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1, , Reproduction in Lower and Higher Plants, ii. Budding : It is the most common method, of asexual reproduction in unicellular, Yeast. Usually it takes place during, favourable conditions by producing one, or more outgrowths (buds). These buds on, seperation develop into new individual., iii. Spore formation : In Chlamydomonas, asexual reproduction occurs by flagellated,, motile zoospores which can grow, independently into new individuals., , Can you recall?, 1. How do plants reproduce without seeds ?, 2. How does vegetative propagation occur, in nature ?, Reproduction is the production of young, ones like parents. Reproduction is an essential, process as it leads to continuation of species as, well as to maintain the continuity of life. Each, organism has its own particular method of, reproduction. All these methods generally fall, into two categories :, i. Asexual reproduction, ii. Sexual reproduction., , Zoospores, , 1.1 Asexual Reproduction :, Asexual reproduction does not involve, fusion of two compatible gametes or sex cells., It is the process resulting in the production of, genetically identical progeny from a single, organism and inherits the genes of the parent., Such morphologically and genetically identical, individuals are called clones. Organisms, choose to reproduce asexually by different, modes or ways:, i. Fragmentation : Multicellular organisms, can break into fragments due to one or, the other reasons. e.g. Spirogyra. These, fragments grow into new individuals., , Parent cell, (Zoosporangium), , Fig. 1.2 : Zoospores in Chlamydomonas, Other methods of asexual reproduction, include - Binary fission which occurs in, Amoeba, Paramoecium; Conidia formation, in Penicillium and Gemmules formation in, Sponges., , Activity :, Sprinkle a small spoonful of yeast over a, warm water and then add sugar. Cover it and, wait for 10 minutes. Yeast becomes bubbly, over the water proving that it is still active., Can you recall?, , Chain of buds, , The capacity to reproduce by vegetative, propagation :, • Root - Sweet potato, Asparagus, Dahlia., • Leaf - Bryophyllum, Kalanchoe, Begonia,, etc., • Stem - rhizome (turmeric), tubers (potato),, bulbs (onion), etc., • How does vegetative propagation occur, in nature?, , Mother cell, , Fig. 1.1 : Budding in Yeast, 1
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Vegetative Reproduction :, , carefully grown to give many plant lets., Micropropagation method is also used now, a days., 1.2 Sexual Reproduction :, It involves fusion of two compatible, gametes or sex cells. All organisms reach to the, maturity in their life before they can reproduce, sexually. In plants, the end of juvenile or, vegetative phase marks the begining of the, reproductive phase and can be seen easily in, the higher plants at the time of flowering., The flower is specialized reproductive, structure of a plant in which sexual reproduction, takes place. The function of flower is to produce, haploid gametes and to ensure that fertilization, will take place. Typical flower consists of four, different whorls viz. calyx, corolla androecium, and gynoecium., Sexual reproduction involves two major, events viz. meiosis and fusion of gametes, to form diploid zygote and the production of, genetically dissimilar offsprings. Variations, are useful from the point of view of the survival, and the evolution of species, over the time., Sexual reproduction is characterised, by fusion of the male and female gametes, (fertilization), the formation of zygote and, embryogenesis. Sequential events that occur, in sexual reproduction are grouped into three, distinct stages viz, Pre-fertilization, Fertilization, and the Post-fertilization., , Plants reproduce asexually through their, vegetative parts. Hence, the new plants formed, are genetically identical to their parents., There are also few methods which would, not occur naturally in the plants. Agriculture, and horticulture exploit vegetative reproduction, in order to multiply fresh stocks of plants., Artificial methods are used to propagate desired, varieties according to human requirements., The various methods are as follows :, a. Cutting :, The small piece of any vegetative part, of a plant having one or more buds is used, for propagation viz. Stem cutting - e.g. Rose,, Bougainvillea; leaf cutting - e.g. Sansvieria;, root cutting e.g. Blackberry., b. Grafting :, Here parts of two plants are joined in, such a way that they grow as one plant. In, this method, part of the stem containing more, than one bud (Scion) is joined onto a rooted, plant called stock, is called grafting. Whereas, budding is also called bud grafting in which, only one bud is joined on the stock, e.g. Apple,, Pear, Rose, etc., , Activity :, , Scion, , Label the parts of flower in the given, diagram :, Stigma, Anthe, Stock, , Style, , r Filament, petal, , Fig. 1.3 : Grafting in Rose, c. Tissue culture : It is a method by, which a small amount of plant tissue is, Do you know ?, , Sepa, l, , Why does gardner choose to propagate, plants asexually?, 2, , Ovule, , Ovar, y
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Connective, , Epidermis, , Always Remember, Diploid, sporophyte, is, the, predominant plant body in all angiosperms,, where meiosis takes place to produce haploid, spores that form gametophyte. Gametophytes, are considerably reduced and develop within, the flower. They produce gametes., , Middle layers, Tapetum, , Sporogenous, tissue, , The male reproductive whorl of flower, is called androecium. Individual member of, androecium, is called stamen. Stamen consists, of filament, connective and anther., , Endothecium, , Fig. 1.4 : (a) T. S. of anther, , Structure of Anther :, An immature stage of anther is represented, by group of parenchymatous tissue surrounded, by single layered epidermis. Anther is, generally dithecous (having two lobes) and, tetrasporongiate. Each monothecous anther, contains two pollen sacs. In dithecous anther, four pollen sacs are present. Therefore, it, is tetrasporongiate. The heterogenesity, (differenciation) arises when some hypodermal, cells get transformed into archesporial cells., , Pollen grains, , Fig. 1.4 : (b) Dehisced anther, 1.3 Microsporogenesis :, Each microspore mother cell divides, meiotically to form tetrad of haploid, microspores (pollen grains)., Structure of microspore :, Typical pollen grain is a non-motile,, haploid, unicellular body with single nucleus., It is surrounded by a two layered wall called, sporoderm. The outer layer exine is thick, and made up of complex, non-biodegradable,, substance called sporopollenin. It may, be smooth or with a sculptured pattern, (characteristic of the species). It is resistant to, chemicals. At some places exine is very thin, showing thin areas known as germ-pores., These are meant for the growth of emerging, pollen tube during germination of pollen grain., The inner wall layer, intine consists of cellulose, and pectin., , T. S. of Anther :, The archesporial cell divides into an inner, sporogenous cell and outer primary parietal, cell. Sporogenous cell forms sporogenous, tissue. Each cell of sporogenous tissue is, capable of giving rise to a microspore tetrad., Parietal cell undergoes divisions to form anther, wall layers. The wall of mature anther consists, of four layers. Epidermis is the outermost, protective layer made up of tabular (flattened), cells. Endothecium is sub-epidermal layer, made up of radially elongated cells with, fibrous thickenings. Inner to endothecium is, middle layer made up of thin walled cells (1-2, layered), which may disintegrate in mature, anther. Tapetum is the inner most nutritive, layer of anther wall. It immediately encloses, the sporogenous tissue (microspore mother, cells)., , Find out, Why pollen grains can remain well, preserved as fossil?, 3
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Female reproductive whorl of flower is, gynoecium (Pistil). Individual member of, gynoecium is called carpel (megasporophyll)., A flower with many, free carpels is called, apocarpous (e.g. Michelia). A syncarpous, flower is one that has many carpels fused, together (e.g. Brinjal). Typical carpel has three, parts viz, ovary, style and stigma. The number, of ovules in the ovary varies e.g. paddy, wheat, and mango are uniovulate whereas tomato, and lady’s finger are multiovulate., , Always Remember, •, , Pollen viability (viability is the functional, ablity of pollen grain to germinate to, develop male gametophyte) depends upon, environmental conditions of temperature, and humidity. It is 30 minutes in rice and, wheat. But in some members of family, Solanaceae, Rosaceae, Leguminosae, it, lasts even for months., , Development of male gametophyte :, Pollen grain marks the begining of, male gametophyte. It undergoes first mitotic, division to produce bigger, naked vegetative, cell and small, thin walled generative cell., The vegetative cell is rich in food and having, irregular shaped nucleus. The generative cell, floats in the cytoplasm of vegetative cell., Pollen grain, , Vegetative cell, , 1.4 Structure of Anatropous ovule :, Each ovule develops inside the ovary and, is attached to the placenta by a small stalk, called funiculus. The place of attachment of, funiculus with the main body of ovule, is called, hilum. In angiosperms, the most common type, of ovule is anatropous in which micropyle is, directed downwards and is present adjacent to, the funiculus (funicle). The ovule consists of, central parenchymatous tissue, the nucellus, which is surrounded usually by two protective, coverings called integuments viz. Outer and, an inner integument., A narrow opening at the apex of the ovule, is called micropyle. Chalaza is the base of, ovule directly opposite to micropyle. Embryo, sac (female gametophyte) is oval multicellular, structure embedded in the nucellus., , Germ pore, , Intine, , C, B, A, Exine Cytoplasm Generative cell Generative nucleus, Vegetative nucleus, , D, , E, Male gametes, , F, Pollen, tube, , Chalaza, , Male gametes, , Antipodals, Secondary, Nucleus, , Tube nucleus, , Embryo sac, Synergids, Egg, Outer integument, Inner integument, , Fig. 1.5 : Development of male gametophyte, The second mitotic division is concerned, with generative cell only and gives rise to two, non-motile male gametes. The mitotic division, of generative cell takes place either in pollen, grain or in the pollen tube. The pollen grains, are shed from the anther, at this two- celled, stage in most of the angiosperms., , Nucellus, , Hilum, Funicle, Micropyle, Placenta, , Fig. 1.6 : Anatropous Ovule, 4
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Degenerated cells, Megaspore, mother cell, (diploid), , Meiosis, , Megaspore, or embryo, sac (Haploid), , Four, haploid megaspores, Mature Embryo, sac (female, gametophyte), just before, fertilisation, seven nuclei, present (six are, haploid one is, diploid), , Growth, nourished by, nucellus, Mitosis (Ist), End nearest, micropyle, , Three, Antipodal cells, Two polar, nuclei, Nuclear, fusion, , Mitosis (IInd), , Egg, (Female, gamete), , Mitosis (IIIrd), , Two synergids, , Fig. 1.7 : Development of female gametophyte, Antipodal cells are group of three cells, present at the chalazal end. The two haploid, polar nuclei of large central cell fuse to form, diploid secondary nucleus or definitive, nucleus, just prior to fertilization. This sevencelled and eight nucleated structure is called, an embryo sac. This method of embryo, sac development from a single megaspore, is described as monosporic development., In angiosperms, the development of female, gametophyte is endosporous i.e. within the, megaspore. Female gametophyte is colourless,, endosporic and is concealed in the ovule, enclosed by ovary., , 1.5 Megasporogenesis :, It is the process of formation of haploid, megaspores from diploid megaspore mother, cell (MMC). Megaspore mother cell becomes, distinguished in the nucellus, more or less in, the centre but towards micropylar end of ovule., Development of female gametophyte :, Megaspore mother cell undergoes, meiosis to form linear tetrad of haploid cells, i.e. megaspore. Upper three megaspores abort, and lowest one towards centre of nucellus, remains functional. It acts as the first cell of, female gametophyte. Generally one megaspore, towards centre is functional megaspore. It is, infact the first cell of female gametophyte., It undergoes three successive, free nuclear, mitotic divisions. Thus total eight nuclei are, formed, four of which are located at each pole., One nucleus from each pole migrates towards, the centre and are called polar nuclei. Three, nuclei towards micropylar end constitute egg, apparatus. It consists of large central, haploid, egg cell and two supporting haploid synergid, cells. Synergid shows hair like projections, called filiform apparatus, which guide the, pollen tube towards the egg., , 1.6 Pollination :, Pollen grains being non motile, angiosperms, have evolved the strategy to use abiotic agents, (wind, water) and biotic agents (birds, insects,, snails) to their flowers, feeding the visitors, and exploiting their mobility for pollination, and also seed dispersal. Pollen grains are nonmotile and they are usually carried from flower, to flower by means of external agents., Pollination is the transfer of pollen grains from, anther to the stigma of the flower. It is the prerequisite for fertilization because both the male, and female gametes are non-motile. Moreover, gametes are produced at two different sites., 5
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Self pollination is a type of pollination, which occurs in a single flower or two flowers, on a single plant. It results in inbreeding or, selfing. In contrast cross pollination is the, transfer of pollen grains from the anther of, one flower to the stigma of another flower of, different plants of same species. Pollination, can be further divided into three types on the, basis of source of pollination., , b. Geitonogamy :, It is the transfer of pollen grain to a stigma, of a different flower produced on the same plant., It is functionally similar to cross pollination, as it involves pollinating agents, but it cannot, bring about genetic variations and is only of, ecological significance e.g. Cucurbita maxima., It is similar to antogamy as pollen grains come, from same plant., , a., , c. Xenogamy (cross polination/ out, breeding) :, It is a type of cross pollination when pollen, grain of one flower is deposited on the stigma, of a flower of different plant belonging to same, species, with the help of pollinating agency. It, generates genetically varied offsprings., Majority of flowering plants depend on, the transfer of pollen grains. Virtually all seed, plants need to be pollinated. Most of the food, and fibre crops grown throughout the world,, depend upon pollinators for reproduction., The agents responsible for pollination have, been grouped into two main categories :, A. Abiotic agents, B. Biotic agents, , Autogamy (self pollination) :, It is a type of pollination in which bisexual, flower is pollinated by its own pollen grains., Offsprings are genetically identical to their, parents e.g. pea., Always Remember, •, , •, •, , •, , •, , •, , Flowers which use autogamy consist of, several adaptations in the structure of a, flower to facilitate this process. It occurs, without external pollinating agents., When flower opens to expose its sex, organs, it is called Chasmogamous., The contrivances (a condition that leads, to) favour self pollination are- Bisexuality,, Homogamy and Cleistogamy., Homogamy : When anther and stigma of, a flower become mature at the same time,, called homogamy., Some flowers are self, pollinated, even before the opening of flower., Such condition is called cleistogamy., Underground flowers in some plants, which exhibit cleistogamy are never, opened e.g. Commelina benghalensis., Plants like Viola, Commelina can produce, both chasmogamous and cleistogamous, flowers on the same plant., , A. Abiotic Agents : These are non-living, agents which include wind and water., 1. Pollination by wind (Anemophily) :, Most of the important crop plants are, wind pollinated. These includes wheat, rice,, corn, rye, barley and oats. Palms are also wind, pollinated., Adaptations in anemophilous flowers :, • The flowers are small, inconspicuous,, colourless, without nectar and fragrance, (odour)., • The pollen grains are light in weight, dry, and produced in large numbers to increase, chances of pollination considering wastage, of pollengrains., • Stigma is feathery to trap pollens carried, by wind currents., , Think about it, Why do some plants have both, chasmogamous and cleistogamous flowers ?, 6
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•, •, , Stamens are exserted with long filaments, and versatile anthers., Stamens and stigmas are exposed to air, currents., , grass) the pollen grains are long, ribbon like, and without exine., Epihydrophily : The pollen grains float on, the water surface and reach the stigma of, female flower. e.g. Vallisneria is a submerged, dioecious, fresh water aquatic plant in which, female flowers reach the water surface, temporarily to ensure pollination and male, flowers float on the surface of water., • Specific gravity of pollen grain is equal, to that of water. That is why they float on, surface of water., • Some aquatic plants are anemophilous e.g., Potamogeton, Halogaris, etc., • Some aquatic plants are entomophilous e.g., Lotus, water hyacinth, waterlily, etc., , Male inflorescence, (Tassel), Flag leaf, Tassel internode, Styles (silks), Female inflorescence, (ear), Seed (Kernel), Leaf, Stalk, (stem), Prop roots, Roots, , Female flower, , Fig. 1.8 : Pollination by wind (Maize), Water, level, , Always Remember, The pollens of wind pollinated plants, are most frequently associated with symptoms, of hayfever among people those are sensitive, to pollens. It is caused by hypersensitivity to, pollen., , Male flower, , 2. Pollination by water (Hydrophily) :, Found only in some 30 genera of, aquatic monocots. E.g. Vallisneria, Zostera,, Ceratophyllum etc., Adaptations in hydrophilous flowers :, • Flowers are small and inconspicuous., • Perianth and other floral parts are, unwettable., • Pollen grains are long and unwettable due, to presence of mucilage., • Nectar and fragrance are lacking in, flowers., , Fig. 1.9 : Male and female plant Vallisneria, B. Biotic Agents : It includes living agents., About 80% of plants require the help of other, living, moving creatures such as insects, birds,, bats, snails to transfer their pollens from one, flower to another. These also sustain our, ecosystems and produce natural resources by, helping plants to reproduce., 1. Pollination by insects (Entomophily) :, It occurs in Rose, Jasmine, Cestrum, etc., Adaptations in entomophilous flowers :, • They are large, showy and often brightly, coloured., • The flowers produce sweet odour (smell), and have nectar glands., , Hydrophily is of two types Hypohydrophily : Pollination occurs below, the surface of water. Here the pollen grains are, heavier than water, sink down and caught by, stigmas of female flowers, e.g. In Zostera (sea, 7
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•, , The stigma is rough due to presence of hair, or is sticky due to mucilaginous secretion., , •, , The pollen grains are spiny and surrounded, by a yellow sticky substance called pollenkit., , •, , Some plants have special adaptations, for the insect visitor to help in cross, pollination, e.g. lever mechanism or turnpipe mechanism in Salvia., , Fig. 1.11 : Ornithophily, Adaptations in ornithophilous flowers :, • Flowers are usually brightly coloured,, large and showy., • They secrete profuse, dilute nectar., • Pollen grains are sticky and spiny., • Flowers are generally without fragrance,, as birds have poor sense of smell., 3. Pollination by Bats (Chiropteryphily) :, Bats can transport pollens over long, distance, some times several kilometers., , Do you know ?, In biotic pollination, plants are, adapted to encourage the specific pollinators, they need. They are said to have developed, pollination contrivance. Plants and pollinators, have co-evolved physical characteristics that, make them to interact successfully. Such, characteristics are considered pollination, syndromes., , Adaptations in Chiropterphilous flowers :, • Flowers are dull coloured with strong, fragrance., • They secrete abundant nectar., • Flowers produce large amount of edible, pollen grains, e.g. Anthocephalous, (kadamb tree), Adansonia (Baobab tree),, Kigelia (Sausage tree)., 1.7 Outbreeding devices (contrivances):, Many plants have mechanisms that, discourage or prevent self pollination. To, promote cross pollination and increase genetic, diversity, plants have evolved a wide variety, of sexual strategies. Genetic diversity is, an essential factor for evolution by natural, selection. Continued self pollination results in, the inbreeding depression., Thus plants have developed many devices, to encourage cross pollination. The examples, of outbreeding devices are as follows:, , Fig. 1.10 : Lever mechanism in Salvia, Think about it, You may see bumblebee early in, the year as they try to find a suitable place, to establish a nest and rear a colony. If you, find a bumblebee nest please leave it alone., Their nest lasts only for a season. Educate the, world about the need to help the bees., 2. Pollination by birds (Ornithophily) :, Only a few types of birds are specialised, for pollination. They usually have small size, and long beaks e.g. Sun birds and humming, birds. Some ornithophilous plants are Bombax,, Callistemon (Bottle Brush), Butea, etc., , Unisexuality :, In this case, the plant bears either male or, female flowers. It is also called as dioecism., As flowers are unisexual, self pollination is, 8
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1.8 Pollen - Pistil Interaction :, It is the interaction of pollen grains with, sporophytic tissue (stigma). It begins with, pollination and ends with fertilization. All, the events from the deposition of pollen grain, on stigma to the entry of pollen tube in the, ovule (synergid) are referred as pollen - pistil, interaction. Pollination does not guarantee the, transfer of right type of pollen, often wrong type, also land on stigma. The pistil has the ability, to recognise and accept the right or compatible, pollen of the same species. Thus wrong type, of pollen is discarded by pistil. Compatibility, and incompatibility of the pollen-pistil is, determined by special proteins. This process, involves pollen recognition followed by, promotion or inhibition of pollen., The stigmatic surface of flower refuse, other wrong type or incompatible pollen, grains. A physiologial mechanism operates to, ensure that only intraspecific pollen germinate, successfully. The compatible pollen absorbs, water and nutrients from the surface of stigma,, germinates and produces pollen tube. Its growth, through the style is determined by specific, chemicals. The stigmatic surface provides, the essential prerequisites for a successful, germination, which are absent in the pollen., The pollen tube is finally pushed through the, ovule and reaches the embryo sac. The tip of, the pollen tube enters in one of the synergids, and then ruptures to release the contents. Due, to pollen pistil interaction, intense competition, develops even in the compatible pollen grains, (gametes)., It also plays important role in sexual, reproduction and seed formation. Pollen grain, can also be induced to germinate in a synthetic, medium. Sucrose induces pollen germination, and tube growth in vitro. Addition of boric acid, facilitates and accelarates pollen germination., , not possible. Plants may be monoecious, e.g., Maize or dioecious, e.g. Mulberry, Papaya., Dichogamy :, In this device, anthers and stigmas mature, at different times in a bisexual flower so as, to prevent self pollination. It can be further, divided into two types:, 1. Protandry : In this type, androecium, matures earlier than the gynoecium, e.g. in, the disc florets of sunflower., 2. Protogyny : In this type, gynoecium matures, earlier than the androecium, e.g. Gloriosa., Prepotency :, Pollen grains of other flowers germinate, rapidly over the stigma than the pollen grains, from the same flower, e.g. Apple., Heterostyly (heteromorphy):, In some plants like Primula (Primrose,, there are two or three forms/ types of flowers, in which stigmas and anthers are placed at, different levels (heterostyly and heteroanthy)., This prevents the pollens from reaching the, stigma and pollinating it. In heteromorphic, flowers, pollen grains produced from anther, pollinate stigmas produced at the same level., Herkogamy :, It is a mechanical device to prevent self, pollination in a bisexual flower. In plants,, natural physical barrier is present between, two sex organs and avoid contact of pollen, with stigma of same flower, e.g. Calotropispentangular stigma is positioned above the, level of anthers (pollinia)., Self incompatibility (self sterility):, This is a genetic mechanism due to which, the germination of pollen on stigma of the same, flower is inhibited, e.g. Tobacco, Thea., Do you know ?, , Artificial hybridization :, It is one of the major approaches used, in the crop improvement. Only the desired, , In all breeding programmes, the plants, are hand pollinated to ensure cross pollination, between selected varieties. e.g. wheat, rice., 9
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Pollen, tube, , Chalaza, Antipodals, Polar, nuclei, Nucellus, Egg cell, , Integuments, , embryo, sac, Integument, , Pollen, tube, , Synergid, Micropyle, Porogamy, A, , Pollen, tube, , Funicle, , Chalazogamy, B, , Mesogamy, C, , Fig. 1.12 : Entry of pollen tube into the ovule, pollen grains are hand pollinated and used haploid male gamete with haploid female, for fertilization. This is accomplished through gamete (egg) to produce a diploid zygote,, emasculation and bagging procedure., whereas in triple fusion, second haploid male, gamete fuses with diploid secondary nucleus, 1.9 Double Fertilization :, producing primary endosperm nucleus (PEN), Double fertilization is a complex, that developes into triploid endosperm. The, fertilization, mechanism, in, flowering, zygote develops into an embryo. Syngamy is, (angiospermic) plants. It was discovered by, a type of generative fertilization whereas triple, Nawaschin in the liliaceous plants like Lilium, fusion is a type of vegetative fertilization., and Fritillaria., Here, both the male gametes participate, After a pollen grain has reached the surface, and therefore, it is described as or called double, of the stigma, it germinates and forms a pollen, tube, which penetrates the stigma, style, ovary fertilization., Stigma, , chamber and then enters ovule. The growth of, pollen tube is guided by the chemicals secreted, by the synergids. It usually enters ovule through, the micropyle. It is termed as porogamy. But in, some cases, it is found to enter through chalaza,, known as chalazogamy and in some plants by, piercing the integuments, called mesogamy., Finally, it penetrates embryo sac of ovule, through its micropylar end., The pollen tube carrying male gametes, penetrates in one of the synergids. Watery, contents of synergid are absorbed by pollen, tube which then ruptures and release the, contents, including the two non-motile male, gametes. As non motile male gametes are, carried through hollow pollen tube, it is known, as siphonogamy that ensures fertilization to, take place. Syngamy and triple fusion are two, events of sexual reproduction in angiospermic, flowering plants. Syngamy is the fusion of, , Triple fusion, Secondary nucleus +, Male gamete, , Pollen grain, Pollen tube, Style, , Ovary, Synergids, , Micropyle, , Ovule, Syngamy, Egg + Male, gamete cell, , Fig. 1.13 : Double fertilization, Significance of Double Fertilization :, • It is a unique feature of angiosperms. It, ensures that the parent plant invests a, seed with a food store, only if the egg is, fertilized., • The diploid zygote develops into an embryo, which consequently develops into a new, plant., 10
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• The triploid PEN develops into nutritive, endosperm tissue., , vacuole appears in the centre of cell pushing, the nuclei towards the periphery. Later, walls, develop between the nuclei, hence multicellular, endosperm is formed. But in several cases, cell wall formation remains incomplete. e.g., wheat, sunflower and coconut. Coconut has, multicellular endosperm in the outer part and, free nuclear as well as vacuolated endosperm, in the centre., , • It restores the diploid condition by fusion of, haploid male gamete with haploid female, gamete (i.e. through syngamy)., • It also helps to avoid polyembryony., 1.10 Development of Endosperm :, The triploid primary endosperm nucleus, repeatedly divides, mitotically to form nutritive, tissue, called endosperm. In post-fertilization, changes within the ovule, the embryo and, endosperm are seen to develop simultaneously., The other cells of embryo sac disorganized, sooner or later. The formation of triploid, endosperm nucleus triggers cell division which, leads to the formation of endosperm., , b. Cellular Type :, In some plants, division of triploid primary, endospermic nucleus is immediately followed, by wall formation. So that the endosperm is, cellular right from the beginning. It is mostly, observed in 72 families of dicots as in members, - Balsam, Petunia, Adoxa, etc., Use your brain power, , Embryo, , Zygote/ Oospore, , What do you call the kernel that you, eat in tender coconut ?, c. Helobial Type :, It occurs in the order Helobiales of, monocotyledons. In this case, first divison, of primary endosperm nucleus is followed, by a transverse wall, which divides the cell, unequally. The smaller cell is called chalazal, cell and larger cell is the micropylar cell. Then, the nuclei in each cell divide by free nuclear, divisions and then walls develop between, nuclei in micropylar chamber. It is intermediate, between cellular and nuclear type endosperm, e.g. Asphodelus., , Endosperm, , i. Nuclear, Oospore, , Embryo, , Oospore, , Embryo, , Endosperm, , ii. Cellular, , iii. Helobial, , Fig. 1.14 : Types of Endosperm, , Mosaic Endosperm : Endosperm containing, tissues of two different types is called mosaic, endosperm. In plants like corn the endosperm, contains patches of two different colours. It, forms a sort of mosaic pattern., , There are three types of endosperms on, the basis of mode of development. These are, i. Nuclear type, ii. Cellular type, iii. Helobial, type :, a. Nuclear Type :, It is the most common type found in 161, angiospermic families. Here, the primary, endosperm nucleus repeatedly divides, mitotically without wall formation to produce, large number of free nuclei. A big central, , 1.11 Development of Embryo :, The process of development of zygote, into an embryo is called embryogenesis. The, embryo is developed at the micropylar end of, embryo sac. The growth of embryo triggers only, 11
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e, , t, E, h, , m, , Endo, h, , A, , e2, , E, h, , S, , B, , e1, , Anti, , S, , Embryo, , S, , s2, s1, m, , E, , C, , D, , E, , B, , 1, , Endo, Pl, , Cot, , Hypo, , Hypo, , Cot, , Rad, , Rad, Embryo, Anti, , R.c, , R.c, S, G, , H, , F, , A. Oospore. B. Two celled, proembryo. e=embryonal initial;, t=suspensor initial; m=Embryo sac, membrane. B1=4-celled I-shaped, proembryo; e , e are from embryonal, 1, , 2, , initial; s1, s2 are from suspensor, initial. C. Further development, of, embryo., S=Suspensor,, h=Hypophysis; E=Embryonal mass, D. L. S. of ovule Endo=Endosperm, in free nuclear stage. Anti=Antipodal, tissue., Embryo=, Developing, embryo E. Embryo showing further, development of embryonic octants, and hypophysis. F. L. S. of ovule., Endosperm becoming cellular., G., Embryo, Cot=Cotyledons;, Hypo=Hypocotyl;, Rad=Radicle;, R.c=Root-cap H. Mature seed., Pl=Plumule. Endosperm has been, consumed almost completely., , Fig. 1.15 : Development of Dicot Embryo as in Capsella, after certain amount of endosperm is formed., After fertilization the embryonic development, begins., The zygote divides to form two- celled, proembryo. The larger cell towards the, micropyle is called basal or suspensor initial, cell and smaller cell towards chalaza is, called terminal or embryonal initial cell. The, suspensor cell divides transversely in one plane, to produce filamentous suspensor of 6-10 cells., Oospore, , Suspensor initial, , A, , The first cell of the suspensor towards the, micropylar end becomes swollen and function as, a haustorium. The lowermost cell of suspensor, is known as hypophysis. The suspensor helps, in pushing the embryo in the endosperm. The, embryonal initial undergoes three successive, mitotic divisions to form octant. The planes, of divisions are at right angles to each other., The lower tier of four cells of octant give rise, to hypocotyl and radicle whereas four cells of, Suspensor, , B, , Scutellum, , Embryonal initial, Coleoptile, , C, E, , D, , Shoot apex, , Plumule, Cotyledon, , Suspensor, , Epiblast, Radicle, , Radicle, , Radicle, , Hypocotyl, , Plumule, , Cotyledon, , Plumule, , Root cap, Coleorrhiza, , Cotyledon, F, , G, , H, , Fig. 1.16 : Development of Monocot Embryo, 12
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upper tier form the plumule and the one or two, cotyledons. The hypophysis by further division, gives rise to the part of radicle and root cap., Subsequently, the cells in the upper tier of octant, divide in several planes so as to become heart, shaped which then forms two lateral cotyledons, and a terminal plumule. Further enlargement of, hypocotyl and cotyledons result in a curvature, of embryo and it appears horse-shoe shaped., The embryo development is similar in both, dicots and monocots up to the octant stage. The, difference appears later. In monocot embryo,, single cotyledon occupies terminal position, and plumule is lateral. The single shield shaped, cotyledon is called as scutellum. The protective, sheath of plumule is called coleoptile and, that of radicle is coleorhiza. Finally, ovule is, transformed into the seed and ovary into the, fruit., , Seed coat and, fruit-wall, , Endosperm, Scutellum, , Aleurone, layer, , Coleoptile, Plumule, Radicle, Coleorrhiza, , Fig. 1.18 : Maize seed (Monocot), Seed sometimes consists of two distinct, coverings, a typical outer seed coat, the testa, and the inner thin, membranous tegmen., The nucellus in the ovule may persist in, some genera like black pepper and beet as a, thin, papery layer, the perisperm. In some, seeds, the food reserves in the endosperm, are partially used up in the development, of an embryo. Obviously, in such seeds the, endosperm remains conspicuous and fills a, greater part of the seed. Thus, the resultant seed, is endospermic or albuminous e.g. Castor,, Coconut, Maize, etc., In other seeds, embryo absorbs food, reserve from the endosperm completely during, its developmental stages. Thus, endosperm, disappears (disorganizes) in mature seeds., The resultant seed is non-endospermic or exalbuminous e.g. Pea, bean, etc., The cotyledons in some non-endospermic, seeds act as a food storage and in others they, are the first photosynthetic organs. Micropyle, persists as a small pore in seed coat to allow, the entry of water and oxygen during soaking., , 1.12 Seed and Fruit Development :, The goal of reproduction, in every living, organisms including plants, is to create, offsprings for the next generation. One of the, ways that plants can produce offpsrings is by, forming (making) seeds. The flowers must be, pollinated in order to produce seeds and fruit., Seed development is initiated by fertilization., The integuments of the fertilized ovule persist, and get transformed into the seed coat of, mature seed., Epicotyl, Hypocotyl, , Fruit development is triggered by hormones, produced by developing seeds. As mentioned, earlier, after fertilization the zygote is formed, and the ovary begins to differentiate into the, fruit and ovary wall develops into pericarp., Pericarp is basically three layered which get, differentiated in the fleshy fruit like mango,, coconut, etc., , Radicle, Embryo, Cotyledon, Seed coat, , Fig. 1.17 : Bean seed (Dicot), , 13
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1.13 Apomixis :, It is phenomenon of formation of embryo(s), through asexual method of reproduction, without formation of gametes and the act of, fertilization. Alternatively, it is unusual sexual, reproduction where there is no meiosis and, syngamy. Embryo develops in the ovule and, ovule developes to form seed ., In apomixis, when a gametophyte organ, or cell produces embryo like structure without, fertilization, it is termed as apogamy. Similarly, when diploid sporophyte cell produces a diploid, gametophyte without undergoing meiosis is, called apospory, e.g. Orange, Mango., , Can you recall?, 1. What are the parts of the fruit ?, 2. What is the difference between true fruit, and false fruit ?, Significance of seed and fruit formation :, • Fruits provide nourishment, to, the, developing seeds., • Fruits protect the seeds in immature, condition., • Seeds serve as important, propagating, organs (units) of plant., • Seeds and fruits develop special devices, for their dispersal and thus help in the, distribution of the species., , Internet my friend, Collect information about seed mother, Rahilbai’s story. How does she save over 80, varieties of native seeds?, , Try This, Help to rebuild natural ecosystem., Mix seeds and potting soil together with dry, clay. Mould the mixture into small balls and, allow them to dry in sun. Throw the same at, places suitable for germination., , The main categories of apomixis are:, a. Recurrent apomixis :, In this type, the embryo sac generally rise, either from an archesporial cell or from some, other part of the nucellus. In diplospory, the, unreduced embryo sac is derived from the, diploid megaspore mother cell e.g. Taraxacum., In apospory, the nucellar cells give rise to, apomictic embryo sac., , Dormancy is a state of metabolic arrest that, facillitates the survival of organisms during, adverse environmental conditions. Structural or, physiological adaptive mechanism for survival, is called dormancy. Mature and viable seeds, will not germinate even in the presence of, favourable conditions and they are dispersed at, different places during dormancy. Viable seeds, germinate only after completion of dormancy, period., , b. Non-recurrent apomixis :, In this type, megaspore mother cell, undergoes usual meotic division and a haploid, embryo sac is formed. Here, the embryo arises, either from the egg by parthenogenesis or from, some other haploid cells of gametophyte through, apogamy. Plants produced by this method are, generally sterile and do not reproduce sexually,, e.g. Nicotiana., , Think about it, 1. How long seeds stay viable/ healthy?, 2. Can old seeds still grow?, Some examples of oldest mature seeds that, have grown into viable plants are as follows :, • Lupinus arcticus - 10,000 years, • Phoenix dactylifera - 2000 years, • Some seeds are short lived, e.g. Citrus., • Some tiny seeds are easy for dispersal., e.g. Striga, Orchids, Orobancha., , c. Adventive Embryony :, In this type, embryos may develop from, somatic nucellus or integuments along with, normal zygotic embryo. It is common in, Mango, Orange, Lemon, etc. It gives rise to a, condition called polyembryony., 14
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Genetically identical plants can be, produced effectively and rapidly by apomixis., , Think about it, Why are some seeds of Citrus referred to, as polyembryonic ?, , 1.14 Parthenocarpy :, This term is coined by Noll (1902). It is the, condition in which fruit is developed without, the process of fertilization. It occurs naturally, in some varities of Pineapple, Banana, Papaya,, etc. In these plants, it seems that the placental, tissue in the unfertilized ovary produces auxin, IAA (Indole-3 Acetic Acid) which is responsible, for enlargement of ovary into fruit. The fruit, resembles the normally produced fruit but it is, seedless., , Do you know ?, 1. Parthenogenesis is the development of, embryo directly from egg cell or a male, gamete. It is a kind of apogamy., 2. Agamospermy : Here plants produce, seeds. But embryo, inside it, is produced, without (omitting) meiosis and syngamy., 3. Parthenocarpy can be induced artificially, by - spraying of gibberellins, delaying, pollination, use of foreign pollens, etc., 4. Genetically uniform parental type, seedlings are obtained from nucellar, embryos., , Use your brain power, What do bananas and figs have in, common ?, 1.15 Polyembryony :, It is the development of more than one, embryos, inside the seed and the condition, is described as polyembryony. It was first, noticed by Leeuwenhoek (1719) in the seeds, of Citrus genus. It is the occurrence of more, than one embryo in a seed which consequently, results in the emergence of multiple seedlings., The additional embryos result from the, differentiation and development of various, maternal and zygotic tissues associated with, the ovule of seed. Polyembryony may be true, or false depending upon whether many embryos, arise in the same embryo sac or in different, embryo sacs in the same ovule. In adventive, polyembryony, an embryo develop directly, from the diploid cell of nucellus and integuments, as in Citrus. In cleavage polyembryony, zygote, proembryo sometimes divides (cleaves) into, many parts or units. Each unit then developes, into an embryo. Polyembryony increases, the chances of survival of the new plants., Nucellar adventive polyembryony is of great, significance in horticulture., , Activity :, Prepare chart for natural vegetative, propagation exibited by flowering plants, indicating the vegetative part/s and the, different examples., Organ, , 15, , Part, , Name of plant
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Exercise, Q. 2 Very short answer type questions :, 1. Name the part of gynoecium that, determines the compatible nature of, pollen grain., 2. How many haploid cells are present in a, mature embryo sac ?, 3. Even though each pollen grain has 2, male gametes, why atleast 20 pollen, grains are required to fertilize 20 ovules, in a particular carpel?, 4. Define megasporogenesis., 5. What is hydrophily ?, 6. Name the layer which supplies, nourishment to the developing pollen, grains., 7. Define parthenocarpy., 8. Are pollination and fertilization, necessary in apomixis ?, 9. Name the parts of pistil which develop, into fruits and seeds., 10. What is the function of filiform, apparatus ?, , Q. 1 Multiple choice questions., 1. Insect pollinated flowers usually posses, ................, a. Sticky pollens with rough surface, b. Large quantities of pollens, c. Dry pollens with smooth surface, d. Light coloured pollens, 2. In ovule, meiosis occurs in .........., a. Integument, b. Nucellus, c. Megaspore, d. Megaspore mother cell, 3. The ploidy level is NOT the same in ......, a. Integuments and nucellus, b. Root tip and shoot tip, c. Secondary nucleus and endosperm, d. Antipodals and synergids, 4. Which of the following types require, pollinator but result is genetically, similar to autogamy?, a. Geitonogamy, b. Xenogamy, c. Apogamy, d. Cleistogamy, 5. If diploid chromosome number in a, flowering plant is 12, then which one of, the following will have 6 chromosomes?, a. Endosperm, b. Leaf cells, c. Cotyledons, d. Synergids, 6. In angiosperms, endosperm is formed, by/ due to .........., a. Free nuclear divisions of megaspore, b. polar nuclei, c. polar nuclei and male gamete, d. synergids and male gamete, 7. Point out the odd one .........., a. Nucellus, b. Embryo sac, c. Micropyle, d. Pollen grain, , 16, , Q. 3 Short Answer Questions :, 1. How polyembryony can be commercially, exploited ?, 2. Pollination and seeds formation are very, crucial for the fruit formation. Justify, the statement., 3. Incompatibility is a natural barrier in the, fusion of gametes. How will you explain, this statement?, 4. Describe three devices by which cross, pollination isencouragedinAngiosperms, by avoiding self pollination., Q. 4 Long Answer Questions :, 1. Describe the process of double, fertilization., 2. Explain the stages involved in the, maturation of microspore into male, gametophyte.
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3. Explain the development of dicot, embryo., , 4. Draw a labelled diagram of the L.S., of anatropous ovule and list the, components of embryo sac and mention, their fate after fertilization., , Q. 5 Fill in the blanks:, The .....................collects the pollen grains., , ......................... is the transfer, of pollen grains from anther of, the flower to the stigma of the, same or a different flower, , The male whorl, called the ....................., produces ..................... ., The pollen grains represent, the ........................, , Once the pollen reaches the, stigma, pollen tube traverses, down the ................... to the, ovary where fertilisation, occurs., , The .................... contains the egg, or ovum., ....................................................., takes place when one male gamete, and the egg fuse together. The, fertilised egg grows into seed from, which the new plants can grow., , The .......................... are coloured to, attract the insects that carry the pollen., Some flowers also produce................ or, .............. that attracts insects., , The ................................ is the base of, the flower to which other floral parts are, attached., , The whorl ...................... is green that, protects the flower until it opens., , Q. 6 Label the parts of seed., , Q. 7 Match the column., Column - I, (Structure before, seed formation., A. Funiculus, B. Scar of Ovule, C. Zygote, D. Inner integument, , Column - II, (Structure after, seed formation., I. Hilum, II. Tegmen, III. Testa, IV. Stalk of seed, V. Embryo, , a. A - V, B - I, C - II, D - IV, b. A - III, B - IV, C - I, D - V, c. A - IV, B - I, C - V, D - II, d. A - IV, B - V, C - III, D - II, Project :, Natural vegetative propagation by leaves only in different vascular plants., , 17
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2, , Reproduction in Lower and Higher Animals, Gemmule Formation:, Gemmule is an internal bud formed only, in sponges. It has asexually produced mass or, aggregation of dormant cells, the archaeocytes, capable of developing into a new organism., The archaeocytes get coated by a thick resistant, layer of secretion by amoebocytes. The, gemmule is formed to overcome unfavourable, conditions. On return of favourable conditions, of water and temperature, the gemmules, hatch and develop into a new individual. e.g., Spongilla., , Can you recall?, 1. Enlist the various life processes. Name, the life process which is responsible for, continuation of the human race., 2. What are the common methods of, reproduction in the unicellular organisms, like Euglena, Amoeba and Paramoecium?, 3. What type of asexual reproduction, occurs in Hydra?, 4. What are the different methods of, reproduction in animals?, We know that reproduction is one of the, major life processes of any living organism., It helps in maintaining the continuity of the, species. Reproduction is defined as the, biological process of formation of new life, forms from pre-existing similar life. It thus, becomes a vital process which enables the, species to survive over a long period, even, though the individuals or organisms live, naturally for a limited period of time i.e. their, life span. In this chapter, we will learn about, the various methods of reproduction in animals, the human reproductive system, gametogenesis, and fertilization, early embryology, parturition, and reproductive health., Reproduction in animals occurs mainly by, two methods i.e. asexual and sexual., , Micropyle, Monaxon spicules, Inner membrane, Archaeocytes, Outer membrane, , Fig. 2.1 : Gemmule, Budding:, It is a simple method of asexual, reproduction normally occuring in favourable, conditions. It is seen in a variety of animals, like coelenterates (Hydra and corals) and in, some colonial ascidians. In Hydra, a small, outgrowth is produced towards the basal end, of the body., , 2.1 Asexual Reproduction in animals :, It is a common method among lower, animals. It does not involve meiosis nor the, gamete formation and fusion. The formation of, progeny is by a single parent only and does not, involve both the sexes, so it is called asexual, reproduction. The progeny or daughter cells, are genetically identical to the single parent, and are also referred to as clones. The lower, animals reproduce asexually by gemmule, formation and budding., , Bud, , Developing, bud, , Fully, mature, bud, , Fig. 2.2 : Budding in Hydra, , Young, Hydra, separates, , 18
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It develops as a bud which grows and, forms tentacles and develops (get transformed), into a new individual. This process is called, budding. The young Hydra gets detached from, the parent and becomes an independent new, organism., , The sexually reproducing animals show, two main phases in their life time. The earlier, juvenile phase mainly represents physical, growth phase starting from birth. The animals, can not reproduce sexually in this phase., The later Reproductive maturity phase, is attained usually after physical growth is, almost over. It involves growth and activity, of the sex organs. The animal can reproduce, sexually in this phase. Both these periods, (phases) are of variable duration in different, animals. After attaining sexual maturity,, the animal exhibits various events, namely prefertilization (gametogenesis and gamete, transfer), fertilization (fusion of male and, female gametes) and post fertilization events, (formation of zygote and embryogenesis)., , Do you know ?, Regeneration:, A word which in biology refers to the, process observed in all living organisms, from the unicellular bacteria upto the most, complex multicellular forms e.g. humans. By, this process, the organism can fundamentally, repair or regrow or restore its lost or damaged, part. Though it involves asexual processes,, it differs distinctly from reproduction e.g., a damaged Hydra can regenerate its lost, part. Similarly Planaria if wounded, its cells, become active and regenerate lost part or, organ back to its original state. They can also, reproduce asexually by fragmentation. Also,, it is seen in planarians that the anterior end, exerts a pull on the posterior end resulting in, a constriction in the middle part and splitting, into two pieces. Each piece grows into a new, Planaria. i.e. two clones of the original have, been formed., , The sexually reproducing animals show, various breeding patterns. Some like the goat,, sheep, and donkey are seasonal breeders while, humans and apes are continuous breeders., They can breed throughout the year., Human Reproduction :, Humans are sexually reproducing animals., The process of reproduction involves various, sequential steps such as gametogenesis,, insemination, internal fertilization (i.e. fusion, of male and female gametes), zygote formation, and embryogenesis, gestation and parturition., The gametes, sperms and eggs are produced, by the primary sex organs, testis in male and, ovary in female. Organs other than testis and, ovary, are called secondary sex organs of the, male and female. As male and female can be, externally differentiated by certain specific, features called secondary sexual characters,, they are called sexual dimorphic characters., In males, presence of beard, moustache,, hair on the chest, muscular body, enlarged, larynx (Adam’s apple) are secondary sexual, characters while in females these characters, are the developed breast, broader pelvis and, high pitched voice., , 2.2 Sexual reproduction in animals :, It is the process which involves the, production of offspring by the formation and, fusion of gametes. It is also called amphimixis., In animals, gamete formation primarily, involves meiosis., 19
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Histology of Testis:, The testis is externally covered by a, collagenous connective tissue layer called, tunica albuginea. Outer to it is an incomplete, peritoneal covering called tunica vaginalis,, and inner to it is tunica vasculosa, a thin, membranous and vascular layer. Fibers from, tunica albuginea divide each testis into about, 200-300 testicular lobules (refer dig. 2.3, L. S. of testis). Each with 1-4 highly coiled, seminiferous tubules. Each seminiferous, tubule is internally lined by cuboidal germinal, epithelial cells (spermatogonia) and few large, pyramidal cells called Sertoli or sustentacular, cells., , A. Male Reproductive System :, It consists of the primary male organ, (gonad) called testes, the accessory ducts, and glands which form internal and external, genitalia., Can you recall?, Label the given male reproductive, system you have studied., 7, 1, 2, 3, , 8, 9, , 4, 5, 6, , Tunica, albuginea, 10, , Connective tissue, , The germinal epithelial cells undergo, gametogenesis to form the spermatozoa., Sertoli cells provide nutrition to the developing, sperms. Various stages of spermatogenesis, can be seen in the seminiferous tubules. The, inner most spermatogonial cell (2n), primary, spermatocyte (2n), secondary spermatocyte, (n), spermatids (n) and sperms (n). The, Interstitial or Leydig’s cells lie in between the, seminiferous tubules. They secrete the male, hormone androgen or testosterone., , Vas deferens, Vasa efferentia, , Tunica vaginalis, Tunica albuginea, , Tail of, epididymis, , Basement, membrane, , Fig. 2.4 : T. S. of Testis, , Rete testis, Body of, epididymis, , Germinal, epithelium, , Sperm, bundle, , Spermatic cord, , Head of, epididymis, , Interstitial cells, (Leydig cells), , Sertoli, cell, , a. Testes:, A pair of testes, mesodermal in origin, are, formed in the lower abdominal cavity. They, are located in a pouch called scrotum. During, early foetal life, the testes develop in abdominal, cavity and later they descend into the scrotal, sac through a passage called inguinal canal., Each testis is oval in shape, 4 to 5cm long, 2 to, 3cm wide and 3cm thick., , Blood vessels, and nerves, , Seminiferous, tubule, , Lobules, Septum, Seminiferous tubule, , Fig. 2.3 : L. S. of testis, , 20
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c. Glands:, The male accessory glands are as follows:, • Seminal vesicles: It is a pair of glands lying, on the posterior side of urinary bladder., It secretes an alkaline seminal fluid, which contains fructose, fibrinogen and, prostaglandins. It contributes about 60%, of the total volume of the semen. Fructose, provides energy for sperm movement while, fibrinogen coagulates the semen into a, bolus for quick propulsion in the vagina., The prostaglandins stimulate reverse, peristalsis in vagina and uterus aiding, faster movement of sperms towards the egg, in the female body., • Prostate gland: It is a large and single, gland made up of 20-30 lobes and is, located underneath the urinary bladder. It, surrounds the urethra and releases a milky, white and slightly acidic prostatic fluid into, the urethra. It forms about 30% of volume, of semen. It contains citric acid, acid, phosphatase and various other enzymes., The acid phosphatase protects the sperms, from the acidic environment of vagina., , Do you know ?, 1. Presence of the peritoneal covering, around the testis is an indication of its, abdominal origin., 2. The testis are suspended in the scrotum, by the spermatic cord., 3. Testosterone hormone stimulates the, descent of testis and the fibro-muscular, band called gubernaculum in the, scrotum., 4. In some males a loop of the intestine, may pass through the inguinal canal into, the scrotum and cause a condition called, inguinal hernia., b. Accessory ducts:, The accessory ducts include rete testis,, vasa efferentia, epididymis, vas deferens,, ejaculatory duct and urethra. All the, seminiferous tubules of the testis at the, posterior surface form a network of tubules, called rete testis. 12-20 fine tubules arising, from rete testis are vasa efferentia. They carry, the sperms from the testis and open into the, epididymis. It is a long and highly coiled tube, which is differentiated into an upper caput-,, middle corpus- and lower cauda epididymis., The sperms undergo maturation in epididymis., Posteriorly it leads into the vas deferens which, travels upto the abdominal cavity and loops, over the ureter to open into the urethra. Before, doing so, it joins the duct of seminal vesicle, to form the ejaculatory duct. The ejaculatory, duct passes through the prostate gland and, opens into the urethra. The urethra provides, a common passage for the urine and semen, and hence is also called urinogenital duct. In, males the urethra is long and extends through, the penis. It opens to the outside by an opening, called the urethral meatus or urethral orifice., All the accessory ducts except urethra are, present in pairs., , Activity :, Find the symptoms of prostate cancer., Always Remember, Prostate cancer is cancer of the prostate, gland. Men who are over 50 years of age, and have a daily high consumption of fat,, have an increased risk of prostate cancer., Internet my friend, What is the role of prostaglandin?, •, , 21, , Cowper’s gland / Bulbourethral gland, : It is a small, pea sized and paired gland, situated on either side of urethra. These
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glands secrete an alkaline, viscous, mucous, like fluid which acts as a lubricant during, copulation., , 1., 2., 3., 4., 5., 6., 7., , Semen :, It is the viscous, alkaline and milky, fluid (pH 7.2 to 7.7) ejaculated by the male, reproductive system. Normally 2.5 to 4.0 ml of, semen is given out during a single ejaculation, and it contains about 400 million sperms. It, contains secretion of the epididymis and the, accessory glands for nourishing (fructose),, neutralizing acidity (Ca++, bicarbonates),, activation for movement (prostaglandins)., , A pair of ovaries, A pair of oviducts, Uterus, Vagina, External genitalia (vulva), A pair of vestibular glands, A pair of mammary glands, Can you recall?, Give labels to given female reproductive, system:, , d. External genitalia:, It includes the penis and the scrotum., The penis is the male copulatory organ. It is, cylindrical and muscular with three bundles, of erectile tissue- a pair of postero-lateral, tissue called corpora cavernosa and a median, corpus spongiousm. The swollen tip of the, penis is called glans penis. It is covered by a, loose fold of skin called foreskin or prepuce., Scrotum :, It is a loose pouch of pigmented skin, lying behind the penis and is divided into a, right and left scrotal sac by a septum of tunica, dartos made of smooth muscle fibres. The, foetal testes are guided into and retained in the, scrotum by a short fibro muscular band called, gubernaculum. The testes remain suspended, in scrotum by a spermatic chord. Failure, of testis to descend into scrotum is called, cryptorchidism. The failure also results in the, sterility. The cremaster and dartos muscles of, scrotum help in drawing testes close or away, from the body. This helps in maintaining the, temperature of the testis 2-30C lower than, the normal body temperature, necessary for, spermatogenesis., , 1. Ovary : It is the primary female sex organ., Its main function is production of egg or ovum, and the female reproductive hormones. It is, solid, oval or almond shaped organ. It is 3.0, cm in length, 1.5 cm in breadth and 1.0 cm, thick. It is located in the upper lateral part of, the pelvis near the kidneys. Each ovary is held, in position by ligaments by attaching it to the, uterus and the abdominal wall. The largest of, these is the broad ligament formed by a fold, of peritoneum. It holds the ovary, oviduct and, the uterus to the dorsal body wall. The ovarian, ligament attaches ovary to the uterus. The, ovary produces five hormones viz, estrogen,, progesteron, relaxin, activin and inhibin., Structure and development of the ovary :, Each ovary is a compact structure, differentiated into a central part called medulla, and the outer part called cortex. The cortex, is covered externally by a layer of germinal, , B. Female Reproductive System:, The female reproductive system consist of, the following parts :, 22
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epithelium. The stroma or loose connective, tissue of the medulla has blood vessels, lymph, vessels, and nerve fibres. The outer cortex is, more compact and granular. It shows large, number of tiny masses of cells called ovarion, follicles. These are collectively formed from, the immature ova originating from cells of, the dorsal endoderm of the yolk sac. The cells, migrate to the gonadal ridge during embryonic, development and divide mitotically. Now, these cells are called oogonia. As the oogonia, continue to grow in size they are surrounded, by a layer of granulosa cells and form the, rudiments of the ovarian follicles. The process, of oogenesis starts much before the birth of the, female baby and by the end of twelve weeks, the ovary is fully formed. It has more than two, million primordial follicles in it., , The large scale destruction of the primordial, follicles during growth is called atresia., The development of the primordial follicles, into mature or Graafian follicles restarts with, the onset of puberty. During each menstrual, cycle only one of the primordial follicle starts, growing to form the Graafian follicle., In each cycle, alternately one of the two, ovaries produces the Graafian follicle., The 1st menstrual cycle or menarche begins, normally at about 13 years and Menopause, i.e. stopping of the cycles happens at age 45, to 55 years. The period in between menarche, and menopause is the reproductive age of the, female and is approximately 32 years. In this, time the female will be producing a maximum, of about 416 eggs (32 ×13 = 416 eggs)., Ovarian histology of a mature female :, In the histology of ovary, we have, discussed the primary structure of ovary. The, following discussion includes the changes seen, in a mature ovary, primarily in the cortex. The, different stages of development of the oocyte, can be seen. These changes in the ovary are, cyclic, occuring during each menstrual cycle, and it involves maturation of the primordial, follicles into primary, secondary and Graafian, follicles. Each primary follicle has multilayered, cuboidal follicular cells. The stroma cells, add theca over the follicle. It now changes, into a secondary follicle. There is growth of, the oocyte and the granulosa cells increase, in number. They start producing the hormone, estrogen. The secondary follicle grows into the, Graafian follicle by addition of more follicular, cells. As this process of maturation of follicles, takes place, they begin to move towards the, surface of ovary. The Graafian follicle presses, against the thin wall of the ovary giving it a, blistered appearance. The egg is released from, the Graafian follicle during ovulation and, the remaining part of the follicle changes into, a temporary endocrine gland called corpus, , Blood vessels Day 1 Primary Secondary Day 12, Primordial follicle, follicle, Tertiary, follicle, follicle, Mature, follicle, Cortex, , Oocyte, Medulla, , Corpus, albicans, Day 20, , Day 14, , Ovulated ovum, Corpus, luteum, , Germinal epithelium, , Fig. 2.5 : T.S. of ovary, The cells of germinal epithelium give, rise to groups of oogonia projecting into the, cortex in the form of cords called egg tubes of, Pfluger. Each cord at its end has a round mass, of oogonial cells called egg nests, from which, the primordial ovarian follicles develop. Each, primordial follicle has, at its center a large, primary oocyte (2n) surrounded by a single, layer of flat follicular cells. The primary oocyte, starts with its meiotic division but gets arrested, it at meiosis I. Of the two million primordial, follicles embedded in the foetal ovary only, about one million remain at birth and only, about 40,000 remain at the time of puberty., 23
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luteum. If fertilization does not take place the, corpus luteum degenerates into a white scar, called corpus albicans., , a. Infundibulum : The proximal funnel, like part with an opening called ostium, surrounded by many finger like processes, called fimbriae (of these at least one is long, and connected to the ovary). The cilia and, the movement of fimbrae help in driving, the ovulated egg to the ostium., , Use your brain power, In t. s. of ovary, can all the stages of, follicles be seen simultaniously?, , b. Ampulla : It is the middle, long and, straight part of the oviduct. Fertilization of, the ovum takes place in this region., , Structure of Graafian follicle :, Graafian follicle is a mature ovarian, follicle. An eccentric secondary oocyte is, surrounded by a non-cellular layer of zona, pellucida secreted by the vitelline membrane, of oocyte. The outermost protective and fibrous, covering is called theca externa. Inner to it is, cellular theca interna. It produces the hormone, estrogen. Inner to the theca interna, the follicular, cells form the membrana granulosa. From the, membrana granulosa the cells differentiate, into discus proligerus and the corona radiata, cells. Cumulus oophorus is the term used for, the oocyte and surrounding granulosa cells . A, fluid filled cavity called antrum lies between, the oocyte and the membrana granulosa. It is, filled with a fluid called liquor folliculi., , c., , Isthmus / Cornua : The distal narrow part, of the duct opening into the uterus., , 3. Uterus : It is commonly also called the, womb. It is a hollow, muscular, pear shaped, organ, located above and behind the urinary, bladder. It is about 7.5 cm long, 5 cm broad, and 2.5 cm thick. The uterus can be divided, into three regions :, a. Fundus : It is the upper dome shaped part., Normally implantation of the embryo, occurs in the fundus., b. Body : It is the broad part of the uterus, which gradually tapers downwards., c. Cervix : It is the narrow nec about 2.5 cm, in length. It extends into the vagina. Its, passage has two openings : an internal, os towards the body, and an external os, towards the vagina., , Theca externa, Theca interna, Antrum, , Internally the uterine wall can be, distinguished into three layers : Outermost, perimetrium,, middle, thick, muscular, myometrium, made up of thick layer of, smooth muscles. Vigorous contractions of these, muscles cause labour during the parturition, (child birth). The innermost layer called, endometrium or mucosal membrane is made, up of stratified epithelium. The thickness of, this layer regularly undergoes changes in, during the menstrual cycle. It is richly supplied, with blood vessels and uterine glands. These, provide nourishment to the developing foetus., , Granulosa cells, Corona radiata, Oocyte, , Fig. 2.6 : Graafian Follicle, 2. Oviduct / Fallopian tube / Uterine tube:, These are a pair of muscular ducts lying, horizontally over the peritoneal cavity. The, proximal part of the tube lies close to the ovary,, and distally it opens into the uterus. Each tube, is 10 to 12 cm in length. It is internally lined by, ciliated epithelium. It can be divided into three, regions :, 24
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c. Clitoris - A small conical and sensitive, projection lying at the antirior end of labia, minora. It has a pair of erectile tissue - The, corpora cavernosa and is homologous to, the penis., , Do you know ?, Uterus cancer:, Most of the uterine cancers begin, in the layer of cells that form the lining of, endometrium of uterus., Symptoms : Abnormal bleeding between, periods, vaginal bleeding after menopause,, an abnormal watery, blood-tinged discharge, from vagina, pelvic pain., Detection : It is diagnosed with Pap smear, test, biopsy, Ultrasound., Treatment : Chemotherapy, radiation,, surgical removal of uterus (hysterectomy)., , d. Labia majora - These are a pair a fleshy, folds of skin forming the boundary of vulva., They are homologous to the scrotum. They, surround and protect the other parts of, external genitalia and enclose the urethral, and vaginal openings in the vestibule., e. Mons pubis - It is a fleshy elevation above, the labia majora. The Mons pubis and outer, part of labia majora show pubic hair., , 4. Vagina : It is a tubular, female copulatory, organ, 7 to 9 cm in length. It lies between the, cervix and the vestibule. The vaginal wall has, an inner mucosal lining, the middle muscular, layer and an outer adventitia layer. The mucosal, epithelium is stratified and non-keratinised, and stores glycogen. There are no glands but, the cervical secretion of mucus is recieved in, the vagina. The opening of the vagina into, the vestibule is called vaginal orifice. This, opening is covered partially by a fold of mucus, membrane called hymen. The vagina acts as, a passage for menstrual flow as well as birth, canal during parturition., , 6. Accessary glands / Vestibular glands /, Bartholin’s glands : It is a pair of glands, homologous to the Bulbourethral or Cowper’s, glands of the male. They open into the vestibule, and release a lubricating fluid., Mammary glands :, Accessory organs of female reproductive, system for production and release of milk after, parturition. Development of the mammary, gland occurs at puberty under the influence of, estrogen and progesteron. Lactotropic hormone, (LTH) or prolactin helps in development of, lactiferous tubules during pregnancy., Pectoralis major muscle, , 5. External genitalia : The external genital, organs of female include parts external to the, vagina and are collectively called ‘vulva’, (covering or wrapping), or pudendum. They, include the following parts :, a. Vestibule - It is a median vertical depression, of vulva enclosing the urethral and vaginal, opening., , Intercostal, muscles, , Suspensory ligaments, Lactiferous, sinus, , Ribs, Lactiferous, duct, , Lung, , Gland lobules, , b. Labia minora - These are another pair of, thin folds inner to the labia majora with, which they merge posteriorly to form the, fore chette while towards anterior end they, converge into a hood-like covering around, the clitoris., , Fat, , Fig. 2.7 : Section view of Mammary gland, The mammary glands are a pair of rounded, structures present in the subcutaneous tissue of, the anterior thorax in the pectoral region (from, 25
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2nd to 6th rib). These are modified sweat glands., Each mammary gland contains fatty connective, tissue and numerous lactiferous ducts. The, glandular tissue of each breast is divided into, 15-20 irregularly shaped mammary lobes,, each with alveolar glands and lactiferous duct., Alveolar glands secrete milk which is stored, in the lumen of alveoli. The alveoli open into, mammary tubules. The tubules of each lobe, join to form a mammary duct. Many mammary, ducts join to form a wider mammary ampulla,, which is connected to lactiferous duct. These, converge towards the nipple located near the, tip of the breast. It is surrounded by a dark, brown coloured and circular area of the skin, called areola., , Puberty / Sexual maturity in Females :, The reproductive system becomes, functional at puberty. It is characterised, by onset of menstrual cycle also called, menarche, which usually occurs at age 1014 years. However, unlike in the males, the, mature females show cyclic changes in their, reproductive system- the menstrual cycles., These cycles continue only upto menopause., This normally happens at age 45-50 years. The, period from menarche to menopause is thus the, reproductive age of the female. The female is, unable to bear children (by natural method), after menopause. Menarche, menstrual cycles, and menopause are controlled by gonadotropic, hormones., 2.3 Menstrual cycle (Ovarian cycle):, Menstrual cycle is the characteristic, feature of primates including human. It, involves a series of cyclic changes in the ovary, and the female reproductive tract, mainly in, the uterus. These changes take place under, the effect of gonadotropins and the ovarian, hormones respectively. The cycles are repeated, with a periodicity of approximately 28 days., The middle of each cycle is characterised by, the release of an egg. This egg in every cycle, comes alternately from one of the two ovaries., The cycle is divided into four phases., , Do you know ?, Breast cancer :, Symptoms: First symptom of breast cancer, is a lump in breast or underarm. Lump is, painless. Swelling of all or part of breast., Skin irritation, Breast or nipple pain, nipple, retraction, Redness, scaliness or thickening, of nipple or breast skin, discharge, etc., Detection:, Mammogram, (x-ray),, ultrasound, MRI, Biopsy, Blood test., Treatment:, Radiation, therapy,, chemotherapy lumpectomy, Mammoplasty, , a. Menstrual phase:, The begining of each cycle is taken as, the first day where menses or loss of blood, (45-100ml) takes place and it lasts for, approximately five days (average 3-7 days)., Endometrium of uterus breaks down, under the effect of prostaglandins released, due to decreased levels of progesteron and, estrogen. Due to this blood, tissue fluid, mucus,, endometrial lining and the unfertilized oocyte, is discharged through vagina. The endometrial, lining becomes very thin i.e. about 1 mm. The, menstrual discharge continues for an average, of 5 days, however this blood does not clot, , Do you know ?, Weaning : Mother’s milk is replaced, gradually by solid food after some time., This process is called weaning., Puberty / Sexual maturity in Males :, Puberty is the age at which the reproductive, system becomes functional, sex organs begin, to produce gametes and sex hormones. In, males the onset of puberty occurs at age 12-15, years. Under the influence of testosterone, the, secondary sexual characters appear. Thereafter, it remains functional throughout the life., 26
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due to presence of fibrinolysin. Menstrual, phase occurs when an ovulated egg does not, get fertilized and it is thereby shed out along, with the menstrum. It is thus called ‘funeral of, unfertilized egg’., During these five days, many primordial, follicles develope into primary and few of them, into secondary follicles under the effect of FSH., Folicular phase, Gonadotropic, hormone, levels, , of degeneration is called atresia. Developing, secondary follicles secrete the hormone, estrogen. The stimulation for proliferation of, new follicles is influenced by GnRH which, stimulates release of FSH., Endometrium begins to regenerate under, the effect of gradually increasing quantity, of estrogens. Regeneration also involves, formation of endothelial cells, endometrial or, uterine glands and network of blood vessels., Thickness of endometrium reaches 3-5 mm., , Luteal phase, , LH, FSH, , c. Ovulatary phase:, It is the shortest phase of menstrual cycle., It involves rupturing of the mature graafian, follicle and release of ovum (secondary, oocyte) into the pelvic cavity; usually on 14th, day of menstrual cycle. Rapid secretion of LH, by positive feedback mechanism causes the, mature follicle to rupture. Ovulation may be, accompanied by mild or severe pains in lower, abdomen., , Ovarian, cycle, Preovulatory phase, , Ovarian, hormone, levels, , Ovulation, , Postovulatory phase, , Progesteron, Estrogens, , Uterine, cycle, , Phases of the Menses Proliferative, phase, uterine cycle, Days, 0, 5, 14, , Secretory phase, 21, , d. Secretory phase / Luteal phase:, Duration of this phase is between the, ovulation and beginning of the next menses., This phase is the longest phase. It lasts for 14, days; from 15th to 28th day of the cycle., After release of secondary oocyte,, remaining tissue of graafian follicle transforms, into corpus luteum under the effect of LH., Corpus luteum begins to secrete progesteron, and estrogens. The ovulated egg may get, fertilized within 24 hours. However, in the, absence of fertilization, corpus luteum can, survive for only two weeks and then degenerate, into a white scar called corpus albicans., The corpus luteum releases progesteron,, small amount of estrogens and inhibin., Under the influence of these hormones, the, endometrial glands grow, become coiled and, start uterine secretions. Endometrium becomes, more vascularized and thickens up to 8-10 mm., Inhibin stops secretion of FSH. These changes, are necessary for fertilization and subsequent, implantation., , 28, , Fig. 2.8 : Hormones and the menstrual, cycle., Internet my friend, 1. Enlist the examples of primates and non, primate animals., 2. Collect information about female, reproductive cycles differentiating both, primates and non-primates., b. Proliferative phase / Follicular phase /, Post menstrual phase:, This phase is the duration between the end of, menstruation and release of ovum (ovulation)., Duration of this phase is more variable than, other phases. Generally, it extends from 5th to, 13th day of menstrual cycle., A few (6 to 12) secondary follicles proceed, to develop but usually one of them develops into, a graafian follicle (mature follicle). The other, secondary follicles degenerate. This process, 27
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However, if the ovulated egg gets fertilized, and the embryo is implanted, there is secretion, of human chorionic gonadotropin (hCG),, which extends the life of corpus luteum and, stimulates it’s secretory activity. Presence of, hCG in maternal blood and urine is an indicator, of pregnancy. In absence of fertilization, next, menstrual cycle begins., , spermatogenesis. At the onset of puberty, the, hypothalamus begins secretion of gonadotropin, releasing hormone (GnRH). It initiates the, significant increase in the secretion of follicle, stimulating hormone (FSH) which induces, spermatogenesis. Each seminiferous tubules, is lined by a single layer of cuboidal epithelial, cells called germinal epithelium., The cells of germinal epithelium undergo, spermatogenesis to produce sperms. Process of, spermatogenesis involves three phases., , Always Remember, Hygiene practices during menstruation :, • Keep the pubic area clean., • Change the sanitary napkin every 4-5, hours., • Maintaining personal hygiene during, menstruation is important to reduce the, risk of infection., • Dispose used sanitary napkin properly., • Using damp and dirty clothes or using, a sanitary napkin for a longer time can, act as a perfect environment for growth, and multiplication of harmful bacteria, and lead to infections., , Primordial cell, (2n), Mitosis, I. Multiplication, phase, , Use your brain power, Why the menstruation is painful in some, women?, , Spermiogenesis Meiotic division, , III. Maturation phase, , II. Growth, phase, , Spermatogonia, (2n), Primary spermatocytes, (2n), , Meiosis I, , Secondary spermatocytes, Meiosis II (n), Spermatids, (n), Spermatozoa, (n), , Can you tell?, Fig. 2.9 : Spermatogenesis, Can you tell the names of primates who, show the presence of menstrual cycle?, , I. Multiplication phase: The primordial, germ cells (2n) of seminiferous tubules, undergo repeated mitotic divisions to produce, large number of spermatogonia (2n). Each, spermatogonium is diploid and with 46, chromsomes., , 2.4 Gametogenesis:, The gametogenesis is the process of, formation of gametes in sexually reproducing, animals. The male gamete is sperm and the, female gamete is ovum or egg. The gametes are, formed from primordial germ cells of gonads., , II. Growth phase: Some of the spermatogonia, stop dividing and grow in size to develop, into primary spermatocytes (2n) due to, accumulation of food., , Spermatogenesis:, The process of formation of the male, gamete (sperm) or spermatozoa from the, germinal epithelium of testis is called, 28
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III. Maturation phase: It involves meiotic or, reduction division. The spermatocyte undergoes, the first phase of meiotic division (meiosis, I) leading to formation of two haploid cells, called secondary spermatocytes (n), which are, with 23 chromosomes each. The secondary, spermatocyte undergoes second phase of, meiotic division (meiosis II) to produce four, haploid spermatids. The spermatid is nonmotile and non-functional. It gets transformed, into a functional spermatozoa by the process, called spermiogenesis. During this process of, change, the spermatids remain held to each, other and to the sertoli cells by cytoplasmic, bridges. The sperm heads remain attached to the, sertoli cells and their tails hanging in the lumen, of seminiferous tubule. During spermiogenesis,, length of spermatid increases. Centrioles are, rearranged as primary and distal centrioles., Mitochondria become spirally coiled and, acrosome is formed from golgi complex., , contains hydrolytic enzymes; hyaluronidase, and proteolytic enzymes like zona lysins and, corona penetrating enzymes., Neck: It is a very short region having two, centrioles i.e. proximal centriole and distal, centriole., Middle piece: It has an axial filament, surrounded by 10-14 spiral turns of, mitochondria (nebenkern). It produces energy, necessary for the movement of sperm., Tail: It is a long, slender and tapering part, containing cytoplasm and fine thread- axial, filament. The axial filament arises from the, distal centriole and travels through out the, length of tail. It is partly surrounded by plasma, membrane (main piece). The part without, plasma membrane is called end piece., Oogenesis:, It is process of formation of the haploid, female gamete i.e. egg or ovum from the diploid, germinal epithelium. It involves the process of, meiosis (and mitosis). Like spermatogenesis,, oogenesis process can be divided into three, stages :, I. Multiplication phase, II. Growth phase, III. Maturation phase, , Structure of sperm:, Sperm is the male gamete. It is a motile,, microscopic elongated cell. It is divisible into, three parts- head, middle piece and tail., Acrosome, Head, Neck, Middle, piece, , Nucleus, Proximal centriole, Distal centriole, Mitochondria, , P.G.C. (2n), I, Multiplication, Phase, (Mitotic, Oogonia, (2n), , divisions), , Tail, , Principal, , II Growth, Phase, , piece, End piece, , Secondary, Occyte (n), , Primary Oocyte (2n), Meiosis I, I Polar body (n), , III Maturation, Phase, , Fig. 2.10 : Structure of Sperm, Head: The sperm head is oval in shape and, contains haploid nucleus. Above the nucleus,, there is a cap like structure called acrosome., It is formed from the golgi body. Acrosome, , Meiosis II, , II Polar bodies (n), Ovum (n), , Fig. 2.11 : Oogenesis, 29
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and is ready for fertilization. (Completion of, meiosis II and completion of fertilization go, hand in hand. If the secondary oocyte does not, receive the sperm / spermatozoa, it is shed off, along with menstrum)., , Activity :, Prepare a chart of comparison between, spermatogenesis and oogensesis., I. Multiplication phase: In this stage, the, primary germinal cells PGCs (2n) of ovary, undergo repeated mitotic division to form, millions of gamete mother cells or oogonial, cells (2n). This process is completed in the, embryonic stage of human females., , Structure of secondary oocyte:, In human, unfertilized egg when ovulated, i.e. released from the ovary is actually the, secondary oocyte. It is non-cleidoic (without, shell) and microlecithal (yolk is present in very, small quantity). It is approximately 0.1mm (100, microns) in size. It is rounded, nonmotile and, haploid female gamete. The nucleus of the egg, appears large and is called germinal vesicle., Typical nucleus or pronucleus is formed at the, time of fertilization. The cytoplasm of egg is, also called ooplasm. It is devoid of centrioles., The egg is surrounded by various coverings., , II. Growth phase: Some of the oogonia stop, division and begin to increase in size and form, the primary oocytes (2n). Cellular organelles, like ER, golgi appratus and mitochondria, increase in number., III. Maturation phase: Oogenesis takes place, in the ovaries. The process is initiated prior to, birth of the female baby. The primary oocytes, (2n) enter the maturation phase which includes, meiotic division (Meiosis I and Meiosis II)., The diploid primary oocytes undergo meiosis I, (reduction division) to form 2 haploid daughter, cells. This division is peculiar in females, as both the daughter cells are with haploid, number of chromosomes i.e. 23 chromosomes., But due to unequal division of cytoplasm, of, the 2 daughter cells produced, one is a large, cell called secondary oocyte (n) and another is, a small cell called 1st polar body (n). Normally, the 1st polar body does not enter meiosis II., The secondary oocyte (n) proceeds meiosis II,, only upto metaphase II. It’s division is further, stopped or arrested at this stage. The secondary, oocyte is shed from the graafian follicle and, ovary. The restart and completion of meiosis II, will happen only with entry of the sperm. This, last phase is usually completed in the ampulla, of the fallopian tube at the time of fertilization., In this division also, the two unequal daughter, cells are formed- the large cell is ovum (n) and, the small cell is 2nd polar body (n). The ovum, (n) so formed functions as the female gamete, , Vitelline membrane, Perivitelline, space, Zona pellucida, Corona radiata, Germinal, vesicle, First polar body, , Fig 2.12 : Unfertilized egg/ Ovum, The egg membrane is called vitelline, membrane. It secretes a non-cellular, glycoproteinous membrane, zona pellucida, on its outside. Adhering to the outer surface of, zona pellucida are several radially elongated, cells forming the corona radiata. These, cells are derived from the innermost layer of, granulosa cells. They are firmly held to the, zona pellucida and to each other by hyaluronic, acid (mucopolysaccharide). Between the, vitelline membrane and the zona pellucida is, a fluid filled perivitelline space. The first polar, body lies in this space., 30
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becomes thin, Ca++ enters the sperm and their, tails begin to show rapid whiplash movements., , The egg shows polarity. The side having, germinal vesicle and first polar body is called, animal pole while the side opposite to it is, called vegetal pole., , Always Remember, , 2.5 Fertilization / Syngamy:, Sexual reproduction primarily involves, formation and fusion of gametes. Fertilization, is the later process which involves fusion of, the haploid male and female gametes resulting, in the formation of a diploid zygote (2n). Like, in other mammals, in humans the process of, fertilization is internal and it usually takes, place in the ampulla of the fallopian / uterine, tube. The fertilized egg or zygote will develop, into an embryo and this process occurs within, the uterus., Extracellular space, Corona radiata, Zona pellucida, Second meiotic, division of oocyte, Second meiotic, division of first, Polar body, Male pronucleus, Female pro-nucleus, (swollen ovum nucleus), Polar bodies, Male pronucleus, Mitotic spindle, Centriole, Female pronucleus, Zygote, , Indian law under the Hindu marriage, Act has defined the marriageable age of a, boy and girl. As per this act, minimum age, for boy must be 21 and for a girl must be 18, years, at the time of marriage., As a result of capacitation, sperms become, extra active and begin to start moving upwards, from vagina to uterus and to the oviducts., The prostaglandins activate the sperms., The vestibular secretions of the female also, enhance sperms motility. The sperms swim at, an average speed of 1.5 to 3.0 mm/min., , Sperm nucleus, 1. After the sperm, penetrates the secondary, oocyte, the oocyte, completes meiosis II,, forming the ovum and, second polar body., 2. Sperm and ovum, nuclei swell, forming, pronuclei., 3. Pronuclei approach, each other and mitotic, spindle forms between, them., 4. Chromosomes, of both pronuclei, intermix. Fertilization is, accomplished., , Sperms reach upto the ampulla as a result of, their own swimming and partly by contraction, of uterus and fallopian tubes stimulated by, oxytocin of female. After capacitation the, sperms may reach ampulla within 5 minutes., Sperms can remain viable for 24-48 hours, (Ovum for about 24 hours)., b. Entry of sperm into the egg : Out of 200 to, 400 million sperms, only few hundred manage, to reach the ampulla. Though many sperms, reach the ampulla but only a single sperm, fertilizes the ovum. A sperm after reaching, the egg / ovum comes to lie against it. Its, acrosome releases lysins : hyaluronidase and, corona penetrating enzymes. They separate, and dissolve the cells of corona radiata, so the, sperm head passes through the zona pellucida, of egg. The zona pellucida has fertilizin, receptor proteins (ZP3, ZP2). The fertilizin, binds to specific acid protein- antifertilizin, of sperm. It brings about attraction of sperms, to the egg to enhance fertilization. Fertilizinantifertilizin interaction is species specific., Thus, the fertilizin-antifertilizin reaction is also, called compatibility reaction., , Fig. 2.13 : Process of Fertilization, Mechanism of fertilization :, Semen released during ejaculation has sperms, and some secretions. The coagulated semen, now undergoes liquification and sperms, become active. The mechanism of fertilization, is as follows :, a. Movement of sperm towards egg:, It involves capacitation of sperms, reaching the vagina. Here as many as 50% are, demotilised / broken / destroyed. Remaining, sperms undergo capacitation. This process, requires 5-6 hours. Acrosome membrane, 31
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Acrosome reaction : As the sperm head touches, the zona pellucida in the animal pole region,, its acrosome covering ruptures to release lytic, enzymes, acrosin or zona lysin. They act on, the zona pellucida at the point of contact. This, causes egg reaction - A small fertilization, cone / cone of reception is formed on the egg, membrane. The sperm head comes in contact, with this cone. It results in production of a weak, wave of depolarisation. Plasma membrane of, the both cells dissolve at the point of contact., The sperm nucleus and the centrioles enter the, egg, while other parts remain outside., , process called syngamy or karyogamy. The, zygote is thus formed. The proximal centriole, recieved from the sperm helps in formation of, the synkaryon spindle and cleavage of cell into, two blastomeres., Internet my friend, Find out about extraembryonic membranes., , As soon as the sperm head touches the, vitelline membrane, a cortical reaction gets, activated changing the vitelline membrane, into a fertilization membrane by deactivating, the sperm receptors of zona pellucida. A, distinct perivitelline space is created around, the fertilization membrane. This prevents any, further entry of other sperms into the egg i.e., polyspermy is avoided., Do you know ?, 1. What would happen if the sperm fuses, with the egg before it reaches the, fallopian tube?, 2. What is ectopic pregnancy? Can ectopic, pregnancy continue upto full term?, , Significance of fertilization :, • Secondary oocyte completes the process of, oogenesis and is transformed into a mature, ovum (n)., •, , The diploid chromosome number is restored, in the zygote by the process of syngamy., , •, , The ovum lacks the centrioles necessary, for further divisions, are received from the, sperm during fertilization., , •, , Fertilization involves fusion of male and, female gametes from the two parents. It, results in variations which are significant, to evolution., , •, , Sex of the offspring is determined., , Always Remember, •, , c. Activation of ovum : The ovum before, fertilization was at metaphase II stage. With a, contact of sperm head to the vitelline membrane, of egg, it gets activated to resume and complete, its meiosis II. With this it gives out the second, polar body. The germinal vesicle organises into, female pronucleus. At this stage, it is the true, ovum or egg., , •, , •, , •, , Fusion of egg and sperm : The coverings, of male and female pronuclei degenerate, allowing the chromosomal pairing., This, results in the formation of a synkaryon by the, 32, , Secondary oocyte (egg) is ovulated after, LH surge at about the middle of menstual, cycle i.e. day 14., Egg (arrested at metaphase II) reaches, the ampulla of uterine tube in 12-24, hours after ovulation. The cilia and the, fimbriae of the fallopian tube help, direct, the egg to ostium., During coitus/ intercourse semen is, deposited into the vagina of the female., This process is called insemination., Human male during ejaculation gives out, about 2-4ml of semen with an average, count of 200-400 million sperms.
