haemoglobin in, rapid destruction of RBCs., erythrocytes leading, to anaemia., , Phenylketonuria Recessive, , Autosomal, gene on, chromosome 12, , Failure of brain to, develop in infancy,, mental retardation,, idiots, , Cystic Fibrosis, (CF), , Recessive, , Autosomal, gene on Excessive thick, Failure of, chromosome 7, mucus, clogging in chloride ion, lungs, liver and, transport, pancreas, mechanism, anomalies., through cell, membrane., , Huntington’s, Disease (HD), , Dominant, , Autosomal, gene on Gradual, Production of an, chromosome 4, degeneration of, inhibitor of brain, brain tissues in, cell metabolism., middle age, loss of, motor control., , Haemophilia, A/B, , Recessive, , Sex-linked, gene on Failure of blood to Defective form of, X-chromosome, clot., blood clotting, factor VIII/IX, , Colour blindness Recessive, , Sex-linked, gene on Failure to, X-chromosome, discriminate, between red and, green colour., , Down’s, syndrome, , Autosomal,, aneuploidy, (trisomy+21), , Defective form of, enzyme, phenylalanine, hydroxylase., , Defect in either, red or/ and, green cone cells, of retina., , Mongolian eyefold Retarded mental, (epicanthus), open development, IQ, mouth, protruded below 40., tongue, projected, lower lip, many, loops on finger, tips, palm crease, , www.aiimsneetshortnotes.com
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448, , Telegram @neetquestionpaper, , Handbook of Biology, , Disorder, , Dominant/ Autosomal/ Sex, Recessive, linked, , Symptom, , Effect, , Turner’s, syndrome, , Sex chromosome, monosomy 44+X0, , Short stature, Sterile, hearing, females (<5’),, problem, webbed neck,, body hair absent,, menstrual cycle, absent, sparse, pubic hair, under, developed breasts,, narrow lips, puffy, fingers., , Klinefelter’s, syndrome, , Sex chromosomal, aneuploidy, (Tri/tetrasomy of X, chromosome), i.e.,, 44+ XXY,, 44+XXXY, , These males are, Gynaecomastia,, tall with long legs, azoospermia,, testes small, sparse sterile, body hair, Barr body, present, breast, enlargement., , Pedigree Analysis, Scientists have devised another approach, called pedigree analysis, to, study the inheritance of genes in humans. This is also useful while, studying the population when progeny data from several generations is, limited. It is also useful in studying the species with long generation, time. A series of symbols is used to represent different aspects of a, pedigree. These are as follows, Male, Female, Sex unspecified, Affected individuals, Mating, Mating between relatives, (consanguineous mating), Parents above and, children below, (in order of birth-left to right), Parents with male child, affected with disease, , 5, , Five unaffected offsprings, , Symbols used in the human pedigree analysis, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Principles of Inheritance and Variation, 449, Once phenotypic data is collected from several generations and the, pedigree is drawn, careful analysis will allow you to determine, whether the trait is dominant or recessive., For those traits exhibiting dominant gene action, Affected individuals have at least one affected parent., The phenotype generally appears in every generation., Two unaffected parents only have unaffected offspring., l, , l, , l, , It is called dominant pedigree and shown as, I, , II, , III, , Those traits which exhibit recessive gene action, Unaffected parents can have affected offspring., Affected progeny are both male and female and it is called, recessive pedigree and shown as, l, , l, , I, , II, , III, , In due course of time, the genetics and its principles will help in the, solution of several heredity problems., , www.aiimsneetshortnotes.com
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450, , Telegram @neetquestionpaper, , Handbook of Biology, , 28, Molecular Basis, of Inheritance, Early in 20th century, scientists knew that the genes are situated on, chromosomes, but they did not know the composition of genes., The identification of the molecules of inheritance was a major, challenge to biologists., DNA and proteins were the candidate for the genetic material, but, protein seems stronger because of its complexity and variety., The scientists knew that the genetic material should have following, characteristics, (i) It should be able to store information that pertains to the, development, structure and metabolic activities of the cells, or organisms., (ii) It should be stable, so that it can be replicated with high, fidelity during cell division and be transmitted from, generation to generation., (iii) It should be able to undergo rare genetic changes called, mutations that provide the genetic variability required for, evolution to occur., , DNA as Genetic Material, The chromosomes, which are described as hereditary vehicles are the, condensed form of DNA and proteins., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Molecular Basis of Inheritance, 451, The characteristics of DNA as genetic material can be proved through, following experiments, , 1. Bacterial Transformation (Frederick Griffith; 1928), This experiment was performed with two strains of Streptococcus, pneumoniae (the pneumonia causing bacteria)., 1, , 3, , 2, , 4, , +, , Virulent S-III, , Died, Smooth walled, encapsulated (virulent), bacteria, when injected, into mice, it caused, pneumonia and death, of mice., , Non-Virulent, R-II, , Heat Killed, Virulent, , Heat Killed Virulent, +, Living Non-Virulent, , Survived, Survived, When non-virulent, After heat treatment, bacteria were injected the capsular structure, into mouse, it caused got broken down and, no harm to mice, the virulent bacteria, and mice survived., became non-virulent., , Some Died, After mixing both heat killed, virulent and living non-virulent,, the genetic material of virulent,, transformed the rough walled, non-virulents and made them, virulent and responsible for, killing of mice., , S = Smooth walled, R = Rough walled, , Transformation experiment, , www.aiimsneetshortnotes.com
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452, , Telegram @neetquestionpaper, , Handbook of Biology, , 2. Transformation Experiment, (Avery, Mac Leod and Mc Carty; 1944), Through this experiment, they showed that the genetic characteristics, of bacteria could be altered from one type to another by the treatment, with purified DNA., The experiment can be understood by following cases, (Case-1) R-type + Protein S-type = R-Type, (Case-2) R-type + Carbohydrate S-type = R-Type, (Case-3) R-type + DNA of S-type + DNase = R-Type, (Case-4) R-Type + DNA of S-type = R-Type + S-Type, The experiment of Avery, Mac Leod and Mc Carty was based on, the same principle as Griffith’s experiment. R indicates the rough, walled bacteria (i.e., avirulent), while S indicates the smooth walled, bacteria (virulent). In the experiment, in every case the resultant is, modified according to the DNA (i.e., R-type)., , 3. Blender Experiment, (Alfred Hershey and Martha Chase; 1952), The diagrammatic representation of this experiment is given below, Bacteriophage, Radioactive (35S), labelled protein, capsule, , Radioactive (32P) Steps in the Experiment, labelled DNA, 1. Radiolabelling Transfer of, , radioactive 35S to amino acids, in protein coat and 32P to the, DNA molecule. Radiolabelled viruses, can be detected through centrifugation., , 2. Infection When virus and bacteria, come in contact, virus injects its genetic, material into bacteria., 3. Blending This led to the separation of, protein coats from bacteria. Empty coats, called viral ghosts., , Radioactive (32P), detected in cells, +, , Radioactive (35S), detected in supernatant, As no radioactive 35S is, detected in bacterial cell,, it confirmed that protein is, not genetic material., , No Radioactivity, detected in supernatant, Here, radioactive 32P, is detected in bacterial, cell, indicated that only DNA, is entered into cell, which, confirmed the genetic nature, of DNA., , 123, , No Radioactive (35S), detected in cells, +, , 4. Centrifugation After every centrifugation,, the bacterial cell with viral particles from, pellet and viral coat formed the part of, supernatant., Supernatant, contains viral, coats, , Blender experiment of Hershey and Chase, , www.aiimsneetshortnotes.com, , Pellet contains, cells with viral, genetic material
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Telegram @neetquestionpaper, Molecular Basis of Inheritance, 453, DNA, The chromosomes are chemically DNA molecules, which act as the, genetic material in most of the organisms. The DNA was discovered by, a German chemist, F Meischer in 1869. Before discussing the, molecular basis of inheritance in detail, we need to understand the, structure of DNA molecule., 2nm, 5′, , 3′, A T, , Central Axis, The axis at, which whole, DNA strands, revolve around., , T A, , G, C, , C, , G, , T A, G, , 3.4 nm, , Phosphoric Acid, As a component of, nucleotide,it is also, involved in, phosphodiester, linkage., 3rd C atom of first, sugar molecule, , C, , Minor, groove, , CH2, O, C, , T A, G, , Nitrogenous Base, There are two types of bases, –Purine and Pyrimidine. Purines, 5′ include adenine and guanine, while, pyrimidines include thymine and, PO4, cytosine., , O, , C, A T, , 0.34 nm, , T A, , Major, groove, G, C, , G, , C, , –O P = O, Phosphodiester Bond, It is a linkage between two, O, sugars and a phosphoric, C H2, acid is involved in bonding., (–C–O–P–O–C–), O, 5th C atom of second, sugar molecule, , Sugar Phosphate Backbone, OH, Phosphoric acid, i.e., H3PO4 having 3′, 3, reactive, —OH, groups, out, of, which, G C, 2 are involved in forming backbone., The both strands are antiparallel, to each other., Hydrogen Bonds, The nitrogenous bases are held together by, hydrogen bonds. The bonds ultimately held, the strands of DNA. The base G C has, 3 H-bonds, while base A T have two, hydrogen bonds., T A, , Base, , Deoxyribose Sugar, The five carbon sugar,, |, which has — C —H, | no. 2., linkage at carbon, , DNA double helix, , The DNA molecule consists of two helically twisted strands connected, together by base pairs, which align themselves in such a manner just, like the steps of ladder., The antiparallel polynucleotide chains run in opposite directions. The, 5′ end carries phosphate group attached on 5th carbon of sugar and 3′, end carries OH-group attached to 3rd carbon of sugar., , www.aiimsneetshortnotes.com
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454, l, , l, , Telegram @neetquestionpaper, , Handbook of Biology, , The joining of bases creates two types of grooves called major, grooves and minor grooves. Each turn of DNA helix, accommodates 10 base pairs., On the basis of various criteria, there are different types of DNA,, These are given in the following table, Comparative Structure of DNA, Characters, , A, , B, , C, , D, , Z, , Handedness, , Right, , Right, , Right, , Right, , Left, , Base pairs / Turn, , 11.0, , 10.0, , 9.3, , 8.0, , 12.0, , Helix diameter (Å), , 23, , 19, , 19, , 16.7, , 18, , Helix rise per bp, , 2.92, , 3.36, , 3.32, , 3.03, , 3.52-4.13, , Occurrence in, biological world, , Rare, , Common, , Less, common, , No, , In some, cells, , Packaging of DNA Helix, The haploid human genome contains approximately 3 billion base, pairs of DNA packaged into 23 chromosomes. In a diploid cell, it makes, about 6 billion base pairs per cell., As each pair of base is around 0.34 nm long, each diploid cell therefore, contains about 2 metres of DNA [( 0.34 × 10−9 ) × ( 6 × 109 )]., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Molecular Basis of Inheritance, 455, To accommodate such a large amount of DNA in our body the, packaging is required, which can be explained through the following, figure, 1. At the simplest level, chromatin, is a double-stranded helical, structure of DNA., , DNA Double helix, , 2. DNA is complexed, with histones to, form nucleosomes., , 2 nm, 3. Each nucleosome consists, of eight histone proteins around, which the DNA wraps 1.65 times., , Nucleosome core, of eight histone, molecules, , 4. A chromatosome, consists of a nucleosome, plus the H1 histone., , Histone H1, , 11 nm, Chromatosome, 5. The nucleosomes fold up, to produce a 30 nm fibre., , 30 nm, , 300 nm, , 6. These 30 nm fibres, form loops averaging, 300 nm in length., , 300 nm, , 7. The 300 nm fibres are, compressed and folded to, produce a 250 nm wide fibre., , Chromatid, , 700 nm, , 8. Tight coiling of the 250 nm, fibre produces the chromatid, of a chromosome., , Chromosome, , 1400 nm, , Chromosome, , Packaging of DNA at different levels, , DNA Replication, The DNA dependent DNA synthesis (i.e., copying) is called DNA, replication. It occurs in S-phase of cell cycle., In DNA, it was found that replication is of semiconservative type,, although it can be thought of to operate in conservative or dispertive, modes too., , www.aiimsneetshortnotes.com
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456, , Telegram @neetquestionpaper, , Handbook of Biology, , All the three possibilities are given below, , Parental strands, New strands, , Conservative Mode, Semiconservative Mode, Here, out of two daughter, Both DNAs with one old, DNAs, one is completely new, and one new strand., and other one is completely old., , Dispersive Mode, Both DNAs with patches of new, material in older DNA helixes., , Three modes of DNA replication, , The schematic representation of DNA replication in prokaryotes is given below, Parent DNA, Endonuclease creates, nick on one strand of DNA., , Nick, , DNA strand with nick, created at one strand., Opening/unzipping of more nucleotides takes, place by helicase (i.e., DNA unwinding protein)., Replication fork is created in, DNA helix, , Replication fork, , DNA Polymerase III (with its two subunits), joins at each strands., 3′ Leading strands, 5′, , DNA polymerase, , 3′, 3′, , Okazaki fragments, 5′, 3′, , 3′, 5′, , 5′, 3′, , 5′, 3′, , Replication, fork, , 5′ The DNA synthesis on both strands takes, 3′ place, leading strand forms continuous DNA, strand, while lagging strand forms Okazaki, fragments., , DNA ligase, Lagging strand, , Process of DNA replication, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 457, Molecular Basis of Inheritance, As DNA replication can occur only in 5′ → 3′ direction, hence it is, continuous on one strand (leading) and in the form of small fragments,, by forming loop (trombone loop) at another strand (lagging strand)., The DNA synthesis on both the strands can be seen clearly through, following figure, 3′, , 5′ 3′, , Single-Strand, Binding Protein, The protein complex, which maintains the, DNA, single-stranded. It, prevents the recoiling of, DNA., DNA Polymerase, The enzyme DNA, polymerase was, discovered by, Kornberg in 1957., The DNA, polymerase III, catalyses DNA, replication in, prokaryotes., In eukaryotes, it is, done by DNA, polymerase and, DNA, polymerase-α., , Okazaki Fragments, Small 200 bp segments, synthesised by second subunit, of DNA polymerase III at, lagging strand., , 5′, , Template, DNA, , Helicases, The enzyme which unwinds the, double helical DNA for its replication., Primase, The enzyme which synthesises, the primer (RNA) everytime, which is further removed by, DNA polymerase-I, before, DNA-ligase joins these fragments., , 3′, 3′ 5′, 5′, 3′ 5′, , Priming Site, RNA Primers, These are small (10-60 bp) RNA, fragments, synthesised by, primase, act as receptors for, primary nucleotides., , Lagging/Discontinuous Strand, (Trombone Loop), As this strand is already 5′ – 3′,, the parallel synthesis cannot, takes place as DNA replication, always takes place in 5′–3′, direction. Second subunit of DNA, polymerase III synthesises Okazaki, fragments of 200 bp long., , Leading/Continuous Strand, The strand with the direction 3′-5′, on which the, continuous synthesis of new strand takes place, in 5′-3′ direction. The first subunit of DNA, polymerase-III synthesises the DNA., , Mechinery of DNA replication (clearly showing trombone loop), , RNA, The other nucleic acid present in cell is RNA, i.e., ribonucleic acid. It is, present predominantly in cytoplasm and mostly in the form of single, strand. The pyrimidine, thymine of DNA is replaced by uracil in, RNA. All normal RNA chains begin with adenine or guanine., The RNA can be of following three types, (i) mRNA or messenger RNA or template RNA., (ii) Ribosomal RNA or rRNA., (iii) Soluble RNA or transfer RNA or tRNA., , www.aiimsneetshortnotes.com
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458, , Telegram @neetquestionpaper, , Handbook of Biology, , 1. Messenger or mRNA or Template RNA, It makes 3 − 5% of total cellular RNA. The sedimentation coefficient of, mRNA is 8S. The name messenger RNA was proposed by Jacob and, Monod (1961)., The structural components of mRNA include, (i) CAP (at 5′ end), (ii) Non-coding region-1, (iii) Initiation codon (AUG), (iv) Coding region, (v) Termination codon, (vi) Non-coding region - 2, (vii) Poly A sequence (at 3′ end), AUG, (Initiation codon), , UAA or UAG or UGA, (Termination codon), , 5′, , 3′, Cap, , NC 1, (10-100), nucleotides, , Coding, region, 1600 nucleotides, , NC 2, (50-150), nucleotides, , Poly (A) sequence, (200-250 nucleotides), , Structure of mRNA, , The mRNA formed in nucleus, comes out with proteins into cytoplasm, and normally swims as spherical balls, known as informosomes., , 2. Ribosomal RNA or rRNA, It makes about 80% or more of total cellular RNA. It is the basic, constituent of ribosomes and developed from the Nucleolar Organiser, Region (NOR) of chromosomes in eukaryotes. In prokaryotes, it is, developed from rDNA., Unpaired, bases, Paired bases, Coiled, region, , Uncoiled, region, , Structure of ribosomal RNA (schematic), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 459, Molecular Basis of Inheritance, There are three types of rRNA present, (i) High molecular weight rRNA (mol. wt > 1 million), e.g., 21S – 29 S rRNA., (ii) High molecular weight rRNA (mol. wt < 1 million), e.g., 12 S – 18 S rRNA., (iii) Low molecular weight rRNA (mol. wt ~ 40,000), e.g., 5S rRNA., , 3. Transfer or tRNA or Soluble RNA, It makes about 10 – 20% of total cellular RNA with sedimentation, coefficient of 3.8 S. It contains 73 – 93 nucleotides., tRNA is synthesised in nucleus on DNA template. About 0.25% of DNA, codes for tRNA. The chief function of tRNA is to carry amino acids to, ribosomes for protein synthesis., Amino, acid, , Amino acid, binding site, , 5′, , TψC loop, , ACC, , Synthetase site, , 3′, , CCA terminus, , DHU loop, , Ribosome, recognition site, , Anticodon loop, , Anticodon site, (a), , (b), , tRNA (a) The binding sites (b) The tertiary structure, , Gene Expression, It is the process by which information contained in genes is decoded to, produce other molecules that determine the phenotypic traits of, organisms., , Central Dogma, Central dogma of molecular biology states that there is one way or, unidirectional flow of information from master copy DNA to working, , www.aiimsneetshortnotes.com
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460, , Telegram @neetquestionpaper, , Handbook of Biology, , copy RNA (transcription) and from working copy RNA to building plan, polypeptide (translation)., Transcription, Translation, DNA , → mRNA , → Polypeptide, , Central dogma of molecular biology was proposed by Crick (1958). It is, also written as follows, Replication, , Transcription, , Translation, DNA → DNA → mRNA , → Polypeptide, , In this dogma, genetic information is stored in the 4 letters language of, DNA and same is transferred during transcription to 4 letters, language of messenger., Commoner (1968) suggested a circular flow of information., DNA → RNA → Proteins → RNA → DNA, DNA, RNA, , RNA, Protein, , Temin (1970) found that retroviruses perform Central Dogma, reverse that involves reverse transcription (forming DNA from RNA)., DNA, , Transcription, Reverse Transcription, , RNA, , Translation, , Polypeptide, , Transcription or RNA synthesis occurs over DNA. Translation or, protein synthesis occurs over ribosomes. These two are separate in, time and space. This protects DNA from respiratory enzymes and, RNAs from nucleases., , Transcription, The transfer of information from DNA strand to RNA is termed as, transcription. It occurs in the nucleus during G1 and G2-phases of cell, cycle., Like DNA replication, it also proceeds in 5' → 3' direction and it, requires the enzyme RNA polymerase. In prokaryotes, only one RNA, polymerase is involved in transcription (with its 5 polypeptide subunits, – σ , β, β' and 2α), while in eukaryotes, the transcription is performed by, three RNA polymerases, (i) RNA polymerase-I Synthesises large rRNAs., (ii) RNA polymerase-II Synthesises small rRNA and mRNA., (iii) RNA polymerase-III Synthesises small rRNA and tRNA., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Molecular Basis of Inheritance, 461, Transcription Unit, The segment of DNA that takes part in transcription is called, transcription unit. It has three components, 1. A promoter, 2. The structural gene, 3. A terminator, A schematic the representation of the process of transcription is as, follows, Core enzyme, Sigma factor, , RNA polymerase, , 1. Binding of RNA polymerase with its, sigma factor to DNA strand., , DNA, Start, , one gene, RNA polymerase, , Initiation site, Core enzyme, , Sigma, factor, , mRNA, , RNA chain, growth, , (r) Rho factor, , End, 2. RNA polymerase reaches to initiation site from, where the process of transcription starts., 3. Initiation After uncoiling of DNA strands, a, bubble shaped structure called transcription, bubble is formed and the synthesis of RNA, chain starts., 4. Elongation Further addition of ribonucleotides, leads to elongation of RNA chain., , Termination, site, 5. Termination The termination factor (ρ=Rho), stops the chain growth and releases RNA from, transcription bubble. The DNA recoils and, newly synthesised RNA goes for processing., , Outline of transcription process, , RNA Processing, In Prokaryotes, In prokaryotes, there are three enzymes, RNase III, RNAse E and, RNase P which are responsible for the most of primary, endonucleolytic RNA processing events. The first two are proteins,, while RNAse P is a ribozyme., These enzymes have unique functions and in their absence the, processing events are not performed. On the other hand, a large, exonuclease participates in the trimming of the 3’ end of tRNA, precursor molecule., , In Eukaryotes, The initial processing steps involve the addition of a cap at 5′ end and, a tail at 3′ end. The primarily synthesised RNA (i.e., Pre mRNAs),, constitute the group of molecules found only in nucleus,, i.e., heterogenous nuclear RNA (hnRNA). These RNA molecules, in, combination with proteins form heterogenous nuclear ribonucleoprotein, particles (hnRNPs). In general, any RNA having sedimentation, coefficient more than 8 is called hnRNA., , www.aiimsneetshortnotes.com
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462, , Telegram @neetquestionpaper, , Handbook of Biology, , Capping involves the formation of a cap at 5′ end by the, condensation of guanylate residues. Addition of tail at 3′ end occurs, in the form of adding polyadenylate sequences., , Genetic Code, The genetic code was discovered by Nirenberg and Matthaei (1961)., The 64 distinct triplets determine the sequence of 20 amino acids on, polypeptide chains., It is defined as, ‘The nucleotide sequence of nitrogenous bases, which specifies the, amino acid sequence in a polypeptide molecule’., , Features of Genetic Code, Universal, With only some minor, exceptions a single coding, dictionary is used for almost, all organisms., Linear, The genetic code is, written in linear form,, in which ribonucleotide, acts as letters., , Commaless, The codons on mRNA, are not spaced by, any comma. Once the, translation begins the, codons are read, continuously one, after other., , Triplet, , Non-overlapping, , Genetic Code, , It means any single, ribonucleotide at a, specific location in, mRNA is the part of, only one triplet., , Degenerate, Any amino acid can be, specified by more than, one codons., , Each codon consists of, three letters. Thus, each amino, acid is specified by three, nitrogenous bases in DNA / RNA., , Non-ambiguous, A particular codon always, codes for the same amino acids., This ambiguity is enhanced at, high Mg+ ion concentration,, low temperature, etc., , Characteristics of genetic codes, , As a result of triplet combination of all ribonucleotides, 64 codons are, generated., Out of these 64 triplet codons, 3 codons are stop or non-sense codon, (or termination codon). These are nucleotide triplets within the mRNA, that signal the termination of translation. These stop codons are, UAG (Amber), UAA (Ochre) and UGA (Opal)., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Molecular Basis of Inheritance, 463, Sometimes genetic codons show deviation from their universality., e.g., in Mycoplasma capricolum, yeast and humans, the stop codon, UGA codes for tryptophan while in several prokaryotes it codes for, amino acid Selenocysteine. In humans, the codon AGA (for arginine), acts as stop codon., Mostly codons are non-ambiguous (i.e., particular codon codes for same, amino acid). However, in certain rare cases, the genetic code is found, to be ambiguous, i.e., some codons, codes for different amino acids, under different conditions, for example, in streptomycin sensistive, strain of E. coli, the codon UUU, normally codes for phenylalanine but,, it may also code for isoleucine, leucine or serine when ribosomes are, treated with streptomycin. This ambiguity is enhanced, at high Mg, ion concentration, low temperature and in the presence of ethyl, alcohol., , Wobble Hypothesis (Crick; 1966), According to this ‘the major degeneracy occurs at the third position,, while first two bases do not change. The third base is called Wobble, base.’ This wobble base of codon lacks specificity and the base in the, first position of anticodon is usually abnormal, e.g., inosine,, pseudouridine and tyrosine., These abnormal bases are able to pair with more than one nitrogenous, bases at the same position, e. g. , Inosine (I) can pair up with A, C and, U. The pairing between unusual bases of tRNA and wobble base of, mRNA is called wobble pairing., , Translation, The process in which genetic information present in mRNA directs the, order of specific amino acids to form a polypeptide chain., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 464, , Handbook of Biology, , The process of translation can be summarised as, Enzyme (aminoacyl t RNA synthetase), Amino, acid, P, , P, , Activation of, Amino acids, , A, , P, , Amino acid + ATP + Enzyme →, Enzyme amino acid – AMP +PPi, , ATP, , P, P, , With the help of enzyme, aminoacyl tRNA synthetase, the, amino acid is activated at its, carboxyl group., , A, , P, , P, P Phosphate, , Amino acid, , Transfer of, amino acid to, tRNA, , P A, AMP, , t RNA, , During this process, a high, energy ester bond is formed, between the carboxyl group, ( COOH) of amino acid and, 3-hydroxy group of terminal, adenosine of tRNA., Enzyme–Amino acid – AMP +, tRNA → Amino acid –tRNA +, AMP + Enzyme., , P A, AMP, , Amino acid– t RNA complex, Transfer of active amino acid to tRNA, , Large, ribosomal, subunit, , Met, , U U, , C G, , U, , C, , U, , A, , C, , A, , U, , G, , G, , U, , C, , U, , U C, , A, , U, , G C, , U, , Smaller, ribosomal, subunit, Joining of larger subunit of, ribosome to smaller subunit-initiation, complex, , Initiation of, polypeptide, chain, synthesis, , The initiation is done by the, formation of smaller subunit, initiation complex by joining of, activated amino acid tRNA, complex with initiation codon., The total complex then joins to, large subunit for complete, synthesis of initiation complex., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Molecular Basis of Inheritance, 465, Amino acid-tRNA, complex, Me, t, , Val, , C, , A, , U, , Phe, , A, , A, , U, , G, , C, , A, , G, , G, , U, , C U, , C, , A, , G, , A, , A, , G, , U, , C, , U, , U, , C, , Ty, r, , Va, l, , Release factors, , Ph, e, Leu, , Ty, , Termination codon (UAG, UGA, and UAA) reaches the ribosome, and terminates the polypeptide, synthesis., , mRNA, , A U G G, , Phe, , U, , Termination of, polypeptide, chain, formation, , G, , Phe, , Val, , C, , The enzyme which helps in, peptide bond formation is, peptidyle transferase. After peptide, bond formation, translocation, occurs, which involves the, movement of second amino acid, tRNA complex from A-site to, P-site., , U C, , Elongating protein, Me, t, , A, , Elongation of, polypeptide, chain, , U, , A, , A, , G, , U, , U, , C, , U, , A, , A, , r, Va, , l, , New protein, , Ph, e, , Leu, , A, , C, , U, , U, , U, , A, , U, , Phe, , G, , C, , U, , A, , A, , Regulation of Gene Expression, Gene regulation is the mechanism of switching off and switching on, of the gene depending upon the requirement of cells and the state of, the development., , (A) Control of Gene Expression in Prokaryotes, The hypothesis of this regulation was given by F Jacob and J Monad., This hypothesis is known as operon model. The theory was given on, the basis of the study of lac (lactose) operon in E. coli., , www.aiimsneetshortnotes.com
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466, , Telegram @neetquestionpaper, , Handbook of Biology, , The operon consists of following components, (i) Regulator gene, (ii) Promoter gene, (iii) Operator gene, (iv) Structural gene, The first three genes among above genes produce three compounds,, i.e., repressor, inducer and corepressor., Repressor has capacity to bind on operator gene only after activation, by corepressor. Another protein inducer have the capacity to bind, on operator as well as repressor., The complete operon looks like, Structural Gene, Regulator, , Promoter, , Operator, , 1200 bp, , 30 bp, , 35 bp, , Regulator is, responsible for the, synthesis of protein, called repressor. The, active repressor is, seen in inducible, system, while inactive, repressor is seen in, repressible system., , It is the segment, at which RNA, polymerase binds., It initiates the, transcription of, structural gene, and controls the, rate of mRNA, synthesis., , This segment of DNA, imposes control over, the transcription. This, region works like ‘on’, and ‘off’ switch for, protein synthesis., , z, , y, , a, , 3063 bp, , 800 bp, , 800 bp, , This region of DNA codes for, the synthesis of proteins. These, determine the primary structure, of polypeptide., , On the basis of their activity principles, the operons are of two types, Operon, Inducible System, (inducer is synthesised by regulator), , Repressible System, (inactive repressor is synthesised by regulator ), , Possibilities, , Possibilities, Inducer, Absent, , Inducer, Present, , In this, regulator gene, produces active repressor,, which binds to operator, gene and blocks, transcription and, protein synthesis., , Regulator gene produces, active repressor, which, forms inducer-repressor, complex. Thus, it does not, bind to operator gene and, transcription and, translation goes on., , Corepressor, Absent, In this, regulator, gene produces, aporepressor, which does not, have affinity for, operator gene., So, it does not, bind to operator, to block the, transcription and, translation., , Corepressor, Present, The aporepressor, produced, combines with, corepressor to, activate it. Then, this, active repressor, binds to operator, gene and blocks, both transcription, and translation., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Molecular Basis of Inheritance, 467, (B) Control of Gene Expression in Eukaryotes, In eukaryotes, the most accepted theory, is Operon-Operator Model, of Britton-Davidson (1969)., According to this model, the eukaryotic operon contains four basic types, of genes, (i) Sensor These gene segments are sensitive to cellular, environment., (ii) Interogator These act as carriers of signal from sensor to, receptor., (iii) Receptor The signal is received by these genes. These are, associated with produce., (iv) Producer These are output control centre., The gene regulation can occur at various levels, 1. At the level of transcription, 2. At the level of RNA processing and splicing, 3. At the level of translation, , Human Genome Project (HGP), HGP was the international collaborative research programme, whose, goal was the complete mapping and understanding of all the genes of, human beings, i.e., genome., HGP has revealed that there are probably about 20,500 human genes., The completed human gene sequence can now identify their locations., The ultimate result of HGP is ‘the detailed information about, structure, organisation and function of the complete set of human, genes.’, The International Human Genome Sequencing Consortium, published the first draft of the human genome in the journal Nature, in February, 2001 with the sequence of the entire genome’s 3 billion, bp, some 90% complete. The full sequence was completed and, published in April, 2003., Following processes were involved in completion of HGP, DNA sequencing, The Employment of Restriction Fragment Length Polymorphism (RFLP), Yeast Artificial Chromosome (YAC), Bacterial Artificial Chromosome (BAC), The Polymerase Chain Reaction (PCR), Electrophoresis, l, , l, , l, , l, , l, , l, , www.aiimsneetshortnotes.com
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468, , Telegram @neetquestionpaper, , Handbook of Biology, , DNA Fingerprinting, It involves the identification of differences in repetitive DNA., Repetitive DNA is a specific region in DNA in which a small stretch of, DNA is repeated many times. It forms the basis of DNA fingerprinting., Technique of DNA fingerprinting w-as initially developed by, Alec Jeffreys to find out markers for inherited diseases., The technique has the following steps, (i) DNA isolation, (ii) Amplification of DNA, (iii) Digestion of DNA, (iv) Separation of DNA fragments, (v) Blotting, (vi) Hybridisation, (vii) Autoradiography, , Applications of DNA Fingerprinting, (i) Used as a tool in forensic investigations., (ii) To settle paternity disputes., (iii) To study evolution., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 29, Evolution, The term evolution is derived from two Latin words, e = from; volvere =, to roll/unfold, and was first used by english philosopher Herbert, Spencer., The principle of evolution implies ‘The development of an entity in, the course of time through a gradual sequence of changes, from a, simple to more complex state’., Biopoiesis refers to origin of life from non-living substances, while, biogenesis is the term used to refer to the origin of life from already, existing life forms., There are two theories which have been given to explain the, mechanism of origin of life. First is spontaneous generation from the, non-living material (abiogenesis) and second is the origin of life from, the parental organism by reproduction (biogenesis). Presently the view, of biochemical origin of life is widely accepted., The history of life comprises two events, (i) Origin of life, (ii) Evolution of life, Before discussing above events in detail we must take a close look on, the ‘origin of universe’., , Origin of Universe, Several theories have been given to explain the origin of universe and, the most accepted one is Big-Bang theory., , Big-Bang Theory (Abbe Lemaitre; 1931), According to this theory, about 15 billion years ago, a fiery explosion, took place in the condensed cosmic matter and its fragments got, scattered into space at an enormous velocity., , www.aiimsneetshortnotes.com
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470, , Telegram @neetquestionpaper, , Handbook of Biology, , Arno Allan Penzias supported the Big-Bang theory and discovered, evidences for this theory. Our galaxy (i.e., cluster of stars) contains, about 100 billion stars and called as Milky way., , Origin of Life, Ancient Theories of Origin of Life, Theories of Abiogenesis, (origin of living organisms from, non-living matter), Theory of Special Creation, These are mythological theories, with, the belief that the life was created by, supernatural powers., Theories of Spontaneous Generation, , Theories of Biogenesis, (origin of living organisms from pre-existing, living organisms, non-living matter), Theories of biogenesis were supported by, various scientists, through experiments, performed by them. Some of them are, discussed here, , This is also known as autobiogenesis., The theory was supported by Plato,, Aristotle, etc. They believed that the, snails, fishes, frogs arose, spontaneously from mud., , Francesco Redi’s Experiment (1668) He, placed well-cooked meat in three jars. First jar, was uncovered, second by parchment and, third was covered by muslin cloth. After, some days, he observed that the maggots, developed only in uncovered jar., , Theory of Cosmozoic Origin According, to this theory, the life is coeternal with, matter without any beginning. The, living protoplasm reached to Earth from, other part of universe., , Lazzaro Spallanzani’s Experiment (1767), Spallanzani, taking organic liquid (boiled, nutritive broth ) in the vessels, then sealed, them. But he always found that, if proper care, is taken, no living things appear., , Louis Pasteur’s Experiment (1860-1862) He, Arrhenius (1908) proposed this theory. disproved the theory of spontaneous, generation by performing a well-designed, It also supports the process of coming, experiment called swan-necked flask, living material from other planet., experiment., Theory of Panspermia, , Modern Theory of Origin of Life (AI Oparin), It is also known as modern theory or abiogenic origin or, naturalistic theory or physicochemical evolution. It was, hypothesised by AI Oparin and supported by JBS Haldane, Miller, and Urey and Sydney F Fox., According to this theory, the life was originated in deep sea, hydrothermal vents. Through these vents, the sea water seeps through, the cracks in bottom, until the water comes close to hot magma., The super heated water expelled forcibly, with variety of compounds, such as H2 S, CH 4, iron and sulphide ions., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Evolution, 471, Oparin wrote the book Origin of Life in 1936. In his book, he, admitted abiogenesis first, but biogenesis ever since. Therefore,, Oparin’s theory is also known as primary abiogenesis., , 34444444444444444244444444444444441, , Chemical Evolution, , The schematic presentation of physicochemical evolution is as follows, Primitive Earth, (Hot revolving ball of the gas) Free atoms like hydrogen, oxygen,, carbon, nitrogen, sulphur, phosphorus, etc., are present., , Inorganic Molecules, These molecules are produced by the combination of elements,, e.g., H2, O2, N2 etc., , Simple Organic Molecules, Formation of water, methane, ammonia and hydrogen, cyanide took place. The environment became reducing., , Complex Organic Molecules, By the polymerisation of simple organic molecules, larger, organic molecules were formed. These are polypeptide,, nucleotides and polysaccharides, etc., , Coacervates, These large organic molecules synthesised abiotically on, primitive earth. These form colloidal aggregates due to, intermolecular attraction. These colloides were called, coacervate by Oparin and microsphere by Sydney F. Fox., , Protobionts, These are also known as protocell or eobiont. These are, nucleoproteinoid having free-living gene and were similar, to present mycoplasma., , Progenotes, The protobionts give rise to Monera, which in turn gives rise, to prokaryotes with naked DNA, protoribosomes, etc., , Algae, , Fungi, , Bacteria, , Bryophytes, Pteridophytes, , Gymnosperms, , Protozoans, Lower invertebrates, , Organic Evolution, , Higher invertebrates, , Vertebrates, , Angiosperms, , www.aiimsneetshortnotes.com
