Page 1 : CHAPTER – 9, , Heredity and Evolution, Genetics : Branch of science that deals with Heredity and variation., Heredity : It means the transmission of features/ characters/ traits from one, generation to the next generation., Variation : The differences among the individuals of a species/ population are, called variations., MENDEL AND HIS WORK ON INHERITANCE, Gregor Johann Mendel (1822&1884) : Started his experiments on plant, breeding and hybridisation, Mendel fi, was known as Father of Genetics, Plant selected by Mendel : Pisum sativum (garden pea). Mendel used a number, of contrasting characters for garden pea., TABLE OF CONTRASTING CHARACTERS. (SEVEN PARTS), CHARACTER, DOMINANT, RECESSIVE, TRAIT, TRAIT, Flower colour, Purple, White, Flower position, Axial, Terminal, Yellow, Green, Seed colour, Round, Wrinkled, Seed shape, Inflated, Constricted, Pod shape, Green, Yellow, Pod colour, Tall, Dwarf, Height of plant, Seven pairs of contrasting characters in Garden, Pea, Mendels Experiments : Mendel conducted a series of experiments in which he, crossed the pollinated plants to study one character (at a time), Monohybrid Cross :, Cross between two pea plants with one pair (monohybrid cross) contrasting, characters, Example : Tall / Short Plants., 80, , X-Science

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Page 4 : TT, tt, , Both dominant gene, Both recessive gene, , Tt, , Pure or, conditon, , One dominant, one, recessive gene, , homozygous, , Hetrozygous, condition., [Hybrid], , Phenotypic ratio : 3:1, Genotypic ratio : 1:2:1, Phenotype fi, Physical appearance [Tall or Short], Genotype fi, Genetic make up [TT, Tt or tt], Observations :, , 1. All F1 progeny were tall, (no medium height plant (half way characteristic), 2. F2 progeny ¼ were short, 3. Phenotypic ratio F2 – 3:1, Genotypic ratio F2 – 1:2:1, , Conclusions :, , 1. TT and Tt both are tall plants while tt is a short plant., 2. A single copy of T is enough to make the plant tall, while, both copies have to be 't' for the plant to be short., 3. Characters/Traits like 'T' are called dominant trait (because, it express itself) 't' are recessive trait (because it remains, supressed), , Dihybrid Cross : A cross macle between two plants having two pairs of, contrasting characters is called dihybrid cross., PARENT, GENERATION, , GAMETES, , ROUND, GREEN SEEDS, , WRINKLED, ·, YELLOW SEEDS, , RRYY, fl, RY, , rryy, fl, ry, , F1, RrYy, [round, yellow], 83, , X-Science

Page 6 : Sex Determination, Phenomenon of decision or determination of sex of an offspring, FACTORS, Responsible for Sex Determination, Environmental, In some animals the temperature, at which the fertilised eggs are, kept decides the gender., , Genetic, In some animals like humans gender or, individual is determined by a pair of, chromosome called sex chromosome, , eg. in Turtle, , XX – Female, XY – Male, , Sex Chromosomes : In human beings there are 23 pairs of chromosome. Out of, these 22 chromosomes pairs are called autosomes and the last pair of, chromosomes that help in deciding gender of that individual are called sex, chromosome., XX – female, XY – male, Sex determination in Human beings, PARENTS :, , FATHER, XY, , GAMETES, (Reproductive cells), , Zygote, formed, after fusion, of gametes, , X, , MOTHER, XX, , Y, , X, , XX, FEMALE, , XX, FEMALE, 50% probability, of a female child, , X, , XY, MALE, , XY, MALE, , 50% probability, of a male child, , This shows that half the children will be boys and half will be girls. All children, will in herit an X chromosome from their mother regardless whether they are boys, or girls. Thus sex of children will be determined by what they inherit from their, father, and not from their mother., 85, , X-Science

Page 7 : Evolution, SITUATION-I, Group of red beetles, Colour variation arises during reproduction, All beetles red except, one that is green, , One beetle Green, Reproduction, , Crows feed on red beetle, , Progeny beetles green, , No. of beetles reduces, , Crow could not feed on, green beetles as they, got camouflaged, in green bushes, , Number of green, beetles increases, Situation 1 : Green beetles got the survival advantage or they were naturally, selected as they were not visible in green bushes. This natural selection is exerted, by crows resulting in adaptations in the beetles to fit better in their environment, , SITUATION-II, Group of red beetles, Reproduction, All beetles are red except one, that is blue, Reproduces, , One blue beetle, Reproduces, , Number of red beetle, increases, , No. of blue, beetle increases, , Crows can see both blue and red beetles and can eat them, Number reduces but still red beetles are more and blue ones are few, Suddenly elephant comes and stamps on the bushes, But now beetles left are mostly blue., , 86, , X-Science