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2.6 Embryonic development :, The zygote formed as a result of syngamy, is activated to divide., , arranged. Till the formation of morula the, zona pellucida is retained around the embryo, and thus, there is no change in the overall size, from zygote to morula. The morula reaches the, isthmus and gains entry into the uterus by the, end of day 4., , Cleavage :, It is the process of early mitotic division of, the zygote into a hollow multicellular blastula., It does not involve the growth of the daughter, cells. The cells formed by cleavage are called, blastomeres., Since, there is no growth phase between, the cleavages, the size of blastomeres will be, reduced with every successive cleavage. As, the size reduces, the metabolic rate increases., Subsequent cleavages are thus faster than, earlier one. This requires rapid replication of, DNA and high consumption of oxygen., Process of cleavage : In human, cleavage is, holoblastic i.e. the whole zygote gets divided., The cleavage planes may be longitudinal or, meridional and equatorial or horizontal. It, is radial and indeterminate i.e. fate of each, blastomere is not predetermined., , 12-15 hours, , 24-30 hours, Polar body, , Blastomere, A. 2- Cell stage, , B. 4- Cell stage, , C. 8- Cell stage, D. Morula, Inner cell mass, Blastocyst, cavity, , Trophoblast, E. Early blastocyst, F. Late blastocyst, , Fig. 2.14 : Process of cleavage and, formation of Blastula, , Internet my friend, What is meroblastic cleavage? In which, organisms, is it observed?, , Blastulation :, Blastulation is the process of formation, of the hollow and multicellular blastocyst., The embryo (blastocyst) that enters the uterus, remains floating in uterine cavity for 2-4 days, after its entry. i.e. till the end of 7th day after, fertilization. The outer layer of cells seen in the, morula now form the layer called trophoblast., , The 1st cleavage in the zygote is meridional, and occurs at about 30 hours after fertilization. It, divides longitudinaly into two blastomeres, one, slightly larger than the other. The 2nd cleavage, is also longitudinal but at the right angle to, the 1st one and occurs after 30 hours of 1st, cleavage. The 3rd cleavage is horizontal. After, 3rd cleavage the embryo is in 8-cell stage. As, the cleavages are going on the young embryo is, gradually being pushed towards the uterus. By, the end of 4th day after fertilization, embryo is a, solid ball of 16-32 cells and externally looking, like mulberry. This stage is thus called morula., The morula shows cells of two types : smaller,, clearer cells towards the outer side and inner, cell mass of larger cells. Cells are compactly, , Cells from the trophoblast begin to absorb, the glycogen rich uterine milk. The blastocyst, doubles in size from 0.15 mm to 0.30 mm. With, more fluid entering inside the blastocyst cavity, is formed. These outer cells become flat and are, called trophoblast cells (since they help only in, absorbing nutrition for the developing embryo)., The inner larger cells form inner cell mass or, embryoblast (the embryo proper develops, from the embryoblasts). These remain attached, 33
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to the trophoblasts on only one side. The, trophoblast cells in contact with the embryonal, knob are called cells of Rauber. At this stage,, the blastocyst shows polarity. The side with, inner cell mass is called the embryonal end and, the side opposite to it is the abembryonal end., By the end of the 7th day the blastocyst is fully, formed. It is now ready for implantation and, gastrulation. The function of zona pellucida is, to prevent the implantation of the embryo at an, abnormal site. It does not expose the sticky and, phagocytic trophoblast cells till it reaches the, implantation site i.e. within the uterus, hence, zona pellucida now ruptures., , The inner layer of cells is called, cytotrophoblast (cells with defined membrane), since, the cells retain their cell boundaries., Gastrulation :, It is the process of formation of ‘gastrula’, from the blastocyst. In the gastrula stage, there, is slowing of the rate of cleavage or divisions, but there are two important events that take, place actively :, a. Differentiation of blastomeres : This process, results in the formation of three germinal layers, i.e. ectoderm, mesoderm and endoderm from, the cells of the embryoblast., b. Morphogenetic movements : These are, different types of movements to reach their, definite place in the embryo., , Can you recall?, What do you mean by Monozygotic, Dizygotic and Conjoined twins., , Ectoderm, , Implantation :, The blastocyst after its formation, gets, implanted or embedded into the endometrium, of the uterus. This process usually begins, on day 7 after fertilization and by end of, 10th day, the embryo is completely burried, inside the endometrium. The embryo usually, implants in the region of the fundus of uterus., In the process, the embryo attaches itself by, its embryonic pole, close to the endometrium., The trophoblast cells of the animal pole, have the power to stick to the uterine wall., Rapid division of the trophoblast cells lying, against the embryonal knob takes place. It, results in the formation of two distinct layerssyncytiotrophoblast and cytotrophoblast. The, outer layer, syncytiotrophoblast is syncytium, i.e. a layer of protoplasm with many nuclei. It, gives out processes which extensively invade, the endometrium. The lytic enzymes secreted, by the trophoblasts, rupture the endometrial, cells thereby making a burrow, into which, the embryo begins to get implanted. By the, end of the 10th day the whole embryo is deeply, embedded into the endometrium, completing, the process of implantation., , Amniotic, cavity, , Mesoderm, Yolk sac, Endoderm, Coelom, Chorion, , Fig. 2.15 : V. S. of late Grastrula, Gastrulation begins in the embryoblast, cells on about 8th day after fertilization. Cell on, the free end of inner cell mass called hypoblasts, (primitive endoderm) become flatend, start, dividing and grows downward towards the, blastocoel, cavity of blastocyst. This layer, called endoderm is first to differentiate. It grows, within the blastocoel and forms a sac called, Yolk sac. The remaining cell of the inner cell, mass, in contact with cells of Rauber are called, epiblasts (primary ectoderm). Both layers form, a flat, bilaminar embryonal disc., After formation of endoderm the second, layer to be differentiated is the ectoderm. Cells, of epiblast divide and redivide and move in, such a way that they enclose the amiotic cavity., 34
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Table 2.16 : Fate of germinal layers:, Ectoderm, Mesoderm, Endoderm, Ectoderm gives rise to epidermis Mesoderm forms all types of Endoderm, develops, into, of skin, hair, nails, sweat glands, muscles (except iris muscles epithelium of mid- gut, glands of, salivary glands, mammary glands, and ciliary muscles of eye which stomach and intestine, tongue,, lacrimal glands, sebaceous glands, originate from ectoderm), tonsils, lungs, trachea, bronchi,, cornea, lens, retina, conjunctiva, connective tissues, dermis of larynx, urinary bladder, vagina,, nasal epithelium, enamel of teeth, skin, adrenal cortex, heart, liver, pancreas, thyroid gland,, internal and external ear, foregut, blood, blood vessels, lymphatic parathyroid gland, thymus, hindgut, adrenal medulla, anterior vessels, middle ear, dentine of gland,, Eustachian, tube,, and posterior pituitary, pineal teeth, urinary and reproductive epithelium of urethra, lining of, gland, entire nervous system., ducts, gonads, kidneys, sclera middle ear., and choroid of eye., The floor of this cavity has the embryonal, disc. The pyramidal cells of the disc towards, the amniotic cavity form the embryonal, ectoderm. The roof of amniotic cavity is lined, by amniogenic cells. Later, these cells divide, and redivide to form the amnion. Amnion is, an extra embryonic membrane that surrounds, and protects the embryo. As a result of all, these changes, the bilaminar embryonic disc, is positioned in between amniotic cavity and, Yolk sac., , Do you know ?, Stem cells: These are undifferentiated somatic, cells of a multicellular organism. They are, capable of giving rise to many more cells of the, same type or they can also differentiate into other, type of cells. Bone marrow cells, blood stem cells, cord cells or umbilical cord cells are examples, of stem cells. They can be used in the treatment, of Parkinson’s disease, Alzheimer’s disease,, Diabetes, Leukemia, Arthritis, etc., , Actual gastrulation occurs about 15 days, after fertilization, in which the bilaminar, embryonic disc is transformed into trilaminar, embryonic disc. This transformation occurs by, division, rearrangement and migration of cells, of epiblast. It begins with formation of primitive, streak and a shallow groove on the surface is, called primitive groove. This streak progresses, from posterior to anterior end of embryo. From, site of a primitive streak, a third layer of cells, called mesoderm extends between ectoderm, and endoderm. Anterior end of primitive groove, communicates with yolk sac by an aperture, called blastopore (future anus). The embryonal, disc now has differentiated into three layersectoderm, mesoderm and endoderm. The, further process after gastrulation is called, organogenesis., , 2.7 Pregnancy :, It is the condition of carrying one or more, embryos in the uterus. It is also called gestation., It refers to the period between fertilization, of the egg, upto parturition. The average, period of pregnancy in human lasts for 266, days from fertilization or 280 days (266+14), counted from LMC- Last Mensturation Cycle., This pregnancy peroid of approximately nine, months is divided into three trimesters of three, months each., 35
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First Trimester :, (from fertilization to 12th week), It is the time of most radical changes in, mother and embryo. The embryo receives, nutrients in the first 2-4 weeks directly from, the endomerium. It is the main period of, organogenesis and the development of body, organs. By the end of eight weeks, the major, structures found in the adult are formed in the, embryo in a rudimentary form. The embryo is, now called foetus. It is about 3cm long. Arms,, hands, fingers, feet, toes are formed. Foetus can, open and close mouth and fists. CNS is fully, formed, working of excretory and cirulatory, systems begins. Movements of foetus begin but, mother can not feel it. Heart beat can be heard, from 6th week. Progesterone level becomes high, and menstual cycle is suspended till the end of, pregnancy. At the end of first trimester foetus is, about 7-10 cm long., Meanwhile, the mother’s body also, undergoes rapid changes. High levels, of progesterone initiate changes in her, reproductive system. The maternal part of, placenta grows, the uterus becomes larger. In, this period, the mother experiences ‘morning, sickness’ (nausea, vomiting, mood swings,, etc)., , felt by the mother. Head has hair, eyebrows and, eyelashes appear, pinnae are distinct. The baby, reaches half the size of a newborn., Third (final) Trimester :, (from 27th week till the parturition), The foetus grows to about 3-4 kg in weight, and 50 cms in length. Eyes are open. There, is gain in body weight. As the foetus grows,, the uterus expands around it, the mother’s, abdominal organs become compressed and, displaced, leading to frequent urination,, digestive blackages and strain in the back, muscles. At the end of third trimester the, foetus becomes fully developed and ready for, parturition., 2.8 Placenta:, It is a flattened, discoidal organ in the, uterus of a pregnant woman. The placenta is a, temporary structural and functional connection, between foetal and maternal circulation., The placenta facilitate the supply of oxygen, and nutrients and also for removal of carbon, dioxide and excretory wastes produced by the, foetus. The placenta is attached to the wall of, the uterus and to the baby’s umbilical cord., Placenta, Villi, , Uterine, wall, , Intervillous space, , Second Trimester :, (from 13th to 26th week), It is the period of rapid growth of foetus., The uterus grows enough for the pregnancy, to become abvious. The foetus is very active, and grows to about 30 cms. Development, of brain begins. Hormone levels stabilize as, hCG declines, the corpus luteum deteriorates, (regresses) and the placenta completely takes, over the production of progesterone which, maintains the pregnancy., Ultrasound (sonography) at 18-20 weeks, shows baby’s growth and position. From, this estimated due date of delivery can be, established. Baby’s movements can be easily, , Umbilical, cord, , Amniotic, sac, Amniotic, fluid, Chorion, , Amnion, , Fig. 2.17 : Placenta, Placenta is the only organ, which is formed, of tissues from two different individuals- the, mother and the foetus. Part of the placenta, contributed by the foetus is called the foetal, placenta and it is the chorionic villi. The other, 36
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part which is rich in blood supply shared by, the mother. It is a part of uterine wall, termed, as maternal placenta. So human placenta is, called haemochorial., The umbilical cord is formed of three blood, vessels. Of these three blood vessels, two are, small arteries which carry blood towards the, placenta and one is a large vein which returns, blood to the foetus., The placenta also acts as an endocrine, tissue and produces hormones like hCG,, progesterone, estrogen while relaxin is secreted, by the ovary in the later phase of pregnancy., Level of hCG increases upto the end of first, trimester and then it declines. By the end of first, trimester progesterone is produced by placenta., These hormones are required for foetal growth, and maintenance of pregnancy., , Always Remember, hCG, HPL (Human placental Lactogen),, relaxin are produced in women only during, pregnancy., 2.9 Parturition:, Humans are viviparous, as they give birth, to their young ones. Parturition is the process of, giving birth to a baby. The physical activities, involved in parturition like uterine and, abdominal contractions, dilation of cervix and, passage of baby are collectively called labour., Labour is accompanied by localised sensation, of discomfort or agony called labour pains., Parturition is controlled by a complex, neuroendocrine mechanism. Signals arise from, the fully formed foetus and placenta cause, mild uterine contractions. It is acompanied by, rise in estrogen- progesterone ratio, increase in, oxytocin receptors in uterine muscles, ., They cause vigorous contractions of, myometrium of uterus at the end of pregnancy., The fully developed foetus gives signals, for the uterine contractions by secreting, Adrenocorticotropic Hormone (ACTH) from, pituitary and corticosteroids from adrenal, gland. This triggers release of oxytocin from, mother’s pituitary gland, which acts on uterine, muscles of mother and causes vigourous uterine, contractions. This leads to expulsion of the, baby from the uterus. It involves the following, three steps :, , Know The Institue :, Cord blood bank, Kolkata, India’s first, Government-run, cord blood bank, at Kolkata was, established in 2001, and is accredited, by AABB (American Association of Blood, Bank). The cord blood bank functions, occording to the central and state government, policies, rules and guidelines., Cord blood (umbilical cord blood) is the, blood that remains in the umbilical cord and, placenta, post delivery. Cord blood banking, is the process of collecting the cord blood,, extraction and cryogenically preserving for, its stem cells and other cells of the immune, system for future potential medical use. Cord, blood is rich in stem cells that can transform, into all sorts of blood cells. They can be, used to treat diseases that harm the blood, and immune system e.g. leukemia, certain, cancers, sickle cell anemia and some, metabolic disorders., , 1. Dilation stage : Uterine contractions begin, from top, forcing the baby towards the cervix., Contractions are accompanied by pain caused, by compression of blood vessels. Oxytocin, induced uterine contractions become stronger, and stronger due to stimulatory reflex. As the, baby is pushed down in the uterus, its head, comes to lie against cervix. Cervix gets dilated., The vagina also shows similar dilation., This stage of labour can normally last upto, few hours. It ends in rupturing of amniotic, membrane of foetus., 37
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Stage 1, Initial (Latent) Phase, , Active Phase, Uterus, , Foetus, , Uterus, , Cervix, , Foetus, , Effaced Cervix, , Vagina, Vagina, , Umbilical Cord, , Umbilical Cord, , Stage 2, Foetus, , Uterus, , Placenta, , Stage 3, Cervix, Umbilical Clamp, , Umbilical Cord, , Crowning of the, Head, , Umbilical Cord, , Vagina, , Fig. 2.18 : Parturition, 2. Expulsion stage : The uterine and abdominal, contractions become stronger. In normal, delivery, the foetus passes out through cervix, and vagina with head in forward direction. It, takes 20 to 60 min. The umbilical cord is tied, and cut off close to the baby’s navel., , Use your brain power, Why is it said that consumption of, mother milk is safest for the new born?, 2.11 Reproductive Health:, According to World Health Organisation, (WHO), reproductive health means total, wellbeing in all aspects of reproduction- its, emotional, behavioural and social aspects, along with the physical ones. Therefore, a, society with people having physically and, functionally normal reproductive organs and, normal emotional and behavioural interactions, amongst them in all sex-related aspects might, be called reproductively healthy society., , 3. After birth : After the delivery of the baby, the placenta separates from the uterus and, is expelled out as “after birth”, due to severe, contractions of the uterus. This process happens, within 10 to 45 minutes of delivery., 2.10 Lactation:, The mammary glands of the female start, producing milk at the end of pregnancy by the, process of lactation. Prolactin is the hormone, which is responsible for production of milk., Lactation helps the mother in feeding the new, born baby. The fluid secreted by the mammary, glands soon after child birth is called colostrum., Colostrum: It is the sticky and yellow fluid, secreted by the mammary glands soon after, child birth. It contains proteins, lactose and, mother’s antibodies e.g. IgA. The fat content, in colostrum is low. The antibodies present in it, helps in developing resistance for the new born, baby at a time when its own immune response, is not fully developed., , Of all the social goals of India, an, important one is to attain total reproductive, health. India was amongst the first few, countries in the world to initiate action plans, and programmes at a national level to improve, reproductive health. All these improved, programmes cover wider areas related to, reproduction. These programs are currently in, operation under the Reproductive and Child, Health Care (RCH) programmes., 38
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Goals of RCH Programmes:, 1. To create awareness among people about, various aspects related to reproduction., 2. To provide the facilities to people to, understand and build up reproductive, health., 3. To provide support for building up a, reproductively healthy society., 4. To bring about a change mainly in three, critical health indicators i.e. reducing, total infertility rate, infant mortality rate, and maternal mortality rate., , 7. By educating couples to reduce mortality, rate of new borns and maternal mortality, rate., The population in India which was, approximately 350 millions at the time of, independence, reached close to a billion mark, by 2000 and crossed 1.2 billion in May 2011., Now in 2020 population of India has crossed, 1.35 billions. The government is taking serious, measures to check this population growth. The, most important step to overcome this problem,, is to motivate society to have smaller families, by using various birth control methods., , The goals of RCH can be achieved by the, following ways:, 1. By introduction of sex education in, schools. Schools should be encouraged, to provide correct information to the, young so as to discourage children, from believing in myths and clear the, misconceptions about sex related aspects., Proper information about safe and hygenic, sexual practices, sexually transmitted, diseases (STD, AIDS), problems related, to adolescence and proper information, about reproductive organs., 2. With the help of audio- visual and the print, media, government and non- government, organisations should take various steps to, create awareness about various aspects, related to reproduction., 3. By educating the younger generation, about birth control measures, pre-natal, care of pregnant woman and post-natal, care of the mother and child, importance, of breast feeding., 4. By developing awareness about problems, arising due to uncontrolled population, growth, social evils like sex abuse and, sex related crimes and take up necessary, steps to prevent them., 5. By creating awareness about statutory ban, on amniocentesis for sex determination., 6. By creating awareness about child, immunization programmes., , 2.12 Birth control :, The birth control measures which, deliberately prevent fertilization are referred to, as contraceptives. The contraceptive methods, help to prevent unwanted pregnancies. An, ideal contraceptive should be easily available,, user friendly, effective and with no or least side, effects., Contraceptive methods are of two main, types i.e. temporary and permanent., a. Temporary methods:, These are of following types :, 1. Natural method/ Safe period / Rhythm, method : In the natural method, the principle, of avoiding chances of fertilization is used., A week before and a week after menstrual, bleeding is considered the safe period for sexual, intercourse. This idea is based on the fact that, ovulation occurs on the 14th day of menstrual, cycle. Its drawback lies in having a high rate, of failure., 2. Coitus Interruptus or withdrawal : In this, method, the male partner withdraws his penis, from the vagina just before ejaculation, so as to, avoid insemination. This method also has some, drawbacks, as the pre-ejaculation fluid may, contain sperms and this can cause fertilization., 3. Lactational amenorrhea (absence of, menstruation) : This method is based on the fact, that ovulation does not occur during the period, 39
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of intense lactation following parturition., Therefore, as long as the mother breastfeeds the, child fully, chances of conception are almost, negligible. However, this method also has high, chances of failure., , Diaphragm, , 4. Chemical means (spermicides): In this, method, chemicals like foam, tablets, jellies,, and creams are used by the female partner., Before sexual intercourse, if these chemicals, are introduced into the vagina, they adhere to, the mucous membrane, immobilize and kill the, sperms. It may cause allergic reaction. This, method also has chances of failure., Lippes loop, , 5. Mechanical means / Barrier methods:, In this method, with the help of barriers the, ovum and sperm are prevented from physically, meeting. These mechanical barriers are of three, types., i), , Fig. 2.19 : Mechanical means, , Condom: It is a thin rubber sheath that, is used to cover the penis of the male, during coputation. It prevents the entry, of ejaculated semen into the female, reproductive tract. This can prevent, conception. It is a simple and effective, method and has no side effects. “Nirodh”, is the most widely used contraceptive by, males. It is easily available and is given free, by the government. It should be properly, discarded after every use. Condom is also, a safeguard against STDs and AIDS., , Hormone, , Uterus, , IUD, , Cevix, Strings, Vagina, , Fig. 2.20 : Copper - T, , ii) Diaphragm, cervical caps and vaults:, These devices used by the female are made, up of rubber. They prevent conception, by blocking the entry of sperms through, the cervix. The device is inserted into the, female reproductive tract to cover the, cervix during copulation., iii), , Copper, , Lippes loop is a plastic double “s” loop. It, attracts the macrophages stimulating them to, accumulate in the uterine cavity. Macrophages, increase phagocytosis of sperms within the, uterus and acts as a contraceptive. Copper, releasing IUDs suppress sperm motility and the, fertilising capacity of sperms., The hormone releasing IUDs make the, uterus unsuitable for implantation and cervix, hostile to the sperms. It delays pregnancy for, longer period. The spontaneous expulsion,, occasional haemorrhage and chances of, infection are the drawbacks of IUDs., , Intra-uterine devices (IUDs) : These, clinical devices are plastic or metal objects., A doctor or trained nurse places the IUDs, into the uterus. These devices include, Lippes loop, copper releasing IUDs ( Cu-T,, Cu7, multiload 375) and hormone releasing, IUDs (LNG-20, progestasert)., 40
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b. Permanent Method:, The permanent birth control method in, men is called vasectomy and in women it is, called tubectomy., These are surgical methods, also called, sterilization. In vasectomy a small part of, the vas deferens is tied and cut where as in, tubectomy, a small part of the fallopian tube is, tied and cut. This blocks, gamete transport and, prevent pregnancy., , 6. Physiological (Oral) Devices : Physiological, devices are used in the form of tablets and, hence are popularly called pills. It is an oral, contraceptive, used by the female. The pill, contains progesteron and estrogen. They inhibit, ovulation, hence no eggs are released from the, ovary of the female using this pill and thus, conception cannot occur. They also alter the, quality of cervical mucus to prevent the entry, of sperms., The pills have side effects such as nausea,, weight gain, tenderness of breast and slight, blood loss between menstrual periods. The pill, “Saheli” is an oral contraceptive for females, which is nonsteroidal. Saheli is to be taken, once in a week. These pills are sponsored by, the Government., , Vas deferens, tied and cut, , A, , Always Remember, Saheli, is, now a part of the, National Family, Programme as an, oral contraceptive, pill in India., , Fallopian tubes, tied and cut, , 7. Other contraceptives : The birth control, implant is a contraceptive used by the female. It, is a tiny, thin rod about the size of a matchstick., It is implanted under the skin of the upper arm., They contain progesterone and estrogen., Their mode of action is similar to that of pills., They prevent pregnancy for 3-4 years., , B, , Fig. 2.22 : Permanent method, Medical Termination of Pregnancy (MTP) :, An intentional or voluntary termination, of pregnancy before full term is called Medical, termination of Pregnancy (MTP) or induced, abortion. MTP is essential in cases of unwanted, pregnancies or in defective development of, foetus. It is safe during the first trimester of, pregnancy. The defective development of, foetus is examined by amniocentesis., , Fig. 2.21 : Implanon/ Nexplanon, , 41
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Amniocentesis is a process in which, amniotic fluid containing foetal cells is collected, using a hollow needle inserted into the uterus, under ultrasound guidance. The chromosomes, are studied to see the abnormalities in the, developing foetus. But the dangerous trend, is the misuse of amniocentesis to determine, the sex of the unborn child. Frequently, if the, foetus is found to be female, it is aborted which, is totally illegal. So the Government of India, has legalised MTP Act in 1971, with strict, conditions to avoid its misuse., , Medical Termination of Pregnancy, (Amendment) Act 2017 under section 3 of the, MTP Act 1971 was enacted by Government, of India. The intention of MTP Act is to, reduce the incidence of illegal abortion and, consequent maternal mortality. As per the, provisions of the MTP Act, only the consent of, woman whose pregnancy is being terminated, is required. According to MTP Act pregnancy, may be terminated : 1. Within first 12 weeks, 2. More than 12 weeks but lesser than 20, weeks. The registered medical practitioner’s, opinion is mandatory stating the continuation, of the pregnancy would involve a risk to the, life of the pregnant woman or grave abnormal, physical or mental health or is substantial risk, to the child., , Amniocentesis : Used to extract foetal cells for genetic analysis., 1. Ultrasound used to determine the, position of the foetus in the uterus, 2. Needle inserted through the, abdominal and uterine wall, , Placenta, , 3. Amnionic fluid containing, foetal cells extracted, 4. Centrifuge of, extracted fluid, 5. Cells used in karyotype, and foetal cells, Amnionic, fluid, , Internet my friend, What are the effects of alcohol drinking, and smoking on foetus in pregnant women?, , Karyotype, , Risks associated with, amniocentesis, , 2.13 Sexually Transmitted Diseases (STDs) :, Diseases or infections which are, transmitted through sexual intercourse are, collectively called Sexually Transmitted, Diseases (STDs) or Venereal Diseases (VDs) or, Reproductive Tract Infections (RTI). The major, venereal diseases are syphilis and gonorrhoea., , 1. Miscarriage, 2. Needle injury to foetus, 3. Leaking amniotic fluid, 4. Infection, , Fig. 2.23 : Amniocentesis process, , Always Remember, Act of MTP : The Medical Termination, of Pregnancy (MTP) Act 1971 provides the, legal framework for MTP Act 2017., , Internet my friend, Collect information about other sexually, transmitted diseases., , Activity :, In a sonography clinic, we observe a, board saying ‘Sex selection and detection is, NOT done in this centre and is punishable, under PC-PNDT Act;, Find out what is PC-PNDT Act. Why, do you think such a mandate is essential?, 42
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Table 2.24 : Sexually Transmitted Diseases (STDs), Name of Disease Syphilis, , Gonorrhoea, , Causative agent, , Treponema pallidum (Bacteria), , Neisseria gonorrhoeae (Bacteria), , Incubation, period, Infection site, , 3-4 weeks, , Male – 2 to 14 days, Female – 7 to 21 days, Mucous membrane of urino-genital tract,, rectum, throat and eye., In male, partial blockage of urethra and, reproductive ducts, pus from penis, pain, and burning sensation during urination,, arthritis, etc., In female, pelvic inflammation of urinary, tract, sterility, arthritis, the children born, to affected mother suffer from gonococcal, opthalmia and gonococcal vulvovaginitis, of girls before puberty., , Symptoms, , Preventive, measures, , Treatment, , Mucous membrane in genital,, rectal and oral region., Primary lesion called chancre at, the site of infection. Chancre is, formed on external genitalia, skin, rashes and mild fever, inflamed, joints, loss of hair. Paralysis,, Degenerative changes occur in the, heart and brain., , Education about sex practices,, sex hygiene, avoiding sex with, unknown partner or multipartners,, using condom during coitus., Antibiotic-Penicillin, , Sex hygiene, using condom during coitus,, avoiding sex with unknown partner or, multipartners., Antibiotic-Cefixime, , IVF (In Vitro Fertization) :, It is a process of fertization where an, egg is combined with sperm outside the body, in a test tube or glass plate to form a zygote, under simulated conditions in the laboratory., The zygote or early embryos (with up to 8, blastomeres) could be then transferred into the, fallopian tube for further development., , 2.14 Infertility :, Infertility is defined as the inability, to conceive naturally after (one year of), regular unprotected intercourse. The causes, of infertility could be physical, congenital,, diseases, immunological or even psychological., The common physical causes in females are, polycystic ovary syndrome (PCOS), hormonal, imbalance, endometriosis while in male, it is, less sperm count and small size of penis., , ZIFT (Zygote Intrafallopian Transfer) :, ZIFT is an infertility treatment used, when there is a blockage in the fallopian tubes, which prevents the fertilization of egg by the, sperm., , Prior to 1978, infertile couple had two, options, adopt or be childless. Today infertile, couples have many options to have a child such, as fertility drugs, test tube babies, artificial, insemination, IUI, surrogate motherhood, etc., The couple could be assisted to have child /, children through certain special techniques, commonly known as Assisted Reproductive, Technologies (ART)., , In this method, egg is removed from, woman’s ovary. Fertilization of the egg with, sperms is brought about outside the body under, sterile conditions to form zygote by the process, called in vitro fertilization (IVF). The zygote, is then transferred to fallopian tube for further, development., 43
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Try This, IVF centres : Make a list of IVF centres, in Maharashtra., GIFT (Gamete Intrafallopian Transfer) :, Transfer of an ovum collected from a, donor into the fallopian tube of another female, who can provide suitable environment for its, fertilization and development., This technique called gamete intrafallopian, transfer (GIFT) has been developed for the, cases in which only the entrance to the oviducts, or the upper segment of the oviducts in blocked., In this procedure ova and sperms are directly, injected into regions of the oviduct, where, fertilization produces a blastocyst, which, enters the uterus via the normal route. GIFT, has a success rate of about 30 percent., ICSI (Intra Cytoplasmic Sperm Injection) :, ICSI is an in vitro fertilization procedure, in which a single sperm cell is injected directly, into cytoplasm of an ovum in the laboratory., Here the sperm has to naturally penetrate the, egg., Artificial Insemination (AI) :, In some infertility cases, the male partner, is unable to inseminate the female due to a very, low sperm count. This problem can be solved, by artificial insemination. In this technique,, the sperms are collected from the male and, artificially introduced into the cervix of female,, for the purpose of achieving a pregnancy, through in vivo fertilization (inside the body)., , Sperm bank / Semen bank:, A sperm bank or semen bank is a place, which collects, stores and provides human, sperms / semen. The semen is provided by, healthy males called sperm donors. The sperms, are stored in sperm bank by cryopreservation, method (at low temperature)., Can you recall?, Surrogate mother :, Some women have problem in, implantation of embryo in uterus. Such, woman can take help of the modern remedial, technique called surrogacy. In this, embryo, is implanted in surrogate mother, who is not, the biological mother., Adoption :, Adoption is a legal process by which, a couple or a single parent gets legal, rights, privileges and responsibilities that, are associated to a biological child for the, upbringing of the adopted child., An adoptive parent should be medically fit, and financially able to take care of the adopted, child. A person wishing to adopt a child must, be at least 21 years old but there is no legal, upper age limit for adoption., Always Remember, Tobacco, marijuana and other drugs, smoking may cause infertility in both men, and women. Nicotine blocks the production, of sperm and decreases the size of testicles., Alcoholism by men interferes with the, synthesis of testosterone and has an impact, on sperm count. Use of cocaine or marijuana, may temporarily reduce the number and, quality of sperm., , IUI (Intra Uterine Insemination) :, In this technique the process is somewhat, like that of artificial insemination, the only, difference is that the sperms are introduced into, the uterine cavity instead of cervix., , 44
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Always Remember, •, , •, , Always Remember, , Jayesh a young, married man of 26 yrs is, suffering from T. B. for the last 2 years., He and his wife are desirous of a child, but unable to have one, what could be, the possible reason? Explain., Neeta is 45 years old and the doctor, has advised her not to go for such a late, pregnancy. She however wants to be the, biological mother of a child, without, herself getting pregnant. is this possible, and how?, , 1. Cells of trophoblast do not form any part, of the embryo proper., 2. They form ectoderm of the chorion, (extra embryonic membrane)., 3. They play important role in formation of, placenta., , Activity :, 1. Prepare concept map on information of male reproductive system., , 2. Prepare concept map on information of female reproductive system., , 45
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Activity :, 3. Prepare concept map on information of menstrual cycle., , 4. Prepare concept maps on information of gametogenesis., Spermatogenesis, , Oogenesis, , 5. Prepare concept map on information of fertilization., , 46
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Exercise, Q. 1 Multiple choice questions., 1. The number of nuclei present in a zygote, is ……, a. two, b.one c. four, c.eight, , 8. Presence of beard in boys is a ............, a. primary sex organ, b. secondary sexual character, c. secondary sex organ, d. primary sexual character, , 2. Which of these is the male reproductive, organ in human?, a. sperm, b. seminal fluid, c. testes, d. ovary, , Q. 2 Answer in one sentence., 1. What is the difference between a foetus, and an embryo?, 2. Outline the path of sperm upto the, urethra., 3. Which glands contribute fluids to the, semen?, 4. Name the endocrine glands involved in, maintaining the sex characteristics of, males., 5. Where, does, fertilization, and, implantation occur?, 6. Enlist the external genital organs in, female., 7. Give two differences between blastula, and gastrula., 8. What is the difference between embryo, and zygote?, , 3. Attachment of embryo to the wall of the, uterus is known as…….., a. fertilization, b. gestation, c. cleavage, d. implantation, 4. Rupturing of follicles and discharge of, ova is known as .............., a. capacitation, b. gestation, c. ovulation, d. copulation, 5. In human female, the fertilized egg gets, implanted in uterus ......................, a. After about7 days of fertilization, b. After about 30 days of fertilization, c. After about two months of fertilization, d. After about 3 weeks of fertilization, 6. Test tube baby technique is called........., a. In vivo fertilization, b. In situ fertilization, c. In vitro fertilization, d. Artificial insemination, , Q. 3 Fill in the blanks:, 1. The primary sex organ in human male, is ………., 2. The…......... is also called the womb., 3. Sperm fertilizes ovum in, ………….. of fallopian tube., , 7. The given figure shows a human sperm., Various parts of it are labelled as A, B,, C, and D .Which labelled part represents, acrosome ?, , the, , 4. The disc like structure which helps in, the transfer of substances to and from, the foetus’s body is called…………, , A, B, C, D, , 5. Gonorrhoea is caused by ……………, bacteria., 6. The hormone produced by the testis is, ……………….., , a. B, , b. C, , c. D, , d. A, 47
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Q. 4 Short answer questions., 1. Write a note on budding in Hydra., 2. Explain the different methods of, reproduction occuring in sponges., 3. Write a note on IVF, 4. Comment on any two mechanical, contraceptive methods., 5. Write a note on tubectomy, 6. Give the name of causal organism of, syphilis and write on its symptoms., 7. What is colostrum?, , Q. 6 Long answer questions., 1. Explain the following parts of male, reproductive system along with, labelled diagram showing these partsTestis, vasa deferentia, epididymis,, seminal vesicle, proastate gland and, penis., 2. Describe female reproductive system, of human., 3. Describe the process of fertilization., 4. Explain the process by which zygote, divides and redivides to form the, morula., , Q. 5 Answer the following questions., 1. Describe the phases of menstrual cycle, and their hormonal control., 2. Explain the steps of parturition., 3. Explain the histological structure of testis., 4. Describe the structure of blastula., 5. Explain the histological structure of ovary, in human., 6. Describe the various methods of birth, control to avoid pregnancy., 7. What are the goals of RCH programme., 8. Which hormones are involved in, parturition?, 9. Which as the function of male accessory, glands?, 10. What is capacitation? Give it’s importance., , Project :, Prepare a chart showing information about, other STDs, mentioning causal organisms,, symptoms and control measures., , 48
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3, , Inheritance and Variation, Can you recall?, , 1. Is there a similarity between the parents, and offsprings?, 2. What are the roles of chromosomes in, living organisms?, 3. How are hybrid seeds produced?, 4. Which are the chromosomal disorders?, , •, , 3.1 Chromosomes and Mechanism of, inheritance., • The transmission of genetic information, from generation to generation is known as, heredity or inheritance. The mechanism, of inheritance was successfuly investigated, before chromosomes had been observed or, genes were known., • Gregor Mendel, son of the peasant farmer,, was born in Moravia in 1822. Gregor, Mendel first gave the accurate explanation, for the mechanism of inheritance by using, hybridization technique., • Inheritance of the seven traits in garden, pea (Refer the diagram below) plant were, 1., , studied individually one at a time or in, combination of two or three character at a, time. He processed the data mathematically, and statistically., Mendel postulated the principles of heredity, which then became the fundamental laws, of heredity, as proposed by Correns (1900)., He visualized that the traits as such are, not inherited physically but by ‘something’, present inside the gametic cell. To this, ‘something’, he coined term ‘factors’ that, are responsible for expression of a particular, trait/ character. He proposed that factors, are particulate in nature. The Mendelian, factors are now termed as ‘genes’. These, factors occur in pairs in the parents and, segregate from each other during gamete, formation without blending/ mixing., , Reasons for Mendel’s Success :, • His experiments were carefully planned, and involved large sample., • He carefully recorded the number of plants, of each type and expressed his results as, ratios., , Do you know ?, Seven pairs of contransting visible characters in pea plant (Pisum sativum), Pea Plant Traits, Seed shape Seed color, , Pod shape, , Pod color, , Flower, color, , Flower, location, , Round, , Yellow, , Inflated, , Green, , Purple, , Axial, , Wrinkled, , Green, , Constricted, , Yellow, , White, , Terminal, , Plant height, Tall, , Dominant, , Recessive, , 49, , Short, (Dwarf)
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• In the pea plant, contrasting characters can, be easily recognized., • The seven different charaters in pea, plant were controlled by a single factor, each. The factors are located on separate, chromosomes and these factors are, transmitted from generation to generation., • He introduced the concepts of dominance, and recessiveness., Before, learning, about, Mendel’s, experiments let us get acquainted with genetic, terms and symbols., 3.2 Genetic Terminology :, Character : It is a specific feature of an, organism e.g. height of stem., Trait : An inherited character and its detectable, variant e.g. Tall or dwarf., Factor : It is a unit of heredity, a particle, present in the organism which is responsible for, the inheritance and expression of a character., (factor is passed from one generation to the, next through gametes). Factor determines a, genetical (biological) character of an organism., Gene : It is a particular segment of DNA which, is responsible for the inheritance and expression, of that character., Alleles or Allelomorphs : The two or more, alternative forms of a given gene (factor), are called alleles of each other. They occupy, identical loci (positions) on homologous, chromosomes. Allele is a short form of, Allelomorph., Dominant : It is an allele that expresses its trait, even in the presence of an alternative allele i.e., in heterozygous condition only. Alternatively,, the allele that expresses in F1 is called, dominant. (It is an allele of a pair that masks, the expression of other allele in F1 generation.), Recessive : This allele is not expressed, in the presence of an alternative allele (in, heterozygous condition). It expresses only in, the presence of another identical allele. It is an, allele that does not express in F1 hybrid., 50, , Phenotype : The external apperance of an, individual for any trait is called phenotype for, that trait. It is observable and is determined by, different combinations of alleles. e.g. In pea,, for the height of stem (plant) tall and dwarf are, the two phenotypes (Tall is determined by TT, or Tt and dwarf by tt)., Genotype : Genetic constitution or genetic, make up of an organism with respect to a, particular trait. It is representation of the genetic, constitution of an individual with respect to, a single character or a set of characters. e.g., pea tall plants can have genotype TT or Tt and, dwarf has tt., Homozygous (pure) : An individual possessing, identical allels for a particular trait, is called, homozygous or pure for that trait., Homozygous breeds true to the trait and, produces only one type of gametes e.g., tall, with TT and dwarf with tt., Heterozygous : An individual possessing, contrasting alleles for a particular trait, is, called heterozygous. Heterozygous does not, breed true for that trait and produces two types, of gametes e.g. F1 generation hybrids (Tt)., Heterozygous individual is also called hybrid., Pure line : An individual or a group of, individuals (population) which is homozygous, or true breeding for one or more traits,, constitutes pure line i.e. plant which breeds true, for a particular character. It is a descendent of, a single homozygous parent produced after self, fertilization., Monohybrid : It is heterozygous for one trait, and is produced from a cross between two pure, parents differing in single pair of contrasting, characters e.g. Hybrid tall produced in a cross, between pure tall and pure dwarf parents. It is a, heterozygote for a single pair of alleles., F1 generation : It refers to the first filial, generation. It consists of all off-springs, produced from a parental cross. Alternatively, it, is first generation from a given mating between, pure parents having contrasting characters.
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F2 generation : The second generation, (progeny) produced by selfing (inbreeding) of, F1 generation offsprings is called second filial, generation. e.g. Progeny produced from a cross, between two F1individuals (e.g. Tt Tt)., Punnett square/checker board : It is a, probability table representing different, permutations and combination of fertilization, between gametes of the opposite mating types., In short, it is a diagrammatic representation of, a particular cross to predict the progeny of a, cross., Homologous, Chromosomes, :, The, morphologically, genetically and structurally, essentially identical chromosomes present, in a diploid cell, are called homologous, chromosomes. Such chromosomes synapse, during meiosis., Back cross : It is a cross of F1 progeny with, any of the parents (e.g. F1 tall pure tall; F1tall, pure dwarf i.e. Tt TT/tt)., Test cross : It is a cross of F1 progeny with, homozygous recessive parent (e.g. F1 tall , pure dwarf i.e. Tt tt). It is used to test the, homozygous/ heterozygous nature of hybrid. It, is a kind of back cross., Phenotypic ratio : It is the ratio of the offsprings, produced in F2 and subsequent generation with, respect to their physical appearence e.g. 3Tall :, 1 dwarf, is F2 ‘Phenotypic ratio’ in monohybrid, cross., Genotypic ratio : It is the ratio of the offsprings, produced in the F2 and subsequent generation, with respect to their genetic make up e.g. 1 TT, : 2Tt : 1 tt, is F2 genotypic ratio in monohybrid, cross., Monohybrid cross :, A cross between parents differeing in, only one heritable trait is called monohybrid, cross. e.g. cross of pure tall and pure dwarf, plants. Mendel performed the monohybrid, cross between two pea plants with only one, pair of contransting character., 51, , Activity :, Complete the following chart :, Phenotype, Genotype, , Tall, TT, , Gametes, , X, , Dwarf, , T, , First filial, , t, , Generation (F1), Selfing of F1, Genotype, , Tt, Tall, Tall Tall, Tt, Tt, , Gametes, , T, , Second filial, Generation (F2), , Male, gametes, , t, , Female, gametes, , T, Tt, , T, , t, Tt, , Tt, , t, , tt, , Dihybrid cross :, A cross between parents differing in two, heritable traits, is called dihybrid cross e.g., cross of pure tall, round seeded plant with, dwarf, wrinkled seeded plant. Mendel also, performed the dihybrid cross between pea, plants that differed in two pairs of contrasting, characters., , Activity :, Complete the following chart :, Parental generation, Phenotype, Genotype, Gametes, First filial, generation, (f1), , Round, yellow Wrinkled, green, X, seeds, seeds, RRYY, rryy, RY, , ry, RrYy, , Round, yellow seeds, , Genotype, , Round, yellow Round,, seeds, yellow seeds, RrYy, RrYy, , Gametes, , RY, Ry, rY, ry, , Selfing of f1, , RY, Ry, rY, ry
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F2 Generation :, Male, gametes, Female, gametes, , RY, , Ry, , rY, , 2. Law of segregation (Law of purity of, gametes) :, This law is based on the fact that the, alleles do not show any blending/ mixing and, both the alleles (characters) are recovered as, such in the F2 generation, though one of these, is not seen at the F1 stage. During formation of, gametes, these two alleles (factors) obviously, separate or segregate, otherwise recessive type, will not appear in F2., , ry, , RY, Ry, rY, ry, , The gametes which are formed are, always pure for a particular character (trait). A, gamete may carry either dominant or recessive, factor but not both. That’s why it is also called, as law of purity of gametes., , Use your brain power, There are 16 possible individuals in F2, generation. Try to find out the phenotypes as, well as the genotypic and phenotypic ratios., Can you tell?, Why are farmers and gardeners, advised to buy new F1 hybrid seeds every, year?, 3.3 Mendel’s Laws of Inheritance :, Mendel proposed three basic postulates on, the basis of which three laws were formulated., These are described below:, 1. Law of Dominance :, In monohybrid and dihybrid crosses, the, phenotypic characters are controlled by discrete, units, called factors. In a dissimilar pair of, factors, one member of the pair dominates, (i.e. dominant) over the other (i.e. recessive)., The law of dominance is used to explain, the expression of only one of the parental, characters of a monohybrid cross in F1 and the, expression of both in F2., Statement of Law of Dominance : “When, two homozygous individuals with one or more, sets of contrasting characters are crossed,, the alleles (characters) that appear in F1 are, dominant and those which do not appear in F1, are recessive”., , 52, , Statement of Law of Segregation : The law, states that “When hybrid (F1) forms gametes,, the alleles segregate from each other and enter, in different gametes”. The gametes formed are, pure in that they carry only one allele each, (either dominant allele or recessive allele)., Hence, this law is also described as “Law of, purity of gametes”., 3. Law of Independent Assortment :, This law is based on dihybrid cross., It is basic principle of genetics developed by, a Mendel. It describes how different genes, or alleles present on separate chromosomes, independently separate from each other, during, formation of gametes. These alleles are then, randomly united in fertilization. In dihybrid, cross, F2 phenotypic ratio 9:3:3:1 indicates, that the two pairs of characters behave, independent of each other. It can be concluded, that the two characters under consideration are, assorted independently giving rise to different, combinations., Statement of Law of Independent, Assortment: The law states that “When hybrid, possessing two (or more) pairs of contrasting, factors (alleles) forms gametes, the factors in, each pair segregate independently of the other, pair”.