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472, , Telegram @neetquestionpaper, , Handbook of Biology, , Modern theory of origin of life was supported by Miller and Urey with, their experiment in 1953., , Miller and Urey’s Experiment, In 1953, Miller built an apparatus of glass tubes and flasks in the, laboratory. He created an atmosphere containing hydrogen (H2 ),, ammonia (NH3 ), methane (CH4 ) and water vapour (H2 O) in one big, flask and allowed the condensed liquid to accumulate in another small, flask. The ratio of methane, ammonia and hydrogen in the large flask, was 2 : 1 : 2., Energy was supplied to the apparatus by heating the liquid as well, as by electric sparks from tungsten’s electrodes in the gaseous flask, (larger flask). The conditions of apparatus resembled the atmosphere, present on the early earth. The experiment was conducted continuously, for about one week and then the chemical composition of the liquid, inside the apparatus was analysed., The diagrammatic representation of Miller’s experiment is as follows, Tungsten electrodes, (connected to tesla coil), , Spark discharge, , 5-litre flask containing, gaseous mixture, (CH4 + NH3 + H2+ H2O as steam), , To, vacuum pump, Stopcocks for, removing, samples, , Water out, Condenser, Cold water in, Tap for withdrawing, sample, , 500 mL flask, with boiling water, , Aqueous medium containing, organic compounds, , Diagrammatic representation of the apparatus Stanley used to, demonstrate the synthesis of organic compounds by electrical, discharge in a reducing atmosphere., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Evolution, 473, Following categories of products were formed under the prebiotic, conditions in Miller’s experiment apparatus., Some Products Formed Under Prebiotic Conditions, Carboxylic Acids, Formic acid, Acetic acid, Propionic acid, Straight and branched, fatty acids (C 4 − C 10 ), Glycolic acid, Lactic acid, Succinic acid, , Nucleic Acid, Bases, , Amino Acids, , Adenine, Guanine, Xanthine, Hypoxanthine, , Glycine, Alanine, α-amino butyric acid, Valine, , Cytosine, Uracil, , Leucine, Isoleucine, proline, Aspartic acid, serine,, threonine, , Sugars, Straight and branched, pentoses and hexoses, , Which Came First RNA or Protein?, It is a matter of great controversy among biologists to decide that, which came first RNA or protein. There are three views regarding this, problem as follows, (i) RNA world (the group of scientists, who focus on RNA as the, first molecule) RNA world group feels that without a hereditary, molecule, other molecules could not have formed consistently., This view is supported by the discovery of ribozyme, a catalytic, RNA molecule, which have the ability to act like enzymes., (ii) Protein world ( the group of scientists, who focus on protein as, the first molecule) The protein group argues that without, enzymes (which are proteins ), nothing could be replicated at, all, or heritable. They are in view that the nucleotide is very, complex therefore, it cannot be formed spontaneously., (iii) Peptide-Nucleic Acid (PNA) world (the group of scientists,, who focus on the combination of RNA and protein.) The PNA, world believed that there must have been a pre-RNA world,, where the peptide, (nucleic acid) was the basis for life. PNA is, simple and able to self-replicate., , Evidences of Evolution, Scientists proposed many evidences through which the evolution of life, forms can be proved. Several different lines of evidences convinced, Darwin and his contemporary scientists that the modern organisms, arose by evolution from more ancient forms., Darwin documented evolutionary evidences mainly on the basis of, geographical distribution of species and fossil records., , www.aiimsneetshortnotes.com
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474, , Telegram @neetquestionpaper, , Handbook of Biology, , Some significant convincing evidences for the occurrence of descent with, modification come from, 1. Palaeontology, 2. Morphology and comparative anatomy, 3. Geographical distribution, 4. Embryology, 5. Taxonomy, 6. Connecting links, 7. Cytology, 8. Biochemistry and Physiology, 9. Genetics, , 1. Evidences from Palaeontology, Palaeontology is the study of fossils of prehistoric life. According to, Charles Lyell, ‘Fossil is any body or trace of body of animals or plants, buried and preserved by the natural causes.’ Fossils are generally, preserved in sedimentary rocks, which are formed by the deposition, of silt, sand or calcium carbonate over millions of years., , Determination of Age of Fossils, The age of fossils can be determined by following methods, • Radioactive Carbon ( C14 ) Dating Method This was discovered by WF Libby. As, the half life of carbon is relatively short, this isotope is only reliable for dating, fossils less than 70000 years., • Electron Spin Resonance (ESR) Method It is a relatively new, precise and, accurate method. It is based on the fact that the background radiation causes, electron to dislodge from their normal positions in atoms and trapped in, crystalline lattice of material, it is mostly used to date CaCO3 and lime stone., • Radioactive Clock Method This was discovered by Boltwood (1907) and based, , on the disintegrating property of radioactive elements., • Potassium-Argon Method The transformation of potassium into argon; rubidium, , into strontium has been used for dating fossils bearing rocks of any age and any, type., , Geological Time Scale, The evidence of the evolution can also be taken through geological time, scale. The complete lifespan of earth (i.e., 4600 million years) is known, as geological time, which have been divided into eras. Eras are divided, into periods and periods into epochs. An Italian scientist Giovanni, Ardulna, developed first geological time scale in 1760., , www.aiimsneetshortnotes.com
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Caenozoic (Age of Mammals), , Period, , Quarternary, , Tertiary, , Era, , www.aiimsneetshortnotes.com, Zoned climatic belts well, established., , Eocene, , Palaeocene Development of climatic belts., , Lands lower, climate warmer., , Oligocene, , Modernisation of angiosperms., , Extension of angiosperms., , Worldwide tropical forests, rise, of monocots and flowering, plants., , Evolutionary explosion of, mammals., , Placental mammals, diversified, and specialised; hoofed, mammals and carnivores, established., , Archaic mammals extinct,, appearance of modern, mammals., , Mammals at height of evolution,, first man-like apes., , Cooling of climate., , Miocene, , Development of grasses,, reduction of forests., , Decline of forests, great decrease Abundant mammals elephant,, of woody plants., horses and camels, humans, evolving., , Cool and temperate climate, away from equator, continuous, rise of mountains of, Western-North America., , Age of man, extinction of many, large mammals., , Age of man; development of, human cultures., , Pliocene, , Dominance of herbs., Increase of herbs, spread of, herbs and grassland., , End of last ice age; climate, warmer; climatic zones distinct., , Recent, (Holocene), , Fauna, (Animal Life), , Flora, (Plant Life), , Pleistocene Periodic continental glaciers in, North., , Geological and Climatic, Conditions, , Epoch, , Rocky Mountain Revolution (Little Destruction of Fossils), , Geological Time Scale with Notes on Events in the Evolution of Life and Environment, , Telegram @neetquestionpaper, Evolution, 475
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Period, , Epoch, , Geological and Climatic, Conditions, , —, , Triassic, , Continents exposed, world, subtropical climates., , Culmination of worldwide warm, climates., , Birth of modern reptiles,, development of climatic, diversity., , —, , —, , Permian, , Pennsylvanian, , www.aiimsneetshortnotes.com, Uniform climate throughout, world., , Rise of continents; climate, became arid and varied,, glaciation in Southern, hemisphere., , Appalachian Revolution (Some Loss of Fossils), , —, , —, , Jurassic, , Cretaceous, , Rocky Mountain Revolution (Little Destruction of Fossils), , Era, , Mesozoic (Age of Reptiles), , Extinction of ammonites and, trilobites, abundance of, primitives reptiles; appearance of, mammals-like reptiles, decline of, amphibians., , Transaction of reptiles to, mammals, rise of progressive, reptiles and egg laying, mammals, extinction of primitive, amphibians., , Dominance of dinosaurs,, appearance of first toothed birds;, rise of insectivorous marsupials., , Great forests of seed-ferns and, Amphibians dominant on land,, gymnosperms (great tropical coal insects common, appearance of, forests)., first reptiles., , Dwindling of ancient plants,, decline of lycopods and horse, tails., , Gymnosperms dominant,, declining towards the end, extinction of seed fern., , Cycades and conifers common;, appearance of first known, flowering plants., , Dinosaurs become extinct,, toothed birds became extinct;, beginning of toteost fishes and, modern birds; archaic mammals, common., , (Animal Life), , (Plant Life), , Rise of flowiering plants, especially monocotyledons,, decrease of gymnosperms., , Fauna, , Flora, , 476, Handbook of Biology, , Telegram @neetquestionpaper
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—, , Ordovician, , —, , —, , Cambrian, , Archaeozoic, , —, , Silurian, , —, , —, , —, , Mississippian, (Carboniferous), , Devonian, , Epoch, , Period, , Proterozoic, , Era, , www.aiimsneetshortnotes.com, Primitive aquatic plants algae,, fungi and bacteria., , Algae, fungi and bacteria; first, fossils of plant life., , Land plants probably first, appeared, marine algae, abundant., , First known land plants club, mosses, algae dominant., , First forests, first gymnosperms, and first known liverworts,, horsetails and ferns., , Shelled protozoans,, coelenterates, flatworms,, primitive annelids., , Invertebrates numerous and, varied, most modern phyla, established., , First indication of fishes, corals, and trilobites abundant,, diversified molluscs., , Wide expansion of invertebrates,, first insects, rise of fishes., , Diversification in fishes; sharks, and lung fishes abundant,, evolution of amphibians., , Rise of insects, sea lilies at, peak, spread of ancient sharks., , (Animal life), , (Plant life), Mosses and seed ferns, dominant, gymnosperms, increasingly widespread (early, coal forest)., , Fauna, , Flora, , Great volcanic activities, no recognisable fossils, indirect evidence of living things from some, sedimentary deposits of organic material in rocks, e.g., Eubacterium isolatum, Archaeospheroides, barbertonis., , Cool climate, volcanic eruptions,, repeated glaciating., , Climate became progressively, warmer., , Warm climate, great, submergence of land., , Slight climate cooling extensive, continental seas., , Broad distribution of uniform, climates; increased temperature., , Climate uniform, humid at first, cooler later as land rose; spread, of tropical seas., , Geological and Climatic, Conditions, , Telegram @neetquestionpaper, Evolution, 477
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478, , Telegram @neetquestionpaper, , Handbook of Biology, , 2. Evidences from Biogeography, Biogeography is the study of distribution of animals and plants., According to continental drift or plate tectonics theory given by, Alfred L Wegener (1912), the total landmass of modern world is, originated from a large mass called Pangea., This separation was started in carboniferous period and ended till, mesozoic era. The shape of coastal areas and the species of plants, and animals present in different continents supports the theory. The, continental drift theory is also known as Jigsaw fit theory., , 3. Evidences from Morphology and, Comparative Anatomy, These include followings, (i) Homology and Homologous Organs, Those organs which have the same embryonic origin and basic, structure, though they may or may not perform the same function., This is the result of divergence due to adaptive radiation. On the, basis of its occurrence, homology is of following types, Various examples of homologous organs are given with their function in, following diagram, Homology, , Phylogenetic Homology, , Sexual Homology, , Serial Homology, , (Homology between different, species.), e.g., pentadactyl, limbs of air breathing, vertebrates., , (Homology between two, sexes of same species.),, e.g., testes of man and, ovaries of woman., , (Homology exists between, two organs of same individual),, e.g., arm and leg of man., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Evolution, 479, Flying, , Swimming, , Running, , Carpals, Humerus Humerus Radius, and ulna, , Grasping, , Humerus, , Humerus, , Carpals, , Ulna, , Radius and ulna, , Ulna, , Radius, Radius, Phalanges, , Phalanges, , Pterodactyl, Carpals, , Ulna Radius, , Carpals, , Dolphin, , Carpals, , Humerus, , Metacarpals, Phalanges, , Dog, Phalanges, , Humerus, , Humerus, , Human, Radius, Humerus, , Ulna, , Bird, Phalanges, , Carpal, Radius, and ulna, , Carpals, Humerus, , Radius, Carpals, , Cannon, bone, , Ulna, , Phalanges, , Phalanges, , Phalanges, Skin patagium, , Seal, , Horse, , Shrew, , Bat, , Homology of forelimbs in vertebrates, , Adaptive Radiation, HF Osborn (1898) developed the concept of adaptive radiation or, divergent evolution, i.e., the development of different functional, structures from a common ancestral form., The significance of adaptive radiation is that, it leads to the, modification of homologous structures which ultimately results into, divergent evolution., , www.aiimsneetshortnotes.com
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480, , Telegram @neetquestionpaper, , Handbook of Biology, , Following figure of adaptive radiation in Darwin’s finches clearly, indicates the process of divergent evolution, Finches from the mainland, of South America that, colonised the, Galapagos Islands, , Galapago’s, finches, , Large, (ground finch), , Insectivorous, (warber finch), , Vegetarian, (tree finch), , Woodpecker, (tool using finch), , Insectivorous, (tree finch), , Cactus (ground, finch), , Food sources, , Large, seeds, , Cactus, seeds and, nectar, , Flying, Insects, , Large, insects, , Buds and, fruits, , insect, larvae, , Adaptive radiation in Darwin’s finches, , (ii) Analogy or Analogous Organs, These are the structures which are different in their basic structure, and developmental origin, but appear and perform similar functions., This relationship between structure and function is known as analogy, or convergent evolution., , Adaptive Convergence (Convergent Evolution), In adaptive convergence, separate lineages show similar morphology, under the influence of similar environmental factors., ‘When a species of distinct lineages closely resemble on overall, morphology it is called as homeomorphs’, e.g., wings of birds, insects, and bats are homeomorphs., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Evolution, 481, Analogy in the wings is shown in the following diagram, Forewing, , Hind wing, , Dragon fly, , Phalanges, , 2, 1, , 3, , 4, , 5, , Feathers, , Phalanges, Carpals Metacarpals, Carpals, Membrane, Radius, of wing, and ulna, Radius, Humerus, and ulna, , Humerus, Pterodon, , Eagle, , Phalanges, Metacarpals, Carpals, Radius, and ulna, (fused), , Skin, Patagium, , Humerus, Bat, , Analogy in the wings, , (iii) Vestigial Organs, These are non-functional organs, which were functional in their, ancestors., There are more than 90 vestigial organs in the human body. Some, examples are coccyx (tailbone), nictitating membrane (3rd eyelid),, caecum, vermiform appendix, canines, wisdom teeth, body hair,, auricular muscles, mammary glands in males, etc., Vestigial organs are also present in some other animals, e.g., splint, bones in horse, hindlimbs and pelvic girdle in python, wings and, feathers in flightless birds, etc., Atavism or Reversion, It is the sudden reappearance or refunctioning of some ancestral, organs, which have either completely disappeared or are present as, vestigial organ, e.g.,, Long and dense hair, Birth of human baby with small tail., Development of power of moving pinna in some individuals., l, , l, , l, , 4. Evidences from Embryology, Through the comparative study of life histories of individuals, the, evidences of evolution can be collected., A comparative study of the ontogeny of various forms of animals, reveals the phylogenetic relationship and thus confirms evolution. To, varify this, following points can be considered, (i) The zygote of all metazoans are single-celled and similar to the, body of protozoans., (ii) The stages of embryonic development, i. e. , morula, blastula, and gastrula are basically similar in all metazoans., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 482, , Handbook of Biology, , (iii) In fishes, the young individuals develop from gastrulas is almost, like the adult, but the tadpole of amphibians is similar to young, fishes., (iv) The early postgastrula stages are quite similar in the members, of all the different classes viz-fishes, amphibians, reptiles,, birds and mammals., (v) Possession of pharyngeal gill slits and gill pouches are one, of the three diagnostic characters of all chordates., Due to the similarity among early embryos of all vertebrates, it is very, difficult to differentiate a human embryo from embryo of other, vertebrates., The comparative account of several vertebrate embryos is given as, follows, In early, gestation, period, I, , I, , I, , I, , I, , I, , In mid, gestation, period, II, , II, , II, , II, , II, , II, , In late, gestation, period, III, III, III, III, Fish Salamander Tortoise Chick, , III, III, Rabbit Man, , Depicting the remarkable similarity in the early embryos of some, vertebrates, , Recapitulation Theory or Biogenetic Law, It states that Ontology recapitulates phylogeny, i.e., ontogeny, (development of the embryo) is the recapitulation of phylogeny (the, ancestral sequences)., , www.aiimsneetshortnotes.com
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484, , Telegram @neetquestionpaper, , Handbook of Biology, , 6. Evidences from Taxonomy, During classification, organisms are grouped according to their, resemblance and placed from simple organisms towards the, complexity., There was no difference among animals and plants during the origin of, unicellular stage of organisms. Thus, Euglena is a common ancestor of, both plants and animals., , 7. Other Evidences, Several other evidences also support the process of evolution. These, may by of biochemical or physiological (i.e., study of different, products and physiology among organisms), cytological (i.e., deep, observation of cellular composition among related organisms) and, genetical (i.e., have the mutation and variation as their theme for, evolution) nature., , Theories of Evolution, Organic evolution implies that ‘present day organisms are modified,, but lineal descendents of species that lived in former geological time,, and the more complex and highly differentiated forms have evolved, from the simpler organisms by gradual modifications’., , Lamarckism, It is the first theory of evolution which was proposed by Jean, Baptiste de Lamarck (1744-1829), a French biologist., It was published in 1809 in his book ‘Philosophie Zoologique’., Central Idea The characteristics that are acquired by organisms, during their lifetimes in response to environmental conditions are, passed on to their offsprings., Four Basic Propositions of Lamarck, Lamarckism includes four basic propositions, (i) Internal vital force, (ii) Effect of environment and new needs., (iii) Use and disuse of organs., (iv) Inheritance of acquired characters., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Evolution, 485, The diagrammatic representation of Lamarck’s theory is as follows, The ancestors of giraffe were bearing small neck and, forelimbs and were like horses. These have internal vital, force to increase their size and become relatively large in, due course of time., , Probably, due to some reasons, the surface vegetation, was removed which lead to the stretching of neck to, reach to the branches of trees. This stretching is induced, by the scarcity of food in environment and need for the, food. The changing environmental conditions always, generate new needs. To fulfil new needs, an organism, needs to make some changes in their structure., As the neck is comprehensively used to reach to the, branches of trees, the elongation takes place. This is, based on the proposition of use and disuse of organs the, other organs of body say tail is not used so much hence,, reduced or become unchanged. The continuous stretching, of neck led to permanent elongation and character is, acquired., The acquired character (i.e., long neck) is transmitted in, next generation as the inheritance of acquired character, is given by Lamarck. After several generations, the, variations/modifications are accumulated upto such extent, that they give rise to new species. This process of new, species formation is called speciation., , Criticism of Lamarckism, (Evidences against the inheritance of acquired characters), Mendel’s laws of inheritance and Weismann’s theory of, continuity of germplasm (1892) discarded the Lamarck’s concept of, inheritance of acquired characters., Theory of continuity of germplasm (August Weismann, 1834-1914), According to Weismann, ‘the characters influencing the germ cells are, only inherited’., , www.aiimsneetshortnotes.com
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486, , Telegram @neetquestionpaper, , Handbook of Biology, , There is a continuity of germplasm (protoplasm of germ cells),, but the somatoplasm (protoplasm of somatic cells) is not, transmitted to the next generation. He cut the tails of rats for as, many as 22 generations and allowed them to breed, but tail-less mice, were never born., , Neo-Lamarckism, In full agreement with Weismann’s theory, neo-Lamarckism proposes, that, (i) Environment influences an organism and changes its heredity., (ii) Some of the acquired variations can be passed on to the, offspring., (iii) Internal vital force and appetency (i.e., a desire) do not play, any role in evolution., (iv) Only those variations are passed on to next generation, which, also affect germ cells., , Darwinism (Charles Robert Darwin; 1809-1882), The second most famous theory of evolution was given by Charles, Robert Darwin. It was published in 1859 in his book ‘‘Origin of, Species by Means of Natural Selection” or the Preservation of, Favoured Races in the Struggle for Life’’., Five Basic Propositions of Darwinism, Darwinism includes five basic propositions, (i) Rapid multiplication/overproduction, (ii) Limited resources, (iii) Variations, (iv) Natural selection, (v) New species formation, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Evolution, 487, The diagrammatic presentation of five propositions are given in, following figure, The multiplication of individual of a species occurs in a, geometric proportion. Due to this tendency of multiplication,, in a very short time the earth would be overcrowded., Despite having the rapid rate of reproduction by a species,, its number remains about constant under fairly stable, environment., , Due to this geometric population growth and their demands,, the resources got depleted rapidly and lead to deficiency. As, most of the natural resources are limited, it led to the, adjustment among organisms for their needs. The struggle, for resources occurs at three levels, 1. Intraspecific struggle Struggle among individuals of, same species. It is most intense., 2. Interspecific struggle Struggle between the individuals, of two different species., 3. Struggle with environment It is the struggle of living, forms against the environment., Variations are the differences among the individuals. These, variations can help to adjust with the environment., There are two types of variations, 1. Continuous variation It shows the whole range of, variation among particular character., 2. Discontinuous variation These appear suddenly and, show no gradation., Variations can be conclusively termed as environment, induced adaptation by an individual., The organisms which adapt useful variation successfully, survive in changing environment and those which fail to, put those changes are not selected and stunted or removed, from the population after death. This process is termed as, natural selection by Darwin. The giraffes with small neck, failed to survive and died. The phrase survival of the fittest, was given by Herbert Spencer., The survived population radiated in different environment, and established as different species with changed/modified, characters. This process of establishment of new species is, called as speciation by Darwin. The new species is, originated by combination of struggle for existence,, continuous variation and inheritance., , www.aiimsneetshortnotes.com
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488, , Telegram @neetquestionpaper, , Handbook of Biology, , Criticism of Darwin’s Natural Selection Theory, Following are the criticisms against Darwin’s theory, (i) Darwin emphasised on inheritance of small variations, which are non-inheritable and useless for evolution., (ii) Darwin failed to explain the survival of the fittest., (iii) Darwin failed to differentiate between somatic and germinal, variations., (iv) Natural selection does not explain the coordinated, development and coadaptation., (v) Darwin failed to explain the occurrence of vestigial organs., , Neo-Darwinism, It may be defined as the theory of organic evolution by the natural, selection of inherited characteristics., The theory of evolution given by Darwin and Wallace has been, modified in the light of modern studies like genetics, molecular biology,, palaeontology and ecology, etc., Postulates of Neo-Darwinism, These are as follows, (i) Neo-Darwinism distinguished between the germplasm and, somatoplasm., (ii) Neo-Darwinism explained that the adaptations result from the, multiple forces and natural selection is one of them., (iii) As per Darwinism, characters are not inherited as such, instead, there are character determiners which control the development., (iv) The characters are the result of determiner’s (genes) of, organisms and the environment during its development., , Mutation Theory (Hugo de Vries, 1848-1935), To explain the process of evolution, Hugo de Vries proposed mutation, theory, which was published in 1901 in his book ‘Die Mutation, Theorie’., He gave much importance to the discontinuous variations or, saltatory variations. He coined the term mutation for suddenly, appearing saltatory variations., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Evolution, 489, Main Features of Mutation Theory, As the mutation theory is more emphasised on mutation’s features, it, can be diagrammaticaly represented as, Random, Beneficial or Harmful, Mutation can occur in any direction., It is harmful or useful. Harmful mutations, are eliminated, while useful one is, naturally selected., , Heritable and Naturally Selected, , Raw Material, Mutation is raw material and, basic requirement of evolution., , Mutation, , Medium of Speciation, Sometimes mutations are the, cause of new species formation, , Mutations are the changes which, inherit from one generation to next, and are the basis of natural selection., , Large and Comprehensive, Mutations are not small changes,, but they are large and help, in changing the organism’s, physiology comprehensively., , Criticism Against Mutation Theory, (i) The Oenothera lamarckiana of Hugo De Vries was not a, normal plant, but a complex heterozygous form with, chromosome aberrations., (ii) Natural mutations are not the common phenomenon., (iii) Most mutations are recessive and retrogressive., (iv) Mutation theory fails to explain the role of nature in the process, of evolution., , Modern Synthetic Theory of Evolution, The modern theory of origin of species or evolution is known as, modern synthetic theory of evolution., The modern synthetic theory of evolution evolved in 1937, with the, publication of Dobzhansky’s Genetics and the Origin of Species, which was supported by Huxley (1942), Mayr (1942) and Stebbins, (1950), etc., , www.aiimsneetshortnotes.com
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490, , Telegram @neetquestionpaper, , Handbook of Biology, , Main Postulates of Modern Synthetic Theory of Evolution, This theory has four basic types of processes, this can be represented, diagrammatically as following, These are the mutations at gene, level, in which one or more base, pairs get changed., , an, ce, Ch, , Hybridisation, , Change in Chromosomes, Structure and Number, , ation, Migr, , Natural selection is the, cause which guides the, population for selective, adaptation., , Natural Selection, , Gene Mutation, , The mutation occurs at, chromosomal level. It, is also called as, chromosomal, aberrations. The, chromosomal, fragments exchanged, or are lost in this, exchange., , Genetic Recombination, Genetic recombination provides, genetic variability, without which, change cannot take place., , Causes and processes of evolution (causes with bold and processes in boxes), , Mechanism of Evolution, Evolution is a change in a populations alleles and genotype from, generation to generation. There are four basic mechanisms by which, evolution takes place. These include mutation, migration, genetic, drift and natural selection., Agents of evolutionary change Various agents of evolutionary, changes are as follows, , Mutation, It is sudden and heritable change in an organism, which is, generally due to change in the base sequence of nucleic acid in the, genome of the organisms. It is the ultimate source of variations., Mutation may be harmful or beneficial for the organism. It helps in the, accumulation of variations, which later results in large variations and, new species formation., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Evolution, 491, Gene Migration (Gene Flow), The movement of individuals from one place to another is called, migration. It can be a powerful agent of change because the, members of two different populations may exchange genetic material., Sometimes gene flow is obvious when an animal moves from one, place to another. When a newcomer individual have unique gene, combination and is well-adapted, it alters the genetic composition of, receiving population., , Genetic Drift or Random Drift, In small population, frequencies of particular allele may change, drastically by chance alone. Such change in allele frequencies occurs, randomly as if the frequencies were drifting and are thus known as, genetic drift. It continues until genetic combination is fixed and, another is completely eliminated., There are two special cases of genetic drift, 1. Founder effect/founder principle It is noted that when a, small group of people called founders, leave their place of origin, and find new settlements, the population in the new settlement, may have unique genotypic frequency from that of the parent, population. Formation of a different genotype in new settlement, is called founder effect., 2. Bottleneck effect Due to several natural causes, the, population declines even if the organisms do not move from one, place to another. A few surviving individuals may constitute a, random genetic sample of the original population. The resultant, alterations and loss of genetic variability has been termed as, bottleneck effect., , Parent, Population, (more white, individuals as, compared to, the black ones), , Bottleneck, (drastic reduction, in population), , Note that the, surviving, individuals have, more amount of, black balls., , Next generation, with larger, proportion of, black individuals, in comparison to, white individuals., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 492, , Handbook of Biology, , Selection, Darwin and Wallace explained the differential reproduction as the, result of selection. It is of two types, , 1. Artificial selection, In this, the breeder selects for the desired characteristics., , 2. Natural selection, Environmental conditions determine that which individual, population produces the maximum number of offspring., , in, , On the basis of environmental conditions, natural selection can be, categorised as follows, Direction of, natural force, , Natural Selection, , Population, , Trait value, Generation-1, , This occurs, when environmental, change may produce selection, pressure, , Trait value, Generation-1, , Direction of growth, of population, Proportion of, individuals, , Proportion of, individuals, , Disruptive or Diverging, Selection, , Proportion of, individuals, , In this, the selective pressure, for the species to change in, one direction., , Proportion of, individuals, , Proportion of, individuals, , This occurs when environment, does not change and it causes no, pressure on well-adapted ones., , Directional Selection, , Trait value, Generation-2, , Direction of growth, of population, , Trait value, Generation-2, , Trait value, Generation-1, Direction of growth, of population, Proportion of, individuals, , Stabilising or, Normalising Selection, , Declining, individuals, Trait value, Generation-2, , Hardy-Weinberg Law, It is the fundamental law which provides the basis for studying the, Mendelian populations. It was developed by GH Hardy and, G Weinberg in 1908. It states that ‘The gene and genotypic, frequencies in Mendelian population remain constant, generation after, generation, if there is no selection, migration, mutation and random, drift takes place.’, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Evolution, 493, Followings are the conditions for Hardy-Weinberg equilibrium., No Mutation, , No Genetic Drift, , Allelic changes do not occur,, or changes in one direction, are balanced by changes, in the opposite direction., , The population is very large, and changes in allelic, frequencies due to chance, alone are insignificant., , Conditions, for, Hardy-Weinberg, Equilibrium, , No Selection, , No Gene Flow, Migration of individuals, and therefore, alleles, into or out of the, population does not occur., , No selective force, favours one genotype, or another., , Random Mating, Individuals pair by chance,, not according to their, genotypes or phenotypes., , Hardy-Weinberg principle is a tool to determine when evolution is, occurring. To estimate the frequency of alleles in a population, we can, use the Hardy-Weinberg equation., According to this equation,, p = the frequency of the dominant allele (represented here by A), q = the frequency of the recessive allele (represented here by a), For a population in genetic equilibrium,, p + q = 1.0 (The sum of the frequencies of both alleles is 100%), ( p + q )2 = 1, So,, , p2 + 2 pq + q 2 = 1, , The three terms of this binomial expansion indicate the frequencies of, the three genotypes, p2 = frequency of AA (homozygous dominant), 2 pq = frequency of Aa (heterozygous), q 2 = frequency of aa (homozygous recessive), , Evolution of Human, Human beings belong to a single family–Hominidae,which includes a, single genus Homo which have a single living species sapiens and a, single living subspecies sapiens. All the racial groups Mongoloid,, Negroid, Caucasoid and Australoid are the types of Homo sapiens, sapiens., , www.aiimsneetshortnotes.com
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494, , Telegram @neetquestionpaper, , Handbook of Biology, , The detailed classification of human with their general characteristics, are mentioned in following table, Classification of Human, Kingdom, , Animalia, , Absence of chlorophyll, cell wall, presence of, locomotion and intake of complex food., , Phylum, , Chordata, , Presence of notochord and dorsal hollow central, nervous system., , Sub-phylum, , Vertebrata, (Craniata), , Presence of vertebral column and cranium, (brain box)., , Section, , Gnathostomata, , Jaws are present., , Super-class, , Tetrapoda, , Forelimbs are present., , Class, , Mammalia, , Mammary glands, ear pinna and hair are present., , Sub-class, , Theria, , Viviparous., , Infraclass, , Eutheria, , Presence of true placenta., , Order, , Primata, , Presence of nails over the digits., , Sub-order, , Anthropoidea, , Facial muscles are present for the emotional expression., , Family, , Hominidae, , Posture is erect and bipedal locomotion., , Genus, , Homo, , Man, , Species, , sapiens, , Wise, , Sub-species, , sapiens, , Most wise, , Human and Other Primates, The primates originated in the beginning of the tertiary period, (Palaeocene epoch) about 65 million years ago from a small terrestrial, shrew-like insectivore., The beginning of primate evolution is presumed in Eocene of Tertiary, period (75-60 million years ago) in evergreen forests. The place of, origin of human is great controversy., The fossils of humans were obtained from Africa, Asia and Europe, but, most probably the origin of human occurred in Central Asia, China,, Java and India (Shivalik hills)., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Evolution, 495, Epochs age, in Million, years, , Neanderthal, Homo erectus man, Homo habilis, A. robustus, Australopithecus, A. boisei, , Pleistocene, 2.5, , Holocene (Recent), 0.001, , New world, Chimpan, Homo sapiens, monkey, Gibbon, zee, Old world, Orangutan, Gorilla, monkey, Cro-Magnon Man, , Pliocene, 7, , Australopithecus, Ramapithecus, Ramapithecus, , Miocene, 25, Oligocene, 38, , ERA, , Palaeocene, 65, , Eocene, 54, , Tertiary, , Coenozoic ERA (ERA or Modern Life), , Quarternary, , Periods, , Following primate trees throw a light on human evolution, , Dryopithecus, , Parapithecus, Lemurs and Tarsiers, Tree shrews, Tree shrews, , Human evolution can be explained through the series of following, intermediates of early humans. From the earliest ape-like ancestors to, the modern man, the evolution is slow and dynamic process., The common ancestry of both ape and human got differentiated after, Dryopithecus and the first man-like primate was Ramapithecus, it was, the oldest man’s ancestor and the first hominoid., Australopithecus, constitutes the first ape man, which had both man, and ape characters. Australopithecus gave rise to Homo habilis, approximately 2 million years ago., , www.aiimsneetshortnotes.com