Page 8 : Situation 2 : Blue beetles did not get survivals advantage. Elephant suddenly, caused major havoc in beetle population otherwise there number would have been, considerably large., From this we can conclude that accidents can change the frequency of some genes, even if they do not get survival advantage: This is called genetic drift and it leads to, variation., , Mechanism of Heredity, Characters or traits of an organism are controlled by the genes, A Section of DNA (cellular), Gene, Provides information, For synthesis of Proteins, Proteins controls a character, Example :, Gene T, , Gene t, , responsible for, synthesis of efficient, enzyme (Protein), responsible for, synthesis of less, efficient enzyme, , 87, , More, production, of growth, hormone, Less, production, of growth, hormone, , Results, in, Tall, Plants, Results, in, short, Plants, , X-Science

Page 9 : Genetic drift. It leads to diversity without any adaptation, , SITUATION-III, Group of red beetles, Habitat of beetles (bushes), Suffer from plant disease, Average weight of beetles, decreases due to poor nourishment, No of beetles kept on reducing, Later plant disease gets eliminated, Number and average weight of the beetles, increases again, Situation 3 : No genetic change has occured in the population of beetle. The, population gets affected for a short duration only due to environmental changes, , Acquired and Inherited Traits, Acquired Traits, , Inherited Traits, , 1. These are the traits which are, developed in an individual due, to special conditions, , 1. These are the traits which are, passed from one generation to, the next., , 2. They cannot be transferred to, the progeny, , 2. They get transferred to the, progeny., , 3. They cannot direct evolution, , 3. They are helpful in evolution., , eg. Low weight of starving, beetles., , eg. Colour of eyes and hair, , 88, , X-Science

Page 10 : Speciation, Micro evolution : It is the evolution which is on a small scale. eg. change in body, colour of beetles., Speciation : it is the process of formation of new species., Species : A group of similar individuals that along to a population that can, interbreed and produce ferrite off spring., Geneflow : It is exchange of genetic material by interbreeding between, populations of same species or individuals, WAYS BY WHICH SPECIATION TAKES PLACE, Speciation takes place when variation is combined with geographical isolation., Gene flow : occurs between population that are partly but not completely, seperated, Sub Population, X1 (local), , Interbreeding, [Reproduction], , Gene, flow, , Sub Population, X1 (migrant), , Variation, in, Local, population, , Genetic Drift, It is the random change in the frequency of alleles (gene pair) in a population over, successive generations., *Natural Selection : The process by which nature selects and consolidate those, organisms which are more suitably adapted and posesses favorable variations, POPULATION Z, Sub Population, Z1, , GEOGRAPHICAL, BARRIER, ISOLATION, (River, Mountain), , Sub Population, Z2, , Over many-many generations, , 89, , X-Science

Page 11 : Results in Accumulation of different variations in, Sub population Z1 and Z2, Genetic drift, Natural selection, Sub population Z1 and Z2 incapable, of interbreeding, Reproductive, Barrier, Formation of, Formation of, new Species 1, new Species 2, Genetic drift takes place due to, a) Severe changes in the DNA, b) Change in number of chromosomes, Evolution and classification, Both evolution and classification, are interlinked., 1. Classification of species is, reflection of their, evolutionary relationship., 2. The more characteristic two, species have in common the, more closely they are, related., 3. The more closely they are, related, the more recently, they have a common, ancestor., 4. S i m i l a r i t i e s a m o n g, organisms allow us to group, them together and to study, their characteristic, , 90, , X-Science