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conclude that plant is heterozygous. Test cross, is also used to introduce useful recessive traits, in the hybrids of self pollinated plants during, rapid crop improvement programs., , Try This, Find the ratio of dihybrid test cross by, using punnett square., , Following is the graphic representation of, test cross (Fig. 3.1). Recessive parent is crossed, to find out unknown genotype., , 3.4 Back Cross and Test Cross :, a. Back cross : The F1 individuals obtained in, a cross are usually selfed to get the F2 progeny., They can also be crossed with one of the two, parents from which they were derived (either, recessive or dominant). Such a cross is known, as back cross., , 3.5 Deviations from Mendel’s findings :, Few generalizations were arrived at by, Mendel, on the basis of his experiments of, garden pea plant- such as,, i. Single trait Single gene Two alleles., ii. Two alleles show interaction in which one, is completely dominant., iii. Factors (genes) for different traits, present on different chromosomes assort, independently., With the passage of time, number of, deviations were observed/ identified in the, post-Mendelian era, that gave additional, information on the patterns of inheritance., These deviations are then described as NeoMendelism., , b. Test cross : The cross of F1 hybrid with the, homozygous recessive parent is known as a test, cross. It is used to test whether an individual is, homozygous (pure) or heterozygous(hybrid)., Test cross is easy, simple, repeatable and, predictable., Test cross can be used to find out genotype, of any plant with dominant expression. But it is, not known whether it is homozygous (pure) or, heterozygous for that trait. For example, A pea, plant having violet (purple) flowers is crossed, with a pea plant with white flowers. If all, flowers produced are violet, we can conclude, that plant is pure or homozygous and if we get, violet and white flowers in 1:1 ratio, we can, , Homozygous, recessive, , Internet my friend, Find out the principle involved in, heredity of sheep/ coat colour, , Homozygous, recessive, , X, , rr, , rr, , r, , r, , Rr, , Rr, , r, R, , R, RR, , R, Rr, Rr, All flowers are violet, Unknown flower is, homozygous dominant, , r, , Rr, , Rr, , Dominant phenotype, (Genotype unknown), , Rr, , r, , Result, , rr, rr, Half of the flowers are violet and, half of the flowers are white., , Interpretation, , Unknown flower is heterozygous, , Fig. 3.1 : Graphical representation of test cross, 53
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Parents :, , Do you know ?, , red flowers X white flowers, RR, rr, , The deviations are :, Gametes :, , a. Single trait, Single gene, two alleles showing interactions like, codominance and incomplete dominance., , Rr, , F1- hybrids :, , b. Single trait, Single gene, more, than two alleles (multiple allelism)., , Pink flowers, , F2 Generation : Selfing of F1, , c. Single trait, more than one genes, (Polygenic inheritance) showing different, epistatic interactions or additive effect., , R, , d. Single gene influencing many traits, (pleiotropy)., , r, , It was observed that the phenotypic, expression of a gene can be modified or, influenced by the other gene. These gene, interactions are of two types., i., , r, , R, , Intragenic interactions : Occur between, the alleles of same gene e.g. incomplete, dominance and co-dominance. It also, occurs between the multiple allele series of, a gene., , ii. Intergenic (non-allelic) interactions:, Occur between the allels of differentgenes present on the same or differentchromosomes. e.g. pleiotropy, polygenes,, epistasis, supplermetary and complementry, genes, etc. Some of these interactions are, discussed below :, a. Incomplete dominance:, In the incomplete dominance, both the, alleles (genes) of an allelomorphic pair express, themselves partially. One allele (gene) cannot, supress the expression of the other allele, (gene) completely. In such case, there is an, hybrid. A, intermediate expression in the F1, well-known example is the flower colour of, Mirabilis jalapa. If a red-flowered (RR) plant, is crossed with a white-flowered (rr) plant, then, F1 offsprings have pink (Rr) flowers., 54, , R, , r, , RR, red, Rr, pink, , Rr, pink, rr, white, , Result :, Genotypic ratio - 1RR : 2Rr : 1rr, Phenotypic ratio - 1Red : 2 Pink :1 White, b. Co-dominance :, In co-dominance, both the alleles (genes), of an allelomorphic pair express themselves, equally in F1 hybrids. Such alleles which are able, to express themselves equally independently in, hybrids, are called co-dominant alleles. Thus, in co-dominance both alleles are expressed., Red, RR, , Phenotype, Genotype, , White, WW, , X, , Parent, generation, R, , Gametes, , W, , Roan, , Roan, , RW, , RW, , F1, Generation, R, , Gametes, , W, , R, , W, , F2, Generation, , Phenotypic, ration :, Genotypic, ration :, , RR, , Red, 1, , RW, , RW, , Roan, 2, , WW, , White, 1, , RR : RW : WW, 1:2:1, , Fig. 3.2 : Representation of co-dominance, in cattle
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Classic example of co-dominance is coat, colour in cattle. There are two types one with, red coat (with red colour hair) and other with, white coat (with white hair). When red cattles, (RR) are crossed with white cattles (WW), F 1, hybrids (RW) are roan., , Table 3.3 : Few phenotypes and genotypes, in Drosophila, Phenotype, Genotype, , Roans have the mixture of red and white, colour hair. Thus both the traits are expressed, equally. In F2 generation red (RR), roans (RW), and white (WW) are produced in the ratio, 1:2:1. Thus in Co-dominance, the genotypic, and phenotypic ratios are identical., c. Multiple alleles :, More than two alternative forms (alleles), of a gene in a population accupying the same, locus on a chromosome or its homologue, are, known as multiple alleles. Multiple alleles arise, by mutations of the wild type of gene. A gene, can mutate several times producing a series of, alternative expression. Different alleles in a, series show dominant- recessive relation or may, show co-dominance or incomplete dominance, among themselves. Wild type is dominant over, all other mutant alleles., , GAMETES, , Phenotype, Genotype, HbA, , Genotype, OFFSPRINGS, , Phenotypes, , vg+, , Nicked wings, , vgni, , Notched wings, , vgno, , Strap wings, , vgst, , Vestigial wings, , vg, , Curiosity Box, 1. What is qualitative and quantitative, inheritance?, 2. Find out the traits of quantitative, inheritance in humans., Another good example of multiple alleles, is A, B, O blood grouping in human beings., d. Pleiotropy :, When a single gene controls two (or more), different traits, it is called pleiotropic gene, and the phenomenon is called pleiotropy, or pleiotropism. The phenotypic ratio is, 1:2 instead of 3:1 because of the death of, recessive homozygote. The disease, sickle-cell, anaemia, is caused by a gene Hbs. Normal or, healthy gene HbA is dominant. The carriers, (heterozygotes HbA/Hbs) show signs of mild, anaemia as their RBCs become sickle-shaped, i.e. half- moon- shaped only under abnormally, low O2 concentration., , In Drosophila, a large number of multiple, alleles are known. e.g. The size of wings from, normal wings to vestigial (no) wings, i.e., just, stumps, is due to one allele (vg) in homozygous, condition. The normal wing is wild type while, vestigial wing is recessive type., , PARENTS, , Normal wings, , Sickle-cell carrier, HbA HbS, HbS, , HbA HbA, Normal, 1, , , , HbA HbS, HbA HbS, HbS HbS, Sickle-cell anaemic, Sickle-cell carrier, 2, 1 (dies), , Fig. 3.4 : Representation of Pleiotropy, 55, , Sickle-cell carrier, HbA HbS, A, Hb, HbS
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The homozygotes with recessive gene Hbs, however, die of total anaemia. Thus, the gene, for sickle- cell anaemia is lethal in homozygous, condition and produces sickle cell trait in, heterozygous carrier. Two different expressions, are produced by a single gene., A marriage between two carriers will, produce normal, carriers and sickle-cell, anaemic children in 1:2:1 ratio. Sickle cell, anaemics die leaving carriers and normals in, the ratio 1:2. The heterozygotes or carriers can, be identified by microscopic examination of, blood., Internet my friend, 1. Find out the inheritance pattern in blood, groups of human beings., 2. Find out more about pleiotropy-(Sicklecell anaemia) and Polygenic inheritance, - (human skin colour), 3.6 Chromosomal Theory of Inheritance :, Gregor Johann Mendel published his work, on inheritance of traits in 1866 but for some, reasons, it remained unnoticed or unrecognised, till 1900, as communication was not easyin those, days. His work was not widely recognized. His, approach of using mathematics and statistics, to explain biological phenomenon was totally, new and unacceptable to the then biologists., As continuous variations were observed in, nature, Mendel’s concept of factors (genes) as, stable and discrete unit which controlled the, expression of characters, and that a pair of, alleles did not “blend” with each other, was not, accepted by his contemporaries. He also did, not know the physical location of the ‘factors’, (genes) in the gametic cell., In 1900, three scientists Hugo de Vries,, Correns and von Tschermak, independently, rediscovered Mendel’s work on the inheritance, of traits. Due to advancements in microcopy,, scientists were able to observe cell division, and the structure of chromosomes under, microscope., 56, , Walter Sutton along with Theodor Boveri, (1903) studied the parallel behaviour of, Mendel’s factors (genes) and behaviour of, chromosomes, at the time of meiosis., Based on these observations, chromosomal, theory of inheritance was put forth by Sutton, and Boveri. This theory identifies chromosomes, as the carriers of genetic material., This theory states that the chromosomes, are present in pairs in somatic cells. During, gamete formation homologous chromosomes, pair, segregate and assort independently during, meiosis. Thus, each gamete contains only one, chromosome from a pair., Nucleus of gametes contains chromosomes,, which carry all hereditary traits. Male and, female gametes (sperms and eggs) carry all, the hereditary traits.They are the link between, parents and offsprings. The fusion of haploid, male gamete and haplaid female gamete,, restores the diploid number of chromosomes of, the species., , Activity :, Observe the following diagram and, answer the questions given below -, , AAaa, , Meiosis I, A, , aa, , A, , Meiosis, II, A, , A, , a, , a, , Questions :, 1. What is homologous chromosome?, 2. In which phase of meiosis-I, homologous, chromosomes segregate?, 3. Where are genes located?, 4. Do genes and chromosomes have similar, behaviour? Justify.
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Function :, Chromosomes are carriers of heredity., Number of chromosomes :, The number of chromosomes is specific and, constant for a particular species, therefore it is, of great importance in the study of phylogeny, and taxonomy of the species., The term Ploidy speaks for the degree, of repetition of the primary basic number of, chromosomes (i.e. ‘x’) in a cell. When the, chromosome number in a cell is the exact, multiple of the primary basic number, then it is, called euploidy. Euploids include monoploid/, haploid (with one set of chromosomes where, x=n), diploids (2n-two sets of chromosomes),, triploids (3n-three sets of chromosomes),, tetraploid (4n-four sets of chromosomes) and, so on. When the chromosome number is not the, exact multiple of the haploid set, it is described, as Aneuploidy. Aneuploidy is either addition, or deletion of one or more chromosome (s) to, the total number of chromosomes in a cell (see, the chart 3.5)., Structure of chromosome :, Chromosomes are best visible under, microscope, when the cell is at metaphase, stage. It is because at this stage chromosomes, are highly condensed. Typical chromosome, , Always Remember, 1. Genes and chromosomes occur always in, pairs in diploid organism., 2. Alleles located on chromosome segregate, along with chromosome during gamete, formation., Can you recall?, 1. What is chromosome?, 2. How many chromosomes are present in, human somatic and reproductive cell?, 3.7 Chromosomes :, Chromosomes are filamentous bodies, present in the eukaryotic nucleus. The term, chromosomes (Gr., Chromo = colour, soma, = body) was coined by W. Waldeyer (1888)., The size of chromosome varies from species to, species. Each metaphase chromosome varies, from 0.1 to 33 m in length and 0.2 to 2 m in, thickness. Chromosomes are visible during cell, division. They are capable of self replication, and play vital role in heredity, mutation,, variation, and evolutionary devlopment of, eukaryotic species. Chemically eukaryotic, chromosomes are made of DNA, histone and, non-histone proteins., , Ploidy, , Euploidy, , Monoploidy, (n), , Diploidy, (2n), , Aneuploidy, , Polyploidy, (3n, 4n, 5n, etc), Hypoploidy, , Monosomy, (2n-1), , Nullisomy, (2n-2), , Hyperploidy, , Trisomy, (2n+1), , Chart 3.5 : Variation in chromosome number (ploidy), 57, , Tetrasomy, (2n+2)
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consists of two chromatides joind together at, centromere or primary constriction. Primary, constriction constists of a disk shape plate called, kinetochore. It is at the kinetochore, spindle, fibres get attached during cell division. Besides, primary constriction, some few chromosomes, possess additional one or two constrictions, called secondary constriction. At secondary, constriction I, nucleolus becomes organized, during interphase. A satellite body (SAT body), is attached at secondary constriction II, in very, few chromosomes. Each chromatid in turn, contains a long, unbranched, slender, highly, coiled DNA thread, called Chromonema,, extending through the length of chromatid., Chromatid consists a double stranded, DNA molecule which extends from one end of, chromosomes to other., Telomere, Chromonemata, , Chromomeres, Secondary, constriction (ii), , Centromere, , Primary, constriction, (centromere), , Matrix, Nucleolus, Satellite, A, , B, , Chromonemata, Secondary, constriction (i) or, nucleolar organizer, , Depending upon the position of centromere, there are four types (shapes) of chromosomes, viz. Acrocentric (j shaped), Telocentric, (i shaped), Submetacentric (L shaped), and Metacentric (V shaped). The ends of, chromosome (i.e. chromatids) are known as, telomeres., Sex Chromosomes :, The chromosomes which are responsible, for the determination of sex are known as sex, chromosomes (Allosomes). Human being and, other mammals have X and Y Chromosomes, as sex chromosomes., X chromosome is straight, rod like and, longer than Y chromosome. X chromosome, is metacentric, while Y chromosome is, acrocentric. X chromosome has large amount, of euchromatin (extended region) and small, amount of heterochromatin (highly condensed, region). Euchromatin has large amount of, DNA material, hence genetically active. Y, chromosome has small amount of euchromatin, and large amount of heterochromatin, hence it, is genetically less active or inert. Both X and, Y chromosome show homologous and nonhomologous regions. Homologous regions, show similar genes while non-homologous, regions show dissimilar genes., Non-Homologous regions, , A : Parts of chromosomes B : Showing, secondary constrictions and details, Fig. 3.6 : Structure of Chromosome, , Centromere, , Activity :, Study the types of chromosome, according to position of centromere. Observe, and complete the following table., Types of, Name of, Position of, Chromosome Chromosome Contromere, Metacentric, Acrocentric, , -, , -, , At one end, , Homologous region, , Fig. 3.7 : Structure of X and Y chromosomes, (in humans), Crossing, over occurs only between, homologous regions of X and Y chromosomes., Non-homologous region of X chromosome is, longer and contains more genes than that of, 58
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non-homologous region of Y chromosome. Xlinked genes are persent on non-homologous, region of X-chromosome while Y linked genes, are persent on non-homologous region of Ychromosome., Can you tell?, 1. What are allosomes?, 2. Compare X and Y chromosomes., 3. In which region of chromosomes does, crossing over take place?, 3.8 Linkage and Crossing Over :, Linkage :, It is a known fact that several genes are, present on the chromosome. As chromosomes, are carriers of heredity, these genes have, tendency to be inherited together. Such genes, are called linked genes. This tendency of two or, more genes present on the same chromosomes, that are inherited together is known as linkage., Linkage was discovered in plants by Bateson, and Punnett and in animals by T. H. Morgan., Linkage is of two kinds - complete and, incomplete linkage:, I. Complete linkage : The linked genes which, are closely located on the chromosome do not, separate (no crossing over) and inherit together., They are called completely linked (strongly, linked) genes and the phenomenon of their, inheritance is called complete linkage. Thus, the parental traits are inherited in offsprings., e.g. X chromosome of Drosophila males- show, complete linkage., II. Incomplete linkage : The linked genes, which are distantly located on the same, chromosome and have chances of separation, by crossing over, are known as incompletly, linked (weakly linked) genes. The phenomenon, of their inheritance, is called incomplete, linkage. Thus, new traits occur in offsprings., e.g. In Zea mays - colour and shape of grain, show incomplete linkage., Linkage Groups :, All the linked genes in a particular, chromosome, constitute a linkage group., 59, , The number of linkage groups of a particular, species corresponds to its haploid number of, chromosomes. e.g. Drosophila melanogaster, has 4 linkage groups that corrrspond to the, 4 pairs of chromosomes. Garden pea has 7, linkage groups and 7 pairs of chromosomes., Sex-linkage :, The transmission (inheritance) of X - linked, and Y-linked genes from parents to offspring,, is called sex-linked inheritance. Sex-linked, inheritance is of three types viz. X-linked, Ylinked and XY-linked. Sex linkage is of two, kinds :, a. Complete sex linkage : It is exhibited by, genes located on non-homologous regions of, X and Y chromosomes. They inherit together, because crossing over does not occur in this, region., Examples of X-linked traits are, haemophilia, red-green colour blindness,, myopia (near sightedness) and for Y-linked are, hypertrichosis, Ichthyosis, etc., b. Incomplate sex linkage : It is exhibited by, genes located on homologous regions of X and, Y chromosomes. They do not inherit together, because crossing over occurs in this region., Examples of X-Y linked traits are total colour, blindess, nephritis, retinitis pigmentosa, etc., Crossing Over :, Crossing over is a process that produces, new combinations (recombinations) of genes by, interchanging and exhanging of corresponding, segments between non-sister chromatids of, homologous chromosomes. It occurs during, pachytene of prophase I of meiosis. The, term crossing over was coined by Morgan., The mechanism of crossing over consists, four sequential steps such as synapsis, tetrad, formation, crossing over and terminalization., This you have already studied in the chapter, on cell division in class XI. The phenomenon, of crossing over is universal and it is necessary, for the natural selection, because it increases, the chances of variation.
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Use your brain power How many linkage groups are in human being and maize?, • Morgan’s Experiments showing linkage, and crossing over :, , Know the Scientist :, , Morgan used Drosophila melanogaster, (fruit fly) for his experiments because,, Drosophila can easily be cultured in laboratory., It’s life span is short, about two weeks. More, over, it has high rate of reproduction., Morgan carried out several dihybrid cross, experiments in fruit fly to study genes that are, sex-linked. The crosses were similar to dihybrid, crosses, as carried out by Mendel in Pea., For example, Morgan and his group crossed, yellow-bodied, white eyed female to the wild, type with brown-bodied, red eyed males and, intercrossed their F1 progeny., , Thomas Hunt Morgan, was an American biologist., He used fruit fly (Drosophila, melanogaster) in genetic, reserch and established the, chromosomal theory of, T. H. Margan heredity. He also discovered, (1866-1945) the principle of linkage, sex, linkage and crossing over., Margan’s work played key role in the, field of genetics. He was awarded a Nobel, Prize in 1933, in Physiology and Medicine., , Cross II, , Cross I, yw, , x, , Parental, Yellow, White, , yw, , w, , y+ w+, , m, , x, w, m, White, Miniature, , Wild type, , yw, , w, , w+, , m+, , Wild type, , m, , w, , m, , F1 generation, y+ w+, Wild type, Parental type, (98.7%), y+ w+, Wild type, yw, , F2 generation, , Yellow, White, y+ w+, yw, Wild type, yw, yw, Yellow, White, , w+ m +, Wild type, , Yellow, White, Recombinant, types (1.3%), , White, Miniature, , Parental, type (62.8%), , y+ w, , w+, , m+, , Wild type, , Brown, White, +, , yw, , w, , Yellow, Red, , Recombinant, types (37.2%), w+, , m, , White, Miniature, , m, , w, , m+, , White, Miniature White, Normal, , y+ w, , w+, , yw, Brown, White, , m+, , w, m, Wild type, , y w+, , w, , m, , w+, , m, , w, m, Miniature, w, , m+, , w, m, w, m, White, Miniature White, Normal, , yw, Yellow, Red, , Fig : 3.8 : Linkage and crossing over, 60
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He observed that the two genes did not, Some characters are influenced by, segregate independently of each other and F2 dominant genes while some other are by, ratio deviated very signiticantly from 9:3:3:1 recessive genes, present on autosomes. For, ratio., example,, Morgan and his group knew that the genes • Autosomal dominant traits like Widow’s, were located on X chromosome and stated that, peak and Huntington’s disease, etc., when two genes in a dihybrid cross are situated • Autosomal recessive traits like Phenyl, on the same chromosome, then the proportion, ketonuria (PKU), Cystic fibrosis and Sickle, of parental combination is much higher than, cell anaemia., non-parental type. This occurs due to physical, association or linkage of the two genes. He also a. Widow’s peak :, A prominent “V” shaped hairline on, found that, when genes are grouped on the same, forehead is described as widow’s peak. It is, chromosome, some genes are strongly linked., determined by autosomal dominant gene., They show very few recombinations (1.3 %)., When genes are loosely linked i.e. present far Widow’s peak occurs in homozygous dominant, away from each other on chromosome, they (WW) and also heterozygous (Ww) individuals., Individuals with homozygous recessive (ww), show more (higher) recombinations (37.2 %)., genotype have a straight hair line (no widows, For example, the genes for yellow body, and white eye were strongly linked and showed, peak). Both males and females have, only 13 percent recombination (in cross-I). equal chance of inheritance., White bodied and miniature wings showed, Widow’s peak, No widow’s peak, 37.2 percent recombination (in cross-II)., Cross I shows crossing over between genes y, and w. Cross II shows crossing over between, genes white (w) and miniature wing (m). Here, dominant wild type alleles are represented with, (+) sign., Fig. 3.9 : Widow’s peak and straight hair, line, , Always Remember, Parental combinations occur more, due to linkage and new combinations less due, to crossing over., 3.9 Autosomal Inheritance :, Human somatic (2n) cell contains, 23 pairs of chromosomes. They can be, divided functionally as autosomes and sex, chromosomes. A single pair of chromosomes is, involved in sex determination and remaining 22, pairs are called autosomes. Autosomes control, a variety of traits other than sex. These traits, are called autosome linked traits. Transmission, of body characters other than the sex linked, traits from parents to their offsprings through, autosomes, is called autosomal inheritance., 61, , b. Phenylketonuria (PKU):It is an inborn metabolic disorder caused, due to recessive autosomal genes. When, recessive genes are present in homozygous, condition, phenylalanine hydroxylase enzyme, is not produced. This enzyme is essential, for conversion of amino acid phenylalanine, into tyrosine. Due to absence of this enzyme,, phenylalanine is not converted into tyrosine., Hence, phenylalanine and its derivatives, are accumulated in blood and cerebrospinal, fluid (CSF). It affects development of brain, and causes mental retardation. Excess, phenylalanine is excreted in urine, hence this, disease is called phenylketonuria.
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Autosomal recessive traits appear in both, sexes with equal frequency. These traits tend to, skip generations., 3.10 Sex Linked Inheritance :, Genes located on non-homologous region, of sex chromosomes, are called sex-linked, genes. The traits that are determined by sex, linked genes, are called sex-linked traits., The inheritance of sex linked genes from, parents to their offsprings, is called sex linked, inheritance. There are two types of sex-linked, genes as X-linked genes and Y-linked genes., a. X-linked (sex linked) genes :, The X linked genes are located on non, homologous region of X chromosome and, these gene do not have corresponding alleles, on Y chromosome., Female has two X chromosomes. In female, two recessive sex linked genes are required, for expression of sex linked traits. If one X, chromosome carries a recessive gene for sexlinked trait (defect) its effect is suppressed, by the dominant gene present on other X, chromosome. The females with one recessive, gene are carriers. The carrier female is, physically normal as she does not suffer from, the disease (disorder)., Male has only one X-chromosome. If, X chromosome carries X-linked recessive, gene for sex linked trait, then it is expressed, phenotypically, because there is no dominant, gene on Y chromosome to suppress its, effect. Therefore, sex-linked / X-linked traits, appear more frequently in males than in the, females. Examples of X-linked traits include, haemophilia, colour blindness, night blindness,, myopia, muscular dystrophy, etc., b. Y-linked (Holandric) genes :, Genes located on non-homologous region, of Y chromosome, are called Y linked genes., The Y-linked genes are inherited directly from, male to male. In man, the Y-linked genes such, 62, , as hypertrichosis is responsible for excessive, development of hair on pinna of ear. This, charater is transmitted directly from father to, son., Internet my friend, Collect information of Ishihara’s Test for, colour blindess., Colour blindness :, Colour blindness is X-linked recessive, disorder where person is unable to distinguish, between red and green colours as both the, colours appear grey. It is caused due to recessive, X-linked genes (XC) which prevents formation, of colour sensitive cells, the cones, in the retina, of eye., The homozygous recessive females (Xc, Xc) and hemizygous recessive male (XcY) are, unable to distinguish between red and green, colours. The frequency of colour blind women, is much less than colour blind men. Dominant, X linked gene (XC) is necessary for formation of, colour sensitive cells in the retina of eye. Thus,, genotypes of male and female individuals can, be represented as followsSex, Male, , Normal, C, , XY, , Female XCXC, , Colourblind, , Carrier, , c, , XY, XcXc, , XCXc, , The inheritance of colourblindness can, be studied in the following two types of, marriages:1. Marriage between colour blind male with, normal female, will produce normal visioned, male and female offspring in F1. The sons have, normal vision but daughter will be carrier for, the disease.
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Parents:, , Colour blind, male, , Genotype, , XcY, , Gametes : Xc, , F1 :, , XCXc, , are dominant over the recessive genes for, haemophilia. The person having recessive gene, for haemophilia is deficient in clotting factors, (VIII or IX) in blood. Even minor injuries cause, continuous bleeding, hence haemophilia is also, called as bleeder’s disease., , Normal, female, , X, , XCXC, Y, , XCXc, , XC, , XCY, , Carrier daughters, ( 50% ), , XC, , The recessive gene for haemophilia is, located on non homologous region of X, chromosome. As there is no corresponding allele, on Y chromosome to suppress its expression, so, men suffer from this disease. Women suffers, only when both X chromosomes have recessive, genes (alleles)., , XCY, , Normal sons, ( 50% ), , Fig. 3.10 : Sex linked inheritance, (colour blindness), 2. Marriage between carrier female (daughter), and normal male will produce female offsprings, with normal vision but half of them will be, carriers for the disease. Half of male offsprings, will be normal while remaining half will be, colour blind., Parents:, , Carrier, Daughter, , Genotype, Gametes : XC, , F1 : XCXC, Normal, Female, 25%, , X, , Normal, Male, , XCXc, , XCY, Xc, , XCY, Normal, Male, 25%, , XC, , The genotype of male and female, individuals can be represented as followSex, Normal, Male, XHY, Female XHXH, , Haemophilic Carrier, XhY, XhXh, XHXh, , Like colour blindness, haemophilia also, shows criss-cross inheritance. The inheritance, of haemophilia can be studied with the help of, following examples 1. Marriage between the Haemophilic male, and normal female., , Y, , XcY, XCXc, Carrier Colourblind, Female, Male, 25%, 25%, , Parents:, , Haemophic, male, , Genotype, , XhY, , Gametes : Xh, , Fig. 3.11 : Sex linked inheritance (colour, blindness), From above example, it is clear that the, X linked recessive gene for colour blindness, is inherited from colourblind father to his, grandson through his daughter. This type of, inheritance is called as cris-cross inheritance., Haemophilia (Bleeder’s disease) :, Haemophilia is X-linked recessive disorder, in which blood fails to clot or coagulates, very slowly. The genes for normal clotting, 63, , F1 :, , XHXh, , Normal, female, , X, , XHXH, Y, , XHXh, , Carrier daughters, ( 50% ), , XH, , XHY, , XH, , XHY, , Normal sons, ( 50% ), , Fig. 3.12 : Sex linked inheritance, (Haemophilia)
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2. Marriage between carrier female (daughter), and normal male., Parents:, , Carrier, Daughter, , Genotype, , XHXh, , Gametes : XH, , F1 : XHXH, Normal, Female, 25%, , X, , Normal, Male, , German biologist, Henking in 1891,, while studying spermatogenesis of the squash, bug (Anasa tristis), noted that 50% of sperms, receive the unpaired chromosomes while other, 50% sperm do not receive it. Henking gave, a name to this structure as the x-body but he, could not explain its role in sex determination., Further investigations by other scientists led, to conclusion that the “x-body” of Henking, was infact a chromosome and gave the name, ‘X-Chromosome’., , XHY, Xh, , XHY, Normal, Male, 25%, , XH, , On the other hand, some species in which, the organism has either male or female, reproductive organs, is said to be dioecious or, unisexual. Humans are dioecious., , Y, , XhY, XHXh, Carrier Colourblind, Female, Male, 25%, 25%, , Fig. 3.13 : Sex linked inheritance, (Haemophilia), , a. Sex Determination in human beings :, The chromosomal mechanism of sex, determination in human beings is XX-XY type., In human beings, the nucleus of each somatic, cell contains 46 chromosomes or 23 pairs, of chromosomes. Out of these, 22 pairs are, autosomes and one pair of sex chromosomes., , Do you know ?, Haemophilia is also referred as “The, royal disease”, because it affected the royal, families of England, Germany, Russia and, Spain in the 19th and 20th centuries. Queen, Victoria of England, who ruled from 18371901, was belived to have been the carrier of, haemophilia. She passed the trait on to her, three of nine children., , Human female has a pair of XX,, homomorphic sex chromosomes while male, has XY, heteromorphic sex chromosomes., Thus genotype of :, Female = 44 Autosomes + XX, Male = 44 Autosomes + XY, , Find out, , During gamete formation in male,, the diploid germ cells in testis undergo, spermatogenesis to produce two types of haplaid, sperms, 50% sperms contain 22 autosomes and, X chromosome while, 50% sperms contain 22, autosomes and Y chromosome., , Aarya shows normal blood clotting, but her mother is haemophilic. Ramesh, shows normal blood clotting but his father is, haemophilic. If Ramesh and Aarya were to, marry, then find out the posible phenotypes of, their offsprings., 3.11 Sex Determination :, The mechanism by which sex is established, is termed as sex determination. The term sex, refers to sexual phenotype. In some species,, both male and female reproductive organs are, present in same organism. It is discribed as, bisexual or hermaphrodite or monoecious., 64, , In Female, the diploid germ cells in, ovaries undergo oogenesis to produce only one, type of egg. All eggs contain 22 autosomes, and X chromosome. Thus human male is, heterogametic and female is homogametic., If sperm containing X chromosome, fertilizes egg (ovum), then diploid zygote is, formed, that grows into a female child. If
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P generation, Male, , Female, , Parents :, , Male, , X, , Female, , Genotype, , 2n+ZZ, , n+Z n+Z, , 2n+ZW, , n+Z, , Gametes :, , XY, , Meiosis, , Gametes X Y, , n+W, , XX, , F1 :, , XX, Fertilization, , 2n+ZZ, , 2n+ZW, , Male bird, , Female bird, , Fig. 3.15 : Sex determination in birds, F1 generation, , X, , XX, , Sperm Y, , Something Interesting, , XY, , X, , Eggs, , Female, XX, , Male, XY, , X, , Female, , Male, , Conclusion : 1:1 sex ratio is produced, , Fig. 3.14 : Sex determination in, human beings, sperm containing Y chromosome fertilizes the, egg, then diploid zygote is formed that grows, into a male child., This indicates that the sex of a child, depends on the type of sperm fertilizing the, egg and hence the father is responsible for, determination of sex of child and not the, mother. Due to lack of knowledge, women are, often blamed for giving birth to female child., b. Sex Determination in birds :, In birds, the chromosomal mechanism of, sex determination is ZW-ZZ type. In this type, females are heterogametic and produce two, types of eggs; 50% eggs carry Z- chromosome,, while 50% eggs carry W- chromosome., Males are homogametic and produce, one type of sperms. Each sperm carries a Zchromosome. Thus sex of individual depends, on the kind of egg (ova) fertilized by the sperm., , 65, , In Bonellia viridis, the environmental, factors determine the sex of individual., The sex of worm Bonellia viridis depends on, which location the Bonellia larva gets settled., The marine female Bonellia worm has, about 10 cm long body. She has a proboscis, that can extend over a meter in length. If, a Bonellia larva settles on the seafloor, it, becomes a female., However when, a larva lands on a, female’s proboscis and enters the female’s, mouth, it migrates into her uterus and, differentiates into a male. Male lives as, parasite in uterus of female fertilizing her, eggs., , c. Sex Determination in honey bees :, In honey bees, chromosomal mechanism, of sex determination is haplo-diploid type. In, this type, sex of individual is determined by, the number of set of chromosomes received., Females are diploid (2n=32) and males are, haploid (n=16). The female produces haploid, eggs (n=16) by meiosis and male produces, haplaid sperms (n=16) by mitosis. If the egg, is fertilized by sperm, the zygote develops into
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a diploid female (2n=32) (queen and worker), and unfertilised egg develops into haploid male, (n=16) (Drone) by way of parthenogenesis., The diploid female gets differentiated, into either worker or queen depending on the, food they consume during their development., Diploid larvae which get royal jelly as food, develops into queen (fertile female) and other, develops into workers (sterile females)., Female, 2n=32, Meiosis, , Parents, , Gametes n=16, , n=16, , Male, n=16, Mitosis, n=16, , without, fertilization, (parthenogenesis), , F1, , n=16, (Haploid), Male, , 2n=32, (Diploid), Female, , Depending upon which chain of, haemoglobin is affected, thalassemia is, classified as alpha-thalassemia and betathalassemia. It is caused due to deletion or, mutation of gene which codes for alpha () and, beta () globin chains that result in abnormal, synthesis of haemoglobin. In Thalassemia,, person shows symptoms like anaemia, pale, yellow skin, change in size and shape of RBCs,, slow growth and development, dark urine, etc., Massive blood transfusion is needed to these, patients. Thalassemia differs from sickle-cell, anaemia. The former is a qualitative problem, of synthesising few globin molecule, while the, latter is a qualitative problem of synthesising, an incorrectly functional globin., Down’s Syndrome (21st trisomy) :, Down’s syndrome is named after the, physician John Langdon Down who first, described this autosomal chromosomal disorder, in 1866., , Fig. 3.16 : Sex determination in honey bee, 3.12 Genetic Disorders :, Genetic Disorders are broadly grouped, into two categories as, Mendelian disorders, and chromosomal disorders, Mendelian, discorders are mainly caused due to alteration, or mutation in the gene. e.g. thalassemia, sicklecell anaemia, colourblindness, haemophilia,, phenylketonuria, etc. On the other hand,, chromosomal disorders are caused due to, absence or excess of one or more chromosomes, or their abnormal arrangment. For eg, Down’s, syndrome, Turner’s syndrome, Klinefelter’s, syndrome etc., Thalassemia :, Thalassemia is an autosomal, inherited, recessive disease. Haemoglobin molecule is, made of four polypeptide chains- 2 alpha (), and 2 beta () chains. The synthesis of alpha, chains are controlled by two closely linked, genes (HBA1 and HBA2) on chromosome, 16 while the synthesis of beta chain is controlled, by a single gene (HBB) on chromosome 11., 66, , Fig. 3.17 : Down’s Syndrome, This Syndrome is caused due to an extra, copy of chromosome number 21st. It shows, presence of three copies of 21st chromosome, instead of homologous pair. These individuals, will have 47 chromosomes instead of the, normal number 46. 21st Trisomy occurs due, to non-disjuction or failure of separation of, chromosomes (autosomes) during gamete, formation. The incidence of non-disjunction, is distinctly higher in mothers who are over 45, years old.
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These patients have mild or moderate, mental retardation and skeletal development, is poor. Distinct facial features like small, head, ears and mouth, face is typically flat, and rounded with flat nose, open mouth and, protruding tongue, eyes slant up and out with, internal epicanthal folds, flat hands and stubby, fingers and palm is broad with single palmer, crease., Down Syndrome - Trisomy 21, , 1, , 2, , 9, , 10, , 3, , 4, , 11 12, Trisomy, , 5, , 6, , 7, , 8, , 13, , 14, , 15, , 16, , Klinefelter’s syndrome (XXY males) :, It is chromosomal disorder caused due to, extra X chromosome in males. Thus genotype, of individuals is 44 + XXY. They are described, as feminized males. Extra chromosome is a, result of non-disjunction of X-chromosome, during meiosis. Individual is male and has, over all masculine development. Voice pitch, is harsh and have under developed testis. They, are tall with long arms, feminine development, (development of breast i.e. Gynaecomastia), and no spermatogenesis, therefore, individuals, are sterile., , or, 17, , 18, , 19, , 20, , 21, , 22, , XX, , Turner’s Syndrome :, (X monosomy / XO females), It is sex chromosomal disorder caused, due to non-disjunction of chromosome during, gamete formation. Individual born with, Turner’s syndrome has 44 autosomes with XO., They are phenotypically female. They have a, short stature (height) and webbed neck, lower, posterior hair line, broad shield-shaped chest,, poorly developed ovaries and breast, and low, intelligence., , XY, , Fig. 3.18 : Karyotype of Down’s syndrome, , Activity :, Study the complementary and supplementary interaction (digenic interactions) both in plants and animals, , 67
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Exercise, Q. 1 Multiple choice questions., 1. Phenotypic, ratio, of, incomplete, dominance in Mirabilis jalapa., a. 2 : 1 : 1, b. 1 : 2 : 1, c. 3 : 1, d. 2 : 2, 2. In dihybrid cross, F2 generation offsprings, show four different phenotypes while the, genotypes are ................, a. six, b. nine, c. eight, d. sixteen, 3. A cross between an individual with, unknown genotype for a trait with, recessive plant for that trait is .............., a. back cross, b. reciprocal cross, c. monohybrid cross d. test cross, 4. When phenotypic and genotypic ratios, are the same, then it is an example of, ............, a. incomplete dominance, b. complete dominance, c. Multiple alleles, d. cytoplasmic inheritance, 5. If the centromere is situated near the end, of the chromosome, the chromosome is, called ................, a. Metacentric, b. Acrocentric, c. Sub-Metacentric d. Telocentric, 6. Chromosomal theory of inheritance was, proposed by ................, a. Sutton and Boveri, b. Watson and Crick, c. Miller and Urey, d. Oparin and Halden, 7. If the genes are located in a chromosome, as p-q-r-s-t, which of the following gene, pairs will have least probability of being, inherited together?, a. p and q, b. r and s, c. s and t, d. p and s, 68, , 8. Find the mis match pair :a. Down’s syndrome = 44 + XY, b. Turner’s syndrome = 44 + XO, c. Klinefelter syndrome = 44 + XXY, d. Super female = 44 + XXX, 9. A colourblind man marries a woman,, who is homozygous for normal colour, vision ,the probability of their son being, colourblind is –, a. 0%, b. 25%, c. 50%, d. 100%, Q. 2 Very Short Answer Questions., 1. Explain the statements :, a. Test cross is back cross but back cross, is not necessarily a test cross., b. Law of dominance is not universal., 2. Define the following terms :, a. Dihybrid cross, b. Homozygous, c. Heterozygous, d. Test cross, 3. What is allosome?, 4. What is crossing over?, 5. Give one example of autosomal recessive, disorder., 6. What are X-linked genes?, 7. What are holandric traits?, 8. Give an example of chromosomal, disorder caused due to non-disjunction, of autosomes., 9. Give one example of complete sex, linkage?, Q. 3 Short Answer Questions., 1. Enlist seven traits of pea plant selected/, studied by Mendel., 2. Why law of segregation is also called the, law of purity of gametes?, 3. Write a note on pleiotropy., 4. What are the reasons of Mendel success?
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5. “Father is responsible for determination, of sex of child and not the mother”., Justify., 6. What is linkage? How many linkage, groups do occur in human being?, 7. Write note on –PKU, 8. Compare - X-chromosome and Ychromosome., 9. Explain the chromosomal theory of, inheritance., 10. Observe the given pedigree chart and, answer the following questions., , Q. 5 Long answer type questions., 1. What is dihybrid cross? Explain with, suitable example and checker board, method., 2. Explain with suitable, independent assotrment., 3. Define test, significance., , example, , an, , cross and explain its, , 4. What is parthenogenesis?, the haplo-diploid method, determination in Honey bee., , Explain, of sex, , 5. In the answer for inheritance of X-linked, genes, Madhav had shown carrier male., His answer was marked incorrect., Madhav was wondering why his marks, were cut. Explain the reason., a. Identify whether the trait is sex, linked or autosomal., b. Give an example of a trait in human, beings which shows such a pattern, of inheritance., Q. 4 Match the column-I with column-II, and re-write the matching pairs., Column-I, , a. Turner’s syndrome, , 2. X-monosomy, , b. Klinefelter’s, syndrome, , 3. Holandric traits, , c. Down's syndrome, , 4. Feminized male, , d. Hypertrichosis, , 7. What is cris-cross inheritance? Explain, with suitable example., 8. Describe the, choromosomes., , different, , types, , of, , Project :, Study the genetic traits like Rolling of tongue, or Widow’s peak in your class and write your, own observations., , Column-II, , 1. 21 trisomy, , 6. With the help of neat labelled diagram,, describe the structure of chromosome., , 69
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4, , Molecular Basis of Inheritance, Can you recall?, , 1., 2., 3., 4., , What is nucleic acid?, What are the types of nucleic acid?, What are the functions of nucleic acid?, What is the difference between DNA in, prokaryotes and eukaryotes?, , 4.1 The Discovery of DNA:, Modern understanding of DNA has evolved, from the discovery of nucleic acid to the, development of the double-helix model. In 1869,, Friedrich Miescher began working with white, blood cells which are the major component of, pus from infections. He collected a lot of pus, from bandages at the local hospital. He used a, salt solution to wash the pus off the bandages., When he added a weak alkaline solution to the, cells, the cells lysed and nuclei precipitated, out of the solution. From the cell nuclei, he, isolated a unique chemical substance to, which he called nuclein. Chemically, nuclein, has high phosphorus content. Moreover it, showed acidic properties. Hence it was named, as nucleic acid., By the early 1900s, we knew that, Miescher's nuclein was a mix (mixture) of, proteins and nucleic acids. There are two kinds, of nucleic acids. DNA (deoxyribonucleic, acid) and RNA (ribonucleic acid)., 4.2 The Genetic Material is a DNA:, By the early 1900s, geneticist knew that, genes control the inheritance of traits, that, genes are located on chromosome and that, chemically chromosomes are mainly composed, of DNA and proteins. Initially, most geneticists, thought that protein are large, complex, molecules and store information needed to, govern cell metabolism. Hence it was assumed, that proteins caused the variations observed, within species., 70, , On the other hand DNA thought to be, small, simple molecule whose composition, varied little among species. Over the time,, these ideas about DNA were shown to be, wrong. In fact DNA molecules are large and, vary tremendously within and among species., Variations in the DNA molecules are different, than the variation in shape, electrical charge, and function shown by proteins so it is not, surprising that most researchers initially, favored proteins as the genetic material., Over a period of roughly 25 years (19281952), geneticists became convinced that DNA, and not protein, was the genetic material. Let, us study three important contributions that, helped cause this shift of opinion., Griffith’s experiments :, In 1928, a British medical officer Frederick, Griffith performed an experiment on bacterium, Streptococcus pneumoniae that causes, pneumonia in humans and other mammals., Griffith used two strains or two genetic varieties, of Streptococcus to find a cure for pneumonia,, which was a common cause of death at that, time. The two strains used were :, i. Virulent,, smooth,, pathogenic, and, encapsulated S type., ii. Non-virulent, rough, non-pathogenic and, non-capsulated R type., Griffith conducted four experiments on, these bacteria. First, when he injected bacteria, of strain R to mice, the mice survived because, it did not develop pneumonia. Second, when he, injected bacteria of strain S to mice, the mice, developed pneumonia and died. In the third, experiment, he injected heat-killed strain S, bacteria to mice, once again the mice survived., In fourth experiment, he mixed heat-killed, S bacteria with live bacteria of strain R and, injected to mice. The mice died and Griffith
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recovered large numbers of live strain S, bacteria from the blood of the dead mice., In these four experiments, something had, caused harmless strain R bacterium to change, into deadly S strain bacterium. Griffith showed, that the change was genetic. He suggested, that genetic material from heat-killed strain, S bacterium had somehow changed the living, strain R bacterium into strain S bacterium., Griffith concluded that the R-strain, bacterium must have taken up, to what he, called a "transforming principle" from the heatkilled S bacterium, which allowed R strain to, get transformed into smooth-coated bacterium, and become virulent., Rough strain, Smooth, (II-R), Strain (III-S), , Heat-killed, Smooth Strain, , Rough strain, and Heat-killed, Smooth Strain, , They also discovered that protein –digesting, enzymes (proteases), RNA-digesting enzyme, (RNAases) did not affect transformation, so the, transforming substance was neither a protein, nor RNA. DNA digested with DNAse did, inhibit the transformation, suggesting that DNA, caused the transformation. These experiments, proved that the transforming principle is DNA, but all biologists were not convinced., Rough nonvirulent, (strain R), + Protease, Mouse dead, + DNase, Heat-killed smooth, virulent (strain S), , Mouse alive, , Fig. 4.2 : DNA transforms bacteria, Finally, Alfred Hershey and Martha Chase, (1952) proved that DNA is the genetic material, and not proteins, by using bacteriophages., , Mouse alive, , Mouse dead, , Mouse alive, , Mouse dead, , Fig. 4.1 : Griffith’s experiment, Avery, McCarty and MacLeod’s experiment:, In 1944, after some 10 years of research, and experimentation, U. S. microbiologists, Oswald T. Avery, Colin M. MacLeod and, Maclyn McCarty (all at Rockefeller University, in New York) first evidenced to prove the DNA, is a genetic material (transforming principle),, through the experiments. They purified DNA,, RNA, Proteins (enzymes) and other materials, from cell free extract of S cells/ strain and mixed, with heat killed S strain and R cells seperately, to confirm which one could transform living, R cells into S cells. Only DNA was able, to transform harmless strain R into deadly, strain S., 71, , Hershey - Chase Experiment:, Hershey and Chase worked with viruses, that infect bacteria i.e. bacteriophages, which, are composed of DNA and protein. They used, radioactive phosphorous 32P in the medium for, some viruses and radioactive sulphur 35S for, some others., They grew some viruses on a medium that, contained radioactive phosphorus and some, others on medium that contained radioactive, sulphur. Viruses grown in the presence of, radioactive phosphorus contained radioactive, DNA (labelled DNA), but not radioactive, proteins because DNA contains phosphorus, (labelled DNA) but proteins do not. Similarly,, viruses grown on radioactive sulphur contained, radioactive protein but not radioactive DNA, because DNA does not contain sulphur., Radioactive phages were allowed, to, infect E.coli bacteria grown on the medium, containing normal ‘P’ and ‘S’. Then, as
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the infection proceeded, the viral coats, were removed with the help of centrifuge., Bacteria which were infected by viruses with, radioactive DNA, were radioactive, indicating, that DNA was the material that passed from, the viruses to the bacteria. Bacteria which were, infected by viruses having radioactive sulphur, (protein) were not radioactive. This indicates, that proteins from the viruses, did not enter, the bacteria. DNA is, therefore, the genetic, material that is passed from virus to bacteria, (fig. 4.3)., In other words, sometime after infection,, radioactivity for ‘P’ and ‘S’ was tested. Only, radioactive ‘P’ was found inside the bacterial, cell, indicating that DNA is the genetic material., Bacteriophage, Sulfur labeled, protein capsule, , Can you recall?, 1. What are the chemical components of, DNA?, 2. What is a chromosome?, 4.3 DNA packaging :, Length of DNA double helix molecule, in, a typical mammalian cell is approximately, 2.2 meters. (This can be worked out simply by, multiplying the total number of base pairs with, distance between the consecutive base pairs)., Approximate size of a typical nucleus is 10-6, m. How this long DNA molecule can be then, accommodated in such a small nucleus? It,, therefore, must be condensed, coiled and super, coiled to fit inside such small nucleus., Packaging in Prokaryotes:, In prokaryotes like E. coli, cell size is almost, 2-3 long. They do not have well organized, nucleus. It is without nuclear membrane and, nucleolus. The nucleoid is small, circular,, highly folded, naked ring of DNA which is, 1100 long in perimeter, containing about 4.6, million base pairs., , Phosphorus, labeled DNA, core, , 1. Infection, , 2. Blending, , The 1100 long (approximately 1.1 mm, if, cut and stretched out) nucleoid is to be fitted, or packaged into a cell which is hardly 2-3, long. Hence the negatively charged DNA, becomes circular, reducing the size to 350m, in diameter. This is further reduced to 30m, in diameter because of folding/ looping. 40-50, domains (loops) are formed. Formation of loops, is assisted by RNA connectors. Each domain is, further coiled and supercoiled, thereby reducing, the size down to 2 in diameter. This coiling, (packaging) is assisted by positively charged, HU (Histone like DNA binding proteins), proteins and enzymes like DNA gyrase and, DNA topoisomerase I, for maintaining super, coiled state., , 3. Centrifugation, , No sulfur detected in cells, +, Sulfur detected in, supernatant, , Phosphorus detected in cells, +, No phosphorus, detected in supernatant, , Fig. 4.3 : Hershey - Chase Experiment, , Do you know ?, 1. Multiple forms of DNA and their, differences., 2. Significance of different forms of DNA., , 72
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RNA cleaved, e. Partially unfolded, chromosome, 30 , , 350 , , 2, , RNA, , a. Circular, unfolded, chromosome, , Each loop is, independently, supercoiled, , b. Folded chromosome, actually 40 to 50 loops, , d., , c. Supercoiled,, folded, chromosome, , Nicked DNA, , Partial, DNase, digestion, Partial, RNase, digestion, , Partially uncoiled chromosome, , Fig. 4.4 : DNA Packaging in Prokaryotes, Packaging in Eukaryotes:, Eukaryotes show well organized nucleus, containing nuclear membrane, nucleolus, and thread-like material in the form of, chromosomes. In the chromosomes, DNA is, associated with histone and non-histone proteins, as was reported by R. Kornberg in 1974. The, organization of DNA is much more complex in, eukaryotes. Depending upon the abundance of, amino acid residues with charged side chains,, a protein acquires its charge. Histones are the, proteins that are rich in lysine and arginine, residues. Both these amino acid residues are, basic amino acids and carry positive charges, with them. So, histones are a set of positively, charged, basic proteins (histones + protamine)., These histones organize themselves to make a, unit of 8 molecules known as histone octamer., H2 A, , H2 B, , H4, , H3, , H1 Histone, , DNA, Octamer of Histones, , Fig. 4.5 : Nucleosome, , 73, , The negatively charged helical DNA, is wrapped around the positively charged, histone octamer, forming a structure known, as nucleosome. The nucleosome core is made, up of two molecules of each of four types of, histone proteins viz. H2A, H2B, H3and H 4. H 1, protein binds the DNA thread where it enters, (arrives) and leaves the nucleosome., One nucleosome approximately contains, 200 base pair long DNA helix wound around, it (fig. 4.5). About 146 base pair long segment, of DNA remains present in each nucleosome., Nucleosomes are the repeating units of, chromatin, which are thread-like, stained, (coloured) bodies present in nucleus. These look, like ‘beads-on-string’, when observed under, an electron microscope. DNA helix of 200 bps, wraps around the histone octamer by 1¾ turns., Six such nucleosomes get coiled and then form, solenoid that looks like coiled telephone wire., The chromatin is packed to form a solenoid, structure of 30 nm diameter (300A0) and further, supercoiling tends to form a looped structure, called chromatin fiber, which further coils, and condense at metaphase stage to form the, chromosomes. The packaging of chromatin at, higher levels, need additional set of proteins, that are called Non-Histone Chromosomal, proteins (NHC).
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Non-Histone Chromosomal Proteins, (NHC) : These are additional sets of proteins, that contribute to the packaging of chromatin, at a higher level., Heterochromatin and Euchromatin :, 1. Heterochromatin: In eukaryotic cells, some, segments of chromonema/ chromosome, during interphase and early prophase, remain in a condensed state. These region, constitute heterochromatin. This term, was proposed by Heitz. These regions are, localized near centromere, telomeres and, are also intercalated. It is genetically mostly, inactive. It stains strongly and appears, dark. Heterochromatin is 2 to 3 times more, rich in DNA than in the euchromatin., , Nucleosomes, , 0.5 m, , Fig. 4.6 : Chromatin showing beads-onstring, Nucleosome, Linker DNA, , 2. Euchromatin: The regions of chromonema, which are in non-condensed state, constitute, euchromatin. Euchromatic regions stain, light. Euchromatin is genetically very, much active and fast replicating., Euchromatin is transcriptionally active,, while heterochromatin is transcriptionally, almost inactive., , DNA wound around histone proteins, , A : Beads-on-string magnified, 111 Å, , Nucleosomes, , 60 Å, Chromatin fibers “stretched”, during preparation for electron, microscopy revealing linker, DNA between nucleosome cores, , Can you recall?, 1. What is the backbone of the DNA, structure?, 2. Name the nitrogen bases of DNA., 3. What are Nucleoside and Nucleotide?, 4. Is the double helix right or left handed?, , Linker DNA,, Nucleosome core,, varying in, 146 nucleotide pairs, length from 8 to of DNA wrapped as, 114 nucleotide, ¾ turns around an, pairs, octamer of histones, , B : Chain of nucleosomes forming, 10 to 11 nm thick fibre, , Find out, What is the key difference between, DNA in prokaryotic and eukaryotic cells?, 4.4 DNA Replication :, The DNA molecule regulates and controls, all the activities of the cell. Because of its, unique structure, it is able to control the, synthesis of other molecules of the cell. At, the same time when the cell reproduces, the, DNA also should duplicate itself to distribute, , 110 Å fiber, , 300Å, metaphase, fiber or, “solenoid”, , 110 Å, , C : Solenoid forming 30 nm thick fibre, Fig. 4.7 : DNA packaging, 74
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equally to the daughter cells. As a carrier of, genetic information, DNA has to perform two, important functions :, a. Heterocatalytic function : When DNA, directs the synthesis of chemical molecules, other than itself, then such functions of, DNA are called heterocatalytic functions., Eg. Synthesis of RNA (transcription),, synthesis of protein (Translation), etc., b. Autocatalytic function : When DNA, directs the synthesis of DNA itself, then, such function of DNA is called autocatalytic, function. Eg. Replication., The process by which DNA duplicates, itself is called replication. Through replication,, it forms two copies that are identical to it., In eukaryotic organisms, replication of, DNA takes place only once in the cell cycle., It occurs in the S- phase of interphase in the, cell cycle., DNA replicates through Semiconservative, mode of replication., The model for Semiconservative replication, was proposed by Watson and Crick, on the basis, of antiparallel and complementary nature of, DNA strands. The process of semicoservative, replication is as below:, , At the point ‘O’, enzyme endonuclease, nicks one of the strands of DNA, temporarily., The nick occurs in the sugar-phosphate back, bone or the phosphodiester bond., 3. Unwinding of DNA molecule:, Now enzyme DNA helicase operates by, breaking weak hydrogen bonds in the vicinity of, ‘O. The strands of DNA separate and unwind., This unwinding is bidirectional and continues, as ‘Y’ shaped replication fork. Each separated, strand acts as template., The two separated strands are prevented, from recoiling (rejoining) by SSBP (Single, strand binding proteins). SSB proteins remain, attached to both the separated strands so as, to facilate synthesis of new polynucleotide, strands., Replication, fork, , 75, , Okazaki, fragments, , RNA primer, , 5’, 3’, 3’, , 5’, , 5’, 3’, , 3’, 5’, , 1. Activation of Nucleotides:, The four types of nucleotides of DNA i.e., dAMP, dGMP, dCMP and dTMP are present, in the nucleoplasm. They are activated by ATP, in presence of an enzyme phosphorylase. This, results in the formation of deoxyribonucleotide, triphosphates i.e. dATP, dGTP, dCTP and dTTP., The process is known as Phosphorylation., 2. Point of Origin or Initiation point:, It begins at specific point ‘O’ -origin and, terminates at point ‘T’. Origin is flanked by, ‘T’ sites. The unit of DNA in which replication, occurs, is called replicon. In prokaryotes, there, is noly one replicon however in eukaryotes,, there are several replicons in tandem., , Lagging, template, , Leading, template, 3’, , 5’, , 3’, , 5’, A=T, T=A, , Parental strand, , C=G, A=T, G=C, Lagging, template, , T=A, 3’, , Leading, template, , 5’, RNA primer, 5’5’, 3’, , Okazaki fragments, New, strands, , 3’, 5’, , Fig. 4.8 : Semiconservative Replication of, DNA
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4. Replicating fork:, The point formed due to unwinding and, separation of two strands appear like a Y-shaped, fork, called replicating/ replication fork. The, unwinding of strands imposes strain which is, relieved by super-helix relaxing enzyme., 5. Synthesis of new strands:, Each separated strand acts as mould or, template for the synthesis of new complementary, strand. It begins with the help of a small RNA, molecule, called RNA primer. RNA primer get, associated with the 3’ end of template strand, and attracts complementary nucleotides from, surrounding nucleoplasm. These nucleotides, molecules bind to the complementary, nucleotides on the template strand by forming, hydrogen bonds (i.e. A=T or T=A; G = C or, C = G). The newly bound nucleotides get, interconnected by phosphodiester bonds,, forming a polynucleotide strand. The synthesis, of new complementary strand is catalyzed, by enzyme DNA polymerase. The new, complementary strand is always formed in 5’3’ direction., 6. Leading and Lagging strand:, The template strand with free 3’end is called, leading template and with free 5’ end is called, lagging template. The process of replication, always starts at C-3 end of template strand and, proceeds towards C-5 end. As both the strands, of the parental DNA are antiparallel, new, strands are always formed in 5’ → 3’ direction., One of the newly synthesized strand, develops continously towards replicating, fork is called leading strand. Another new, strand develop discontinuously away from the, replicating fork is called lagging strand., Maturation of Okazaki fragments :, DNA synthesis on lagging template takes, place in the form of small fragments, called, Okazaki fragments (named after scientist, , 76, , Okazaki). Okazaki fragments are joined by, enzyme DNA ligase., RNA primers are removed by DNA, polymerase and replaced by DNA sequence with, the help of DNA polymerase-I in prokaryotes, and DNA polymerase-α in eukaryotes., Finally, DNA gyrase (topoisomerase), enzyme forms double helix to form daughter, DNA molecules., 7. Formation of daughter DNA molecules:, At the end of the replication, two daughter, DNA molecules are formed. In each daughter, DNA, one strand is parental and the other, one is totally newly synthesized. Thus, 50%, is contributed by mother DNA. Hence, it is, described as semiconservative replication., Experimental confirmation :, Semiconservative Replication : In newly, formed DNA molecule, one strand is old, (i.e. conserved) and other strand is newly, synthesized. Thus, it is called Semiconservative, mode of replication., It is experimentally proved by Matthew, Meselson and Franklin Stahl (1958) by, using equilibrium - density - gradient centrifugation technique., 1. Meselson and Stahl in 1958 performed, an experiment to prove semiconservative, nature (mode) of replication., 2. They cultured bacteria E.coli in the medium, containing 14N (light nitrogen) and obtained, equilibrium density gradient band by using, 6M CsCl2. The position of this band is, recorded., E. coli cells were then tranferred to 15N, medium (heavy isotopic nitrogen) and, allowed to replicate for several generations., At equilibrium point density gradient band, was obtained, by using 6M CsCl2. The, position of this band is recorded.