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496, , Telegram @neetquestionpaper, , Handbook of Biology, , Prior to ape man, Homo habilis (handy man, or able man or skillful man, or the tool maker), , Discovery, Mary Leakey (1961) obtained the fossils of Homo, habilis from Pleistocene rocks of Olduvi Gorge in, East Africa., Richard Leakey (1972) also obtained fossils of, Homo habilis from East side of Lake Turkana in, Kenya, Characteristics, Homo habilis man was about 1.2 to 1.5m tall., Its cranial capacity was 700-800 cc, which lived in, Africa about two million years ago., Homo habilis was carnivorous and had begun, hunting for meat., Homo habilis lived in small community or groups in, caves., Perhaps they showed sexual division of labour and, communicated with visual signals and simple, audible sounds., l, , l, , l, , l, , l, , l, , l, , Homo erectus (erect man), , Discovery, Fossils of Homo erectus obtained from diverse sites, from Olduvai Gorge in Africa to Java, Algeria,, Germany, Hungary and China., Fossils were 8,00,000 to 30,000 years ago., Homo erectus is considered as the direct ancestor of, modern man. It evolved from H. habilis about 1.7, million years ago in the Pleistocene., Homo erectus species includes the fossils of Java, man, Peking man, Heidelberg man, Algerian of, Atlantic man., l, , l, , l, , l, , Characteristics, They were the oldest known early human to have, modern human-like body proportion., They were the first human species to have fleshy, nose. They had flat skull with prominent ridges over, the brow., They had short arm and long legs. The short arms, depict that the tree climbing ability was lost, completely in them. The long legs depict that they, are better suited for long distance migrations., They were the first one to walk upright and stood, erect thus, named so. Also, known as Homo, ergaster., They were the first hominid to live in hunter-gatherer, society., l, , l, , l, , l, , l, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Evolution, 497, Java man or, Pithecanthropus erectus or, Homo erectus (ape man, that walks erect), , Discovery, In 1891, Eugene Dubois obtained fossils (some, teeth, skull cap and femur bone) from Pleistocene, deposits (500000-1500000 years back) in Central, Java (an island of Indonesia)., It was named Pithecanthropus erectus (ape man, that can walk erect) by Eugene Dubois and Homo, erectus by Mayer (1950)., Characteristics, Java man was more than 25 feet tall and weighted, about 70 kg., Its legs were thin and erect, but body slightly bent, during movement., Java man was the first pre-historic man, who began, the use of fire for cooking, defence and hunting., Its cranial cavity was 940 cc, which is about, intermediate between Australopithecus (600-700cc), and modern man (1400-1600cc)., l, , l, , l, , l, , l, , l, , Peking man, (Homo erectus Pekinensis, or Pithecanthropus, pekinensis or Sinanthropus, pekinensis), , Discovery, The fossils (skulls, jaws and post cranial bony, fragments) of Peking man were discovered by WC, Pai (1924) from the limestone caves of Choukoutien, near Peking (Peking is the former name of China’s, capital Beijing)., These fossils of Peking man were about six lakh, years old., Characteristics, Peking man was 1.55 to 1.60m tall, i.e., slightly, shorter, lighter and weaker than java man., The cranial cavity of Peking man was 850-1200cc, that is more than Java man., l, , l, , l, , l, , Heidelberg man, (Homo erectus, heidelbergensis), , Discovery, The fossil of Heidelberg man is represented by lower, jaw, which was found from the middle Pleistocene, rocks of Heidelberg (Germany)., Credit for the discovery of Heidelberg man goes to, Otto Schoetensack., Characteristics, It had ape-like lower jaw with all the teeth. The teeth, were human-like., The jaw was large, heavy and lack a chin., Its cranial cavity was probably about 1300cc,, intermediate between erect man (H. erectus) and, Neanderthal man (H. sapiens neanderthalensis)., Heidelberg man is regarded as an ancestor to, Neanderthal man and contemporary to Homo, erectus., l, , l, , l, , l, , l, , l, , www.aiimsneetshortnotes.com
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498, , Telegram @neetquestionpaper, , Handbook of Biology, , Neanderthal man, (Homo sapiens, neanderthalensis), , Discovery, Fossils of Neanderthal man was discovered by, C Fuhlrott (1856) from Neander valley in Germany., Neanderthal man arose about 1,50,000 years ago, and flourished in Asia, Europe and North Africa., Neanderthal man extinct about 25000 years ago., l, , l, , Characteristics, l, , l, , l, , Cro-Magnon man, , Neanderthal man existed in the late Pleistocene, period., Neanderthal walked upright with bipedal movement., Cro-Magnon man (Homo sapiens fossilis) or fossil, man closest to modern man or direct ancestor of, living modern man., , Discovery, Mac Gregor discovered the fossil of cro-Magnon, man from Cro-Magnon rocks of France in 1868., Characteristics, Cro-Magnon man was almost similar to modern, man with about 1.8m height. Orthognathous face,, broad and arched forehead, strong jaws, elevated, nose and well-developed chin as well as dentition., Cranial capacity was about 1650cc, i.e., much, more than modern man (1450cc)., Probably they succeeded from Neanderthal man and, distributed in Africa, Europe and Middle East., Cro-Magnon lived during old stone age which is also, known as Palaeolithic (began more than 2 million, years ago)., l, , l, , l, , l, , l, , Modern man, (Homo sapiens sapiens), , Discovery, It is believed that living modern man first appeared, about 10,000 years ago in the regions of Caspian, sea and Mediterranean sea., Characteristics, Its cranial capacity is average 1450cc, which is, lesser than cro-Magnon., It is distinguished from cro-Magnon merely by slight, raising of skull cap, reduction in volume of cranial, cavity (1,300-1,600cc) thinning of skull bones and, formation of four curves in the vertebral column., Human species (sapiens) have white or caucaroid,, mongoloid and black or negroid races., l, , l, , l, , l, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Evolution, 499, Future Man (Homo sapiens futuris), The organic evolution is a continuous process of nature, which is still, continued at present and probably will remain in future too. It is, believed that in future, human could change as a result of the factors, like gene mutation, gene recombination and natural selection., An American anthropologist HL Sapiro named the future man,, (Homo sapiens futuris which may possess following characteristics, (i) Height will be higher., (ii) Hair will reduce and skull may become dome-shaped., (iii) Body and cranium will be more developed., (iv) The fifth finger may reduce., (v) The age will increase., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 30, Human Health, and Diseases, Human Health, It is defined as a state of complete physical, mental and social, well-being. It is not merely the absence of disease or infirmity., Balanced or good health is a state of optimum physical fitness,, mental maturity, alertness, freedom from anxiety and social, well-being with freedom from social tensions., Health can be affected by the following factors, (i) Lifestyle related problems These are habit and food related, problems. These include diabetes, obesity, etc. Such problems, affect the health reversibly., (ii) Genetic disorders These include deficiencies or defects with, which the child born, it means these are inherited from parents., These are also called inborn errors., (iii) Infections These are health problems caused by infection from, disease causing pathogens., Healthy people are more efficient at work with increased longevity., This leads to reduced Infant Mortality Rate (IMR) and Maternal, Mortality Rate (MMR). There are some other factors also, which have, major impact on our health, such as awareness about diseases and, their effects on different functions of body, vaccination against, infectious diseases, proper disposal of waste, maintenance of hygienic, food and water resources., , Common Diseases in Humans, Any deviation from normal state of health is called disease, in which, the functioning of an organ or body got disturbed or deranged., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Human Health and Diseases, 501, These diseases are caused by microorganisms like bacteria, virus,, fungi, protozoans, worms, etc. These diseases causing organism are, called as pathogens. Diseases can be classified as, Diseases, , Congenital Diseases, , Acquired Diseases, , These diseases are present in human,, since birth or caused due to, mutation, chromosomal aberration or, environmental factors, e.g., alkaptonuria,, sickle-cell anemia, Down syndrome,, Cleft palate, etc., , These diseases develop, after birth and are not transferred, from parent to offspring., , Communicable, , Non-communicable, , (Spread from one, person to other), , (Not spread from one, person to other), , Contagious, , Non-contagious, , (Spread by, direct contact), , (Spread through, indirect contact), , The detailed accounts of these diseases are as follows, , Communicable or Infectious Diseases, These are transferred from one person to another. On the basis of types of, causative agent (pathogen), communicable diseases are of following types, Spirochaetal Diseases, Helminthic Diseases, , i.e., syphilis, , Protozoan Diseases, , i.e., filariasis, taeniasis,, liver rot, ascariasis,, trichinosis, etc., , Rickettsial Diseases, e.g., trench fever, Q-fever,, rocky mountain fever,, spotted fever, etc., , e.g., malaria, sleeping, sickness, kala-azar,, amoebiasis, pyorrhoea, etc., , Communicable, Diseases, , Bacterial Diseases, e.g., typhoid,tetanus,, cholera, T.B., pertusis, etc., , Viral Diseases, e.g., measles, chicken pox,, rabies, mumps, polio,, smallpox, etc., , Fungal Diseases, e.g., athlete’s foot,, ringworm, etc., , Communicable diseases, , Non-Communicable or Non-Infectious Diseases, These diseases are not transferred from an affected person to healthy, person. Among non-infectious diseases, cancer is the major cause of, death., , www.aiimsneetshortnotes.com
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502, , Telegram @neetquestionpaper, , Handbook of Biology, , Non-communicable diseases can be categorised as follows, Hormonal Diseases These diseases occur due to defects, in the production of hormones. These are, • Cretinism (due to the deficiency of thyroxine), • Diabetes (due to the deficiency of insulin), • Dwarfism (due to the hypoactivity of pituitary gland), • Gigantism (due to the hyperactivity of pituitary gland), , Disease of Malfunctioning, , Allergic Diseases, , Diseases caused by, malfunctioning of organs, are cardiac failure, kidney, failure, osteoporosis,, myopia, cataract and, cancer, etc., , These are caused due to the, overactive response of, immune system towards, certain things like dust,, serum, drugs, fabric and, pollens, etc, e.g., sneezing,, irritation, itching, rashes, etc., , Disease Caused by, Addictive Substances, , Non-Communicable, Diseases, , Ageing and, Degenerative Diseases, Degeneration of body, tissue results in disease., e.g., weakening of eye, muscles, arteriosclerosis,, and arthritis, (Joint and bone diseases)., , These are the diseases, or symptoms caused by, the addiction of certain, substances like alcohol,, narcotic drugs, tobacco, and certain psychological, factors, e.g., liver damage,, reduce alertness, etc., , Mental Illness, , Deficiency Diseases, , These are mental, disorders originated, due to any problem,, e.g., schizophrenia,, etc., , These diseases are related to the deficiency of, nutrients in diet.These may be, Protein deficiency Kwashiorkor,marasmus, etc., Vitamin deficiency Pellagra, scurvy, etc., Mineral deficiency Rickets, etc., Iodine deficiency Goitre, etc., , Non-communicable diseases, , Immunity and Immune System, Immunity can be defined as, ‘The self-preparedness (of the body) against invasion by microbes. It, also includes defense against non-microbial antigens and malignancy.’, , Antigens, These are the substances, which evoke an immune response when, introduced in the body., , Criterias for Antigenicity, (i) Molecular size should be > 5000 daltons., (ii) Chemical nature (usually protein and polysaccharide)., (iii) Susceptibility to tissue enzyme., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Human Health and Diseases, 503, (iv) Foreignness., (v) Iso and autospecificity (except lens protein and sperm)., , Antibodies, These are proteins produced within the body by the plasma cells, against antigens., , Structure of Antibodies, The basic unit of all immunoglobulin (Ig) molecules consists of, four polypeptide chains linked by disulphide bonds., The structure is represented diagrammatically as, Light chain, hypervariable, region, , (MW = 23000 d.), Light chain, (MW = 53,000 –, 75,000 d), Heavy chain, , NH2, , NH2, , VL, , SS, , SS, , (Amino terminus) NH2, , VH, SS, , CL, , NH2, Heavy chain, hypervariable, region, , SS, , 1, CH, , SS, SS, , VL = Variable domain of, light chain, CL = Constant domain of, light chain, VH = Variable domain of, heavy chain, CH = Constant domain of, heavy chain, SS = Disulphide bond, , CH2, , Hinge region, = Pepsin/papain, cleavage sites., , CH3, , COO–, , COO–, , (Carboxy terminus), , Antibody structure, , www.aiimsneetshortnotes.com
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504, , Telegram @neetquestionpaper, , Handbook of Biology, , Most of the antibodies are euglobulin and is usually gamma (γ), globulin. All antibodies are immunoglobulins, but all immunoglobulins, may not be antibodies. Immunoglobulins constitute 20-25% of total, serum proteins., , Classes of Immunoglobulins, There are five classes of immunoglobulins. These are described as, follows, IgD, It resembles IgG structurally, and also serves as recognition, receptor for antigen., , IgA, It occurs in two forms, i.e.,, serum IgA (monomer), and secretory IgA (dimer), MW 1,80,000 – 4,00000., , Immunoglobulins, , IgG, It is general purpose antibody,, which enhances phagocytosis, by opsonisation., It has 4 subclasses, G1, G2, G3 and G4, MW - 1,50,000 –1,60,000., , IgM, , IgE, , Its effective valency is 5;, earliest Ig to be synthesised by, foetus. Its detection is useful, in diagnosis of congenital infections., MW = 9,50,000, , Mostly extracellular, it is, chiefly produced in the lining, of intestinal and respiratory, tract., MW = 1,90,000., , Types of immunoglobulins, , Note, IgG protects body fluids., IgA protects body surface., IgM protects the bloodstream., , The action/response of antibodies against antigens is known as immune, response or immunity. Classically, it is divided into two categories, (a) Non-specific or Innate Immunity, It is not affected by the prior contact with the antigen and effective, against all without recognising the specific identities of the enemies,, e.g., skin, sebum, sweat, mucus and acids in stomach are, non-specifically protective., (b) Specific or Acquired Immunity, This immunity is the primary function of the lymphocytes which is, carried out by other cells also. It has separate mechanisms for each, and every enemy. To develop immunity, the prior contact with the, specific antigen is essential. It develops against only to those antigens,, which are not recognised as self., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Human Health and Diseases, 505, The specific immunity may be active or passive., (i) Active Immunity, , It is developed within the body by the introduction of attenuated (heat, suppressed) antigens, which are against lymphocytes. It can also be, activated through vaccination, e.g., polio vaccine, tetanus vaccine, etc., On the basis of action of responding cell, active immunity is of two types, Active Immunity, Cell-Mediated Immunity (CMI), , Humoral Immunity (HI), , This immunity is due to, T-lymphocytes, which got, matured in thymus., , It is due to B-lymphocytes,, which got matured in, bone marrow., , T-lymphocytes, , They produce antibody, on their surface when, exposed to antigen., , B-lymphocytes, , They produce specific, antibody on their surface, when exposed to antigen., , After producing various, types of antibodies, T-cell, itself goes to antigen and, degrades it. No antibody is, released., , Saved as memory, cell for further, response against, same antigen., , Released antibodies, go to antigen, and digest it., , Demonstration of active immunity in organisms, , www.aiimsneetshortnotes.com
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506, , Telegram @neetquestionpaper, , Handbook of Biology, , (ii) Passive Immunity, , It occurs due to the transfer or introduction of antibodies, (immunoglobulins) from outside, e.g., injection of serum against, specific antibodies as Anti-Tetanus Serum (ATS), Anti-Venom Serum, (AVS), etc., During this, readymade antibodies are directly given to protect the, body against foreign agents. The yellowish fluid colostrum secreted by, mother during the initial days of lactation has abundant antibodies, (i.e., IgA) to protect the infant., The foetus also receives some antibodies from their mother through the, placenta during pregnancy. This is also an example of passive, immunity., Immune system is biologically, reticuloendothelial system., The detailed description of reticuloendothelial system is as follows, Reticulo Endothelial System (RES), , Lymphoid System, , Reticular System, , It consists of various, cells and organs., , It consists of phagocytic, cells that are concerned, with scavanging function., , Lymphoid Cells, , Lymphoid Organs, , • Lymphocytes, • Plasma cells, , Central (primary), Lymphoid Organ, , Peripheral (secondary), Lymphoid Organ, , Organs in which precursor, lymphocytes, proliferate, develop, and mature., • Thymus, • Bone marrow, , Organs in which lymphocytes, store, act and recycled., • Lymph nodes, • Spleen (largest lymphoid organ), • Mucosa-Associated Lymphoid, Tissue (MALT), , Components of reticuloendothelial system, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Human Health and Diseases, 507, Cells of Immune System, The various cells performing different functions constitute the immune, system., A close look of structure and functions of these cells are described below, Cells of Immune System, , Dendritic cells, , Null Cell or LGL, , These are Antigen Presenting, Cells (APCs). These process antigens and, present them to T-cell during primary, immune response., They are bone marrow derived cells., These have little or no phagocytic activity., These are of three types, (i) Interdigitating dendritic cells., (ii) Langerhans cell., (iii) Follicular dendritic cell., , (Large Granular Lymphocyte), They do not bear surface Ig, non-adherent, and non-phagocytic with macrophage,, they constitute innate immunity., , Phagocytic Cells, These are of two types, (i) Mononuclear macrophages, of blood and tissue, These are the largest lymphoid cells, with half life of 1 day, while lifespan, of tissue macrophage is, ~7 months. These are important, for chronic inflammation and, cell-mediated immunity., (ii) Microphages, These are polymorphonuclear, leucocytes of blood neutrophil,, eosinophil and basophil., They do not have any role in, specific immune process., , Lymphocyte, Human body contains about 1012, lymphocytes, out of which 109 are, re-newed daily., They are of two types, (i)T-lymphocyte, Thymus derived and constitutes about, 60-70% of peripheral lymphocytes., It is present in paracortical area of, lymph nodes and periarteriolar sheath, of spleen., (ii) B-lymphocyte, 10-20% of peripheral lymphocytes,, responsible for humoral immunity., In spleen and lymph node, they form, lymphoid follicles., , Major Histocompatibility Complex (MHC), l, , l, , Gene for MHC located on short arm of chromosome six, which, code for histocompatibility (transplantation) antigen., Main function of MHC molecule is to bind peptide fragments of, foreign proteins for presentation to antigen specific T-cells., , www.aiimsneetshortnotes.com
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508, , Telegram @neetquestionpaper, , Handbook of Biology, , MHC gene products are classified as, Class-I Antigen, , Class-II Antigen, , Class-III Antigen, , It is glycoproteins, expressed in all nucleated, cells. It is the principle, antigen involved in graft, rejection and cell, mediated cytolysis., , It is glycoproteins restricted to, antigen presenting cell only. It, is responsible for graft versus, host response and Mixed, Leucocyte Reaction (MLR)., , It is soluble proteins of, complement system, e.g.,, heat shock protein and TNF, (α and β)., , Complement System, It is an enzyme cascade that helps to defend against infections. Many, complement proteins (C1-C9) occur in serum as inactive precursors, (zymogens). At the sites of infection, these zymogens are activated, locally and trigger a series of potent inflammatory events., , Activities of Complement System, The complement system shows various activities to digest the antigens., Phagocytes have important role in this system., These activities are shown in following figure, Lysis, , Complement, , Opsonisation, , Bacteria, , Activation of Inflammatory, Response, , Clearance of immune, complexes, , Complement, receptor, , Extravasation, , Ag-Ab, complex, Degranulation, Tissue, Blood, , Target cell, , Phagocyte, , Phagocyte, , Activities of complement system, , Vaccination and Immunisation, It is based on the property of the memory of the immune system., During vaccination, a preparation of antigenic protein or pathogen, or inactivated/weakened pathogen is introduced into the body., Memory B-cell and T-cell are generated by vaccines that recognise the, pathogen quickly on further contact and digest the invaders with a, massive production of antibodies. If the preformed antibodies against, any antigen are introduced into the body, it is called passive, immunisation., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 509, Human Health and Diseases, Allergies, The exaggerated or overactive response of immune system to certain, antigen or pathogen is called allergy. The substances which cause, such immune response are called allergens., During allergies from pollens, animal dander and mites in dust, etc.,, the IgE type of antibodies are produced. The use of drugs like, anti-histamine, adrenaline and steroids helps in reducing such allergic, response., , Autoimmunity, Sometimes due to genetic or other reasons, the immune system of, body is unable to differentiate between self and foreign substance and, start killing the self tissues or cells. This is called autoimmune, disease, e.g,. rheumatoid arthritis, etc., , Acquired Immuno Deficiency Syndrome (AIDS), AIDS is a cell-mediated immune disorder caused by Human, Immunodeficiency Virus (HIV). HIV causes reduction in the number of, helper T-cells, which stimulate the antibody production by B-cell and, ultimately reduce the natural defence against viral infections., First incidence of AIDS was reported from California, USA (1981)., Prof. Luc Montagnier isolated HIV in 1983 at Pasteur Institute,, Paris., Various names are given to AIDS causing agent by different scientist as, LAV-II (Lymphadenopathy-Associated Virus-II) by Luc Montagnier, (1983) France., HTLV-III (Human T-lymphotropic Virus III) by Dr RC Gallo, (1984) USA., HIV (Human Immunodeficiency Virus) common name for LAV and, HTLV by international committee of viral nomenclature (1986), (WHO)., l, , l, , l, , www.aiimsneetshortnotes.com
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510, , Telegram @neetquestionpaper, , Handbook of Biology, , Structure of HIV, HIV belongs to retrovirus (RNA containing) family of viruses. The, detailed description of the structure of virus is as follows, Lipid Bilayer, (forms envelop of virus), , Glycoprotein, Coat (Gp 120 and Gp 41), forming spiked dots giving, look of horse chestnut to HIV., , RNA, (two copies of ssRNA, acts as genetic material), , Core Protein, , Reverse Transcriptase, , (double-layered; inner-P-24, , (helps in making copies, , and P-28 outer covering), , of DNA from RNA itself), , Structure of HIV, , Transmission of HIV, AIDS is a fluid transmitted disease., The modes of transmission of HIV can be pointed as, (i) Unprotected sexual intercourse., (ii) Use of contaminated needles or syringe., (iii) Use of contaminated razors., (iv) Transfusion of infected blood., (v) Artificial insemination., (vi) Prenatal transmission from mother to baby., HIV is found in blood and semen, but it is not transmitted through, (i) Mosquito bites., (ii) Shaking hands with AIDS patients., (iii) Sharing meals towels and toilets., (iv) Hugging or dry kissing with patients., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Human Health and Diseases, 511, Mechanism of HIV Infection, Mechanism of HIV infection can be described diagrammatically as, follows, 1, , HIV, , HIV adhere on host cell, surface (T-cell) by, endocytosis, 2, , 9p 120, CD4, Co-receptor, (CCR5 or CXR4), , Viral RNA, reverse, transcriptase integrase, enzyme and other viral, proteins enter into, host cell-cytoplasm., , Preintegration, complex, 3, , Host cell, , Viral, RNA, , Reverse, transcriptase, , 4, , Integrase, Viral DNA, , Mature Virion, Mature virions, are liberated, which can, infect other, cells., , Reverse transcriptase, enzyme transcribes, viral DNA from RNA., Viral DNA is transported acorss, the host nucleus and gets, incorporated with host genome, with the help of enzyme integrase., , 5, , 9, 8, , Host DNA, New viral, RNA, , 6, 7, , Host, nucleus, , Assembly of new viral particles into, protein coat forming immature HIV., , Host DNA with integrated, viral DNA transcribes viral, RNA in the infected cell., New viral RNA is used as, genomic RNA which, synthesises viral protein., Viral protein gets synthesised, by the process of translation, from viral RNA., , Steps in HIV infections, , Incubation period It ranges from 6 months to 10 years. Average, timing is 28 months., Symptoms Chief symptoms include fever, lethargy, pharyngitis,, nausea headache, rashes, etc., Treatment Although, there is no cure for AIDS, it can be manifested, in two major ways,, (i) Antiviral therapy Drugs against causative agent., Azithmidine and ribovirin are the drugs, which seems to be, promising against AIDS. Zidovudine or AZT was the, first drug used for the treatment of AIDS. Didanosine, (dideoxyionosine-DDI) is another drug employed to treat AIDS., (ii) Immunostimulative therapy Increases the number of, resistance providing cells in the body., , www.aiimsneetshortnotes.com
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512, , Telegram @neetquestionpaper, , Handbook of Biology, , Prevention, Following steps may help in the prevention of AIDS as there is no, vaccine against AIDS., (i) Health education–people should be educated about AIDS, transmission. December 1st is celebrated as World's AIDS Day, to spread the information about AIDS., (ii) Use of disposable needles and syringes., (iii) Blood should be quarantined or screened before transfusion., (iv) Use of sterilised equipments must be insisted, while getting, dental treatment., (v) In sexual relationship, one should be monogamous or safe, sexual practices should be done., (vi) Avoid use of common blades at barber's shop., , Cancer, It is defined as an uncontrolled proliferation of cells without any, differentiation. It is a group of more than 200 different diseases, where, malignant growth or enlargement of tissue occurs due to unlimited and, uncontrolled mitotic division of certain cells and invades surrounding, tissues, forming tumours. Simply, cancer can be defined as mitosis, run amok., , Characteristics of Cancerous Cell, l, , l, , l, , l, , l, , l, , Following are the characteristics of cancerous cells, Self-sufficiency in growth signaling., Insensitivity to antigrowth signals., Evasion of apoptosis., Limitless replicative potential., Induction and sustainment of angiogenesis., Activation of metastasis and invasion of tissue., , Types of Tumours, There are two types of tumours, , (i) Benign Tumours or Non-Malignant Tumours, These remain confined to the site of its origin, do not spread to other, parts of body, grow slow and cause limited damage to the body. It is, non-cancerous., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Human Health and Diseases, 513, (ii) Malignant Tumour or Cancerous Tumour, It contains cancerous cells which break away from their site and can, spread to the other part of the body through the blood stream and, lymphatic system by the process called metastasis. It grows fast., Partially, transformed cell, 1. An epithelial cell, becomes partially, formed., , Blood vessels, , Lymph, vessel, , 2. This cell multiplies, forming a mass of, dysplastic cells, , 3. These dysplastic cells, grow rapidly, forming, a localised cancerous, tumour., 4. The cancer cells secrete, chemicals that allow them, access to other tissues,, the lymphatic system and, the bloodstream., Cancer cell, secretions, , Cancer growth and metastasis, Cancers grow by cell division. Cells can break free from the, tumour and lymphatic systems to other parts of the body,, where they establish secondary tumours. Secondary, tumours often develop in the liver, lungs and lymph nodes., , www.aiimsneetshortnotes.com
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514, , Telegram @neetquestionpaper, , Handbook of Biology, , Types of Cancer, On the basis of its origin, cancer is of following types, Cancer, , Leukaemia, , Sarcoma, , Carcinoma, , Caused due to the excessive, WBCs formation in bone marrow, and lymphatic nodes., Includes gilomas, (cancer of glial cells),, melanomas, (cancer of pigment cells), etc., , Cancer of lymphoid tissues, (lymphoma), connective tissue, (fibrosarcoma, chondrosarcoma),, and muscles (leiomyosarcoma, in smooth muscles and, rhabdomyosarcoma in, stripped muscles)., , Cancer of epithelial cells, (squamous carcinoma),, and glandular tissues, (adenocarcinoma)., Includes lung cancer,, breast cancer, etc., , Theories Related to Causes of Cancer, (i) Mutation Theory, This theory explains that the accumulation of mutation over years may, produce cancer., , (ii) Selective Gene Activation Theory, This theory explains that certain genes that are not normally, expressed, suddenly become active and their product causes cancer., Oncogenes that functions normally are called proto-oncogenes or, cellular oncogenes (C-onc), which under normal conditions, code for, protein that are necessary for cell growth., Mutation in proto-oncogene changes its activity and they loose the, control on growth and division and continuously divide giving rise to a, mass of cells called tumours., Carcinogens are the agents that cause cancer. They can be physical,, chemical or biological., Different carcinogens are as follows, Carcinogens, , Physical Carcinogens, , Chemical Carcinogens, , Biological Carcinogens, , They include ionising, (X-ray, γ-ray) and, non-ionising (UV) radiations., , Include caffeine, nicotine,, pesticides, combustion, products of coal and petrol., , Include viruses like HPV causing, cervical cancer, epstein-barr virus, causing Burkitt’s lymphoma., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Human Health and Diseases, 515, Cancer Detection and Diagnosis, Successful treatment of cancer requires early detection of the disease., Histopathological studies of the tissue and blood, bone marrow tests for, increased cell counts and biopsy are the methods for detecting cancer., Besides these radiography, Computed Tomography (CT) (generates, 3-D image of internal organs by using X-rays) and Magnetic Resonance, Imaging (MRI) are used to detect cancer of internal organs., , Treatment of Cancer, Surgery, radiation therapy, chemotherapy are the common treatments, of cancer., 1. Radiation Therapy Exposure of cancerous parts to X-rays,, which destroy rapidly growing cells. Radioisotopes like Radon, (Rn-220), cobalt (Co-60) and iodine (I-131) are used in it., 2. Immunotherapy It involves natural anticancer immunological, defence mechanism. Monoclonal antibodies are used in it, e.g.,, radioimmunotherapy., 3. Chemotherapy Involves the administration of certain, anticancer drugs, which check cell division. These drugs have, side effects like hair loss, anaemia, etc. Patients are given, substances called, biological response modifiers (e.g.,, interferon), which activate immune system and destroy tumour., , Drugs, These are the chemicals used in the diagnosis, prevention, treatment, and cure of diseases. They change the working style of the body. These, are also called addictive substances or habituating substances., World Health Organisation (WHO) defines drugs as follows, ‘Drug is any substance or product that is used or is intended to be used, to modify or explore physiological systems or pathological states for the, benefit of the recipient’., Drugs can be classified into two major categories as follows, (i) Psychotropic drugs Mood altering drugs, affect behaviour, and mental activity of a person., (ii) Psychedelic drugs Hallucinogens, produce dream like state, with deorientation and loss of true sensory stimulus. They often, make users of see sound and hear colour. These are also, called vision producing drugs as they produce false, imagination., , www.aiimsneetshortnotes.com
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516, , Telegram @neetquestionpaper, , Handbook of Biology, , Psychotropic Drugs, These are classified into four major categories, i.e., tranquillisers,, sedative and hypnotics, opiate narcotics and stimulants., Phenothiazines, Barbiturates, , Major tranquillizers, antipsychotic,, reduce aggressiveness, e.g.,, reserpine, chlorpromazine, etc., , General depressants, reduce, anxiety, known as sleeping pills,, e.g., phenobarbitone,, mephobarbitone, etc., , Benzodiazepines, Minor tranquillizers, antianxiety, drug, reduces sleep, e.g. valium,, flur zepam, etc., , Benzodiazepines, Antianxiety as well as sedative., , Tranquillizers, Decrease tension and anxiety,, produce feeling of calmness, without inducing sleep., , Sedative and Hypnotics, Reduce excitement, induce, sleep, depress CNS., , Psychotropic, Drugs, Opiate Narcotics, , Stimulate nervous system,, make the person alert and, active., , Derived from opium,, relieve pain (analgesic)., , Caffeine, , Morphine, , It is 1, 3, 7 trimethylxanthine,, white crystalline bitter alkaloid,, CNS stimulant, increases Basal, Metabolic Rate (BMR), inhibits, the release of histamine., , Principal opium alkaloid, strong, analgesic, depresses respiratory, centre, results in constipation,, causes addiction., , Codeine, It is methyl-opium, mild analgesic, does, not cause addiction, used in cough syrups., , Smack, Crude byproduct of heroin, known, as brown sugar,, stronger analgesic than heroin., , Pethidine, Sedative and euphoriant, causes, less histamine release, local, anaesthetic action, also called, meperidine, safer in asthmatics., , Heroin, , Stimulants, , Crack, Derivative of cocaine, causes, mental and heart problems., , Betal Nut, Mild CNS stimulant, stains teeth,, contains alkaloid arecoline and a, red tannin., , Amphetamines, Synthetic drug, also called pep-pills,, CNS stimulant, causes wakefulness,, used in dope-test for athletes., , Cocaine, , It is dimorphine or diacetylmorphine,, three times more potent than, morphine, depressant and, dangerous opiate, induces, drowsiness and lethargy., , Natural coca-alkaloid, commonly, called coke, posseses, vasoconstrictor properties, powerful, CNS stimulant, delays fatigue., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Human Health and Diseases, 517, Psychedelic Drugs, They are broadly classified into two groups, , (i) Natural Hallucinogens, They include Lysergic acid Diethylamine (LSD), mescaline, psilocybin,, cannabinoids and belladonna (Datura)., Mescaline, Low potent, white-powdery, alkaloid., , LSD, Psilocybin, Crystalline solid, used in, psychological medicines., , Natural, Hallucinogens, , Belladonna, Seeds of Datura stramonium and, aerial parts of Atropa belladonna, are misused for their hallucinogenic, properties., , Most powerful, always, smoked, causes horrible, dreams, damages CNS,, brings about chromosomal, defects., , Cannabinoids, Include bhang, ganja,, charas (hashish) and marijuana., , (ii) Synthetic Hallucinogens, They include Phencyclidine Piperidine (PCP) and Methylenedioxy, Methamphetamine (MDMA)., (a) PCP (Phencyclidine Piperidine) It is widely used in veterinary, medicine to briefly immobilise large animals. It is available to, addicts as angel dust (white granular powder)., It has stimulant, depressant, hallucinogenic and analgesic, properties. Higher dose of PCP may produce hypersalivation,, vomiting, fever and even coma., (b) Methylenedioxy Methamphetamine (MDMA) It has, CNS-excitant and hallucinogenic properties. It has become, popular in students under the name ‘ecstasy’ drug., , www.aiimsneetshortnotes.com
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518, , Telegram @neetquestionpaper, , Handbook of Biology, , Some Drug Yielding Plants, Common, Name, Hemp plant, , Botanical, Name, , Parts of the Plant, from which the, Product is, Obtained, , Cannabis, Leaves and flowers, sativa or, Cannabis, indica, (cannabinoid), , Product Obtained, , Hallucinogenic products, Bhang from fresh/dried leaves, and flowering shoots of both, male and female plants. Ganja, from unfertilised female, inflorescence. Charas from, flowering tops of generally, female plants. Marijuana from, dried flowering plants., , Poppy plant, (opium poppy), , Papaver, somniferum, , Unripe capsules, (fruits), , Opium (afeem) and its, derivatives, (e.g., morphine,, codeine, heroin, pethidine and, methadone.), , Ergot fungus, , Claviceps, purpurea, , Fruiting bodies, , LSD, , Mexican, mushroom, , Psilocybe, mexicana, , Fruiting bodies, , Psilocybin (Psilocybine), , Tea plant, (a shrub), , Thea, sinensis, , Dried leaves, , Tea, , Coffee plant, , Coffea, arabica, , Dried seeds, , Coffee, , Cocoa plant, , Theobroma, cacao, , Dried seeds, , Cocoa, , Coca plant, (cocaine plant), , Erythroxylon, coca, , Leaves and young, twigs, , Cocaine (Commonly called coke, and crack), , Spineless cactus, (peyote cactus), , Lophophora, williamsii, , Dried tops, (called mescals), , Mescalin (mescaline), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Human Health and Diseases, 519, Addiction, It is the continued repetition of a behaviour despite of its adverse, consequences. Addiction to any substance is a disease and is difficult to, beat., , Drug/Alcohol Addiction (or Abuse), It is the state of periodic or chronic intoxication or dependency of a, person on the regular consumption of drugs and alcohol either in low, or high concentration., , Reasons of Drug/Alcohol Addiction, There are various reasons causing drug/alcohol addiction. They, include, (i) Peer pressure If friends describe about the good feeling of, alcohol or drugs, such inspiration from peer groups acts as a, pressure to start with the drugs., (ii) Frustation or depression People start taking drugs or alcohol, to get solace or relief from personal problems, (iii) Family history Examples of parents or members of the family, using these substances act as the natural stimulant., (iv) Desire to do more physical or mental work Some people, think that the use of such substances provide them mental relief, and increase their working power., (v) Apathy Lack of interest in day to day activities of an individual, may lead to such addictions., (vi) Excitement or adventure Young blood look for some exciting, work and these addictive substances attract them for such, tasks., , www.aiimsneetshortnotes.com