Page 12 : Tracing Evolutionary Relationships, (Evidences of Evolution), I., , Homologous Organs : (Morphological and anatomical evidences. These are, the organs that have same basic structural plan and origin but different, functions., Example :, Forelimb of Horse, Winds of bat, Paw of a cat, , (Running), (flying), (walk/scratch/attack), , Same basic, plan,, different, functions, , II. Analogous Organs : These are the organs that have different origin and, structural plan but same function example :, Design different, Wings of bat fi, elongated fingers with skin folds, same function, ie. flight, Wings of bird fi, Feathery covering along the arm, III. Fossils : (Palaeontological evidences), The remains and relics of dead organisms of the past., Example :, i), , Fossil of wooly mammoth, , ii) Archeopteryx (fossil bird), iii) Dead insect caught in hot mud., FOSSILS ARE PRESERVED TRACES OF LIVING ORGANISMS, Eg. AMMONITE, , -, , Fossil invertebrate, , TRILOBITE, , -, , Fossil in vertebrate, , KNIGHTIA, , -, , Fossil fish, , RAJASAURUS, , -, , Fossil dinosaur skull, , 91, , X-Science

Page 13 : AGE OF THE FOSSILS, i., , Deeper the fossil, older it is., , II. Detecting the ratios of different of, the same element in the fossil, material ie Radio-carbon dating., [C-(14) dating), , Recent, , 1. ..........................., 2. ..........................., 3. ..........................., 4. ..........................., 5. .........................., 6. .........................., , Older, , Evolution by stages, Evolution takes place in stages ie bit by bit over generations., I., , Fitness advantage, Evolution of Eyes, Evolution of complex organs is not sudden it occurs due to minor changes, in DNA, however takes place bit by bit over generations., enough to, Flat worm has rudimentary eyes give fitness, advantage, Insects have compound eyes, Humans have binocular eyes, , II. Functional Advantage, Evolutions of feathers, Feathers fi, provide insulation in cold weather, but later they might become useful for flight., Example :, Dinosaurs had feathers, but could not fly using feathers. Birds seem to have, later adapted the feathers to flight., Artificial Selection :, Humans have been a powerful agent in modifying wild species to suit their own, requirement through out ages by using artificial selection. eg (i) Wild cabbage the, dissimilar looking structures have evolved from a common ancestral design. (ii), Wheat (many varieties obtained due to artificial selection), , 92, , X-Science

Page 14 : WILD, CABBAGE, , KALE, , CABBAGE, with larger, leaves, with short distance, between the leaves, BROCCOLI, , KOHL RABI, CAULIFLOWER, , Has sterile, flowers, , Arrested flower, development, , With Swollen, parts, , Molecular Phylogeny :, ?, It is based on the idea that changes in DNA during reproduction are the basic, , events in evolution, ?, Organisms which are more distantly related will accumulate greater, , differences in their DNA, , 93, , X-Science

Page 15 : Human Evolution, Tools to Study Human Evolutionary Relationship, , Excavating, , Time dating, , Fossils, , Determining, DNA, Sequences, , Although there is great diversity of human forms all over the world get all humans, are a single species, GENETIC FOOTPRINTS OF HUMANS, Hundreds/thousand of years ago, Earliest members arose in Africa, , East Asia, South Africa, , Africa, Philippines, , Island, of, Indonesia, , West, Asia, , Central, Asia, , Australia, Eurasia, , ?, They did'nt go in a single line, ?, They went forward and backward, ?, Moved in and out of Africa, ?, Sometimes came back to mix with each other., , 94, , X-Science

Page 16 : EXERCISE, (Question Bank), Very Short Answers (1 Mark), 1., , Define variation, , 2., , What is monohybird cross?, , 3., , What is dominant trait., , 4., , What are genes?, , 5., , Define Homologous organs, , 6., , If an individual has XX chromosome [22+XX] will that individual be male, or female., , 7., , Which plant Mendel had choosen for his experiments., , 8., , How do Mendel's experiment show that traits may be dominant or recessive?, , 9., , Define analogous organs? Give example., , Short Answers (2 Marks), 1., , Differentiate between acquired and Inherited traits? Give example of each., , 2., , Explain what are fossils? How the age of fossils be determined, , 3., , What is speciation? What factors lead to formation of a new species., , 4., , Explain the mechanism of sex determination in humans., , 5., , Differentiate between homologous and analogous organs. by giving, examples., , 6., , Define inheritance. What are the units of inheritance, , 7., , What is genetic drift? How it contributes to the formation of new species, , 8., , Explain monohydrid cross by taking tall and dwarf plants. Mention the, phenotypic and genotypic ratio of F1 and F2 off springs., , Long Answer (5 Marks each), 1., , Explain the process of artificial selection by taking the example of wild, cabbage plant., , 2., , Explain about the human evolution., , 95, , X-Science