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Generation I, 15, , 15, , 14, , N-DNA, , Generation II, , N-DNA, , 14, , N-DNA, , N-DNA, 14, , 40 min, , 20 min, , 14, , N15N-DNA, , N15N-DNA, , 14, , 15, , N 15 N, Heavy, , 14, , N 15 N, Hybrid, , 14, , N 14 N, Light, , N-DNA, , 14, , N 15 N, Hybrid, , Fig. 4.9 : Interpretation of results of Meselson’s experiment on the separation of DNA by, equilibrium density gradient centrifugation, 4. The heavy DNA (15N) molecule can, be distinguished from normal DNA by, centrifugation in a 6M Cesium chloride, (CsCl2) density gradient. The density, gradient value of 6M CsCl2 and 15N DNA is, almost same. Therefore, at the equilibrium, point 15N DNA will form a band. In this, both the strands of DNA are labelled with, 15, N., 5. Such E. coli cells were they transferred to, another medium containing 14N i.e. normal, (light) nitrogen. After first generation,, the density gradient band for 14N 15N was, obtained and its position was recorded., After second generation, two density, gradient bands were obtained - one at 14N, 15, N position and other at 14N position., 6. The position of bands after two generations, clearly proved that DNA replication is, Semiconservative., Use your brain power, , 4.5 Protein synthesis :, Proteins are very important biomolecules., They serve as structural components, enzymes, and hormones. The cell needs to synsthesize, new protein molecules. The process of, protein synthesis includes transcription and, translation. The process of copying of genetic, information from one (template) strand of DNA, into a single stranded RNA transcript, is termed, as transcription. During this process, synthesis, of complementary strand of RNA takes place, (Except that the Adenine nitrogen base pairs, with the Uracil base instead of Thymine)., Central Dogma :, Double stranded DNA molecule gives, rise to mRNA which acts as a messenger to, programme the synthesis of a polypeptide, chain (protein). This type of unidirectional, flow of information from DNA to RNA to, protein/ proteins is referred as central dogma, of molecular biology. It was postulated by, F.H.C. Crick in 1958., Transcription, , 1. List as many different enzyme activities, required during DNA synthesis as you, can., 2. This type of replication is called semiconservative replication. Considering, the meaning of these words, why DNA, replication is called semiconservative, replication?, , DNA, , Translation, , mRNA, , Polypeptide, , The present concept of central dogma in, retroviruses or riboviruses is given by Temin, (1970) and Baltimore (1970):, Transcription, Translation, DNA, mRNA, Polypeptide, Reverse Transcription, , 77
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Accordingly enzyme RNA dependent DNA, polymerase, synthesizes DNA from RNA., Can you recall?, 1. What is transcription?, 2. How many nucleotides are present in a, codon?, 3. Name the molecule which carries, anticodon?, 4. What is mutation?, A. Transcription:, During transcription, information of only, one strand of DNA is copied into RNA. This, strand of DNA acts as template. Enzyme RNA, polymerase catalyses the formation of RNA, transcript., DNA is located in the nucleoid of, Prokaryotes and in nucleus of Eukaryotes., DNA transcription takes place in nucleus, in eukaryotes whereas translation occurs, in cytoplasm. DNA transfers information, to m-RNA which then moves to ribosomes., Transcription occurs in the nucleus during, G1 and G2 phases of cell cycle. DNA has, promotor and terminator sites. Transcription, starts at promotor site and stops at terminator, site. Actually the process of transcription, in, both Prokaryotes and Eukaryotes, involves, three stages viz. Initiation, Elongation and, Termination., Transcription Unit:, Each transcribed segment of DNA is called, transcription unit. It consists of i. Promotor,, ii. The structural gene, iii. A terminator. Two, strands of DNA in the structural gene show, following features :, i. The promotor is located towards 5’ end of, structural gene i.e. upstream. It is a DNA, sequence that provides binding site for, enzyme RNA polymerase. RNA polymerase, binds to specific Promotor. In prokaryotes,, the enzyme recognizes the promotor by its, sigma factor sub unit., ii. Structureal genes - two strands of DNA have, opposite polarity. DNA dependent RNA, 78, , polymerase catalyses polymerisation in, 5’→3’ direction. So the DNA strand having, 3’→5’ polarity acts as template strand. The, other strand of DNA having 5’→3’ polarity, is complementary to template strand. The, sequence of bases in this strand, is same, as in RNA (where Thymine is replaced by, Uracil). It is the actual coding strand. The, information on this strand of DNA is copied, on mRNA. This is called sense strand., iii. The terminator is located at 3’ end of coding, strand i.e. downstream. It defines the end of, the transcription process., Template strand, , 3’, , 5’, , Structural gene, , 5’, Promoter, , Coding strand, , 3’, Terminator, , Fig. 4.10 : Transcription unit, After binding to promoter, RNA polymerase, moves along the DNA and causes local, unwinding of DNA duplex into two chains in, the region of the gene. Exposed ATCG bases, project into nucleoplasm. Only one strand, functions as template (antisense strand) and, the other strand is complementary which is, actiually a coding strand (sense strand). The, ribonucleoside tri phosphates join to bases of, DNA template chain. As transcription proceeds,, the hybrid DNA-RNA molecule dissociates and, makes mRNA molecule free., A, G, U, C, A, G, U, A, C, A, U, G, m-RNA, , 5, , 3, , 3, , T, C, A, G, T, C, A, T, G, T, A, C, 5, Template strand, of DNA, (antisense strand), , 5, A, G, T, C, A, G, T, A, C, A, T, 3, G, Coding strand, of DNA, (sense strand), , Fig. 4.11 : Formation of Template and, Coding strand of DNA
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When RNA polymerase reaches the, terminator signal on the DNA, it leaves DNA, and fully formed mRNA (primary transcript) is, released., As the mRNA grows, the transcribed region, of DNA molecule becomes spirally coiled and, attains (regains) double helical form., In bacteria, m-RNA does not require, any processing because it has no introns., Prokaryotes posses only one type of RNA, polymerase. In eukaryotes, there are three, types RNA polymerases. RNA polymerase-I, transcribes r-RNA. RNA polymerase-II, transcribes m-RNA (primary transcript) and, heterogeneous nuclear RNA (or hnRNA). RNA, polymerase-III is responsible for transcription, of t-RNA and small nuclear RNA (snRNA)., Do you know ?, 1. Many viruses contain RNA as genetic, material and replicate by synthesizing, first the DNA and then form RNA. This, process is called reverse transcription., Such viruses are known as Retroviruses., 2. e.g. Human immuno deficiency virus, (HIV) is responsible for causing AIDS., 3. In some cases like E.coli, a chain, terminating protein, the rho factor stops, the synthesis of mRNA., , Transcription unit and the gene:, The DNA sequence coding for m-RNA/ tRNA or r- RNA is defined as a gene. Cistron is, a segment of DNA coding for a polypeptide. A, single structural gene in transcription unit is, said to be monocistronic where as a long, segment of DNA having set of various structural, genes in one transcription unit is referred as, polycistronic. Structral genes in eukaryotes, have interrupted non-coding sequences, (introns). The coding sequences or expresssequences are defined are exons. Only exons, appear in procesed mRNA in Eukaryotes., Processing of hnRNA:, In eukaryotes, forms of RNA transcribed, from DNA are called primary transcripts., Such transcripts undergo changes called, processing or maturation before becoming, functional. Primary transcript is non functional, and contains both exons and introns. During, processing only introns are removed by the, process called splicing., 5’, 3’, , 5’, 3’, , 3’ mRNA, Intron, Cap, Polyadenylation, m, GPPP Exon, RNA splicing, 5’, m, 3’, GPPP, 5’, Poly A tail, , Capping, , m, , GPPP, 5’, , 4. The process of transcription as well as, translation involves 3 stages - initiation,, elongation and termination., , m, , GPPP, 5’, Messenger RNA (mRNA), , 3’, , Fig. 4.12 : Transcription and Processing of, hnRNA to mRNA in Eukaryotes, Always Remember, Types of RNA and process of transcription:, In bacteria, there are three types of RNAs : m- RNA provides the encoded message, t- RNA, brings specific amino acid, to the site of translation. r- RNA plays role in providing binding site, to mRNA., There is single DNA dependent RNA polymerase that catalyses transcription of all 3 types, of RNA in bacteria. RNA polymerase binds to promotor and initiates transcription (initiation)., 79
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Exons are joined in a definite sequence, (order) by DNA ligase enzyme. Heterogeneous, nuclear RNA, undergoes the process of capping, and tailing. In capping, methylated guanosine, tri phosphate is added to 5’ end of hnRNA. In, tailing, polyadenylation take place at 3’end., It is the fully processed hnRNA, now called mRNA. For translation m-RNA is transported, out of the nucleus through nuclear pore., Genetic Code:, It is already known that DNA is a master, molecule of a cell that initiates, guides, regulates, and controls the process of protein synthesis., To perform this complicated function, it must, carry the requisite information for the synthesis, of proteins. Obviously this information has to, be verily located in the DNA itself. The site for, storing this information lies in the sequence of, nucleotides (i.e. nitrogen bases), as evidenced, by Yanofski and Sarabhai (1964)., About, 20 different types of amino acids are, involved in the process of synthesis of proteins., DNA molecule has 4 types of nitrogen bases to, identify these 20 different types of amino acids., Question arises then, how is it possible that 20, types of amino acids are encoded by 4 types of, nitrogen bases?, According to F.H.C., Crick, this, information is stored in the form of coded, language (cryptogram) called genetic code,, that contains code words (codons) each one, specifying (representing) specific amino acid., Genetic code, therefore, is a collection of base, sequences that correspond to each amino acid., A single nitrogen base in a codon (singlet, codon) will encode for only four different types, of amino acids. A combination of two nitrogen, bases (doublet codon) will specify only 16, different types of amino acids. A combination, of three nitrogen bases (triplet codon) will, specify 64 different types of amino acids. Hence, G. Gamov (1954) suggested that in a codon,, 80, , there must be combination of three consecutive, nitrogen bases that will be sufficient to specify, 20 different types of amino acids., Thus, there would be 64 different codons, (code words) in the dictionary of genetic code, and that each code word has to be a triplet, codon. Every three consecutive nucleotides in, DNA will constitute a triplet codon. Genetic, code is a triplet code, was evidenced first by, Crick (1961) using “frame- shift mutation”., However, M. Nirenberg and Matthaei were, able to synthesize artificial m-RNA which, contained only one type nitrogenous base, i.e. Uracil (Homopolymer). This synthetic, poly-U sequence was transferred to protein, synthesizing enzymes. A small polypeptide, molecule was produced/ formed by the linking, of phenylalanine molecules. This explains that, UUU codes for phenyl alanine. Later different, homopolymer codons were deciphered. Codons, formed by two or more bases were also tried., Dr. Har Gobind Khorana : He devised a, technique for artificially synthesizing m- RNA, with repeated sequences of known nucleotides., By using synthetic DNA, Dr. Khorana prepared, chains of polyribonucleotides with known, repeated sequences of two or three nucleotides., eg. CUC UCU CUC UCU., This resulted in formation of polypeptide, chain having two different amino acids placed, alternately (Leucine and Serine). Similarly, polynucleotide chain with three- nitrogen, base repeats gave polypeptide chain with only, one amino acids. Eg. CUA CUA CUA CUA, (leucine). Later, Severo Ochoa established that, the enzyme (polynucleotide phosphorylase), was also helpful in polymerising RNA with, defined sequences in a template- independent, manner (i.e. enzymatic synthesis of RNA)., Finally Nirenberg, Matthaei and Ochoa, deciphered all the 64 codons in the dictionary, of genetic code.
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iv., , v., , vi., , vii., , viii., , ix., x., , •, , Genetic code is commaless : There is, no gap or punctuation mark between, successive/ consecutive codons., Genetic code has degeneracy : Usually, single amino acid is encoded by single, codon. However, some amino acids are, encoded by more than one codons. e.g., Cysteine has two codons, while isoleucin, has three codons. This is called degeneracy, of the code. Degeneracy of the code is, explained by Wobble hypothesis. Here,, the first two bases in different codons are, identical but the third one, varies., Genetic code is universal : By and, large in all living organisms the specific, codon specifies same amino acid. e.g., codon AUG always specifies amino acid, methionine in all organisms from bacteria, up to humans., Genetic code is non-ambiguous : Specific, amino acid is encoded by a particular, codon. Alternatively, two different amino, acids will never be encoded by the same, codon., Initiation codon and termination codon:, AUG is always an initiation codon in any, and every mRNA. AUG codes for amino, acid methionine. Out of 64 codons, three, codons viz. UAA, UAG and UGA are, termination codons which terminate/ stop, the process of elongation of polypeptide, chain, as they do not code for any amino, acid., Universal : Usually in all organisms the, specific codon specifies same amino acid., , Activity :, 5, , 3, AUGUCGACGCCCUAA, , m-RNA, Consider given m-RNA strand which, has undergone mutation and lost nucleotides, A, C, and G sequentially. Resultant mRNA, is represented by 1, 2 and 3. With the help of, checker board of amino acids, explain the, changes in amino acid sequence that will, occur due to such mutation., 5, , 3, , 1., AUGUCGCGCCCUAA, , 5, , 2., , 3, A UG U C G G C C C UA, , 5, , A, , 3, , 3., AUGUCGCCCUAA, , Codon and anticodon : Codon is a part, of DNA e.g. AUG is codon. It is always, represented as 5’ AUG 3’. Anticodon is a, part of tRNA. It is always represented as, 3’UAC 5’., , Mutations and Genetic Code:, Mutation is a phenomenon in which, sudden change in the DNA sequence takes, place. It results in the change of genotype, (i.e. character). Along with recombination,, mutation is raw material for evolution as it, also results in variations. During mutation,, possibility of loss (deletion) or gain (insertion/, duplication) of a segment of DNA results in, alteration in the chromosome. Mutation can, also occur due to change in a single base pair, of DNA. This is known as point mutation. Eg., Sickle cell anaemia (Refer to earlier chapter)., Deletion or insertion of base pairs of DNA, causes frame – shift mutations or deletion, mutation. Insertion or deletion of one or two, bases changes the reading frame from the point, of insertion or deletion. Insertion or deletion, of three or multiples of three bases (insert or, delete) results in insertion or deletion of amino, acids and reading frame remains unaltered, from that point onwards., , It is possible to predict sequence of codon, on mRNA by studying the sequence of, amino acids in a polypeptide chain., , t-RNA- the adapter molecule:, Scientists considered that there has to, be a mechanism in which t-RNA will read the, 82
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codon and also simultaniously binds with the, amino acid as amino acid does not have any, special capacity to read the codon. So t-RNA is, considered as an adapter molecule. This role of, tRNA was understood much later., Glutamic acid, , 3’, , Amino acid, attachment site, , Process of translation requires amino, acids, mRNA, tRNA, ribosomes, ATP, Mg++, ions, enzymes, elongation, translocation and, release factors., , 5’, , tRNA 5’, , B. Translation - protein synthesis :, Translation is the mechanism in which, codons of mRNA are translated and specific, amino acids in a sequence form a polypeptide on, ribosomes. All types of proteins are synthesised, by the cell, within itself (i.e. intracellularly)., , 3’, , i., , Anticodon, loop, , Intramolecular, base pairing, C U C Anticodon, , GUCCAGGAGCUAUAG, mRNA, , Fig. 4.14: t-RNA - the adapter molecule, Cloverleaf structure (2 dimentional) of tRNA possess an anticodon loop that has bases, complementary to the codon. It is called, anticodon. It shows amino acid acceptor end, (3’ end) having unpaired CCA bases (i.e. amino, acid binding site) to which amino acid binds., For every amino acid, there is specific t- RNA., Initiator t-RNA is specific for methionine., There are no t-RNA’s for stop codons. In the, actual structure, the t-RNA molecule looks like, inverted L (3 dimentional structure)., Can you tell?, Why t-RNA is called as adapter, molecule?, , Amino acids form raw material for, protein synthesis. About 20 different, types of amino acids are known to form, proteins. These are available in the, cytoplasm., ii. DNA controls synthesis of proteins having, amino acids in specific sequence. This, control is possible through transcription, of m-RNA. Genetic code is specific for, particular amino acid., iii. RNAs serve as intermediate molecules, between DNA and protein., iv. Ribosomes serve as site for protein, synthesis. Each ribosome consists of large, and small subunits. These subunits occur, separately in cytoplasm. Only during, protein synthesis, these two subunits get, associated together due to Mg++ ions., A ribosome has one binding site for m-RNA, and 3 binding sites for t-RNA. They are P, site (peptidy t-RNA site), A site (aminoacyl, – t-RNA site) and E site (exit site). Only first, t- RNA- amino acid complex, directly enters P, site of ribosome., In Eukaryotes, a groove is present between, two subunits of ribosomes. It protects the, Polypeptide chain from the action of cellular, enzymes and also protects mRNA from the, action of nucleases., , Can you recall?, 1. Name different types of RNAs., 2. Name the site of protein synthesis., 3. Which molecule carries information of, protein synthesis from gene?, 4. Which molecule carries amino acid from, cytoplasm to ribosome?, , Mechanism of translation (i.e. synthesis of, polypeptide chain) :, It involves three steps :, i. Initiation, ii. Elongation, iii. Termination, 83
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1. Initiation of Polypeptide chain :, a. Activation of amino acids is essential, before translation initiates for which, ATP is essential. Small subunit of, ribosome binds (attaches) to the m-RNA, at 5’ end. Initiator codon, AUG is present, on m-RNA which initiates the process of, protein synthesis (translation). Initiator, t- RNA binds with initiation codon, (AUG) by its anticodon (UAC) through, hydrogen bonds. It carries activated, amino acid methionine (in Eukaryotes), or formyl methionine (in prokaryotes)., b. Now the large subunit of ribosome joins, with the smaller subunit, that requires, Mg++ ions., c. Initiator charged t-RNA (with activated, amino acid methionine) occupies the Psite of ribosome and A- site is vacant., 2. Elongations of polypeptide chain :, During this process, activated amino acids, are added one by one to first amino acid, (methionine). Amino acid is activated by, utilising energy form ATP molecule. This, amino acid binds with amino acid binding, site of t-RNA- This results in formation of, t-RNA- amino acid complex., Addition of Amino acid occurs in 3 Step, cycle a. Condon recognition- Amino acyl t- RNA, molecule enters the ribosome at A-site., Anticodon binds with the codon by, hydrogen bonds., b. Amino acid on the first initiator t-RNA, at P-site and amino acid on t-RNA at Asite join by peptide bond. Here enzyme, Ribozyme acts as a catalyst. At this time, first tRNA at ‘P’ site is kicked off., c. Translocation- The t- RNA at A-site, carrying a dipeptide at A-site moves, to the P-site. This process is called, translocation. In translocation, both, the subunits of ribosome move along in, relation to tRNA and mRNA. Hence,, 84, , tRNA carrying dipeptide now gets, positioned at ‘P’ site of ribosome, making, ‘A’ site vacant. At this site, then next, charged tRNA molecule carrying amino, acid will be received. During this process,, first uncharged tRNA is discharged from, E-site., This process is repeated as amino acids, are added to Polypeptide. It takes less than 0.1, second for formation of peptide bond., Third charged t-RNA with its amino acid,, arrives at A-site of ribosome. Anticodon and, codon bind by hydrogen bond. Polypeptide, bond is formed. Second t-RNA is discharged, from P-site to E-site and leaves the ribosome., So the events like arrival of t-RNA- amino acid, complex, formation of peptide bond, ribosomal, translocation and removal of previous tRNA,, are repeated. As ribosome move over the mRNA, all the codons on mRNA are exposed, one by one for translation., Larger sub unit of, ribosome, Initiator tRNA, , mRNA, , a., , Smaller sub unit, of ribosome, , E site, A site, P site, , Peptide, link, , b., Polypeptide, chain, , E site, A site, , A site, Last, tRNA, , c., Released mRNA, , Fig. 4.15 : Translation Protein synthesis, a. Initiation, b. Elongation, c. Termination
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3. Termination and release of polypeptide:, At the end of m-RNA, there is a stop codon, (UAA/ UAG/ UGA). It is exposed at the Asite. It is not read and joined by anticodon of, any t-RNA. The release factor binds to the, stop codon, thereby terminating the translation, process. The Polypeptide is now released in the, cytoplasm., Two subunits of Ribosome dissociate and, last tRNA is set free in the cytoplasm., m-RNA also has some additional sequences, that are not translated and are referred as, untranslated regions (UTR). The UTRs are, present at both 5’-end (before start codon) and, at 3’-end (after stop codon). They are required, for efficient translation process., Finally mRNA is also released in the, cytoplasm. It gets denatured by nucleases, immidiately. Hence mRNA is short -lived., Can you tell?, 1. Enlist different steps of protein synthesis., 2. Name the initiator codon of protein, synthesis., 3. Explain in brief the process of initiation, during protein synthesis., 4. Name three binding sites of ribosome., 5. What is translocation?, 4.6 Regulation of gene expression:, It is the multistep process by which a gene, is regulated and its product is synthesized., Thus, gene expression results in the formation, of a Polypeptide. Gene expression process is, regulated at different levels., In eukaryotes, the regulation can be at, different levels like1. Transcriptional level (formation of, primary transcript), 2. Processing level ( regulation of splicing), 3. Transport of m-RNA from nucleus to the, cytoplasm., 4. Translational level., 85, , Genes of a cell are expressed to perform, different functions. For eg. An enzyme beta, galactosidase is synthesised by E-coli. It is, used for hydrolysis of lactose into galactose, and glucose., Lactose, , ( – galactosidase), +H2O, , Galactose + Glucose., , If E.coli bacteria do not have lactose, in the surrounding medium as a source of, energy, then enzyme -galactosidase is, not synthesised. So, it is the metabolic or, physiological or environmental conditions that, regulate expression of genes. The development, and differentiation of embryo into an adult, organism, is also a result of the coordinated, regulation or expression, of several sets of, genes., Now one has to understand and know the, mechanism by which the organisms regulate, gene expression in response to changes in the, environment. If so, whether single mechanism, exists for regulation of the expression of, different genes/ sets of genes or different genes, are regulated by different mechanisms., Certain bacteria like E.coli adapt to their, chemical environment by synthesizing certain, enzymes depending upon the substrate present., Such adaptive enzyme is called inducible, enzymes. A set of genes will be switched on, when there is necessity to metabolise a new, substrate. This phenomenon is called induction, and small molecule responsible for this, is, known as inducer. It is positive control., Do you know ?, Repressible regulation of gene is, seen when the end product of a biosynthetic, pathway like amino acid, is provided in the, medium. At this time, internal biosynthesis, of amino acid stops. It is negative control so, the metabolite (amino acid) turns off a set of, genes involved in producing that metabolite., This is called feedback repression.
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4.7 Operon concept :, It is a transcriptional control mechanism, of gene regulation. Francois Jacob and Jacques, Monod (1961) explained that metabolic, pathways are regulated as a unit., For example in E.coli, when lactose sugar, is provided to the culture medium, cell induces, production of three enzymes necessary for, digestion of lactose. The enzymes are :, i., , -galactosidase : Digests lactose into, galactose and glucose., , ii., , -galactoside permease : Permits, lactose molecules to enter into the cell., , iii. Transacetylase, (-Galactoside, acetyltransferease) : Transfers an, acetyl group from acetyl CO-A to, galactoside., Synthesis of these three enzymes, is, controlled by a long segment of DNA known, as Operon. It consists of an operator site O and, three structural genes Z, Y and A .The action, of structural genes is regulated by operator, site with the help of a repressor protein., Repressor protein is produced by the action of, gene i (inhibitor) known as regulator gene., The gene expression depends on whether, operator is switched on or switched off., If the operator is switched on, the three genes, z, y and a are transcribed by RNA Polymerase, into a single m-RNA. Each structural gene is, generally known as cistron and the transcribed, long m-RNA covering various cistrons is, known as Polycistronic., Switching on or switching off of the, operator is achieved (acomplished) by a protein, called repressor. When this protein is attached, to the operator and blocks it, the switch is turned, off and structural genes are not expressed., Lac operon :, Lactose or lac operon of E.coli is inducible, operon. Theoperonisswitchedonwhenachemical, inducer- lactose is present in the medium., 86, , Lac operon consists of following, components :, 1. Regulator gene (repressor gene), 2. Promoter gene, 3. Operator gene, 4. Structural genes, 5. Inducer - It is not a component of, operon., 1. Regulator gene : This gene controls the, operator gene in cooperation with an, inducer present in the cytoplasm. Regulator, gene preceeds the promoter gene. It may not, be present immidiately adjacent to operator, gene. Regulator gene produces a protein, called repressor protein. Repressor binds, with operator gene and represses (stops) its, action. It is called regulator protein., 2. Promoter gene : This gene preceeds the, operator gene. It is present adjacent to, operator gene. The promoter gene marks, the site at which the RNA Polymerase, enzyme binds. When the operator gene, is turned on, the enzyme moves over, the operator gene and transcription of, structural genes starts. Promoter gene base, sequence determines which strand of DNA, acts a template., 3. Operator gene : It preceeds the structural, genes. This controls the functioning of, structural genes. It lies adjacent to the, Structural genes. When operator gene is, turned on by an inducer, the Structural, genes produce m-RNA. Operator gene is, turned off by a product of repressor gene., 4. Structural gene : When lactose is added, to the E.coli culture, the structural genes, catalyse (produce) m-RNA which in turn, produces polypeptides, on the ribosomes., The polypeptides formed, act as enzymes, to caltalyse lactose in the cell. There are, 3 structural genes in the sequence lac-Z,, lac-Y and lac-A. Enzymes produced are, -galactosidase, -galactoside permease, and transacetylase respectively.
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lac operon, Regulatory gene, 3’, , RNA polymerase, Promoter, , Operator blocked, 1, 2, 3, , Repressor, mRNA, 3’, Movement, blocked, , Transcription, (a), 5’, Inducer absent Translation, Repressor, Regulatory gene, 3’, Transcription, 5’, Translation, , Transcription, proceeds, 2, , 3, 5’, , Repressor, mRNA, 3’, , Template, DNA strand, , Structural genes, no synthesis of mRNA, in active, , Operator 1, , Promoter, , 5’, , Template, DNA strand, , Transcription, mRNA, Translation, , 5’, , Proteins (enzymes to metabolize lactose), (b), Inducer present, , Repressor, , Inactivated, repressor, Inducer (allolactose), , Fig. 4.16 : Working of Lac Operon, 5. Inducer : It is a chemical in the cytoplasm, (allolactose) which inactivates the, repressor. When lac operon is switched on,, then inducer joins with repressor protein, preventing the binding of repressor to the, operator gene. So the Operator gene is free, and now enzyme RNA polymerase can, move from promoter to structural genes via, operator gene., Role of lactose :, A few molecules of lactose enter into the, cell by an enzyme permease.A small amount, of this enzyme is present even when operon is, switched off. A few molecules of lactose, act as, inducer and bind to repressor. This repressor –, inducer complex fails to join with the operator, gene, which is then turned on. Structural genes, produce all enzymes. Thus, lactose acts as, an inducer of its own break down. When the, inducer level falls, the operator is blocked again, by repressor. So structural genes are repressed/, inactivated again. This is negative feedback., Use your brain power, If operator gene is deleted due to, mutation, how will E.coli metabolise lactose?, 87, , Can you tell?, 1. What is the role of a repressor gene?, 2. Name the different structural genes in, sequence of lac operon., 3. Which molecule does act as inducer, molecule in lac operon?, 4. In which condition, lac operon is, switched off?, Internet my friend, Find out information about Trp-operon, Araoperon, His-operon, Val-operon., 4.8 Genomics:, The term Genome (introduced by H.Winkler, in 1920) is the total genetic constitution of an, organism. Alternatively, it is a complete copy, of genetic information (DNA) or one complete, set of chromosomes (monoploid or haploid) of, an organism., The term Genomics (term coined by T.H., Roderick in 1986) is the study of genomes, through analysis, sequencing and mapping of, genes along with the study of their functions.
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The sequencing of yeast, Drosophila and, mouse genome was done in order to facilitate, comparative studies between humans and other, organisms commonly used for genetic studies,, in laboratory. Several additional genomes are, now either actively being sequenced or strongly, considered for sequencing. These include, several microbes, bee, tomato and other crops., Genomics study may be classified into two, types:, a. Structural genomics: It involves mapping,, sequencing and analysis of genome., b. Functional genomics: It deals with the, study of functions of all gene sequences, and their expression in organisms., Application of genomics:, Structural and functional genomics is used, for different purposes in the improvement of, crop plant, human health and livestock. The, knowledge and understanding acquired from, genomics research can be applied in a number, of different sectors, including medicine,, biotechnology and social sciences. It helps in, the treatment of genetic disorders through gene, therapy., • Genomics is used in agriculture to develop, transgenic crops having more desirable, characters., • Genetic markers developed in genomics,, have applications in forensic analysis., • Genomics can lead to introduce new gene in, microbes to produce enzymes, therapeutic, proteins and even biofuels., 4.9 Human Genome Project :, The human genome project was initiated, in 1990 under the International administration, of the Human Genome Organization (HUGO)., This project was co-ordinated by the US, department of Energy and National institute, of health., international partners in the United Kingdom,, France, Germany, Japan, India and China. The, 88, , Human Genome Project formally began in, 1990 and was completed in 2003.The human, genome project is a multinational research, project to determine the genomic structure of, humans. The main aims of project are –, I. Mapping the entire human genome at the, level of nucleotide sequences., II. To store the information collected from the, project in databases., III. To develop tools and techniques for analysis, of the data., IV. Transfer of the related technologies to the, private sectors, such as industries., V. Taking care of the legal, ethical and social, issues which may arise from project., HGP (Human Genome Project) was closely, associated with rapid development of a new, area in biology, called Bioinformatics. The, work of human genome project has allowed, researchers to begin to understand the blueprint, in building and constructing the human genome., As researchers learn more about the functions, of genes and proteins, this knowledge will have, a major impact in the fields like Medicine,, Biotechnology and the Life sciences. Therefore, HGP is very important., Human Genome Project was to provide a, complete and accurate sequence of the 3 billion, DNA base pairs that make up the human, genome and to find out the estimated number, of human genes. Now about 33000 genes have, been estimated to be present in humans., The project was also aimed to sequence, the genomes of several other organisms such, as bacteia e.g. E.coli, Caenorhabditis elegans, (a free living non-pathogenic nematode),, Saccharomyces cerevisiae (yeast), Drosophila, (fruit fly), plants (rice and Arabidopsis), Mus, musculus (mouse), etc. Complete genome, sequences of these model organisms will be, useful for comparative studies that will allow, researchers to study gene functions in these, organisms.
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Table 4.17 : Comparative genome sizes of humans and other models organisms., Organism, Human (Homo sapiens), Mouse (Mus musculus), Fruit fly (Drosophila melanogaster), Plant (Arabidopsis thaliana), Roundworm (Caenorhabditis elegans), Yeast (Saccharomyces cerevisiae), Bacteria (Escherichia coli), , Chromosome Estimated gene Estimated size, number, number, (base pairs), 46, 33,000, 3 billion, 40, 25,000, 2.9 billion, 8, 13,000, 165 million, 10, 25,000, 157 million, 12, 19,000, 97 million, 32, 6000, 12 million, 4400, 4.6 million, 1*, , The secret of our complexity may lie not, in the number of our genes but how we use, them. It will lead to the understanding of gene, structure and function in other species. Since, we possess many of the genes same as these, of flies, round worms and mice, such studies, will lead to a greater understanding of human, evolution., Use your brain power, 1. What have we learnt from the Human, Genome Project?, 2. Why is HGP important?, Can you tell?, Do different organisms have the same DNA?, 4.10 DNA Fingerprinting:, Genes present on chromosomes are, responsible for determining characters of, the organism as well as for inheritance of, characters. Due to recombination of paternal, and maternal genes, we differ from our parents., Differences also arise due to infrequent, mutations that occur during gamete formation, (cell division). Due to all these factors, every, individual has its unique genetic make-up,, which may be called its Fingerprint. The, technique developed to identify a person with, the help of DNA restriction analysis, is known, as DNA profiling or DNA fingerprinting. The, technique of finger printing was first given by, British geneticist, Dr. Alec Jeffreys in 1984., 89, , DNA fingerprinting technique is based on, identification of nucleotide sequence present, in this wonder molecule. About 99.9% of, nucleotide sequence in all persons, is same., Only some short sequences of nucleotides, differ from person to person. In the population,, every person shows unusual sequences of 20100 base pairs, which are repeated several, times. They are termed as Variable Number of, Tandem Repeats (VNTRs)., The length of the regions having VNTRs, is different in each individual and hence is the, key factor in DNA profiling. Steps involved in, DNA finger printing are as follows:, 1. Isolation of DNA: The DNA must be, recovered from the cells or tissues of the, body (host). Only small amount of tissue, like blood, hair roots, skin, etc. is required., 2. Restriction digestion: The isolated DNA, is treated with restriction enzymes. The, restriction enzymes cut the DNA into, small fragments having variable lengths., This phenomenon is called Restriction, Fragment Length Polymorphism (RFLP)., 3. Gel electrophoresis: The DNA samples, are loaded for agarose gel electrophoresis, under an electric influence. The DNA, fragments, which are negatively charged, move to the positive pole. The movement, of these fragments depends on length of, the fragments. This results in formation of, bands. dsDNA splits into ssDNA by alkali, treatment.
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4. Southern blotting: The separated DNA, fragments are transferred to a nylon, membrane or a nitrocellulose filter paper, by placing it over the gel and soaking them, with filter paper overnight., , the nitrocellulose filter paper. Remaining, single stranded DNA probe fragments are, washed off., 7. Photography: The nitrocellulose filter, paper is photographed on an X-ray film by, autoradiography. The film is analysed to, determine the presence of hybrid DNA., , 5. Selection of DNA probe: A known sequence, of single- stranded DNA is prepared. It is, called DNA Probe. DNA Probe is obtained, from organisms or prepared by cDNA, preparation method. The DNA probe is, labelled with radioactive isotopes., , Application of DNA fingerprinting, 1. In forensic science, DNA finger printing is, used to solve problems of rape and some, complicated murder cases., , 6. Hybridization: Probe DNA is added to, the nitrocellulose filter paper containing, host DNA. The single-stranded DNA, probe pairs with the complementary base, sequence of the host DNA strand. As a, result DNA-DNA hybrids are formed on, , 2. DNA finger printing is used to find out the, biological father or mother or both, of the, child, in case of disputed parentage., 3. DNA finger printing is used in pedigree, analysis in cats, dogs, horses and humans., , Restriction, enzyme, Isolated purified, DNA, Sample, Electrophoresis, Restriction, digestion DNA fragments, Transfer of, DNA to, Selected single, membrane, stranded DNA, probes, , DNA extraction, , Southern blotting, , X-ray, Hybridization of DNA, , Fig. 4.18 : DNA Fingerprinting, Know the scientists, Father of DNA Fingerprinting in India. He was instrumental in making DNA, fingerprinting mainstream in India, for research and its forensic applications. He, obtained DNA probe from Y chromosome of female banded krait snake (in this snake, female has XY and male has YY chromosome). The unique segment obtained from this, chromosome is, banded krait minor (Bkm - DNA). It was used to developed probe for, the Indigenous DNA fingerprinting technique., Dr. Lalji Singh Contributions of Dr. Lalji Singh: i. He installed several dedicated laboratories on aspects, ( 1947 - 2017) of genetics such as population biology, structural biology and transgenic research. ii., His work in the field of DNA fingerprinting technology, contributed for, wildlife conservation, forensics,, evolution and phylogeny. iii. Established Centre for DNA Fingerprinting and Diagnostics (CDFD) in, late 1990s- making it nodal centre for DNA fingerprinting and diagnostics for all species and several, diseases. iv. Founded Laboratory for Conservation of Endangered Species (LaCONES)., , 90
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Activity :, Prepare physical model of DNA molecule (Watson-Crick model), Requirements :, , Labelled Diagram :, , Functions :, , 91
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Exercise, Q. 1 Multiple Choice Questions, 1. Griffith worked on ............., a. Bacteriophage, b. Drosophila, c. Frog eggs, c. Streptococci, 2. The molecular knives of DNA are, ………….., a. Ligases, b. Polymerases, c. Endonucleases, d. Transcriptase, 3. Translation occurs in the ..............., a. Nucleus, b. Cytoplasm, c. Nucleolus, d. Lysosomes, 4. The enzyme required for transcription is, .................., a. DNA polymerase, b. RNA polymerase, c. Restriction enzyme, d. RNAase, 5. Transcription is the transfer of genetic, information from .............., a. DNA to RNA, b. tRNA to mRNA, c. DNA to mRNA, d. mRNA to tRNA, 6. Which of the following is NOT part of, protein synthesis?, a. Replication, b. Translation, c. Transcription, d. All of these, 7. In the RNA molecule, which nitrogen, base is found in place of thymine?, a. Guanine, b. Cytosine, c. Thymine, d. Uracil, 8. How many codons are needed to specify, three amino acid?, a. 3, b. 6, c. 9, d. 12, 9. Which out of the following is NOT an, example of inducible operon?, a. Lactose operon, b. Histidine operon, c. Arabinose operon, d. Tryptophan operon, 92, , 10. Place the following event of translation, in the correct sequence, i. Binding of met-tRNA to the start, codon., ii. Covalent bonding between two, amino acids., iii. Binding of second tRNA., iv. Joining of small and large ribosome, subunits., A. iii, iv, i, ii, B. i, iv, iii, ii, C. iv, iii, ii, i, D. ii, iii, iv, i, Q. 2 Very Short Answer Questions:, 1. What is the function of an RNA primer, during protein synthesis?, 2. Why the genetic code is considered as, commaless?, 3. What is genome?, 4. Which enzyme does remove supercoils, from replicating DNA?, 5. Why are Okazaki fragments formed, on lagging strand only?, 6. When does DNA replication take, place?, 7. Define term- codon and codogen., 8. What is degeneracy of genetic code?, 9. Which are the nucleosomal 'core', histones?, Q. 3 Short Answer Questions:, Write short note on DNA packaging, in eukaryotic cell., Enlist the characteristics of genetic, code., Write a note on applications of DNA, finger printing., Explain the role of lactose in ‘Lac, Operon’., Q. 4 Short Answer Questions:, 1. Write a note on Human genome, project (HGP).
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2. Describe the structure of ‘Operon’., 3. In the figure belowA, B and C are three, types of, ., Amino acid, , Ribosome, Uracil, , A, , B, , C, , 4. Identify the labeled structures on the, following diagram of translation., C, CCG GCC ACU CCC, A, GGG, , B, , Part A is the, Part B is the, Part C is the, , ., ., ., , 5. Match the entries in column I with, those of column II and choose the, correct answer., Column I, , Column II, , A. Alkali treatment, , i. Separation of DNA, fragments on gel slab, , Q. 5 Long Answer Questions:, 1. Explain the process of DNA replication., 2. Describe the process of transcription in, protein synthesis., 3. Describe the process of translation in, protein synthesis., 4. Describe the ‘Lac-operon’., 5. Justify the statements. If the answer is, false, change the underlined word(s) to, make the statement true., i. The DNA molecule is double, stranded and the RNA molecule is, single stranded., ii. The process of translation occurs at, the ribosome., iii. The job of mRNA is to pick up, amino acids and transport them to, the ribosomes., iv. Transcription must occur before, translation may occur., 6. Guess (i) the possible locations of DNA, on the collected evidence from a crime, scene and (ii) the possible sources of, DNA., Evidence, , Possible, location of, DNA on the, evidence, , e.g. Eyeglasses e.g., pieces, , B. Southern blotting ii., Split, DNA, fragments into single, strands, C. Electrophoresis, iii. DNA transferred to, nitrocellulose sheet, , Bottle,, Glass, , D. PCR, , iv. X-ray photography, , E. Autoradiography, , v. Produce fragments, of different sizes, F. DNA treated with vi. DNA amplification, REN, , Can,, , Ear, , Sources of, DNA, , e.g. Sweat,, Skin, , Sides,, mouthpiece, , ---------------, , ----------------, , Handle, , Sweat,, skin, blood, , Used cigarette, , Cigarette butt, , -------------, , Bite mark, , -------------, , saliva, , -------------, , Surface area, , Hair,, semen,, sweat,, urine, , Project : Collect information about B and Z forms of DNA. Sketch the diagrams and write, the differences between these two forms., 93
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5, , Origin and Evolution of life, Observe and Discuss, , Can you recall?, , 1. Redi’s Experiment, , 1. What is evolution?, 2. Where was first life formed?, 3. Why are many species of plants and, animals getting (becoming) extinct?, 4. The Lamarck’s theory of inheritance of, acquired characters., 5. What is Speciation?, , 2. Louis Pasteur’s Experiment, , 5.1 Origin of life : (Protobiogenesis), The living matter shows attributes or, characters like responsiveness, growth,, metabolism, energy transformations and, reproduction., As far as origin of life is considered, it has, remained an enigma for intellectuals at all, times. Despite of advancements in various, fields like biochemistry, astrobioloy, geography,, molecular biology, etc. scientists are unable to, ascertain the truth. Various theories and, hypotheses have been proposed to find the, probable answer to this question., a. Theory of special creation :, It is the oldest theory and is based on, religious belief without any scientific proof. It, states that all living organisms are created by a, super-natural power., b. Cosmozoic theory/Theory of Panspermia:, This theory advocates that life did not arise, on the planet Earth. It may have descended to, the earth from other planets in the form of, spores or micro-organisms, called cosmozoa/, panspermia. Recently, NASA has reported, fossils of bacteria-like organisms on a piece of, Martian rock recovered from Antarctica., c. Theory of spontaneous generation, (Abiogenesis) :, According to this theory, life originated, from non-living material spontaneously. This, theory was disproved by Louis Pasteur., 94, , No, flies, , No, maggots, , Flies, , maggots, , Broth is boiled, Curved neck is, removed, , Broth remains free, maggots of microorganisms, Microorganisms, grow in broth, , Flies, , 1., , 2., , d. Theory of biogenesis :, According to this theory, living organisms, are always produced from pre-existing living, forms, by process called reproduction., Theory of biogenesis however could not, explain origin of first life on earth but could, explain only the continuity of life., 5.2 Chemical Evolution of Life (Self assembly, theory of origin of life ) :, According to this theory, life originated on, earth by combinations of several chemicals, through constant chemical reactions over a, long period of time. This theory is also called, self assembly theory of origin of life or, biochemical origin of life., This theory was first formulated by Haeckel, but later developed by the Russian scientist, Alexander I. Oparin (1924) and British biologist, J. B. S. Haldane (1929). The process of, chemical evolution can be divided into, following steps :
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a. Origin of Earth and Primitive, atmosphere:, The origin of universe was explained by, the Big-Bang theory of Georges Lemaitre, (1931). According to this theory the Universe, originated about 20 billion years ago by a, single huge titanic explosion. As the universe, expanded, the temperature decreased and, various galaxies of solid objects were formed., Milky Way is one such galaxy of which our, solar system is one small part. Earth is one of, the planets of solar system and originated about, 4.6 billion year ago. When formed, it was a, rotating cloud of hot gases and cosmic dust, called Nebula. The condensation and cooling, resulted in stratification with heavier elements, like nickel and iron passing to the core and, lighter ones like helium, hydrogen, nitrogen,, oxygen, carbon, etc. remaining on the surface., They formed the atmosphere of the earth. The, primitive atmosphere of the earth was quite, different from the present one and it was of a, reducing type, devoid of free oxygen., b. Formation of ammonia, water and, methane:, Primitive atmosphere was very hot. As it, slowly cooled, the lighter elements started to, react with each other. The early atmosphere, was rich in hydrogen, carbon, nitrogen and, sulphur of which hydrogen being more active,, it reacted with other elements to form chemicals, on earth like CH4, NH3, H2O and H2S., c. Formation of simple organic molecules :, As temperature of the earth decreased, steam, condensed into water that resulted in heavy, rain fall and the earth gradually cooled. Rain, water got accumulated on the land to form, rivers, streams, lakes, seas and oceans. The, atmosphere then did not contain ozone layer, and thus ultra-violet radiations reached the, surface of earth directly. Under the influence of, available energy sources such as ultra-violet, 95, , rays, radiations, lightening and volcanic, activities, the early molecules of hydrocarbons,, ammonia, methane and water underwent, reactions like condensation, polymerisation,, oxidation and reduction. These reactions, resulted in formation of simple molecules like, monosaccharides, amino acids, purines,, pyrimidines, fatty acids, glycerol, etc. All these, simple organic molecules accumulated at the, bottom of water bodies. Haldane described it, as the ‘‘hot dilute soup’’ or ‘‘primitive broth’’., It did not show any degradation due to absence, of free oxygen and enzymes., d. Formation of complex organic molecules:, The primitive broth was neutral and free from, oxygen. Polymerisation took place and simple, organic molecules aggregated to form new, complex, organic molecules like, polysaccharides, fats, proteins, nucleosides, and nucleotides. Polymerisation of amino acids, formed protoproteins which later formed, proteins. Formation of protein molecules is, considered as landmark in the origin of life., Proteins (enzymes) accelerated the rate of other, chemical reactions., e. Formation of Nucleic acids :, Nucleotides may have been formed by the, reaction between phosphoric acid, sugar and, nitrogenous bases (purines and pyrimidines)., Number of nucleotides join together to form, nucleic acids (RNA, DNA). Nucleic acids, acquired self-replicating ability which is a, fundamental property of living form., f., , Formation of Protobionts or Procells :, Nucleic acids along with inorganic and, organic molecules formed the first form of life, called protobionts. Protobionts are the, prebiotic chemical aggregates having some, properties of living system.
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Protobionts are formed due to coacervation, i.e. aggregation of organic molecules. Oparin, (1924) called them coacervates and Sidney, Fox called protenoids or microspheres., , Coacervates, , Fig. 5.1 : Coacervates, Coacervates are colloidal aggregations of, hydrophobic proteins and lipids (lipoid, bubbles). Coacervates grew in size by taking, up material from surrounding aqueous medium., As they grew, they became thermodynamically, unstable and split into smaller units, comparable, to daughter cells of budding organisms., Microspheres are protenoids formed from, colloidal hydrophilic complexes surrounded by, water molecules. These bodies may have outer, double-membrane, like primitive cell. Diffusion, and osmosis may have occurred across the, membrane. They were more stable than, coacervates. Coacervates and microspheres, were non-living colloidal aggregations of lipids, and proteinoids respectively. They had some, basic properties of living cells, such as growth, and division. These colloidal aggregations, turned into first primitive living system called, eobionts or protocell., g. Formation of first cell :, When RNA or DNA system developed, within protocells, they look like bacteria or, viruses. They regulated various metabolic, activities. First cell was anaerobic, heterotrophic, and obtained energy by chemoheterotrophic, processes., Urey and Miller’s Experiment :, Stanley L.Miller and his teacher Harold C., 96, , Urey provided the first experimental evidence, in support of chemical evolution theory of, Oparin., They designed a glass-apparatus called, spark-discharge apparatus., The apparatus (Fig. 5.2) was first sterilized, and evacuated. Methane, ammonia and, hydrogen gases were pumped in the proportion, of 1:2:2 into the glass chamber. A tube carrying, water vapour was also connected to the, chamber. Lightning effect was mimicked by, electric discharge carbon arc spark in the, chamber. Process of evaporation and, precipitation was also simulated by the use of, heating mantle and condenser respectively., The mixture of CH4, NH3, H2 was exposed, continuously to electric discharge for several, days causing the gases to interact, after which, these were condensed. The liquid collected in, the U-tube turned brown. Chemical analysis of, this liquid reported the presence of simple, organic compounds. (urea, amino acids, lactic, acid, etc). This experiment strongly supports, that the simple molecules present in the earth’s, early atmosphere combined to form the organic, building blocks of life., , Electrodes, CH4, NH3, To, vaccum, pump, , H3O, H2, Condenser, , Gasses, Carbon, Spark, Water, out, Water, in, Water droplets, , Boiling water, , Water containing, organic compounds, Liquid in water trap, , Fig. 5.2 : Urey and Miller’s Experiment
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RNA World Hypothesis :, Oparin Haldane theory and Miller Urey, experiment gives us an understanding that, pathway of origin of life on earth goes from, non-living to living. ‘Like begets like’, necessitates presence of stable genetic material, and cellular machinery to carry out routine, activities essential for survival., We are also aware that certain proteins, which we call enzymes, catalyse the chemical, reactions in the cell. It was in 1980 that Sidney, Altman and Thomas Cech independently found, out that RNAs can also act as biocatalysts., These catalytic RNAs are called as Ribozymes., For this discovery, Altman and Cech earned, Nobel Prize in chemistry in 1989., This discovery provided important support, for RNA World hypothesis. The hypothesis, suggests that early life must have been based, exclusively on nucleic acids, most probably, RNA. It was first proposed by Carl Woese,, Francis Crick and Leslie Orgel in 1960, long, before discovery of ribozymes., Fact is that RNA is found abundantly in all, living cells, it is structurally related to DNA, and chains of RNA can evolve or undergo, mutations, replicate and catalyse reactions, all, support this hypothesis., RNA selfreplicates, (via ribozymes), , RNA forms, from inorganic, sources, , RNA catalyses, protein synthesis, , Membrane formation, changes internal chemistry, allowing new functionality, , DNA becomes, master template, , RNA codes, both DNA and, protein, , Proteins catalyse, cellular activities, , Besides, biomolecules like Acetyl-Co-A, have a nucleotide in their molecular structure., Major evidence is existence of ribosome (the, protein assembly unit) in the cell. In ribosomes,, translation process is catalysed by RNA. (Refer, chapter- Molecular Basis of Inheritance)., These molecules might have undergone, repeated replication and mutation forming, varieties of RNA molecules with varying sizes, and catalytic properties. Eventually they might, have developed their own protein coats and, machinery to survive the assembly of primitive, cell. In due course, a double stranded stable, structure, the DNA, might have been formed, and thus continued the ongoing journey which, resulted in rich biodiversity on earth., 5.3 Organic Evolution :, Evolution (Latin word, e = from; volvere =, to roll) means the act of unrolling or unfolding, of nature. It brings about orderly changes from, one form to another. These changes result in, descendants becoming different from the, ancestors., Organic evolution can be defined as slow,, gradual, continuous and irreversible changes, through which the present day complex forms, of the life developed (or evolved) from their, simple pre-existing forms., According to Charles Darwin, evolution, is ‘descent with modification’. You have, already studied the Lamarck’s theory of, inheritance of acquired characters in 10th std., According to this theory, the traits are acquired, due to internal force, changes in environment,, new needs and the use and disuse of organs., After several generations, it gives rise to new, species., This theory was disproved by a German, biologist August Weismann, who cut the tails, of many rats for several generations but could, not find any change in size of tail even after, , Fig. 5.3 : RNA World Hypothesis, , 97
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21 generations. He concluded that variations, produced in somatic cells (somatoplasm) are, not inherited while variations produced in germ, cells (germplasm) are inherited to next, generation and he proposed the theory of, Germplasm., 5.4 Darwinism :, Before darwinism, several theories were, proposed to explain the process organic, evolution. Few of them are explained below :, Lamarck (1809) published theory of origin, of acquired characters. Which was then ruled, out., , Fig. 5.4 : Charles Darwin (1809 - 1882), Darwnism (theory of origin of species by, Natural Selection)., Charles Darwin as a naturalist travelled, extensively the world over from 27th December, 1831 to October 1836 and returned to England., Based on his collections of living and fossil, material he published a book ‘‘The origin of, species by Natural Selection’’ in 1859. Before, publishing his book, he was very much, influenced by C. Lyell (Geologist) who pointed, out that the natural forces that existed in the, past are same as those existing at present., Darwin observed that the natural forces resulted, in the changes in the earth’s crust along South, America. He observed variety of strange plants, and animal in Galapagos islands and other, nearby islands in the Archipealago in terms of, variations between the tortoises and finches., Similar observations were also made by, Wallace. He was also influenced by R. Malthus,, an Economist, who worked on human, population mentioning that the reproductive, 98, , potential of humans is greater than others. This, resulted in multiplication of human population, without corresponding increase in the food, supply. This increase lead to competition and, struggle for existence of human species., He was also influenced by plant/animal, breeders who by using artificial selection,, altered the characteristic of cultivated plant, and domestic animals., Darwinism is based on five main postulates:, 1., , 2., , 3., , 4., , Overproduction (Prodigality of nature), - It is the natural tendency to produce more, number of progeny in geometric ratio, for, perpetuation of the species. He observed, prodigality potential many species of, plants and animals e.g. Salmon fish, produces about 28 lakh eggs in a single, season. In a span of 750 years single pair, of elephants would produce 19,000,000, elephants. However the size of given, species in a given area remains relatively, constant because of fluctuations that occur, seasonally., Struggle for existence - Tendency of over, production leads to the struggle for, existence between the members of, population for limited supply of food or to, overcome, adverse, environmental, conditions or for a space or to escape from, enemies etc., Organic variations - The variations speak, for all kinds of differences that occur in, morphology, physiology, nutrition, habit, behavioural, patterns, etc., Darwin, recognized these variations as raw material, for evolution. Variations were observed, among members of the same species and, even in different species., Natural selection - Organic variations can, serve as evidence that for the some, organisms have better adapted to survive, under existing environmental conditions, than the others. In the struggle for existence, organisms with favourable variations are
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selected by the nature while those with, unfavourable variations perish. According, to Darwin, the principle by which useful, variations are preserved by nature, is called, ‘Natural Selection’. H. Spencer named, this process as ‘survival of fittest’., 5., , Origin of new species (speciation) - As, favourable variations are transmitted from, generation to generation, successive, generations become better adapted to, environment. Gradually these adaptation, with few new modification become fixed, in the life cycle and finally giving rise to a, new species., , Evidences Darwinism include - (i), Evolution of long-necked Giraffe to pluck and, eat more leaves from tall trees and woody, climbers. This adaptation became fixed in the, life for survival. The Giraffe borne tall could, survive in famine heat areas. This adaptation, was transmitted to their offspring. This is how,, present long-necked Giraffe came to existence., (ii) Black colour peppered moths evolved, gradually as new species. (iii) DDT resistance, in mosquitoes-intensive DDT spraying, destroyed all types of mosquitoes. However, some mosquitoes developed resistance to DDT, and survived the on slaught of DDT spray., Such resistant mosquitoes survived and, reproduce giving rise to more resistant, offspring., , e. According to natural selection new species, are formed by gradual accumulation of, useful variations. If it is so, then their, should be intermediate forms. But in most, cases intermediate form were not, recognised. Moreover, Darwinism also, could not explain existence of neutral, flowers and the sterility of hybrids., 5.5 Mutation Theory :, This theory was proposed by Hugo de Vries, (1901), after the rediscovery of Mendel’s work, (1900). He proposed this theory based on his, observations on seven generations of the plantevening primrose (Oenothera Lamarckiana)., He found that though most of the offsprings, resembled their parents in many characters,, some of the offsprings show the appearance of, sudden or spontaneous variation clearly, different from the phenotypic expression of the, parent. These sudden variations were called, mutations or discontinuous variations. The, variant offsprings produced variants and not, normal plants i.e. these changes were, inheritable. He also observed that some variants, also produced more variations. He noted that, these sudden changes are inheritable, and, proposed the Mutation theory., The main features of mutation theory are :, •, , Mutations are large, sudden and, discontinuous variations in a population., , •, , These changes are inheritable., , Drawbacks and Objections to Darwnism -, , •, , a. He considered minute fluctuating variation, as principal factors which are not heritable, and not part of evolution., , Mutations provide the raw material for, organic evolution. ‘, , •, , Mutation may be useful or harmful. Useful, mutations are selected by nature., , b. He also did not distinguish somatic and, germinal variation and considered all, variations are heritable., , •, , Accumulation of these mutations over a, period of time leads to the origin and, establishment of new species., , c. He did not explain the ‘arrival of the, fittest’. d. He also did not explain the cause,, origin and inheritance of variations and of, vestigial organs, nor he could explain the, extinction of species., , •, , Harmful mutation may persist or get, eliminated by nature., , 99
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Objections to Mutation Theory :, i., , •, , All individuals of the some species, constitute a population. The populations, occur in small groups of ‘interbreeding, populations’. Such small interbreeding, group of a population is referred as, ‘Mendelian population’., , •, , The total genetic information encoded in, sum total of genes in a Mendelian, population is called gene pool. Simply,, gene pool means the total number of genes, of all individuals in a population. The, gametes produced by individual furnish a, pool of genes of next generation from which, the genes will be selected., , •, , The migration of population effectively, alter the gene pool. The gene pool also, changes due to replacement of one, generation by another in the Mendelian, population. Thus any change in the gene, pool affects population., , •, , Genes are arranged linearly on the, chromosome having definite positions., According to Mendel, every gene that, influences a trait has two alleles. The, proportion of an allele in the gene pool, to, the total number of alleles at a given locus,, is called gene frequency., , •, , Modern synthetic theory comprises five, main factors that are broadly divided into, three main concepts like - i. genetic, variations caused due to various aspects, of mutation, recombination and migration., ii. natural selection and iii. isolation, for, explaining the evolution of species., , The large and discontinuous variation, observed by Hugo de Vries were actually, due to chromosomal aberrations were as, gene mutations usually bring about minor, changes., , ii. Rate of mutation is very slow as compared, to the requirement of evolution., iii. Chromosomal aberrations have little, significance in evolution as they are quite, unstable., Always Remember, 1. According to Darwin variations are small, and directional where as mutations are, large, sudden, random and direction less., 2. Darwin believed that the gradual, inheritable variations over a long period, of time, lead to Speciation (formation of, new species) while de Vries believed that, mutations are the cause of speciation., 3. A single step large mutation is called, saltation., 5.6 Modern Synthetic Theory of Evolution :, • It is the result of true synthesis of all, biological discipline. Studies pertaining to, genetical,, ecological,, anatomical,, geographical, palaeontological etc. were, persued to explain mechanism of evolution., Also due importance was given to both, mutations and natural selection., •, , •, , R. Fischer, J. B. S. Haldane, T. Dobzhansky, J. Huxley, E. Mayr, Simpson, Stebbins,, Fisher, Sewall Wright, Medel, T. H. Morgan, etc. are the main contributors of modern, theory of evolution., Stebbins in his book discussed five key, factors such as gene mutations, mutations, in the chromosome structure and number,, genetic recombinations natural selection, and reproductive isolation, contributed in, the evolution of new species., , a. Genetic variations : The change in gene, and gene frequencies, is known as genetic, variation. Genetic variations are caused by, following factors :, i. Gene Mutation : Sudden permanent, heritable change is called mutation., Mutation can occur in the gene, in the, chromosome and in chromosome number., Mutation that occurs within the single gene,, , 100
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is called point mutation or gene mutation., This leads to the change in the phenotype of, the organism, causing what is called, variation., ii. Genetic recombination : In sexually, reproducing organisms, during gamete, formation, exchange of genetic material, occurs between non-sister chromatids of, homologous chromosomes. This is called, crossing over. It produces new genetic, combinations which result in variation., Fertilization between opposite mating, gametes leads to various recombinations, resulting into the phenotypic variations, causing change in the frequencies of alleles., iii. Gene flow : Gene flow is movement of, genes into or out of a population. Gene, movement may be in the form of migration, of organism, or gametes (dispersal of, pollens), or, segments, of, DNA, (transformation). Gene flow also alters, gene frequency causing evolutionary, changes., iv. Genetic drift : Any random fluctuation, (alteration) in allele frequency, occurring in, the natural population by pure chance, is, called genetic drift. For example, when the, size of a population is severely reduced due, to natural disasters like earthquakes, floods,, fires, etc. cause elimination of particular, alleles from a population. Smaller, populations have greater chances for, genetic drift. It will result in the change in, the gene frequency. Genetic drift is also an, important factor for evolutionary change., v. Chromosomal, aberrations, :, The, structural, morphological change in, chromosome due to rearrangement, is, called chromosomal aberrations. It changes, the genes arrangement (order or sequence), that results in the variation. Chromosomal, aberrations occur due to a. Deletion : Loss of genes from, chromosome., , b. Duplication : Genes are repeated or, doubled in number on chromosome., c. Inversion : A particular segment of, chromosome is broken and gets, reattached to the same chromosome in, an inverted position due to 1800 twist., There is no loss or gain of gene, complement of the chromosome., d. Translocation, :, Transfer, (transposition) of a part of chromosome, or a set of genes to a non-homologous, chromosome is called translocation. It, is effected naturally by the transposons, present in the cell., ABCDE FGH, , • Deletion, , A B C E F GH, , loss of a chromosomal segment, , • Duplication, , ABCDEFGH, , ABCBCDEFGH, , repeat a segment, ABCDEFGH, , • Inversion, , ADCBEFGH, , reverses a segment, , • Translocation, , ABCDEFGH, , MNOCDEFGH, , move segment from one chromosome to another, , Fig. 5.5 : Chromosomal aberrations, b. Natural selection :, According to Darwin, natural selection is, the main driving force behind the evolution., This holds that genetic variations rise within, the population. The ‘fittest’ will be at the, selective advantage and will be more likely to, produce offsprings than the rest, as the ‘fit’, continues to enjoy greater survival and, reproductivity, new species will eventually, evolve., Alternatively, natural selection is the, process by which better adapted organisms, grow and produce more number of offsprings, in the population., It brings about evolutionary changes by, favouring differential reproduction of genes, that bring about changes in gene frequency, from one generation to next generation., , 101
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Selection against harmful mutations leads, to a mutation balance in which allele frequency, of harmful recessives remain constant, generation after generation., , Fig. 5.6 : Natural selection (Biston betularia, and Biston carbonaria), Natural selection encourages those genes, or traits that assure highest degree of adaptive, efficiency between population and its, environment. Industrial melanism is one of, the best example for natural selection. In Great, Britain, before industrilisation (1845) grey, white winged moths (Biston betularia) were, more in number than black-winged moth, (Biston carbonaria)., These moths are nocturnal and during day, time they rest on tree trunk. White-winged, moth can camouflaged (hide in the background), well with the lichen covered trees that helped, them to escape from the predatory birds. on, other hand, the black-winged moth resting on, lichen covered tree trunks were easy victims, for the predatory birds and their number was, reduced. During industrial revolution, large, number of industries came up in Great Britain., The industries released black sooty smoke that, covered and killed the lichens growing on tree, and turn the tree black due to pollution., This change become an advantage to the, black-winged moth that camoflaged well with, the black tree trunks and their number increased, while the white-winged moth become victims, to predatory birds due to which their number, reduced. Thus natural selection has resulted in, the establishment of a phenotypic traits in, changing the environmental conditions., , c. Isolation :, Isolation is the separation of the population, of a particular species into smaller units which, prevents interbreeding between them. Some, barrier which prevents gene flow or exchange, of genes between isolated populations, is called, isolating mechanism., Number of isolating mechanisms are, operated in nature and therefore divergence, and speciation may occur. The isolating, mechanisms are of two types namely,, geographical isolation and reproductive, isolation., I. Geographical Isolation :, It is also called as physical isolation. It, occurs when an original population is divided, into two or more groups by geographical, barriers such as river, ocean, mountain, glacier, etc. These barriers prevent interbreeding, between isolated groups., The separated groups are exposed to, different kinds of environmental factors and, they acquired new traits by mutations. The, separated populations develop distinct gene, pool and they do not interbreed. Thus, new, species have been formed by geographical, isolation. E.g. Darwin’s Finches., II. Reproductive Isolation :, Reproductive isolations occurs due to, change in genetic material, gene pool and, structure of genital organs. It prevents, interbreeding between population., Types of Isolating Mechanisms :, A. Pre-mating or pre-zygotic isolating, mechanism : This mechanism prevent, fertilization and zygote formation., i., , 102, , Habitat isolation or (Ecological isolation), : Members of a population living in the, same geographic region but occupy, separate habitats so that potential mates do, not meet.