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520, , Telegram @neetquestionpaper, , Handbook of Biology, , Effects of Drug/Alcohol Abuse, Drug/alcohol addiction is a sign of disgrace in society. The addicts are, not liked by friends, colleagues and family., Financial, It could create financial crisis, and poverty as a major, portion of earning is spent to, support such addictions., , Society, , Family, Addiction to such substance, bring about aggresivenes in, person behaviour, which may, cause marital or family strife., , People avoid the person with, such addictions. Addict person, may lose or alienate longtime, friends., , Effects of, Drug/Alcohol, Abuse, , Work, Work performance may decline, due to hallucinogenic properties, of these substances. Person may, start being absent from work place, more often., , Legal, , Health, , Person may start doing, illegal work like theft to, support his addiction., Driving after consuming, such substances may also, pose problems like accidents., , Person may suffer from, various health issues like, depression, less CNS, activity, liver diseases, etc.,, after taking these substances, on regular basis., , Effects of drug/alcohol abuse, , Withdrawal Symptoms Include anxiety, nervousness, irritability,, depression, insomnia, dryness of throat, disturbed bowels, lack of, concentration, increased appetite and craving for tobacco., , De-addiction, Addiction to drugs or alcohol vary widely according to the types of, drugs involved, amount of drugs or alcohol used, duration of the drug, alcohol addiction, medical complications and the social needs of the, individual., The following four ways can cure the drug/alcohol addicts, (i) Addiction treatment is a methodical and slow process, e.g., if an, addict is used to smoke fifteen cigarettes a day, make sure that, he/she reduces three cigarettes by the end of the month. This is, because his body would not be able to bear the strain of more, cigarettes. This may lead to serious complications., (ii) Addiction rehabilitation centre can provide a temporary relief to, the addicts problems., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Human Health and Diseases, 521, (iii) De-addiction help can be provided through the means of friends, and family members. Active interest in de-addiction process can, help the addict tremendously by means of counselling., (iv) There are many natural therapies available to cure the patient., These therapies are permanent. These therapies work well in, the mindset of an addict. Once the patient's mindset is changed,, he can take control of his life without any external assistance., , Adolescence, World Health Organisation (WHO) defines adolescence as the period of, life between 12 and 19 yrs of age. It is the formative period of both, physical and psychological health and is the preparatory phase for the, adult life. That's why a healthy adolescence is a critical juncture for a, healthy adulthood., , Characteristics of Adolescence, l, , l, , l, , l, , Imaginary Audience False belief in adolescents that other are, intensely interested in their appearance and judge their every move., Metacognition Also called introspection. It is the capacity to reflect, on our own thoughts and behaviour., Egocentrism Lack of differentiation between some aspects of self, and other, unpleasant behaviours., Personal Fables Belief in adolescents that they are highly special, and destined to live a heroic or legendary life., , Adolescence and Drug/Alcohol Abuse, It is accompanied by several biological and behavioural changes., Curiosity, need for adventure and excitement and experimentation, may constitute the common causes, which motivate adolescents to start, taking drugs and alcohol., Other causes include peer pressure, family history, media, etc., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 31, Strategies for, Enhancement in, Food Production, According to the theory given by TR Malthus, the world’s population, is increasing geometrically, i.e., 2, 4, 8, so on. As the cropping area is, not increasing significantly, the search for alternate food resources and, strategies for enhancement in food production plays an important role., The advanced techniques in animal husbandry and plant breeding, play an important role in enhanced food production. Several methods, of enhanced food production and their detailed descriptions are given, here., , Animal Husbandry, It is the science of rearing, caring, feeding, breed improvement and, utilisation of domesticated animals. It deals with the raising of, livestock, poultry farming, fisheries, sericulture, apiculture and lac, culture. The animals used for transport, milk, meat and agriculture, are collectively called livestock., Despite having large portion of livestock population, India contributes, only 25% of world’s farm produce, it means that the productivity per, unit area is very low., , Management of Farms and Farm Animals, In farm management, we deal with the processes and systems that, increase the yield and improve the quality of products., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 523, , Strategies for Enhancement in Food Production, , Better yield primarily depends upon the quality of breed in the farm., For the yield, potential have to be realised and the farm animals have, to be well-looked after. Following things should be kept in mind for, proper farm management., Farm animals should be housed well., They should have proper, scientific diet., Farm animals must avail adequate water., They should be maintained disease-free., Proper maintenance of hygiene and sanitation., l, , l, , l, , l, , l, , Even after ensuring above measures, a farm should be inspected in, regular intervals and the record keeping of these inspections should be, maintained., , Livestock, The term ‘livestock’ is used for domesticated animals and it is a part of, modern agriculture. On the basis of utilities, livestock can be, categorised into, (a) Milk yielding animals Cows, buffaloes and goats provide us, milk, which are used to obtain animal protein and serve as a, perfect natural diet., (b) Meat and egg yielding animals Sheep, goat, pigs, ducks, and fowls provide us meat and eggs., (c) Animals utilised as motive power Buffaloes, horses,, donkeys, bullocks, camels and elephants are used in transport, and ploughing the fields., (d) Wool giving animals Sheep are reared for obtaining wool, from their hide., (e) Miscellaneous uses The hides of cattle are used for making a, variety of leather goods., Examples of Some Domesticated Animals, Here, several animals of livestock category are described with their, detailed descriptions here., Cow or Zebu (Bos indicus), , It is sometimes known as humped cattle. Cow (Bos indicus) is one of, the most important milk yielding cattle in the country., The castrated male cows, i.e. bullocks are used in farm practices and, drawing carts., , www.aiimsneetshortnotes.com
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524, , Telegram @neetquestionpaper, , Handbook of Biology, , The important Indian breeds and their related aspects are as follows, , Tharparkar, It is found in several, districts of Rajasthan., This breed can be, extensively used for, commercial production., , Haryana, Mainly found in, Karnal, Hisar and, Gurgaon district of, Haryana., Kankrej, It is mostly found in, Gujarat and Rajasthan., It is one of the oldest, breed in India., , Ongole, It is our mute, ambassador to many, countries. Calves, sometimes born with, red colour, but as they, grow, turn white., , Sahiwal, It is originated from, Sahiwal district of, Pakistan, Punjab. It is, one of the best dairy, breed., , General, Utility, Breeds, , Deoni, It is reported from, various regions of, Maharashtra and, Karnataka. It is, originated from gir, breed about, 500 yrs ago., , Milch, Breeds, , It refers to, those varieties, which provide, milk., , These cow, varieties are, for doing labour, in the fields., , Gir, It is originated in, Gir hills of Gujarat., This breed is known, for its ability to, tolerate stress., Red Sindhi, It has been originated, in Karachi Pakistan., It has white patches, on red body., , Indian, Cows, , Malvi, Their home tract is, around the Malva, district of MP and, Jhalawar of Rajasthan., These have darkspot on, neck and dished forehead., Hallikar, It is a drought breed of, Southern India. It is medium, sized, compact and muscular., The face is long and forehead, is bulgy., , Drought, Breed, , These varieties, of cow can perform, both works efficiently., , Nagori, These are white, light, grey in colour. They, have originated in, Nagaur district of, Rajasthan., Kangayam, These are also present, in Indian state, Tamil Nadu., These have dark colours in, hump, back and forehead., , Various cow varieties in India, , Buffalo (Bubalus bubalis), , Indian buffalo is a major cattle raised for milk production. 26 breeds of, buffalo are found in India., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 525, , Strategies for Enhancement in Food Production, The important Indian breeds are, , Bhadawari, This breed is mostly found, in several districts of UP, and MP. Average milk yield, is 800-1000 kgs per lactation., Surti, Also known as Daccani, Gujarati. Coat colour, varies from rusty, brown to silver grey., It generally gives, 1000-1300 kgs, milk per lactation., , Nagpuri or Ellichpuri, It is also called Barari,, commonly found in several, districts of Maharashtra. It, has white patches on face., Average milk production is, 700-1200 kgs per lactation., , Indian, Buffaloes, , Murrah, It is most important, buffalo breed commonly, found in several districts, of Haryana. It is jet black, in colour and gives about, 1500-2500 kgs milk, per lactation., , Nili Ravi, It is originated, around the river, Ravi. The specific, feature of this breed, is wall eyes. The milk, yield is 1500-1850 kgs, per lactation., , Jaffrabadi, It is generally found, in several districts of, Gujarat. It is the heaviest, Indian breed. Average, milk yield is 1000-1200 kgs, per lactation., Mehsana, It is a dairy breed, of buffalo found in the, state of Maharashtra and, Gujarat. It was produced, by breeding between surti, and murrah., , Various buffalo varieties in India, , Horse (Equus caballus), , It is the first beast of burden. Physically, it is firm footed, strong, fast, runner, intelligent and barns easily. Breeds of Indian horses and the, regions in which, they are found is shown in the following table, Breeds of Indian Horses, Name, Manipuri, , Regions, North-Eastern mountains, , Marwari, , Rajasthan, , Zanskari, , Ladakh, , Kathiawari, , Rajasthan and Gujarat, , Bhutia, , Punjab and Bhutan, , Spiti, , Himachal Pradesh, , Sheep (Ovis aries), , It is reared for wool and mutton. It is herbivorous in nature and feeds, on farm-waste, oil cake and other cattle feeds., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 526, , Handbook of Biology, , Important Indian sheep breeds are as follows, Breeds of Indian Sheep, Breed, , Distribution, , Uses, , Bhakarwal, , Jammu and Kashmir, , Undercoat used for high quality, woollen shawls, , Lohi, , Punjab, Rajasthan, , Good quality wool, milk, , Deccani, , Karnataka, , Mutton, no wool, , Rampur-Bushair Uttar Pradesh, Himachal Pradesh, , Brown-coloured wool, , Marwari, , Gujarat, , Coarse wool, , Nali, , Haryana, Punjab, Rajasthan, , Superior carpet wool, , Patanwad, , Gujarat, , Wool for army hosiery, , Nellore, , Maharashtra, , Mutton, no wool, , Camel, , It is mostly used in deserts and commonly known as ‘ship of deserts’., Its main uses are transport, ploughing and drawing water, etc. Some of, the species of camels are Camelus dromdarius (Arabian camel),, Camelus ferus (Bactrian camel), etc., , Improvement of Animals through Breeding, Scientific methods are used for the improvement of animals, some of, these scientific methods are as fallows, , Breeding, Breeding is the cross between animals of two breeds (i.e., a group of, animals related by descent and similar in most characters)., It can be sub-categorised as, Breeding, Outbreeding, , Inbreeding, It is the mating of closely related, individuals for 4-6 generations. Increasing, homozygosity leads to the loss of variation, and stabilisation of pureline. Continued, inbreeding results into the loss of, productivity i.e., inbreeding depression., , Outcrossing, It is mating between unrelated, members of same breed, but, have no common ancestors, in 4-6 generations. The, resultant individual is known as, outcross., , The mating between two, unrelated individuals., , Cross Breeding, It refers to the cross of superior, male of one breed with superior, female of another breed, e.g.,, Bikaneri (ewes) X Merino (rams), Hisardale (sheep)., , Interspecific Hybridisation, It refers to the crossing, between male and female, animals of two different, species, e.g., Mule and, Hinny., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 527, , Strategies for Enhancement in Food Production, Advanced Methods of Breeding, There are three following advanced methods of breeding, (i) Artificial Insemination (AI), , It is a method of controlled breeding in which semen from the selected, male parent is injected into the reproductive tract of selected female, parent., Advantages of artificial insemination are, (a) Semen collected can be frozen for later use., (b) Semen collected can be transported in frozen form., (c) Help us to overcome several problems of normal mating., (ii) Multiple Ovulation Embryo Transfer Technology (MOET), It is a programme for herd improvement in animals like cattle, sheep,, etc. In this method, the hormones like FSH activity are injected into, female to promote super ovulation which can be fertilised by either, superior male or artificial insemination. The fertilised egg of 8-32 cells, can be transferred to receptive surrogate mothers., (iii) Transgenesis, It involves the transfer of gene into special cell or embryos. In this, case, the unfertilised egg is enucleated by treating it with, cytochalasin-B and the blastula stage nuclei are obtained from, embryo donor., , Livestock Diseases, There are several infectious diseases that commonly affect the, livestock animals. Some of these are listed in the table below, Disease, , Pathogen, , Affected Livestock, , Foot mouth disease, , Virus (RNA Amphthovirus), , Cattles-sheep, goat, pigs, , Rinderpest (cattle plaque) Rinderpest virus, , Cattle-buffaloes, sheep, goat, , Cowpox, Anthrax (splenic fever), , Cowpox virus, Bacillus anthracis, , Cows (and even humans), Cattle-camel, sheep, goat, , Pneumonia, , Streptococcus/Diplococcus, , Cattles, , pneumoniae, Mastitis, Tick fever, , Corynebacterium pyogenes, Babesia bigemina, , Cattles, Cattles-buffaloes, , Coccidiosis, Ascariasis, Fascioliasis (liver rot), , Eimeria, Isospora, Ascaris, Fasciola hepatica,, Fasciola gigantica, , Poultry, cattle-sheep, swine, Cattle-pig, sheep, Cattle-sheep, goat., , www.aiimsneetshortnotes.com
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528, , Telegram @neetquestionpaper, , Handbook of Biology, , Pisciculture/Fish Farming/Culture Fishery, It can be defined as, ‘The scientific rearing and management of fishes in water bodies under, controlled conditions’. It is established to capture, preserve, exploit and, utilises various types of fishes, prawns, lobsters, crabs, oysters, other, molluscs, etc., Fishery can be categorised into, Fishery, On the basis, of products, , Fin Fishery, It is the culture and, management of, cartilaginous, and bonyfishes., , On the basis of water, source of fish production, , On the basis of mode, of obtaining fishes, , Shell Fishery, , Capture Fishery, , It is the culture, and production, of crustaceans, and molluscs., , The fish is caught, from natural water,, both marine and, inland., , Culture Fishery, , Freshwater Fishery, , Marine Fishery, This includes capture, fisheries in ocean and seas., , Fish culture in river, canal, lakes,, resevoir, tank, ponds, and paddy fields., , Growing various types, of aquatic organisms in, water bodies is called, culture fishery., , Brackish Water Fishery, Fish culture in slightly, salty habitat as estuary., , Steps used in Pisciculture, The following steps are used in fish farming or pisciculture, Breeding, , It is first step of pisciculture and divided into two types, i.e.,, Natural breeding Fishes allowed to breed naturally and, eggs collected manually., Induced breeding The sperm and ova collected separately, to allow desired fusion., , Hatching, , Fertilised eggs are kept in hatching pits. After few days small, (4-5 mm), fish fries originate., , Nursery Ponds, , Fish fries transferred to ponds contain natural, zooplankton and phytoplankton. Fish fries live here for, 15-30 days, to grow into fingerlings., , Rearing Ponds, , Fingerlings transferred in large tanks for 2-3, months, untill they attain size of about 20 cm., , Stocking Ponds, , Now, these fishes are transferred in large ponds till maturity., , Harvesting, , The big sized fishes are captured for marketing and, smaller one again released into stocking ponds., , Fishes are used as food, in controlling diseases and in the production of, fish oils (cod-liver oil is rich in vitamin-A and D), fish manure (bones of, fishes), fish glue, shagreen (sharp placoid scales of shark used for, polishing), leather (skin of sharks) and artificial pearl., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 529, , Strategies for Enhancement in Food Production, , Poultry, The term Poultry refers to rearing of fowl, geese, ducks, turkeys and, some variety of pigeons, but more often it is used for fowl rearing., Fowls are reared for food or for their eggs., Poultry birds reared for meat are called broilers., Female fowls raised for egg production are called layers., Cockerel is a young male fowl and rooster is mature male fowl., l, , l, , l, , The hens normally start laying eggs from February and continue till, August. The average production by an Indian breed is about 60 eggs, per annum., , Poultry Feed, It includes bajra, jowar, barley, maize, wheat, rice bran, oil-cake, fish, meal, bread, green residue of vegetables, salt, vitamins and minerals., Now-a-days, readymade poultry feed is also available in the market., , Poultry Products, The fowls are reared to obtain following useful products for human, (i) Eggs These are the rich source of easily digestable animal, protein. These are the good sources of calcium, protein, iron,, vitamins and a moderate amount of fat. Each egg consists of shell, and shell membranes (12%), albumin and chalaza (56%) and yolk, (32%)., (ii) Poultry Meat It is a good source of nutrition for non-vegetarians., (iii) Feathers They are used for the commercial purposes such as for, making pillows and quilts., (iv) Manure It is obtained from excreta of poultry birds and is highly, valuable for field crops., Some indigenous breeds of fowls include, Assel (best table bird) It has high endurance and fighting qualities., Chittagong or Malay It grows faster and have good taste., Ghagus Big and hardy breed found in South India., Bustra It is minor breed found in Gujarat and Maharashtra., l, , l, , l, , l, , Large increase in the egg production in India has been named as, silver revolution., , www.aiimsneetshortnotes.com
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530, , Telegram @neetquestionpaper, , Handbook of Biology, , Apiculture/Bee-Farming, ‘Apiculture is the rearing, management and care of honeybees for the, obtaining honey, wax and other substances’., For apiculture large places called apiaries or bee farms are, established scientifically., The Khadi and Village Industries Commission (KVIC) and the Indian, Council of Agricultural Research (ICAR) are making efforts to raise the, commercial production of honeybees products., , Species of Honeybees, Four species of honeybees are reported in different parts of India,, which are as follows, (i) Apis florea F. (Little bee) Docile bee rarely stings and can be, easily used for honey extraction., (ii) Apis indica F. (Indian bee) It can be easily domesticated and is, most commonly used for the honey production. Therefore, it is, reared in artificial hives., (iii) Apis dorsata F. (Rock bee) It is a giant bee and yields, maximum honey., (iv) Apis mellifera F. (European bee) Best species from commercial, point of view., , Products Obtained from Apiculture, Honey, Beeswax, It is yellowish or greyish, brown-coloured waxy, substance. It is completely, insoluble in water, but, completely soluble in, organic solvents as ether., It is secreted by wax, glands of worker bees., , Propolis, Propolis and balm are other, substances. They are used in, repairing and fastening of, combs., , Products, of, Apiculture, , It is white to black in colour and, sweet in taste. Its pH is 3.9. It is, good blood purifier and curative, for ulcers on tongue and, alimentary canal., Chemical composition of honey is, (a) Ash 1.00%, (b) Enzyme and pigments 2.21%, (c) Maltose and other sugar 8.81%, (d) Water 17.20%, (e) Dextrose 21.28%, (f) Levulose 38.90%, (g) Iron, calcium and sodium, , Bee venom, It is used in various ayurvedic, medicines used for arthritis and, snake bites., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 531, , Strategies for Enhancement in Food Production, Colony and Castes/Social Organisation of Honeybees, , Honeybees are social and polymorphic insects, live in highly organised, colonies. An ordinary colony has about 40-50 thousand individuals,, consisting of three main types., 1. Queen, The queen is large-sized bee, responsible for laying eggs. She lays up to, 2000 eggs everyday of each season. Queen lays both fertilised (2n) and, unfertilised (n) egg. The workers and queen originate from fertilised, egg, while drones originate from unfertilised egg., 2. Drone, It is haploid fertile male. Drones are larger than workers and are quite, noisy. They fail to collect food, but eat voraciously. These are stingless, and their main role is to mate with queen., 3. Workers, These are diploid, sterile female. Their size is the smallest among all, castes., Total indoor and outdoor activities are performed by workers only. For, this purpose, they have been provided with some specific features such as, (a) They have a powerful sting for defence., (b) They have long proboscis for sucking the nectar., (c) They have strong wings for fanning., (d) For collection of pollens, they have pollen baskets., (e) They have four pairs of pocket like wax secreting glands on, ventral surface of second to fifth abdominal segment., Workers live for 3-12 months. The function of workers changes with, age. During first half of their life-they remain engaged in indoor, duties as scavangers, nurse bees, fanner bees and guard bees., During the second half of their life, they perform outside duties as, scout bees and forager bees., Honeybee, (Apis mellifera), , Worker, Queen, , Drone, , Colony members of honeybees, , www.aiimsneetshortnotes.com
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532, , Telegram @neetquestionpaper, , Handbook of Biology, , Life Cycle of Honeybees, The life cycle of honeybees have 4 prominent stages. The eggs layed by, queen hatches into larva within 24 hrs of formation. The larvagets, metamorphosed into pupa which later matures into adult bee. The, diagrammatic representation of life cycle of honeybee is as follows, , Adult, , Egg, , Pupa, , Larva, , Life cycle of honeybees, , Sericulture, It is the production of raw silk on commercial scale by rearing practice, of the silkworm., , Silk, It is a pasty secretion of caterpillar of silkworm during cocoon, formation. It is secreted from the salivary glands of silkworms., Silk is composed of following two types of proteins, (i) Fibroin Constitutes 80% of the silk thread., (ii) Sericin Constitutes 20% of the silk thread., Four types of silk are produced in India. These are mulberry silk, (contributes about 91.7%), eri silk (contributes about 6.4%), tasar silk, (contributes about 1.4%) and muga silk (contributes about 0.5%)., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 533, , Strategies for Enhancement in Food Production, Species of Silkworm, Some species of silkworm are as follows, , (i) Mulberry silkworm (Bombyx mori) It belongs to family–, Bombycidae, native to China, but now it has been introduced in, different countries., (ii) Tasar silkworm (Antheraea paphia) It is found in China, India, and Sri Lanka. Caterpillars of this silkworm feed on oak, sal, ber, and fig plants. It belongs to the family–Saturniidae., (iii) Muga silkworm (Antheraea assama) Native to Asom (India),, and it belongs to family–Saturniidae. Caterpillars feed on, Machilus and Cinnamon plants. Silk produced by this moth is, known as muga silk., (iv) Eri silkworm (Attacus ricinii) It feeds on castor leaf and, belongs to family–Saturniidae. Life history of this worm, resembles with that of mulberry worm., (v) Oak silkworm (Antheraea pernyi) Oak silkworm is found in, Japan and China and feeds on oak plant. It also belongs to the, family–Saturniidae., (vi) Giant silkworm (Attacus altas) This worm is found in India, and Malaysia and is the largest of living insects., , Process of Sericulture, The sericulture includes following steps, Stifling, , It is the killing of cocoons through hot water, dry heat,, sun exposure (3 days) and fumigation., , Reeling It means removal of silk threads from the killed cocoons., The removed silk is called raw silk., , Spinning Twisting of several threads of raw silk to get fibre silk, is called spinning., , Lac Culture, The lac is obtained from the Indian lac insect Laccifer lacca, (Tachardia lacca)., The lac insect feeds on the sap of the host tree (palash)., , Chemical Composition of Lac, It contains large amount of resins, sugar, water and other alkaline, substances., , www.aiimsneetshortnotes.com
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534, , Telegram @neetquestionpaper, , Handbook of Biology, Resin, , 68 to 90%, , Dye, , 2 to 10%, , Wax, , 6%, , Albuminous matter, , 5 to 10%, , Mineral matter, , 3 to 7%, , Water, , 3%, , Shell lac is used in the preparation of varnishes, paints and polishes, and is also used in making gramophone records, printing ink, buttons, and pots and in filling ornaments such as bangles and bracelets. It is, also used as insulating material., , Plant Breeding, It is purposeful manipulation of plant species in order to create desired, plant types that are better suited for cultivation, give better yield and, are disease resistant. Plant breeding programmes are carried out in, systematic way worldwide., The main steps in breeding a new genetic variety of a crop are, Collection of variability, Evaluation and selection, of parents, , For effective exploitation of natural genes available in the, population, the collection and preservation of all the different, wild varieties, species and relatives of the cultivated species, is done. The collection is called germplasm collection., The germplasm is evaluated to identify the, parent with desirable characters, which is further, used in the process of fertilisation., , Cross hybridisation among The set of different desired characters can be combined, through hybridising these parents. It is very time consuming, the selected parents, , and tedious process. One among several progeny individual, is true hybrid., , Screening and testing of, superior recombinants, , It is the process of selection of hybrid with desired character, combination. It is crucial process and requires careful scientific, evaluation of the progeny., , Testing, release and, commercialisation of, new cultivers., , The newly selected variety is evaluated on the basis of various, performance parameters in varied conditions. Later, these are, released as the product in market for commercial purpose., , Mutation Breeding, When mutations are artificially induced in a crop for crop, improvement, it is known as mutation breeding. Mutations can be, artificially induced by certain agents called mutagens, e.g., X-rays,, β-rays, γ-rays, UV-rays, nitrous acid, maleic hydrazide, hydrazine,, Methyl Methane Sulphonate (MMS), Ethyl Methane Sulphonate, (EMS), etc., Like Sharbati Sonora was produced from Sonora 64, some new crop, varieties are also developed by mutation breeding viz. NP-386 (wheat),, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 535, , Strategies for Enhancement in Food Production, , Jagannath (rice), Arunna (castor), Mu-7 and Indore 2 (cotton), Pusa, Lal Meeruti (tomato), Primex (white mustard), etc., , Indian Hybrid Crops of High Yielding Varieties (HYVs), With the development and advancement in the agricultural techniques, during Green Revolution, several high yielding varieties of crops, were introduced in India. It includes the semidwarf varieties of rice, (e.g. Jaya and Ratna) and wheat; high yielding and disease resistant, varieties of wheat (e.g. Sonalika and Kalyan Sona), etc., Green Revolution, A series of research, development and technology transfer initiatives occurrring, between the 1940s and the late 1970s that increased agriculture production, worldwide is called Green Revolution. The initiatives led by Norman E, Borlaug, the Father of Green Revolution is credited with saving over billion, people from starvation., This revolution is credited with the development of high yielding varieties and, modernisation of management techniques, by the use of synthetic fertilisers, and pesticides by the farmers., , Plant Breeding for Disease Resistance, Resistance of the host plant for diseases, is the ability to prevent the, pathogens from causing diseases and is determined by the genetic, constitution of the host plant., The disease resistance can be developed in plants through conventional, breeding technique or mutation breeding., During conventional breeding technique, the following steps take place, 1. Screening the germplasm for resistance resource., 2. Hybridisation of the selected parent., 3. Selection and evaluation of the hybrids., 4. Testing and release of new varieties., The plant variety of various crops and their disease resistance is shown, in the following table, Disease Resistant Varieties, Crop, , Variety, , Resistance to Diseases, , Wheat, , Himgiri, , Leaf and stripe rust, hill bunt, , Brassica, , Pusa Swarnim (Karan rai), , White rust, , Cauliflower, , Pusa Shubhra, Pusa Snowball K-1, , Black rot and Curl blight black rot, , Cowpea, , Pusa Komal, , Bacterial blight, , Chilli, , Pusa Sadabahar, , Chilly mosaic virus, tobacco, mosaic vrius and leaf curl, , www.aiimsneetshortnotes.com
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536, , Telegram @neetquestionpaper, , Handbook of Biology, , Plant Breeding for Resistance Against Insect Pests, For the development of insect pest resistance, the similar steps are, taken such as the collection of resistant gene from the cultivated or, wild varieties and transfer of these genes to targeted host., Some released crop varieties bred by hybridisation and selection for, insect pest-resistance are given below, Insect Resistant Crops, Crop, , Variety, , Insect Pests, , Brassica (rapeseed mustard), , Pusa Gaurav, , Aphids, , Flat bean, , Pusa Sem 2,, , Jassids, aphids and fruit borer, , Pusa Sem 3, Okra (Bhindi), , Pusa Sawani, , Shoot and fruit borer, , Pusa A-4, , Plant Breeding for Improved Food Quality, According to a survey, about 840 million people in the world do not, have adequate food to meet their daily requirements. A far greater, number, i.e., about 3 billion people suffer from deficiency of, micronutrients, vitamin and proteins. This deficiency is called hidden, hunger. Diet lacking micronutrients increase the risk for diseases,, reduced lifespan and mental disabilities., , Biofortification, The breeding methods have been used to produce crops with high, levels of vitamins, proteins and minerals, to improve the public health., Breeding for improved nutritional quality is undertaken with the, objectives of improving, (i) Protein content and quality, (ii) Oil content and quality, (iii) Vitamin content, (iv) Micronutrient and mineral content, In 2000, maize hybrids that had twice the amount of the amino acids,, lysine and tryptophan, compared to existing maize hybrids were, developed. Wheat variety Atlas-66 having a high protein content has, been used as a donor for improving cultivated wheat., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 537, , Strategies for Enhancement in Food Production, , Single Cell Protein (SCP), Conventional agricultural production of cereals, pulses, vegetables,, fruits etc., may not be able to meet the demand of food with the rate at, which human and animal population is increasing., The shift from grain to meat diets also creates more demand for cereals, as it takes 3-10 kg of grain to produce 1 kg of meat by animal farming., One of the alternate sources of proteins for animal and human, nutrition is Single Cell Protein (SCP). Microbes are being grown on, industrial scale as a source of good protein., Microbes like Spirulina can be grown easily on materials like waste, water from potato processing plants (containing starch), straw,, molasses, animal manure and even sewage to produce large quantities, and can serve as food rich in protein, minerals, fats, carbohydrate and, vitamins., Such utilisation also reduces environmental pollution. It has been, estimated that in a day, 250 g of microorganisms like Methylophilus, methylotrophus, because of its high rate of biomass production and, growth can be expected to produce 25 tonnes of protein., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 32, Microbes in, Human Welfare, A large variety of microorganisms constitute the major component of, biological system, as they are present everywhere like soil, water, air,, inside our bodies and of animals and plants., The branch of science which deals with the study of different aspects of, microorganisms is known as microbiology and Louis Pasteur is, considered as Father of Modern Microbiology., Various microorganisms can tolerate extreme conditions like high, salinity (halophiles), deep inside temperature (thermophiles) and, in highly acidic atmosphere (thermoacidophiles)., By infecting the living organisms, microorganisms cause serious, diseases in plants, animals and humans. Thus, microorganisms affect, human beings both directly and indirectly., Many microorganisms are also very useful to human beings. We use, several microbial products almost everyday., The uses of microorganisms in various fields are discussed here, , Microbes in Household Products, (Domestic Microbiology), The microbes have been used to make several products such as curd,, cheese, butter, vinegar, etc., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Microbes in Human Welfare, 539, Some important products produced by microorganisms are mentioned, below, Vinegar, It is produced by, fermentation process, induced by Acetobacter, aceti., , Fibre Separation, Bacteria are used in, separation of fibre such, as flax, hemp and jute., , Curd, Lactic Acid Bacteria, (LAB) grows in milk, and converts it into curd., , Microorganism, in Households, , Butter, , Dosa, Idli, Toddy, The dough and plant sap, are used (after fermentation), in making these products., , Cheese, The sweet and sour cream, It is a microbial product of, is churned in the presence of, milk. Various types of cheese are, organisms like Streptococcus, produced by several organisms., lactis and Leuconostoc, citrivorumare to produce butter. Bread/Dough, Common yeast Saccharomyces, cerevisiae is used as leavening, agent in baking industry., , Household applications of microbes, , Microbes in Industrial Products, (Industrial Microbiology), Microorganisms such as bacteria, fungi, yeasts, etc., are now used in a, wide range of industrial processes. The study of microorganisms in, industrial production processes is known as industrial microbiology., The microorganisms are usually cultured in large fermentation, chambers called as fermentors, under controlled conditions., Following are the products synthesised industrially through microbes, (i) Antibiotics These are chemical substances which are, produced by microorganisms and can kill or inhibit the growth, of other disease causing microorganisms., A microorganism which produces antibiotic is called antibiont., The term ‘antibiotic’ was first defined by Waksmann in 1942., The first antibiotic was penicillin (wonder drug), isolated, from Penicillium notatum (a mould), by Alexander Fleming, in 1928., , www.aiimsneetshortnotes.com
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540, , Telegram @neetquestionpaper, , Handbook of Biology, , Chief antibiotics and their source organisms are given in following table, Antibiotics and Their Source, Antibiotic, , Source, , Penicillin, , Penicillium notatum and, P. chrysogenum, , Streptomycin, , Streptomyces griesus, , Erythromycin, , S. erythreus, , Viomycin, , S. floridae, , Chlorotetracycliin, , S. aurofaciens, , Terramycin, , S. rimosus, , (ii) Alcohols The most important alcohol, i.e., ethanol or ethyl, alcohol, (CH3CH 2OH ) is used as solvent, a germicide, a beverage,, an antifreeze, a fuel, a depressant and is a versatile chemical, intermediate for other chemicals., The most widely used sugar for ethanol fermentation is, blackstrap molasses, contains about 35-40% sucrose, 15-20%, invert sugars such as glucose and fructose and 28-35% of, non-sugar solids. The whole process of ethanol production can, be summarised as follows, C6H12O6 + Yeast → 2C2H5OH + CO2 + Energy, Glucose, , Ethanol, , Several organisms like yeast (i.e., Saccharomyces cerevisiae,, S. uvarum) and bacteria (i.e., Clostridium sporogenes,, C. indolis, C. sphenoides, Zygomonas mobilis and Leuconostoc, mesentroides, etc.) are involved in ethanol production,, industrially., (iii) Nutritional supplements Microorganisms are also used as a, source of several nutritional supplements., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Microbes in Human Welfare, 543, Various strains of non-pathogenic Clostridia have shown to infiltrate, and replicate within solid tumours. Clostridia, therefore have the, potential to deliver therapeutic proteins to tumours., Lactobacillus species has therapeutic properties, anti-inflammatory and anticancer activities., , including, , Serum and vaccines produced by various microorganisms are used to, induce immunity among human beings., The alkaloid released from Claviceps purpurea called ergotinine,, stimulates the muscles of uterus and is used to assist childbirth and, controls uterine haemorrhage., Some Other Important Products of Microorganisms, Products, , Microorganisms, , Cyclosporin-A, 11-membered cyclic oligopeptide, an, immunosuppressive that inhibits activation, of T-cell response to transplanted organs., , Trichoderma polysporum and, Tolypocladium inflatum., , Statins, Inhibitor of enzyme HMG Co-A reductase, of liver, lowers LDL cholesterol level., , Yeast–Monascus perpureus., , Microbes as Biofertilisers and Biocontrol Agents, (Agricultural Microbiology), To protect the environment and control soil pollution, the biofertilisers, and manures are used in modern agriculture, termed as organic, farming., , Biofertilisers, These are the nutrient materials obtained from the living organisms or, their remains, used for enhancing the fertility of soil., Biofertilisers contain some organisms which can bring about nutrient, availability to the crop plants., The main sources of biofertilisers are, (i) Nitrogen-fixing bacteria (free-living and symbiotic), (ii) Nitrogen-fixing cyanobacteria (free-living and symbiotic), (iii) Mycorrhizal fungi, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Microbes in Human Welfare, 545, Bioherbicides can be categorised as, Smoother Crops, The crops which do not allow any weed to, grow near by its vicinity (place) are called smoother crops., e.g., sweet clover, soya bean, alfalfa., , Predator Herbivore, In this, some insects like beetles,, etc., are used to control weeds,, e.g., Cactoblastis cactrorum and, Chrysolina beetles., , Vegetables, Certain weeds, sush as Amaranthus, and Chenopodium can be used as, fodder or vegetable., , Mycoherbicides, Devine and collego are, fungal spores, which are, sprayed over weeds to kill it., , Bioherbicides, , Transgenic Plants, Through the gene transfer, the resulted, genetically engineered plants develop, resistance against pests., , Bioinsecticides, Living organisms and their products used for insect control are called, bioinsecticides. These include pathogens /parasites and predators., Some important bioinsecticide are as follows, (i) Sporeine First commercial bioinsecticide obtained from, Bacillus thruingiensis., (ii) Doom It is the mixture of Bacillus papillae and Bacillus, lentiborbus, which has been used to control Japanese beetles, papillae., (iii) Ladybug (lady bird beetle) and praying mantis can control, scale insect or aphid pests of vegetables, cotton and apple., (iv) Vedalian Beetle (Radiola cardinalis) has been found, effective against cottony cushion scale (Icerya purchasi)., (v) Mycar is a product obtained from the fungus Hirrutella, thompsoni and used to control citrus rust mite., (vi) Predator bug (Cystorhinus mundulus) has been successfully, used to control sugarcane leaf hopper in Hawaii., (vii) Bacillus sphaericus is toxic to larva of Anopheles mosquito., (viii) Boverin is obtained from a fungus Beauveria bassiana and, used for controlling colorado potato beetle (Leptinotarsa, decemlineata) and codling moth., (ix) The fungus Entomophthora ignobilis may be used for, controlling green peach aphid., (x) The fungus Coelomomyces is useful to control mosquito larvae., , www.aiimsneetshortnotes.com