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ii. Seasonal or temporal isolation : Members, of a population living in the same, geographic region but are sexually mature, at different years or different times of the, year., iii. Ethological isolation : Due to specific, mating behaviour the members of, population do not mate., iv. Mechanical Isolation : Members of two, population have difference in the structure, of reproductive organs., B. Post-mating or Post-zygotic barriers :, i. Gamete mortality - Gametes have a, limited life span. Due to one or the other, reasons, if union of the two gametes does, not occur in the given time, it results in the, gamete mortality., ii. Zygote mortality - Here, egg is fertilized, but zygote dies due to one or the other, reasons., iii. Hybrid sterility - Hybrids develop to, maturity but become sterile due to failure of, proper gametogenesis (meiosis). e.g. Mule, is an intergeneric hybrid which is sterile., Can you tell?, 1., 2., 3., 4., , What is variation?, What is mutation?, What is gene frequency?, Why variations are occurs in population?, , 5.7 Mechanism of organic evolution :, One has to give the importance to the, population while considering the mechanism of, evolution. It is the population that evolves and, not its individual members. Individual’s role is, to pass its genetic variation to its offspring., The following are the basic processes, which bring about evolution viz. Mutations,, gene recombination, gene flow (migration),, genetic drift, natural selection, isolation and, speciation., Mutations - These are permanent heritable, changes in the genetic material of an organism., , Mutations are already described earlier in this, chapter. Gene mutations produce new alleles, which are added to gene pool., Gene recombination - These are variation, produce due to coming together of alleles, during, sexual, reproduction., Gene, recombinations occur due to random union of, gametes, anaphasic separation of chromosomes, and crossing over., Gene flow - It is the transfer of gene during, interbreeding of populations that are genetically, different. As explained earlier in this chapter, gene flow is due to emigration and imigration., Its brings about changes in the allele frequency., Genetic drift - Any alternation in allete, frequency in the natural population by chance,, is called genetic drift. Concept of genetic drift, was first given Sewall wright, hence, called as, Sewall wright effect. For example, elimination, of a particular allele from a population due to, events like accidental death prior to mating of, an organism. Genetic drifts are random or, directionless. The effect of genetic drift is more, significant in small population than in large, population. Due to genetic drift, some alleles of, a population are lost or reduced by chance and, some others may be increased. Some time, a, few individuals become isolated from the large, population and they produce new population in, new geographical area. The allele frequency of, new population become different. The original, drifted population (i.e. colonizing ancestor/, pioneer) becomes ‘founders’ and the effect is, called founder effect., A bottle neck effect is seen when much of a, population is killed due to a natural disaster, and only a few remaining individuals are left to, begin a new population., Natural selection - It is a process by which, better adapted individuals with useful, variations are selected by nature and leave, greater or more number of progenies, (Differential reproduction)., , 103
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Number of Individuals, , Type of Natural selection :, a. Stabilizing selection : (Balancing selection), 1. Here more individuals of a population, acquired a mean character value., , 3. It reduces variations., 4. It does not lead to evolutionary change but, tend to maintain phenotypic stability within, population, therefore, it is described as, stabilizing selection., 5. Genetically stabilizing selection represents, a situation where a population is adapted to, its environment., Number of Individuals, , Selection against both extremes, , Population, after selection, Original, population, Time, , Fig. 5.7 : Stabilising selection, b. Directional selection :, 1. In this type, more individuals acquired, value other than the mean character value., 2. Naural selection acts to eliminate one of, the extremes of the phenotypic range and, favour the other. e.g. systematic elimination, of homozygous recessives., , Population, after selection, Original, population, Time, , Fig. 5.8 : Directional selection, c. Disruptive Natural selection :, 1. Here more number of individuals acquire, peripheral character value at both ends of, the distribution curve., 2. Nature select extreme phenotypes and, eliminate intermediate. Hence two peaks, are formed in distribution of traits., 3. This kind of selection is rare., 4. It ensures the effect on the entire genepool, of a population, considering all mating, types or systems., 5. Example - It was observed in the different, beak size of African seed cracker finches., The birds have different size of beak and, they feed on seeds. The avilable seeds were, of two kinds small and large sized seeds., Large beak sized birds feeds on large seeds, while small beak sized birds feed on small, seeds and their number was increased., Intermediate beak sized birds are unable to, feed on either type of seeds so their, population was decreased gradually and, then eliminated by natural selection., , 3. Directional selection operates for many, generations, it results in an evolutionary, trend within a population and shifting a, peak in one direction., 4. e.g. Industrial melanism, DDT resitant, mosquito etc., , 104, , Selection against the intermediates, , Number of Individuals, , 2. It tends to favour the intermediate forms, and eliminate both the phenotypic extreme., For e.g. More number of infants with, intermediate weight survive better as, compare to those who are over-weight or, under-weight., , Selection against an extremes, , Population, after selection, Original, population, Time, , Fig. 5.9 : Disruptive selection
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Isolation - It is separation of a single, interbreeding population into subunits., Isolation restricts gene flow between descrete, (non continuous population due to different, barriers like geographical barriers. (This part, is already explained in detail earlier in this, chapter), Speciation - The sub units of single, interbreeding population due to the, geographical barriers like river, mountains,, desert, sea etc. become isolated in such a way, that their interbreeding is prevented. This will, finally lead to origin of new species (i.e., speciation). (Discussed in detail ahead in this, chapter)., 5.8 Hardy-Weinberg’s principle :, It is also known as Hardy-Weinberg’s, equilibrium law. The law states that ‘at, equilibrium point both the gene (allele), frequency and geneotypic frequency remain, constant from generation to generation’. It, occurs only in the diploid, sexually reproducing,, large, free interbreeding population in which, mating is random and no selection or other, factors are present for changing the allele, frequency. e.g. A single locus has two alleles (A, and a). The frequencies of these allele are p, and q respectively. The allele frequency for any, locus is always one. i.e. P + Q = 1. The genotypic, frequencies of both the alleles are represented, by (p + q)2 = 1. The binomial expansion of this, is P2 + 2pq + q2 = 1 i.e. AA=P2, aa=q2 and for, 2Aa= 2pq., Hence P2 + 2pq + q2 = 1 This is a binomial, expansion of (p + q)2., This can be explained by punnet square as, follow., Hybrid A a, A (p), a (q), Hybrid, Aa, , A (p), , AA (p2), , Aa (pq), , a (q), , Aa (pq), , aa (q2), , Like allele frequency, the genotypic, frequencies together are also equal to 1., , There are few factors such as gene, migration (gene flow), genetic drift, mutation,, genetic recombinations, natural selection, nonrandom mating, etc. which affect or change the, Hardy-Weinberg equilibrilium,, If these factors do not occur in the, population, then population is genetically, stable or non evolving population., Can you tell?, In which conditions the gene frequency, of a population will remain constant?, 5.9 Adaptive Radiation :, The process of evolution which results in, transformation of original species to many, different varieties, is called, adaptive radiation., Darwin’s Finches is one of the best example, of adaptive radiation. During his visit to, Galpagos Islands. Charls Darwin also noticed, a variety of small birds. These birds are called, Darwin’s finches., , Fig. 5.10 : Darwin’s finches, Darwin concluded that the American main, land species of bird was the original one from, which they migrated to the different islands of, Galpagos. They adapted to the different, environmental conditions of these islands., From original seed eating features many other, forms with altered beaks evolved into, insectivorous features., Another example of adaptive radiation is, Australian Marsupials. In Australia, there are, many marsupial mammals who evolved from, common ancestor., , 105
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2. Moulds : These are the hardened, encasements formed in the outer parts, of organic remains which later decayed, leaving cavities. Body parts of plants or, animals later decays but the impression, still remains and becomes permanent., For example Foot – prints are formed, in this manner., , Can you tell?, 1. What is carbon dating and how does it, work ?, 2. What is fossils ?, 3. What is Homologous organs ?, 4. What is Embryology ?, 5.10 Evidences of organic evolution :, The theory of organic evolution states that, the present day complex organisms have, originated from earlier simpler forms of life., The process of evolution is supported by, evidences provided by various branches of, biology such as : Palaeontology, comparative, anatomy, embryology and molecular biology., A. Palaeontology : The study of ancient life, with help of fossils is called palaeontology., Fossils are the dead remains of plants, and animals that lived in past in various, geological layers., • The study of fossils provides the most, convincing and direct evidence of, evolution., • Fossils are formed in sedimentary rocks,, amber (yellowish fossils resin), ice, peat, bogs etc., • During fossilization, the primitive forms, of organisms occupy the older, lower, layers and the advanced forms occupy, the upper, more recent layers of the, earth., Types of fossils :, 1. Actual remains : These are most, common type of fossils. The plants,, animals and human bodies got, embedded in permafrost of arctic or, alpine snow remain preserved in the, actual state, e.g. Wooly Mammoth, in Siberia. Amber or hardened resin, contains preserved bodies of many, insects and arthropods., , 3. Cast : They are hardened pieces of, mineral matter deposited in the cavities, of moulds., 4. Compressions : Internal structure is, absent but a thin carbon film indicates, the outline of external features., Significance of Palaeontology :, 1. It is useful in reconstruction of phylogeny., 2. It helps in studying various forms and, structures of extinct animals., 3. It provides record of missing link, between two groups of organsims., 4. It helps in the study of habits of extinct, organisms., 5. Palaeontology provides the following, types of evidences., Connecting link (missing link) :, These are fossil forms transitional or, intermediate between two groups of organisms., It shows some characters to both the groups., Thus it indicate the evolutionary line Seymouria, (between amphibians and reptiles). e.g., Archaeopteryx (between reptiles and birds)., Archaeopteryx lithographica :, It is fossilized crow size toothed bird found, from jurassic rocks in Germany. It is known as, missing link between reptiles and birds because, it shows characters of both., Reptilian characters :, 1. Presence of long tail, claws and scales, on the body., 2. Single headed ribs., 3. Abdominal ribs are present which look, like ribs of crocodile., 4. Jaws with homodont teeth., , 106
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5. Sternum without keel., 6. Bones are solid (nonpneumatic)., 7. Hind limbs had four clawed digits., , Do you know ?, First fossil of Archaeopteryx was found in, Jurassic rocks of Bavaria. It was discovered, in 1861 and preserved in British museum by, Andreas Wanger., The second specimen found in 1877,, known as Archaeornis, is kept in the Berlin, museum., , Beak, Scales on the body, Teeth, , Clawed, Digits, , Wings, , Feathers, , B. Morphology : Morphology deals with, study of external structures while, anatomy, deals with study of internal structures. From, comparative study of morphology and anatomy, we can understand the evolutionary aspects, in the form of homologous, analogous and, vestigeal organs., a. Homologous organs : Homologous organs, are those organs, which are structurally, similar but perform different functions., For example :, 1. Forelimbs of vertebrates such as, lizzard, bird, bat, horse, whale and man,, , Fig. 5.11 : Archaeopteryx, Avian characters :, 1. Feathery exoskeleton., 2. Forelimbs are modified into wings., 3. Jaws are modified into beak., 4. Skull bone is completely fused., 5. Large rounded cranium., 6. Cranium with large orbits and a single, condyle., 7. Limb bones are bird like., 8. Hind limbs with four toes first toe is, opposible., , Humerus, Radius, Ulna, , Thus from the above study it is very clear, that birds evolved from reptiles. Huxley justified, this by calling birds as glorified reptiles., , Carpals, Bat, Whale, , Activity :, , Bird Man, , Horse, Lizard, , Complete the following chart., Animals, Connecting link, between, 1. Balanoglossus, ...................................., 2. .................., 3. Lung fishes, 4. ..................., , annelida and arthropoda, .............................., reptiles and mammals, , 5. Seymouria, 6. Ichthyostegia, , ............................., fishes and amphibia, , Metacarpals, Phalanges, , A, Leaf, Tendril, , Thorn, Stem, , Bougainvillea, , Cucurbita, , B, Fig. 5.12 : Homologous organs, 107
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all of them have humerus, radius-ulna,, carpals, metacarpals and phalanges, in their forelimbs. Forelimbs of these, vertebrates are structurally similar but, perform different functions., 2. Vertebrate heart and brain., 3. In plants, thorns of Bougainvillea, and tendrils of cucurbita represent, homology., The structural similarities between the, homologous organs indicates that they have a, common ancestory., Differences in homologous organs are, examples of divergent evolution or adaptive, radiation., b. Analogous organs : Analogous organs, are those which are structurally dissimilar, but functionally similar. These organs, have external superficial similarity due, to similar functions but they are different, anatomically., For e.g. wings of butterfly (insects) and of, birds look superficially alike but they are, no anatomically similar structures though, they perform similar functions., Other examples of analogous organs., , Fore wing, , Ulna, Hind wing, Insect, , Bird, , Fig. 5.13 : Analogous organs, c. Vestigeal organs : (Rudimentary organs), Vestigeal organs are imperfectly developed, and non-functional, degenerate structures, which were functional in some related, and other animals or in ancestors. The, vestigeal organs are no longer required by, the organism but indicate the relationship, with those organisms were these organs are, fully developed., Examples : Human beings show some, vestigeal organs like 1. Presence of vestigeal nictititating, membranes., 2. Presence of wisdom teeth (third molars)., 3. Coccyx (tail bone) : It is greatly reduced, in man since the tail is of no use due to, erect posture., , 1. Eye of the octopus (mollusca) and of, mammals. They differ in their retinal, position, structure of lens and origin of, different eye parts., , Canine, 1), , 2), , Plica semilumaris, , Third, molar, (wisdom, tooth), , 2. The flippers of penguins (birds) and, dolphins (mammals)., 3. Sweet potato (root modification) and, potato (stem modification) store food, in form of starch., Analogous organs leads to convergent, evolution i.e. different organisms shows same, superficial structural similarities due to similar, functions or habitat. These organs do not help, to trace the common ancestry. Thus analogous, organs do not have significant role in evolution., , 3), , 4), , Sacrum, , Colon, , Small, intestine, , Caecum, , Coccyx (fused tail vertebrae), , 108, , Vermiform appendix, , Fig. 5.14 : Vestigeal organs
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4. Vermiform appendix and the caecum. It, is functional in herbivorous mammals, for digestion of cellulose. In man due, to eating of cooked food it has lost its, function., Presence of these vestigeal organs provide, evidence that man has (evolved) descended, from simple primates., Can you recall?, Give examples of embryological, evidences studied in lower classes., d. Molecular Evidences :, 1. Cell is the basic structural and functional, unit of life in all organisms., 2. Similarities in proteins and genetic material, performing a similar function among, diverse organisms gives evidence of a, common ancestry., 3. Basic metabolic activities also occur in a, similar manner in all organisms., 4. ATP is the energy source in all living, organisms., 5.11 Speciation :, The process of formation of a new, species from the per-existing species is called, speciation., Species is a group of similar organisms, that can interbreed and produce a fertile, offspring in nature. New species are formed by, the following modes., a. Intraspecific Speciation :, i., , Allopatric speciation : Formation of, a new species due to separation of a, segment of population from the original, population by distanced or a geographical, barrier cutting across the species range., e.g. creeping glaciers, development of, mountains. Migration of individual also, causes allopatric speciation. The mode of, evolution here is called adaptive radiation, , ii., , e.g. 14 different species of finches in, Galapagos islands and several marsupial, species in the Australian continent., Sympatric speciation: Formation of, species within single population without, geographical isolation. These are formed, due to reproductive isolation. e.g. Cichlid, fishes in Lake Victoria. Mutations are, helpful in sympatric speciation., , b. Interspecific Speciation :, Hybridisation :, Two different species on crossing may give, rise to a new species. e.g. Mule is a hybrid, produced by interbreeding between a male, donkey and a female horse. Hinny is offspring, of male horse and female donkey., Can you recall?, 1. What are fossils? why should we study, fossils?, 2. How do we find age of fossils ?, 3. Where do we find fossils ?, 5.12 Geological time scale :, The planet earth with its present biodiversity, was not so when it was born. Study of fossils, tells us that life forms were not the same millions, of years ago (MYA). Geological time scale is, used to understand the sequence of events that, to place on the earth in different ages over, a period of time. It is divided into six major, ‘Eras’ Eras ended with major environmental, changes on earth resulting into extinction and, emergence of new species. The eras are further, divided into periods and epochs based on minor, but landmark events in each era. Table 5.15, shows the geological time scale at a glance., The first life appeared on the earth some, 2000 million years ago. It took billions of years, for this process to take place, from protenoids, to first cells the transition is still a mystery., Once formed the living forms diversified into, various groups. Life began in the sea water and, , 109
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plants were the first living beings to adapt to, terrestrial life. Fishes evolved and diversified., The lobefin group of fishes too got diversified., Some developed stout and strong fins and could, go to land and come back to water., The coelecanth was considered a living, fossils. It was thought that lobefins are extinct,, , but the variety of the lobefin fish, called, coelacanth was caught in 1938 in South Africa., Reptiles evolved from amphibians. They, are the first true land vertebrates. They do not, have to go to water for reproduction. (Hint :, think of amphibian and reptilian eggs). But, about 200 million years ago (mya) some reptiles, , Table 5.15 : Geological time scale, , Quarternary, , Era Period, , Tertiary, , Cenozoic, , 0.01-2.0, , Time, MYA, 0.1-0.6, , Epoch, , Angiosperms, Recent, (Holocene), , Age of mammals : Development, of modern man, birds, fishes and, insects. Development of human, culture., , 0.6 - 2.0, , Pleistocene Increase in herbs, , Extinction of great mammals., Appearance of primitive man., , 2-13, , Pliocene, , Hard woody plants, conifers, grasslands, bryophytes, monocots, , Emergence or origin of man., Evolution of ruminants - horse,, camel, elephant., , 13-26, , Miocene, , 26-38, , Oligocene, , 38-54, , Eocene, , Abundance of deciduous Formation of first man like apes., trees origin of grasses, Adaptive radiation or spread of, mammals., Rise of monocots and, Extinction of Archiac mammals,, flowering plants, Appearance of apes and monkeys., Turtles and crocodiles attained, development., Development of, Diversification of placental, angiosperms, mammals and modern birds., , 54-65, , Palaeocene Modernisation of, flowering plants, , Cretaceous, , 65-135, , Jurassic, , 135-165, , Triassic, , Mesozoic, , 2-6.5, , 165-225, , Plant life, , Animal life, , Arrival of early or first primates, rise, of placental mammals., , Decline of ferns sphenopsids (horsetails), and Gymnosperms, Ginkos, Gnetales. 1st, appearance of flowering, plants., Origin of angiospersms, Dominance of lycopods,, ferns, conifers, cycads., , Extinction of Dinasours and toothed, birds. Appearance of placental, mammals and first modern birds, , Dominance of, gymnosperms extinction, of seed ferns, , Appearance and rise of dinosours., Extinction of primitive amphibians., Diversification of reptiles. Rise of, oviparous mammals. Therapsids,, diversification of flies., , 110, , Age of reptiles. Dinasaurs dominant,, Appearance of toothed birds, (Archaeopteryx) Rise of marsupials.
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Palaeozoic, Proterozoic, Archaeozoic, , permian, Carboniferous, Devoniam, Silurian, Ordovician, Cambrian, , 16003800, , 600-1600, , 500-590, , 440-500, , 400-440, , 345-400, , 280-345, , 225-280, , No life, , No fossil records, , Tracheophyte ancestors,, chlorophyte ancestors, bacterial single-cellled, protista, blue green algae, , Rhynia like plants. All, types of marine algae, , Appearance of first, seedless vascular land, plants, abundant algae, , Appearance of lycopods, and ferns. Domiance of, algae, ascomycetean, fungi, , Origin of conifers, Decline of lycopods, Abundance of ferns,, cycads and conifers, , Primitive flat worms, annelids,, sponges, coelenterates, primitive, of, fossils, scanty, metazoans,, prokaryotes, , Abundance or age of trilobites,, Diversification of invertebrate phyla., , Abundance of diversed invertebrates., Appearance of first vertebrates, jawless fishes, Appearance of corals,, giant cephalopods like Nautilus., , Appearance of first terrestrial, animals, wingless insects and jawed, fish, , Appearance of first pro - Diversification of fishes. Evolution, gymnosperms. Formation of amphibians. Appearance of, of forests, wood decaying ammonites, fungi, chytrids and origin, of bryophytes., , Development of diverse, pteridophytes, mosses, and gymnosperms. age, of ferns and coal forests,, different fungal groups, , Origin of life, Simple unicellular forms like viruses,, bacteria and algae, , Abundance of amphibians (age of, amphibian).Appearance of reptiles, and winged insects., , Rise of moderninsects, Disappearance, of trilobites, appearance of mammal, like reptiles (Pelycosaurs). Decline of, amphibians., , 111, , Absence of living being, chemical evolution, Formation of earth,, 38004600, , * (MYA = Million Years Ago), , Azoic
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230-66 Ma:, Non-avian dinosaurs, , 2 Ma:, First Hominins, , 4550 Ma :, Formation of the Earth, Hominins, Mammals, Land plants, Animals, Multicellular life 4527 Ma :, Eukaryotes, Prokaryotes Formation of the Moon, , c. 380 Ma:, First vertebrate land animals, c. 530 Ma:, Cambrian explosion, 750-635 Ma:, Two Snowball Earths, , c. 4000 Ma: End of the, Late Heavy Bombardment, first life, , c. 3200 Ma:, Earliest start, of photosyntheisis, , c. 2300 Ma:, Atmosphere becomes oxygen-rich, first Snowball Earth, , Fig. 5.16 : Geological time scale pie diagram, moved back to aquatic mode of life and gained, fish like form as seen in Ichthyosaurs. The, giant reptiles like Dinosaurs once dominated, the earth but are now extinct. When was this?, Around 65 million years ago! why it must have, happened? Can we give affirmative reason for, this extinction? At around the same time giant, ferns were present on earth. However, they, also became extinct and got converted to fossil, fuels. How this must have happened?, Decline of giant reptiles marked the, begining of dominance of mammals. These, viviporous organisms were more intelligent., They could avoid danger. Early mammals, were small shrew like organisms, but this, group diversified. Whales, dolphins, seals, and sea cow live in water, bats are the flying, mammals, Kangaroo rats are fossorial, lemurs, are arboreal. Major physical disturbances led, , to phenomenon like the continental drift i.e., continents moved from their original place., As a consequence when south America joined, north America, ancestral forms of horse,, hippos, rabbits, etc. native to south america, were dominated by north American animals., At the same time, marsupial diversified into, different habitats in Australia. These survived, due to lack of competition., From the fossil records we can trace, complete evolutionary history of horse,, elephant, dog, etc. Human beings are the most, evolved animals on the earth., , 112, , Internet my friend, You may gather information out of curiosity, about geological events occurred in the past.
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5.13 Human Evolution :, Do you know ?, Use your brain power, , There is a difference of only 2.5 %, between DNA of chimpanzee and man while, between monkey and man it is 10 %., , Since your earlier school days you have, been solving mysteries/puzzles labelled as, use your brain power. Did you ever wonder, why human brain has such a capacity? Why, and how we evolved along these lines?, What is the extent of similarity between are, humans, chimpanzees and monkeys ?, It has been traced that the human, evolution appeared to have evolved from a, tree dwelling shrew like animal. This process, began in Palaeocene epoch. During this period,, dwindling forests forced arboreal mammals to, adapt to life on land. This descent must have, been the driving force. In the following chart, it, can be seen that we are most closely related to, gibbons, chimpanzees and gorillas., , The major evolutionary trends in transition, from ape to man are considered further. Special, characteristics have been acquired by man in, the course of evolution. Major changes that, took place in evolution of man include increase, in size and complexity of brain and enhanced, intelligence, increase in cranial capacity,, bipedal locomotion, opposable thumb, erect, posture, shortening of forelimbs and lengthening, of hind limbs, development of chin, broadening, of pelvic girdle, development of lumbar, curvature, social and cultural development, (articulated speech, art, development of tools,, etc)., , Class : Mammalia, Marsupials, (Pouched mammals), , Monotremes, (Egg laying mammals), , Eutherians, (Placental mammals), , Order : Primate, Sub order : Prosimii, , Lemurs, , New world monkeys, Long non-prehensile tail, e.g. squirrel monkey, spider monkey, Hyalobatidae, Arboreal apes,, Gibbons, , Suborder : Anthropoidea, , Tarsier, , Old world monkeys, Short non-prehensile tail, e.g. Baboons, macaques, langur, etc., Pongidae, semi-arboreal apes, Gorilla,, Chimpanzee, Orangutan, , Chart 5.17 : Classification of mammals, 113, , Hominoidea, Tailers, Great apes, , Hominidae, Erect posture, Human beings
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Table 5.18 : Human evolution, Heads, , Dryopithecus, , Ramapi- Australopi- Homo, thecus, thecus, habilis, , Homo, erectus, , Neanderthal Homoman, sapiens, , Appearance Ape like, , Man like Connecting Handy, link, man like, between, Ape and, man, , Ape man, , Advanced, prehistoric, man, , Modern, man, , Site of, Lake, fossil record victoria, of Africa,, Haritalynga,, Himachal, Pradesh, , Shivalik, Hills in, India and, even in, Kenya, , Toung, in South, Africa,, Ethiopia,, Tanzania, , Olduvai, Gorge, Tanzania, in Africa, , Java and, peking, , Neanderthal, valley,, Germany, , Africa, , Period, , Miocene, and early, pliocene, epoch 14, -12 mya, , late, pliocene, or early, pleistocene, epoch about, 4 – 1.8 mya, , Late, pliocene, or early, pleistocene, 2.5 to 1.4, mya, , middle of, pleistocene, epoch 1.5, mya ago, , Late, pleistocene, epoch, 100000 to, 40000 yrs, ago, , Not taller, than 4 feet,, jaws larger,, prognathus, face, chin, absent,, lumbar, curvature, present., , Lower, jaw, lighty, built,, dentition, more like, modern, man,, smaller, molars, , 5 feet in, height, prognathus, face,, massive, jaws, Huge, teath, chin, absent,, Bony eye, brow ridges, present, , Heavy, built short, prominant, brow, ridges low, forehead,, deep jaws,, chin absent,, outwardly, curved thigh, bones, , upright, , erect, , erect, , erect, , erect, , 450 to 600, cc, , 650 to 800 900 cc, cc, , 1400 cc, , 1450 cc, , man with, ape brain, , probably, did not, eat meat,, made, tools from, stones,, nicknamed, handy man, , used hide,, burried, their dead,, constructed, flint tools, , developed, distinct, races., Developed, cave art, about, 18000 yrs, ago, , Miocene, epoch 20 –, 25 mya, , Skeltal, features, , Posture, , semi erect, , Cranial, capacity, Special, features if, any, , close, similarity to, chimpanzee, , erect, , 114, , probably, ate meat,, omnivorous, might have, used fire
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Cranial capacity of human begins increased, over a period of time and large size of frontal, lobe helped in development of high forehead., Increase in intelligence necessitated, physical development so that body and brain, could be used effectively and productively., Freedom of forelimbs from locomotory function, and opposable thumb led to better utilization, of hands for holding objects effectively and, development of motor skills etc., Bipedal locomotion, upright posture, coupled with stereoscopic vision helped man to, move around safely on land., Evolutionary history of man was traced, with the help of fossil remains found over a, period of time., , Use your brain power, Even though the cranium of elephant, is larger than that of man, humans are, considered more intelligent than elephant., Why is it so ?, Some of our ancestors and their, evolutionary history is shown in the table., The above table clearly shows the, gradual increase in cranial capacity, shape of, skull and dentition of the ancestral humans till, date., Our journey of evolution still, continues....., , Fig. 5.19 : Human Evolution, Internet my friend, , Think about it, Human being is said to be most, evolved, intelligent living being. Yet we are, not self sufficient. Think of various aspects, for which we depend on other living beings, for our survival., , 1. Recently a fossil park has been, established in Gadchiroli district, of Maharashtra state. Find more, information about Wadadham fossil, park., 2. Find out information about caves in, India. One such place is in Madhya, Pradesh. It is at Bhimbetka rock shelter, in Raisen district. Here we can see cave, paintings by prehistoric humans., 115
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Activity :, Collect the information about the organisams depicted in the following diagrams, and write on the same., , A., , B., , C., , D., , E., , 116
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Exercise, Q. 1 Multiple choice questions., 1. Who proposed that the first form of life, could have come from per- existing nonliving organic molecules?, a. Alfred Wallace, b. oparin and Haldane, c. Charles Darwin, d. Louis Pasteur, , 6. Identify the wrong statement regarding, evolution., a. Darwin’s variations are small and, directional., b. Mutations are random and nondirectional., c. Adaptive radiations leads to, divergent evolution., d. Mutations are non- radamon and, directional., , 2. The sequence of origin of life may bea. Organic, materialsinorganic, materials – Eobiont- colloidal, aggregates- cell., b. Inorganic materials – organic, materials – colloidal aggregates –, Eobiont- cell., c. Organic, materialsinorganic, materials – colloidal aggregates cell, d. Inorganic, materialsorganic, materials – Eobiont- colloidal, aggregates - cell, , 7. Gene frequency in a population remain, constant due to –, a. Mutation, b. Migration, c. Random mating, d. Non- random mating, , 3. In Hardy - Weinberg equation , the, frequency of homozygous recessive, individual is represented by :a. P2, b. pq, c. q2 d. 2pq, , 8. Which of the following characteristic is, not shown by the ape?, a. Prognathous face, b. tail is present, c. Chin is absent, d. forelimbs are longer than hind limbs, , 4. Select the analogous organsa. Forelimbs of whale and bat, b. Flippers of dolphins and penguin, c. Thorn and tendrils of bougainvillea, and cucurbita., d. Vertebrates hearts or brains., , 9. .................. can be considered as, conncting link between between ape, and man., a. Austalopithecus, b. Homo hablis, c. Homo erectus, d. Neanderthal man., , 5. Archaeopteryx is known as missing, link because it is a fossil and share, characters of botha. Fishes and amphibians, b. Annelida and arthropoda., c. Birds and reptiles, d. Chordates and nonchordates., , 10. The Cranial capacity of Nanderthal, man was, a. 600 cc, b. 940 cc, b. 1400 cc d. 1600 cc, , 117, , Q. 2 Very short answer question., 1. Define the following termsa. Gene pool b. gene frequency, c. Organic evolution d. Population, e. Speciation
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2. What is adaptive radiation?, 3. If the variation occur in population by, chance alone and not by natural selection, and bring change in frequencies of an, allele. What is it called?, , Q. 5 Long answer questions., 1. Would you consider wings of butterfly, and bat as homologous or analogous, and why?, 2. What is adaptive radiation? Explain, with suitable example., , 4. State the Hardy – Weinberg eqnilibrium., 5. What is homologous organs?, , 3. By talking industrial melanism as one, example. Explain the concept of natural, selection., , 6. What is vestigeal organ?, 7. What is the scientific name of modern, man?, 8. What is coacervate?, , 4. Describe the, experiment., , 9. Which period is known as “age of, Reptilia”?, , 5. What is Isolation? Describe the different, types of reproductive Isolatons., , 10. Name the ancestor of human which is, described as man with ape brain., , 6. What is Genetic variations? Explain the, different factors responsible for genetic, variations., , Q. 3 Short answer question., , Urey, , and, , Millers, , Q. 6 Complere the chart., , 1. Write a note on Genetic drift., 2. Enlist the different factors that are, responsible for changing gene frequency., 3. Draw a graph to show that natural, selection leads to disruptive change., 4. Give the significance of fossils., 5. Write the objections to Mutation theory, of Hugo de vries., , Era, , Dominating group of, animal, , 1. Cenozoic, , .................................., , 2. ...................., , Reptiles, , 3. Palaeozic, , .................................., , 4. ...................., , Invertebrates, , 6. What is disrruptive selection? Give, example., Project :, , Q. 4 Matah the following., Columu- I, Column – II, 1. August Weismann a. Mutation theory, 2. Hugo de vries, , b. Germplasm theory, , 3. Charl Darwin, , c. Theory of acquired, characters, d. Theory of natural, selection, , 4. Lamark, , Prepare a diagrammatic chart of the, chemical evolution of life., , 118
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6, , Plant Water Relation, , Can you recall?, 1., 1. Which are the various parts of plant body?, 2. What are the functions of various parts of, plant body?, 3. Which plant tissues are involved in, transport of water and minerals?, , Curiosity Box :, 1. What is hydrogen bond?, 2. What are the meanings of specific heat,, heat of vaporization and heat of fusion?, 3. What are adhesive and cohesive forces?, Water molecules have good adhesive and, cohesive forces of attraction. Due to high, surface tension and high adhesive and cohesive, force, it can easily rise in the capillaries. It is, therefore, a significant molecule that connects, physical world with biological processes., , Use your brain power, You know that we need a water pump, to lift water at top of the building. but, how, does plants lift the water from soil upto, canopy without any pump?, Plant obtains variety of substances like, water, minerals, nutrients, food and gases, like O2 and CO2, from its surroundings., Productivity in plants is mainly affected by the, non-availibility of water., Water is considered as ‘elixir of life’., Water constitutes almost 90 to 95% of most, plant cells and tissues. Water helps the cells, to maintain turgidity and shape. It shows, following properties due to which it has great, biological importance., , 6.2 Water absorbing organ:, Root :, Root is the main organ of water and, mineral absorption. In terestrial plants, plants, absorb water in the form of liquid from the soil, however, epiphytic plants like orchids absorb, water vapours from air with the help of epiphytic, roots having special tissue called velamen., Typical root is divisible into four different, regions. In the zone of absorption, epidermal, cells (epiblema cells) form unicellular hair like, extensions called root hairs., , 6.1 Properties of water:, It is in the liquid form at room temperature, and is the best solvent for most of the solutes., It is inert inorganic compound with neutral pH, when in pure form. Due to this, water is best, transporting medium for dissolved minerals, and food molecules. It is best aqueous medium, for all biochemical reactions occurring in, the cells. It is an essential raw material for, photosynthesis. Water has high specific heat,, high heat of vaporization and high heat of, fusion. Due to this, it acts as thermal buffer., These various properties are due to hydrogen, bonds between the water molecules., , Maturation zone, Root hair zone, Root hair, Zone of elongation, Meristematic region, Root cap, , Fig. 6.1 a. : Root tip showing root hair zone, A root hair cell, Mitochondria, , Cell membrane, Cell wall, , Nucleus, , Vacuole, , Cytoplasm, , Root epithelial, cells, , Fig. 6.1 b. : Structure of root hair, , 119
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Structure of root hair :, Root hair is cytoplasmic extension, (prolongation) of epiblema cell. Each root hair, may be approximately 1 to 10mm long and, tube like structure. It is colourless, unbranched,, short-lived (ephemeral) and very delicate. It, has a large central vacuole surrounded by thin, film of cytoplasm, plasma membrane and thin, cell wall, which is two layered. Outer layer is, composed of pectin and inner layer is made up, of cellulose. Cell wall is freely permeable but, plasma membrane is selectively permeable., 6.3 Water available to roots for absorption:, Plants absorb water from the rhizosphere, (the microenvironment surrounding the root)., Water present in the soil occurs as gravitational, (free) water, hygroscopic water, combined, water and capillary water. Water percolates, deep, due to the gravity, in the soil, is called, ‘gravitational water’. This is not available, to plants for absorption. Fine soil particles, imbibe/ adsorb water and hold it. This is called, ‘hygroscopic water’. Roots cannot absorb it., Water present in the form of hydrated oxides, of silicon, aluminum, etc., is called ‘combined, water’. It is also not available to plants for, absorption. Some amount of water is held in, pores present between the neighbouring soil, particles, due to capillarity. This is called, capillary water that is avilable for absorption., 6.4 Absorption of water by roots from soil:, Root hair absorbs water by employing three, physical processes that occur sequentially- viz., imbibition, diffusion and osmosis., , a. Imbibition:, Imbibition is swelling up of hydrophillic, colloids due to adsorption of water. Substance, that adsorbs water / liquid, is called as imbibant, and water/ liquid, that gets imbibed is called, as imbibate. The root hair cell wall is made, up of pectic compounds and cellulose which, are hydrophillic colloids. During Imbibition,, water molecules get tightly adsorbed without, the formation of solution. Imbibition continues, till the equilibrium is reached. In other words,, water moves along the concentration gradient., Imbibition is significant in soaking of seeds,, swelling up of dried raisins, kneading of, flour etc., Use your brain power, Why do the wooden doors become, very hard to close and open in rainy season?, b. Diffusion: Diffusion means to disperse., Diffusion can be defined as the movement of, ions/ atoms/ molecules of a substance from the, region of their higher concentration to the region, of their lower concentration. The movement, is due to the kinetic energy of the molecules., Diffusion continues till an equilibrium is, reached. Thus, water passes into the cell by, diffusion through a freely permeable cell wall., Water is now at the interface of cell wall and, plasma membrane., Diffusion results in the diffusion pressure, (D. P.) which is directly proportional to the, number of diffusing particles. Diffusion, pressure of pure solvent (pure water) is always, , Activity :, Try this at your home., A. Take 10 ml of pure water in a suitable glass vessel and put 2 - 3 raisins in it. Observe the, changes in raisins since the time you put them in water till they become fully swollen i.e., turgid. Why did raisins become turgid?, B. Take 10 ml of pure water and add 5 gms of either sugar or salt to it. Let it dissolve and then, put the same turgid raisins in it and observe the changes in raisins. What changes did occur, in raisins and why? Discuss your observations with your teachers., 120
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more than the diffusion pressure of solvent, in a solution. The difference in the diffusion, pressures of pure solvent and the solvent in a, solution is called Diffusion Pressure Deficit, (DPD) or Suction Pressure (SP). The term, was coined by B.S. Meyer (1938). Now a, days, term water potential is used for DPD. In, colloquial language, the term DPD is actually, the thirst of a cell with which it absorbs water, from the surroundings. Water arround cell, wall has more diffusion pressure than cell, sap. Due to this, water moves in the cell by, diffusion. Diffusion is significant in plants in, the absorption of water, minerals, conduction, of water against the gravity, exchange of gases, and transport and distribution of food., Outside of cell, , Cytoplasm, , Water molecules, , Water-selective, pore (aquaporin), , Membrane bilayer, , Fig. 6.2 : Diffusion of water into plant cell, across the plasma membrane, , Use your brain power, 1. When you burn an incense stick in one, corner of room, its fragrance spreads all, over the room in a short time. How does, it happen?, 2. How does the water come out through, the surface of porous earthen pot?, , c. Osmosis : It is a process by which water enters, into the cytoplasm of the root hair cell. Osmosis, is a special type of diffusion of solvent through, a semipermeable membrane. The cytoplasm, of root hair cell contains minerals, sugars,, etc. In other words, solution inside the cell is, more concentrated (stronger) than outside the, cell (weaker). Therefore, solvent from weaker, solution enters into cytoplasm (i.e. to stronger, solution) of cell through a semipermiable, plasma membrane. This migration of solvent is, called Osmosis., Thus, water at the interface of cell wall and, plasma membrane, enters into the cytoplasm of, the root hair cell due to osmosis., With respect to the concentration and, osmotic migration, three types of solutions are, recognized viz,, i. Hypotonic (weak solution or strong, solvent) having low osmotic concentration., ii. Hypertonic (strong solution or weak, solvent) having high osmotic concentration., iii. Isotonic having such a concentration of, solution where there is neither gain nor, loss of water in an osmotic system. In other, words, concentration outside and inside the, cell is same., Osmosis is of two types viz, Exo-osmosis, and Endo-osmosis., Exo-osmosis : It is the migration of solvent, from the cell outside. It causes flaccidity of cell., Endo-osmosis : It is the migration of the, solvent into the cell. It causes turgidity of, cell i.e. cytoplasm becomes turgid. Turgidity, increases the turgor pressure (T. P.) of the cell., T. P. is the pressure exerted by turgid cell sap on, to the cell membrane and cell wall. In a fully, turgid cell, DPD is zero. Cell wall being thick, and rigid, exerts a counter pressure on the cell, sap. This is called Wall pressure (W. P.). In a, fully turgid cell, T. P. = W. P. but operating in, opposite direction., Osmotic pressure (O. P.) : The pressure, exerted due to osmosis is osmotic pressure., , 121
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Osmotic pressure is a pressure of the solution,, which is required in opposite direction, so as to, stop the entry of solvent molecules into the cell., More simply, osmotic pressure of a solution, is equivalant to the pressure which must be, exerted upon it to prevent flow of solvent across, a semipermeable membrane., Therefore, D. P. D. = O. P. - T. P., ( T. P. = W. P.), D. P. D. = O. P. - W. P., In a flaccid cell, T. P. is zero DPD = OP, In a turgid cell, DPD is zero TP = OP, , 6.5 Water Potential (ψ):, According, to, the, principle, of, thermodynamics, every component of a system, is having a definite amount of free energy, which is used to do work. Osmotic movement, of water is on the basis of free energy. Free, energy per molecule in a chemical system, is, called its chemical potential., Chemical potential of water is called water, potential. It is represented by Greek letter psi, (ψ). Water potential of protoplasm is equal but, opposite in sign to DPD It has negative value., The unit of measurement is in bars/ pascals/, atmospheres., Water potential of pure water is always, zero. Addition of any solute in it, decreases its, psi (ψ) value. Therefore, it has negative value., , Do you know ?, Improtance of T. P. : It keeps cells and, organelles stretched; provides support to, the non-woody tissues; essential for cell, enlargement during growth; maintains shape, of cell and facilitates opening and closing of, stoma., Improtance of Osmosis : It is responsible, for absorption of water into root; maintains, turgidity of cell; facilitates cell to cell, movement of water; offers resistance to, drought, frost, etc; also helps in the drooping, of leaflets and leaves in vicinity of “touch me, not” plant., , D. P. D. is now termed as water potential., O. P. is now termed as osmotic potential., T. P. is now termed as pressure potential. It, has always positive value., Water always flows from less negative, potential to more negative water potential, (i.e. from high water potential area to low, water potential area). Difference between, water potential of the adjacent cells decides, movement of water through plasmodesmata, across the cells., , Facilitated diffusion : The passive absorption, of solutes when mediated by a carrier, is, called Facilitated diffusion. Particles that, are lipid soluble can easily diffuse through, lipoproteinous cell membrane. The diffusion, of hydrophilic solutes has to be facilitated, because their diffusion across the membrane, is difficult. Membrane proteins provide, such sites for facilitated diffusion. These, proteins are aquaporins and ion- channels., These proteins help move substances across, membranes without the expenditure of energy., Concentration gradient must be present for the, molecules to be diffused through facilitated, diffusion., , Factors affecting water absorption:, i. Presence of capillary water is essential., ii. Rate of water absorption is maximum at, soil temperature between 200 to 300C., iii. High concentration of solutes in soil water, reduced the rate of absorption of water., iv. Poorly aerated soil shows poor absorption, rate., v. Increased transpiration accelarates the rate, of absorption of water in the irrigated soil., 6.6 Plasmolysis:, Exo-osmosis in a living cell when placed, in hypertonic solution, is called plasmolysis., During plasmolysis, protoplast of cell shrinks, and recedes from cell wall. Thus, cell becomes, , 122
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flaccid. In a plasmolysed cell, a gap is, developed between cell wall and the protoplast., This gap is filled up by outer solution., In a plasmolysed cell, T. P. is always zero., When such cell is placed in hypotonic solution,, endo-osmosis occur, making cell turgid. This, is called deplasmolysis. In a fully turgid cell, T. P. = O. P. hence, DPD is always zero., 6.7 Path of water across the root (i.e. from, epiblema upto xylem in the stelar region) :, Water is absorped by root hair cell, through, imbibition diffusion, osmosis,, sequentially. Consequently the cell becomes, turgid. Its turgar pressure increases, but its DPD, value decreases. However, the immidiately, adjacent cortical cell inner to it, has more DPD, value, because its O. P. is more. Therefore,, cortical cell will suck water from the turgid root, hair cell. It then becomes turgid. The flaccid, root hair cell now absorbs water from soil., Water from the turgid cortical cell is sucked, by inner cortical cell and the process goes on., Thus, a gradient of suction pressure (DPD) is, devloped from cells of epiblema to the cortex, of the root. Consequently water moves rapidly, across the root through loosely arranged, living cells of cortex, followed by passage, cells of endodermis and finally into the cell of, pericycle. Protoxylem is in the close proximity, with pericycle., , Absorption of water being a continous, process, a sort of hydrostatic pressure is, developed in living cells of root. This is called, root pressure. It is due to root pressure, water, from pericycle is not only forced into the xylem,, but also conducted upwards against the gravity., Pathway of water across the root essentially, occurs in two ways viz, apoplast and symplast., Pathways, Apoplast, Vacuolar, , The apoplastic (non-living) pathway, provides a route toward the vascular stele, through free spaces and cell walls of the, epidermis and cortex. An additional apoplastic, route that allows direct access to the, xylem and phloem is along the margins of, secondary roots. Secondary roots develop, from the pericycle, a cell layer just inside the, endodermis. The endodermis is characterized, by the Casparian strip, a suberized layer that, forces all to move in the symplast in order to, enter the vascular system. Since secondary, roots grow through the endodermis, a direct, pathway to the xylem and phloem is available, that bypasses the Casparian strip and allows, to enter the vascular system without moving, into the symplast (living tissue)., , Symplastic, path, , Apoplastic, path, , Casparian, strip, , Xylem, , Fig. 6.3 : Pathways for water uptake, by the root, , Transmembrane, , When some amount of water passes, across the root through the cell wall and the, intercellular spaces of cortical cells of root, it, is then called apoplast pathway. This pathway, occurs up to endodermis., , Endodermis Pericycle Phloem, , Cortex, , Symplast, , When water passes across from one living, cell to other living cell through plasmodesmata,, then it is called symplast pathway. It is also, called transmembrane pathway., 6.8 Mechanism of absorption of water :, Mainly, there are two ways/ modes of, absorption of water viz, passive absorption and, active absorption., 123
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a. Passive absorption :, It is the main way of absorbing water, through the roots and not by the roots from soil, into the plant. The driving force is transpiration, pull and it thus proceeds through DPD gradient., There is no expenditure of energy (ATP) as, water moves in accordance to the concentration, gradient. Hence, it is passive absorption. About, 98% of the total water absorbed in plants, occur, passively. Passive absorption occurs during, day time when transpiration is in progress. It, stops at night when transpiration stops., Rapid transpiration creates a tension in the, xylem vessel due to negative water potential., This tension is transmitted to xylem in the, roots. Consequently water is pulled upwards, passively., During passive absorption, no ATP is, utilized. Obviously, the rate of respiration is not, affected. In plants, water is mainly absorbed, passively., b. Active absorption :, Here, water is absorbed due to activity, of roots. Root cells play active role in the, absorption of water. The driving force is the root, pressure developed, in the living cells of root., Active absorption occurs usually at night when, transpiration stops due to closure of stomata. As, water absorption is against the DPD gradient,, there is expenditure of ATP (energy) generated, through the respiratory activity of cells., Active absorption may be of two kinds, viz, osmotic and non-osmotic :, 1. Osmotic absorption : Atkins and Priestly, (1922) proposed that water is absorbed from soil, into xylem of the root according to the osmotic, gradient. To create osmotic conditions, there is, an expenditure of energy. But such absorption, does not directly require an expenditure of, energy., A gradient of DPD develops from cell of, epiblema to pericycle due to activity of living, cells of root. As the process is continuous,, , a hydrostatic pressure, called root pressure,, is developed in root cells. This root pressure, forces water from pericycle to xylem and then, upwards to the stem., 2. Non-osmotic absorption : Kramer and, Thimann (1959) proposed this theory., Sometimes, water is absorbed from soil against, the concentration gradiant. Such absorption, requires an expenditure of energy released, during respiration, directly. Poor supply of, oxygen retards water absorption. Moreover, low temperature retards water uptake because, of decrease in the rate of respiration. Use of, metabolic inhibitors also retards the rate of, respiration and thus the water uptake., 6.9 Translocation of water:, The transport of water with dissolved, minerals from root to other aerial parts like, stem and leaves, against the gravity, is called, translocation or ascent of sap., Translocation of water occurs through, the lumen of conducting elements of xylemtracheids and vessels, in all vascular plants., Ringing experiment has proved that xylem is, the path of ascent of sap., Several mechanisms/ theories have, been put forth to explain the mechanism of, translocation of water. The theories includevital force theory, relay pump theory, physical, force theory, root pressure theory, etc. We shall, consider following three theories :, a. Root Pressure Theory (Vital Theory) :, According to this theory, the activity, of living cells of root is responsible for, translocation of water. J. Pristley proposed this, theory. When a stem of potted plant is cut few, inches above the soil by a sharp knife, xylem, sap is seen flowing out/ oozing out through the, cut end. This exudation at the cut end of stem is, a good proof for the existence of root pressure., As water absorption by roots is constant and, continous process, a hydrostatic pressure is, developed in the living cells of cortex of root., , 124
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This is termed as root pressure by S. Hales. It is, due to root pressure water along with dissolved, minerals is not only forced into xylem but it is, also conducted upwards against the gravity., Root pressure seems to be largely an, osmotic phenomenon and its development is an, active process. The value of root pressure is +1, to +2 bars which is enough to pump water to, a height of 10 to 20 meters. The factors like, oxygen, moisture, temperature of soil, salt, contents, etc. influence the root pressure., , Manometer, , Manometer to measure, exudation pressure from, cut stump, , Final level, Initial level, Stump, , b. Capillarity theory (physical force theory):, According to this theory, physical forces, and dead cells are responsible for ascent of sap., This theory was put forth by Bohem in, (1863). Wick dipped in an oil lamp, shows, capillarity due to which oil is raised upwards., The conduction of water in a straw dipped in, water, is raised to a certain height because of, capillarity. The height to which water is raised, depends on the diameter of the straw., Capilarity is because of surface tension,, and forces of cohesion (attraction between like, molecules) and adhesion (attraction between, unlike molecules). Xylem vessel/ tracheid with, its lumen is comparable with straw. Water, column exist because of combined cohesive, and adhesive forces of water and xylem wall,, due to capillarity. It is because of capillarity, water is raised or conducted upwards against, the gravity, to few centimeters only., Objections/ Limitations of capillarity theory:, Few important objections are :, , Fig. 6.4 : Experiment to demonstrate root, pressure, , i., , Objections/ limitations of root pressure, theory:, Although, ascent of sap takes place due, to root pressure, there are certain objections, raised, such as i., , It is not applicable to plants taller than 20, meters., , ii. Ascent of sap can also occur even in the, absence of root system., iii. Root pressure value is almost nearly zero in, taller gymnosperm trees., iv. In actively transpiring plants, no root, pressure is developed., v. Xylem sap under normal condition is under, tension i.e. it shows negative hydrostatic, pressure or high osmotic pressure., To sum up therefore, root pressure is not, the sole mechanism explaining the ascent of, sap in all plants of varying heights.., , Capillary tube (xylem) must be continously, and completely hollow from one end to the, other end but tracheids in the xylem show, closed end-walls., , ii. The lower end of capillary tube i.e. xylem, must be in direct contact with soil water., However, there exists a barrier of root, cortex between xylem and soil water., iii. Narrower the capillary tube, greater is the, height to which water column is raised., Thus, taller trees should show xylem, vessels with very narrow bore (diameter)., However, in nature the tall trees show, xylem vessels having wider bore., Hence, to sum up capillarity can not be the, sole mechanism to explain ascent of sap in all, the plants of varying heights., c. Cohesion- tension theory (Transpiration, pull theory) :, This is presently widely accepted theory, explaining ascent of sap in plants. It was put, , 125
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forth by Dixon and Joly (1894). This theory is, based on two principles., Cohesion and adhesion, and transpiration, pull :, A strong force of attraction between water, molecules, is called cohesive force. While, a strong force of attraction between water, molecules and lignified wall of lumen of xylem, vessel, is called adhesive force., Due to combined cohesive and adhesive, forces a continous water column is developed, (formed) in the xylem right from root upto the, tip of the topmost leaf in the plant., Transpiration pull : The transpiration pull, developed in the leaf vessel is transmitted down, to root and thus accounts for the ascent of sap., Excess water is lost in the form of vapour,, mainly through the stomata found on leaf., This water loss increases D. P. D. of mesophyll, cells. These cells withdraw water ultimately, from xylem in the leaf. In otherwords, due to, continous transpiration, a gradient of suction, pressure (i.e. D. P. D.) is developed right from, guard cells up to the xylem in the leaf. This, will create a tension (called negative pull or, transpiration pull) in the xylem. Consequently,, water column is pulled out of xylem. Thus,, water is pulled upwards passively against the, gravity leading to the ascent of sap., Objections/ Limitations of transpiration pull, theory:, i., , For transpiration pull to operate, water, column should be unbroken and continous., However, due to temperature fluctuations, during day and night, gas bubbles may enter, in water column breaking the continuity., , ii. This mechanism assumes that tracheids are, more efficient than the vessels, as their end, walls support water column., However, vessels are more evolved, than tracheids and are more efficient., , iii. If plant is smeared with vaseline in order to, stop transpiration, even then ascent of sap, occurs., iv. Ascent of sap also occurs in deciduous, plants that have shed all of their leaves., These observations point to the fact that, besides physical forces, activity of living cells, seems to be necessary for lifting the water, column up., 6.10 Transport of mineral ions :, Soil serves as main source for minerals., Minerals constitute most commonly occuring, solid, crystalline inorganic materials obtained, from earth’s crust. Minerals play an important, role in the day to day life of plant. Minerals are, absorbed by plants in the ionic (disolved) form,, mainly through roots and then transported., Do you know ?, •, , •, , Minerals that play important role in, the day to day life, are called essential, elements. About 36 to 40 elements are, incorporated in the plant’s life., Some minerals like C, H, O, P, N, S, Mg, required in large quantity, are called, macro elements. While minerals like Cu,, Co, Mn, B, Zn required in small quantity,, are called micro elements., , The analysis of plant ash demonstrates, that minerals are absorbed by plants from soil, and surroundings. Absorption of minerals is, independent of that of water., Absorbed mineral ions are pulled in, upward direction along with xylem sap because, of transpiration pull. This could be understood, when the ascending sap is analysed. Mineral, ions are needed in the areas of the plant viz., apical, lateral, young leaves, developing, flowers, fruits, seeds and storage organs., Hence, from the source (root), these are pulled, and transported ascendingly through the sap, and gets unloaded by fine veins through the, , 126
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process of diffusion in the vicinity of cells., Cells uptake them actively., , food from one part to the other part, is called, translocation of food., , Soil would not be the only source for mineral, uptake. Mineral ions can be remobilized within, the parts of the plant. Older parts (like leaves in, deciduous plants) export their ions to younger, leaves before the fall. Most readily mobilized, ions are like phosphorus, sulphur, nitrogen, and potassium but the ions from structural, components like calcium is not remobilized., , Path of translocation : Food is to be, translocated to longer distances in higher, plants. Hence plants must have adequate, channels for the transport of food. Sieve tubes, and vessels are structurally ideally suited, for longitudinal (vertical) translocation. The, ringing experiment, structure and distribution, of phloem, chemical analysis of phloem sap, and use of isotope 14C, clearly point out that the, phloem tissue is primarily responsible for flow, of food in longitudinal downward direction., The horizontal (lateral) translocation occurs, from phloem to pith or phloem to cortex via, medullary rays in the stem., Food is always translocated in the form of, sucrose (soluble form) and always along the, concentration gradient from source to sink. The, transport of food occurs in vertical and lateral, direction., , Internet my friend, 1. The general roles of minerals in the life, of plants., 2. The role of essential minerals in the day, to day life of plants., Analysis of xylem exudate also shows, that some nitrogen travels as inorganic ions, whereas much of it is carried in the organic, form like amino acids and related compounds., Small amount of inorganic molecules of, phosphorus and sulphur are also carried. It was, a belief earlier that xylem transports inorganic, and phloem transports organic molecules., However, it is not correct because some, exchange of materials also occurs between, xylem and phloem., Do you know ?, •, •, , Vertical translocation : In vertical, (longitudinal) transport, food is translocated, in downward direction from leaves (source) to, stem and root (sink). It also occurs in upward, direction during germination of seed, bulbils,, corm, etc. Upward translocation also occurs, from leaves to growing point of stem, to, developing flowers and fruits situated near the, ends of the branches of stem., , Different modes of passive absorption and, active absorption of minerals in plants., Carrier concept of active absorption., Sieve plate, , 6.11 Transport of food :, All the plant parts require continous supply, of food for nutrition and developement. In, higher plants, there is a great differentiation and, division of labour. Chloroplasts are confined to, green cells of leaves where food is synthesized., The non-green parts like root and stem must, received food from leaves. The part where food, is synthesized is called source and while part, where it is utilized, is called sink. Food has to, travel from source to sink. This movement of, 127, , Companion cell, , Sieve tube, , Cytoplasm, , Fig. 6.5 : L. S. of sieve tube, , Sieve, tube, element
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Lateral translocation : It occurs in the root and, stem. When food is translocated from phloem, to pith, it is called radial translocation and, from phloem to cortex, it is called tangential, translocation., The transport of food through phloem is, bidirectional. Phloem sap contains mainly, water and food in the form of sucrose. But, sugars, amino acids and hormones are also, transported through phloem., Mechanism of sugar transport through, phloem :, Several mechanisms/ theories like, diffusion, activated diffusion, protoplasmic, streaming, electro-osmosis, pressure-flow, etc., are put forth. The most convincing theory is, Munch’s pressure flow theory or mass flow, hypothesis., Ernst Munch proposed that photosynthetic, cell synthesizes glucose. Hence, its osmotic, concentration increases. Due to endo-osmosis, water from surrounding cells and xylem,, is absorbed. The cell becomes turgid. Due, to increase in turgor pressure, sugar from, photosynthetic cell is forced ultimately into the, sieve tube of the vein. This is called loading of, Vein., At the sink end, root cell utilizes sugar, and also polymerizes excess sugar into the, starch. Its osmotic concentration is lowered., Exo-osmosis occurs. Water in the root cell is, lost to surrounding cells, thereby decreasing, the turgidity of cell. Turgor pressure is lowered., Hence, a turgor pressure gradient is developed, from sieve tube in the leaf to the root cell., Consequently, food is translocated along the, concentration gradient, passively. This is Vein, unloading. At the sink end sugar is used and, excess water exudes into the xylem., Main objection to this theory is that this, mechanism does not explain bidirectional, transport of food. More over, according to, Munch, pressure flow is purely a physical, process., , 6.12 Transpiration :, Plants absorb water constantly and, continously. Hardly 5% of the total water, absorbed by roots that is utilised for cell, expansion and plant growth. Remaining 95%, water becomes surplus which is then lost into, the atmosphere, through its aerial parts. Hardly, 1% of surplus water is lost in the form of liquid, and 99% of surplus water, is lost in the form of, vapour. The loss of water in the form of liquid, is called guttation. It occurs through special, structures called water stomata or hydathodes., The loss of water in the form of vapour is called, transpiration that occurs through leaves, stem,, flowers and fruits. Most of the transpiration, occurs through the leaves (called foliar, transpiration). The actual water loss during, transpiration occurs through three main sites, - cuticle, stomata and lenticels. Accordingly,, three types of transpiration are recognized viz., cuticular, stomatal and lenticular., Water evaporates, from the leaves, Veins carry water, into the leaves, , Water is drawn up, the stem to the leaves, , Roots take up water, from the soil, , Fig. 6.6 : Transpiration, i. Cuticular transpiration:, Cuticle is a layer of waxy substance- cutin,, present on outer surface of epidermal cells of, leaves and stem. Cuticular transpiration occurs, by simple diffusion and contributes 8-10% of, the total transpiration. Cuticular transpiration, , 128
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occurs throughout the day and its rate is, inversely proportional to thickness of cuticle., ii. Lenticular transpiration:, Lenticels are small raised structures, composed of loosely arranged complementary, cells. Each lenticel is a porous tissue consisting, of cells with large intercellular spaces in, the periderm of the secondarily thickened, organs and the bark of woody stems and roots, of dicotyledonous flowering plants. Lenticels, are present in bark of old stem and pericarp, of woody fruits but are absent in leaves., Lenticular transpiration contributes only, about 0.1-1.0% of total transpiration. Rate of, , Do you know ?, •, •, , The number of stomata per unit area of, leaf, is called stomatal frequency., The correlation between the number of, stomata and number of epidermal cells, per unit area, is called stomatal index (I)., , 6.13 Structure of stomatal apparatus :, Typical stomatal apparatus consists of two, guard cells, stoma and accessory cells., Subsidiary cell, , Epidermal cells, , Inner thick, wall, Nucleus, , Lenticular pore, , Stoma pore, , Loose complementary, cells, , Guard cell, , Fig. 6.8 (a) : Structure of guard cell, Guard cells, Stomatal, pore, , Fig. 6.7 : Structure of lenticel, lenticular transpiration is very slow. It also, occurs throughout the day., , Chloroplast, , iii. Stomatal transpiration:, Stomata are minute apertures formed of, two guard cells and accessory cells. They are, located in the epidermis of young stem and, leaves. Leaves generally show more number, of stomata on the lower surface. Depending, upon distribution of stomata on leaves, leaves, are categorized into three types namely, epistomatic- on upper epidermis (Hydrophytese.g. Lotus), hypostomatic- on lower epidermis, (Xerophytes- e.g. Nerium) and amphistomaticon both surfaces (Mesophytes- e.g. Grass)., Stomatal transpiration occurs only during, daytime. (Exception: Desert plants)., , Fig. 6.8 (b) : Open and closed stoma, Stomata are minute, elliptical pores, bounded by two kidney/ dumbbell shaped, guard cells. Guard cell is a type of epidermal, tissue which may be called as modified,, epidermal parenchyma cell. They are kidneyshaped in dicotyledons and dumbbell-shaped, in grasses., , 90 to 93% of total transpiration occurs, through stomata and that too during day time, only., 129, , Epidermal, cells, Subsidiary, cells, Chloroplast, Guard cells, Stomatal, aperture, A. Kidney shaped, B. Dumbbell shaped, , Fig. 6.9 : Types of guard cells
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In Cyperus, both kidney- and dumbbellshaped guard cells are present., Guard cells are living, nucleated cells with, unevenly thick walls. Inner wall (wall facing, stoma) of guard cells is thick and inelastic, and, its lateral wall is thin and elastic. Guard cells, contain few chloroplasts which are capable of, poor photosynthesis. Guard cells have ability to, change their size and form due to which stoma, opens (widens) or closes (narrows)., Stoma is an elliptical pore formed due, to specific arrangement of guard cells. It is, through the stoma, excess water is lost in the, form of vapour., Accessory cells : These are specialized, epidermal cells surrounding the guard cells., Their number is variable and are the reservoirs, of K+ ions. These are also called subsidiary, cells., Opening and Closing of Stoma :, Opening and closing of stoma is controlled, by turgor of guard cells. During day time,, guard cells become turgid due to endosmosis., Thus turgor pressure is exerted on the thin, walls of guard cells. Being elastic and thin,, lateral walls are stretched out. Due to kidney, or dumb-bell like shape, inner thick walls are, pulled apart to open (widen) the stoma. During, night time, guard cells become flaccid due to, exosmosis. Flaccidity closes the stoma almost, completely. Endosmosis and exosmosis occur, due to diurnal changes in osmotic potential of, guard cells. Different theories are proposed to, explain diurnal changes in osmotic potential., According to starch-sugar interconversion theory (Steward 1964), during day, time, enzyme phosphorylase converts startch, to sugar, thus increasing osmotic potential of, guard cells cosing entry of water there by gaurd, cells are stretched and stoma widens. The, reverse reaction occures at night brining about, the closure of stoma., Phosphorylase, Starch, , (Day), Sugar, , Night, (Stoma opens), , (Stoma closes), , According to theory of proton transport, (Levitt-1974), stomatal movement occurs due, to transport of protons H+ and K+ ions. During, daytime, starch is converted into malic acid., Malic acid dissociates to form Malate and, protons. Protons are transported to subsidiary, cells and K+ ions are imported from them., Potassium malate is formed that increases, osmolarity and causes endosmosis. Uptake of, K+ ions is always accompanied with Cl¯ ions., At night, uptake of K+and Cl- ions is, prevented by abscissic acid, changing the, permeability of guard cells. Due to this guard, cells become hypotonic and thereby become, flaccid., Significance of Transpiration :, Advantages:, i. It removes excess of water., ii. It helps in the passive absorption of water, and minerals from soil., iii. It helps in the ascent of sap., iv. As stomata are open, gaseous exchange, required for photosynthesis and respiration,, is facilitated., v. It maintains turgor of the cells., vi. Transpiration helps in reducing the, temperature of leaf and in imparting, cooling effect., Disadvantages:, Excessive transpiration leads to wilting, and injury in the plant. It may also lead to the, death of the plant., Transpiration is ‘A necessary evil’ :, For stomatal transpiration to occur, stoma, must remain open, during day time. When, stomata are open then only the gaseous exhange, needed for respiration and photosynthesis, will, take place. If stomatal transpiration stops, it will, directly affect productivity of plant through the, loss of photosynthetic and respiratory activity., Hence for productivity, stomata must remain, open. Consequently transpiration can not be, avoided. Hence, Curtis (1926) regarded, transpiration as ‘a necessary evil’., , 130
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Activity :, Prepare stomatal frequency chart for any six angiospermic plants in your area., Plant Name, , Details, , 131
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Exercise, Q. 1 Multiple Choice Questions, 1. In soil, water available for absorption, by root is ..................., a. gravitaional water, b. capillary water, c. hygroscopic water, d. combined water, , 8. Water absorption takes place through, ............., a. lateral roots, b. root cap, c. root hair, d. primary root, 9. Due to low atmospheric pressure the, rate of transpiration will ............., a. increase, b. decrease rapidly, c. decrease slowly, d. remain unaffected, , 2. The most widely accepted theory for, ascent of sap is .............., a. capillarity theory, b. root pressure theory, c. diffusion, d. transpiration pull theory, , 10. Osmosis is a property of .................., a. solute, b. solvent, c. solution, d. membrane, , 3. Water movement between the cells is, due to ............., a. T. P., b. W. P., c. DPD, d. incipient plasmolysis, , Q. 2 Very short answer questions., 1. What is osmotic pressure?, 2. Name the condition in which protoplast, of the plant cell shrinks., 3. What happens when a pressure greater, than the atmospheric pressure is applied, to pure water or a solution?, 4. Which type of solution will bring about, deplasmolysis?, 5. Which type of plants have negative root, pressure?, 6. In which conditions transpiration pull, will be affected?, 7. Mention the shape of guard cells in, Cyperus., 8. Why do diurnal changes occur in, osmotic potential of guard cells?, 9. What is symplast pathway?, , 4. In guard cells, when sugar is converted, into starch, the stomatal pore ............., a. closes almost completely, b. opens partially, c. opens fully, d. remains unchanged, 5. Surface tension is due to .............., a. diffusion, b. osmosis, c. gravitational force d. cohesion, 6. Which of the following type of solution, has lower level of solutes than the, solution?, a. Isotonic, b. Hypotonic, c. Hypertonic, d. Anisotonic, 7. During rainy season wooden doors warp, and become difficult to open or to close, because of ..............., a. plasmolysis, b. imbibition, c. osmosis, d. diffusion, , Q. 3 Answer the following questions., 1. Describe mechanism for absorption of, water., 2. Discuss theories of water translocation., 3. What is transpiration? Describe, mechanism of opening and closing of, stomata., , 132
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4. What is transpiration? Explain role of, transpiration., , Q. 4 Long answer questions., 1. Describe structure of root hair., , 5. What is significance of transpiration?, Explain root pressure theory and its, limitations., 6. Explain capillarity theory of water, translocation., 7. Why is transpiration called ‘a necessary, evil’?, 8. Explain movement of water in the root., 9. Define and or explain the terms:, Osmosis,, diffusion,, plasmolysis,, imbibition, guttation, transpiration,, ascent of sap, active absorption, DPD,, turgor pressure, water potential, wall, pressure, root pressure., 10. Distinguish between a) Osmotic pressure, and turgor pressure b) Diffusion and, osmosis., 11. Enlist macronutrients and micronutrients, required for plant growth., 12. How are the minerals absorbed by the, plants?, , 133, , 2. Write on journey of water from soil to, xylem in roots., 3. Explain cohesion theory for translocation, of water., 4. Write on the mechanism of opening and, closing of stoma., 5. What is hydroponics? How is it useful in, identifying the role of nutrients?, 6. Explain the, minerals., , active, , absorption, , of, , 7. Write on macro- and micro nutrients, required for plant growth., Project :, 1. Prepare powerpoint presentation, different types of transpiration., , for