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546, , Telegram @neetquestionpaper, , Handbook of Biology, , Some of the natural insecticides are listed below, Natural Insecticides and Their Sources, Natural insecticides, , Sources, , Rotenones, , Roots of Derris elliptica and, Lonchocarpus, , Nicotine, , From tobacco (Nicotiana tabacum), , Salanin, azadirachtin, meliantiol, , From neem (Azadirachta indica), , Pyrethrin and cineria, , From capitulum of pyrethrum, (Chrysanthemum cinerarifolium,, C. coccineum and C. marashalli), , Ryania, , Roots and stem of Ryania speciosa, , Microbes in Sewage Treatment, (Environmental Microbiology), Municipal waste water is called sewage. It contains large amount of, organic matter and microbes. Treatment of waste water is done by the, heterotrophic microbes which are naturally present in the sewage., The treatment of sewage is carried out in following two stages, , 1. Primary Treatment, In involves the physical removal of large and small particles, from the sewage through filtration and sedimentation., , 2. Secondary or Biological Treatment, The primary effluent is aerated in large tanks. Through this aeration,, the Biological Oxygen Demand (BOD) of water increases (dissolved, oxygen levels got decreased by growing microbes)., , Microbes in Biofuels, Biofuels are fuel of biological origin which are used for the production, of heat and other forms of energy. The energy derived from biofuels is, called bioenergy., The biofuels offer following advantages, (i) These are renewable energy resources., (ii) They release relatively low greenhouse gases including carbon, dioxide emission than fossil fuels., , www.aiimsneetshortnotes.com
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548, , Telegram @neetquestionpaper, , Handbook of Biology, , 33, Biotechnology :, Principles and, Processes, Biotechnology is the scientific technology which uses living organisms, in the systems or processes for the manufacturing of useful, products/services for human beings., The term biotechnology was coined in 1917 by Karl Ereky to, describe a process for large scale production of pigs., , Principles of Biotechnology, Among many, the two core techniques that enabled the birth of modern, biotechnology are, (i) Alternation of constituents of genetic material (DNA or RNA) to, change the phenotype of resultant organisms., (ii) Production of the large number of microbes/eukaryotic cells in, controlled environment to manufacture various products., , Research Areas of Biotechnology, 1. Production of improved organisms or pure enzymes., 2. Creating optimal conditions for a catalyst to act., 3. Technologies to purify proteins, organic compounds, etc., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 549, , Biotechnology : Principles and Processes, , Genetic Engineering or Recombinant, DNA Technology, It is the technology involved in the synthesis of artificial genes, repair, of genes and for manipulation in genes and genomes of any organism., The method of genetic engineering is completed in following stages/steps, (i) Isolation of a particular gene segment or DNA from an, organism., (ii) Introduction of isolated DNA into vector DNA to form rDNA., (iii) Introduction of rDNA into host., (iv) Selection of host progeny in which rDNA is present, (i.e., selection of hybrids)., (v) Formation of multiple copies of these hybrids (i.e., cloning)., For the isolation of particular gene or DNA, specific enzymes, called, endonucleases are used. The obtained fragments may be blunt or, sticky ended., For the transfer of the desired DNA from one organism to other, it, should be added with the microbial vector. As a result of, integration of vector DNA and desired DNA, rDNA is produced. These, rDNAs are formed primarily in vectors., Through vectors, these rDNAs are transferred to host where they, integrate with the host DNA and are copied several times. Among the, total progeny organisms, only some of the organisms cells have rDNA, present in them, called hybrids., After selecting these hybrids, the process of cloning takes place in, which several copies of the same genetic constituents are produced,, called clones. As a result of insertion of these rDNA, the desired, phenotypes/products can be obtained., A large number of products of various categories and applications are, obtained from biotechnological processes. These products are used in, various fields as agriculture therapeutics, textiles, environmental, management, etc., , Gene Cloning, It is the process of producing exact copies (clones) of a particular gene, or DNA sequence using genetic engineering techniques., , www.aiimsneetshortnotes.com
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550, , Telegram @neetquestionpaper, , Handbook of Biology, , Diagrammatic presentation of process of gene cloning is given below, Bacterium, , 1. Vector such as a, plasmid is isolated, , DNA containing, gene of interest, , 2. DNA is cleaved, by an enzyme, into fragments, , 3. Gene is inserted, into plasmid, , Bacterial Plasmid, chromosome, , Recombinant DNA, (plasmid), i.e., plasmid with, gene of interest, , Gene of, interest, 4. Plasmid is taken up by a, cell such as a bacterium, , Recombinant bacterium, , Goal may be to create, OR, copies of gene, , 5. Cells with gene of interest are cloned, Goal may be to create product of gene, , 6. (b)Cells make, a protein, product, , Plasmid, RNA, Protein product, 6. (a) Copies of gene are harvested, , Gene for pest, resistance is, inserted into, plants, , Gene alters bacteria Amylase, cellulase and, for cleaning up, other enzymes prepare, toxic waste, fabrics for clothing, manufacture, , 7. Copies of protein, are harvested, , Human growth, hormone treats, stunted growth, , Basic steps in biotechnology, , Tools of rDNA Technology, 1. Restriction Endonucleases, The most important tools in biotechnology are restriction enzymes., These belong to the large family of enzymes, called nucleases. These, were discovered by Arber in 1962., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 551, , Biotechnology : Principles and Processes, , These enzymes have the ability to recognise the certain nucleotide, sequence and make 4-8 bp long cuts on these sequences. They were, named restriction endonuclease because they have the ability to, restrict phage infection among bacteria. Due to their function,, they are also known as molecular scissors or chemical scalpals., W Arber, H Smith and D Nathans in 1978, were awarded with, Nobel Prize in medicine and physiology for their pioneering work in, the study of restriction endonucleases., The restriction enzymes can be of 3 types, on the basis of their, chemical and physiological properties., The comparative account of these enzymes is given in the following, table, Features, , Type I Enzyme, , Type II Enzyme, , Type III Enzyme, , Protein structure, , Bifunctional enzyme, with 3 subunits, , Separate, endonuclease and, methylase, , Bifunctional enzyme, with 2 subunits, , Recognition site, , Bipartite and, asymmetrical (e.g.,, TGAC and TGCT), , Short sequence, (4-6 bp), often, Palindromic, , Asymmetrical, sequence of 5-7 bp, , Cleavage site, , Non-specific >1000, bp from recognition, site, , Same as or close to, recognition site, , 24-26 bp down, stream of recognition, site, , Restriction and, methylation, , Mutually exclusive, , Separate reactions, , Simultaneous, , ATP needed for, restriction, , Yes, , No, , Yes, , Mg 2+ needed for, restriction, , Yes, , Yes, , Yes, , Commonly used, in, , Random cutting and, fragments making, , Gene manipulation, , Gene cloning, , Note A palindromic sequence is a nucleic acid sequence that is the same whether, read from 5' to 3' end of one strand or 5' to 3' on complementary strand., , www.aiimsneetshortnotes.com
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552, , Telegram @neetquestionpaper, , Handbook of Biology, , As a result of treatment with restriction endonucleases, two types of, DNA fragments are produced., DNA, Restriction, endonucleases, , Sticky Ends/Cohesive Ends, , Blunt Ends/Flush Ends, , (This leaves, single-stranded, unpaired bases at cut ends), , (This leaves both strands, ended at the same point), , 5′, 3′, , GA, , ATTC, , CTTAAG, , 3′, , 5′, , 5′, , 3′, , GT Py Pu AC, CA Pu Py TG, , Eco RI, 3′, , 5′, , 5′, , G, , 3′, , C TT AA 5′, , AATTC, 3′, , G, , 3′, 5′, , Hind II, 3′, 5′, , 5′, 3′, , GT Py, CA Pu, , 3′ 5′, 5′ 3′, , Pu AC, Py TG, , 3′, 5′, , Nomenclature of Restriction Endonucleases, The name of the enzyme is derived from the name of organism from, which it is isolated., (i) The first letter of the genus becomes the first letter of the name, (written in capital letter)., (ii) First two letters of the species make second and third letter of, the enzyme (written in small letters)., (iii) All these three letters are written in italics., (iv) The fourth letter of the name of enzyme is the first letter of, strain (written in capital letter)., (v) The Roman number written at the end of the name indicates the, order of discovery of enzyme from that strain., , 2. Exonucleases, These enzymes remove nucleotides from the terminal ends (either, 5′ or 3′ ) of DNA in one strand of duplex., , 3. Lysing Enzymes, These enzymes are used for the isolation of DNA from cells,, e.g., lysozyme is used to digest the bacterial cell wall for the extraction, of cellular DNA. Protease, lipase and other degrading enzymes come in, this category., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 553, , Biotechnology : Principles and Processes, 4. Synthesising Enzymes, , With the help of these enzymes, the synthesis of DNA takes place on, the suitable templates. They are of two types, Synthesising Enzymes, , Reverse Transcriptase, , DNA Polymerase, , Synthesis of complementary DNA, takes place on RNA template., , Synthesis of DNA takes, place on DNA template itself., , This enzyme helps in in vitro synthesis of complementary DNA (cDNA), strand on DNA templates., , 5. DNA Ligase/Sealing Enzyme/Joining Enzyme, These enzymes help in sealing the gaps in DNA fragments, which are, joined by complementary base pairing. They act as molecular glue,, join DNA fragments by forming phosphodiester bonds, e.g.,, T4-ligase of bacteriophage. It can join both cohesive and blunt ended, fragments, hence useful in DNA cloning. The ligase of E. coli is, ineffective to join blunt end DNA, hence, it is not used in gene cloning., , 6. Alkaline Phosphatase, This enzyme phosphate group from the 5′ end of a DNA and thus, modify the terminal of DNA., Alkaline, Phosphatase, , 5′ GOH 3′, 3′ C p Tp Tp A p A p 5′, , →, , 5′ GOH 3′, 3′ C p Tp Tp A p A OH 5′, , After the treatment of alkaline phosphatase to the DNA, both, recircularisation and plasmid dimer formation can be prevented, as DNA ligase cannot join the ends., , 7. S1 - Nuclease, This enzyme converts cohesive ends of the duplex DNA to blunt or, flush ends by trimming away the single strand., , 8. Linkers and Adapters, l, , l, , Linkers are single-stranded, synthetic oligonucleotides which self, associate to form symmetrical double-stranded molecule containing, the recognition sequence for a restriction enzyme., Adaptor molecules are chemically synthesised DNA molecules., They are used in 5′ hydroxyl form to prevent self-polymerisation., , www.aiimsneetshortnotes.com
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554, , Telegram @neetquestionpaper, , Handbook of Biology, , 9. Vectors (Vehicle DNA), It is defined as a DNA molecule that can be used to carry a DNA, segment (gene) to be cloned., Types of vectors are, (i) Plasmid Vector, Plasmids are double-stranded, closed circular DNA molecules, which exist in the cell as extrachromosomal units. They are, self-replicating and found in bacterial species., There, (a), (b), (c), , are three general classes of plasmids, Virulence plasmids Encode toxic genes., Drug resistant plasmids Provide resistance., Conjugation related plasmids Encode genes for bacterial, conjugation., , It was discovered by William Hayes and Joshua Lederberg in 1952., Plasmids range in size from 1-200kb and depend on the host protein, for their maintenance and replication function., (ii) Bacteriophage, Plasmid vectors normally used to clone DNA segments of small size,, i.e., up to 10 kb. However, when the size of gene of interest is more, than 10 kb, vectors based on bacteriophage are used, e.g., M13,, λ (lambda) phage, etc., (iii) Cosmid Vector, Cosmids are formed by the combination of plasmids and ‘cos’ sites of, phage lambda (λ). It has the capacity to transfer the DNA of up to, 45 kbp. This vector can be packaged into λ-phage. This is more, efficient than plasmid transformation., A typical plasmid vector contains, (a) A plasmid origin of replication, (b) Selectable markers, (c) Suitable restriction enzyme sites., (d) Lambda (λ) ‘cos’ site., (iv) Phagemid Vectors, It is a composite structure made up of bacteriophage and plasmids., These have the capacity to carry larger DNA molecules., (v) Shuttle Vectors, Plasmid vectors can replicate only in E. coli. The cloning vectors which, can propagate in two different hosts are called shuttle vectors., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 555, , Biotechnology : Principles and Processes, (vi) Ti plasmid, , These are found in Agrobacterium tumefaciens, bacteria infecting dicot, plants. The part of Ti plasmid transferred in the plant cell DNA is, T-DNA., (vii) Artificial Cloning Vectors, These vectors are artificially constructed., Following are some artificial cloning vectors, (a) pBR 322 vector This was the first artificial cloning vector, constructed in 1977 by Boliver and Rodriguez., It possesses following characteristics, l, Size 4.36 kb (double stranded cloning vector), l, Contains two antibiotic resistant genes, Ampicillin resistance ( ampR ), Tetracycline resistance ( tet R ), It contains 20 unique recognition sites for restriction, endonucleases., Cla I, , Hind III, , Eco RI, , Bam HI, , Pvu I, Pst I, Ampicillin, resistance, (ampR) gene, , Sal I, , pBR322, 4363bp, , Tetracycline, resistance, (tet R ) gene, , rop, Pvu II, Origin of, replication (ori), , Diagram showing essential features of plasmid pBR 322, , (b) Bacterial Artificial Chromosome (BAC) This vector is based, on f-factor of E. coli. It can accommodate up to 300-350 kbp of, foreign DNA and it can also be used in genome sequencing, projects. It contains genes for replication and maintenance, of F-factor., (c) Yeast Artificial Chromosomes (YAC) These vectors contain, telomeric sequences, the centromere and the autonomously, replicating sequence from yeast chromosomes. It is used to, clone the DNA fragments of 500 kb in size., , www.aiimsneetshortnotes.com
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556, , Telegram @neetquestionpaper, , Handbook of Biology, , (viii) Transposons as Vectors, These are the DNA sequences which can change their location in the, genome and hence, known as mobile DNA or transposons. The, activator (Ac) and dissociation (Ds) elements are the popular, transposable controlling elements of maize which are also called Ac-Ds, elements. The transposons of Drosophila are known as P-elements., They can be used as vectors., Characteristics of a Cloning Vector, The following features are essential to facilitate cloning into a vector, (i) A vector should contain a replicon that enables replication in, the host cells., (ii) It should have several marker genes., (iii) It should have a unique cleavage site within one of the marker gene., (iv) For the expression of cloned DNA, the vector DNA should, contain suitable control elements such, as promoter,, terminators and ribosome binding sites., , Processes of Genetic Engineering/rDNA Technology, Genetic engineering is a complex process which can be studied in, following steps, , 1. Isolation of Genetic Material, This can be achieved by treating the bacterial cells/plant/animal tissues, with enzymes such as lysozyme (bacterial), cellulase (plant cells) and, chitinase (fungus), etc., The complete schematic representation of the process is as follows, Living cell/Tissue, , Lysozymes,, cellulase,, chitinase, , Free DNA, Ribonuclease, with other, macromolecules, (i.e., RNA, proteins, etc), , RNA, , DNA with, proteins, etc, Protease, Purified DNA, (In the form of, thread suspension), , Protein, , Chilled, ethanol, , Separated DNA, Polysaccharide, and lipid, , Method to isolate DNA, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 557, , Biotechnology : Principles and Processes, , In order to cut the DNA with restriction enzyme, it should be in pure, form., , 2. Cutting of DNA at Specific Location, The purified DNA fragments are treated with restriction enzyme at, optimal conditions of that enzyme. After certain period, agarose gel, electrophoresis is employed to check the progression of restriction, enzyme digestion and separation of DNA fragments., , Gel Electrophoresis, Electrophoresis is a technique of separation of charged molecules like DNA under the, influence of an electric field so that, they (DNA) migrate in the direction of positive, electrode (anode) through a medium/matrix., DNA, bands, , Wells, , Smallest, , 1, , 2, , 3, , 4, , Largest, , A garose gel, , A typical gel electrophoresis showing undigested and, digested DNA fragments., , The smaller fragments of DNA settle down fast towards the anode while the larger, DNA fragments which remain undigested appear at the topmost region of the, agarose gel column., , 3. Amplification/Copying of Gene of Interest Using PCR, Polymerase Chain Reaction (PCR) is a technique of synthesising multiple, copies of the desired gene (or DNA) in vitro. This was developed by, Kary Mullis in 1985., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 558, , Handbook of Biology, , The procedure of this reaction is as follows, Sample DNA 5′, , 3′, , Double Helix 3′, , 5′, , 14243, Segment to be Amplified, Denaturation, (90-98°C), , 5′, Single, Stranded, 3′, DNA, , Primers 1, , 3′, 5′, 2, , Annealing, (40-60°C), , 5′, , 3′, , 2, , Primers, Annealed, , Annealing of Oligonucleotide, Primers on both the strands to, start DNA copying, primer is, of RNA nature. (40-60°C), , Primers, 1, , 3′, , 5′, , Taq DNA, Synthesis, Polymerase (70-75°C), 5′, , 2, , Desired, Segment, 3′, Copied, , 1, Denaturation, , 123, , Old, Strands, , Denaturation is the process of, opening of two DNA strands, around desired DNA sequence., (90-98°C)., , 5′, 3′, , 123, , New Strands 3′, 5′, , 5′, 3′, Annealing, , 3′, 5′, Cycle I Complete, Cycle II Begins, 3′ 4 copies of, desired, 5′, segment, , Taq DNA Polymerase,, Extension of DNA fragment, by Using heat stable DNA, polymerase leads to the, synthesis of DNA, complementary to desired, DNA. (70-75°C)., Denaturation of Newly, Synthesised DNA It takes, place at high temperature, (90-98°C). After this the coiling, of both old and new strands, takes place., , Primers anneal to, all 4 and copy them., , Continued, , PCR Technique, , 4. Ligation of DNA Fragment into Vector DNA to form rDNA, After the isolation of target DNA fragment, DNA ligase can be used to, join it to a vector digested by the same restriction endonuclease, e.g., a, fragment generated by Eco RI only joins with the cloning vector, digested by Eco RI, and not with the cloning vector generated by Bam, HI., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 559, , Biotechnology : Principles and Processes, The complete process looks like, Cloning vector, (plasmid), , Eukaryotic chromosome, (containing gene of, interest), , 1. Cloning vector, is cleaved with, restriction, endonuclease, (e.g. Eco RI), , 2. DNA fragment of interest, is obtained by cleaving, chromosome with a, restriction endonuclease, (e.g. Eco RI), 3. Fragments are ligated, to prepared cloning, vector, DNA ligase, Recombinant vector, , The process of formation of rDNA, , 5. Insertion of rDNA into Host Cells/Organisms, The rDNA can be inserted into the host cell through various methods., Broadly these can be categorised into, (a) Vector-mediated gene transfer, (b) Vectorless gene transfer, , www.aiimsneetshortnotes.com
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560, , Telegram @neetquestionpaper, , Handbook of Biology, , Gene transfer, Vector-Mediated, Gene Transfer, , Vectorless, Gene Transfer, , Virus-Mediated, , Agrobacterium, Mediated, This is the first, successful gene transfer, method. Various species of, Agrobacterium are used to, provide natural gene transfer, and expression in plant systems,, e.g., A. rhizogenes,, A. radiobactor, , As many viral infections are systemic, hence virus can be used to, transfer desired genes to host., Caulimovirus, Gemini virus, and some other RNA viruse, are used to transfer the genes., , Physical Gene Transfer, Methods., • Electroporation Here high electrical, , Chemical Gene Transfer, Methods PEG, , • (Poly Ethylene Glycol-mediated, transfer) The first integration of, impulses (1-1.5 kV) are used to insert the, isolated Ti-plasmid DNA into, rDNA into host., plant protoplast was, • Particle Bombardment/Biolistics, reported in the Petunia and, In this, the rDNA coated on gold or tungsten, tobacco in the presence of PEG., is fired on host through gene gun., The 40% solution of PEG creates, • Microinjection, small pores in the plasma, It is the direct mechanical introduction of, membrane which helps in the, rDNA into the target cell., integration of linear DNA on, • Liposome-Mediated Transformation, random sites into host DNA., Artificial lipid vesicles are used to transfer, • Calcium Phosphate, rDNA to host., Coprecipitation, • Silicon Carbide FibreIn this, the DNA CaPO4 complex, Mediated Transformation, is added to dividing cells to, The fibres of 10-80 µm, transfer rDNA., length are used to deliver, • Polycation, DMSO Technique, rDNA into target cells., it involves use of polycation, • Ultrasound-Mediated Transformation, to increase adsorption, An acoustic intensity of 0.5 W/cm2, of DNA by host cell., for 30 mins. is sufficient to take, • DEAE Dextran Procedure, foreign rDNA by protoplast., Here rDNA is complexed with, • Pollen-Mediated Transformation, diethyl amino ethyl to inject it into, The introduction of rDNA into gametes, the host. This method does, can occur through this method., not produce stable transformants., , 6. Selection/Screening of Hybrids, The selection of hybrids with rDNA can be made by the treatment of, antibiotics (the resistant gene of antibiotic is already inserted in, rDNA). All the hybrids will die which do not contain rDNA and only, recombinant hybrids will be reported in the resultant solution., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 561, , Biotechnology : Principles and Processes, , Bioreactors (Fermenters), These are the vessels in which raw materials are biologically converted, into specific products by microbes, plant and animal cells in a, controlled way., Following figure will give the idea about the structure and operation of, a typical bioreactor, Antifoam, , Motor, , Steam, , Acid/base, , Pressure guage, , Nutrient or Inoculant, This is used to, add inoculum, (GMOs) or, nutrient to the, Sterile nutrient, medium, medium, , Filtered, waste gases, Cold-water outlet, , Impeller, It helps in proper, mixing of nutrient Oxygen, and inoculum, concentration, probe, , pH probe, It indicates the, pH of inoculum, Temperature probe, It may be the biosensor, or thermometer which, indicates the change in, temperature, , Cooling jacket, It reduces the heat,, generated during, growth, Cold-water, inlet, , Sparger, It sprinkles the air, bubbles into inoculum, Compressed air, , Steam, Harvest pipe, The products are collected, through this outlet, , A typical bioreactor, , Downstream Processing, It is the process of separation and purification to make a, biotechnological product ready for marketing., After the purification, the product is mixed with certain preservative, and taken for comprehensive trials on target individuals., Before releasing into the market, every product has to take the, approval by Genetic Engineering Approval Committee (GEAC)., , www.aiimsneetshortnotes.com
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562, , Telegram @neetquestionpaper, , Handbook of Biology, , 34, Biotechnology and, Its Applications, Biotechnology is the application of biological system in technology that, can only be achieved through the integration of biological, physical and, engineering sciences. Biotechnology has tremendous applications in, certain areas like healthcare, agriculture, industries, etc., , Types of Biotechnology, On the basis of its applications, biotechnology is of following types, (i) Red biotechnology It is medical biotechnology, applied in designing, organisms used to produce antibiotics or genetic cure products through, genomic manipulation., (ii) White biotechnology It is the industrial use of biotechnology., (iii) Green biotechnology It is the agricultural use of biotechnology., (iv) Grey biotechnology It includes all those applications of, biotechnology that are directly related to the environment., (v) Blue biotechnology It is based on the exploitation of sea, resources to create products and application of industrial interest., , Applications of Biotechnology in Crop Improvement, There, 1., 2., 3., , are mainly three benefits of biotechnology to agriculture, Reduction of the duration of breeding period., New methods of hybridisation., Application of rDNA technology in agriculture., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biotechnology and Its Applications, 563, Transgenic Crops or GM Crops, It is a crop which contains and expresses a transgene. A more popular, term for transgenic crops is Genetically Modified crops or GM, crops., The genetic modification may lead to following changes in crops, Enhanced nutritional value, Vitamin-A enriched rice, (i.e., Golden rice)., , More tolerance towards, , GM, Crops, , Abiotic stresses Cold, drought,, salt and heat resistant plants., , Reduced post harvest loss, , Reduced reliance on chemical pesticides, , ‘Flavr Savr’ tomato with delayed ripening, , Insects and pest resistant plants., , After its integration into host DNA, transgene can perform one of the, following functions, (i) Produces a protein of interest The gene which produces, the protein of our interest is inserted into other organism., e.g., hirudin, a protein that prevents blood clotting. The gene, producing hirudin is inserted into the plant Brassica napus, where the hirudin is synthesised and stored in seeds., (ii) Produces a desired phenotype It produces a protein that,, on its own produces the desired phenotype, e.g., crystal (cry), protein produced by Bacillus thuringiensis (Bt) in plants is toxic, to the larvae of certain insects., (iii) Modifies an existing biosynthetic pathway By this, modification, a new end product is obtained. e.g., transgenic rice, and transgenic potatoes produce higher content of vitamin-A, and protein, respectively., (iv) It masks the expression of native gene A protein, expression masks the existing native gene. e.g., in the tomato, variety ‘Flavr Savr’, the function of the gene producing, polygalacturonase (pectin degrading enzyme) is blocked which, results in the delayed ripening and better nutrient quality., Examples of GM crops are, 1. Bt cotton Pest resistant, herbicide tolerant and high yielding, plant. It is also resistant to bollworm infestations., 2. Golden rice Vitamin-A rich rice., 3. Potato With higher protein content., 4. Corn, brinjal Insect resistance., 5. Soybean, maize Herbicide resistance., , www.aiimsneetshortnotes.com
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564, , Telegram @neetquestionpaper, , Handbook of Biology, , Genetically Modified Organisms ( GMOs), The GMOs have various modifications in their metabolism and may, have altered phenotypes., Following table describes the detailed information about several GMOs, Some Genetically Modified Organisms, Organism, , Modification, , Long life tomatoes, , There are two well-known projects, both affecting the gene for, the enzyme polygalacturonase (PG), a pectinase that softens, fruits as they ripen. Tomatoes that make less PG, ripen more, slowly and retain more flavour., The American ‘Flavr Savr’ tomato used antisense technology to, silence the gene, while the British Zeneca tomato disrupted the, gene. Both were successful and were on sale for a few years,, but neither is produced any more., , Insect-resistant crops, , Genes for various powerful protein toxins have been transferred, from the bacterium Bacillus thuringiensis to crop plants, including maize, rice and potatoes., These Bt toxins are thousands times more powerful than, chemical insecticides, and since they are built-in to the crops,, insecticide spraying (which is non-specific and damages the, environment) is not necessary., , Virus-resistant crops, , Gene for virus coat protein has been cloned and inserted into, tobacco, potato and tomato plants., The coat protein seems to ‘immunise’ the plants which are, much more resistant to viral attack., , Herbicide-resistant, crops, , The gene for resistance to the herbicide basta has been, transferred from Streptomyces bacteria to tomato, potato, corn, and wheat plants making them resistant to basta., Fields can safely be sprayed with this herbicide, which will kill, all weeds, but not the crops., , Pest-resistant, legumes, , The gene for an enzyme that synthesises a chemical toxic to, weevils has been transferred from Bacillus bacteria to the, Rhizobium bacteria that live in the root nodules of legume, plants. These root nodules are now resistant to attack by weevils., , Nitrogen-fixing crops, , This is a huge project, which aims to transfer about 15 or more, genes required for nitrogen-fixation from the nitrogen-fixing, bacteria Rhizobium into cereals and other crop plants., These crops would then be able to fix their own atmospheric, nitrogen and will not need any fertiliser. However, the process is, extremely complex., , Crop improvement, , Proteins in some crop plants, including wheat, are often, deficient in essential amino acids (that’s why vegetarians have to, watch their diet so carefully). So the protein genes are being, altered to improve their composition for human consumption., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biotechnology and Its Applications, 565, Organism, , Modification, , Mastitis-resistant, cattle, , Tick-resistant sheep, , Fast-growing sheep, , The gene for the enzyme lactoferrin, which helps to resist the, infection that causes the udder disease mastitis, has been, introduced to Herman-the first transgenic bull., Herman’s offsprings inherit this gene and do not get mastitis, hence, produce more milk., The gene for the enzyme chitinase, which kills ticks by digesting, their exoskeleton has been transferred from plants to sheep., These sheep are immune to tick parasites and do not need, sheep dip., The human growth hormone gene has been transferred to, sheep, so that they produce human growth hormone and grow, more quickly. However, they are more prone to infection and, the females are infertile., , A number of fish species, including salmon, trout and carp,, have been given a gene from another fish (the ocean pout), which activates the fish’s own growth hormone gene so that,, they grow larger and more quickly., Salmon grows to 30 times their normal mass at 10 times more, than the normal rate., Environment cleaning Genes for enzymes that digest many different hydrocarbons, found in crude oil have been transferred to Pseudomonas, microbes, bacteria so that they can clean up oil spills., Fast-growing fish, , Bt Cotton (Insect Resistant Cotton), The bacterium Bacillus thuringiensis (Bt) naturally produce chemicals, which are harmful to certain insects (e.g., larvae of moths, cotton, bollworm and flies) and are harmless to other forms of life., The Bt cotton variety, contains a foreign gene obtained from Bacillus, thuringiensis. This gene protects the plants from bollworm by, producing Bt toxin. This Bt toxin does not kill the Bacillus because it, exists as inactive protoxin in its body. Once an insect ingests the, inactive toxin, it gets exposed to the alkaline pH of the gut, which, solubilises the crystals and converts it into active form. The activated, toxin binds to the surface of midgut epithelial cells and creates pores, that cause cell swelling and lysis and eventually causes death of the, insect., Farmers who grew Bt variety, obtained 25-75% more cotton than, those who grew the normal variety. The inserted foreign genes are, cryI Ac and cry IIAb (control the bollworm) and cry IAb (controls the, corn borer)., , www.aiimsneetshortnotes.com
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566, , Telegram @neetquestionpaper, , Handbook of Biology, , There are two methods to introduce cry genes into target cells, Agrobacterium, mediated gene, transfer, , Gene gun, mediated gene, transfer, , Foreign Genes, (e.g., cry gene), Gene inserted, into Ti plasmids, , Gene replication, , Gold particles coated, with DNA, , Bacterium mixed, with plant cells., , Cell shot with gene gun, and DNA incorporated into, plant cell chromosome, , Plasmid moves into plant, cells and inserted DNA, into plant chromosome, , Transgenic plant is generated, from transformed cell, , Cells screened, for transgene, , Generation of Bt cotton, , Applications of Biotechnology, in Plant Tissue Culture, Plant tissue culture is a novel and innovative technique to grow high, quality, disease-free plants quickly and in a large quantity by culturing, various plant parts. This method is used mostly when the planting, material is in scarce amount., Following are the methods used in plant tissue culture, , 1. Meristem Culture, It is the method of cultivation of axillary or apical shoot meristem. It involves, the development of an already existing shoot meristem and subsequently the, regeneration of adventitious roots from the developed shoot., The process of meristem culture is shown in the following flow chart, Explant, from Shoot, Apical Meristem, (SAM), , A complete, plant, , Shoots transferred, to the medium, for rooting, , Culture in a, medium, containing, cytokinin, , Shoots of, 2-3 cms are, excised, , Obtaining, plantlets, , Hardening, of, plantlets, , Explant have, multiple axillary, branches (i.e., shoots), Field, plantation, , Steps in meristem culture, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 567, Biotechnology and Its Applications, Meristem culture is used for, , Rapid clonal, multiplication, , Production of, virus-free plants, , Germplasm, conservation, , Production of, transgenic plants, , 2. Embryo Culture, In this method, the embryos removed from the developing seeds are, placed on a suitable medium to obtain seedlings., Embryo culture can be applied for, Recovery of interspecific hybrids., Propagation of orchids., Overcoming dormancy., Anther culture and haploid production., l, , l, , l, , l, , Embryo-nurse Endosperm Technique, The embryos from mature seeds are cultured in vitro on developing endosperm., The fresh endosperm is the primary requirement of the developing embryo., , 3. Protoplast Culture and Somatic Hybridisation, The production of hybrid plants through the fusion of protoplasts of, two different plant species is called somatic hybridisation and the, produced hybrids are known as somatic hybrids or cybrids., Protoplast, also known as naked plant cell refers to all the, components of a plant cell excluding the cell wall., The technique of somatic hybridisation has following four steps, Isolation of protoplasts, Fusion of the protoplasts, Selection of hybrid cells, Culture of hybrid cells (regeneration of hybrid plants)., l, , l, , l, , l, , www.aiimsneetshortnotes.com
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568, , Telegram @neetquestionpaper, , Handbook of Biology, , Sterilised leaf or other, soft parts of plant, , ), 60, 19, g,, in, ic ock all ., at, m (C ll w e, zy se ce zym, En llula of en 8)., e ture ing 96, • C ix rad e, 1, M, • deg ab, k, (Ta, , • Me, Th c, tis e d han, pl sue iss ica, as, e, m aft ctio l, ol er, n, ys, of, at, io, n, , The diagrammatic representation of the process of somatic hybridisation, is as follows, , Protoplast, , Protoplast, , (A) + (B) Protoplast of other, variety or species, Fusion of Protoplasts, Hybrid cells, (with nucleus and cytoplasm, of both fusion parents), , Asymmetric, hybrids, have full somatic, complement of one, fusion parent and, unequal no. of, chromosomes from, other fusion parent., , Symmetric, hybrids, contain somatic, chromosomes complement, of both the fusion parents, and equal nuclear, components of both, fusion parents., , Cybrid-1, contains nucleus of, protoplast-A and, cytoplasm of both, the fusion parents., , Cybrid-2, contains the, nucleus of, protoplast-B and, cytoplasm of both, the fusion parent., , Somatic hybrids have following uses, Used for gene transfer and transfer of cytoplasm., Used in the production of useful polyploids., In the development of new crop plants, e.g., pomato (hybrid of potato, and tomato), rabbage (hybrid of radish and cabbage), etc., l, , l, , l, , Applications of Biotechnology in Medicine, With the help of following services, biotechnology imposes immense, impact on healthcare sector. It helps in, (i) Enabling mass production of safe and more effective therapeutic, drugs., (ii) The early diagnosis of diseases for their effective treatment., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biotechnology and Its Applications, 569, The biotechnological applications can be categorised into two groups, 1. Gene products, 2. Gene therapy, , 1. Gene Products, Description of some genetically engineered products is as follows, (i) Human insulin (humulin) The pancreas produces insulin in, humans to regulate the blood sugar concentration. In the absence, of enough insulin, the patient develops wasting symptoms and, eventually dies., Humulin is synthesised for the management of adult-onset, diabetes. In 1983, an American company Eli Lily produced, first genetically engineered insulin by synthesising two DNA, sequences corresponding to A and B chains of insulin., This DNA fuses with the plasmid of E. coli where both the, chains are produced separately. These chains are joined by, disulphide bonds and humulin is produced., (ii) Human Growth Hormone (hGH) The hGH gene is cloned, into E. coli, which helps in the treatment of dwarfism in, humans. This is synthesised by adding a single sequence which, causes the gene to be translated and secreted from the cell., (iii) Tissue Plasminogen Activator (TPA) A clot dissolving, protein can now be produced by recombinant mammalian cells., (iv) Interferon It is an antiviral protein produced by E. coli and, used to fight certain cancers and skin diseases., (v) α-1 Antitrypsin (AAT) The AAT protein inhibits protease, enzymes like trypsin and elastase. Because of mutation (base, substitution), the AAT fails to inhibit elastase hence, elastase, digests the elastic tissues of alveoli and causes emphysema., AAT is now produced in GM sheep where the gene for AAT is, coupled with milk producing gene. The AAT is purified from the, milk of GM sheep (i. e. , Tracy)., (vi) Vaccines These represent another application of rDNA, technology. The hepatitis-B vaccine (now in use) is composed of, viral particles manufactured by yeast cells and recombined with, viral genes., , www.aiimsneetshortnotes.com
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570, , Telegram @neetquestionpaper, , Handbook of Biology, , (vii) Antibiotics These are produced by fungi such as Penicillium, and Cephalosporium etc., to treat infections caused by bacteria, and certain other parasites., (viii) Biochips These are single-stranded DNA chains or repeated, DNA segments which firmly struck to silica (glass chips) for, matching and studying DNA components of unknown, composition., , 2. Gene Therapy, It is the technique of genetic engineering in which we replace a, faulty gene by a normal healthy functional gene. This therapy, has been tried for sickle-cell anaemia and Severe Combined, Immunodeficiency Disesae (SCID)., The first clinical gene therapy was performed on a 4-year-old girl with, Adenosine Deaminase (ADA) deficiency in 1990., Gene therapy can be visualised in following flow chart, A functional gene, (cDNA), Lymphocytes extracted, from the bone marrow, of patient, , Grown in culture, medium, Lymphocytes with cDNA, , Inserted in, retrovirus, , Retrovirus, injects cDNA, into lymphocytes, , Lymphocytes reinjected, into patient, periodically, , Schematic representation of gene therapy, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biotechnology and Its Applications, 571, Cystic Fibrosis, It is the most common genetic disease caused by the mutation in the, gene for protein called CFTR (Cystic Fibrosis Transmembrane, Regulator)., The gene for CFTR was identified in 1989 and soon after that a cDNA, clone was made. This cDNA cloned gene is delivered to epithelial cells, of the lungs, where they get incorporated into nuclear DNA and make, functional CFTR chloride channels., , Stem Cell Technology, It is rapidly developing field for the treatment of a variety of malignant, and non-malignant diseases by using stem cells., Stem cells are present in multicellular organisms that can divide, through mitotic division and differentiate into specialised cells. These, are of two types, (i) Embryonic stem cells These cells can differentiate into all the, specialised cells, called pleuripotent cells. These regenerate, blood, skin or intestinal tissues., (ii) Adult stem cells In adult organisms, stem cell and progenitor, cell act as a repair system for the body., The potential applications of stem cell include organ and tissue, regeneration, brain disease treatment, cell deficiency therapy,, cardiovascular disease treatment., , Molecular Diagnostics, It includes all the tests and methods to identify a disease analysing, DNA or RNA of an organism, e.g., rDNA technology, PCR, ELISA etc., ELISA (Enzyme Linked Immunosorbent Assay) It uses an enzyme, conjugated to an antibody for the detection of specific antigen/antibody, based on antigen-antibody interaction., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 572, , Handbook of Biology, , Applications of Biotechnology in Industries, The industrial applications of biotechnology can be explained by the, following presentation, Enzymes, Various enzymes are produced at, industrial level such as amylase, used in, brewing, baking and textile industry., Other enzyme is protease, which is used, in meat, leather and detergent, industries., , Miscellaneous, Amino acids, nucleotides, vitamins, and organic acids are also, produced by the microbial action., Lysine (used to treat Herpes, simplex infection) is a product of the, bacterium Corynebacterium, glutamicum. Viatmin-B12 and B2, are produced by bacterium and, mould respectively. Xanthan (used, to stabilise and thicken food is, produced by Xanthomonas., , Other Food Items, A food product, sauerkraut (sour, cabbage) is produced by the, microbial action of Leuconostoc and, Lactobacillus bacteria. Some, microbes are also used in pickles., , Mining, Microorganisms are highly, important to leach low grade, ores, to extract their valuable, metals. For example, copper, and uranium can be extracted, by Trichobacillus., , Biotechnology, in Industry, , Bakery Industry, , Beverages Wine, It is the aged product of alcoholic, fermentation of fruits. The crushed fruit, is combined with the Saccharomyces., Fermentation takes several days and, produces alcoholic product called wine., The beer is produced by soaking grains, with Saccharomyces. The other beverages, are vodka, whisky, rum, sake, etc., , It this, the flour, water, salt and, yeast are used to make the dough., Saccharomyces cerevisiae is, used to ferment carbohydrate, present in the dough and, produces CO2, which creates the, soft texture of bread., , Dairy industry, , Cheese, , Buttermilk, , Yogurt, , The protein portion, of the milk, casein, is used to produce, cheese and, cheese products., The protein curd, which is, precipitated from, milk is an, unripened, cheese, , The dairy product, that results from, the souring of low, fat milk by lactic, acid. The flavour, is due to, substance such, as diacetyl and, acetaldehyde., It is produced by, Streptococcus,, Leuconostoc and, Lactobacillus,, , It is a fermented, milk product with, pudding-like, consistency. It is, produced by, Streptococcus, thermophilus, and, Lactobacillus, bulgaricus., , Cheese Product, Soft cheese, Such as camembert is a product, of growth of the fungus, Penicillium camemberti., Hard cheese, Have less water and ripened by, bacteria or fungi., Swiss cheese, It is ripened by various bacteria, such as Propionibacterium, which produce gas holes in the, cheese., Blue cheese It is produced by, Penicillium roqueforti which, produces veins in the cheese., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 573, Biotechnology and Its Applications, Applications of Biotechnology in Environment, Biotechnology has tremendous potential for unique, efficient,, eco-friendly and economically viable options for waste treatment and, degradation of hazardous waste into relatively less harmful products., Following biotechnological products help in the protection of, environment., (i) Biosurfactants These are surface active substances, synthesised by several microorganisms like bacteria and yeast., These have the property to reduce surface tension, stabilise, emulsions and promote foaming., Biosurfactants have the potential to solubilise hydrocarbon, contaminants and increase their availability for microbial, degradation. In some bacterial species such as Pseudomonas, neruginosa, biosurfactants are also involved in a group motility, behaviour called swarming motility., (ii) Superbug It is a modified strain of oil eating bacteria which, was developed by Prof. Anand Mohan Chakraborty. The, process of working through which GMOs cleanup several, environmental contaminants is known as bioremediation. A, more general approach to cleanup oil spills is by the addition of, fertilisers to facilitate the decomposition of crude oil by bacteria., (iii) Mycofiltration It is the process of using fungal mycelia to filtre, the toxic waste., (iv) Phytoremediation It refers to the natural ability of certain, plants called hyperaccumulators to bioaccumulate, degrade, or render harmless contaminants in soil water or air, e.g.,, mustard plants, pigweeds, etc., (v) Biosensors These are referred to engineered organisms, (usually a bacterium) that are capable of reporting some, environmental phenomena like presence of heavy metals or, toxins., (vi) Biofuels There are a wide range of fuels, which are in someway, derived from biomass. Biofuels are gaining increased public and, scientific attention driven by factors such as high fuel prices,, need for increased energy security and concern over greenhouse, gas emission from fossil fuels., , www.aiimsneetshortnotes.com
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574, , Telegram @neetquestionpaper, , Handbook of Biology, , These fuels can be categorised as, Biofuel, , Secondary, , Primary, Firewood, wood chips,, pellets, animal waste., crop residues, landfill, gases, etc., , 1st generation, Made from sugar., starch and vegetable, oil. e.g., bioalcohol,, biodiesel, green, diesel, etc., , 2nd generation, , 3rd generation, , Made from non-food, crops. e.g., biogas,, syngas, etc., , Made from, algae. e.g., bioethanol,, hydrogen fuel., , Ethical Issues in Biotechnology, The manipulation of living organisms by the human race needs some, regulation on both ethical and moral grounds as genetic modification, of organisms can have unpredictable results when such organisms are, introduced into the ecosystem., (i) Biopatent A patent is the right granted by the government, to, an inventor to prevent others to make commercial use of one’s, invention. The patents granted for biological entities and, products derived from them are called as biopatents., (ii) Biopiracy is the term used to refer the use of bioresources by, companies and other organisations without proper, authorisation from the countries and people concerned without, compensatory payment., (iii) Biowar The war, which is fought with the help of biological, weapons against humans, their crops and animals is called a, biowar. In biowar, viruses, bacteria and some other harmful, organisms are used and are called as bioweapons in biowar., (iv) Bioethics It is a branch of ethics, philosophy and social, commentary that deals with the biological sciences and their, potential impact on society., Biotechnology provides several products of high utility values., Major part of applied biotechnology still remains unexplored, which surely will provide the solution to various problems, related to humans and their environment., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 35, Organisms and, Population, An isolated, biological entity (e.g., unicellular or multicellular) which is, able to perform biological processes independently called as organism., Individual organism is the basic unit of ecological hierarchy., , Organism and its Environment, Organism’s life exists not just in a few favourable habitats, but even in, extreme and harsh conditions, e.g., desert, rainforests, deep ocean and, other unique habitats., The suitability of environment directly affects the growth of residing, population and manifests in the form of various biological communities., , Components of Environment, The surface of the earth consists of three elements, i.e., land, sea and, air. On the basis of three elements, it is divided into hydrosphere, (water), lithosphere (land), atmosphere (air) and pedosphere (composed, of disintegrating compounds of rock and stone forming soil)., , Biomes, A large regional unit characterised by a major vegetation type and, associated fauna found in a specific climatic zone is referred to as, biome., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 576, , Handbook of Biology, Deserts, , Grasslands, , Mean annual temperature (°C), , Temperature 20-30°C with, increasing rain precipitation, up to 75-80 cm, the species, richness and productivity, increases with high biomass., , Lack of water, temperature is, very high/very low, less, precipitation, arid climate, leads to sparse population, with desert adapted feature, like spine, etc., , Tropical Forest, Most suitable combination of, temperature (20-30°C) and, precipitation (150-430 cm), leads to well-adapted community, with evergreen plants and animals., , 30, 25, 20, 15, 10, 5, 0, –5, , –10, –15, , 50, , 100 150 200 250 300 350 400 450, Mean annual precipitation (cm), , Arctic and Alpine Tundra, Very low temperature and, precipitation, therefore very low, biodiversity is present at high, latitudes in Northern hemisphere., , Coniferous Forest, Low temperature and high, precipitation result into marshy, floors in forest because of high, humus deposition, which, supports high biodiversity., , Temperate Forest, Moderate temperature and, precipitation, therefore, soft woody and hard woody, plants and all types of, animals are present., , Different types of biomes of the world, , Habitat and Microhabitat, The natural abode of air organism including its total environment is, called its habitat., Microhabitat is a small part of a habitat with its own characteristic, environmental features, e.g., forest floors, tree canopies, etc., , Niche/Ecological Niche, It refers to the functional role of species in its habitat and more, precisely in its microhabitat., , Responses to Abiotic Factors, Organisms cope up with the stressful conditions or possibilities to, manage with the adverse situation., With following modifications, an organism can stabilise its relationship, with environment., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Organisms and Populations, 577, Regulate, Some organisms are able to maintain a constant body temperature and, constant osmotic concentration despite changes in the external, environment, e.g., thermoregulation. Human is an isothermic, organism, it regulates the temperature in summers by sweating and in, winters by shivering. The process of regulation mostly occurs in birds, and higher animals., , Conform, It is the strategy of adjustment of organisms towards environmental, conditions. In this, an organism controls its physiology in the tune of, environmental conditions, e.g., poikilotherms. These organisms fail to, maintain their body temperature and change it with the environment,, e.g., fishes., , Migrate, It is the movement of an organism from less favourable conditions to, more favourable conditions., On the basis of driving factors of migration, it is of following four types, (i) Diurnal migration When migration is controlled by the cycle, of day and night, e.g., the movement of planktons towards the, surface of aquatic bodies during night and descent to depth, during day., (ii) Metamorphic migration This type of migration is controlled, by stage of life, e.g., salmon fishes living in Pacific ocean ascend, freshwater stream once in life for spawning and after laying, eggs, they die. Offsprings return back to the ocean to develop for, the period of years before they again repeat the event., (iii) Periodic migration These migrations are controlled by size, and population, e.g., several insects migrate from their place of, origin, when population increases beyond carrying capacity of, that place., (iv) Annual migration This migration is regulated by the time of, year, e.g., Siberian Cranes migrate to India at specific period, (July to September month)., , Suspend, During unfavourable conditions, organisms slow down their metabolic, process, e.g.,, (i) Lower plants produce spores with thick covering to sustain, unfavourable conditions and germinate in favourable, conditions., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 578, , Handbook of Biology, , (ii) Polar bears undergo hibernation during winters., , Internal level, , rs, me, r, o, nf, Co Regulators, , Partial regulators, , External level, , Diagrammatic representation of organismic response, , Adaptations, Organisms are adapted morphologically, physiologically, behaviourally, to survive and reproduce in their habitat by making adjustments with, environment., Adaptations are of two types, Types of Adaptations, Genotypic Adaptations, , Phenotypic Adaptations, , • Genetic variations which enable a, sub-population to adapt itself to a, particular habitat and environmental conditions., , • It involves physiological,, , • Genotypic variants in a population or, individual species due to change in, environment are called ecotypes., , and morphological, modification., • Phenotype variants formed, in a population due to change, in environment are called, ecophenes or ecads, , Strategic Adaptations in Plants, 1. Plant Adaptations to Light Regime, (i) Heliophytes/Sun Loving Plants, (a) Stem with short internodes, leaves thicker and bladed, phototropism., (b) High respiration rate. ‘These plants grow in bright light, but, some heliophytes can grow in partial shade, e.g., sugarcane,, sunflower, maize and Bougainvillea etc., (ii) Sciophytes/Shade Loving Plants, Stem thin, long internode, sparsely branched, poorly developed, conducting and mechanical tissue., These plants grow in partial shade or low light, but some, sciophytes are not damaged by bright light, e.g., Drosera,, Nepenthese, birch, spruce, etc., These are aerobic, show low rate of respiration., l, , l, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Organisms and Populations, 579, (iii) Stratification, In a forest, plants get arranged in various strata (layers/ arrangement, according to their size, i.e., grasses, herbs, shurbs and trees) according, to their shade tolerance, it is called as stratification., , 2. Plant Adaptations to Aquatic Environments, The plants growing in aquatic habitat are called as hydrophytes or, aquatic plants. Hydrophytes are of five types, (i) Emergent Hydrophytes (Amphibious Plants), Plants grow in shallow water of marshy area/swamps., Long shoot, aerial leaves with stomata, root well-developed,, rhizome present., Cuticle present to avoid dessication, developed vascular bundles,, e.g.,Ranunculus., l, , l, , l, , (ii) Submerged Hydrophytes, Poorly developed roots., Thin leaves, stomata are absent., Leaves are finely dissected., Stem soft, flexible, spongy with no cuticle layer in epidermal cells., Aerenchyma occurs in the roots and stem. Vascular tissues are, reduced. e.g., Hydrilla, Vallisneria., l, , l, , l, , l, , l, , (iii) Suspended Hydrophytes, Roots are absent., Never come in contact with the bottom., In all characters, they resemble with the submerged hydrophytes,, e.g., Utricularia, Lemna species., l, , l, , l, , (iv) Free-floating Hydrophytes, Plants are free floating in water, no connection with bottom., Plants have air storing organs (e.g., inflated petiole in Eichhornia)., Roots help in balancing and root tips are covered by root pockets., Stomata are present on the upper surface of leaves, e.g., Azolla,, Trappa, Eichhornia etc., l, , l, , l, , l, , (v) Anchored Hydrophytes with Floating Leaves, These plants float on surface but rooted at bottom of shallow water, body., Large leaves, long petiole, vascular system is well-developed., Large air cavities, leaves with wax to avoid wetting., Stomata present on upper surface of leaves e.g., Nymphoides,, Potamogeton species., l, , l, , l, , l, , www.aiimsneetshortnotes.com
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580, , Telegram @neetquestionpaper, , Handbook of Biology, , 3. Plant Adaptations to Water Scarcity and Heat, Xerophytic plants which live in dry conditions and show high rate of, transpiration than absorption of water. Deep root system, woody stem,, green photosynthetic leaves reduced to spine to prevent water loss., There are mainly four types of xerophytic plants which are discussed below, (i) Ephemerals or Drought Escapers, These plants live for a brief period during the rain., Small size and larger shoots and roots., They are generally found in arid zone, e. g. , Euphorbia species,, Solanum, Argemone mexicana., l, , l, , l, , (ii) Annuals or Drought Evaders, These plants live for a few month even after stoppage of rain., They need small quantity of water for their growth and development., Similar to ephemeral xerophytes, but grow for longer periods, e.g.,, Echinops echinatus and Solanum surattense., l, , l, , l, , (iii) Succulent or Drought Resistant, These plants store water and mucilage in fleshy organs., They have water storage region made up of thin-walled, parenchymatous cells., Stem is green, photosynthetic and have thick cuticle., They are called phylloclades (stems of indefinite growth) and, cladodes (1-2 internode long stems), e.g., Opuntia and Euphorbia., l, , l, , l, , l, , (iv) Non-Succulent Perennial Xerophytes or Drought Endurers, These are true xerophytes or euxerophytes., They have smaller shoot system and very extensive root., Leaflets of leaves are often small, vertical, thick and leathery, e.g.,, Nerium and Calotropis procera., l, , l, , l, , 4. Plant Adaptations to Saline Environment (Halophytes), Halophytes show following characteristics as their adaptations, (i), , Accumulation of, Several Compounds, , (ii) Maintain High, , Osmotic Pressure, , Growing with NaCl, MgCl2 and high, concentration of salt., They have a high osmotic pressure, (minimum of 40 bars)., , (iii) Structural Adaptations, , Succulent leaves, stem or both, thick cuticle,, sunken stomata. These have substances like, tannins and other wax substances to reduce, insolation and prevent desiccation., , (iv) Secretion of Some, , They secrete salt like atriplex, spartina, through chalk or salt glands, , Products, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Organisms and Populations, 581, Halophytic adaptations including structural and physiological, modifications can be explained through the example of mangroves., Stilt Roots, • Additional support to the, plants., • They developed by, nodes as well as, internodes, e.g., sugar, cane, bamboo, all grass, family Rhizophora., , Sunken stomata, , Thick cuticle, Parenchymatous tissue, (water storage tissue), , Pneumatophore, It is negatively geotrophic, vertical roots., , Chlorenchymatous tissue, (palisade tissue), , Knee Roots System, allow the gases exchange,, e.g., Bruguiera, gymnorrphiza, , Salt Gland, Several mangroves secrete, salt through salt glands, (e.g., Avicennia), , Plank Roots, , • The exposed vertical, portion helps in aeration, and widely spreading, roots help in improved, anchorage in unstable, mud., • Plank roots also called, Buttress Roots, snake roots, • They provide stability to huge trees specially in tropical area., • They can grow up to 10 m in height, e.g., Heritiera littoralis and, Pellicioera rhizophorae., , Structural modifications in plants to saline environment, , 5. Plant Adaptations to Oligotropic Soils, l, , l, , l, , l, , Oligotropic soils are poor in nutrients., One such type of soil, which supports dense vegetation is the one, found in tropical rainforests., Top soil of oligotropic region has shallow while subsoil has dense, clay mixed with Fe - Al (iron-aluminium) compounds., Major adaptation of tropical plants is the presence of mycorrhizae, (plant roots with fungi)., , Mycorrhizae are of two types, (i) Ectomycorrhiza When the fungal hyphae present outside, the host cell, it is called ectomycorrhiza., (ii) Endomycorrhiza When the fungal hyphae present inside, the host cell, it is called endomycorrhiza., , www.aiimsneetshortnotes.com
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582, , Telegram @neetquestionpaper, , Handbook of Biology, , Strategic Adaptations in Animals, l, , l, , l, , Animals also develop strategies to live better in their environment., Animal adaptations may be of two types, (i) Short term It is temporary like increase of heartbeat., (ii) Long term It is permanent in nature like typical type of beak,, claw, etc., In animal, most adaptations occur against environmental changes, and stress conditions. These may be physiological and behavioural, adaptations, e.g., migration, hibernation, aestivation, camouflage,, mimicry, echolocation, water scarcity and prevention of freezing., , 1. Adaptations to Cold Environment, Some animals protect themselves from excessive cold by developing, hard covering as they cannot undergo hibernation and cannot migrate,, e.g., barnacles and molluscs of intertidal zone of cold areas, several, insects and spiders., Some animals are adapted to colder environment by developing extra, solutes in their body fluids and special ice nucleating proteins in the, extracellular spaces., These extra solutes which prevent freezing, are glycerol and antifreeze, proteins. Ice fish (Chaenocephalus) or Antarctic fish (Trematomus), remain active even in extremely cold sea water due to this hardness., Mammals from colder climates generally have shorter ears and limbs, to minimise heat loss. This is called Allen’s rule., , 2. Adaptations to Water Scarcity, l, , l, , l, , Animals face water scarcity in desert areas. They show two types of, adaptations for reducing water loss and ability to tolerate arid, conditions. Camel has a number of adaptations to desert conditions, like water consumption, tolerance with temperature, etc., The animal produces dry faeces and urine., Camel can rehydrate itself quickly. Its storage capacity of water is about, 80 litres., , 3. Adaptations to Environmental Stress, These are of three types, (i) Hibernation and aestivation Hibernation or winter sleep, and aestivation or summer sleep are quite common in, ectothermal animals., (ii) Acclimatisation It is the development of a favourable, morphological and physiological response to a change in the, environment., (iii) Migration It is the movement of an animal to other places for, food, climate and other reasons., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Organisms and Populations, 583, 4. Adaptations for Protection from Predators, Camouflage, It is the ability of an organism to blend with the surrounding or, background. Organisms use camouflage to mask their location,, identity and movement, e.g., many insects, reptiles and mammals, (like military colouration dress), insects (like butterfly)., Mimicry, It is the resemblance of a species with another species in order to, obtain advantage, especially against predation., The species which is copied is called model, while the animals, which copy are known as a mimic or mimictic., l, , l, , These are of two types, (i) Batesian mimicry In this mimicry, the mimic is, defenceless, e.g., viceroy butterfly mimics unpalatable toxic, monarch butterfly., (ii) Mullerian mimicry In this mimicry, there is a resemblance, between two animal species, especially insects to their mutual, benefit, e.g., monarch butterfly and queen butterfly., Warning Colouration, Dart frogs (Phyllobates bicolor, Dendrobates pumilio) found in tropical, rainforests of South America are highly poisonous as well as brightly, coloured to be easily noticed. Predators usually avoid them., , Population and Community, As combination of several populations in an area makes community,, the relationship between these two is established. The comparative, account of both population and community is given below., , Differences between Community and Population, Community, , Population, , It is a grouping of individuals of different, species found in an area., , It is a grouping of individuals of a single, species in an area., , Interbreeding is absent amongst different, members of a community., , Individuals interbreed freely., , Different members of a community are, morphologically and behaviourly dissimilar., , Morphologically and behaviourly similar, species are found in a population., , It is a large unit of organisation., , It is a small unit of organisation., , In a biotic community, there is often a, relationship of eating and being eaten., , There is no relationship of eating and, being eaten., , www.aiimsneetshortnotes.com
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584, , Telegram @neetquestionpaper, , Handbook of Biology, , Characteristics of Population, Dispersal, Emigration, , Immigration, , Exit of individuals, from population., , Entry of individuals, into population., , Natality (Birth rate), , Density, , Natality is the rate of production, of new individuals per unit of, population per unit time., Natality is expressed as, ∆Nn/∆t =Absolute natality rate, , Density is the number, of individuals, per unit area or volume., Density is represented, as, N, D= —, S, N = Total number of, individuals,, S = Space/Area, , Dispersion, It indicates how the, individuals of a population, are distributed in space, and time. Three possible ways, of dispersion are uniform,, random and clumped., , ∆Nn/N∆t = Specific natality rate, (i.e. Natality rate per unit of population), Where,, N = Initial number of organisms, n = New individuals in the population, t = Time, , Characteristics of, Population, , Mortality (Death rate), , Biotic Potential, It is the maximum reproduction, capacity of a population, under optimum, environmental conditions., Vital index = Number of birth/, Number of death, It is the highest possible vital, index of a species, therefore when the, species has its highest birth rate and, lowest mortality., , Age Distribution, , It is the rate of loss of individuals, per unit time due to death, (i) Specific Mortality, Minimum death rate under ideal, conditions due to natural processes., (ii) Realised Mortality, Actual death rate due to abnormal, conditions like disease,, natural hazards., , The ratio of various age, groups is very important, for future aspects of population., (i) Pre-reproductive, Juvenile or dependent phase, (ii) Reproductive, Adult phase, (iii) Post-reproductive, Old age., , Population Growth Curves, S-shaped, , 0, , Carrying capacity, of environment, , dN, — = rN, dt, The growth rate, of the population, accelerates, , Time (t), , Population size (N), , Population size (N), , J-shaped, , 0, , (a) Exponential, (unrestricted) growth, , dN, — =rN (K – N/K), dt, , The rate, accelerates, , The, rate, slows, down, Point of, maximum, growth, , Time (t), (b) Logistic (restricted), growth, , (a), Expanding, population, (Triangular-shaped), (b), Stable, population, (Bell-shaped), (c), Declining, population, (Urn-shaped), Post-reproductive, Reproductive, Pre-reproductive, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Organisms and Populations, 585, Population Interactions, Organisms belonging to different populations interact for their necessities, Population Interaction (on the basis of species involved), 1. Intraspecific (within the species), 2. Interspecific (between species) These are of two types, (i) Antagonism (one species or both may be harmed), e.g.,, Coytes kill and ingest gray fox in South California., (ii) Symbiosis (one species or both may be benefitted), e.g.,, Mycorrhizal roots., Population interactions can also be categorised on the basis of its, nature., Population Interactions, (on the basis of interaction of nature), , Positive Interaction, , Negative Interaction, , (one or both may be benefitted), , Mutualism, , Proto-cooperation, , The association is, No obligatory in nature, obligatory, e.g., roots, but both the partners get, of some leguminous plants, benefitted, e.g., sea anemone, and N2 -fixing bacteria., and hermit crab., , (one or both may be affected), , Commensalism, Only one might be, benefitted but other, is not affected,, e.g., epiphytes., , Competition, , Parasitism, , Predation, , It is presumed that the, superior competitor, eliminates the inferior, one. It is of two types, (i) Intraspecific competition, (ii) Interspecific competition, , It is an interaction between two, individuals, where the parasite, gets the benefit at the expense, of the host. It is of different categories, , It is the eating of, one species by, another., Predators consume, other living animals,, e.g., Nepenthes., , (i) Ectoparasites, e.g.,human body lice., (ii) Endoparasites, Gause’s competitive exclusion, e.g., Plasmodium malariae., principle states that the two, (iii) Facultative parasites, closely related species, e.g., Oyster prawn., competing for the same resources, (iv) Obligate parasites, cannot co-exist indefinitely and, e.g.,Taenia solium., the competitively inferior one will, be eliminated eventually., , Interaction and adaptation of organisms into their environment can be, accomplished by various strategies. These strategies ultimately help in, the establishment of new communities. Detailed study of these, processes of establishments throws light on several new fields of, environmental studies., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 36, Ecosystem, An ecosystem consists of biological community that occurs in some, local and the physical and chemical factors that make up its non-living, or abiotic environment., , Ecosystem, ‘Ecosystem is normally an open system because there is a continuous, entry and loss of energy and materials’., The term ecosystem was first used by AG Tansley in 1935 to, describe the whole complex of living organisms living together as a, sociological unit and their habitats., The ecosystem is also called as biocoenosis (Mobius; 1877),, microcosm (Forbes; 1887) and biogeocoenosis (Sukachey)., It is also known as ecocosm or biosystem., , Types of Ecosystem, On the basis of origin, the ecosystem can be of following types, Ecosystem, , Natural Ecosystem, , Artificial Ecosystem, These systems are maintained and, manipulated by men for different, purposes, e.g., croplands,, township, etc., , The ecosystems which are, capable of operating and, maintaining themselves., It is further classified as, , Terrestrial Ecosystem, , Aquatic Ecosystem, , e.g, forest, desert,, grassland, etc., , e.g., pond, lake, river, etc., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Ecosystem, 587, Components of Ecosystem, Eugene P Odum explained the components of ecosystem on the basis, of trophic levels which are as follows, Inorganic Substances, Carbon, nitrogen, sulphur, potassium,, carbon dioxide, water, etc., , Abiotic Components, , Organic Substances, Proteins, carbohydrates, lipid, etc., , Climatic Regime, Temperature, humidity,, soil, light, pressure, etc., , Producers (autotrophic component), Autotrophic organisms, i.e., plants (green), and photosynthetic bacteria, , Biotic Components, , Macroconsumers (heterotrophic components), Phagotrophs or heterotrophs, i.e., animals and, non-green plants, Microconsumers (decomposers), Transformers or decomposers,, i.e., bacteria and fungi, , Components of ecosystem, , Abiotic Components, Abiotic components of an ecosystem consist of two things, i.e.,, materials (e.g., water, minerals, gases, etc.) and energy., The important abiotic components include temperature, wind, light,, water, soil and minerals, etc., 1. Temperature, It is the most ecologically relevant environmental factor. Latitude,, altitude, topography, vegetation and slope aspects are some, factors which influence the temperature., Temperature regulated periodic activities are reported from animals,, e.g., diurnal (active during day), nocturnal (active during night),, auroral (active at dawn), vesperal (active during evening) and, crepuscular (active in twilight)., , www.aiimsneetshortnotes.com
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588, , Telegram @neetquestionpaper, , Handbook of Biology, , 2. Water, It is the most important factor for all living processes. Infact the life on, earth originated in water and without water, it is unsustainable., Water constitutes the most part of our body and blood. On the basis of, water availability in plants, they are grouped into three communities, namely hydrophytes, mesophytes and xerophytes., 3. Light, Light with wavelength between 400–760 nm is the visible light. The, part of light which is effective in photosynthesis (i.e., 400-700 nm) is, termed as Photosynthetically Active Radiation (PAR)., This band of energy provides radiant energy for photosynthesis and, thus supports all autotrophic organisms., 4. Soil, It is weathered top surface of earth’s crust constituted by mineral, matters (sand, silt and clay), organic matter (humus) and, microorganisms (bacteria, fungi, etc)., Soil is the medium of anchorage and supply of nutrients and water to, plants and plants are the ultimate source of energy for animals and, humans. Hence, soil constitutes the important life support component, of the biosphere., , Biotic Components, The biotic components are divided into following categories, (i) Autotrophic components (producers) Living organisms, which fix light energy to manufacture the complex organic, food from simple inorganic substances, e.g., green plants., (ii) Heterotrophic components (macroconsumers) Living, organisms that ingest other organisms and are therefore, called heterotrophs. They derive their food directly or, indirectly through green plants, e.g., animals, etc., (iii) Decomposers (microconsumers) Decomposers are also called, as saprobes or saprophytes or mineralisers, as they release, minerals trapped in organic substances, e.g., fungi, mould,, bacteria, etc., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Ecosystem, 589, On the basis of their role in trophic structure, macroconsumers or, consumers are categorised as, , Consumers, (i) Primary consumers (herbivores) These organisms feed directly, on producers. These are also known as key industry animals, e.g.,, protozoans (pond ecosystem), deer (forest ecosystem), etc., (ii) Secondary consumers (carnivores) The group of organisms, which feed on primary consumers, e.g., insects, game fishes, etc., (iii) Tertiary consumers (top carnivores) These animals eat other, carnivores. Some ecosystems have top carnivores like lion and, vulture., Note Detritivores These organisms depend on the organic detritus left by, decomposers (bacteria and fungi), e.g., earthworms., , Ecosystem : Structure and Characteristics, Boundary of, Ecosystem, An invisible boundary inside, which the conditions are, habitable for organisms, of that specific ecosystem., , Sun, The ultimate, source of energy, for any ecosystem., , Climate, The region of ecosystem, which results by the interaction, between organisms., , Earth-Giant, Ecosystem, , Producers, Man, Forest Grassland Desert engineered, 1, , 3, , 2, Terrestrial, ecosystems, , 4, , Freshwater Marine, 5, , Nutrient Pool, , May be, terrestrial, or aquatic, , R, , Aquatic, ecosystems, , Decomposers, E, G, Materials, Energy, , 6, , I, , Consumers, M, , E, , Nutrient Pool, A reservoir in which the mineral, products from decomposers are, present and are absorbed by producers., , Structure of an ecosystem (generalised), , www.aiimsneetshortnotes.com
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590, , Telegram @neetquestionpaper, , Handbook of Biology, , Features of Ecosystem, A comparative account of several ecosystems is given in the following, table, Comparative Summary of Marine, Grassland,, Forest and Desert Ecosystems, Marine, Ecosystem, , Component, , Grassland, Ecosystem, , Forest, Ecosystem, , Desert, Ecosystem, , Soil and, atmosphere., , Rainfall less than, 25 cm, extreme of, temperature and, cold., , Abiotic, components, , Temperature, CO 2 , H2O , nitrate,, zones, air, O 2 ,, phosphate and, mineral rich salts, sulphates, roughly, 19% of the earth’s, etc., crust., , Biotic, components, , Phytoplanktons,, diatoms and, dinoflagellates., , Dichanthium and, Cynodon., , Mainly trees like, teak, sal., , Producers, , Microscopic algae,, members of, Phaeophyta and, Rhodophyta., , Digitaria,, Dactyloctenium,, Setaria and also, few shrubs., , Cycads, cacti,, Quercus in, temperate forest, palm, coconut,, Pinus, Abies,, etc., Cedrus, Juniperus, and, Rhododendron., , Deer, sheep, cow,, buffaloes, rabbit,, mouse. Also some, insects, termites, and millipedes., , Leafhoppers, flies, Animals, insects,, some reptiles and, beetle, bugs,, spider, deer,, camel., mouse and, moles., , Shrubs, bushes,, some grasses and, very few trees., , Macroconsumers, Primary, , Crustaceans,, molluscs and, fishes., , Secondary, , Carnivorous fishes. Fox, jackal, snake,, frogs, lizards and, birds., , Lizard, fox, snake Reptiles, and birds., , Tertiary, , Herring, shad and, mackerel carnivore, fishes like cod,, haddock, halibut,, etc., , Hawk and vulture., , Lion, tiger, wild, cats, etc., , Vultures, , Mucor, Aspergillus,, Penicillium,, Fusarium,, Cladosporium and, Rhizopus., , Mostly fungi, Aspergillus,, Polyporus,, Fusarium, etc., Bacteria Bacillus,, Clostridium and, Streptomyces., , Fungi and bacteria, which are, thermophilic., , Microconsumers, Decomposers Chiefly bacteria, and fungi., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Ecosystem, 591, Functions of Ecosystem, Following are the important functional aspects of the ecosystem, 1. Productivity, 2. Energy flow, 3. Development and stabilisation, 4. Decomposition, 5. Nutrient cycle, Before going in detail about the functional aspects of ecosystem, we, need the better understanding of food chain and food web., , Food Chain, As the biotic factors of the ecosystem are linked together by food, a, particular linking makes a chain called food chain. It is ‘A group of, organisms in which there is a transfer of food energy which takes place, through a series of repeated process of eating and being eaten’., It is always straight and usually contains 4-5 trophic levels., , Types of Food Chains, On the basis of habits of organisms involved, the food chain can be, categorised as, Parasitic Food Chain (PFC), It is also called auxillary food, chain. This chain begins, with the host and usually ends, with parasites, due to which its, pyramid of number is inverted., Its food sequence is as follows, Plant, Herbivores, Parasites, , Grazing Food Chain (GFC), It is the most common food chain., It is also called as predator food, chain. The sequence of food chain, in an aquatic ecosystem is as follows, , Producers (autotrophs), Phytoplanktons like weeds,, diatoms and other green algae, , Hyper-parasites, , Food, Chain, , Primary Consumers (herbivores), Zooplanktons like dinoflagellates, Secondary Consumers, (primary carnivores), Aquatic insects, crustaceans, and other aquatic organisms, , Tertiary Consumers, (secondary carnivores like small fish), , Detritus Food Chain (DFC), It starts from the dead organic matter and ends in, inorganic compounds. A common detritus food, chain with earthworm is as follows, Detritus, , Earthworm, Frog, , Top Carnivores (large fish), , Sparrow, , Falcon, , Snake, , Peacock, , Types of food chain, , www.aiimsneetshortnotes.com