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7, , Plant Growth and Mineral Nutrition, Do you know ?, , Can you recall?, , Apical meristem : In vascular plants, growth, is restricted to the apices of root and shoot. It, is responsible for growth in length/ height and, the differentiation or cell types. It contributes, to the primary growth., Intercalary meristem : It is located at the, node or at the base of internode of stem. It, is primarily responsible for increasing length, of internodes and also for formation of leaf, primordia and lateral buds., Lateral meristem : It is located laterally along, the axis of dicotyledons and gymnosperms. It, is located as strip in the vascular bundles of, stem of dicots. It is called vascular cambium., It is responsible for increase in the girth of the, stem due to addition of secondary vascular, tissues., , 1. Do you think that the growth is property of, living beings only?, 2. Is there any difference between plant, growth and animal growth?, , 7.1 Plant growth :, Growth is one of the characteristic features, of living organisms. Growth as a phenomenon, has two aspects viz. quantitative and, qualitative. Quantitative aspect speaks for an, increase in the length, breadth, size, volume,, body mass or dry weight and number of cells., Growth as a quantitative change is a final end, product of successive metabolism., Qualitative aspect talks about the change, in the nature of growth where development, is an ordered change or progress while, differentiation leads to higher and more, complex state. Growth thus can be defined as, permanent, irreversible increase in the bulk of, an organism, accompanied by the change of, form., In multicellular (vascular) plants, growth, is indeterminate and occurs throughout, the life indefinitely. It is restricted to some, specific region called meristems which are, the regions where new cells are constantly and, continuously produced. Meristems are of three, types based on location viz. Apical, Intercalary, and Lateral., Do you know ?, Root and stem show indefinite or, indeterminate growth. However, in organs, like leaves, flowers and fruits, growth is, determinate. i.e. they grow up to certain, genetically destined size. In unicellular, plants, growth is uniform and determinate., , 7.2 Phases of growth :, The cells in the meristem divide, enlarge, and get differentiated. Corresponding to these, three stages, there are three phases of growth :, A. Phase of cell division/ formation : Cells, of meristem are thin walled, non-vacuolated, having prominent nucleus and granular, cytoplasm. Meristematic cell undergoes, mitotic division to form two new cells. One, cell remains meristematic and the other cell, undergoes enlargement and differentiation. In, this phase, rate of growth occurs at a slower, pace (Lag phase)., B. Phase of cell enlargement/ elongation :, The newly formed cell becomes, vacuolated, osmotically active and turgid due, to absorption of water. The turgidity results in, the enlargement of cell - both lengthwise and, breadthwise. In this phase new wall materials, and other materials are synthesized to cope, up with the enlargement. The growth rate, in this phase occurs at an accelerated pace, (exponential or Log phase)., , 134
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C. Phase of Cell maturation/ differentiation :, The enlarged cell now becomes specialized, to perform specific fuction and attains maturity, - both morphological and physiological. In this, phase, rate of growth slows down and comes to, a steady state (stationary phase)., Plumule, Zone of mature, cells, Zone of cell, differentiation, , Zone of cell, elongation, , A, , B, , Zone of cell, formation, , Fig. 7.1 Phases of growth in root Position of radicle at the begining (A) and at, the end (B), 7.3 Conditions for Growth :, The, different, environmental, and, physiological conditions necessary for the, growth include - Water, supply of nutrients,, , temperature, oxygen, Carbon/ Nitrogen ratio,, gravitational force, light and growth hormones., The chief conditions are explained below :, Water is the essential component of, protoplasm and maintains turgidity of the cell., It acts as aqueous medium for biochemical, reactions. Microelements and Macroelements, are nutrients required for the proper growth, of the plant. Optimum Temperature ranges, between 25-350C. Oxygen is essential for, respiration and the release of energy. Light is, very much essential for germination of seed and, photosynthesis. Gravitational force decides, the direction of growth of the shoot and root., 7.4 Growth Rate and types of growth :, Growth rate :, It is the increased growth per unit time. It, is also called efficiency index. Rate of growth, can be measured by an increase in the size and, area of different plant organs like leaf, flower, and fruits., The ratio of change in the cell number (dn), over the time interval (dt) is called Absolute, growth rate (AGR). Alternatively, it is the, measurement and comparison of total growth, per unit time., , Growth in plants can be measured in terms of...., 1. Increase in the number of cells produced - e.g. single maize root apical mesistem can give rise, to more than 17,500 new cells/Hour., 2. Increase in surface area of the leaf - e.g. growth of dorsiventral leaf., 3. Increase in length - e.g. growth of pollen tube., 4. Increase in volume of a fruit - e.g. In watermelon flower, ovary after fertilization increases in, its size/ volume by upto 3,50,000 times., 5. Increase in girth of shoot., 6. Increase in dry weight of organ., Various methods for the measurement of linear growth of stem and radicle are as follows:, 1. Direct method : It can easily be measured with the help of ordinary measuring scale. It is a, simple method., 2. Horizontal microscope : It is used to measure growth in fields., 3. Auxanometer : This equipment is used for precise measurement of linear growth of shoot., There are two types of an auxanometers viz, a) Arc auxanometer b) Pfeffer’s auxanometer, 4. Crescograph : It records primary growth very accurately. It magnifies growth upto 10,000, times giving information of growth per second. It is developed by sir J. C. Bose., , 135
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initially but later on there is a rapid growth, at exponential rate. Geometric growth can be, expressed mathematically by an equation., , Types of growth :, There are two types of growth viz,, arithmetic growth and geometric growth., , Height of the plant (L), , dn, AGR =, dt, The AGR, when divided by total number of, cells present in the medium, gives Relative, growth ratio (RGR). Alternatively, RGR refers, to the growth of a particular system per unit, time, expressed on a common basis or it is the, ratio of growth in the given time/ initial growth., AGR, RGR = n, AGR and RGR are useful in describing the, dynamics of cell growth in culture., , a, b, , Time (t), , Graph 7.2 : Constant linear growth, , a. Arithmetic growth : Here, rate of the, growth is constant and an increase in the, growth occurs in arithmetic progression. i.e. 2,, 4, 6, 8 cms etc.In this type of growth, the rate of, growth is constant., After mitosis one of the daughter cell, continues to divide and the other cell takes, part in the differentiation and maturation., e.g. elongation of root at a constant rate, best, explains arithmetic growth. Linear curve is, obtained when growth rate is plotted against, the time. Arithmetic growth is expressed, mathematically by an equation,, It is expressed as,, Lt = Lo + rt, Where, Lt = Length at time ‘t’, Lo = Length at time ‘Zero’, r = Growth rate, t = Time of growth, When graph of length (L) is plotted against, the time (t), a linear curve is obtained as, indicated in the diagram., b. Geometric growth :, Cell divides mitotically into two. Here,, both the daughter cells continue to divide and, redivide repeatedly. Such growth is called, geometric growth. Here, growth rate is slow, 136, , W1 = Wo ert, W1= Final size , Wo = initial size, r = growth rate, t = time of growth, e = base of natural logarithm, a. Arithmetic, , b. Geometric, , c., , Zygote divided, , Geometric phase:, all cells divide, , Arithmetic phase :, These cells divide, This cells do not, divide, , = Cells capable of, division, = Cells that have, lost capacity to, divide, , Digrammatic representation of : a. Arithmetic, b., Geometric grwoth and c. Stages during embryo, development showing geometric and arithmetic phases, , Fig. 7.3 : Growth rate
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We can also observe quantitative, comparison between the growth of living, system in two ways., Measurement and comparisons of total, growth per unit time is called the Absolute, growth rate(AGR) whereas the growth of, the given system per unit time expressed on, a common basis per unit initial parameter is, called the Relative growth rate(RGR)., , Population size, , J-shaped curve, , Year, , Graph 7.5 : Exponential Growth curve, B1, 55 cm2, , 10 cm2, , 5 cm2, A, , Stationary phase, , Size/ weight of the organ, , A1, , B, , 50 cm2, , Fig. 7.4 : Growth rate comparison, In the above example, two leaves ‘A’, and ‘B’ are of different sizes but show same, absolute increase in area in a given time. Both, leaves grow and increase their area by 5cm2, to produce ‘A’ and ‘B’ leaves. ‘A’ leaf of 5cm2, in size grows 5cm2/ day then its RGR would, be 100%. If the leaf is 50cm2 in size and the, growth rate/day is 5cm2 then its RGR would, become 10%., 7.5 Growth curve :, It is a graphic representation of the total, growth against time. There are three types of, curves viz, Linear, Exponential and Sigmoid., Arithmetic growth curve is linear while, Geometric growth curve is exponential., Corresponding to three distinct phases, of growth, growth rates differ. In Lag phase,, growth rate is slow. In Exponential (Log), phase, growth rate is faster and reaches its, maximum. In Stationary phase, growth rate, gradually slows down. When a graph of rate of, growth against time is plotted for three phases, of growth, a sigmoid curve is obtained., , Lag phase, Time, , Graph 7.6 : Sigmoid Growth curve, The total time (period) required for all, phases to occur, is called Grand Period of, Growth., 7.6 Differentiation, De-Differentiation, ReDifferentiation :, a. Differentiation :, It is maturation of cells derived from apical, meristem of root and shoot. Permanent change, in structure and function of cells leading to, maturation, is called differentiation. During, cell differentiation, cell undergoes few to, major anatomical and physiological changes, e.g. Parenchyma in hydrophytes develops, large schizogenous interspaces for mechanical, support, buoyancy and aeration. The maturation, is at the cost of capacity to divide and redivide., b. Dedifferentiation :, The living differentiated cell which has, lost the capacity to divide, may regain the same, as per the need and divide. Thus, permanent, (mature) cell undergoes dedifferentiation and, becomes meristematic e.g. interfascicular, , 137
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cambium and cork cambium are formed from, parenchyma cells between vascular bundles, and inner most layer of cortex, respectively., c. Redifferentiation :, The cells produced by dedifferentiation, once again lose the capacity to divide and, mature to perform specific function. This, is called redifferentiation e.g. secondary, xylem and secondary phloem are formed, from dedifferentiated cambium present in the, vascular bundle., , stage show different forms of leaves in the same, plant e.g. heterophylly in cotton, coriander,, larkspur (Delphinium). The environmental, heterophylly is shown by Ranunculus flabellasis, (butter cup). The intrinsic plasticity is found in, coriander and cotton. Heterophylly is exhibited, in the same plant in different growth phases or, under different environmental conditions., , 7.7 Development :, It refers to the ordered or progressive, changes in shape, form and degree of, complexity. It includes all the changes occurring, in sequence from the germination of seed upto, the senescence or death during life cycle of, plants. Thus development includes growth,, morphogenesis, maturation and senescence., , 1, Juvenile, , 3, , 2, Adult, , Terrestrial habitat, , 4, , Seed germination, , Water habitat, , Meristem, , Fig. 7.8 Heterophylly, , Cell division, , Can you tell?, , Plasmatic growth, , 1. Is there any relation between phases of, growth and regions of growth curve?, 2. Which plant organ does show both, arithmetic and geometric growth?, 3. Differences between arithmetic and, geometric growth., , Cell elongation, Cell maturation, Mature cell, Senescence, Death, , Fig. 7.7 Flow chart of development, 7.8 Plasticity :, It is the capacity of being moulded, formed, or modeled. It is the ability of plants to form, different kinds of structures (i.e. to change) in, response to different environmental (external), or internal stimuli, in various phases of life., In many plants, juvenile stage and mature, , 7.9 Growth Hormones :, The term ‘hormone’ was coined first by, Starling (1906) in animal physiology. The, internal factors that influence growth are called, growth hormones or growth regulators as they, inhibit, promote or modify the growth. Growth, promoters are auxins, gibberellins (GA) and, cytokinins (CK). Growth inhibitors in plants, are ethylene and abscissic acid (ABA). All, phytohormones are growth regulators., , 138
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Know the Scientist :, The auxin is the first hormone to be, discovered in plants. Discovery of auxins, dates back to 19th century when Charles, Darwin (1886) was studying tropism in, plants. He exposed canary grass coleoptile to, unilateral light. He concluded that a growth, stimulus is developed in the coleoptile tip, and transmitted downwards to the growth, zone. This has caused bending of the tip, towards light., The Danish plant physiologist Boysen, - Jensen (1910) cut off the colepotile and, inserted thin plate of gelatin beween the, tip and the cut stump. He observed that, coleoptiles tip still bends towards unilateral, light., Paal (1919) cut off the tip of colepotile, and replaced it asymmetrically on the, cut coleoptile stump. He observed that, the colepotile tip bent away from the side, bearing tip even in dark., F.W. Went (1928) successfully isolated, natural auxin from Avena coleoptile tips., He cut off the tip and placed them on small, agar blocks. Then after certain period of, time placed the agar blocks asymmetrically, on cut coleoptile stump that caused bending., He demonstrated the presence of substance, which could diffuse into agar blocks. Went, named this substance as auxin., , coleoptile bends, , top of coleoptile, removed (no, bending), , light-proof, cap on tip (no, bending), Darwin, , tip removed tip removed coleoptile tips, on agar, , tip placed on tips removed,, agar cut into, one side, blocks, , gelatine, inserted, , bends, towards, light, , bending in agar block placed, absence of on one side and, light, bending occurs, , Boysen-Jensen, , Paal, , Went, , According to Thimann and Pincus (1948), “Plant hormones are organic substances, produced naturally in higher plants affecting, growth or other physiological functions at a site, remote from its place of production and active, in very minute (optimum) amount”. Hormones, are transported through phloem parenchyma, (Phillips 1971)., a. Auxins (Auxien = to grow):, F. W. Went in 1931, used this term first., Auxin was isolated from urine of a person, suffering from Pellagra (Kogl and H. Smit, 1931). In plants, it is synthesized in growing, tips or meristematic regions of plants from, where it is transported to other plant parts. The, most common and important natural auxin is, Indole-3-acetic acid (IAA). Tryptophan is the, primary precursor of IAA in plants. It is the, first hormone to be discovered in plants and, is primarily responsible for cell elongation. It, shows polar transport - Basipetal transport in, stem. Now synthetic auxins like IBA (Indole, butric acid), NAA (Naphthalene acetic acid),, 2, 4-D pichloro (Phenoxy acetic acid), etc. are, used., Physiological effects and applications of, auxin:, The primary effect is cell enlargment. In, most of the higher plants, growing apical bud, inhibits the growth of lateral buds. This is called, as apical dominance. Auxin stimulates growth, of stem and root. Auxin induces multiplication, of cells, hence used in tissue culture experiments, to produce callus. It stimulates formation, of lateral and adventitious roots. These are, marketed as synthyetic herbicides. e.g. 2, 4-D, (2,4 dichlorophenoxy acetic acid). It kills dicot, weeds without affecting monocot crop plants., The seedless fruits like orange, lemon,, grapes, banana etc. are produced by application, of auxin (i.e. induced parthenocarpy). Auxins, promote cell division in cambium and also cause, early differentiation of xylem and phloem. It, 139
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promotes root elongation in low concentration, and shooting at higher concentration. It, also hastens early rooting in propagation by, ‘cutting’., Foliar spray of NAA and 2,4-D induces, flowering in litchi and pineapple. Likewise, it, prevents premature fruit drop in apples, pear, and oranges, and also prevents formation, of abscission layer. Auxins play a role in, elongation of cell. It is known to increase rate, of respiration. Auxins break dormancy in seed, and promote quick germination., Do you know ?, Agent orange : Mixture of two phenoxy, herbicides in easter form. 2, 4-D and 2,4, 5-T, (dioxin) is known as agent orange used in, Vietnam war for defoliation of forests., b. Gibberellins :, It is another growth promoting hormone, and is abundant in root tip and developing, seeds. It shows non-polar transport through, vascular tissue., Gibberellins were first isolated from the, fungus Gibberella fujikuroi by Japanese scientist, Kurosawa (1926). He observed that when, rice plant was infected by fungus Gibberella, fujikuroi, it shows extensive stem elongation, called‘bakane disease’. The crystalline form, of Gibberellins were isolated by Yabuta and, Sumiki (1938) from the fungus culture. They, named it as gibberellin. It is synthesized in, young leaves, seeds, roots and stem tips. These, are synthesized from mevalonic acid. More, than 150 chemical types are known so far., GA3 is most common and biologically active, form. Chemically it contains a gibbeane ring a cyclic diterpene with four isoprene units., Physiological effects and application of, Gibberellins :, Dormancy of bud can be broken by, gibberellin treatment. It can promote seed, germination in cereals like barley and wheat, , by synthesizing hydrolysing enzyme amylase, to produce sugar. The most striking effect of, it, is the elongation of stem where internodes, increase in length. It also promotes bolting i.e., elongation of internodes just prior to flowering, in plants those with rosette habit e.g. beet,, cabbage. It causes parthenocarpy in tomato,, apple and pear, and flowering in long day, plants. It is used to increase the fruit size and, bunch length of grapes. When gibberellins, are applied on genetically dwarf plants, like maize, the stem rapidly elongates and, acquires the height of normal tall varities of, maize. Application of gibberellins overcomes, the requirement of vernalization. Usually, it, inhibits growth of root, delays senescence and, prevents abscission. It also breaks dormancy of, seed and hastens germination. Application of, gibberellin causes production of male flowers, on female plant., c. Cytokinin :, It is another growth hormone that promotes, cell division. Letham coined the term cytokinin., The first cytokinin was discovered by Skoog, and Miller (1954) during investigation of, nutritional requirements of callus, tissue, culture of Nicotiana tabacum (Tobacco).They, observed that the callus proliferated when, the nutrient medium was supplemented with, coconut milk and degraded sample of DNA, (obtained from herring sperm). They named, it as kinetin. Chemically kinins are 6-furfuryl, amino purine. First natural cytokinin was, obtained from unripe maize grains by Letham, et al. It is known as Zeatin. 6-benzyl adenine is, a synthetic cytokinin hormone. Seven different, types of cytokinins are recorded from plants., Natural cytokinins are also reported from, plants like Banana flowers, apple and tomato, fruits, coconut milk, etc., Physiological effects and applications of, cytokinin :, Besides cell division, it also promotes cell, enlargment. High cytokinin promotes shooting., , 140
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A low ratio of cytokinin to auxin induces root, development but a high ratio causes buds and, shoot to develop. Cytokinin and auxin ratio, and their interactions controls morphogenic, differentiation. It promotes the growth of, lateral buds and controls apical dominance by, cell division. It delays the senescence or ageing, and abscission processes in plant organs. This, was reported by Richmond and Lang (1957)., Formation of interfasicular cambium and, expansion of cells are other functions. It also, breaks dormancy and promotes the germination, of seeds. Cytokinin reverses apical dominance, effect. It induces RNA synthesis and formation, of interfascicular cambium., d. Ethylene :, It is the only gaseous growth regulator., Denny (1924) reported ethylene is effective, in fruit ripening. Gane (1934) established that, plants naturally synthesize ethylene. Crocker, (1930) proposed that ethylene is the plant, hormone responsible for fruit ripening. It is a, simple gaseous hydrocarbon with essential, role in the fruit ripening. The most widely used, compound as a source of ethylene is ethephon., It is synthesized in roots, shoot apical meristem,, ripening fruits etc., Do you know ?, Ethret / Ethephon is a 2-chloroethyl, Phosphoric acid, which releases ethylene, after dissolving in water., Physiological effects and application of, ethylene :, It promotes ripening of fruits like bananas,, apples and mangoes. It stimulates initiation of, lateral roots in plants and breaks the dormancy, of bud and seed., It accelerates the abscission activity, in leaves, flowers and fruits by forming of, abscission layer. Ethylene inhibits the growth, of lateral buds and causes apical dominance, and retards flowering. It is associated with, , the enhancement of process of senescence of, plants organs. It inhibits flowering in most of, the plants except pineapple. It causes epinasty, (drooping) of leaves and flowers. It increases, activity of chlorophyllase enzyme causing, degreening effect in banana and Citrus fruits., Internet my friend, Degreening: It is the process of decomposition, of green pigment in fruits usually by applying, ethylene. This method is called trickle, degreening. Collect more information about, degreening., e. Abscissic Acid :, It is a natural growth inhibiting hormone., Carns and Addicott (1961-65) observed that the, shedding of cotton balls was due to a chemical, substance abscisin I and II. Wareing (1963), isolated a substance from buds of Acer that can, induce bud dormancy and named it dormin., These two identical chemical substances were, given the common name abscissic acid. It is, synthesized in leaves, fruits, roots, seeds etc., Chemically, it is a 15-carbon sesquiterpenoid, and is synthsized from mevalonic acid., Physiological effects and application of ABA:, It promotes abscission of leaves and induces, dormancy in many plants. It controls the, dormancy in buds and seeds by inhibiting, growth processes. It accelerates the senescence, of leaves, flowers and fruits. It inhibits and, delays cell division and cell elongation and, suppresses cambium activity by inhibiting, mitosis in vascular cambium. ABA could cause, efflux of k+ ions from the guard cells and, result in closure of stomata. So, it is known as, an antitranspirant. It acts as a stress hormone, by inducing the plant to bear the adverse, environmental conditions. It inhibits flowering, in long day plants but stimulates flowering in, short day plants., , 141
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the flowering behaviour in plants - Soyabean, and Meryland mamoth variety of tobacco., They found that soyabean plant flowers during, late summer and tobacco variety during winter,, irrespective of their germination and growing, season. They studied effects of different, temperatures, nutrition, soil moisture, etc. in, respect of flowering. None of these were found, to regulate flowering. However, experimentally, they found that the exposure to specific duration, of light (i.e. photoperiod) had profound, influence on flowering. They examined the, effect of day length on flowering by using, artificial illumination. They concluded that, the relative length of the day was most crucial, in the growth and development of flowers to, which they coined the term photoperiodism., Based on the photoperiodic response, plants, were classified in three categories viz, Short, Day Plants (SDP), Long Day Plants (LDP), and Day Neutral Plants (DNP)., , Do you know ?, Bioassays for :, Auxins - Avena curvature test., Gibberellins - Alpha amylase bioassay., Cytokinins - Chlorophyll retention test., Ethylene - Tripple pea test., ABA - Inhibition of alpha amylase test., Internet my friend, Collect information of synthetic plant, hormones., Can you tell?, 1., 2., 3., 4., , Why is auxin called a growth regulator?, Effect of Gibberellin application on apple., How can we overcome apical dominance?, Which is standard bioassay method for, auxins?, 5. ABA is called as stress hormone. Why?, , 7.10 Photoperiodism :, Higher plants reproduce sexually by, producing special structures called flowers., Plants exhibit transition from vegetative, growth to reproductive growth during which, flowers are produced. Like vegetative growth,, reproductive growth is also influenced by, several environmental and nutritional factors., Among the environmental factors - light, and temperature exert profound influence on, flowering. The influence of light is known as, Photoperiodism and that of temperature, is, Vernalization., Light as an environmental factor influences, germination of seed, vegetative growth,, photosynthesis, etc. Light as a factor as three, aspects viz, Quality, Intensity and Duration, of light. It is the duration of light that has, profound effect on flowering in higher plants., The term photoperiodism was used by, Garner and Allard (1920). They were studying, , Do you know ?, Organs for reception of photoperiodic, stimulus - Leaf is the chief organ for receiving, the photoperiodic stimulus as demonstrated by, Knoff (1934). Defoliated plants will not flower, even if the plants are exposed to proper duration, of light., Photoperiodic stimulus - It is a chemical, stimulus transported through phloem and is, called florigen which is hormonal in nature., Photochemical receptors in the leaves, are the biloproteins (pigments) located in the cell, membrane. These are called Phytochromes., Blue wavelengths of light influences, flowering., , a. Short Day Plants (SDP) :, These plants usually flower during winter, and late summer when day length is shorter than, the critical photoperiod (critical photoperiod, is that length of photoperiod above or below, which flowering occurs). These are called, , 142
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long night plants because they require long, uninterrupted dark period/ night for flowering., If dark period is interrupted even by a flash, of light, SDP will not flower. Some of the, short day plants are Dahlia, Aster, Tobacco,, Chrysanthemum, Soybean (Glycine max),, Cocklebur (Xanthium), etc., b. Long Day Plants (LDP) :, Plants that flower during summer are, called long day plants. They require longer, duration of light than the critical photoperiod,, for flowering. They are called short night, plants as they require short dark period. When, long dark period is interrupted by a brief flash, of light, LD plants can flower e.g. pea, radish,, sugar beat, cabbage, spinach, wheat, poppy,, etc., , a. Requires, a relatively, long of, uninterrupted, darkness., Light, Critical, dark period, , Phytochrome :, Hendricks and Borthwick (1952) observed, that flowering in SD plants is inhibited, if dark, period is interrupted even by a flash of red, light of 660 nm. If it is immidiately followed, by far red light (730 nm), then SD plants will, flower. This observation led them to conclude, that some pigment system in plant receives the, photoperiodic stimulus. These pigment proteins, are called phytochromes., The leaves produce light-receiving, proteinaceous pigment called phytochrome, that induces flowering. It exists in two, interconvertible forms viz, red (Pr) and far, red (Pfr). When Pfr absorbs far red light, it, is converted into Pr and vice versa. These, are located in the cell membrane of green, cells., 660nm (red), Pr, Pfr, 730nm (far red), Darkness, During day time, Pfr accumulates in, the plants. It inhibits flowering in SDP but, initiates flowering in LDP. During dark period, Pfr changes into Pr, it stimulates/ promotes, flowering in SDP and inhibits flowering in, LDP., , Flash Darkness, of light, b. Requires a, relatively small, duration of, darkness/ no, darkness at all., , Always Remember, Control of morphogenesis by light and, phytochrome, is called photomorphogenesis., , Flash of light, , Fig. 7.9 : Photoperiodism, , Internet my friend, , c. Day Neutral Plants (DNP) :, These plants flower throughout the, year round, independent of duration of light, (photoperiod). They do not require specific, photoperiod to flower. Therefore, they are, called Day neutral plants e.g. Cucumber,, tomato, cotton, sunflower, maize, balsam, etc., , Melchers proposed that chilling treatment, may induce formation of hypothetical floral, hormone, vernalin., 7.11 Vernalization (Yarovization) :, Temperature as environmental factor, influences several physiological processes, including reproduction. Temperature as a, factor has three cardinal points viz, minimum,, , 143
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optimum and maximum temperature. It is, a low temperature (chilling) treatment that, induces early flowering in plants as was, evidenced by Klippart (1918). Chouard (1960), defines vernalization as accelaration of the, ability to flower by chilling treatment. The, term vernalization was coined by T.D Lysenko, (1928) for the effect of low temperature on, flowering in plants., It is an influence of temperature on, development and flowering. Many plants, such as cereals, crucifers require a period of, cold treatment for flowering. It is the method, of inducing early flowering in the plants by, pretreatment to their seeds/ seedlings at low, temperature (1-60C for one to one and half, months’ duration). The site of vernalization is, believed to be shoot apical meristem. Generally,, vernalization is effective at seed stage in, annual plants. Vernalization stimulus is also a, chemical stimulus named as vernalin. This can, be transferred through grafting (Melcher 1939)., Know the Scientist :, The low temperature induces early, flowering which was first noticed by, Klippart (1957) while working on two, varieties of wheat- ‘winter wheat’and ‘spring, wheat’. The winter wheat sown in winter,, produces flowers in the following summer., The spring wheat sown in the spring and, produces flowers during summer. However,, if winnter variety is sown in spring does not, produce flowers during summer but does so, in the next year’s summer. He observed that, if germinated seeds of ‘winter wheat’ are, treated with low temperature, it can behave, as spring wheat. He concluded that winter, wheat requires low - temperature exposure, before the onset of flowering., The reversion of vernalization by high, temperaturetreatmentiscalleddevernalization., , Advantages of vernalization :, • Crops can be produced earlier., • Crops can be cultivated in regions where, they do not grow naturally., 7.12 Mineral nutrition :, Plant absorbs water, gases, mineral,, nutrients, etc. from surroundings. Green plants, for the synthesis of their organic food need, inorganic substances (elements) which are, obtained from soil in the form of minerals., Minerals constitute most commonly occuring, solid, inorganic materials obtained from the, earth’s crust., Chemical analysis of plant ash clearly, indicates that plant absorbs mineral elements, from surroundings (soil, air and water) for, its use. About 36 to 40 different elements of, periodic table are used as minerals by the, plants. These are absorbed in ionic (dissolved), form as PO4 , CO3 , SO4 , etc.,usually through, roots (regions of elongation and growth)., Sources of minerals :, Plants derive necessary elements from the, atmosphere, soil and water. Carbon enters the, plant as atmospheric carbon-dioxide., Source of hydrogen is water and oxygen, comes from air and water. Carbon, Hydrogen, and oxygen are not minerals in origin., Source of nitrogen is the soil. Plant derives, nitrogen from both mineral and non-mineral, origin., Classificaion of minerals :, Earlier, on the basis of their requirement, minerals were classified as essential and nonessential. Essential minerals are those that are, indispensible without which plants can not, complete their life cycle e.g. C, H, O, N, P, etc., These, elements, play, structural, and, physiological roles. Their absence can produce/, cause major deficiency symptoms. The nonessential elements are not indispensable and, they do not produce/ cause any deficiency, symptoms. This classification is absolete now., , 144
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Based on the quantity requirement, minerals, are classified as minor or microelements and, major or macroelements. Microelements are, required in traces because they function in, the catalytic role e.g. Zn, Cu, Al, Si, etc. as cofactors. Macroelements are required in large, quantity. They mainly play the nutritive and, structural roles e.g. C, H, O, P, Mg, N, K, S,, etc. C, H, O are non mineral major elements., This classification is not accepted now., Know the Scientist :, Criteria for Essentiality of elements, proposed by Arnon and Stout (1939) : The, elements must be absolutely necessary for, supporting normal growth and reproduction., These elements must be having specific, functions and should not be replaceable by, another element. The element must be directly, involved in the nutrition of the plant. If an, element satisfies all above three criteria, it is, considered to be an essential element., Do you know ?, Liebig showed the Essentiality of, mineral nutrients and put forth the ‘Law of, minimum’. According to this law, the yield of, crop plant is determined by the amount of, essential element that is present (available) in, the minimum quantity., , Symptoms of Mineral deficiency in plants :, Any visible deviation from the normal, structure and function of the plant, is called, symptom or hunger sign. The concentration, of the essential elements below which plant, growth is retarded, is termed as critical, concentration., The element is said to be deficient when, present below the critical concentration. Certain, morphological changes are indicative of the, deficiency of particular element. Deficiency, symptoms also depend on the mobility of, the elements in the plants. The deficiency, symptoms appear first in young tissues when, elements are relatively immobile e.g. sulphur,, calcium., When the elements are actively mobilized, within the plants and exported to young, developing tissues, the deficiency symptoms, are visible first in the older tissues (senescent, leaves). e.g. nitrogen, magnesium, potassium., Some important deficiency symptoms seen, in plants are:, • Stunting : The growth is retarded. The stem, appears condensed and short., • Chlorosis : It is the loss or non-development, of chlorophyll resulting in the yellowing of, leaves, • Necrosis : It is the localized death of tissue, of leaves., • Mottling : Appearance of green and nongreen patches on the leaves., • Abscission : Premature fall of flowers,, fruits and leaves., , Now a days minerals are classified on the, basis of their biochemical functions., Table : 7.10 Roles of Mineral Elements in Plants, Element, Nitrogen, NO-2or NOor NH+4, Phosporus, H2PO-4or, HPO24, , 3, , Region of plant in, which required, Everywhere, particularly in, meristematic tissues, Younger tissues,, obtains from older,, metabolically less, active cells, , Constituent of proteins, nucleic acids,, vitamins, hormones, coenzymes, ATP,, chlorophyll., , Deficiency, symptom, Stunted, growth,, chlorosis., , Constituent of cell membrane, certain, proteins, all nucleic acids and nucleotides, required for all phosphorylation reactions., , Poor growth,, leaves dull, green., , Functions, , 145
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Potassium, K+, , Helps in determining anion- cation balance, in cells involved in protein synthesis,, Meristematic tissues, involved in formation of cell memberane, buds, leaves, root tips and in opening and closing of stomta;, increases hardness; activates enzymes and, helps in maintenance of turgidity of cells., , Calcium, Ca2+, , Meristematic and, differentiating, tissues, accumulates, in older leaves, , Involved in selective permeability of cell, membranes, activates certain enzymes, required for development of stem and root, apex and as calcium pectate in the middle, lamella of the cell wall., , stunted, growth., , Magnesium, Mg2+, , Leaves, withdrawn, from ageing leaves, and exported to, developing seeds, , Activates enzymes in phosphate, metabolism, constituent of chlorophyll,, maintains ribosome structure., , Chlorosis, , Sulphur, SO42-, , Stem and root, tips; young leaves, remobilised during, senescence, , Constitutent of certain proteins, vitamins, (thaimine, biotin CoA) and Ferredoxin., , Chlorosis, , Iron, Fe3+, , Everywhere carries, along leaf veins., , Constituents of ferredoxin and cytochrome,, activates catalase required for synthesis of Chlorosis, chlorophyll., , Yellow edges, to leaves,, premature, death., , Manganese, (trace), Mn2+, , Leaves and seeds, , Activates certain enzymes (carboxylases), , Chlorosis,, grey spots on, leaves., , Molybdenum, (Trace), MoO 2+, , Everywhere, MO3+, particularly in roots, , Activates certain enzymes in the nitrogen, metabolism., , Slight, retardation of, growth., , Boron (trace), 2BO3-3or B O, 4 7, , Leaves and seeds, , Required for uptake and utilisation of Ca2+,, Brown heart, pollen germination and cell differentiation,, disease., carbohydrate translocation., , Copper (trace), Cu2+, , Everywhere, , Activates certain enzymes., , Die-back of, shoots., , Everywhere, , Activates various enzymes especially, carboxylases, part of carbonic anhydrase, and various dehydrogenases needed for, auxin synthesis, , Malfomred, leaves, , Everywhere, , With Na+ and K+ helps to determine solute, concentration and anion-cation balance, in cells, essential for oxygen evolution in, photosynthesis., , Poor growth, of the plant, , 2, , Zinc (trace), Zn2+, , Chlorine, Cl-, , 146
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Minerals salt absorption :, Most minerals in the soil are charged, particles hence, they can not pass across cell, membrane. Hence most of the minerals are, absorbed actively with the expenditure energy., Minerals can also be absorbed passively, without expenditure of energy. Mineral ion, absorption is independent of water absorption., Mineral ion absorption can occur in two, ways :, a. Passive Absorption : Movement of, mineral ions into the root occurs by diffusion., Molecules or ions diffuse from a region of, their higher concentration to a region of their, lower concentration. The movement of mineral, ions into root cells as a result of diffusion is, without expenditure of energy is called passive, absorption. Passive absorption can take place, by direct ion-exchange, in direct ion-exchange, mass flow and Donnan equilibrium., , Do you know ?, • Constituents of protoplasm and cell, walls : C,H,O,N,P,S are important and, permanent constituents of the protoplasm, and the cell wall., • Osmotic potential : The osmotic pressure, of cell is the result of mineral salts and, organic compounds dissolved in the cell, sap., • Catalytic functions : Many elements, like Fe, Cu, Zn, Mg, Mn, Cl, etc. act as, catalysts in various enzyme reaction of, plant metabolism., • Permeability of cytoplasmic membrane:, Permeability of membrane is influenced, by the presence of the various ‘cations’, and ‘anions’ of the mineral elements in the, external medium like ca+, k+., • Components of energy related chemical, compounds : Phosphorus in ATP and Mg, in chlorophyll., , b. Donnan equilibrium : It is based on the, assumption that certain negatively charged, ions, after their entry into the cell, become, fixed on the inner side of the cell membrane, and can not diffuse outside through the cell, membrane. Therefore, additional mobile, cations are required to balance these fixed, anions. Obviously concentration of cations, become more due to accumulation. This kind, of passive absorption of anions/ cations from, cell exterior against their own concentration, gradient in order to neutralize the effect of, cations/ anions, is called Donnan equilibrium., , Do you know ?, The atmospheric CO2 is virtually, the only source of carbon, which is the basic, constituent of all the organic compounds., Internet my friend, •, , Collect information about hydroponics, and find its use in kitchen garden., , •, , Collect information on Aeroponics., , Toxicity of Micronutrients :, Mineral ion concentration which reduces, the dry weight of tissues by 10%, is considered, as toxic. Toxicity of one element may inhibit, the uptake of the other e.g. Mn competes with, Fe, Mg for uptake, but inhibits Ca translocation, to shoot apex. Thus, Mn toxicity develops, deficiency symptoms of Ca, Mg and Fe., , Active Absorption: Uptake of mineral ions, against concentration gradient, is called, active absorption, such movement requires an, expenditure of energy by the absorbing cell., This energy is derived from respiration and, is supplied through ATP. When the roots are, deprived of oxygen, they show a sudden drop, in active absorption of minerals. The mineral, ions accumulated in the root hair pass into the, cortex and finally reach the xylem., , 147
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The minerals in the xylem are then carried, along with water to other parts of the plant along, the transpiration stream and are subsequently, assimilated into organic molecules and then, redistributed to other parts of the plant through, the phloem., Do you know ?, To explain active absorption of minerals, Hoagland and Davis (1923) put forth Carrier, hypothesis. Specific proteins in the membrane, of root cells actively pump ions into the, cytoplasm of epidermal cells of root. These, proteins are called carriers that pump both, cations and anions from the soil. According to, Bennet and Clarke (1956) protein conjugated, with lecithin acts as carrier., 7.13 Nitrogen cycle:, It is series of natural processes by which, Nitrogen enters successively from air to, organisms through soil and back to environment., Plants use photosynthetic product, the sugars to, make proteins. To do this, they need nitrogen., Unfortunately, it is very innert (nonreactive)., Plants need nitrogen in a reactive form usually, as nitrate ions., , Nitrogen is a limiting nutrient in the, agricultural ecosystems. It exists as nitrogen, atoms with a strong triple covalent bond, (N ≡ N). A regular supply of nitrogen to the, plants is maintained through biological and, physical process., Nitrogen fixation :, Atmosphere is the source of nitrogen. It, can not be used directly. It combines with C,, H, N and O to form compounds before being, used. Conversion of free nitrogen (N2) of the, atmosphere into nitrogenous salts to make, it available for the plants, is called nitrogen, fixation. It is of two types : Physical and, Biological fixation., , Atm. N2, Non biological, nitrogen fixation, Biological nitrogen, fixation, Dentrifying, Nitrates in the soil Commercial, fertilisers in, bacteria in soil, soil, NH3 in plants, Nitrates, nitrites, in the soil, , Amino acids, in plants, , Nitrifying bacteria, in the soil, NH3 in soil, Ammonifying, bacteria in the soil, Combustion, , Death, , Plant proteins, Food, Animals, Excreta Death, , Nitrogenous organic, matter in soil, , Fig. 7.11 Nitrogen cycle, 148, , Physical Nitrogen fixation: It occurs in, several steps and starts with combination of, atmospheric nitrogen with oxygen under the, influence of electric discharge and thunder, storm produce nitric oxide., Electric discharge, N2 + O2, 2 NO, Nitrogen oxygen Thunder storm Nitric oxide, The nitric oxide is then oxidized to nitrogen, peroxide in the presence of oxygen., Oxidation, 2NO + O2, 2NO2, Nitrogen peroxide, During rains, the nitrogen peroxide combines, with rain water to form nitrous acid and nitric, acid which come to ground along with rains., 2NO2 + Rain water, , HNO2 + HNO3, Nitrous Acid Nitric Acid, On ground, the alkali radicals of soil react, with nitric acid to produce nitrites and, nitrates.(absorbable form), HNO3 + Ca or K salts, Ca or K nitrates, Industrial nitrogen fixation. It occurs by HaberBosch nitrate process at high temperature and, pressure., 4500c, N2 + 3H2, 2NH3, Ammonia, 200 atm, Ammonia is then converted to urea as it is, less toxic.
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Symbiotic N2 fixation :, The best known nitrogen fixing symbiotic, bacterium is Rhizobium. This soil living/, dwelling bacterium forms root nodules in plants, belonging to family Fabaceae e.g. beans, gram,, groundnut etc., , Internet my friend, Enlist names of symbiotic and free living, nitrogen fixing bacteria., Always Remember, Today nearly 80% of nitrogen found, in human tissues originate from the HaberBosch process., Biological Nitrogen fixation : It is carried out, by prokaryotes called as ‘Nitrogen fixers’ or, Diazotrophs’. It accounts nearly 70% of natural, nitrogen fixation. Nitrogen fixers are either, symbiotic or free living. The cyanobacteria fix, significant amount of nitrogen in specialized, cells called heterocysts., Nitrogen fixation is high energy requiring, process and nitrogen fixers use 16 molecules of, ATP to fix each molecule of nitrogen to form, ammonia., N, + 8H+ +8e- + 16ATP, 2, , 2NH, +H2 +, 3, 16ADP + 16Pi, , Ammonia is then converted into amino acids., Nitrification :, Most of the soil bacteria participate in, converting ammonia into nitrate, the form, of nitrogen which can be used by plants and, animals. This involves two steps performed by, two different types of bacteria., First a soil bacteria convert ammonia into, nitrogen-di-oxide (nitrite) eg. Nitrosomonas,, Nitrosococcus, etc., 2NH + 3O, 3, , 2, , Nitrosomonas, Nitrosococcus, , 2HNO2 + 2 H2O, , Microbial, decomposition, , 2HNO 3, , These bacteria are chemoautotrophs. By, metabolizing nitrogen along with oxygen, they, obtain energy to power their own life processes., , amino acids, , Amino acids, , NH3 + ROH, Ammonia organic acid, Nitrogen assimilation :, In soil, nitrogen is present as nitrates,, nitrites and ammonia (NH 4+). It is obsorbed by, the green plants and converted to nitrogenous, organic compounds like amino acids, DNA,, etc. This is known as nitrogen assimilation., From plants, nitrogen as biomolecules like, amino acids, enters food chain and moves to, animals and then to decomposers through the, death of animals., Nitrates are first converted to ammonia, but it is highly toxic and immediately used, for conversion into amino acids, which are, then transported to other parts of the plants for, synthesis of proteins., NO - + 2e- + 2H+, NO - + H O, 3, , nitrate., Nitrobacter, , Proteins, , NO - +8e- + 8H+, , Then another type of soil bacterium called, Nitrobacter adds a third oxygen atoms to create, 2HNO2 + O2, , Ammonification :, After the death of plants and animals,, various fungi, actinomycetes and some, ammonifying bacteria decompose the tissues, and convert organic nitrogen into amino, acid and then to ammonia and back into the, ecosystem. Ammonia (NH4 +) is now available, for uptake by plants and other micro-organisms, for growth., , 2, , 2, , 2, , NH + + 2H O, 4, , 2, , Amino Acid synthesis :, Amino acids are building blocks of proteins., The amino acids are synthesized through :, Reductive amination : Ammonia reacts with, alpha ketoglutaric acid to form glutamic acid, (glutamate)., , 149
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α Ketoglutaric acid + NH 4+ NADPH 2, Glutamate dehydrogenase, Glutamate +, H2O+ NADP, Transamination : Amino group of one amino, acid (-CHNH2) is transfered to keto position (CO) of other carboxylic acid., Glutamic acid + oxaloacetic acid, Glutamate aspertate, , α - Ketoglutaric acid +, Aspartic acid, , Aminotransferase, , Amides :, Ammonia may be absorbed by amino, acid to produce amides. The process is called, amidation. The amides are the amino acids, having two amino groups. Extra amino group is, attached to acidic group (-COOH) in presence, of ATP., Glutamic acid + NH ++ ATP, alpha, 4, , glutamine + ADP, Aspartic acid + NH4++ ATP, , Aspargine, + ADP, , Amides like asparagine and glutamine, are formed from glutamic acid and aspartic, acid respectively by addition of another amino, group to each. Amides are transported to other, parts of plants via xylem vessels., Denitrification :, It is the process in which anaerobic bacteria, can convert soil nitrates back into nitrogen gas., Denitrifying bacteria removes fixed nitrogen, i.e. nitrates from the ecosystem and return it to, the atmosphere in inert form., Denitrifying bacteria includes Bacillus, spp., Paracoccus spp. and Pseudomonas, denitrificans. They transform nitrates to nitrous, and nitric oxides and ultimately to gaseous, nitrogen., 2NO3, , 2NO2, , 2NO, , N2, , Sedimentation : Nitrates of the soil are washed, away to the sea or leached deep into the earth, along with percolating water., , Do you know ?, 1. Soil nitrogen is replenished by excretion of animals, (as ammonia, urea and uric acid), ammonification and nitrification., 2. Plastids contain nitrite reductase which reduces it to ammonia., , Activity :, Label the following diagrams and identify the types of germination., , 150
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Exercise, Q. 1 Multiple choice questions., 1. Which of the hormones can replace, vernalization?, a. Auxin, b. Cytokinin, c. Gibberellins, d. Ethylene, , 8. Essential macroelements are ............, a. manufactured during photosynthesis, b. produced by enzymes, c. absorbed from soil, d. produced by growth hormones, 9. Function of Zinc is ................, a. closing of stomata, b. biosynthesis of 3-IAA, c. synthesis of chlorophyll, d. oxidation of carbohydrates, , 2. The principle pathway of water, translocation in angiosperms is .........., a. Sieve cells, b. Sieve tube elements, c. Xylem, d. Xylem and phloem, , 10. Necrosis means ..............., a. yellow spots on the leaves, b. death of tissue, c. darkening of green colour in leaves, d. wilting of leaves, , 3. Abscisic acid controls .................., a. cell division, b. leaf fall and dormancy, c. shoot elongation, d. cell elongation and wall formation, , 11. Conversion of nitrates to nitrogen is, called ....................., a. ammonification, b. nitrification, c. nitrogen fixation, d. denitrification, , 4. Which is employed for artificial, ripening of banana fruits?, a. Auxin, b. Ethylene, c. Cytokinin, d. Gibberellin, 5. Which of the following is required for, stimulation of flowering in the plants?, a. Adequate oxygen, b. Definite photoperiod, c. Adequate water, d. Water and minerals, 6. For short day plants, the critical period, is ................., a. light, b. dark/ night, c. uv rays, d. both a and c, 7. Which of the following is day neutral, plant?, a. Tomato, b. Cotton, c. Sunflower, d. Soybean, , 12. How many molecules of ATP are, required to fix one molecule of nitrogen?, a. 12, b. 20, c. 6, d. 16, Q. 2 Very Short Answer Questions :, 1. Enlist the phases of growth in plants?, 2. Give the full form of IAA?, 3. What does it mean by ‘open growth’?, 4. Which is the plant stress hormone?, 5. What is denitrification?, 6. Name the bacteria responsible for, conversion of nitrite to nitrate., 7. What is role of gibberellin in rosette, plants?, 8. Define vernalization., 9. Define photoperiodism., 10. What is grand period of growth?, , 151
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Q. 3 Short Answer Questions :, 1. Write a short note on :, a. Differentiation b. Redifferentiation, 2. Differentiate between Arithmetic and, Geometric growth., 3. Enlist the role and deficiency symptoms, of :, a. Nitrogen b. Phosphorus c. Potassium, 4. What is short day plant? Give any two, examples., 5. What is vernalization? Give its, significance., , Q. 4 Long Answer Questions :, 1. Explain sigmoid growth curve with the, help of diagram., 2. Describe the types of plants on the basis, of photoperiod required, with the help of, suitable examples., 3. Explain biological nitrogen fixation, with example., , Project :, 1. Grow seed in the deep tray on soil medium and study different stages of germination. Prepare, powerpoint presentation with the help of pictures/photographs of the same., 2. Prepare chart differentiating the epigeal and hypogeal germination., 3. Collect the information about the viviparous germination in plants growing along seashore., 4. Identify and label the deficiency symptoms in the given diagram., , 152
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Respiration and Circulation, , 8, Can you recall?, , 1. Definition of respiration., 2. The types of cellular respiration., 3. Why should we respire all the time?, All living organisms require energy to, carry out various life processes. The energy, that is stored in the body in the form of complex, organic compounds (potential energy) is, however not usable by the organisms unless it, is converted into usable form. This conversion, is achieved through the process of respiration., , the cells of stem, leaf and root. These air, spaces are continuous. Oxygen diffuses into, the air space through stomata (the pores on, leaves and young stems), carbon dioxide and, water vapour diffuse out. In the aerated soil,, the oxygen dissolves in the film of moisture or, water around the root tissue and enters it by, diffusion., Woody flowering plants (trees and shrubs), have an external impervious bark. Here,, gaseous exchange occurs through small pores, in the stem surface, called lenticels., , Respiration : It is a biochemical process of, oxidation of organic compounds in an orderly, manner for the liberation of chemical energy in, the form of ATP., C6H12O6 + 6O2, , Stomatal pore, Lenticels, Bark, , 6 CO2 + 6H2O + 38 ATP, , For this, the process of gaseous exchange, takes place between the organism and the, environment. The site of gaseous exchange is, called the respiratory surface., , Leaf, , Stoma, , Fig. 8.1 : Organs of gaseous exchange in, plants, Curiosity Box :, , Use your brain power, , 1. What are the main features of respiratory, surface?, 2. Which are the parts of plant help in the, process of gaseous exchange?, , What would happen if respiration take, place in one single step?, 8.1 Organs of Respiratory Exchange :, Respiratory exchange is a simple physical, process. For efficient gaseous exchange, the, respiratory surface should have the following, features :, a. It should have a large surface area., b. It should be thin, highly vascular and, permeable to allow exchange of gases., c. It should be moist., Gaseous exchange in plants :, The shape and structure of plants facilitate, gaseous exchange by diffusion. A terrestrial, flowering plant has many air spaces between, , Respiration in Animals :, As compared to plants, animals show wide, variety of respiratory surfaces or organs. The, respiratory surfaces differ in various animals., In animals, depending upon the complexity, of organization and the surrounding medium,, certain parts of the body have become, specialized into different types of respiratory, organs. In the higher animals, these respiratory, organs are also associated with a transport, system., , 153
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Organism, , Protists, Sponges, and Coelenterates, , Habitat, , Aquatic, , Flatworms like, Aquatic or, Planaria, Annelids semiquatic, (earthworm, nereis,, leech), amphibians, (frog), Insects, Terrestrial, , Arachnids like, spiders and, scorpions, Limulus, (Arthropod), Amphibian tadpoles, of frog,, salamanders and, newts, Fish, Reptiles, Birds and, Mammals, Turtles, , Respiratory, surface/, organ, Plasma, membrane, , Terrestrial, , Plasma, membrane,, general body, surface (moist, skin), Tracheal, tubes and, spiracles, Book lungs, , Aquatic, , Book gills, , Aquatic, , External gills, , Aquatic, Terrestrial, , Internal gills, Lungs, , Nasal cavity, Nostril, Mouth, , Pharynx, , Larynx, Trachea, , Left, lung, , Right main, bronchus, , Ribs, , Right lung, Diaphragm, Alveolous, , Air sac with blood, capillaries, , Fig. 8.3 : Human Respiratory system, , Underwater cloaca, , Table 8.2 : Respiratory surface/ organ in, organisms, Use your brain power, Why large animals can not carry out, respiration without the help of circulatory, system?, 8.2 Human Respiratory system:, The respiratory system brings about, inspiration, expiration and exchange of gases, in the lungs. These are then transported by, blood from the lungs to the different tissues, and parts of the body. The respiratory system, and be divided into an upper respiratory system, having external nares, nasal cavities, internal, nares, nasopharynx, nose, throat and associated, structures. The lower respiratory system refers, to the larynx, trachea, bronchi, bronchioles and, lungs., , Nose :, The nose has a pair of slit like openings, called external nares or nostrils for entry of, air into the nasal cavity. The nasal cavity is, divisible into right and left nasal chambers by, a mesethmoid cartilage. Each nasal chamber, is further divided into three regions., i. Vestibule : It is the proximal part about, the nostrils. Its skin has hair for filtering, the air and traping the dust and suspended, particles in the inhaled air., ii. Respiratory part (conditioner) : The, middle thin walled highly vascular part for, warming and moistening the inhaled air., iii. Olfactory or sensory chamber : The, uppermost part is lined by olfactory, epithelium for detection of smell., Pharynx :, It is divisible into three parts. The, nasopharynx is the uppermost part from, the nasal chamber it leads into oropharynx, (common passage for food and air). This, , 154
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continues below as the laryngopharynx., Between the nasopharynx and oropharynx, is the palate bone. The pharynx has a set of, lymphoid organs called tonsils., , Find out, •, , Larynx :, It is called voice box. It is the part of the, respiratory tract which contains vocal cords, for producing sound. The larynx extends from, the laryngopharynx and the hyoid bone to the, trachea. It is a hollow, tubular structure. Its, wall is made up of cartilage plates held by, membranes and muscles. Internally, it is lined, by a pair of folds of elastic vocal cords (true, vocal cords). Voice is produced by passage of, air between the vocal cords and modulations, created by tongue, teeth, lips and nasal cavity., The larynx opens into the layngopharynx, through a slit like opening called glottis. This, opening of the trachea or wind pipe is guarded, by a leaf like flap called epiglottis. It prevents, the entry of food into trachea., Epiglottis, , Hyoid, bone, , Thyrohyoid, membrane, , Laryngeal, prominence, (Adam’s Apple), Thyroid, cartilage, , Tracheal cartilage, , Fig. 8.4 : Larynx, Trachea (wind pipe) :, It is a long tube 10 to 12 cm in length. It runs, through the neck in front of the oesophagus and, extends into and upto the middle of thoracic, cavity. It is supported by ‘C’ shaped 16 to 20, rings of cartilage which prevent the collapse, of trachea. It is lined internally with ciliated,, pseudostratified epithelium and mucous glands, that trap the unwanted particles preventing, their entry into the lungs., , •, , Kavya underwent a surgical procedure, called Rhinoplasty. What could have been, the reason for such a surgery? On which, part of the body is it carried out?, What is the role of tonsils in our body?, How many pairs of tonsils do we have?, Do you know ?, , •, , •, , Shreyas choked while eating dinner. How, can you help him? What is the immediate, help that can be given to him?, What is a role of epiglottis?, , Bronchi :, The trachea divides into right and left, primary bronchi as it reaches the middle of, the thoracic cavity. The bronchi are supported, internally by ‘C’ shaped incomplete rings of, cartilage. The primary bronchi divide to form, secondary and tertiary bronchi which lead into, terminal bronchioles ending into alveoli., Lungs :, These are the main respiratory organs of, humans. One pair of spongy and elastic lungs, are present in the thoracic cavity. Each lung, is enclosed and protected by a double pleural, membrane, outer parietal and inner visceral, membrane. Between the two pleura is a pleural, cavity filled with a lubricating fluid called, pleural fluid. It is secreted by the membranes., The right lung is larger and divided into 3 lobes,, while the left lung is smaller and divided into, 2 lobes. Each lobe of the lung has the terminal, bronchioles ending in a bunch of air sacs, each, with 10 to 12 alveoli., Alveoli :, These are thin walled lobulated structures,, like a bunch of grapes. Each alveolus is, surrounded by a network of capillaries of, pulmonary artries and veins. These have, highly elastic wall made up of a single layer, , 155
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of squamous epithelium resting on a basement, membrane of connective tissue. There are, about 700 million alveoli in the lungs and, they provide the surface area for exchange of, gases., Internet my friend, 1. What is the importance of pleural fluid?, 2. Find the total surface covered by the, alveoli., Diaphragm : It is a muscular septum that, separates the thoracic and abdominal cavity. It, is dome shaped and on contraction it becomes, flattened., 8.3 Mechanism of respiration :, Respiration is a biological process, involving exchange of gases between the, atmosphere and the lungs and it results in the, formation of ATP. It includes the following, processes:, A. Breathing, B. External respiration, C. Internal respiration, D. Cellular respiration, Try This, Count the number of breaths you take, in the following situations (a). After a good, night’s sleep (b). During a vigorous activity, (running, climbing stairs etc) (c). After the, vigorous activity. Do you find any difference, in the count?, a. Inspiration, (Breathing in), , A. Breathing :, It is a physical process by which gaseous, exchange takes place between the atmosphere, and the lungs. It involves inspiration and, expiration (see fig. 8.5). Both these steps, involved parts of the thoracic cage, the ribs,, sternum and the intercostal muscles and, muscles of the diaphragm., Inspiration : During inspiration, the, atmospheric air is taken in to the lungs. It, occurs due to the pressure gradient formed, between the lungs and the atmosphere. It is, an active process in which the diaphragm, becomes flat and goes downward, the external, intercostal muscles contract so the ribs and, sternum move upward and outward. This leads, to an increase in the thoracic volume and a, decrease in pressure of thorax and the lungs., To equalize the low pressure inside the lungs,, air from the atmosphere rushes into lungs. This, is inspiration., Expiration : During expiration, the thorax, contracts causing air to be exhaled. The, diaphragm relaxes and is pushed upwards. It, becomes dome shaped. The intercostal muscles, also relax pulling the rib cage inward and, downward. This causes a decrease in thoracic, volume and leads to increase in pressure in, the thorax and the lungs as compared to the, atmospheric pressure. So air from the lungs, rushes out. This is expiration., One inspiration and one expiration is one, breath., , Air, , Air, , b. Expiration, (Breathing out), , Rib cage moves, up and forward, , Rib cage, moves down, and inward, , Pressure in lungs, decreases and air, comes rushing in., Diaphragm contracts and moves down, , Diaphragm relaxes and moves up, , Fig. 8.5 : Breathing, 156
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B. External respiration/ Exchange of gases at, the alveolar level :, An alveolus consists of a layer of simple, squamous epithelium resting on a basement, membrane. It is intimately associated with a, dense network of capillaries. The capillary wall, is also made up of simple squamous epithelium, resting on a thin basement membrane. Both, the layers have similar structure and are thin, walled. Together they make up the respiratory, membrane through which gaseous exchange, occurs i.e. between the alveolar air and the, blood., Diffusion of gases will take place from, an area of higher partial pressure to an area of, lower partial pressure until the partial pressure, in the two regions reaches equilibrium., The partial pressure of carbon-dioxide of, blood entering the pulmonary capillaries is, 45 mmHg while partial pressure of carbondioxide in alveolar air is 40 mmHg. Due to this, difference, carbon dioxide diffuses from the, capillaries into the alveolus., Similarly, partial pressure of oxygen of, blood in pulmonary capillaries is 40 mmHg, while in alveolar blood it is 104 mmHg. Due to, this difference oxygen diffuses from alveoli to, the capillaries., , Pulmonary volumes and capacities, (Normal values), Lung Volumes :, Tidal volume (T.V.) : It is the volume of air, inspired or expired during normal breathing., It is 500 ml., Inspiratory reserve volume (IRV) : The, maximum volume of air, or the extra volume, of air, that is inspired during forced breathing, in addition to T.V. Its value is 2000 to 3000ml., Expiratory reserve volume (ERV) : The, maximum volume of air that is expired during, forced breathing after normal expiration. Its, value is 1000 to 1100ml., Dead space (DS) : The volume of air that is, present in the respiratory tract (from nose to, the terminal bronchioles), but not involved in, gaseous exchange. It is 150 ml., Residual volume (RV) : The volume of air, that remains in the lungs and the dead space, even after maximum expiration. It is 1100 to, 1200ml., Lung capacities :, Total Lung capacity : The maximum amount, of air that the lungs can hold after a maximum, forcefull inspiration (5200 to 5800ml)., Vital capacity (VC) : The maximum amount, of air that can be breathed out after a, maximum inspiration. It is the some total of, TV, IRV and ERV and is 4100 to 4600ml., , blood goes, to pulmonary, vein, Alveolus, , blood from, pulmonary, artery, , Use your brain power, Capillary, , Why does gas exchange in the alveolar, region very rapid?, , Alveolar, membrane, Respiratory, membrane, , (Air) CO2, O2, , Surface, fluid, Oxygen diffuses into, red blood cells, , Carbon dioxide diffuses, into alveolus, , Fig. 8.6 : Exchange of gases between, alveolus and capillary, , C. Internal respiration :, The two main components of blood, involved in transport of the respiratory gasesCO2 and O2, are the RBCs and the plasma., i. Transport of oxygen :, Of the total oxygen transported only, 3% is transported in a dissolved state by the, plasma. The remaining 97% is bound to, the haemoglobin (Hb) present in the RBCs., , 157
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Haemoglobin acts as the respiratory carrier. It, has a high affinity for O2 and combines with, it to form oxyhaemoglobin. Theoretically, one, molecule of Hb has 4 Fe++, each of which can, pick up a molecule of oxygen (O2)., Hb + 4O2, Hb (4O2), Oxyhaemoglobin is transported from lungs, to the tissues where it readily dissociates to, release O2., Hb (4O2), Hb + 4O2, However, the degree of saturation of Hb, with O2 depends upon the O2 tension i.e. ppO2., • 100% saturation is rare., • Maximum saturation of 95 to 97% is at, ppO2 in alveoli (100 mmHg)., • Degree of saturation decreases with the, drop in ppO2. This begins the dissociation, of HbO2., • At 30 mmHg of ppO2, only 50% saturation, can be maintained., •, , Oxygen ppO2 (mm Hg), , Graph 8.7 : Oxyhaemoglobin dissociation, curve (pp = partial pressure), Carbon monoxide poisoning :, Affinity of haemoglobin for carbon, monoxide is about 250 times more, than for, oxygen. In the presence of carbon monoxide,, haemoglobin readily combines to form a, stable compound, carboxyhaemoglobin., The haemoglobin is blocked by carbon, monoxide, preventing oxygen from binding, with haemoglobin. Thus, less haemoglobin, is available for oxygen transport depriving, the cells of oxygen. This is carbon monoxide, poisoning., , The relationship between HbO2 saturation, and oxygen tension (ppO2) is called, oxygen dissociation curve. This oxygen haemoglobin dissociation curve is a sigmoid, curve and it shifts towards the right due to, - increase in H+ concentration, increase in, ppCO2 and rise in tempreature and rise in, DPG (2, 3 diphosphoglycerate), formed in, the RBCs during glycolysis. It lowers the, affinity of haemoglobin for oxygen., , Bohr effect : It is the shift of oxyhaemoglobin, dissociation curve due to change in partial, pressure of CO2 in blood., Haldane effect : Oxyhaemoglobin functions, as an acid. It decreases pH of blood. Due to, increase in the number of H+ ions, HCO3changes into H2O and CO2., In the alveoli where ppO2 is high and ppCO2, is low, oxygen binds with haemoglobin, but in, the tissues, where ppO2 is lower and ppCO2 is, high, haemoglobin does not hold as much O2., It releases O2 for diffusion into the tissue cells., , Use your brain power, While working with the car engine in, a closed garage, John suddenly felt dizzy and, fainted. What is the possible reason?, ii. Transport of CO2 :, Carbon dioxide is readily soluble in water, and is transported by RBCs and plasma in three, different forms., a. By plasma in solution form (7%) : Only, 7% of CO2 is transported in a dissolved form as, carbonic acid (which can breakdown into CO2, and H2O)., , 158, , CO2 + H2O, , H2CO3
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and bicarbonate ions recombine to form, carbonic acid and under the influence of, carbonic anhydrase yields carbon dioxide, and water., CA, CA, H+ + HCOH CO, CO + H O, 3, , 2, , 3, , 2, , 2, , c. By red blood cells (23%) : Carbon dioxide, binds with the amino group of the haemoglobin, and form a loosely bound compound, carbaminohaemoglobin. This molecule readily, decomposes in region where the partial pressure, of carbon dioxide (ppCO2) is low (alveolar, region), releasing the carbon dioxide., Hb + CO2, , neurons in the medulla (inspiratory center),, ventro lateral group of neurons in medulla, (inspiratory and expiratory center) and, pneumotaxic center located in pons (primarily, limits inspiration, slow wave sleep and rapid, eye movement sleep). Apneustic center in the, medulla is antagonistic to the neumotaxic, center. It controls non rapid eye movement, sleep and wakefullness., Brain, Breathing, control centers, , HbCO2, , Breathing, control centers, stimulated by :, , Pons, Medulla, , Use your brain power, 1. What is the role of haemoglobin in the, transport of oxygen in the blood?, 2. Write a note on chloride shift., , Nerve impulses, trigger, contraction of, muscles, , a. CO2 increase in, blood (acts directly), b. Nerve impulse, from O2 sensor, indicating O2, decrease, , Intercostal, nerves, , D. Cellular Respiration :, It is the last step taking place inside the cell, where food is oxidized and ATP is generated. It, can be shown by two steps:, , Phrenic, nerves, , a. Oxidation : Breaking down of complex, organic molecules into simple inorganic, molecules with release of heat energy., C6H12O6 + 6O2, , 6CO2 + 6H2O + 686 Kcal, , b. Phosphorylation : It involves trapping the, heat energy in the form of high energy bond of, ATP molecule. ATP is used to carry out vital life, processes and so is called as energy currency of, the cell., ADP + iP + 7.3 Kcal, ATP, 8.4 Regulation of Breathing :, Respiration is under dual control : nervous, and chemical. Human adults breathe about 12, times/minute while a new born about 44 times/, minute. Normal breathing is an involuntary, process. Steady rate of respiration is controlled, by neurons located in the pons and medulla, and are known as the respiratory centres. It, regulates the rate and depth of breathing. It, is divided into three groups : dorsal group of, , Diaphragm, Intercostal muscles, , O2 sensors, in artery, (aortic arch), , Fig. 8.10 : Regulation of Breathing, During inspiration when the lungs expand, to a critical point, the stretch receptors are, stimulated and impulses are sent along the, vagus nerves to the expiratory centre. It then, sends out inhibitory impulses to the inspiratory, center., The inspiratory muscles relax and, expiration follows. As air leaves the lungs, during expiration, the lungs are deflated and, the stretch receptors are no longer stimulated., Thus, the inspiratory centre is no longer, inhibited and a new respiration begins. These, , 160
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events are called the Hering-Breuer reflex. movements some may be reflexes, but others, The Hering-Breuer reflex controls the depth can be initiated voluntarily e.g. coughing and, and rhythm of respiration. It also prevents the yawning., lungs from inflating to the point of bursting., The respiratory centre has connections, Internet my friend, with the cerebral cortex which means we can, voluntarily change our pattern of breathing., 1. Find out information about the various, modified respiratory movements and, Voluntary control is protective because it, write it in a tabular form., enables us to prevent water or irritating gases, from entering the lungs. But the ability to stop, 2. What is the significance of such, movements?, breathing is also limited by the build up of, carbon dioxide in the blood., 8.6 Common disorders of respiratory system:, 8.5 Modified Respiratory Movements :, The given table shows a list of some, Some respiratory movements are different, from the normal movements and help express common respiratory disorders, their symptoms,, cause and treatment., emotion or clear the air passage. Of these, Table 8.11 : Common disorders of respiratory system, Disorder, , Symptoms, , Emphysema, , Breakdown, of, shortness of breath, , Chronic, bronchitis, , Coughing, shortness of breath, , Acute, bronchitis, , Inflammation, of, shortness of breath,, mucous coughed up., , Sinusitis, , Inflammation of the sinuses,, mucous discharge, , Viruses and, bacteria, , If bacterial, take antibiotics, and, decongestants,, use, vaporizer, , Laryngitis, , Inflammation of larynx, vocal, cords, sore throat, hoarseness Viruses and, of voice, mucous build up and bacteria, cough, , If bacterial, take antibiotics,, cough medicines, voice rest,, avoid irritants like smoke, , Pneumonia, , Inflammation of lungs ranging, from mild to severe, cough, and fever, shortness of breath, Bacteria, viruses, chills, sweating, chest pain,, blood in mucous, , Consult physician, immediately, antibiotics,, cough medicines, stay warm, , Asthma, , Constriction of bronchioles,, mucus build up in bronchioles,, periodic wheezing, difficulty in, breathing., , Occupational, Respiratory, Inflammation, Disordersdamage., silicosis,, asbestosis, , Cause, alveoli, Smoking, air, pollution, Smoking, air, pollution, , bronchi,, Viruses and, yellow, bacteria, , fibrosis,, , Treatment, Quit smoking, avoid polluted, air, administer oxygen to, relieve symptoms, Quit smoking, avoid polluted, air, if possible move to, warmer, drier climate, If bacterial, take antibiotics,, cough medicine, use vaporizer, , Allergy to pollen,, some foods, food Use of inhalants to open, additives, pet hair, passage ways, avoid irritants, etc., , Long term, exposure to dust, Protective mask, lung, particles silica and during work., asbestos, particles, during occupation, , 161, , and gear
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Think about it, Why is it difficult to hold one’s breath, beyond a limit?, Artificial ventilation :, It is also called artificial respiration. It is the, method of inducing breathing in a person when, natural respiration has ceased or is faltering. If, used properly and quickly, it can prevent death, due to drowning, choking, suffocation, electric, shock, etc. The process involves two main steps, : establishing and maintaining an open air, passage from the upper respiratory tract to the, lungs and force inspiration and expiration as in, mouth to mouth respiration or by mechanical, means like ventilator., Ventilator :, A ventilator is a machine that supports, breathing and is used during surgery, treatment, for serious lung diseases or other conditions, when normal breathing fails. It is mainly used, in hospitals as part of life support system., Ventilators do the following,, 1. Get oxygen into the lungs., 2. Remove carbon dioxide from the lungs., 3. Help the patient breathe., , The wastes generated within are given out into, the surrounding., Transportation in organisms and, animals occurs by diffusion and by active, transport between the cells. This mechanism is, suitable where the surface area of body is large, and the distance between parts of the body in, the organism is extremely small. Cyclosis is the, streaming movement of the cytoplasm shown by, almost all living organisms e.g. Paramoecium,, Amoeba, root hair cells of many plants and, WBCs in animals. It is for transportation, within the cell or intracellular transport. In, sponges and coelenterates the surrounding, water is circulated through the body cavities., In flat worms there is parenchymal circulation., In round worms there are no blood vessels and, the body fluid is moved around the viscera by, contraction of body wall and muscles. This is, extracellular transport., , Observe the diagram and discuss the process with your friends., Mouth, , Food, , CO2, O, 2, Blood, , Digestive, system, , Respiratory, system, Intestitial, fluid, , Heart, , , , 8.7 Transportation in living organisms :, All, living, organisms,, whether, unicellular or multicellular show an important, property of exchange of material with their, surrounding as well as between various parts, of the their cell or body., , Observe and Discuss, , Nutrients, , Circulatory, system, , Body, cells, Urinary, system, , Intestine, Anus, Unabsorbed, matter (feces), , Can you recall?, Which type of circulation is present in, cockroach? How is it different from that of, humans?, , Metabolic waste, products (urine), , Internet my friend, , Organisms take up oxygen and nutrients, from the surrounding, these are circulated, within the body for various metabolic activities., , 162, , 1. Which is type of circulation present in, amphibians and reptiles?, 2. Enlist organisms without a proper, transport system.