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592, , Telegram @neetquestionpaper, , Handbook of Biology, , Food Web, It is the network of food chains which become interconnected at, various trophic levels. In any complex food web, one can recognise, several different trophic levels., In a food web, a given species may occupy more than one trophic level., The complexity of food web varies greatly and this can be expressed by, a measure called connectance of the food web., Actual number of interspecific interaction, Connectance =, Potential number of interspecific interaction, A typical food web can be represented as follows, Hawk, , Lion, , Owl, , Bird, , Snake, Fox, , Frog, Caterpillar, Deer, Grasshopper, , Rabbit, , Green plants, , Food web, , 1. Productivity, It refers to the rate of biomass production, i.e., the rate at which the, sunlight is captured by the producers for the synthesis of energy rich, organic compounds., It is the amount of organic matter accumulated per unit area per unit, time., Production Ecology is the branch of Ecology that deals with the rate, of production of organic matter in ecosystem., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 593, Ecosystem, It is of following types, Productivity, Primary Productivity, , Secondary Productivity, , The rate at which radiant energy is, stored by the photosynthetic and, chemosynthetic activities of producers., It is of following types, , Gross Primary, Productivity, (GPP), , It is the rate of energy, storage at consumer level,, i.e., herbivore, carnivore, and decomposers., , Net Productivity, It is the rate of, storage of organic, matter not used, by the heterotrophs, or consumers., , Net Primary, Productivity, (NPP), , It is the total rate of, photosynthesis including, the organic matter used, up in respiration., , It is the rate of storage, of organic matter in excess, of respiratory utilisation., , Measurement of Productivity, As a result of photosynthesis, there is an increase in dry mass. The, Relative Growth Rate (R) is defined as the gain in mass per unit of, plant mass in unit time., Increase in dry mass in unit time, R =, Dry mass of plant, w − w0, The increase in dry mass in unit time is equal to t, t, wt = dry mass after time t,, w0 = dry mass at the start of time period., The Net Assimilation Rate (NAR) relates increase in dry mass to, leaf area., Increase in dry mass in unit time, NAR =, Leaf area, Biomass is the total dry mass of all organisms in an ecosystem., Total biomass = Biomass of primary producers + Biomass of consumers, + Biomass of decomposers + Biomass of dead organisms., , 2. Energy Flow, ‘The movement of energy in ecosystem is termed as energy flow’., It is unidirectional energy transformation. The flow of energy in, ecosystem is controlled by two laws of thermodynamics., (i) First law Energy can neither be created nor be destroyed, but, can be transferred or transformed to another form., , www.aiimsneetshortnotes.com
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594, , Telegram @neetquestionpaper, , Handbook of Biology, , (ii) Second, law In, every, activity, involving, energy, transformation, dissipation of some energy takes place., The incident radiation of plant is about 1 × 106 kJ/m 2/yr and of this,, about 95-99% is immediately lost by plants through reflection,, radiation or heat of evaporation., The remaining 1-5% is used in the production of organic molecules., Organisms at each trophic level depend on those belonging to the lower, trophic level for their energy requirements., Each trophic level contains certain mass of living matter at a, particular time called standing crop. The standing crop is measured, as the mass of living organisms (biomass)., The number of trophic level in the food chain is restricted as the, transfer of energy follows 10% law given by Raynold Lindemann., Following diagram clearly describes the flow of energy in a food chain, applying 10% law, , 1 × 106 Solar energy, , Autotrophs, Phototroph, 0.5 x 106, 10000, absorbed, GPP, , Herbivores, C, 800, secondary, production, , C, , 8000, NPP, , a th, De, , 0.5 × 106, Not absorbed, (reflected), , R, , R, , 2000, R, , 0.49 × 106, Heat of evaporation,, conduction, convection, , E, , R, 80, C, secondary, production, , E, , 8, , E, , Death, E, , E, , Death, , E, , Death, , Detritivores and decomposers, , Energy flow through a grazing food chain, , R = Energy loss through respiration, E = Energy loss from grazing, food chain to detritivores and decomposers through excretion,, C = Consumption by organisms., Here, biomass 800, 80 and 8 kJ/m 2/yr, NPP shows that only 10%, energy is transferred to the next trophic level., , Ecological Pyramids, These are the diagrammatic representation of the relationships among, numbers, biomass and energy content of the producers and consumers, of an ecosystem. The concept was proposed by Charles Elton (1927)., Hence, these are also known as Eltonian pyramids., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Ecosystem, 595, Types of Pyramids, Pyramids can be of different types including upright or inverted or, spindle-shaped., One, vulture, Few, snakes, Several frogs, , Numerous, parasites, Several birds, , Many grasshoppers, Single long tree, , Crop plants, , Forest ecosystem, , Grassland ecosystem, Upright, In most of the ecosystems,, e.g., grassland ecosystem, , Pyramid of, Numbers, Inverted, Only in some tree, ecosystems, , Upright, Most terrestrial and, aquatic ecosystems, , Types of, Pyramids, , Pyramid of, Biomass, Inverted, In marine ecosystem, , Pyramid of Energy, , Numerous parasites, Large fish, , Several birds, , Crustaceans, and small fish, , Single tree, , Phytoplanktons, Tree ecosystem, Always Upright, e.g., pond ecosystems, , Marine ecosystem, , One One, tiger bird, Several Several, rabbits fishes, Numerous, grasses, and plants, , Numerous, phytoplanktons, , Pyramid of energy, , www.aiimsneetshortnotes.com
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596, , Telegram @neetquestionpaper, , Handbook of Biology, , Spindle-shaped pyramid is seen in the forest ecosystem where the, number of producers is lesser and they support a greater number of, herbivores, which in turn support a fewer number of carnivores., , Carnivores, Herbivores, Producers, , Partly upright pyramid of number, , 3. Development and Stabilisation, An ecosystem develops and stabilises through the process of, ecological succession., , Ecological Succession, It is a sequence of seres (developmental stage of a community) from, barren land to the climax., The initial community of the area which is replaced in time by a, sequence of succeeding communities until the climax is reached is, called pioneer stage or pioneer community. The intermediate, stages between pioneer and climax stages (i.e., final stage) are called as, seral stages., , Causes of Succession, The causes of ecological succession can be of three types which are as, follows, Initial or Initiating, Causes, , These causes are both climatic, and biotic. It includes factors, such as erosion, wind, fire, etc., These heavily affect the, population of that locality., , Ecesis Causes, , These are also called as, continuing causes which modify, the population to adapt several, conditions of environment., , Stabilising, Causes, , The climatic causes determine, the nature of climatic climax,, i.e., the end point of succession., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Ecosystem, 597, Changes During Biotic Succession, The following changes may occur due to ecological succession, (i) Small short lived plants to large long lived plants., (ii) Unstable biotic community to stable biotic community., (iii) Little diversity to high diversity., (iv) Greater niche specialisation., (v) Increase in biomass., (vi) Increase in soil differentiation., (vii) Increase in humus content of the soil., (viii) Aquatic or dry conditions to mesic conditions., (ix) Simple food chains to complex food webs., , Types of Succession, Primary, Succession, , Allogenic, Succession, When the succession is, caused by the factors, external to the, community., , Clarke (1954), defined, it as the succession which, begins on a bare area, where no life has existed., , Secondary, Succession, , Autogenic, Succession, The succession, which is brought, about by organisms, themselves., , Biological, Succession, , Heterotrophic, Succession, The succession which begins, predominantly on, organic environment and, dominance of, heterotrophic organisms, mainly occurs., , It refers to the community, development on the sites, previously occupied, by well-developed, communities., , Autotrophic, Succession, Succession that begins, predominantly on, inorganic environment, and characterised by the, dominance of autotrophic, organisms., , Various types of succession, , www.aiimsneetshortnotes.com
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598, , Telegram @neetquestionpaper, , Handbook of Biology, , Process of Succession, The succession is a slow and complex phenomenon, which is categorised, into following stages and substages, This means the development of bare areas, without any form of life., It may be caused by following factors, Topographic, e.g., soil erosion by various factors., Climatic, e.g., glaciers, dry period, hailstorm, fire, etc., Biotic, e.g., human, fungi, viruses, etc., It is the successful establishment of a species in a, barren area. It is completed in following substages, Migration The seed, spores and propagules, reach to barren area., Ecesis Adjustment of establishing species with, environment prevailing there., Aggregation Multiplication of species in numbers., , Nudation, , Invasion, , Competition and, Co-action, Reaction, Stabilisation, , After aggregation, the individuals of a species compete, with other organisms for space, nutrition and other, resources., The modification of the environment through the, influence of living organisms on it is called reaction., The stage at which final or climax community becomes, more or less stabilised for a longer period of time, in that particular environment., , The processes involved in succession, , Examples of Biological Succession, Hydrosere and xerosere are the two main biological successions., They are discussed below, (i) Hydrosere/Hydrarch Succession, In this succession, a pond and its community are converted into a land, community., , www.aiimsneetshortnotes.com
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600, , Telegram @neetquestionpaper, , Handbook of Biology, , Developments in Xerosere/Xerarch succession occurs in following stages, Bare Rock, , Crustose Lichen Stage (pioneer community), e.g., Rhizocarpon, Rhinodina, etc., , Foliose Lichen Stage, e.g., Parmelia, Dermatocarpon, etc., Moss Stage, e.g., Polytrichum, Grimmia, etc., , Seral, Communities, , Herb Stage, e.g., several herbs., Shrub Stage, e.g., Rhus, Phytocarpus, etc., Forest Stage (climax community), e.g., trees., , Succession on bare rock, , 4. Decomposition, The process of decomposition completely takes place outside the body, of decomposers., They digest the organic substances outside their body and then absorb, it. Hence, they are also known as osmotrophs (absorptive)., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Ecosystem, 601, Process of Decomposition, There are three processes which occur simultaneously during, decomposition., Fragmentation of, Detritus, , The detrivore animals like, earthworms and termites, eat the detritus and convert, it into simple inorganic substances., This is called fragmentation., , Leaching, , Soluble part of the detritus, (i.e., sugar, inorganic nutrients) gets, leached to the lower layers of soil, by percolating water., , Catabolism, , It is carried out by saprotrophic, bacteria and fungi. It is completed, in following two substages., , Humification, , Mineralisation, , It is the process of partial, decomposition of detritus, to form humus. It is a dark, coloured, amorphous, organic, matter rich in cellulose, lignin,, etc. It is slightly acidic and acts, as reservoir of nutrients., , It is the release of, inorganic substances, i.e., CO2, H2O and, minerals., , Factors Affecting Decomposition, (i) Chemical nature of detritus Slow decomposition (cellulose,, lignin, tannin, resin), fast decomposition (protein, nucleic acid)., (ii) Soil pH Acidic (slow decomposition), alkaline soil (fast, decomposition)., (iii) Temperature Temperature ∝ rate of decomposition., (iv) Moisture Amount of moisture ∝ rate of decomposition., (v) Aeration Amount of air ∝ rate of decomposition., , 5. Nutrient Cycling, For the maintenance of ecosystem, the nutrients get recycled in, ecosystem. The cycling of nutrients is also known as biogeochemical, cycling. This can be categorised as, Nutrient Cycle/Biogeochemical Cycle, Gaseous Cycles, , Sedimentary Cycles, , In these cycles, the, main reservoirs of chemicals, are atmosphere and ocean,, e.g., carbon cycle,, nitrogen cycle, etc., , In these cycles, the, main reservoirs are, soil and rocks, e.g.,, phosphorus, and sulphur cycle., , Hydrological Cycle, In this cycle, the, reservoir may be, in atmosphere, or in soil,, e.g., water cycle., , www.aiimsneetshortnotes.com
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602, , Telegram @neetquestionpaper, , Handbook of Biology, , Carbon Cycle, The atmospheric carbon dioxide is virtually the only source of carbon., This gas is used by all the plants in photosynthesis and the end, products (organic substances) of this complex process are used in the, construction of living matter. The complete carbon cycle looks like, CO2 in atmosphere, , Photosynthesis, (terrestrial food chains), , Combustion of fossil, fuels for vehicles,, electricity and heat, , Burning of forests,, fuel wood and, organic debris, , Respiration and, decomposition, , Coal, , Detritus food chain, , Photosynthesis Plankton, (aquatic food, chains), CO2 in, water, Organic, sediments, Decay, organisms, Calcareous, sediments, , Oil and gas, , Limestone and dolomite, , The carbon cycle, , Phosphorus Cycle, It lacks an atmospheric component. The basic source and the great, reservoir of phosphorus are the rocks and other deposits, which have, been found in the past geological ages., Weathering, , P, P Inorganic, in rocks, , Organic, in plants, , Decay, P, , Inorganic, in water, , P Available, inorganic in soil, , Organic, P in soil, , P Unavailable, inorganic in soil, River, , P Inorganic, in ocean, , Uplift over, geological time, , P, , Inorganic in, sediments, , Phosphorus cycle in nature, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Ecosystem, 603, Hydrological (Water) Cycle, Water moves in ecosystem through various reservoirs, i.e., ocean,, atmosphere and living organisms. Following diagrammatic, representation gives the idea of water cycle., Atmosphere, , Respiration, , Precipitation, , Evaporation, , Precipitation, , Evaporation, , Precipitation, , Tran, spir, Pre, atio, cipi, n, tatio, n, Plants, , Animals, , Water cycle in nature, , Ecosystem Services, Healthy ecosystems are the base for a wide range of economic,, environmental and aesthetic goods and services. The products of, ecosystem processes are named as ecological or ecosystem services., Ecosystem services refer to a wide range of conditions and processes, through which natural ecosystems and the species that are part of, them, help to sustain and fulfil human life., These services maintain biodiversity and the production of ecosystem, goods, such as seafood, wild game, forage, timber, biomass fuels,, natural fibres and many pharmaceuticals, industrial products and, their precursors. It is also the transformation of a set of natural assets, (soil, plants and animals, air and water) into things that we value., Robert Constanza et. al., have tried to put price tags on, nature’s life-support services. Scientists have estimated this price to be, 33 trillion US dollars a year, while our global gross production is only, 18 trillion US dollar., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 37, Biodiversity and, Conservation, Biodiversity (Gk. bios–life; divsersity–forms) or Biological diversity can, be defined as the vast array of species of living organisms present on, the earth., The term, ‘Biodiversity, was coined by WG Rosen (1985), but later, popularised by EO Wilson., Due to difference in habitat and environment, the biodiversity can be, studied at global as well as country level. In India, maximum species of, arthropods are found (approx 68,389) among animals, while among, plants, maximum species of angiosperms are found (17,500)., , Levels of Biodiversity, For the convenience of study, the biodiversity can be categorised in the, following three levels of biological organisations, , 1. Genetic Diversity (Within species diversity), The diversity in number and types of genes as well as chromosomes, present in different species and the variation in the genes and their, alleles in same species., It is useful as it involves the adaptation to change in the, environmental conditions and is also essential for healthy breeding., It also helps in speciation., , 2. Species Diversity (Between species diversity), It means the species richness in any habitat. Greater the species, richness, greater will be their diversity. India is among the world’s 15, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biodiversity and Conservation, 605, nations that are exceptionally rich in species diversity. Number of, individuals of different species represents the species evenness and, species equitability., , 3. Community and Ecosystem Diversity, (Ecological diversity), It is the diversity at ecosystem or community level. An ecosystem is, referred to as natural when it is undisturbed by human activities., Diversity at the level of community or ecosystem has three, perspectives, i.e., α, β and γ (Whittaker; 1965)., l, , γ - diversity, It is also called regional, diversity which represents, the total richness of species, in all the habitats found, within a region., , α-diversity, Site1, , γ, , It is also called local diversity., It is the diversity within community., , α1, , Region, , β, , α2, , α3, Site 3, , Site2, , β, β -diversity, It is the diversity between two, communities which develop, due to change in habitats along, environmental gradients., , Schematic representation of various levels of diversity, , Patterns of Biodiversity, 1. Latitudinal Gradient, Generally, species diversity decreases as we move away from the, equator towards poles., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 606, , Handbook of Biology, , Evergreen coniferous forests, Very rare biodiversity, but, plants are evergreen, , Decreasing biodiversity, towards poles, , 1, 66 –° N, 2, 1, 23 –° N, 2, , Temperate deciduous forests, and grasslands, Due to less rain, the diversity, is sparse and productivity is, low., , Tropical deciduous forests, , The biodiversity is nearly, equal to tropical rainforest., 0° Equator, , Tropical, region, , Tropical rainforest, 1, 23 –° S, 2, , Temperate, region, , 1, 66 –° S, 2, , The region of highest, biodiversity due to, suitable environment., , Temperate deciduous, forests and grasslands, Somewhat unfavourable, conditions lead to low, biodiversity and, productivity., , Biodiversity pattern on earth, , 2. Altitudinal Gradient, The impact of altitude is significant on the type of biodiversity. Mostly, the increasing altitude leads to decrease in biodiversity as only some, species can adapt the conditions prevailing at high altitude., Following graph gives the clear idea of this relationship, 2000, , Species richness, , 1600, 1200, , 800, 400, 0, 0, , 1000 2000, , 3000, , 4000, , 5000, , Elevation (m), , Effect of altitude on biodiversity, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biodiversity and Conservation, 607, 3. Species-Area Relationship, According to German naturalist and geographer Alexander von, Humboldt ‘‘Species richness increases with increasing explored area,, but only up to a certain limit’’., The relationship between species richness and area gives a rectangular, hyperbola curve for a wide variety of taxa like birds, bats, freshwater, fishes and flowering plants., On a logarithmic scale, the relationship is a straight line and is, described by the following equation, log S = log C + Z log A, Here, S is species richness, Z is slope of line or regression coefficient,, C is Y intercept, while A is area., Y-axis, , e, al, sc, g, -lo, lo, g, , Species richness, , S = CAZ, , los S = log C + Z log A, , Area, , X-axis, , Species-area relationship, , Ecologists have discovered that the value of Z-line is similar for a small, region or area particular, regardless of taxonomic group or region, (i.e., 0.1–0.2). But, if we consider a large area (i.e., whole continent),, the value of Z deviates between 0.6-1.2., , Importance of Biodiversity, Biodiversity is essential not only for ecosystem, but also for the, survival of human race. It maintains high productivity and human, health., , www.aiimsneetshortnotes.com
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608, , Telegram @neetquestionpaper, , Handbook of Biology, , The detailed description of importance of biodiversity is given below, Ecosystem Services, Biodiversity offers several, services like oxygen,, pollination of plants,, waste treatment and, biological control of, pests, etc., , Scientific Values, Several scientific researches, are performed over various, plant and animal species, which are used by humans, to their scientific knowledge, development., , Importance, of, Biodiversity, , Drugs and Medicines, The medicine of plant origin, have singnificant importance, in our therapy system., e.g., ayurveda., , Stability of Ecosystem, According to long term, ecosystem experiment, by David Tilman, the, ecosystem with more, species tends to be more, stable., , Food Source, Both plants and animals provide, ultimate source of food to the, population. 85% of the worlds food, production is met by cultivating less, than 20 plant species., , Other Useful Products, , Fibres, , Several products like gum,, resin, dye, fragrence, tea,, coffee latex, etc., are obtained, from biodiversity., , Biodiversity provides important raw, material for textile industry,, e.g., cotton, hemp, jute, etc., , Importance of biodiversity, , The importance of biodiversity is described through an analogy, (the ‘rivet popper hypothesis’) used by Paul Ehrlich in which he, compared ecosystem with airplane and the species with rivets., , Loss of Biodiversity, The loss of biological diversity is a global crisis. Out of the 1.6 million, species known to inhabit the earth, about 1/4 to 1/3 is likely to get, extinct within the next few decades. Tropical forests are estimated to, contain 50-90% of the world’s total biodiversity., The IUCN (International Union for Conservation of Nature and, Natural Resources) Red List (2004) documents the extinction of, 784 species (including 338 vertebrates, 359 invertebrates and, 87 plants) in the last 500 years., Some examples of recent extinctions include the dodo (Mauritius),, quagga (Africa), thylacine (Australia), Steller’s sea cow (Russia), and three subspecies of tiger (Bali, Java, Caspian)., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biodiversity and Conservation, 609, The last twenty years alone have witnessed the disappearance of, 27 species. Careful analysis of records shows that the extinctions, across taxa are not random; some groups like amphibians appear to be, more vulnerable to extinction., Adding to the grim scenario of extinctions, the fact is that more than, 15,500 species worldwide are facing the threat of extinction., Presently, 12% of all bird species, 23% of all mammal species, 32% of, all amphibian species and 31% of all gymnosperm species in the world, are facing the threat of extinction., In general, loss of biodiversity in a region may lead to, Decline in the plant production., Lowered resistance to environmental perturbations such as drought., Increased variability in certain ecosystem processes, such as plant, productivity, water use and pest and disease cycles., l, , l, , l, , IUCN and Red List Categories, International Union for Conservation of Nature and Natural Resources, (IUCN) is now called World Conservation Union (WCU),, headquartered at Morges, Switzerland., The Red Data Book, catalogue the taxa who face the risk of, extinction. It was initiated in 1963. The Red List contains 9 categories, of individuals according to their threats. These are, Extinct (Ex), Extinct in the Wild (EW), Regionally Extinct (RE), Critically endangered (CR), Endangered (EN), Vulnerable (VU), Near Threatened (NT), Least Concern (LC), Data Defecient (DD), l, , l, , l, , l, , l, , l, , l, , l, , l, , Out of these categories, 4, 5 and 6 are the threatened categories., , www.aiimsneetshortnotes.com
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610, , Telegram @neetquestionpaper, , Handbook of Biology, , Causes of Biodiversity Loss, Unbalanced human activities lead to accelerated extinction of species, from the world. The major causes of biodiversity reduction are termed, as ‘Evil Quartat’., Some important causes of biodiversity loss are given below, Habitat Loss, , Coextinction, In ecosystem, the species, are related with each other, in a trophic structure., Extinction of one species led to, the extinction of others as well,, it is called coextinction., , Causes of, Biodiversity, Loss, , Alien Species Invasion, When alien species invade in a, system by any method, they do, not have any environmental barrier, which lead to overcrowding of, the species and resulted into the, replacement of inhabited species., , This is the most important cause of, of biodiversity loss, e.g., the tropical, rainforest once covering 14% surface, of earth, now covers not more than 6%., After removal of these habitats, the, harbouring species also lost., , Overexploitation, The human dependency on, nature for food, shelter turns, into ‘‘greed’’ ‘‘need’’ which, in turn led to heavy loss of, natural resources, i.e., biodiversity., , Factors causing biodiversity loss, , Biodiversity Conservation, Conservation means protection, upliftment and scientific, management of biodiversity so as to maintain it at its optimum level, and derive sustainable benefits for the present as well as future, strategies., The following are the three major reasons to conserve biodiversity, Narrow utilitarian The useful human products like food, fibres,, drugs and medicines are obtained from biodiversity., Broadly utilitarian Biodiversity provides ecosystem services like, providing oxygen, pollinating crops and controlling floods and erosions, etc., Ethical utilitarian Every living species has an intrinsic value,, though it may not have direct economic value and also every species, has right to live., , Methods of Biodiversity Conservation, Some main strategies of conservation are as follows, (i) All the threatened species should be protected. Priority should be, given to ones belonging to the monotypic genera, endangered over, vulnerable, vulnerable over rare and rare over other species., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biodiversity and Conservation, 611, (ii) All the possible varieties (old or new) of food, forage and timber, plants, medicinal plants, livestock, aquaculture animals,, microbes should be conserved., (iii) Wild relatives of economically important organisms should be, identified and conserved in protected areas., (iv) Critical habitats for feeding/breeding/resting/nursing of each, species should be identified and safeguarded., (v) Resting/feeding places of migratory/wide ranging animals, should be protected, pollution controlled and exploitation, regulated., (vi) National Wildlife Protection Law should be enacted (in India,, 1972), wildlife protection strategies should be formulated (1983), and protection programmes should be integrated with the, international programmes., (vii) Ecosystems should be prioritised., (viii) The reproductive capacity of the exploited species and, productivity of the ecosystem should be determined., (ix) International trade in wildlife should be highly regulated., (x) Development of reserves or protected areas should be initiated., (xi) Introduction of new species should be in strict control of, regulatory laws., (xii) Pollution reduction and public awareness should be promoted., Biodiversity Conservation, , In situ, , Ex situ, , It is the conservation of living resources, through their maintenance within the, natural ecosystem in which they occur., , It means the conservation outside the, habitats by perpetuating sample, population in genetic resource centre,, e.g., zoos, botanical gardens, etc. These, can also be categorised as, , Protected areas network, Hotspots, , Sacred lands, Biosphere, and groves reserves, , Terrestrial, , National, parks,, wildlife, sanctuaries, , Sacred plants, Seed banks,, home garden gene banks,, cryopreservation, , Marine, , www.aiimsneetshortnotes.com, , Botanical garden,, Arborata, zoological, gardens, aquaria
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612, , Telegram @neetquestionpaper, , Handbook of Biology, , The detailed description of these protected areas is given below, , 1. Hotspot, The concept of hotspot was given by Norman Myers in 1988. Hotspots, are the areas that are extremely rich in species diversity, have high, endemism and are under constant threat., Among the 34 hotspots (cover less than 2% of earth land area) of the, world, two are found in India extending into neighbouring countries, The Western Ghats/Sri Lanka and the Indo–Burma Region, (covering the Eastern Himalayas also known as cradle of speciation)., The key criteria for determining a hotspot are as follows, (i) Number of endemic species, i.e., the species which are found, nowhere else., (ii) Degree of threat which is measured in terms of habitat loss., , Hotspots in India, The two hotspots in India are as follows, (i) Eastern Himalaya, , The Eastern Himalayan hotspot extends to the North-Eastern India, and Bhutan. The temperate forests are found at altitudes of 1,780 to, 3,500 metres. Many deep and semi-isolated valleys found in this region, are exceptionally rich in endemic plant species., Besides being an active centre of evolution and rich diversity of, flowering plants, the numerous primitive angiosperm families (e.g.,, Magnoliaceae and Winteraceae) and primitive genera of plants, like, Magnolia and Betula, are found in Eastern Himalaya., (ii) Western Ghat, , The Western Ghats region lies parallel to the Western coast of Indian, Peninsula for almost, 1600 km, in Maharashtra, Karnataka, Tamil, Nadu and Kerala., The forests at low elevation (500 m above mean sea level) are mostly, evergreen, while those found at 500-1,500 metres height are generally, semi-evergreen forests. The Agasthyamalai hills, the Silent valley and, the new Amambalam reserve are the main centres of biological, diversity., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biodiversity and Conservation, 613, 2. Wetlands, These are an integral part of the watersheds and generally lie at the, interface between the land and water. On the basis of their function of, filtering water before entering into the large water bodies, they are, also known as ‘kidneys of ecosystem’., A convention for the protection of wetlands held in Ramsar on 2nd, February 1972, since then 2nd February was celebrated as World, Wetland Day., In India, there are 26 Ramsar sites present., , 3. National Parks of India, India’s first national park (IUCN Category-II Protected area) was, Hailey National Park, now known as Jim Corbett National Park,, established in 1935. By 1970, India had only five national parks., In 1972, India enacted the Wildlife Protection Act and Project, Tiger to safeguard habitat. Further, Federal Legislation strengthening, the protections for wildlife was introduced in the 1980s. As on April, 2012, there are 102 national parks., Some important national parks of India are mentioned in the following, table with their belonging states, Some National Parks in India, Name, Bandipur National Park, , State, Karnataka, , Bannerghatta National Park, , Karnataka, , Bhitarkanika National Park, , Odisha, , Buxa Tiger Reserve, , West Bangal, , Corbett National Park, , Uttarakhand, , Dachigam National Park, , Jammu and Kashmir, , Dibru-Saikhowa National Park, , Asom, , Gir National Park, , Gujarat, , Great Himalayan National Park, , Himachal Pradesh, , Gugamal National Park, , Maharashtra, , Hemis National Park, , Jammu and Kashmir, , Indravati National Park, , Chhattisgarh, , Intanki National Park, , Nagaland, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 615, Biodiversity and Conservation, Some important sanctuaries of India are given in following table, Some Important Sanctuaries in India, Name and Location, , Area, (in sq km), , Key Vertebrate Species being, Protected, , Chilka Lake (Odisha), , 990, , Flamingoes, sandpipers, ducks, water, fowls, cranes, golden plovers and, ospreys., , Keoladeo Ghana, , 29, , Migratory birds Siberian crane, spoon, bill, herons, egrets and variety of other, local birds., , Bird Sanctuary, (Rajasthan), , Mammals Blue bull, wild boar, black, buck and spotted deer., Reptiles Python., Mudumalai Wildlife, Sanctuary, Nilgiri (Tamil, Nadu), , 520, , Mammals Flying squirrel, porcupine,, elephant, sambhar, cheetal, barking deer,, mouse, deer, four-horned antelope, giant, squirrel, wild dog, cat and civet., Reptiles Rat snake, python, flying lizard, and monitor lizard., , Manas Wildlife Sanctuary,, Kamrup (Asom), , —, , Tiger, wild boar, sambhar, golden, langoor, one-horned rhino, panther,, swamp deer, wild dog and wild buffalo., , Periyar Sanctuary (Kerala), , 777, , Mammals Elephants, leopard, black, langoor, sambhar, gaur, bison., Birds Egret and horn bills., , Sultanpur Lake Bird, Sanctuary (Uttar Pradesh), , 12, , Birds Cranes, duck, green pigeon, drake, and spot bill., Reptiles Python and crocodile., , 5. Biosphere Reserves, These are special protected areas of land and/or coastal environments,, wherein people are an integral component of the system. These are the, representative examples of natural biomes and contain unique, biological communities within. They represent a specified area zonated, for particular activities., These consist of, Core zone No human activity is allowed in this zone., Buffer zone Limited activity is permitted., Manipulation zone Several human activities are allowed., l, , l, , l, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biodiversity and Conservation, 617, 7. Botanical Gardens, These play an important role in the conservation of plant species as, that there are several instances when plants believed to be extinct,, were found living only in a botanical garden. Sophora toromiro is the, famous example., Record of threatened plants that are in cultivation have been kept in, Green Books. The Indian Green Book prepared by BSI which lists, 100 such species which are rare, endangered or endemic, but all are, growing in a living state in various botanical gardens., With the help of above measure, we can easily protect the biodiversity, present all around us. The protection of biodiversity cannot be only, accomplished by government organisation, but it is the cumulative, responsibility of every individual., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 38, Environmental, Issues, Humans have always inhabited two worlds. One is the natural, world of plants, animals, soil, air and waters that preceded us by, billion of years and of which, we are a part. The other is the world of, social institutions and artifacts that we create for ourselves using, science, technology and political organisation., Where earlier people has limited ability to alter their surroundings, we, now have power to extract and consume resources, produce wastes, and modify our world in a way that threatened both our continued, existence and that of many organisms with which we share the planet., Environmental issues include the aspects which adversely affect our, biophysical environment. Pollution, global warming, deforestation, etc.,, are the topics of major concern in current perspective., , Pollution, Pollution is the addition of the harmful agents to the ecosystem, which, has detrimental effects on it. Environmental pollution is any discharge, of materials or energy into air, water or land that may cause acute, (short term) and chronic (long-term) effects on the earth’s ecological, balance or may lower the quality of life., Pollution can be defined by different organisations differently., Some of these are as follows, World Health Organisation (WHO) has defined that ‘Pollution is the, introduction of harmful materials into the environment’., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 619, Environmental Issues, According to Central Pollution Control Board (CPCB), ‘Pollution means, contamination of water, air and land in such a way that alters the, physical, chemical and biological property of that resource’., Ministry of Environment and Forest (MOEF) defined pollution as, ‘Introduction of different harmful pollutants into certain environment, that makes it unhealthy to live in’., , Pollutants, Pollutants are chemicals or biological substances that deteriorate our, natural environment., Types of Pollutants, , On the basis of their, chemical nature, , On the basis of, existence in nature, , On the basis of, natural degradation, , Organic pollutants, e.g., DDT, oils, etc., , Quantitative pollutants, e.g., CO2 , etc., , Inorganic pollutants, e.g., nitrates, metals, etc., , Qualitative pollutants, e.g., pesticides, etc., , On the basis, of persistence, , Acid pollutants e.g., runoff from coal mining, Radiological pollutants, e.g., radioactive, chemicals found, in soil, rocks, etc., , Biodegradable, e.g., sewage, , Biological pollutants, e.g., bacteria, virus, etc., Multiple pollutants e.g., xenobiotics, , Non-biodegradable, e.g., DDT, BHC, etc., , Secondary pollutants, e.g., O3 , PAN, etc., , Primary pollutants, e.g., DDT, CO2 , etc., , Physical pollutants e.g., soil carried in rainwater., , Types of Pollution, On varions basis pollution can be categorised as, Pollution, On the basis of, part of environment, where it occurs, , On the basis, of its origin, , Air pollution, Water pollution, Land pollution, Genetic pollution, etc., , On the basis, of physical nature, of pollutant, , Natural, e.g., volcanic, eruptions, etc., Anthropogenic, e.g., fossil fuel, burning, mining,, etc., , On the basis, of emission of, pollutants, , Gaseous pollution, Dust pollution, Thermal pollution, Noise pollution, Radioactive pollution, , www.aiimsneetshortnotes.com, , Point source, pollution, Line source, pollution, Area source, pollution, Diffuse source, pollution, Fixed source, pollution, Mobile source, pollution
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620, , Telegram @neetquestionpaper, , Handbook of Biology, , Air Pollution, It is an undesirable change in the natural characteristics of the, atmosphere due to contamination of indoor and outdoor environment, by any chemical, biological or physical agent., , Sources of Air Pollution, Various air pollutants and their originating causes are given in the, following figure, Photochemical Products, Photolysis of NOx, O3 and, hydrocarbons from PAN,, PBN (Peroxybenzoyl Nitrate),, Benzpyrene., , Smog, Sunlight + smoke + fog, , Oxides of Nitrogen, Automobile exhaust and, some chemical industries., Carbon Monoxide, Automobile exhaust., , Toxicants and Heavy Metals, Metallurgical operations, (Hg, Ni, Pb, Cd)., , Sulphur Dioxide, Combustion of fossil, fuels, Smelting of ores., , Smoke, Incomplete combustion of carbonaceous, material, smoke stacks of thermal power, plants., Spray, Mechanical disintegration, processes, , Fume, Particles of metals and metal, oxide formed by condensation of, vapour by sublimation, etc., , Dust (SPM), Raw dust from woodworks,, sands from sandblasting., , Sources, of Air, Pollution, , Hydrogen Sulphide, Industrial effluents., , Hydrogen Fluoride, Laundry, fertilisers,, aluminium smelting, industries., , Aldehydes and Organic Acids, Incomplete combustion of, petroleum, etc., , Secondary Pollutants, NO2, O3,,N2 O5, RCOOH,, HCO3, photochemical reactions, of primary pollutants., , Chief air pollutants and their sources, , The six types of air pollutants that account for the most of the air, pollution are called criteria air pollutants., , Effects of Air Pollution, The air pollution has following effects on various organisms, , 1. Effects on Humans, The following table provides the list of various air pollutants and their, effects on human body, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Environmental Issues, 621, Common Air Pollutants and their Effects on Human Body, Pollutants, , Effect on Human Body, , Aldehydes, , Irritate nasal and respiratory tract., , Ammonia, , Inflames upper respiratory passage., , Arsenic, , Breakdown of red cells in blood, damage to, kidneys, causes jaundice, lung and skin cancer., , Carbon monoxide, , Reduces O2 carrying capacity of blood., , Chlorine, , Attacks entire respiratory tract and mucous, membrane of eyes, causes pulmonary oedema., , Cyanides, , Interfere with nerve cells, resulting in dry throat,, indistinct vision, headache., , Fluorides, , Irritate and corrode all body passages, cause, osteoporosis., , Sulphides, , Cause nausea, irritate eyes and throat., , Nitrogen oxides, , Inhibit ciliary action of nose, cause bronchitis., , Phosgenes (carbonyl chloride COCl2 ), , Induce coughing, irritation and sometimes fatal, pulmonary oedema., , Sulphur, , Causes chest constriction, headache, vomiting, and death from respiratory ailments., , Suspended particles (ash, soot,, smoke), , Cause emphysema, eye irritation and possibly, cancer., , 2. Effects on Plants, Air pollution also causes several damages to plants., These are listed below, Injury Thresholds and Effects of Air Pollutants on Plants, Pollutant, , Effect on Plants, , Concent, ration, (ppm), , Sustained, Exposure Time, , Ozone (O 3), , Flecks, bleaching, bleached, spotting, growth suppression. Tips, of conifer needles become brown, and necrotic., , 0.03, , 4h, , Sulphur dioxide, (SO2 ), , Bleached spots, bleached areas, between veins, chlorosis, growth, suppression, reduction in yield,, leaf curling., , 0.03, , 8h, , 0.01, , 6h, , Peroxyacetyl Nitrate Glazing silvering or bronzing on, (PAN), the lower surface of leaves., , www.aiimsneetshortnotes.com
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622, , Telegram @neetquestionpaper, , Handbook of Biology, , Pollutant, , Effect on Plants, , Concent, ration, (ppm), 0.0001, , Sustained, Exposure Time, , Hydrogen Fluoride, (HF), , Chlorosis, dwarfing, leaf, abscission, lower yield., , 5 weeks, , Chloride (Cl2 ), , Bleaching between veins, tips and, leaf abscission., , 0.01, , 2h, , Ethylene (C 2H 4 ), , Withering, leaf abnormalities,, flower drooping and failure of, flower to open., , 0.05, , 6h, , 3. Effects on Climate, Air pollution causes acid rain. The acid rain has various negative, effects. The effects of acid precipitation can be categorised as, Effect on Climate, Effects on, Aquatic Life, , Effects on, Forest, , Acidic deposition adversely, affects the aquatic life by making, water acidic. The ponds in which, the biodiversity reduces at, significant level, are called, ‘Biologically dead’., , Effects on, Building and Monuments, , Acid deposition negatively, affects the forests., The red spruce forest in, tropical areas are killed, severely., , The oldest building, and monuments all, over the world are, destroyed by atmospheric, acids at an alarming rate., , Effects of air pollution on climate, , Control of Air Pollution, Several methods are used to control air pollution., Some of them are as follows, , 1. Use of High Chimneys, For proper escaping of smoke, fumes and heated air, the industrial, plants should have high chimneys., , 2. Government’s Norms for Emission, In the line of world standard, Government of India also has formulated, new fuel policies., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Environmental Issues, 623, These fuel policies with their applicable regions are given below, Standard, India 2000, , Bharat stage II, , Reference, Euro 1, , Euro 2, , Date, 2000, , Nationwide,, , 2001, , NCR*, Mumbai, Kolkata, Chennai, , 2003. 04, , NCR*, 10 cities ^, Nationwide, , 2005. 04, Bharat stage III, , Bharat stage IV, , Euro 3, , Euro 4, , Region, , 2005.04, 2010.04, , NCR*, 10 cities ^, Nationwide, , 2010.04, , NCR*, 10 cities ^, , * National Capital Region (Delhi), ^ Mumbai, Kolkata, Chennai, Bangaluru, Hyderabad, Ahmedabad, Pune, Surat, Kanpur, and Agra, , 3. Other Control Measures to Control Air Pollution, These methods are characterised on the basis of physical nature of, pollutants., (i) Methods to Control Particulate Pollutants, Different technological equipments are used to control particulate, pollution. These are, (a) Cyclonic separator In this, centrifugal force causes the, settling of particulate matters., (b) Trajectory separators In this, heavier particles settle down,, when dirty air is passed from a chamber as an oblique jet., (c) Electrostatic precipitator Particulate matter present in, dirty air are charged electrically and passed through a chamber, where these particles loose their charges and settle down., (d) Filters Particulate matter get filtered out by passing dry, emissions under pressure through polyester, teflon and, polyamide bags which are large sized and porous., , www.aiimsneetshortnotes.com
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624, , Telegram @neetquestionpaper, , Handbook of Biology, , (ii) Methods to Control Gaseous Pollutants, , The gaseous pollution can be inhibited by following set of methods, Adsorption, Technique, The toxic gases, from dirty air are, removed by very, fine solid particles, (e.g., charcoal)., , Combustion, Technique, , Absorption, Technique, , The emission are, burnt at high, temperature to, remove gaseous, pollutants., , Scrubber, The exhaust is, passed through, The packing, materials, fixed a spray of water, in scrubber are or lime to remove, used to absorb gases like SOx., the gaseous, pollutants., , Catalytic, Converter, It contains, expensive metals, like Platinum,, Palladium and, Rhodium as the, catalyst. After passing, through it, unburnt, hydrocarbons are, converted into CO2, and water., , Water Pollution, Water is said to be polluted when its quality gets degraded due to the, addition of various inorganic, organic, biological and radiological, substances, which make it unfit and a health hazard., Impurities in the form of variables are as follows, Chemical, It includes all possible, inorganic and organic, substances, such as, chlorides, sulphates, nitrates, nitrites, boron, heavy metals,, pesticides, phenol, cyanide, oil,, etc., ions concentrations, BOD, and COD, etc., of water., , Physical, It includes appearance,, temperature, turbidity,, colour, odour and, taste, etc., , Water, Quality, Variables, , Biological, The presence of all flora, and fauna in water at a, particular time., , Categories of water pollutants, , The comparative account of Biochemical Oxygen Demand (BOD) and, Chemical Oxygen Demand (COD) is given as, Comparison of BOD and COD, Biochemical Oxygen Demand, (BOD), It is the amount of oxygen used for, biochemical oxidation by, microorganisms in a unit volume of, water., , Chemical Oxygen Demand, (COD), It is the amount of oxygen required by, organic matter in a sample of water for its, oxidation by a strong chemical oxidant and is, expressed as ppm of oxygen taken from the, solution of potassium dichromate in 2 hours., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 625, Environmental Issues, Biochemical Oxygen Demand, (BOD), , Chemical Oxygen Demand, (COD), , BOD value approximates the amount of, oxdisable organic matter and therefore,, used as a measure of degree of water, pollution and waste., , This value is a poor measure of strength of, organic matter, as oxygen is also consumed, in the oxidation of inorganic matter such as, nitrates, sulphates, reduced metal ions and, also that some organic molecules such as, benzene, pyridine and few other cyclic, organic compounds which are not oxidised by, this test., , BOD test is influenced by many factors, such as types of microorganisms, pH,, presence of toxins, some reduced, mineral matter and nitrification of, microorganisms., , Presence of toxins and other such, unfavourable conditions for the growth of, microorganisms does not affect COD values., , Sources of Water Pollution, The various sources of water pollution can be explained through the, following diagram, Industrial, , Fertilisers and, Farm Wastes, Runoff from, agricultural fields., , Paper and Pulp Free chlorine., Textile Minor acids, fats, oils and grease., Food processing Starch., Chemical Mineral acids, NH3, tartaric acid and nitro compounds P, S, F., Metal Fluorides, cyanogen and limestone are called nuisance., Petroleum Hydrocarbons, phenols and fats., Tanneries Sulphide, chromium, phenol and tannic acid., Acid and Grease Bad taste and odour to H2O., Battery Lead mineral acids., Wool Scouring Alkalis, fats, oils and grease., Acids, HNO3, H2SO4., , Synthetic Detergents, Washing clothes, near water bodies., , Dyes, Chemical industries., , Household Wastage, and Sewage, Include carbohydrates,, proteins, sugars, starch,, cellulose, dextrin, glycogen,, alginic acid, etc., , Sources of, Water, Pollution, , Pesticides, Include DDT, 2, 4-D, TEPP,, aldrin, BHC, parathion., , Toxic Metal, Pb, Zn, Ar, Cu, Cd, Hg, Ni from, electroplating, chemical and copper, pickling industries., , Fats, Soaps and Waxes, Food and household industries., Gaseous Pollutants, NH3, Cl, H2S, O2,, phosphine, etc., Oils, Tanks, machines, lubricants,, factories and refineries waste., , Water pollutants and their sources, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 626, , Handbook of Biology, , Effects of Water Pollution, Water pollution affects individuals severely and causes various, diseases, which depend upon the nature of pollutants., Chief pollutants and their toxic effects are given in the following table, Some Elements and their Toxic Effects in Humans, Elements, , Toxic effects, , Aluminium, , Interferes with phosphate metabolism, inhibits absorption of, fluorides, Ca and iron compounds., , Arsenic, , Loss of appetite, copious secretion of mucus in respiratory, tract, black foot disease., , Cadmium, , Itai-itai disease (Japan), kidney damage., , Fluorine, , Fluorosis, about 5-12 ppm is toxic, enamel becomes brittle,, bones lose their elasticity and are prone to fractures, impairs, glycolysis, knock-knee disease., , Lead, , Anaemia and mental retardation due to degenerative, changes in motor nerves., , Mercury, , Minamata disease, main site of injury is CNS leading to, tremors inability to coordinate, impairment of vision and loss, of hearing. Two major episodes of mercury poisoning have, occurred in Japan, in Minamata bay and Niigata., Mercury was absorbed, bioaccumulated and biomagnified to, high levels. Fish collected from this bay had 10-12 mg of, Hg per kg of their flesh and bones. The largest mercury, epidemic occurred in 1971-72 in lraq, when 6000 people, were affected and 500 died; infertility in human., , Control of Water Pollution, Water pollution can be controlled through various measures, some of, them are discussed here, (i) Reduced use of pesticides and chemical fertilisers in, agriculture., (ii) Avoid the disposal of waste into water., (iii) Proper sewage treatment before disposal into large water, bodies., (iv) Control of disposal of industrial waste into water., (v) Proper maintenance of water bodies., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Environmental Issues, 627, Special Cases of Water Pollution, Eutrophication and biomagnification are two special cases of water, pollution., , Eutrophication, Eutrophic (eu + trophic = truely nourished) waters are rich in organisms, and organic materials. Eutrophication is an increase in nutrient, level and productivity., As with BOD, eutrophication often results from nutrients enrichment., Sewage, fertiliser runoff and other human activities cause increase in, biological productivity which is called cultural eutrophication., The schematic representation of eutrophication is given below., Sewage, disposal, Fertilisers, runoff, Biodegradation, , Elevated, phosphorus, and nitrogen, levels., , Collapse, of aquatic, ecosystem., , Increased, growth of, blooms and, bacterial population., Plants, animals, and algae die,, decomposers, deplete O2 level., , Consumption of, O2 from water., , Water becomes turbid,, unpleasant and cloudy., , Events of eutrophication, , Algal Bloom, The presence of large amount of nutrients in water causes excessive, growth of algae which is known as algal bloom. It imparts distinct, colour to the water bodies and causes deterioration of water quality., , Biomagnification/Bioaccumulation, Many pesticides such as DDT, aldrin and dieldrin have a long life in, the environment. These are fat soluble and generally non-biodegradable., After incorporation into food chain, they get magnified and, accumulated in higher trophic level. The process of biological, magnification is also reported for certain other pollutants such as, lead (Pb), mercury (Hg), copper (Cu) and strontium-90., The diagrammatic representation of bioaccumulation is shown below., , DDT levels, , Water, , Microscopic, Aquatic, Organisms, , Small, Fishes, , Large, Fishes, , Fish Eating, Birds, , 0.000003 ppm, , 0.04 ppm, , 0.5 ppm, , 2.0 ppm, , 25.0 ppm, , www.aiimsneetshortnotes.com
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628, , Telegram @neetquestionpaper, , Handbook of Biology, , Soil Pollution, It is defined as the build up in soils of persistent toxic compounds,, chemicals, salts, radioactive material and disease causing, agents which have adverse effects on health of inhabiting organisms., It can be of following two types, (i) Negative soil pollution It is the reduction in soil productivity, due to erosion and overuse., (ii) Positive soil pollution It is the reduction in soil, productivity, because of addition of undesirable substances like, fertilisers into soil., , Sources and Effects of Soil Pollution, The chief agents of soil pollution and their effects on soil are presented, diagrammatically below., Biological Agents, , Industrial and Urban Waste, , Excreta of humans, animals and birds is the, major one., Pathogenic organisms are, (i) Bacteria, fungi and parasitic, worms, etc., (ii) Excreted by animals, cow, pig, sheep,, etc.,, (iii) Naturally found in soil due to some, edaphic cause., Diseases caused by these, agents are dysentery, cholera,, typhoid,etc., , Examples of industrial and urban wastes are, (i) Coal and mineral mines, metal processing, industries and engineering industries., (ii) Domestic and community wastes, i.e., sludge., (iii) Garbage, rubbish materials such as paper,, residues from home, fuels, street sweepings,, glasses, rubber and abandoned vehicles, etc., Dumping of solid wastes not only creates, aesthetic problems but also public health problems., , Sources of, Soil Pollution, , Radiological Agents, , Agricultural Practices, , From nuclear explosion and radioactive, wastes (nuclear testing and laboratories), like ruthenium 106, rhodium 106, iodine, 131, barium 140, lanthanium 140, cerium, 144, promethium 144, carbon 14, cesium 137,, create several serious health hazards,, e.g., cancer., , Fertilisers, pesticides, soil condition,, fumigant and other chemical agents., Farming phosphates, nitrates, DDT,, BHC, endrin, aldrin, dieldrin,, organosulphurous compounds,, organic compounds with Pb, Hg,, Ar are toxic to plants. Lindane has, been reported to, taint carrots., Flies, insects and rodents multiply, which in turn harm the crop., , Various factors causing soil pollution, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Environmental Issues, 629, Control of Soil Pollution, The control of soil pollution can be done through following steps, (i) It involves safer land use, planned urbanisation, controlled, developmental activities, safe disposal and the management of, solid wastes., (ii) In recovering and recycling some waste items like plastics, tin, cans, other metals, glass, polyethylenes, rags, papers, etc., are, picked up by rag pickers for recycling. All these items are, recycled in recycling units to make new items. This reduces soil, pollution., (iii) To reduce soil pollution solid waste is sometimes disposed off by, burning. The methods of burning are, (a) Incineration Carried out at very high temperature,, i.e, 900-1300°C., (b) Pyrolysis It is combustion at temperature 1650°C in the, absence of oxygen., , Noise Pollution, Noise is defined as any loud disturbing sound released into the ambient, atmosphere. It is measured by a sound meter and is expressed in a unit, called decibel (dB). Any value more than 80 dB causes noise pollution., , Sources of Noise Pollution, There are as follows, Bull dozing,, stone crunching,, etc., , Crackers, , Dynamite, blasting, , Transport, automobiles, , Sources of Noise, Pollution, , Public address, systems like, loudspeakers, , Industries like textile, mills, construction, sites, etc., , Agricultural machines, like tractors, tubewell,, etc., , Defence equipments, like tanks, explosions,, etc., , Effects of Noise Pollution, l, , l, , l, , May cause a partial or permanent loss of hearing., Can impair the development of nervous system of unborn babies., Hatching of birds is disturbed., , www.aiimsneetshortnotes.com
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630, , Telegram @neetquestionpaper, , Handbook of Biology, , Control of Noise Pollution, l, , l, , l, , Volume of loudspeakers should be kept low., Traffic police personnel and factory workers exposed to high noise, pollution should be provided with the ear plugs or ear muffs., Green belt vegetation should be maintained to serve as noise, absorbers., , Thermal Pollution, It is the degradation of water quality by any process that changes the, whole water temperature., It can also be defined as ‘warming up of an aquatic ecosystem to the, point where desirable organisms are adversely affected’ (Owen, 1985)., , Causes of Thermal Pollution, Major sources of thermal pollution are many industries, thermal power, plants, oil refineries, etc. The use of coolants and boilers in thermal, power plants is an important cause of thermal pollution., , Effects of Thermal Pollution, Harmful effects of thermal pollution on aquatic ecosystems are as follows, (i) Reduction in dissolved oxygen., (ii) Interference with reproduction of aquatic animals., (iii) Increased vulnerability to diseases., (iv) Direct mortality., (v) Invasion of destructive organisms., (vi) Undesirable changes in algal population., (vii) Elimination of flora and fauna of cold water., , Radioactive Pollution, The release of radioactive material into environment is called, radioactive pollution. This is very dangerous as radiation can mutate, the DNA which causes abnormal growth and sometimes cancer. The, radiation remains in atmosphere for years, slowly diminishing over, times., , Causes of Radioactive Pollution, There are many causes of radioactive pollution. The most important, one is inappropriately disposed radioactive wastes., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Environmental Issues, 631, Some, (i), (ii), (iii), (iv), (v), (vi), (vii), , of these causes are as follows, Production of nuclear weapons, Decommissioning of nuclear weapons, Medical waste, Mining of radioactive ores, Coal ash, Nuclear power plants, Nuclear tests, , Effects of Radioactive Pollution, The nuclear radiations cause genetic variation (i.e., mutation) and, cancer in exposed organs or body parts. These radiations affect the, future generations as it can alter the DNA composition permanently., , Solid Wastes, These wastes are left over that goes out in trash. The various sources, of solid wastes are municipal waste, mining waste, hospital waste,, defunct ships, electronic wastes (e-wastes), etc., Different modern industries are releasing large amount of solid wastes, which need to be managed in proper way to avoid environmental loss., , Control of Solid Wastes, There are various controlling measures of solid wastes, some of them, are discussed below, (i) Dumping or landfilling is pilling of waste on selected low lying, land. Open landfilling is dumping of waste material on, uncovered low lying area. The waste is burnt periodically or, compressed at intervals. In sanitary landfilling, wastes are, dumped in a depression or trench after compactions and covered, with dirt everyday., Most importantly the solid wastes can be treated after separation, into three types, (a) Biodegradable (b) Recyclable (c) Non-biodegradable, (ii) E-wastes are treated scientifically in an environment friendly, manner and then either buried in landfills or incinerated., (iii) Other methods of disposing wastes are source reduction,, composting, recovery and recycling., (iv) Ahmed Khan in 1998, developed polyblend, a fine powder of, recycled modified plastic, which can be used for road carpeting, when mixed with bitumen in Bengaluru., , www.aiimsneetshortnotes.com
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632, , Telegram @neetquestionpaper, , Handbook of Biology, , Consequences of Pollution, Greenhouse Effect (GHE), It was first described by Fourier in 1827., It is defined as ‘The trapping of solar radiation by a layer of, Greenhouse Gases (GHGs), which is important for the maintenance of, habitable temperature on earth’., Greenhouse Effect (GHE) is a positive concept as it is needed for, existence of life on earth and in the absence of it, the temperature of, earth would be –18° C., , Causes of GHE, The greenhouse effect is caused by several gases. The share of, greenhouse effect by different sources are given in following figure, , Transportation, 14.3%, , Waste, 3.2%, , Agriculture, 13.8%, Land use, change, 12.2%, , Electricity, and heat, 24.9%, , Industrial, processes, 4.3%, Fugitive, emission, 4.0%, Other fuel, combustion, 8.6%, , Industries, 14.7%, , Annual global greenhouse gas emission in, 2010, by different sectors, , Despite their differential concentrations, different gases cause varied, level of greenhouse effects. This is called differential greenhouse, effect., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Environmental Issues, 633, Differential greenhouse effect caused by various substances is shown in, the following figure, Greenhouse Effect, 60%, , Carbon dioxide, (CO2), , Acid Rain, , Sulphur dioxide, (SO2), , 6%, , Nitrous oxide, (N2O), , 20%, , 14%, , Hydrocarbons,, e.g., methane (CH4), , Chlorofluorocarbons (CFCs), , Photochemical Smog, Depletion of Stratospheric Ozone (O3), , Differential greenhouse effect, , The greenhouse effect is increasing day by day with increasing, concentration of these substances into the environment. Chief, greenhouse substances and their brief descriptions are as follows, Carbon Dioxide (CO2), , Methane (CH4), , Present level in atmosphere is 380 ppm, (parts per million)., Atmospheric lifetime is 5-200 yr., It is increasing due to fossil fuel’s burning,, deforestation and change in land use., High concentration may cause, fertilisation effect, i.e., increase in the, rate of photosynthesis and growth of, plants, decrease in stomatal, conductance and transpiration rate., , Present level in atmosphere is, 1750 ppb (parts per billion)., Methanogen bacteria increase, greenhouse effect by producing, methane., The major sources are freshwater, wetlands, enteric fermentation in, cattle. Flooded rice fields along with, biomass burning., , Greenhouse, Gases (GHGs), Nitrous Oxide (N2O), Present atmospheric concentration is, 316 ppb (parts per billion)., Major sources are agriculture, biomass, burning, nylon industries, nitrogen rich, fertilisers and fuels., , Chlorofluorocarbons (CFCs), Present atmospheric concentration is, 282 ppt (parts per trillion)., Atmospheric life is 45-260 yr., Major sources are leakage from air, conditioners, refrigeration units, evaporation, of industrial solvents, production of plastic, foams and propellants in aerosol, spraycans., , Chief greenhouse gases, their sources and effects, , www.aiimsneetshortnotes.com
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634, , Telegram @neetquestionpaper, , Handbook of Biology, , In most scenarios, emissions continue to rise over the century, while in, a few, emissions are reduced. Over the last three decades of 20th, century, GDP per capita and population growth were the main driving, factors in greenhouse gas emissions., , Global Warming, The gradual continuous increase in average temperature of the surface, of earth as a result of increase in the concentration of greenhouse gases, is termed as global warming., The global average surface temperature rose 0.6 - 0.9° C (1.1-1.6°F), between 1906 and 2005 and the rate of temperature increase has, doubled in the last 50 years., Returning insolation of very high, wavelength, fail to cross the layer, formed by greenhouse gases, (i.e., trapped)., , Incoming insolation, of very low wavelength, comes to earth surface, , Earth, Trapped insolation, again returned to, earth’s atmosphere, and causes global, warming., , The layer of greenhouse gases, formed and thickened by GHGs., After thickening, it traps returning, sun rays in high amount and makes, the earth’s environment warmer., , Schematic representation of global warming, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 635, Environmental Issues, Effects of Global Warming, Various effects of global warming are as follows, (i) The temperature of the earth has increased by 0.6° C in last, three decades, which will lead to changes in precipitation, patterns., (ii) Rise in temperature leads to deleterious changes in, environment resulting in odd climatic changes called El Nino, effect., (iii) The rise in temperature will lead to the increased melting of, polar ice caps, which will cause the rise in sea level and many, coastal areas will be submerged., (iv) Increased temperature will lead to increased weed growth,, eruption of diseases and pests. Thus, crop productivity will, decrease., , Steps to Control Global Warming, (i) Kyoto (Japan) hosted an international conference from, December 1-10, 1997 of G-77 (a group of 140 developing, countries) to discuss global warming., (ii) To assess the role of human activities in climate change, the, World Meterological Organisation (WMO) and United, Nations Environment Programme (UNEP) set-up an, Intergovernment Panel on Climate Change (IPCC) in 1988. The, IPCC and United Nations Framework on Climate Change, (UNFCC) that had reviewed the situation in October 1997,, submitted their report in Kyoto in Kyoto Protocol., (iii) Earth Day (22 April) It was founded by Gaylord Nelson, and organised by Danis Hayes. It marks the beginning of, environment consciousness with clear focus on reducing, pollution. The earth day network promotes environment, awareness and year round progressive action., , Acid Rain, It is a broad term referring to a mixture of wet and dry deposition from, the atmosphere containing higher than normal amount of nitric and, sulphuric acids., Acid rain occurs when these gases (SOx and NOx) react in the, atmosphere with water, oxygen and other chemicals to form various, acidic compounds., , www.aiimsneetshortnotes.com
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636, , Telegram @neetquestionpaper, , Handbook of Biology, , Acidic deposition occurs in two ways, i.e., wet and dry., Acid Deposition (acid rain), , Wet Deposition, , Dry Deposition, When acidic chemicals are deposited, in the form of dust or smoke and fall, to the ground through dry deposition., , It refers to acidic rain, fog and snow., They result when acidic chemicals in, air are blown into wet areas. The strength, of the effect depends upon the acidity of, water, chemistry and buffering capacity, of soil, etc., , Causes of Acid Rain, It may cause due to natural sources like volcanoes or by the, combustion of fossil fuel in which SOx and NOx get released., , Effects of Acid Rain, Acid rain have various adverse effects on several groups of organisms., The overall pH of water bodies and soil gets reduced by acidic rain., Acid deposition adversely affects both the floral and faunal biodiversity, in various ecosystems., Finally acid rain also causes the damage to several architecture and, buildings. It causes the process of mineralisation, especially in, limestone constructed buildings., , Ozone Layer Depletion, In the region of upper stratosphere (ozonosphere), 17-26 km above the, earth’s surface, exists a thin veil of renewable ozone (O3 ). This ozone, layer absorbs 99% of the harmful incoming UV radiations., The energy of radiation gets dissipated in the following reaction, O3 1, , O2 + [O], , Ozone is being depleted by several man-made chemicals called Ozone, Depleting Compounds (ODCs) or Ozone Depleting Substances, (ODSs), It was first detected by Farman et al. in 1984., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Environmental Issues, 637, The process of the formation and breakdown of ozone in stratosphere is, diagrammatically represented below., Natural ozone production in the stratosphere, The free oxygen atoms react, with diatomic oxygen molecules, to form ozone, , UV, , ra, di, at, io, n, , Ultraviolet radiation from, the sun strikes to a diatomic, oxygen molecule and, splits it into two, oxygen atoms, , Oxygen, Diatomic oxygen, atoms, molecule (O2), Destruction, Natural ozone destruction, in the stratosphere, , Ozone (O3), molecule, , Ozone absorbs ultraviolet light in the range of, 290-320 nanometers. This solar energy, breaks apart the ozone molecules, into diatomic oxygen, molecules and, ion, oxygen atoms, iat, d, ra Diatomic (O2), oxygen, UV, Oxygen, atoms, Ozone (O3), molecule, , Oxygen, atoms, , Ozone Diatomic oxygen, molecule, molecule, , Ozone production and destruction in nature, , Rather than a ‘hole’, ozone depletion is more a thinning, where ozone, level has decreased by 50% to 100%. Ozone loss is projected to, diminish gradually until around 2050, when polar ozone holes will, return to 1975 levels., Mechanism of ozone depletion is as follows, UV- C, CFCl3 , → CFCl2 + Cl, UV- C, CFCl2 , → CFCl + Cl, , Cl + O3 → ClO + O2, ClO + O3 → Cl + 2O2, , www.aiimsneetshortnotes.com
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638, , Telegram @neetquestionpaper, , Handbook of Biology, , Harmful Effects of Ozone Layer Depletion, Depletion of ozone leads to various direct and indirect effects, some of, them are discussed below, (i) Rain failure Due to depletion of ozone layer in stratosphere,, the temperature of earth increases and it will be responsible for, the failure of rainfall., (ii) Increase in radiation Reduction of O3 in stratosphere would, allow UV rays to reach the earth., (iii) Cancer Due to thinning of ozone layer, threat of skin cancer, (melanoma) may increase. A 5% decrease in stratospheric ozone, appears likely to lead 10-20% increase in skin cancer globally., (iv) High dose of UV-B causes inflammation of cornea (snow, blindness), cataract, etc., (v) Other effects include destruction of aquatic flora and fauna,, loss of immunity and epidemic proportions of cataracts., (vi) Increased UV radiation’s entry to earth’s atmosphere leads to, increased global warming., Note, (i) To protect ozone depletion, Montreal Protocol was signed in Montreal, (Canada) in 1967 (effective since 1989)., (ii) Dobson Unit (DU) It is a measurement of column ozone level. In tropics, it, is 250-300 DU year around., , Degradation by Improper Resource, Utilisation and Maintenance, Degradation of natural resources can occur, not just by the action of, pollutants but also by improper resource utilisation practices., , 1. Soil Erosion and Desertification, Topsoil is the most fertilie soil and it takes centuries to build. Improper, human activities can remove it, resulting in arid patches of land., Natural resources get degraded not only by pollutants, but also by, improper practices of their utilisation and maintenance. Soil erosion is, caused by human acitivities like overcultivation, unrestricted grazing,, deforestation and poor irrigation. All these practices lead to the, removal of topsoil. Desertification is also a major problem these days,, that occurs mainly due to urbanisation., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Environmental Issues, 639, 2. Water-Lodging and Soil Salinity, Irrigation without proper drainage of water leads to water-lodging in, the soil. It draws salt to the surface of the soil. Deposited salt starts, collecting at the roots of the plants and affect the plant growth and, productivity. It is extremely damaging to the agriculture., , Deforestation, It is the conversion of forest area to non-forested area., The prime reason for deforestation is increased demand of humankind, and its dependence on forest products. Jhum cultivation is such a, technique in which mostly tribal population slash and burn forests to, make it agricultural land. After some time, these populations move to, different place and do the same practice again, hence this agriculture, is also called shifting agriculture., , Effects of Deforestation, It causes loss of biodiversity, as it leads to habitat destruction, soil, erosion and sometimes desertification as well. Deforestation is also, responsible for increased concentration of CO2 in the atmosphere,, because trees use CO2 during photosynthesis., , Reforestation, It is the process of restoring forest that once existed, but was removed, at some point of time in the past., , Case Studies of Forest Conservation, (i) Amrita Devi Bishnoi in 1731 had shown exemplary courage by, hugging a tree and daring kings people to cut her first., Government of India recently instituted Amrita Devi Bishnoi, Wildlife Protection Award for individulals or communities,, which protect and save forests., (ii) Chipko movement was launched by Chandi Prasad Bhatt, and Sundar Lal Bahuguna against large scale falling of trees, by timber contractor in Uttarakhand hills., These all protection movements led to introduction of Joint Forest, Management (JFM) concept in 1980s for protecting and managing, forests., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , Appendix, 1. Planes of the Body, Different sections of the body are termed as anatomical planes (flat, surfaces) by the medical professionals. These planes are imaginary, lines vertical or horizontal, which are drawn through an upright body., The terms are used to describe a specific body part., Sagittal plane, Coronal plane, , Transverse plane, , Body Planes, , Coronal (Frontal) Plane, It is a vertical plane running from side to side. It divides the whole body, or any of its parts into anterior and posterior portions., , Sagittal (Lateral) Plane, It is a vertical plane running from front to back. It divides the body or, any of its parts into right and left sides. Median plane is a sagittal, plane that runs through the midline of the body., , Transverse Plane, It is a horizontal plane. It divides the body or any of its parts into upper, and lower parts., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 2. Comparison of Compound Microscope,, Transmission Electron and Scanning, Electron Microscope, Characteristics, , Compound, Microscope, , Transmission, E. Microscope, , Scanning, E. Microscope, , Resolution (Average), , 500 nm, , 10 nm, , 2 nm, , Resolution (Special), , 200 nm, , 0.5 nm, , 0.2 nm, , Magnifying Power, , Up to 1,500X, , Up to 5,000,000X, , ~ 100,000X, , Depth of Field, , Poor, , Moderate, , High, , Type of Object, , Living or non-living, , Non-living, , Non-living, , Preparation, Technique, , Usually simple, , Skilled, , Easy, , Preparation, Thickness, , Rather thick, , Very thin, , Variable, , Specimen Mounting, , Glass slides, , Thin films on copper, grids, , Aluminium stubs, , Field of View, , Large enough, , Limited, , Large, , Source of Radiation, , Visible light, , Electrons, , Electrons, , Medium, , Air, , High vacuum, , High vacuum, , Nature of Lenses, , Glass, , 1 electrostatic + a few, em. lenses, , 1 electrostatic + a few, em. lenses, , Focusing, , Mechanical, , Current in the, objective lens coil, , Current in the, objective lens coil, , Magnification, Adjustments, , Changing objectives, , Current in the, projector lens coil, , Current in the projector, lens coil, , Specimen Contrast, , By light absorption, , By electron scattering, , By electron absorption, , Light Microscope, Eyepiece, , Stage, , Objective lens, Specimen, Optical, condenser, Focusing, knob, , Transmission Electron, Microscope, Electron, gun, Condenser, Specimen, Objective, ‘lens’, , Scanning Electron, Microscope, Electron gun, , Electron beam, Electron, Condenser, beam, Scanning, electromagnets, Fluorescent, screen Detector, , Projector, ‘lens’, , Illuminator, , Viewing, binoculars, , Specimen, Fluorescent Amplifier, Secondary, screen, electrons, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Common Name, , Botanical Name, , Important Plant, Part, , Uses, , B. Spices and condiments, 1. Red pepper, (Chillies), , Capsicum sp., , Dried fruit, , Dried pepper is used as powder, with most of the Indian foods,, fresh also eaten., , 2. Black pepper (Kali, Piper nigrum, mirch = Black pearl), , Seeds, , Dried mature seeds used in, cooking., , 3. Turmeric (Haldi), , Curcuma domestica, , Rhizome, , Dried rhizome is very aromatic and, used to colour pickles, food stuffs, and also to prepare kumkum., , 4. Cumin (Zira), , Cuminum cyminum, , Fruits, , Aromatic fruits are used in soup,, curries, cakes, pickles, oil is used, for flavouring beverages and other, food stuffs., , 5. Coriander (Dhania), , Coriandrum sativum, , Fruits and leaves, , Fruits and leaves are aromatic,, used in making soup, pickles, etc., , 6. Clove (Laung), , Syzygium, aromaticum, , Flower bud, , Dried unopened flower buds are, very aromatic, fine flavoured and, imparts warming qualities., , 7. Saffron (Kesar), , Crocus sativus, , Stigma and style, , The dried stigma and tops of the, style make the saffron of, commercial use. It possesses, pleasant aroma, used as spice and, dye stuff., , 8. Cardamom (Chhoti, Ilaichi), , Elettaria, cardamomum, , Fruits and seeds, , Fruits and seeds are used for, flavouring, sweet, dishes,, beverages, etc., , 9. Bengal cardamom, (Badi Ilaichi), , Amomum, aromaticum, , Fruits and seeds, , Fruits and seeds are chief, ingredient of ‘garam masala’., , 10. Asafetida (Hing), , Ferula assafoetida, , Roots, , Resin obtained from the roots is, used for flavouring food products., , 1. Mungphali, Arachis hypogea, (Ground nut=Peanut, ), , Seeds, , Seeds yield edible oil, roasted, seeds eaten, oil cake used as cattle, feed and manure., , 2.(a) Rape, (b) Mustard, , Brassica napus, B. campestris, , Seeds, , Seed oil used for cooking, oil cake, a good manure and cattle feed., , 3. Til (Sesame), , Sesamum indicum, , Seeds, , Seeds yield cooking oil, oil used for, hairs as medicine., , 4. Coconut, , Cocos nucifera, , Seeds, , Seeds yield cooking oil, also used, as hair oil, for soaps; fruit husk, yields coir., , 5. Cotton, , Gossypium sp., , Seed, , Oil is used as ghee and cake as, fodder of animals., , C. Edible oil, , www.aiimsneetshortnotes.com