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Use your brain power, What is the co-relationship between, activeness of organism and complexity of, transport system?, 8.8 Circulation in animals :, In higher animals the circulation is, carried out by special fluids blood and lymph., Blood vascular system :, Higher animals from Annelida to, chordata have a special circulating fluid, the, blood which is pumped to the tissues by the, heart through the blood vessels., Types of blood vascular system :, 1. Open circulation : In animals having, an open circulation, blood is circulated, through the body cavities (haemocoels)., The visceral organs lie in the blood filled, body cavity. Exchange of material takes, place directly between blood and cells or, tissues of the body. The blood flows with, low pressure and usually does not contain, any respiratory pigment like haemoglobin,, so it does not transport respiratory gases., e.g. Arthropods (cockroach, studied in 11th, std.) and Molluscs., , 2. Closed circulation : In all the vertebrates,, higher molluscs and annelids, blood is, circulated all over the body through a, network of blood vessels. In this type of, circulation, blood flows within the blood, vessels and does not come in direct contact, with cells and body tissues. Exchange of, material between blood and body tissues is, through an intermediate fluid called lymph., Blood flows with high pressure and contains, respiratory pigments like haemoglobin for, transportation of respiratory gases., The closed circulation can be divided into, two main types : single and double circulation., Single circulation : In single circulation, the, blood passes through heart only once during, each cycle as in fishes. Deoxygenated blood, is pumped from heart towards gills, where, it undergoes oxygenation. This oxygenated, blood moves towards various body parts, gets, deoxygenated and returns back to heart for, next cycle., Gill capillaries, , Artery, , Observe and Discuss, , Gill, circulation, , Observe the, appropriate labels., , diagram, , and, , give, , Heart, , Ventricle, Atrium, Systemic, Vein, , circulation, , Systemic capillaries, , Fig. 8.12 : Single circulation, , 163
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Since, the heart of fish carries only, deoxygenated blood, it also called ‘venous, heart’., Double circulation : In double circulation,, blood passes through heart twice during each, cycle; it occurs in birds and mammals. In these, animals, heart pumps deoxygenated blood to, lungs for oxygenation and it returns to heart, as oxygenated blood. This is ‘pulmonary, circulation’. The oxygenated blood is pumped, from the heart towards various body parts, (except lungs) and returns back to the heart, as deoxygenated blood. This is ‘systemic, circulation’. Human heart shows double, circulation., Pulmonary, veins, , Heart, Right, atrium, , Lungs, , Left, atrium, , Right, Left, ventricle ventricle, , Pulmonary, artery, Pulmonary circulation, , Blood Composition and Coagulation : Study, of blood is called haematology. An average, adult has about 4 to 6 liters of blood. It is a red, coloured fluid connective tissue derived from, embryonic mesoderm. It is slightly alkaline, (pH 7.4), salty and viscous fluid. It is heaviere, then water. It has two main components- the, fluid plasma (55%) and the formed elements, i.e. blood cells (44%). These can be separated, by centrifugation., Plasma : It constitutes 55% of the blood. It is a, straw-coloured, slightly alkaline, viscous fluid, and consists of following:, Table 8.14 : Composition of plasma, , Superior and, inferior vena, cava, , Contents, , Percentage, , 1. Water, 2. Proteins (albumen, globulin,, properdin, prothrombin, fibrinogen), 3. Inorganic salts (Na, K, Mg, Ca, Fe,, Mn and Cl-, HCO- and PO3- ), , 90 %, 7 to 8 %, , 4. Others :, a. Food (glucose, amino acids, fatty, acids, triglycerides), b. Wastes (urea, uric acid and, creatinine), c. Regulators (hormones, enzymes,, vitamins), d. Anticoagulants (heparin), e. Cholesterol and antibodies, f. Dissolved gases (O2, CO2, N2), , 1 to 2 %, , 3, , Body, organs, , Dorsal, aorta, Systemic circulation, , Fig. 8.13 : Double circulation, (Diagrammatic), Internet my friend, , 1%, , 4, , Internet my friend, , 1. Find out the difference between coelom, and haemocoel?, 2. Name respiratory pigments present in, the blood of different animals., Circulatory System in Human :, The human circulatory system is composed, of blood vascular and lymphatic system., , 1. Find out the percentage and functions of, different blood proteins., 2. What is the clinical importance of, haematokrit value?, 3. Differentiate between plasma and serum., , 8.9, , Blood vascular system :, In human beings it consists of blood, heart, and blood vessels. It is responsible for various, functions like transport, homeostasis and, protection., , Formed elements :, The blood cells that are produced in the, body are collectively called formed elements., Human blood contains three types of formed, elements as red blood corpuscles (RBCs), white, blood corpuscles (WBCs) and platelets., , 164
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8.10 Red blood corpuscles / Erythrocytes :, Do you know ?, , Erythrocytes are the most abundant cells in, the human body. They are circular, biconcave, and enucleated (in camel and llama they are, nucleated)., , Each erythrocyte approximately contains, 270 million molecules of haemoglobin., Normal content of haemoglobin in blood of, men is about 14 – 17 gm% and in women, it is about 13 – 15 gm%. Condition with, less number of RBCs or less amount of, haemoglobin or both is called as anaemia., Each molecule of haemoglobin is a, protein-iron complex. It consists of four, polypeptide (globin) chains 2 alpha and 2, beta chains. An iron – porphyrin (haem), group is attached to each chain and all, four chains are bound together. Each haem, group can carry one O2 molecule and thus, one haemoglobin molecule can carry four, O2 forming oxyhaemoglobin. CO2 interacts, with amino acid residues of globin chains, and forms carbaminohaemoglobin. After, haemolysis, haemoglobin is broken down., Its globin part is broken to recycle the amino, acids. Iron of heme group is stored as ferritin, in the liver and porphyrin group of heme is, converted into green pigment biliverdin and, then into red-orange coloured bilirubin. These, pigments (mainly bilirubin) are added to bile, and finally removed out of body along with, faeces., , The red colour or RBCs is due to an oxygen, carrying pigment, the haemoglobin, in their, cytoplasm. In males, their average number, is about 5.1-5.8 million/mm3 (per μL) and in, females about 4.3-5.2 million/mm3. This is, called total RBC count. The average life span, of RBCs is 120 days. The process of formation, of RBCs is called erythropoiesis., RBCs are produced from haemocytoblasts, / reticulocytes. The erythropoeitic organ of the, foetus is the liver and spleen and in the adult,, it is mainly the red bone marrow. Vitamin, B12, folic acid and heme protein are required, for production of RBCs The old and worn out, RBCs are destroyed in the liver and spleen, (graveyard of RBCs). Condition with increase, in the number of RBCs is called polycythemia, and with decrease in number of RBCs is, called as erythrocytopenia. The hormone, erythropoietin produced by the kideny cells, stimulates the bone marrow for production of, RBCs., Mature erythrocyte is devoid of nucleus,, mitochondria or other membrane bound cell, organelles. Its cytoplasm (stroma) is rich in, haemoglobin and O2 carrying proteinaceous, pigment that gives red colour to the RBCs and, blood. It also contains an enzyme, carbonic, anhydrase., Erythrocytes are responsible for the, transport of respiratory gases O2 and CO2,, maintaining pH and viscosity of blood. They, also contribute in the process of blood clotting., The hematocrit is ratio of the volume of RBCs, to total blood volume of blood. It is different, for men and women., , Internet my friend, 1. Compare between myoglobin and, haemoglobin., 2. In the erythrocytes, nucleus and, mitochondria are absent. Explain?, White blood corpuscles / Leucocytes:, Leucocytes are colourless, nucleated and, amoeboid cells larger than RBCs.Due to their, amoeboid movement they can move out of the, capillary walls by a process called diapedesis., A normal adult has on an average, 5000-11000, WBCs per mm3 of blood. Decrease in number of, , 165, , 8.11
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WBCs (<4000) is called leucopenia (common, in HIV, AIDS and TB patients or those exposed, to radiations, shock, etc). Temporary increase in, number of WBCs is called as leucocytosis. It is, due to infection. It also occurs during pregnancy, and in newborn babies. Uncontrolled increase, in number of WBCs is a type of blood cancer, called leukemia. WBCs are mainly concerned, with defense mechanism i.e. protection., Types of WBCs :, These are colourless, irregular nucleated, cells and show polymorphism (exist in variable, forms). They can be classified into two main, types such as granulocytes and agranulocytes., , a. Neutrophils : Granules are very fine, large, in number, evenly distributed and stained, with neutral stains (dyes). Neutrophils are, about 70% of total WBCs. These cells are, spherical and nucleus is several lobed (27). These are able to perform amoeboid, movements and phagocytosis. They are, responsible for destroying pathogens by the, process of phagocytosis. ‘Pus’ is mixture of, dead neutrophils, damaged tissues and dead, microbes., Think about it, Why and when do the leucocytes perform, diapedesis?, , A. Granulocytes :, These are WBCs with a granular, cytoplasm, also called Polymorpho nuclear, leucocyte (PMN) cells. They have lobulated, nuclei in different shapes. Granulocytes are, formed from myeloid stem cells and once, formed, do not divide. Granulocytes constitute, about 72% of total WBCs. Granules are, actually secretory vesicles which contain, various secretions, enzymes, etc. Depending, upon staining property of the granules, these, granulocytes are classified into three types as, neutrophils, basophils and acidophills., Think about it, What are the granules in granulocytes?, , b. Basophils / Cyanophils : These cells have, very few granules of large size, and stain with, basic stains like methylene blue. Basophils, are non-phagocytic, small, spherical cells and, are about 0.5-1% of total WBCs.. Nucleus, is twisted. They are present in infected and, allergic conditions only. Basophils secrete, heparin, histamine and serotonin., c. Eosinophils / Acidophills : Acidophills, contain lysosomal granules that are stained, to red colour with acidic stains like eosin., Eosinophils are about 1 – 3 % of total WBCs., Nucleus is bilobed. They destroy antigenantibody complex by phagocytosis. Their, number increases in allergic condition and they, show antihistaminic property. They are also, responsible for detoxification as they produce, antitoxins., , Granules, Nucleus, , Nucleus, , a. Neutrophil, , b. Basophil, , c. Eosinophil, , d. Lymphocyte, , Fig. 8.15 : Granulocytes and Agranulocytes, 166, , e. Monocytes
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B. Agranulocytes :, Agranulocytes are about 28% of total, WBCs. Cytoplasm of these leucocytes is, without granules. They are formed from, lymphoid stem cells and can divide by mitosis., Nuclei of agranulocytes are large in size but, are not lobulated like the granulocytes. There, are two types of agranulocytes - Lymphocytes, and Monocytes., a. Lymphocytes : Lymphocytes are the, smallest of all WBCs and have a large spherical, nucleus. They constitute about 25-30% of total, WBCs. Depending upon function, two types, of lymphocytes are present as B-lymphocytes, and T-lymphocytes. B-lymphocytes mature, in bone marrow and are responsible for, antibody production/humoral immunity. It is, a highly specific antigen, antibody immunity, T-lymphocytes mature in thymus and are, responsible for cell-mediated immunity. Helper, T-cells, killer T-cell, memory T-cells and, suppressor T-cells are four main subtypes of Tlymphocytes., b. Monocytes : Monocytes are the largest of, all the WBCs. Its nucleus is large and bean, or kidney shaped. They form 3-5% of WBCs., Monocytes are actively motile and give rise, to macrophages. They are mainly phagocytic, and destroy the bacteria and dead or damaged, tissue by phagocytosis., Internet my friend, 1. What are the reasons for changes, in number of neutrophils and the, importance of complete blood count, (CBC)?, 2. Why and when are heparin, histamine, and serotonin secreted? Are these, biomolecules secreted by any other cell/, organ in our body?, , 8.12 Thrombocytes / Platelets:, Thrombocytes are cellular fragments, formed from the large cells called, megakaryocytes. These are produced in bone, marrow. They are very small, oval shaped cell, fragments without nucleus. Normal count of, thrombocytes in human blood is about 2.5 – 4.5, lakh / mm3 of blood. If number of thrombocytes, decreases than normal, condition is called as, thrombocytopenia. This condition causes, internal bleeding (haemorrhage). Platelets, secrete platelet factors which are essential, in blood clotting. They also seal the ruptured, blood vessels by formation of platelet plug/, thrombus. They secrete serotonin a local, vasoconstrictor., RBC, , WBC, Platelets, , Fig. 8.16 : Blood smear, Blood Clotting/ Coagulation of blood :, Clotting or coagulation is the process of, converting the liquid blood into a solid form., This process may be initiated by contact, of blood with any foreign surface (intrinsic, process) or with damaged tissue (extrinsic, process). Intrinsic and extrinsic processes, involve interaction of various substances called, clotting factors by a step wise or cascade, mechanism. There are in all twelve clotting, factors numbered as I to XIII (factor VI is not, in active use). Interaction of these factors in, a cascade manner leads to formation of the, enzyme thrombin. Thromboplastin, helps in, the formation of enzyme prothrombinase. This, enzyme inactivates heparin and it also converts, inactive prothrombin into its active thrombin., , 167
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Thrombin converts soluble blood proteinfibrinogen into insoluble fibrin. Fibrin forms a, mesh in which platelets and other blood cells, are trapped to form the clot. Blood clotting, occurs as shown in the following flowchart., Observe and Discuss, , (base) and conical at lower end (apex). Conical, end is slightly tilted to left side and rests above, the diaphragm., Heart is enclosed in a membranous sac, called pericardium. Pericardium is formed, of two main layers - outer fibrous and inner, serous pericardium., Heart wall, , Observe the flow chart and discuss the, process with your friends., Extrinsic Pahway, , Pericardium, , Intrinsic Pahway, Fibrous, pericardium, Parietal layer, of serous, pericardium, , Damage to the, blood vessel, , Damage to tissue, outside the vessel, Inactive, factor X, , Cascade of, clotting factors, , Tissue, Thromboplastin, , Fibrinogen, , Thrombin, Fibrin, , Myocardium, (Cardiac, muscles), Endocardium, , Pericardial, space, Visceral layer, of serous, pericardium, (Epicardium), , Activated, factor X, Prothrombin, , Trabeculae, carneae, , Blood Clot, , Fig. 8.17 : Heart wall and Pericardium, Serous pericardium is soft, moist and, elastic. It is formed of squamous epithelium and, is further divisible into two layers as parietal, and visceral layer. Parietal and visceral, layers of serous pericardium are separated by, a pericardial space. This space is filled with, pericardial fluid (about 50ml) which acts as, a shock absorber and protects the heart from, mechanical injuries. It also keeps the heart, moist and acts as lubricant., , Curiosity, 1. What is blood clotting? How and when, does it occur?, 2. What is immunity? Name its types., 3. Why does the platelet count decrease in, dengue patient?, 4. Why does our immune system fail, against pathogens like Trypanosoma and, Plasmodium?, 5. What is the relation between immunity, and organ transplantation?, 6. How do monocytes perform amoeboid, movement and phagocytosis?, 7. How do monocytes modify into, macrophages?, 8.13 Heart :, Heart is the main pumping organ of the, circulatory system. It is reddish brown in colour,, hollow, muscular organ, roughly the size of, one’s fist. Its average weight is about 300gm, in males and 250gm in females. It is conical in, shape and lies in mediastenum- i.e. the space, between two lungs. It is broader at upper end, , Heart wall :, The heart is mesodermal in origin. Its wall, is formed of three layers, outer epicardium,, middle myocardium and inner endocardium., Epicardium is thin and formed of a single, layer of flat squamous epithelium resting, on basement membrane. Myocardium is the, middle thick layer formed of cardiac muscles., Endocardium is a single thin layer formed of, squamous epithelium. The epicardium and, endocardium are protective in function whereas, myocardium is responsible for contraction and, relaxation of heart., , 168
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External structure of heart :, The human heart is four chambered., The two superior chambers are called, atria (auricles) and inferior two are called, ventricles. Externally, the atria are separated, from ventricles by a transverse groove called, coronary sulcus or atrioventricular groove., The two ventricles are externally separated, from each other by two grooves, the anterior, and posterior inter-ventricular sulci. Coronary, arteries and coronary veins run through, these sulci. Pulmonary trunk arising from, right ventricle and aorta from left ventricle, are present on anterior surface of heart. The, , pulmonary trunk bifurcates into right and left, pulmonary arteries. Aorta (systemic aorta) is, divisible into three regions as ascending aorta,, systemic arch /aortic arch and descending, aorta. The Ligamentum arteriosum joins, pulmonary trunk and aortic arch. It is the, remnant of an embryonic duct called ductus, arteriosus. The aortic arch gives out three, arteries viz. brachiocephalic (innominate), artery, left common carotid and left subclavian. The right atrium recieves superior and, inferior vena cava along its dorsal surface., Pulmonary veins open into left atrium along, the dorsal surface of heart., , Left common carotid artery, Brachiocephalic artery, , left subclavian artery, Superior vena cava, , Aorta, Right pulmonary artery, Left pulmonary artery, , Right pulmonary veins, , Left pulmonary vein, Left Atrium, Coronary sinus, , Inferior vena cava, , Left Ventricle, , Right Ventricle, , Apex of heart, , Fig. 8.18 : Posterior (dorsal) view : External structure of human heart, , Left subclavian artery, , Superior vena cava, , Aorta, Ligamentum arteriosum, Right pulmonary artery, , Left pulmonary artery, Pulmonary trunk, , Right pulmonary veins, , Left pulmonary veins, Left Atrium, Branch of left coronary, artery, Left Ventricle, , Right coronary atery, Right atrium, Coronary Sulcus, Right Ventricle, Inferior vena cava, , Fig. 8.19 : Anterior (ventral) view : External structure of human heart, 169
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Left common carotid artery, Pulmonary trunk, , Superior vena cava, Right pulmonary artery, Pulmonary semilunar valve, Opening of superior, vena cava, , Left pulmonary artery, Left pulmonary veins, Left atrium, , Right pulmonary veins, , Bicuspid (Mitral) Valve, , Right atrium, Tricuspid valve, , Chordae tendinae, Papillary muscles, , Right ventricle, , Left Ventricle, , Inferior vena cava, , Interventricular septum, , Columnae carnae, , Fig. 8.20 : Internal structure of human heart, Internal structure of heart:, Atria : These are the thin-walled receiving, chambers of heart. They are separated from, each other by inter-auricular septum. Interauricular septum has an oval depression called, fossa ovalis. It is a remnant of the embryonic, aperture called foramen ovalis., Superior vena cava (precaval), inferior, vena cava (postcaval) and coronary sinus, open into the right atrium. Opening of the, postcaval is guarded by a Eustachian valve, while the Thebesian valve guards the opening, of coronary sinus into right atrium. Four, pulmonary veins open into the left atrium., These openings are without valves., Both the atria open into the ventricles, of their respective sides by atrioventricular, apertures. These openings are guarded by, cuspid valves. The tricuspid valve is present, in the right AV aperture and bicuspid valve, (mitral valve) is present in the left AV aperture., All these heart valves help in maintaining a, unidirectional flow of blood. They also avoid, back flow of blood., Ventricles : These are inferior, thick-walled, pumping chambers of the heart. The right, and left ventricles are separated by an interventricular septum. Wall of the left ventricle is, more muscular and about 3-times thicker than, the right ventricle. Inner surface of the ventricles, , shows several ridges called columnae carnae, or trabeculae carnae which divide the lumen, of ventricle into small pockets or fissures. The, lumen of ventricles also shows inelastic fibers, called chordae tendinae. These attach the, bicuspid and tricuspid valves to the ventricular, wall (papillary muscles) and regulate their, opening and closing., The right ventricle opens into the, pulmonary aorta and left ventricle opens into, the aorta. These openings are guarded by three, semilunar valves each. These valves prevent, the backward flow of blood into the ventricles., Pumping action of heart :, The heart acts as the main pumping organ, of the circulatory system. The pumping action, is brought about by a rhythmic contraction, and relaxation of the cardiac muscles or heart, muscles. Contraction of heart muscles is systole, and relaxation of heart muscles is diastole., A single systole followed by diastole, makes one heart beat. The heart beats 70 to, 72 times per minute. This is called heart rate., During each heart beat ventricles pump about, 70 ml of blood this is called stroke volume., It means heart pumps about 72 (heart rate) x, 70 ml (stroke volume) = 5040 ml 5 liters of, blood per minute this is called cardiac output., , 170
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Right atrium, Left atrium, , Sinoatrial (SA) Node, Atrioventricular (AV) Node, Atrioventricular (AV), Bundle (Bundle of his), , Left ventricle, , Right and Left, Bundle Branches, Purkinje fibers, , Right ventricle, , Fig. 8.21 : Conducting system of human heart, Conducting tissue of heart:, The human heart is myogenic i.e. the heart, is capable of generating a cardiac contraction, independent of nervous input. It also shows, auto rhythmicity i.e. it can generate its own, rhythm by specialized muscles. A specialized, cardiac musculature called the nodal tissue is, distributed in the heart. A part of this nodal, tisse is present in the upper right corner of the, right atrium. It is called SA Node or Sinoatrial node. It lies at the base of opening of, superior vena cava. Another mass of nodal, tissue, the modified muscular fibers also called, autorhythmic fibers (conducting tissue) control, the beating rate of heart. Conducting (nodal), tissue consists of SA node, AV node, bundle of, His and Purkinje fibers., Conducting system of the heart :, SA node (sinu-atrial node) is present in, the right atrium. It acts as pacemaker of heart, because it has the power of generating a new, wave of contraction and making the pace of, contraction. SA node passes the contraction, to the left ventricle and also to the AV node., AV node (atrio-ventricular node) is present in, the right atrial wall near the base of interatrial, septum. It acts as pace setter of heart., Bundle of His/ Tawara branches start, from AV node and pass through interventricular, septum. Bundle of His forms two branches, the, right and left bundles, one for each ventricle., , These branches form network in ventricular, walls and these are called Purkinje fibers., Bundle of His and Purkinje fibers spread, impulses in ventricles. As a result both the, ventricles contract simultaneously., Do you know ?, Sometimes, valves are defective. Due to, this, abnormal or adventitious sound is heard,, called ‘heart murmuring’ or ‘hissing.’, 8.14 Working mechanism of human heart :, Cardiac Cycle :, Human heart alternately contracts and, relaxes. Contraction is called systole and, relaxation is called diastole. Atria and, ventricles contract alternately. Consecutive, systole and diastole constitutes a single, heartbeat or cardiac cycle. It is completed in, 0.8 sec. On an average, 72 beats are completed, in one minute in an adult, at rest., a. Atrial systole (AS):, Right atrium receives, deoxygenated, blood and left atrium receives oxygenated, blood. When both the atria are completely, filled with blood, pressure is exerted on the, wall. In response to this pressure, SA node, gets excited and generates cardiac impulse., Due to this, cardiac muscles in the atrial wall, contract causing atrial systole. During atrial, systole, blood is pumped into ventricles. Blood, , 171
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is prevented from going back to the veins and, coronary sinus by Eustachian and Thebesian, valve respectively. After completing systole the, atria go into diastole., In normal conditions, atrial systole is for, 0.1 sec. and atrial diastole (AD) is for 0.7 sec., b. Ventricular systole (VS):, The impulse which started from SA node, now reaches the AV node and it gets excited. AV, node sends impulses to bundle of His and from, bundle of His to Purkinje fibers. Purkinje fibers, spread impulses all over the wall of ventricles., Due to this, ventricular wall contracts causing, ventricular systole. During, ventricular, systole, right ventricle pumps deoxygenated, blood into pulmonary trunk and left ventricle, pumps oxygenated blood into aorta. During, ventricular systole the cuspid valves close both, the atrioventricular apertures preventing blood, flow into atria (lubb sound is heard)., In normal conditions, ventricular systole, lasts for 0.3 sec. and ventricular diastole (VD), lasts for 0.5 sec. During ventricular diastole,, semilunar valves are closed, preventing, backflow of blood from pulmonary trunk and, systemic aorta into ventricles (dub sound is, heard)., For about 0.4 second, both atria and, ventricles are in diastole. When all the, chambers of heart are in diastole, this condition, is called joint diastole or complete diastole., Thus, duration of one cardiac cycle is 0.8 sec., , Right side of heart contains deoxygenated, and left contains oxygenated blood. Total, volume of blood pumped during one ventricular, systole is called stroke volume (SV) and it is it, approximately 70 ml., Cardiac output (CO):, It is the volume of blood pumped out per, min. For a normal adult human being it is, calculated as follows :, , AS, VS, AS, , 0, , VD, Joint diastole, AD, , 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0, Time in sec, , Fig. 8.22 : Diagramatic representation of, cardiac cycle, 172, , (CO) = SV × HR, = 70 × 72 = 5040 ml/min, Regulation of cardiac activity :, Though human heart is myogenic,, it is also under dual control, the nervous, as well as hormonal. The nervous control, includes the part of autonomic nervous, system. Sympathetic system (with hormone, epinephrine as neurotransmitter) increase, the rate of heartbeat during emergency., Parasympathetic system (with acetylcholine, as neurotransmitter) reduces rate of, heartbeat., Nervous control includes the part, of the autonomous nervous system- its, cardiovascular center lies in the medulla, oblongata. It controls rate of heart beat in, response to inputs from various receptors like, proprio-receptors (which monitor the position, of limbs and muscles), chemoreceptors, (monitoring chemical changes in blood) and, baroreceptors (monitoring the stretching of, main arteries and veins)., Chemical control of the heart rate, includes the conditions like hypoxia,, acidosis, alkalosis causing decreased, cardiac activity, hormones like epinephrine, and norepinephrine enhance the cardiac, activity. Besides, concentration of cations, like K+, Ca++ and Na+ have major effect on, cardiac activity. Cardiac activity decreases, with the elevated blood level of K+ and Na+
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8.15 Blood vessels :, There are three main types of blood vessels, in the human circulatory system viz, arteries,, veins and capillaries., Arteries :, These blood vessels carry blood from heart, to various parts/organs of the body, there they, branch into arterioles and further into fine, capillaries. They normally carry oxygenated, blood to all parts of the body (except the, pulmonary artery which carries deoxygenated, blood). They are usually situated deep in the, body except a few like the radial, brachial,, femoral, etc. which are superficially located., In a T. S. of artery, its wall shows three layers., 1. Tunica externa or tunica adventitia, 2. Tunica media, 3. Tunica interna or intima, The outermost tunica externa is a thick,, tough layer of collagen fibers. The tunica, media is made up of smooth muscles and, elastic fibres. This thick muscular and elastic, layer makes the arterial wall pulsatile. The, innermost tunica interna is a single layer of, flat compact endothelial cells surrounding the, lumen. The angular margin around the lumen, shows tesselations. Arterial lumen is devoid of, valves and blood flows through it rapidly and, with high pressure., Tunica externa, , Lumen, , Lumen, , Tunica media, Artery, , Tunica interna, , Vein, , Lumen, Capillary, , Fig. 8.23 : T. S. of Artery, Vein and Capillary, , Veins :, Veins are thin walled, mostly superficial, vessels which carry blood from the organs, towards the heart. The capillaries around the, various organs join to form the veins. Except, for the pulmonary veins or other veins of the, body carry deoxygenated blood towards the, heart., Portal vein : A portal vein e.g. hepatic portal, vein, differs from the other normal veins in, that its starts as capillaries from one organ and, capillarises in some intermediate organ e.g., liver, before taking the blood towards the heart., Histologically, the veins also show the three, layers like in the arteries. The tunica externa,, tunica media and tunica interna. However, the, tunica media is comparitively thiner and their, lumen is wide and narrow. Internal valves at, regular intervals can be seen. Blood flows with, flow pressure and the valves prevent backflow, of blood., Capillary :, These are a network of minute blood, vessels. They are thin walled having a single, layer of flat squamous epithelium resting, on a single basement membrane. They are, mainly involved in exchange of materials., Wall of capillaries is formed of single layer, of squamous epithelium and it is stretchable., Blood flows through the capillaries under, high pressure. Wall of capillaries bear small, endothelial pores or fenestrae through which, blood cells (WBCs) can escape by the process, called as diapedesis., Pulse : It is a series of pressure waves that, travel through the arteries due to ventricular, systole. It is the strongest in arteries closer, to the heart and gradually becomes weak in, arteries away from heart. It can be felt easily in, the superficial arteries like radial artery in the, wrist and carotid artery in the neck. The pulse, can be felt at particular points on the body. All, locations where the pulse can be felt are shown, in the figure 8.27., , 173
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Facial, , Temporal, Carotid, Brachial, Radial, Femoral, , Dorsalis, pedis, , Popliteal, Posterior, tibial, , Fig. 8.24 : Pulse points, Pulse rate is equal to heart rate. Pulse rate, higher than normal (above 100 beats/min), is called tachycardia and slower pulse rate, (below 60 beats/min) than normal is called, bradycardia., Use your brain power, Why do the veins have valves?, 8.16 Blood pressure (B. P.):, The pressure exerted by blood on the wall, of the blood vessels is called blood pressure., It is measured by the sphygmomanometer. It is, usually measured from the arteries., Arterial Blood Pressure:, Pressure exerted by blood on the wall of, artery is arterial blood pressure. Pressure on, arterial wall during ventricular contraction, (systole) is systolic pressure (SP). For a normal, healthy adult the average value is 120 mmHg., Pressure on arterial wall during relaxation, of ventricles is diastolic pressure (DP). For a, normal healthy adult it is 80 mmHg., B P = SP / DP, = 120/80 mmHg, Blood pressure is normally written as 120/80, mmHg. Difference between systolic and, diastolic pressure is called pulse pressure., Normally, it is 40 mmHg., Deviations from normal blood pressure, value indicate malfunctioning of heart. It, may be due to high or low blood volume,, arterial inelasticity or hardening of arteries, , (arteriosclerosis), deposition of fats like, cholesterol in the arteries (atherosclerosis),, renal diseases and emotion induced hormonal, changes, obesity, etc. Blood pressure lower, than normal i.e. below 90/60 mmHg is called, hypotension and blood pressure higher than, normal i.e. above 140/90 mmHg is hypertension., Various factors that affect the blood pressure, are cardiac output, peripheral resistance, blood, volume, length and diameter of blood vessels,, viscosity of blood, age, gender, venous return,, sleep, emotions, exercise, anxiety, etc., Think about it, Why do obese persons are prone to, hypertension?, Normal cardiac output is 5 lit/min., Increase in cardiac output increases systolic, pressure. Peripheral resistance depends upon, the diameter of blood vessels. Decrease in, diameter of arterioles and capillaries under the, effect of vasoconstrictors like vasopressin or, ADH cause increase in peripheral resistance, and thereby increase in blood pressure. Blood, loss in accidents decreases blood volume and, thus the blood pressure. Blood pressure is, directly proportional to Viscosity of blood., Blood pressure increases with age due to, increase in inelasticity of blood vessels. Amount, of blood brought to the heart via the veins per, unit time is called the venous return and it is, directly proportional to blood pressure. Blood, pressure is also directly proportional to the total, length of the blood vessel. Blood pressure can, also be affected by vaso constriction or vaso, dilation. Females have slightly lower BP than, males her age before menopause. However, the, risk of high B. P. increases in the females after, menopause sets in., , 174, , Internet my friend, Surf the internet for video-clips of, angiography, angioplasty and by-pass, surgery. Gather more information about, these medical procedures.
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called as Korotkoff sounds. Pressure in the, cuff is further lowered till any pulsatile sound, cannot be heard due to smooth blood flow. At, this moment, pressure indicated in manometer, is diastolic pressure. An optimal blood presure, (normal) level reads 120/80 mmHg., , Think about it, 1., 1. Why the heart-recipient has to rely upon, life-time supply of immunosupressants?, 2. Why the transplanted heart beats at higher, rate than normal?, Measurement of blood pressure:, Blood pressure is measured with the help, of an instrument called sphygmomanometer., This instrument consists of inflatable rubber bag, cuff covered by a cotton cloth. It is connected, with the help of tubes to a mercury manometer, on one side and a rubber bulb on the other, side. During measurement, the person is asked, to lie in a sleeping position. The instrument, is placed at the level of heart and the cuff is, tightly wrapped around upper arm. The cuff is, inflated till the brachial artery is blocked due, to external pressure. Then pressure in the cuff, is slowly lowered till the first pulsatile sound, is heard., At this moment, pressure indicated in, manometer is systolic pressure. Sounds heard, during measurement of blood pressure are, , Hypertension :, Persistently raised blood pressure higher, than the normal is called hypertension. 140/90, mmHg is called as threshold of hypertension, and the 180/120 mmHg and higher readings, are dangerous to the health. It may damage the, heart, brain and kidneys., Under the condition of hypertension,, heart uses more energy for pumping which, causes angina pectoris- the chest pains due, to lowered blood supply to cardiac muscles, and may lead to myocardial infarction. There, are more chances of brain hemorrhage due, to hypertension as arteries in brain are less, protected by surrounding tissues as compared, to other organs. In kidney, hypertension may, cause kidney failure., Coronary Artery Disease (CAD) :- It is also, known as atherosclerosis. In this, calcium, fat, cholesterol and fibrous tissues gets deposited, in blood vessels suppling blood to the heart, muscles making the lumen narrow., Angina Pectoris :, It is the pain in the chest resulting, from a reduction in the blood supply to the, cardiac muscles because of atherosclerosis or, arteriosclerosis. It is charactarized by severe, pain and heaviness in the chest. The pain may, spread to the neck, lower jaw, left arm and, left shoulder. The pain usually results from, exertion, when there is more demand of oxygen, by the heart, but the supply does not meet the, requirement., , Fig. 8.25 : Sphygmomanometer, , Angiography :, X-ray imaging of the cardiac blood, vessels to locate the position of blockages, 175
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is called angiography. Depending upon the, degree of blockage, remedial procedures like, angioplasty or by-pass surgery are performed., In angioplasty, a stent is inserted at the site, of blockage to restore the blood supply while, in by-pass surgery, the atherosclerotic region, is by-passed with part of vein or artery taken, from any other suitable part of the body, like, hands or legs., Heart Transplant :, Replacement of severely damaged heart, by normal heart from brain-dead or recently, dead donor is called heart transplant. Heart, transplant is necessary in case of patients with, end-stage heart failure and severe coronary, arterial disease., Silent Heart Attack :, Silent heart attack, also known as silent, myocardial infarction is a type of heart attack, that lacks the general symptoms of classic heart, attack like extreme chest pain, hypertension,, shortness of breath, sweating and dizziness., Symptoms of silent heart attack are so mild, that a person often confuses it for regular, discomfort and thereby ignores it. It has been, studied that men are more affected by silent, heart attack than women., , 8.17 Electrocardiogram:, Graphical recording of electrical variations, detected at the surface of body during their, propagation through the wall of heart is, electrocardiogram (ECG). This recording, may be in the form of printout or onscreen, display. The instrument used for this recording, is the ECG machine or electrocardiograph., This instrument detects and amplifies the, signals., Various electrodes are used for recording, of signals. Four electrodes are positioned on, limbs; two on arms and two on legs. These are, limb electrodes. Six electrodes are positioned, on chest. These are chest electrodes., In a normal record, three different waves, are recognized as P-wave, QRS complex and, T-wave. P-wave is a small upward deflection, from baseline of graph. It represents the atrial, depolarization. The QRS complex starts as, a slight downward deflection from baseline,, continues as sharp and large upright wave, and ends as a downward wave. QRS complex, represents the ventricular depolarization. Twave is small, wide and upwardly elevated, wave., It, represents, the, ventricular, repolarization., Atria Ventricles, , Know the Scientist :, , +2, , Millivolts, , RR interval, , Akash Manoj, a teenager from Chennai, invented the non-invasive technique to, predict the possibility of a silent heart attack., Interestingly, he invented this technique, when he was in class-X., For his innovation, he had been invited, to the Rashtrapati Bhavan as a guest of, the President of India under the Innovation, Scholars In-Residence Programme., His innovative kit analyses the level of, FABP3 (Fatty Acid Binding Protein-3) with, the help of UV light. It is the smallest protein, in the blood., Find out more information about....., , S-T, segment, , R, , +1, , P, , T, , 0, , -1, , P-R interval, Q-T interval, = 0.16 sec, 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6, Time (sec), , Fig. 8.26 : Normal ECG, ECG helps to diagnose the abnormality, in conducting pathway, enlargement of heart, chambers, damages to cardiac muscles,, reduced blood supply to cardiac muscles and, 176
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causes of chest pain. A physicial can find out, the defect in the heart by examining the wave, pattern and the time interval betwen them., 8.18 Lymphatic System :, Lymphatic system consists of lymph,, lymphatic vessels, some organs and tissues., The word ‘lymph’ means ‘clear water’ and it, is a fluid connective tissue with almost similar, composition to the blood except RBCs, platelets, and some proteins. Fluid from intercellular, spaces of the body tissue enters into the, lymphatic vessels, from here it is discharged, into the blood vessels (veins) through the, thoracic duct and the right lymphatic duct., , Curiosity, 1. What is depolarization and repolarization?, 2. What is the correlation between, depolarization and repolarization as ell as, contraction and relaxation of the heart?, 3. How are the signals detected and amplified, by electrocardiograph?, 4. Who discovered ECG?, , Internet my friend, Location of lymph nodes in human body., , Tonsil, , Cervical lymph nodes, , Subclavian vein, , Red bone marrow, Thymus gland, Spleen, Axillary lymph nodes, , Inguinal lymph nodes, Thoracic duct, , Appendix, , Popliteal lymph nodes, , Fig. 8.27 : Lymphatic System, 177
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Do you know ?, Tonsils are small lymphatic nodules in pharyngeal region. Normally there are five tonsils, strategically positioned to fight against inhaled and ingested foreign substances. Inflammation, of tonsils is called as tonsillitis. It is caused due to viral or bacterial infection. Symptoms, include sore throat, fever, swollen lymph nodes, nasal congestion, difficulty in swallowing,, headache, etc. Viral tonsillitis cures naturally but bacterial tonsillitis needs antibiotic treatment., Tonsillectomy is performed in some patients who do not respond to the treatment., , Pulmonary circulation, , Systematic circulation, Lymph node, , Lymphatic capillaries, Lymphatic duct, Subclavian vein, Lymphatic, vessel, , Pulmonary blood capillaries, Veins, Arteries, , Valve, , Systemic blood capillaries, Lymph node, , Heart, , Lymphatic capillaries, , Lymph, , Arteriole, Blood capillary, Venule, , Endothlium, of lymphatic, capillary, , Blood, , Tissue cell, , Tissue cell, , Blood, , Intestitial fluid, , Lymph, Intestitial fluid, , Anchoring, filament, , Lymphatic capillaries, , Opening, a. Relationship of lymphatic capillaries to tissue cells, and blood capillaries, , b. Details of lymphatic capillary, , Fig. 8.28 : Circulation and Lymphatic System, , 178
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Activity :, 1. Prepare chart for different types of heart muscles and their functions., , 2. Differentiate between the functioning of heart in frog and human., Human Heart, , Frog Heart, , 179
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Exercise, Q. 1 Choose the correct alternatives from those, given below and complete the statements., 1. The muscular structure that separates the, thoracic and abdominal cavity is, ., a. pleura, c. trachea, , 11. Cockroach shows, circulatory system?, a. Open, c. Lymphatic, , b. diaphragm, d. epithelium, , 3., , b. Three, , c. Four, , d. Five, , b. Pharynx, d. Trachea, , 14., , 4. The maximum volume of gas that is inhale, during breathing in addition to T.V is, ., a. residual volume, c. G.R.V., , 5., , b. I.R.V., d. vital capacity, , muscles contract when the, external intercostal muscles contract, a. Internal abdominal, b. Jaw, c. Muscles in bronchial walls, d. Diaphragm, , b. Closed, d. Double, , wave in ECG represent, atrial depolarization., a. P, b. QRS complex, c. Q, d. T, , 15. The fluid seen in the intercellular spaces, in Human is, a. blood, b. lymph, c. interstitial fluid, d. water, Q. 2 Match the Respiratory surface to the, organism in which it is found., , 6. Movement of cytoplasm in unicellular, organisms is called, ., a. diffusion, b. cyclosis, c. circulation., d. thrombosis., 7. Which of the following animals do not, have closed circulation?, a. Earthworm., b. Rabbit, c. Butterfly, d. Shark, 8. Diapedesis is performed by, ., a. erythrocytes, b. thrombocytes, c. adipocytes, d. leucocytes, 9. Pacemaker of heart is, ., a. SA node, b. AV node, c. His bundle, d. Purkinje fibers, 10. Which of the following is without nucleus?, a. Red blood corpuscle b. Neutrophill, c. Basophill, d. Lymphocyte, , of, , 13. Opening of inferior vena cava is guarded, by, ., a. bicuspid valve, b. tricuspid valve, c. Eustachian valve, d. Thebesian valve, , is a sound producing organ,, a. Larynx, c. Tonsils, , kind, , 12. Diapedesis can be seen in, cell., a. RBC, b. WBC, c. Platelet, d. neuron, , 2. What is the minimum number of plasma, membrane that oxygen has to diffuse, across to pass from air in the alveolus to, haemoglobin inside a R.B.C.?, a. Two, , which, , Respiratory surface, Plasma membrane, Lungs, External gills, Internal Gills, Trachea, , Organism, Insect, Salamander, Bird, Amoeba, Fish, , Q. 3 Very short answer questions., 1. Why does trachea have ‘C’ shaped rings, of cartilage?, 2. Why is respiration in insect called direct, respiration?, 3. Why is gas exchange very rapid at, alveolar level., 4. Name the organ which prevents the, following the entry of food into the, trachea while eating., , 180
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Q 4. Short answer questions., 1. Why is it advantageous to breathe, through the nose than through the, mouth?, 2. Identify the incorrect statement and, correct it,, a. A respiratory surface area should, have a large surface area., b. A respiratory surface area should be, kept dry., c. A respiratory surface area should be, thin, may be 1mm or less., 3. Given below are the characteristics of, some modified respiratory movement., Identify them., a. Spasmodic contraction of muscles of, expiration and forceful expulsion of, air through nose and mouth., b. An inspiration followed by many, short, convulsive, expiration, accompanied by facial expression., , 4., 5., 6., 7., 8., , Write a note on blood plasma., Explain blood clotting in short., Describe pericardium., Describe valves of human heart., What is role of papillary muscles and, chordae tendinae in human heart?, 9. Explain in brief the factors affecting, blood pressure., Q. 5 Give scientific reason., 1. Closed circulation is more efficient than, open circulation., 2. Human heart is called as myogenic and, autorhythmic., 3. Person who has undergone heart, transplant needs lifetime supply of, immunosupressants., 4. Arteries are thicker than veins., 5. Left ventricle is thick than all other, chambers of heart., , 5. Intrinsic, clotting., , and extrinsic, , process, , of, , Q. 7 Long answer questions., 1. Smita was working in a garage with, the doors closed and automobiles, engine running. After some time she felt, breathless and fainted. What would be, the reason? How can she be treated?, 2. Shreyas went to a garden on a wintry, morning. When he came back, he, found it difficult to breath and started, wheezing. What could be the possible, condition and how can he be treated?, 3. Why can you feel a pulse when you, keep a finger on the wrist or neck but, not when you keep them on a vein?, 4. A man’s pulse rate is 68 and cardiac, output is 5500 cm3.Find the stroke, volume., 5. Which blood vessel of the heart will, have the maximum content of Oxygen, and why?, 6. If the duration of the atrial systole is, 0.1 sec and that of complete diastole, is 0.4 sec, then how does one cardiac, cycle complete in 0.8 sec?, 7. How is blood kept moving in the large, veins of the legs?, 8. Describe histological structure of, artery, vein and capillary., 9. What is blood pressure? How is it, measured? Explain factors affecting, blood pressure., 10. Describe human blood and give its, functions., , Q. 6 Distinguish between :, 1. Open and closed circulation., 2. Artery and vein., 3. Blood and lymph., 4. Blood capillary and lymph capillary., , Project :, • Visit pathological laboratory to study, various blood tests like Hb detection,, CBC, blood groups., • Visit hospital to study how to take ECG,, stress test, measurement of BP, etc., • Evaluation of ECG on broad basis., • Use of stethescope., •, , 181, , Differential count of WBCs.
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9, , Control and Coordination, , Can you recall?, 1. What is the need for the control and coordination in multicellular animals ?, 2. How do plants carry out control and, coordination ?, Unicellular organisms have a simple, organisation of their life processes. However, a multicellular organisation of the body, organs and organ systems required both, a, control over their life processes as well as a, coordination between the various systems in, order to maintain homeostasis of the organism., Plants and animals both show a control and, coordination mechanism. In plants this done, by sending chemical signals and brining about, various types of movements (e.g. phototropic,, chemotactic, thingmotactic, etc). Animals,, specially the higher vertebrates show a gradual, increase in the complexity of their control and, coordination by giving both electrical and, chemical singles. In this chapter now you will, study about development of nervous system, in different animal groups and details of the, system in humans., The porifera (sponges) are the most, primitive of the animal phyla., , cells form tissues, organs and systems which, must work in coordination with each other for, smooth internal functioning of the body. Also, the organism must be able to respond and, coordinate with respect to various stimuli or, changes in the external environment., In the lower animals like Hydra and, Planaria the nervous system achieves this, function, while in higher more complex, animals, it is done by two coordinating systems, - the nervous (elctrical) system and endocrine, (chemical) control system. These two systems, will be studied separately though they work in, coordination with each other., NERVOUS COORDINATION, 9.1 Nervous System in Hydra :, Hydra, a cnidarian shows the diffused, nervous system, which is the most primitive, nervous system. The cnidarians are thus the, first animal group showing true simple nervous, system. It consists of the sensory cells and the, nerve cells or neurons along with their fibres., The nerve cells are scattered or distributed, throughout the body and inter connected to, each other by synapses between their fibres to, form the nerve net. There are two nerve nets, both in the mesoglea, one connected towards, the epidermis and second towards the gastrodermis. There are sensory cells scattered in the, , Can you recall?, 1. Do sponges have tissues and organs ?, 2. Can sponges coordinate their various, functions ?, , Tentacles, , Even though there are different types of, cells in sponges for carrying out different, functions, a proper nervous system is lacking., However to bring about efficient working of, the body these multicellular animals show, division of labour among the cells. This leads to, specialization of cells for the various activities, like digestion, respiration, excretion and others., Later in the higher animals, phyla the different, 182, , Nerve net, , Fig. 9.1 : Nerve net in Hydra
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body wall and tentacles, but sense organs are, lacking. Neurons have fibres but there are no, sensory and motor nerves. The nerve impulse, shows no polarity or direction. Thus in Hydra,, activation of sensory cells can happen at any, point, and from this point impulse can be carried, through out the body in any direction, thus, bringing movements of the body or tentacles, eg. catching of prey during feeding., The diffused types of nervous system is the, first important landmark in the nervous system., It is seen in the ctenophora as well as in the, enteric system or gut wall of higher animals, including man., 9.2 Nervous System in Planaria (flatworm) :, Planaria is a flatworm belonging to the, phylum platyhelminthes. It is the most primitive, animal with a central nervous system (CNS), located on the ventral side of body. It consists, of a mass of cerebral or cephalic ganglion, appearing like an inverted U shaped brain., These lie in the anterior or head region and from, each ganglion arise nine branches towards the, outer side. Ventrally from below the ganglia, arise a pair of Ventral Nerve Cords (VNC) or, long nerve cords. These are inter connected, to eachother by transfer nerve or commissure, in a ladder like manner. The peripheral nerve, plexus arising laterally from VNC. The PNS, Eyespot, Brain, Nerve cords, , Transverse nerve, , Fig 9.2 Ladder type nervous system in, Flatworms e.g. Planaria, , include sensory cells arranged in lateral cords, in the body. A pair of photosensory structure,, the eyes are located on dorsal side of the brain., Also there are single sensory cells scattered in, the body., In the above examples of Hydra, Planaria, and the earlier studied examples of cockroach, and humans, we have seen the gradual, evolution or changes of the neural system., There is a high level of specialization in the, formation of neurons as electrically signalling, cells and also in the entire system, gradually, from a diffuse neural system to a centralized, nervous system. The expansion into a properly, organized system involving the brain, its, gradual expansion in size and functions., This has lead to centralization of various, sense organs assisting in coordinating the, internal environment with that of the external, environment. Also there evolution of a complex, networking system which efficiently transmits, signals between one part or organ of the body, and another., , Activity :, Note the changes taking place in the, internal environment of the body, when a, person goes from resting state into a state of, physical activity., 9.3 Neural tissue, The neural tissue consists primarily of two, types of cells viz the neurons and the neuroglia, or glial cells. While a nerve is bundle of axons,, the word ‘nerve’ is used for a bundle of axons, outside the CNS while inside the CNS for the, same, word ‘tract’ is used. The nerves may be, sensory or motor or mix type i.e. having both, the types - sensory and motor fibres., All these along with nervous organs make, up the nervous system of the higher animal and, bring about coordination and control of various, activities of the body. This is done through, the receptors which bring in sensory inputs, towards the central nervous system. Processing, is carried out in the CNS and then through the, , 183
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Ependymal cell, , Oligodendrocytes, , Astrocytes, , Microglia, , Satellite cells, , Schwann cells, , Fig. 9.3 : Types of Neuroglial cells, motor commands, the response is sent out. The, nerves arising from the cytons of the CNS,, travel throughout the body transmitting the, nerves impulses to or from the CNS., Curiosity Box:, Find out about the nervous system in, Earthworm., Internet my friend, 1. How many neurons are present in the, human body and specifically in the brain?, 2. Normally what percentage of cranial, capacity is used by an average human ?, 3. What is the ratio between neurons and, neuroglia ?, Neurons/Nerve cells : These are the, structural and functional units of the nervous, system. (You may recall the structure of, a neuron studied in earlier classes). Each, multipolar neuron has three parts - cyton or, cell body, dendron and axon. The cyton has, a distinct central nucleus with a nucleolus, , and neuroplasm. A clear film of cytoplasm, surrounds the nucleus around which there are, nurofibrils, Nissl’s granules and other cell, organelles Nissl’s granules are riboprotein, components. They play an important role, in the synthesis of the enzyme required for, formation of the neurotransmitter. Neurofibrils, play an important role in transmission of nerve, impulse. Dendrons are many small conical, processes arising from the cyton. These are, highly branched into fine dendrites. Nissl’s, granules and neurofibrils both can be seen, at the base of the dendrons. They transmit, message towards the cyton. Axon is a single, long, usually unbranched process arising, from the cyton at the axon hillock. It consists, of a bundle of neurofibrils. Nissl’s granules, are absent. Terminally, the axon gives out, branches called telodendrons. The axons carry, the messages away from the cytons. The axons, may give out lateral branches called collaterals., The terminal branches attach to a muscle,, gland, skin or telodendrites of another neuron., The interconnection between two neurons or, neuron with motor organ is called synapse. It is, , 184
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Table 9.4 : Types of Neuroglial cells and their functions, Location, , Cell type, , Oligodendrocytes, CNS (Central, Nervous System), , Functions, These cells have few branches and mainly form the, myelin sheath around the central axons, which form, the white matter of CNS. Myelin an isulating sheath, is made up of protein and fatty substances. It allows, quick transmission of electrical impulses., , Small sized cells with few branches. These are derived, Microglia or brain, from monocytes and act as macrophages. They go to, macrophages, the site of injury, dead neurons and cell debris in the, CNS. They mediate immune response in the CNS., Star shaped cells and the most abundant glial cells of, Astrocytes, CNS. They have varied roles in the brain, secretion, and absorption of neural transmitter and maintence of, blood-brain barrier BBB. Regulate the transmission of, electrical impulses with the brain., Form single layer of squamous or columnar, often, Ependymal cells, ciliated epithelial cells lining the ventricles or brain, cavities and central canal of spinal cord. Mainly, responsible for production and probably also for, circulation of CSF in brain ventricles and central, canal., PNS (Peripheral Schwann Cells, Nervous System), Satellite cells, , These are the most abundant glial cells of PNS. They, produce myelin sheath around medullated nerves of, PNS., They support the functions of neurons., , usually axo-dendronic or may be axo-axonic,, axo-somatic or dendro-dendronic., The cytons are generally found inside the, brain, spinal cord (CNS) and in the ganglia., Small groups of cell bodies inside the white, matter of brain are called basal nuclei. A, bundle of axons called nerve may be covered, only by neurilemma in the non-medullated, nerves while in the medullated nerves it is, covered both by medullary sheath and on the, outside by neurilemma. Conduction of impulse, by the medullated nerves is 50 times faster than, in the non-medullated nerves. The connective, tissue covering around the nerve fascicule is, called endoneurium. Few nerve fasciculi with, , endonurium are surrounded by connective, tissue, called perineurium and a still large, bundle of nerves is covered on the outer side by, epineurium. Blood is supplied to all the nerves, to provide oxygen and nutrients., Neuroglial cells :, The neuroglial cells are far greater in, number than the neurons. Most of the supporting, cells of the nervous system are derived from the, same embryonic tissue layer (ectoderm) that, produces neurons. The term neuroglia refers, to the supporting cells of the Central Nervous, System (CNS) and Peripheral Nervous System, (PNS)., , 185
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9.4 Synapse :, It is a junction between two nerve cells, with a minute gap (synaptic cleft) in between, them which allows transmission of impulse by, a neurotransmitter bridge., 1. Properties of nerve fibres :, a. Excitability/Irritability - The nerve fibres, on, account of presence of a polarised membrane,, have the ability to perceive stimulus and enter, into a state of activity., b. Conductivity - It is ability to transmit the, excitation., c. Stimulus - It is any detectable, physical,, chemical, electrical change in the external, or internal environment which brings about, excitation in a nerve/muscle/organ/organism., In order to be effective, the stimulus must have a, minimum intensity called threshold stimulus., Subliminal (weak) stimulus will have no, effect while supraliminal (strong) stimulus, will produce the same degree of impulse as the, threshold stimulus., d. Summation effect -A single subliminal, stimulus will have no effect but if many such, weak stimuli are given in quick succession,, 1, , Presynaptic neuron, , they may produce an impulse due to addition, or summation of stimuli., e. All or none law - The nerve will either, conduct the impulse along its entire length or, will not at all conduct the impulse, as in case, of subliminal or weak stimulus., f. Refractory period - It is the time interval, (about millisecond) during which a nerve fails, to respond to a second stimulus however strong, it is., g. Synaptic delay - The impulse requires about, 0.3 to 0.5 milliseconds to cross a synapse. This, time is required for release of neurotransmitter, from the axon terminal and excitation in the, dendron of the next neuron., h. Synaptic fatigue - The transmission of nerve, impulse across the synapse halts temporarily, due to exhaustion of its neurotransmitter., i. Velocity - The rate of transmission of impulse, is higher in long and thick nerves. It is higher, in homeotherms than in poikilotherms. The, velocity of transmission is higher in voluntary, fibres (100 - 120 m/second in man) as opposed, to autonomic or involuntary nerves (10-20 m/, second). Similarly it is faster in medullated, , Nerve, impulse, , 2, , Ca2+ 2+, Ca, Ca2+, Voltage-gated Ca2+, channel, Cytoplasm, , Ca2+, Synaptic end bulb, Synaptic cleft, , Synaptic, vesicles, 3, , Ca2+ Neurotransmitter, 4, , Neurotransmitter, receptor, Ligand-gated, channel closed, , Na +, , 5, , Postsynaptic neuron, , Postsynaptic, 6 potential, , Fig. 9.5 : Synaptic transmission, 186, , K+, Ligand-gated, channel open, 7 Nerve impulse
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nerve, as the impulse has to jump from one node, of Ranvier to the next. At the synapse where the, neurons communicate with one another. The, neuron carrying an impulse to the synapse is, the pre-synaptic neuron. The neuron receiving, input at the synapse is the post synaptic neuron, or generator region (gland or muscle). A, synaptic cleft or a small intercellular space lies, in between two cells having a width about 2030 nm between them. ., The process by which the impulse from, the pre-synaptic neuron is conducted to the, post-synaptic neuron or cell is called synaptic, transmission. It is a one way process carried, out by neurotransmission., 2. Types of synapses, a. Electrical synapse : In this type of synapse, gap between the neighbouring neurons is, very narrow. The synapse between such, closed neurons is mechanical. The electrical, conductive link is formed between the pre and, post synaptic neurons. At the gap junction, the, two cells are within almost 3.8 nm distance, of each other. Transmission across the gap is, faster but depends on the connection located, at the gap junctions between the two neurons., Electrical synapses are found in those places, of the body requiring fastest response as in the, defence reflexes. also they are bidirectional,, allowing transmission in either direction or, may be unidirectional., b. Chemical synapse : These are specialized, junctions through which cells of the neural, system send chemical signal to the other, neurons and to non-neuronal cells, such as, gland and muscle. Synaptic gap is larger than, that in electrical synapse and it is 20-40 nm., Achemical synapse between a motor neuron, and a muscle cell is called a neuromuscular, junction. There are three components of a, typical chemical synapse. 1. The presynaptic, terminal (mostly axonic terminal), 2. The, synaptic membrane of the post synaptic cell, (usually on the dendrite of the next neuron/, , gland cell/ muscle) and 3. The post synaptic, neuron., The impulse travels along the axon of the, pre-synaptic neuron to the axon terminal. Most, presynaptic neurons or axons have several, synaptic knobs at their ends or terminals. These, knobs have arrays of membranous sacs, called, synaptic vesicles, that contain neurotransmitter, molecules., When an impulse reaches a synaptic, knob, voltage sensitive Ca++ channels open, and calcium (Ca++) diffuses inward from the, extracellular fluid., The increased calcium concentration inside, the cells, initiates a series of events that fuse, the synaptic vesicles with the cell membrane, of presynaptic neuron, where they release their, neurotransmitters by exocytosis. Once the, neurotransmitters bind to the receptors of the, post-synaptic cell, the action is either excitatory, (turning a process on) or inhibitory (turning a, process off). This is dependent on the nature of, the neurotransmitter involved., Once theimpulse has been transferred across, the synapse, the enzyme like cholinesterase, destroys the neurotransmitter and the synapse, is ready to receive a new impulse., 9.5 Transmission of nerve impulse :, The neurons are cells with some specials, features. The cells can be excited. The, nerve impulse is a wave of bioelectrical or, electrochemical disturbances passing along a, neuron. The transmission of the nerve impulse, along the long nerve fibre/axon tube is a, result of electrical charges across the neuronal, membrane during conduction of an excitation., Each neuron has a charged cellular membrane, with a voltage which is different on the outer, and inner side of the membrane. The plasma, membrane separates the outer and inner, solutions of different chemical compounds but, having approximately the same total number, of ions. The external tissue fluid has both Na+, , 187
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and K+ but there is predominance of Na+ and, Cl-, while K+ is predominant within the fibre, or in the intracellular fluid. This condition of, a resting nerve is also called a polarised state, and it is established by maintaining an excess, of Na+ on the outerside. On the inside there is, an excess of K+ along with large negatively, charged protein molecules and nucleic acid., Some amount of Na+ and K+ is always leaks, across the membrane. The Na+/K+ pump in the, membrane actively restores the ions to their, appropriate side. Against the concentration and, electrochemical gradient, Na+ is being forced, out and K+ is being forced inside the membrane., This process is called sodium pump or Na-K, exchange pump. This active process requires, ATP energy. The difference in distribuiton of, Na+ and K+ on the two sides of the membrane, produces a potential difference of -50 to -100, millivolts (average is -70 millivolts)., This potential difference seen in a resting, nerve is thus called resting potential. (-70, millivolts) and it is mainly due to differential, permeability of the resting membrane which, is much more permeable to K+ than to Na+., This results in slightly more K+ diffusing out, than Na+ moving inside and causing slight, difference in polarity. Also ions like negatively, charged proteins and nucleic acids inside the, cell make the overall charge negative on the, inside and positive charge on the outside., The nerve membrane not only has leakage, , Generation of nerve impulse :, 1. Depolarization : The origin and maintenance, of resting potential depends on the original, perfect state. Any change or disturbance to, the membrane will cause Na+ to enter into the, membrane and lower the potential difference, (lesser than -70 millivolts). This makes the, membrane more permeable to Na+, so there will, be rapid influx of Na+. This property is peculiar, to a nerve membrane., The voltage gated Na+/K+ channels, are special in 2 ways : They can change the, potential difference of the membrane as per the, stimulus received and also the gates operate, separately and are self closing., During resting potential, both gates are, closed and resting potential is maintained., However during depolarization the Na+, gates open but not the K+ gates. This causes, Na+ to rush into the axon and bring about a, depolarisation (opposite of polarity). Extra, cellular fluid (ECF) becomes electronegative, with respect to the inner membrane which, becomes electropositive. The value of action, potential is +30 millivolts to +60 millivolts., This triggers depolarisation in the next part, while it itself starts going to repolarisation., K+, , Na+, , K+, , Na+, , channels but also has many gated channels for, Na+/K+. These are also called voltage gated, channels. These channels enable the neuron, to change it membrane potential to active, potential in response to a stimuli. The Na+/K+, gated channels are separate so transport of, both these ions is separately done. However, during resting potential, both these gates are, closed and the membrane resting potential is, , High Na+, , maintained., , High K+, , Resting, , K+, Negative organic ions, , Polarized, membrane, , Axon, , Na+, , Stimulus, applied, , Depolarised, , Excited, Axon, , K+, , Polarised, , K, , Polarised, , +, , +, , Na, , Depolarised, , K+, , Na+, , Na+ - K +, Pump, , K+ Na+, K+, Na+, , Re-polarised, , Na+, , Excited, Axon, , K+, , Fig. 9.6 : Polarisation and Depolarisation, along a nerve, 188
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2. Re-polarization : Change in the polarity, from depolarized, back to the original state is, done by the process of repolarization. It occurs, after a short interval called refractory period., The large number of Na+ on the inside causes a, drop in the permeability of membrane to Na+, and at the same time making it more permeable, to K+ ions by opening the K+ voltage gates, and slowly closing the Na+ gates. This action, is a localized activity. K+ ions passes out very, rapidly as compared to slow entry of Na+., In this period, Na+ gates are closed, K+, gates are open and Na+ - K+ pumps becomes, operational. This process of producing a wave, of stimulation → causing depolarization →, repolarization is repeated continuously upto the, end of axon terminal. It is a self propagating, process., In medullated nerves, the insulating fatty, myelin sheath prevents flow of ions between, the axoplasm and ECF. The transport pump and, gated channels can operate only in the region, of nodes of Ranvier, where myelin sheath is, absent., The action potential cannot travel as a, wave of membrane depolarization it has to, jump from node to node. This process called, saltatory conduction, is at the rate of 120, m/second. It is faster than the continuous, conduction in non-medulated fibre (50 :1)., Do you know ?, Na-K pump operates actively and by use, of carrier (for every 3 Na+ pumped out 2K+, are pumped in). It is electrogenic., Always Remember, The resting potential of axon is -70, mV. Na+- K+ Pump pumps out 3 Na+ions for, every 2 K+ ions they pump into the cell., Can you tell?, 1. Explain how is impulse transmitted, through a synapse?, 2. Describe the conduction of a nerve, impulse in the neuron., , Chart 9.7 : Steps in generation and conduction, of nerve impulse, Application of stimulus on a resting nerve, Permeability of membrane changes and it, becomes more permeable to Na+, Na+ ions diffuse into the neuron from the ECF, Number of positive ions inside axon increases, Membrane potential changes from -70 mV to, about +30 mV and this change in the membrane, potential is called action potential, Since the polarity has been reversed from, negative on outside and positive inside it is also, called depolarization (compared to ECF), Repolarisation : At the peak of action potential, (+30 mv), the Na+ channels close. K+ gates open., The membrane becomes more permeable to K+, K+ ions diffuse out of the axon, The inside of the membrane (becomes less and, less positive) becomes negative once again, Axoplasm inside becomes negatively charged, and ECF becomes positively charged respectively, , 9.6 Human Nervous System :, The nervous system in humans is well, developed and complex. It is broadly classified, into three parts. viz, CNS, PNS and ANS., 1. Central nervous system (CNS) : The brain, and spinal cord are the parts of CNS which lie, along the mid dorsal axis. Brain is enclosed, within the brain box/cranium of the skull,, whereas the spinal cord occupies the vertebral, canal of the vertebral column. Inner to these, bony coverings, are three protective membranes, called meninges. That protect the brain and, spinal cord., a. Dura mater : It is the outermost tough,, non vascular, thick and fibrous meninx and is, attached to the inner side of the cranium. It is, separated from the underlying arachnoid mater, by the subdural space, filled with a serous fluid., b. Arachnoid mater : It is the middle, thin and, non vascular layer of connective tissue having, web like appearance. It is separated from the, , 189
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oxygen to the brain. It protects the brain from, desiccation., , Can you recall?, , CSF is slightly alkaline fluid with a specific, gravity of 1.005. A total of 100 -120 cc of CSF, is present in and around the CNS., , Nervous system, Central nervous, system (CNS), , Brain, , Peripheral, nervous system, (PNS), , Spinal Cranial, cord nerves, , Autonomic, nervous system, (ANS), , Curiosity Box:, CSF is released by the pia mater. Inside, the ventricles/cavities of the brain, there is, release of CSF by the choroid plexuses and, the ependymal cells., , Spinal, nerves, Sympathetic, nervous, system, , Parasympathetic, nervous system, , Does this CSF remain enclosed inside the, ventricles ?, , Brain, Forebrain, , Hindbrain, , Midbrain, , What can be the outcome of such a, situation ?, , Cerebrum Diencephalon, , Optic, lobes, , Optic, Chiasma, , Cerebellum, , Do you know ?, , Pons Medulla, varolii oblongata, , pia mater below by a narrow subarachnoid, space filled with cerebro spinal fluid - CSF., c. Pia mater : It is the innermost delicate,, highly vascular membrane lies in close contact, with the CNS., CSF (cerebrospinal fluid) : It is lymph like, extra cellular fluid secreted by choroid plexuses, of pia mater present inner to subarachnoid, space in the ventricles of the brain within, the central canal of spinal cord. The CSF is, secreted by the pia mater, the choroid plexuses, and the ependymal cells lining the ventricles of, the brain and central canal of spinal cord. The, three openings in the roof of medulla oblogata, help in draining out the CSF from brain to the, outside. The meninges and CSF act as a shock, absorber and protect the brain and spinal cord, from mechanical injuries. It also maintains, constant pressure inside cranium. It helps in, exchange of nutrients and wastes between, blood and brain tissue. It helps in the supply of, 190, , Blood brain barrier (BBB) Keeps a check on passage of ions and large, molecules from the blood to the brain tissue., Endothelial cells lining the blood capillaries, help in this process along with the astrocytes., , Always Remember, CSF is continuously generated by the, ependymal cells lining the ventricles and, central canal and simultaneoulsy drained, out of the brain into the blood stream., CSF maintains a constant pressure inside, the cranium. The nervous tissue is without, lympatic vessels., , Think about it, During extraction of a tooth, the dentist, gives an injection of Anaesthesia to the, patient before extraction. Is the action, potential generated ? How does the local, anaesthesia work? What is the effect of pain, killer on the nervous system.
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band of nerve fibres called corpus callosum., The outer surface of cerebrum is called, Can you recall?, cerebral cortex while the deep inner part is, Label the various parts of the digram, cerebral medulla. The cerebral cortex has, and recall their functions., outer thin region composed of grey matter and, inner medulla composed of white matter., The surface of each cerebral hemisphere, is greatly folded by many convolutions or, gyri and grooves called sulci. These greately, increase total surface area for accomodation of, the vast number of nerve cells., Each cerebral hemisphere is further divided, into four main lobes by three deep sulci. These, are A. The Human brain :, The study of all aspects of the brain is Centre sulcus which demarcates frontal lobe, called encephalology. The brain can be divided from the parietal lobe., into three main parts - forebrain, midbrain and Parieto-occipital sulcus separates the parietal, from occipital lobe., hindbrain., a. Forebrain : Forebrain consists of olfactory The lateral or sylvian sulcus demarcates the, temporal lobe from the frontal and parietal, lobes, cerebrum and diencephalon., lobes, i. Olfactory lobes :, Since these three sulci are not complete,, These are highly reduced in human brain, the, lobes, are not clearly demarcated from each, and covered by cerebrum from all sides except, ventral. Each lobe consists of a olfactory other. A fifth median lobe called insula or, insular cortex is folded deep within the lateral, peduncle and olfactory bulb., sulcus., ii. Cerebrum :, The grey matter of cerebral cortex, It is a largest part of the brain, making up, about 85 % of total brain. It is divided into right mainly consists of cell bodies of billions of, and left cerebral hemisphere by means of a neurons along with non-medulated fibres and, deep median, long fissure. The two hemispheres dendrons. The white matter mainly has axons, internally connected to each other by a thick of myelinated nerves., Chart 9.8 Parts of Brain, Brain, Midbrain, Mesencephalon, , Forebrain, Prosencephalon, Cerebral, peduncles or, crura cerebri, , Corpora quadrigemina, , Cerebellum, Rhinencephalon, reduced olfactory, lobes (2), , Telencephalon, cerebrum divided, incompletely into, two cerebral, hemispheres, , Hindbrain, Rhombencephalon, Metencephalon, , Pons varolii, , Diencephalon, Epithalamus, , 191, , Thalamus, , Hypothalamus, , Myelencephalon, , Medulla, oblongata
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Do you know ?, Corpus callosum is typically seen in, mammalian brain., Corpus callosum is the largest commissure, of the brain., It has an anterior and posterior fold called, genu and splenium respectively., Why an injury to the right cerebrum, affects the functioning of the left side of body ?, Functional areas of cerebrum :, 1. Frontal lobes : They have motor area, which controls voluntary motor activities or, movements of muscles. The premotor area, is higher centre for involuntary movements, and autonomus nervous system. Association, area is for coordination between sensation, and movements. Broca’s area/motor speech, area. It translates the thoughts into speech., Expression of emotions, intelligence, willpower, memory, personality areas are located, in the frontal lobe., 2. Parietal lobes : They are mainly for, somaesthetic sensation of pain, pressure,, temperature, taste (gustatoreceptor)., 3. Temporal lobes : It contains centres for, smell (olfactory), hearing (auditory), speech, and emotions., 4. Occipital lobes : They have visual area, mainly for sense of vision., , Area of contact between temporal, parietal, and occipital lobes is centre for Wernicke’s, area or intelligence centre. It helps in the, understanding of spoken and written words., The cerebrum, thus shows all three types of, areas sensory, motor and association area., Basal nuclei or basal ganglia are grey, masses present within the white matter or, lying on the lateral sides of thalamus. The, basal ganglia or nuclei of cerebrum receive, neurotransmitters from various parts. They, help the cortex in the execution of activities, at the subconscious level e.g. writing slow or, rapid typing. Corpus striatum at the floor of, cerebrum is the largest basal nucleus., Curiosity Box:, • Find out how different functional areas of, the brain can be mapped ?, • What is EEG ? What information can be, obtained from the EEG ?, • Which are silent areas of the brain?, iii. Diencephalon :, It is the part of the forebrain that contains, the epithalamus, thalamus and hypothalamus., It lies below the corpus callosum and above, the midbrain. It encloses a single cavity termed, third ventricle/Diocoel which communicates, with the two lateral ventricles of cerebrum, through a narrow opening called foramen of, Monro., , Central sulcus, Cerebrum, Lateral ventricle, , Parieto-occipital, sulcus, , Corpus callosum, , Choroid plexus, , Thalamus, , Pineal gland, hypothalamus, Pituitary gland, Brain stem, , {, , Arbor vitae, , Mid brain, Pons varolii, Medulla oblongata, , Cerebellum, , Spinal cord, , Fig. 9.9 Sagital section of brain, 192
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The epithalamus is the thin non nervous, roof of the diencephalon. Anterioly it is fused, with the piamater to form the anterior choroid, plexus and from its dorsal wall it is connected, to pineal gland through a pineal stalk. (Pineal, gland is discussed in detail in chemical coordination). Earlier this gland was though to be, vestigeal, but later it has been found to produce, to hormone melatonin (sleep inducing hormone;, also related to reproductive behaviour). The, lateral thick walls of diencephalon form the, thalami. They mainly contain grey matter. The, habenculor commissure connects two thalami., Different parts of the brain are interconnected, by the RAS (Reticular Activating System), through the thalami. It is called relay centre as, it transmitts all sensory impulses except those, of olfactory (smell) to the cerebrum (gatekeeper, of cerebrum connecting the anterior lateral, ventricle to the iter posteriorly. The narrow, cavity of diencephalon is called IIIrd ventricle, or diocoel. It connects anteriorly to the two, lateral ventricles by a single opening called, Foramen of Monroe and posteriorly to the IVth, ventricle or metacoel through a narrow duct, of Sylvius or iter., Hypothalamus : It forms a floor of, the diencephalon. It is richly supplied with, blood vessels (Hypothalamo-hypophyseal, portal vein) helps in feed back mechanism for, hormonal control). It maintains homeostasis,, internal equilibrium of the body and, , involuntary behaviour control. Like in the, cerebrum, the hypothalamus also contains, hypothalamic nuclei in its white matter (refer, fig. 9.33 pituitary gland) with neuro-secretory, cells involved in the production of hormones, oxytocin and vasopressin., The hypothalamus is a link between the, nervous and the endocrine system. It has higher, centres for endocrine system. It regulates heart, rate, respiration, blood pressure (B.P.), body, temperature, water and electrolyte balance. It, has centres for hunger, thirst, sleep, fatique,, satiety centre, secretion of glands of stomach, and intestine. It also produces neurohormones, that stimulate the pituitary gland. A complex, neuronal circuit called the limbic system is, formed by the hypothalamus amygdala, parts, of epithalamus and thalamus, hippocampus, and other areas. It appears to be responsible, for emotional reactions, motivational drives, and memory. The floor of the hypothalamus, continues as a downward projection called, hypopyseal stalk or infundibulum which, connects it to the hypophysis (pituitary, gland) both physically and functionally by, secretion of neurotransmitters (details in, chemical coordination). The inferior surface, of hypothalamus also bears the optic chiasma, (crossing of the two optic nerves) and a pair of, mammillary bodies (unique to mammmalian, brain and responsible for recollective memory)., , Lateral ventricles, Interventricular, foramen, Third, ventricle, Cerebral aqueduct, Fourth ventricle, Coraral Plane, , Central canal, , Fig. 9.10 : Ventricles of brain, 193, , Sagittal Plane
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b. Mid brain :, It is located between diencephalon and the, pons varolli. It contains the cerebral aqueduct, or iter that connects the third and fourth, ventricles. The corpora quadrigemina are, four rounded elevations on the dorsal surface, of the mid brain. The two superior colliculi are, involved in visual reflexes and the two inferior, colliculi are relay centres for auditory reflexes, that operate when it is necessary to move the, head to hear sounds more distinctly., The mid brain also contains on its inferior, surface two thick fibrous tracks called cerebral, peduncles or crura cerebri. These tracts of, ascending and descending nerve fibres from, RAS and connect the cerebrum mid brain. Near, the centre of the mid brain is a mass of grey, matter scattered within the white matter. It is, called the red nucleus. It plays an important, role in controlling posture and muscle tone,, modifying some motor activities and motor coordination., Always Remember, Wernicke's area : It is the sensory, speech area responsible for understanding, and formulating written and spoken, language., Broca's area : It is the motor speech, area and translates thoughts into speech, and controls movement of tongue, lips and, vocal cords., c. Hind brain :, The posterior region of the brain is, called hind brain. It consists of pons varolli,, cerebellum and medulla oblongata. The pons, varolli appears as a rounded bulge on the, underside of the brain stem (brain stem consist, of mid brain, pons and medulla and continues, upto spinal cord), and contains a cross band of, nerve fibres connecting cerebrum, cerebellar, lobes, medulla oblongata and spinal cord. It, also contains several nuclei. The cerebellum is, the second largest part of the brain and consists, of two lateral hemispheres and a central vermis., It is composed of white matter with a thin layer, , of grey matter, the cortex. The white matter, intermixes with the grey matter and shows a, tree-like pattern called arbor vitae., Can you tell?, Explain - ‘‘Cerebullum is well developed, in humans’’., The surface of cerebellum shows, convolutions (gyri and sulci) a number of, nuclei lie deep within each lateral or cerebellar, hemisphere. Over 30 million neurons lie in, the cortex. Three pairs of myelinated nerve, bundles called cerebullar penduncles connect, cerebellum to the other parts of CNS. It is an, important centre which maintains equilibrium, of body, posture, balancing orientation,, moderation, of, voluntary, movements,, maintainance of muscle tone. It is a regulatory, centre for neuromuscular activities and controls, the rapid activities like walking, running,, speaking etc. All activitie of cerebellum are, involuntanry (though may involve learning in, early stages). The medulla oblongata is the, posterior conical part of the brain and continues, as the spinal cord. It has inner grey matter and, outer white matter. It controls involuntary vital, functions like heart beat, respiration, vasomotor, activities and peristalsis. It also controls nonvital reflex activities like coughing, sneezing,, swallowing, vomitting, yawning etc. The, cavity of medulla is called IVth ventricle or, metacoel. It’s roof has the posterior choroid, plexes for secretion of CSF. The posterior, choroid plexes also shows 3 openings - a pair, of lateral foramen of Luschka and a median, foramen of Magendie., , 194, , •, •, •, , Internet my friend, Find out the role of the foramina, mentioned above., What is ataxia ?
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Can you tell?, 1. The functions of fore brain, 2. Injury to the medulla oblongata causes, sudden death - Explain., 3. Distinguish between cerebrum and, cerebellum., 4. About the mid brain., B. Spinal Cord :, Spinal cord is the part of central nervous, system and forms the lower extension of the, medulla oblongata of the brain. Like the brain,, it is covered and protected by bony covering, and membranes. It lies within the neural canal, of the vertebral column and is surrounded by, three meninges - dura mater, arachnoid mater, and pia mater. The Cerebro Spinal Fluid (CSF), secreted by pia mater, forms a fluid cushion, around the spinal cord and within it inside the, central canal., Externally, the spinal cord appears as long, cylindrical rod, 42 to 45 cm long and 2.0 to, 2.5 cm broad. The spinal cord is broadest at, its anterior end gradually tapers into conus, medullaris (L1 to L2) and continues as a, thread like filum terminale end posteriorly., Spinal cord shows two swellings along its, length called cervical and lumbar swelling., 31 pairs of spinal nerves arise from, lateral sides of the spinal cord. These nerves, are concentrated in the region of cervical, and lumbar swelling and around the conus, medullaris. The bunch of nerves in the hind, part of the spinal cord, along with the filum, terminale, appear like a horse’s tail, so called, cauda equina., T. S. of spinal cord, The spinal cord is dorsoventrally flattened, due to the presence of deep, narrow posterior, fissure and shallow, broad anterior fissure. A, central canal can be seen in the centre. The, fissures divide the spinal cord incompletely, into a right and left side. The grey matter is, somewhat H-shaped or butterfly shaped and, , is on the inner side, while the white matter is, on the outer side. The fissures divide the grey, matter into six horns, namely dorsal, lateral, and ventral horns, while the white matter is, divisible into 6 columns or funiculi, namely, dorsal, lateral and ventral funiculi. The dorsal, and ventral horns extend out of the spinal, cord as dorsal root and ventral root of spinal, cord respectively. Of these, the dorsal root is, connected to the dorsal root ganglion. (It lies, just outside and lateral to the spinal cord). It, has an aggregation/collection of unipolar, sensory neurons., Posterior median, fissure, Posterior, median, septum, White, matter, , Dorsal root, Dorsal horn, , Ependyma, Lateral horn, , Central, canal, Grey, matter, , Ventral horn, Ventral root, Anterior median fissure, , Fig. 9.11 : T. S. of spinal cord, The association or inter-neurons lie inside, the grey matter. The receive signal from the, sensory nerve, integrate it and direct the, response towards motor neurons lying towards, the ventral horn. The lateral horns have, neurons of autonomic nervous system (ANS)., The nerves arising from these neurons, emerge, out from the ventral root of spinal nerve., The white matter consists mainly of bundles, of myelinated nerve fibre called ascending and, descending tracts. The ascending tracts conduct, sensory impulses from spinal cord to the brain, and these lie in the dorsal column/funiculi., The descending tracts conduct motor impulses, from brain to the lateral and ventral funiculi of, spinal cord., Functions : The spinal cord is the main centre, for the most reflex actions. It provides pathway, for conduction of sensory and motor impulses, to and from the brain. It provides nervous, connection to many parts of the body., , 195
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2. Peripheral Nervous System (PNS) : The, peripheral nervous system connects the central, nervous system to the different parts of the body, having receptors and effectors. Depending, , on the connection to the CNS, the peripheral, nerves are classified into two main types Cranial nerves - connected to the brain., Spinal nerves - connected to the spinal cord., , Table 9.12 Cranial nerves - nature and functions, No., I., , Name, Olfactory, , Type, Origin, Sensory Olfactory bulb, , Organs Innervated, Epithelium of Nose, , Functions, Smell, , II., , Optic, , Retina of Eye, , Vision, , III., , Occulomotor, , IV., , Pathetic, , Sensory Side of, diencephalon, Motor Floor of, mid brain, Motor Floor of, mid brain, , V., , Trigeminal, (Dentist’s nerve), , Mixed, , a. Ophthalmic, , Sensory, , b. Maxillary, , Sensory, , c. Mandibular, , Mixed, , (largest), , VI., , Abducens, , Motor, , VII., , Facial (bearing, geniculate, ganglion), , Mixed, , VIII. Auditory, (vestibulocochlear), i. Vestibular, ii. Cochlear, IX. Glossopharyngeal, , Eye muscles (4 of 6, eye muscles), Eye muscles (1, of 6 eye muscles,, forehead scalp), Ventral side of, pons, Nasal cavity, Upper, eyelids,, forehead,, scalp,, conjunctiva,, lacrimal gland, scalp, Mucosa of nose,, palate, upper teeth,, upper lip, lower eye, lid parts of pharynx, Lower teeth, skin, over mandible cheek,, side of head in front, ear,, muscles, of, mastication, Pons, Muscles of eye ball,, lateral rectus muscle, , Movement of eye, ball, Rotation and, movement of eye, ball, Sensation of skin, touch, taste, jaw, movement., , Pons, , facial, scalp and, neck muscles,, lacrimal, sublingual,, submandibula, nasal, and palatine glands, , Facial expression,, movement of, neck, secretion, of tears, taste,, salivary secretion., , Internal Ear, , Hearing and, equilibrium, , Sensory Pons, , Mixed, , Side of medulla Pharynx, tongue,, oblongata, salivary glands, 196, , Movement of eye, , Taste, salivation, and swallowing
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X., , Vagus, (Pneumogastric), , Mixed, , Side of medulla Larynx, trachea,, oblongata, pharynx, alimentary, canal, heart, lungs,, pancreas, blood, vessels,, , XI., , Spinal accessory, , Motor, , XII., , Hypoglossal, , Motor, , Side of medulla Neck and shoulder, oblongata, muscles, reflexes, of thoracic and, abdominal vicera, larynx, pharynx, Side of medulla Tongue muscles, oblongata, , Cranial Nerves : These nerves develop from, the brain, in all amniotes (reptiles, birds and, mammals). There are 12 pairs of cranial, nerves. Roman numbering I to XII is used to, denote them. These nerves originate from or, terminate into the brain., According to their function, these are, classified as sensory (I, II, VIII), motor (III,, IV, VI, XI, XII) and mixed (V, VII, IX, X), nerves., The details of cranial nerves present in the, human body is presented in Table 9.15., Spinal Nerves : Thirty one pairs of spinal, nerves originate from the spinal cord. They, are mixed nerves and they provide two way, communication between the spinal cord and, part of the upper and lower limbs, neck and, trunk., Table 9.13 : Number and types of spinal, Nerves, Group, , No. of pairs Region of origin from, vertebral column, Cervical, 8 (C1-C8), Neck, Thoracis, 12 (T1-T12) Thorax, Lumbar, 5 (L1-L5), Abdomen, Sacral, 5 (S1-S5), Pelvis, Coccygeal 1 (Co1), Coccyx, , Visceral, sensations, and visceral, movements like, breathing cardiac,, slowing, gastric, and pancreatic, secretion,, gastrointestinal, movements, Movements of, larynx, pharynx,, neck and shoulder, , Movement of, tongue, , Do you know ?, 1. Of the 12 pairs of cranial nerves, only, the X (vagus) passes into the body and, innervates internal organs., 2. Vagus has the maximum number of, branches and longest distribution., 3. V/trigeminal/Dentist’s nerve is the, largest cranial nerve, 4. VI/abducens is the smallest cranial neve., Formation of a typical spinal nerve : All, spinal nerves are of the mixed type i.e. they, have some nerve fibre as sensory and some, motor. Each spinal nerve is formed inside, the neural canal of verterbral column by two, roots - the posterior or dorsal sensory root and, anterior or ventral root. Anterior root receives, the sensory nerve from the dorsal root ganglion, (cell bodies of sensory neurons are located in the, ganglion), while the anterior/ventral root gives, out the motor nerve. The dorsal sensory and the, ventral motor nerves together form the mixed, spinal nerve. It emerges out from both sides, of the spinal cord through the intervertebral, foramen. As soon as it emerges out of vertebral, column, it shows three branches viz., , 197
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•, , Ramus dorsalis : from skin and to muscles, of dorsal side, Ramus ventralis : the largest of the three, supplies the organs and muscles on lateral, and anterior side, Ramus communicans : the smallest of the, three and given out from 1st thoracic upto, 3rd lumbar (L3) spinal nerve. It joins the, sympathetic ganglia., , •, , •, , Grey matter, White matter, , Dorsal root, Dorsal root ganglion, Spinal nerve, Ramus, dorsalis, , Ramus, ventralis, Ventral root, Sympathetic, Ramus, communicans, ganglion, , Reflex Action : It is a sudden, spontaneous, automatic, involuntary response to stimulus., The response to stimulus is said to be, involuntary as it is carried out without any, conscious effort by the brain. The path along, which the action is carried out is called reflex, arc., [Note : In your earlier classes you have studied, about the reflex actions.], Human nervous system is divided into, CNS, PNS, ANS. PNS consist of network, of nerves arising from or going to the CNS., Accordingly peripheral nerves are classified as, a. Afferent nerves, b. Efferent nerves, Afferent nerve fibres transmit sensory impulse, from tissue or organ to the CNS and the, efferent nerve fibres transmit regulatory or, motor impulses from the CNS to the various, peripheral tissues and organ., , Fig. 9.14 Formation of Spinal Nerve, Chart 9.15 Types of Reflex actions, 1. On the basis of control over the actions., , •, •, •, , Reflex actions, , Cranial reflexes, carried out by brain, slow action response, eg. watering of mouth on sight or smell of, good food, , •, •, •, , Spinal reflexes, carried out through spinal cord, urgency for response is required so these are quick, acting, eg. withdrawal of leg while stepping on, something hot or pointed, , 2. Based on previous experiences, Reflex actions, , •, •, , Unconditional reflexes, These do not require any previous experience, eg. sneezing, coughing, yawning, hiccuping., , •, •, , Conditional reflexes, These actions are based on previous experience., eg. swimming, dancing, cycling etc., Initially these actions are voluntary when learning, is being done, later after perfection they become, involuntary. These were first studied by E. Pavlov, on salivation in dog (at the sight and sound of bell), , 3. According to number of synapses involved, Reflex actions, , •, , Simple monosynaptic, It involves only sensory and motor neurons eg., knee jerk reflex, , •, , 198, , Complex polysynaptic refexes, It involves sensory internervous and motor or, neurons eg. cycling, swimming, etc.
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Parasympathetic Nervous System, Constricts pupil, inhibits, III, secretion of tears, Stimulates, VII, IX Ganglion, flow of saliva, , Sympathetic Nervous System, Dilates pupil, Stimulates secretion of tears, Inhibits flow of saliva, , Medulla oblongata, , Slows, heartbeat, Constricts bronchi,, dilates blood vessels,, lowers B.P., Stimulates peristalsis, and secretion, , Accelerates heartbeat, Dilates bronchi, constricts blood vessels and increases B.P., , X, , Stimulates, release of bile, , Contracts, bladder, , Solar plexus, , to glucose, Inhibits peristalsis and secretion, nonadrenaline Conversion of glycogen, Stimulates, Secretion of, adrenaline and, , Chain of, sympathetic, ganglia, , Inhibits bladder, contraction, , Fig. 9.16 Autonomic Nervous System, However according to recent studies,, the extent of PNS has been broadened to, incorporate the ANS., According to this view, the PNS is divided, into, i. somatic nervous system and, ii. autonomic nervous system, The somatic nerous system relays impulses, from CNS to the skeletal or voluntary muscles, of the body., 3. Autonomic Nervous System (ANS) :, Autonomic nervous system transmits, impulses from CNS to the involuntary organs, and smooth muscles of the body., ANS consists of a special set of peripheral, nerves that regulate the activities of involuntary, organs like cardiac muscles, smooth muscles,, glands etc. In this, impulses are conducted, from the Central Nervous system by an axon, that synapses with an autonomous ganglion., It is preganglionic neuron. The second neuron, in this ganglionic pathway has an axon that, extends from the autonomic ganglion to an, effector organ and is known as postganglionic, neuron., Autonomic nervous system consists of, sympathetic and parasympathetic nervous, system., , Use your brain power, Mr. Sharma suffered from a stroke and, the right side of his body was paralysed., However his response was normal for knee, jerk reflex with either leg. Explain how and, why ?, a. Sympathetic Nervous System (SNS):, It is also called thoraco-lumbar outflow. It, originates in the thoracic and lumbar region of, spinal cord (T1 to L3) and consists of 22 pairs, of sympathetic ganglia which lie on a pair of, sympathetic cords on lateral sides of the spinal, cord., The pre-ganglionic nerve fibres are short, and post ganglionic nerve fibres are long., Adrenaline and Noradrenaline is produced, at the terminal ends of postganglionic nerve, fibres at the effector organ, hence it is also, called Adrenergic fibres. Sympathetic, nervous system controls body activities during, emergencies (fight or flight response). It has, excitatory and stimulating effect on most, organs of the body except in the digestive and, the excretory organ., , 199
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Table 9.17 : Comparison between sympathetic and Parasympathetic Nervous System, Organ/Region, , Sympathetic effect, , Parasympathetic effect, , Heart beat, , Increases, , Decreases, , Blood vessels, , Constricts, , Dilates, , Arterial B.P., , Increases, , Decreases, , Pupil of Eye, , Dilates, , Constricts, , Gastrointestinal movements, (stomach and intestine), , Retards peristalsis, , Accelerates peristalsis, , Urinary bladder, , Relaxes the bladder, , Contracts the bladder, , b. Parasympathetic Nervous System :, It is also called cranio-sacral outflow. It, consists of the branches from the cranial (III,, VII, IX, X) nerves, sacral (II, III) and spinal, (IV) nerves. It consists of ganglia which are, very close or within the wall of the effector, organs. The pre-ganglionic nerves are long, and post-ganglionic nerves are short. Acetylcholine is produced at the terminal end of postganglionic nerve at the effector organ, hence, these are also called cholinergic fibres., , defined by a type of stimuli that it can respond, to eg. a photoreceptor responds to light, what, exactly is the meaning of the receptor. It, implies that when a specific type of stimulus, reaches the sensory neuron (receptor) it causes, the production of an action potential in it and, this action potential is carried in the form of, an impulse. These impulses are conducted to, the different functional areas of the brain for, processing and interpretation., , Parasympathetic nervous system is, antagonistic to sympathetic nervous system. It, brings back to normal, all activities which are, stimulated by the sympathetic system. Hence, it is also called housekeeping system. It has an, inhibitory effect on most organs. However, the, activities like those associated with digestion,, peristalsis and micturition, which are inhibited, by sympathetic system are thus accelerated by, the parasympathetic system., , Curiosity Box:, 1. Ever wondered as to how we are able to, understand the smell of the first showers, of rain, or the sudden changes in the, climate ?, , The answers to all these questions are the, presence of a sensory system in our body. It, consists of simple to complex structures called, sensory receptors., 9.7 Sensory Receptors :, Sensory Receptors are some specialised, structures in the body to receive the various, stimuli from the external or internal, environment. The nature of the receptor is, 200, , 2., , How are we able to hear the chirping of, the birds and recognize the sound of the, bird ?, , 3., , How can we see and enjoy the beautiful, colours of the nature after the sunrise ?, Internet my friend, , Find out the fifth category of taste called, Umami apart from the four recognized ones, - salty, sour, sweet, bitter.
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Classification of receptors :, Receptors are classified on the basis of their location, function and their sensitivity to specific, stimuli. Their classification is given in the following chart., Chart 9.18. Types of receptors, No., , Name/Type of receptor, , Location, , Function, , I. Exteroceptors : Receive external stimuli, a. Phonoreceptors, , Internal Ear - organ, of corti, , Sound reception, , b. Statoreceptors, , Internal Earsemicircular canals, , Receptors for maintaining, balance and equilibrium, , c. Photoreceptors, , Retina of Eye, , Receives sensory stimuli for, vision, , d. Thermoreceptors, , Skin, , Receives sensory stimuli for, heat (caloriceptors) and cold, (trigidocetptors), , e. Mechanoreceptors, , Skin, , Sensitive to mechanical, stimuli like touch, pain,, pressure, deep pressure, etc., , f. Chemoreceptors, • Gustatoreceptors, • Olfactory receptors, , Taste buds of tongue, Olfactory Epithelium, of Nose, , Sensitive to taste of sweet,, salt, sour, bitter and umami., Sensitive to about 10,000, different smells, , II. Interoceptors : Receive stimuli coming from within the body, a. Enteroceptors, , from internal body, organs, , Sensitive to stimuli coming, from internal organs like, hunger, thirst, pain, osmotic, change, , b. Proprioceptors, , Joints, muscles and, tendons, , Detect changes in the, movements of joints, tendons, and muscles; pain, tension, and sensitive to vibrations, , c. Baroreceptors, (*These are also considered as, mechanoreceptors, receiving, signals from internal organ), , Present in walls of, atria, venae cavae,, aortic arch, carotid, sinus, , Sense changes in B.P. so, as to restore homeostasis, through vasodilation or, vasoconstriction, , 201
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Eye :, The eyes are a pair of sensory organs of, vision. These are located in the orbit of skull, with a cushion of fat around them. Each eye, is spherical/rounded and called eyeball. The, eyes are protected bones, eyebrows, upper and, lower eyelids with eyelashes and the lacrimal/, tear glands. Movement of the eyeball within, the orbit is controlled by 6 sets of muscles., Wall of the eyeball is made up of 3 layers, (1) sclera, (2) choroid and (3) retina, 1. Sclera/scelrotic : It is the outermost layer, made of dense fibroelastic connetive tissue with, collagen fibres. It provides attachment to the, eyeball muscles. The anterior thick, transparent, part of sclera is cornea. It is slightly bulged out, for focussing light on the retina. The sclera, is provided with blood vessels, however the, cornea is devoid of them. Cornea is nourished, by aqueous humour and also by lacrimal, secretion. The exposed part of sclera and the, entire Cornea are covered by a transparent, membranous covering called conjuctiva. It, provides protection and lubrication to the, cornea., , the vascular part of choroid sharply bends, into the cavity of eyeball, forming a thin and, coloured partition called iris. It is perforated in, the middle by an aperture called pupil. Smooth, muscles of the iris help in regulating the size, of pupil depending on the intensity of light, entering the eyeball. The pigment in the iris, determines the colour of the eye., Lens : It is a transparent, elastic, biconvex, structure. It is suspended in the eyeball by the, suspensory ligaments. The lens and suspensory, ligaments divide the cavity of the eyeball into, a small anterior aqueous chamber, filled with, a clear watery fluid aqueous humor and a, posterior large vitreous chamber, filled with a, jelly like vitreous humor. It maintains shape of, the eyeball and maintain pressure for keeping, the lens in position., Iris, , b. Ciliary body : It is a thick, muscular, ring, like structure at the junction of choroid and, iris. Its epithelium secretes aqueous humor., Attached to the ciliary body are suspensory, ligaments which hold the lens. The ligaments, and muscles of the ciliary body help in the, adjustment of the size of lens., c. Iris : At the junction of the sclera and cornea,, , Retina, , Cornea, Vitreous chamber, vitreous humor, , Choroid, Fovea, Blind, spot, , Pupil, , 2. Choroid /Uvea : It is the middle, vascular, and pigmented layer. It is not a complete layer, and can be divided into 3 regions - a. Choroid, proper b. Ciliary body c. Iris, a. The choroid proper : It lines the sclera., Due to its pigmented nature it prevents internal, reflection. The blood vessels of choroid provide, nutrition and oxygen to the retina., , Sclera, , Lens, , Anterior, chamber, aqueous, humor, , Optic nerve, Suspensory ligament, , Fig. 9.19 : Eye, 3. Retina : It is the innermost, delicate, non, vascular light sensitive layer. It has 2 regions, (a) single layer of pigmented non sensory part, lining the iris and ciliary body (b) sensory part, lining the choroid. It has an outer pigmented, part and an inner nervous part. The inner, nervous part is transparent and made of 3, layers (1) outer photosensitive layer made of, rod and cone cells. (2) middle layer of bipolar, nerve cells (3) inner layer of ganglion cells. The, nerve fibres from the basal end of the ganglion, cells collectively form the optic nerve., , 202
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Light, , Do you know ?, Why do eyes of cats and dogs glow in the, night ? The glowing of eyes in some animals, is due to presence of a reflecting layer behind, the retina, called tapetum lucidum., , To optic, nerve, , Nerve fibers, , Ganglion cell, Amacrine cell, , The blind spot is an area diagonally, opposite to the lens. It is the area of retina from, where the optic nerve and blood vessels leave, the eyeball. There are no rod and cone cells in, this region. An area, lateral to the and above, the blind spot is called yellow area or macula, lutea. At its centre is a depression called lovea, centralis. It has maximum density of cone cells, and is the place of formation of sharpest vision., The rod and cone cells lie deep in the retina,, so that light has to pass through the ganglion, and bipolar cells before reaching them., Photo receptor cells : These are of two, types (a) Rod cells (b) cone cells., They contain light sensitive proteins, termed as photopigments. The cones are, responsible for daylight (photopic) vision and, colour vision. While the rods function in dim, light (Scotopic) vision. The purple red protein, called rhodopsin is present in the rods which, is vitamin A derivative. The cones are of three, types, which contain their own characteristic, photo-pigments that respond to red, green, and blue lights. Various combinations of, these cones and their photopigments produce, sensation of different colours. The sensation of, white light is produced due to the simultaneous, equal stimulation of these three types of cones., , Bipolar cell, Horizontal cell, Cone, Rod, Pigment epithelium, Choroid, Sclera, , Fig. 9.20 : Structure of retina, Generation of image :, The light rays from the object pass through, the conjunctiva, cornea through the pupil upon, the lens and is focused on the retina to form, an image. In the visual area of cerebrum, the, nerve impulses are analysed and the image, formed is recognized., , The Optic nerve consists of the fibres, arising from the base of ganglion cells. It leaves, the eye ball from the posterior side and carries, visual impulses from the retina to the brain., , 203, , Always Remember, Accomodation : The lens makes fine, adjustments to bring a sharp focus on retina., The ability of the lens by which the light ray, from far and near objects is focused on the, retina is called accomodation power of the, lens., Internet my friend, •, •, •, •, , Find out information about those who, can donate eyes ?, Is there any age limit for donating eyes ?, Who cannot donate eyes ?, Facts about eye donation.
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auditory canal. The tympanic membrane, is a delicate, membranous structure which, transmits the sound waves to the middle ear., It is formed of connective tissues covered with, skin on the outside and mucous membrane on, the inside., , Activity :, Collect information about causes and, corrections for myopia, hypermetropia,, astigmatism, presbyopia, cataract, night, blindness., , The middle ear consists of chain of, three ear ossicles called Malleus (hammer),, Incus (anvil) and Stapes (stirrup-the smallest, bone). On receiving the vibrations from the, tympanic membrane, the ear ossicles amplify, the vibrations and transfer these to the cochlea., A short eustachian tube connects the middle, ear to the pharynx. It equalises air pressure on, both sides of the ear drum., , Changes in retina when light rays fall on it, Light falls on rod and cone cells in Retina, Breaking up of light sensitive pigments by, specific wavelength of light, Stimulation of rod and cone cells and generation, of nerve impulse, , The internal ear consists of the labyrinth, and vestibular apparatus. The labyrinth consists, of bony labyrinth and membranous labyrinth., These are filled with perilymph and endolymph, respectively. The coiled portion of the labyrinth, is cochlea., , Nerve impulse transmitted to bipolar nerve cells, Nerve impulse transmitted to ganglion cells, Nerve impulse in the axons of ganglion cells, converge and leave via the optic nerve, Nerve impulse is transmitted by optic nerve to, brain, Perception of image by the brain cells, (in the visual area of cerebrum), , Ear :, The human ear is called stato-acoustic, organ and it has two functions - hearing and, body equilibrium. Anatomically the ear is, made up of three parts : the external ear, middle, ear and inner ear., The external ear consists of ear pinna,, auditory canal and tympanic membrane. In, humans, the ear pinna is an immovable part,, supported by elastic cartilage structure. It leads, into an auditory canal. The pinna collects and, sends the sound waves into the auditory canal., The auditory canal ends at the ear drum. It, transfers the sound waves to the ear drum., There are very fine hair and wax secreting, sebaceous glands in the skin of pinna and, , The cochlea contains fluid filled three, chambers separated by Reissner’s membrane, and basilar membrane. The upper chamber, towards vestibul is called scala vestibuli and, the bottom chamber scala tympani are filled, with perilymph. The middle chamber is the, scala media. It is filled with endolymph while, scala vestibuli and scala tymphnith are filled, with perilymph. The organ of Corti is a pea, sized structure located on basilar membrane, (floor of scala media)., The organ of corti has a sensory epithelium, over the basilar membrane. The sensory, epithelium is in contact with a gelatinous, tectorial membrane. The sensory cells have, sensory hair on their free end so also called, hair cell. In between the rows of hair cells are, present supporting cells., Hair cells have long stiff microvilli called, stereocillia on their apical surfaces. Above, these stereocellia, is a jelly like membrane, , 204
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Ossicles :, Temporal bone, , Stapes, , Semicircular ducts, , Incus, , Vestibular nerve, , Malleus, , Cochlear, nerve, , Auricle, , Cochlea, Earlobe, Auditory, canal, , Tympanic, cavity, , Eardrum, , Auditory tube, , Fig. 9.21 : Structure of human ear, called tectorial membrane. This organ acts as, a transducer, converting sound vibrations into, nerve impulses., , Bony labyrinth, Anterior, , Inner Ear and the mechanism of balance :, Besides the cochlea, the inner ear also has, the vestibular apparatus which is composed, of three semi-circular canals and the utriculo, saccular region with the otolith organ. All three, semi-circular canals lie in different planes, at right angle to each other. These canals are, filled with endolymph. The base of each of, the canal has an ampulla in which there is a, sensory spot called crista. The cristae help in, maintaining equilibrium. The vestibule has, two sensory spots-macula of saccule and utricle, the macula consist of hair cells and supporting, cells. Tips of the hair and cilium project into a, thick gelataneous sheath otolithic membrane., Within this membrane minute particle otoliths, or otoconia are secreted. These are made of, CaCO3 and protein. The macula and crista, are the receptors sensitive to the position of, the head with respect to gravity. The three, semicircular canals are arranged such away, that the movement in any plane can be detected, by these cells and the balance and posture of, the body is maintained. Receptors for dynamic, balance lie in the cristae of ampullae while for, , Posterior, Lateral, Ampulla of, semicircular duct, , Membranous labyrinth, Ampulla of semicircular, canal, Endolymphatic sac, Utricle, Vestibule, Saccule, Cochlea, , Oval window, , Cochlear, duct, , Secondary tympanic, membrane in round window, Vestibular, canal, Cochlear, duct, Basilar, membrane, Tympanic, canal, , 205, , Bone, Auditory, nerve, , Organ of corti, , Fig. 9.22 : Human Internal Ear, , Activity :, The auditory centre of the brain analyses, the impulses received and the sound is, perceived., Draw flow chart of mechanism of, hearing.
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static/linear balance these are in the maculae, of utriculus and sacculus., Mechanism of Hearing :, Pinna of the ear receives the sound, waves and directs them to eardrum. Eardrum, vibrates and these vibrations are amplified, and transmitted through the ear ossicles to, the endolymph inside cochlea. This generates,, wave in the endolymph. These waves induce, ripples in the basilar membrane. These, movements in the basilar membrane cause the, hair cells to press against tectorial membrane., This generates nerve impulse in the afferent, neurons. Impulse is sent to the brain via the, auditory nerve. Auditory cortex of the brain, decodes the sound., , Alzheimer’s disease :, It is the most common form of dementia., Its incidence increases with the age, showing, the loss of cognitive functioning -thinking,, remembering, reasoning and behavioral, abilities to such an extent that it interferes with, the persons daily life and activities. It occurs, due to loss of cholinergic and other neurons in, the CNS, accumulation of amyloid proteins., There is no cure for Alzheimer’s, but treatment, slows down the progression of the disease and, may improve the quality of life., CHEMICAL COORDINATION, The cells and organisams communicate, with each other through chemical signals. Also, they are broadly of four types as follows :, Autocrines : Cells release secretion to stimulate, itself., , Use your brain power, 1. What is the function of tympanic, membrane?, 2. Enlist the various receptors found at, various location in the body., , Paracrines : Cells release secretion to stimulate, neighbouring cells., , 9.8 Disorders of nervous system :, Psychological disorders :, Commonly called mental disorders, are a, wide range of conditions that affect the mood,, thinking or behaviour. These affect multiple, areas of life and create distress for the person, suffering from it. Some of the major categories, of psychological disorders are - Intellectual, disability (formerly known as mental, retardation), Autism spectrum disorder, bipolar, disorder, depression, anxiety disorder, ADHD, (Attention Deficit Hyperactivity Disorder), and, stress related disorders., Parkinson's disease :, Degeneration of dopamine-producing, neurons in the CNS causes Parkinson's disease., Symptoms develop gradually over the years., Symptoms are tremors, stiffness, difficulty in, walking, balance and co-ordination., , Endocrines : Cells release secretion to, stimulate distant cells., Pheromones : Organs release secretions to, stimulate other organism., Higher animals have complex body, organization. Due to this, in addition to the, nervous coordination, there is need of chemical, coordination. Chemical coordination is carried, out by secretions of ductless glands. This, chemical coordination system is also called the, endocrine system., 9.9 Endocrine system :, The endocrine system controls body, activities by means of chemical messengers, called hormones. Hormones are released, directly into the blood. The hormone is carried, all over the body via blood. However the, message is relayed only to the target organs, which are stimulated to carry out specific, process which include activities like growth, and development., , 206
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I., , II., , III., IV., V., , VI., , Chemical nature of hormones, Amines : These are simple amines., Catecholamines secreted by adrenal, medulla, epinephrine and non-epinephrine, and melatonin from pineal gland. Some, are modified from the amino acids. e.g.,, Thyroxine., Peptide hormones : These hormones, consist of long or short chains of amino, acids. e.g. Hormones of hypothalamus, oxytocin, ADH, GnRH., Protein hormone : Insulin, glucagon, TSH, FSH, LTH, GH, relaxin., Fatty acid derivatives :- Prostaglandin, Steroid hormones : These hormones are, lipid soluble and derived from cholesterol, and other steroids. e.g. estrogen, testosterone, aldosterone. Action of these, hormones is concerned with long lasting, responses., Gas : NO (Nitric Oxide), , Properties of Hormones :, They act as chemical messengers and are, effective in very low concentration. Hormones, can function as regulators that inhibit or, stimulate or modify specific processess. Some, hormones interact with receptors present on, plasma membrane of target cells where as, some enter the necluses to interact with genes., Hypersecretion or Hyposecretion of hormons, leads to various disorders., These are metabolised after their function., Thus cannot be reused. Hormone secretion is, regulated by positive or negative feedback, mechanism., Mechanism of hormone action :, Hormones are released in a very small, quantity. They produce their effect on the target, organs cells by binding to hormone receptors., The hormone receptors may be on the cell, membrane or may be intracellular. A hormone, , Activity :, Identify the glands and state their functions., , 207
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hormone receptor complex is formed and this, leads to biochemical change in the target tissue., A. Mode of hormone action through, membrane receptors :, Hormones like catecholamines, peptide, and polypeptide hormones are not lipid soluble., Therefore they cannot enter their target cells, through plasma membrane., These non steroid water soluble hormones, interact with surface receptor, which initiate, metabolic activity. Molecules of amino acid, derivatives, peptide hormones bind to specific, receptor molecules located on the plasma, membrane. The hormone receptor complex, causes the release of an enzyme adenylate, cyclase from the receptor site. This enzyme, forms cyclic AMP from ATP of the cell. cAMP, activates enzymatic actions. The hormone acts, as the first messenger and cAMP is the second, messenger. Other kind of second messengers, are Ca++, cGMP and IP 3(Inositol triphosphate)., Hormone (e.g., FSH), , Receptor, , B. Mode of action through intracellular, receptors :, Steroid and thyroid hormones are lipid, soluble and easily pass through plasma, membrane of target cell into the cytoplasm., In the cytoplasm, they bind to specific intra, cellular receptor proteins forming a hormonereceptor complex that enters the nucleus. In, the nucleus, the hormone receptor complex, binds to a specific regulatory site of DNA., The activated genes transcribes mRNA which, directs protein synthesis and enzymes in the, cytoplasm. Action of lipid soluble hormones is, slower but long lasting., , Receptorhormone, complex, , Physiological responses, (e.g., ovarian growth), , Fig. 9.23 : Mechanism of hormone action, through membrane receptor, Internet my friend, What is negative and positive feedback, of hormone action ?, , Proteins, , Fig. 9.24 : Mechanism of hormone action, through intracellular receptor, , Response 1, , Biochemical responses, , Nucleus, Genome, mRNA, , Physiological responses (Tissue, growth and differentiation), , Ovarian cell, membrane, , (Generation of secondary messenger), (Cyclic AMP or Ca++), , Uterine cell, membrane, , Hormone, (e.g. oestrogen), , 9.13 Major endocrine glands :, A. Hypothalamus :, It is ectodermal in origin. It is located at, the floor of diencephalon. Major function of, hypothalamus is to maintain homeostasis., It controls the secretory activity of pituitary, gland by the, release, and, inhibiting, hormones. All hormones of hypothalamus, are peptide hormones. They are secreted by, the neurosecretory cells so they are called, neurohormones. The hormones secreted by, hypothalamus are : ADH, Oxytocin., , 208
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lying in the cleft between the anterior and, posterior lob., , 1. Adrenocorticotropin, Releasing, Hormone : It stimulates the release of, ACTH by the anterior pituitary gland., 2. Thyrotropin Releasing Hormone : It, stimulates the release of TSH by anterior, pituitary gland., 3. Gonadotropin Releasing Hormone, (GnRH) : It stimulates pituitary to secrete, gonadotropins., 4. Prolactin, Inhibiting, Hormone, (Prolactostatin) : It inhibits prolactin, release by anterior piturary gland., 5. Somatostatin : It inhibits the release of, growth hormone., 6. Somatotropin stimulates release of, growth hormone., 7. Gastrin Releasing Peptide (GRP) and, 8. Gastric Inhibitory Polypeptide (GIP), , Neurohypophysis is connected directly, to the hypothalamus by axon fibres., Adenohypophysis and intermediate lobes, are connected to the hypothalamus through, hypophyseal portal system., Hypophyseal portal system :, Various hormones secreted by, hypothalamus reach the pituitary gland, through the hypophyseal portal system. The, portal vein collects blood from various parts, of hypothalamus and opens into anterior lobe, of pituitary. From pituitary, the vein finally, carries the blood into the superior vena cava., Supraoptic nucleus, (ADH), , B. Pituitary gland or hypophysis gland :, Paraventricular, nucleus, The pituitary gland is the smallest gland., (oxytocin), Pituitary gland is a pea sized reddish-grey, coloured gland. It controls almost all other, endocrine glands, hence earlier it was called, Optic, Median eminence, the master endocrine gland. It is located just chiasma, below the hypothalamus and is attached to it, Infundibulum, by a stalk called infundibulum or hypophyseal, Hypophyseal, Hypophyseal, stalk. Pituitary gland remains lodged in a bony, artery, portal vein, depression called sella turcica of the sphenoid, Pars, bone. Pituitary gland consists of two lobes intermedia, Pars nervosa of, neurohypophysis, called anterior lobe (Adenohypophysis) and Pars distalis of, posterior lobe (Neurohypophysis). Both the adenohypophysis, lobes develop from different parts of embryo., Hypophyseal vein, Hence it has of dual origin., Fig. 9.25 : Pituitary gland, Adenohypophysis is an outgrowth from the, roof of buccal cavity. This outgrowth is called, Rathke’s pouch. It grows upward towards, the brain. The neurohypophysis grows as a, downward extension of hypothalamus. The, two outgrowths together form the pituitary, gland. The connection of Rathke’s pouch with, pituitray gland is lost in embryo. Intermediate, lobe (Pars intermedia) is a small reduced part, , Adenohypophysis: It is the larger lobe of, pituitary gland. It is a highly cellular and, vascular part of pituitary gland. It contains, various types of epitheloid secretory cells,, acidophils, basophils, chromatophores. It is, differentiated into three parts – pars distalis,, pars intermedia and pars tuberalis. ., , 209
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The hormones of adenohypophysis are, as follows :, 1. Somatotropin /Somatotropic Hormone /, STH / Growth hormone / GH :, This hormone stimulates growth and, development of all tissues by accelerating, protein synthesis and cell division. Highest, secretion the GH is seen till puberty and then, its secretion of becomes low. However, it is, continuously secreted through out life for repair, and replacement of body tissue or cells., Improper secretion of growth hormone, produces various disorders. Hyposecretion, of growth hormone since childhood results in, stunted physical growth and condition is called, pituitary dwarfism., Hypersecretion of growth hormone in, childhood causes Gigantism, a condition of, overgrowth. The individual attains abnormal, height. When the pituitary gland produces, excess growth hormone in middle aged adults,, it results in disproportionate growth causing, disfigurement and enlargement of bones of, nose, lower jaw, hands, fingers and feet. The, condition is called Acromegaly., 2. Thyrotropin / Thyroid stimulating, Hormone / TSH : Its primary action is to, stimulate the thyroid gland secretion of the, hormone thyroxine., 3. Adreno corticotropic hormone / ACTH, / Adrenocorticotropin : It stimulates, adrenal cortex to produce and secrete its, hormones. It maintains functioning of, adrenal cortex., 4. Prolactin / Luteotropin / Mammotropin:, Prolactin is unique among pituitary, hormones as it is under predominant, inhibitory control from hypothalamus., Prolactin activates growth of breasts during, pregnancy (mammotropin) and stimulates, the milk production and secretion of milk, (lactogenic) by mammary gland after child, birth., , Internet my friend, Collect the information about, Simmond’s disease and Gorilla rib., 5. Gonadotropin :, a. Follicle stimulating hormone/ FSH :, It stimulates growth of ovarian follicles, in the females, while in males, it is concerned, with the development of seminiferous tubules., b. Leutinizing Hormone/ LH :, In female, the leutinizing hormone helps, in ovulation (discharge of ovum from graafian, follicle). FSH and LH are responsible for, stimulation of ovaries to produce oestrogen, while LH induces the ruptured follicles to, develop into corpus luteum and for production, of progesterone., c. Interstitial cell stimulating hormone /, ICSH :, In males, it stimulates the testes to produce, the androgen called testosterone. Testosterone, is responsible for development of secondary, sexual characters., Neurohypophysis: It is differentiated into, three parts, 1. Pars nervosa/ neural lobe 2., Infundibulum 3. Median eminence., The pars nervosa acts as storage area for, the secretions of hypothalamus. It stores and, releases oxytocin and vasopressin., 1. Oxytocin : It stimulates contraction of, uterus during parturition. It also stimulates, the contraction of mammary glands to initiate, ejection or release of milk. So is called birth, hormone or milk ejecting hormone., 2. Antiduretic Hormone (ADH)/ Vasopressin:, It stimulates the re-absorption of water in, distal convoluted tubule and collecting ducts of, uriniferous tubules of the kidneys. It decreases, loss of water by reducing the urine quantity., It increases blood pressure by causing vaso, constriction., , 210
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Deficiency of ADH reduces water reabsorption and increases urine output. This, condition is called diabetes insipidus No, glucose is lost in the urine. Excessive micturition, causes excessive thirst. This condition is called, polydipsia., Hypothalamus, , Neurosecretory, cell, , Neurosecretory, cell, , Pituitary portal, system, Posterior, pituitary, , Anterior, pituitary, , Kidney, , C. Pineal gland : The pineal gland is given off, from the roof of diencephalon and is located, between the two cerebral hemispheres. The, pineal gland is sensitive to the biochemical, signals of light. It secretes a hormone called, melatonin also known as sleep hormone., Melatonin is derived from tryptophan and, plays a very important role in the regulation, of Biological Clock (e.g. 24 hour diurnal, rhythm) of our body. It helps in maintaining the, normal rhythm of sleep-wake cycle and also, influences body temperature, metabolism and, reproductive cycles., , Ovaries, , tubules, Testes, , Brain, Corpus callosum, , Smooth, , Bones, Adrenal, , Thalamus, , Oxytocin, , Hypothalamus, , muscle, Tissues Memmary, glands, , Pineal gland, , Thyroid, , Pituitary gland, , cortex, , H 3C, , H, N, , Brain stem, , Fig. 9.26: Hypothalamus, Adenohypophysis, and Neurohypophysis, , O, , HN, , , , , CH 3, , Melatonin- Sleep Hormone, , Fig. 9.27 : Pineal gland, Pars intermedia : It is poorly developed, in human beings. It secretes Melanocyte, Stimulating Hormone (MSH) in some lower, vertebrates., MSH stimulates the dispersion of melanin, granules in melanocytes and is responsible for, skin pigmentation., Can you tell?, 1. State properties of hormones ?, 2. Explain the mode of action of steroid, hormones ?, 3. Describe neurohormonal regulation of, pituitary and thyroid gland ?, 4. Give names and functions of hormones, secreated by adenohypophysis ?, , D. Thyroid gland :, It is the largest endocrine gland. This, bilobed gland is situated in front of the trachea, just below the larynx. It is richly supplied with, blood vessels. The two lobes of thyroid gland, are connected a non-secretory band called, isthmus. The thyroid lobes are composed of, rounded follicles held together by interfollicular, connective tissue called stroma. The stroma, contains blood capillaries and small group of, parafollicular cell or ‘C’ cells (clear cells)., Thyroid follicles are composed of cuboidal, epithelium resting on a basement membrane, and is filled with a gelatinous colloid., , 211
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Think about it, Larynx, , 1. Patient suffering from hypothyroidism, shows increased level of TSH. Why ?, 2. Why do we use iodized salt?, 3. In which part thyroid gland stores its, hormones?, , Left thyroid, gland, , Right thyroid, gland, Trachea, , A, , Parafollicular, cells or C- cells, , Follicular cells, , Blood, capillaries, , Thyroid follicles, , B, Fig. 9.28 Thyroid gland, Thyroid gland is stimulated to secrete its, hormones by thyroid stimulating hormone, (TSH). The two hormones secreted by, the follicular cells are Thyroxine/tetra, iodothyronine/ T4 (four atoms of iodine) and, Triiodothyronine or T3 (three atoms of iodine)., Thyroxine is synthesized by attaching iodine, to amino acid tyrosine by enzymatic action., The amino acid tyrosine molecule binds to, iodine to produce Monoiodotyronine (T1) or, 2 atoms of iodine to produce Diiodothyronine, (T2). T1 and T2 molecules bind end to end, to make colloidal mass inside the follicle., They are further metabolised to prepare T3, and T4. Triidothyronine or T3 is also secreted, in small quantity. It is physiologically more, active. Thyroid gland is the only gland that, stores its hormones. T3 and T4 hormones are, stored before secretion and are regulated by, thyrotropin of pituitary gland by negative feed, back mechanism., , Thyroxine regulates the basal metabolic, rate of body. It also regulates metabolism, by stimulating protein, synthesis, and, promotes growth of body tissues. It helps, in thermoregulation by increasing heat, production. It increases action of neuro, transmitters- adrenaline and nor adrenaline. It, also supports the process of RBC production, and maintenance of water and electrolyte, balance. It also regulates reproductive cycles, in females., Parafollicular cells or ‘C’ cells produce, calcitonin hormone, which regulates calcium, metabolism., Disorders related to thyroid gland:, a. Hyperthyroidism :, It is caused by increase in the levels of, thyroid hormones. This increases metabolic, rate, sensitivity, sweating, flushing, rapid, respiration, bulging of eye balls, and affects, various physiological activities., , Fig. 9.29 Bulging eyeballs, Grave’s disease (Exopthalmic goitre) :, Hyperthyrodism in adults, is characterised by, protruding eyeballs, increased BMR and weight, loss. Increased BMR produces a range of effect, like increased heart beat, increased BP, higher, , 212
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body temperature, nervousness, irritability,, tremor of fingers and bulging eyeballs., , Find out, , b. Hypothyroidism : It is caused by deficiency, of thyroid hormones or removal of thyroid, gland (Thyroidectomy)., , Why are African pygmies diminutive. Is, it due to lack of GH, thyroxine or absence of, thyroxine receptors on their cell surface?, , Cretinism : Hyposecretion in infants leads to, cretinism. A cretin has reduced BMR and low, oxidation. They are short statured because, the skeleton fails to grow. They are mentally, retarded. They show dry skin, thick tongue,, prolonged neonatal jaundice, lethargy and, constipation. This can be treated by early, administration of thyroid hormones., The, cretin shows stunted physical growth delayed, puberity and mental retardation., , Calcitonin : It is secreted by the ‘C’ cells. It, regulates the concentration of calcium and, phosphorus in the blood. It is under feedback, control of plasma calcium concentration in, plasma. It is secreted when concentration, of calcium rises in the blood. It lowers, concentration of calcium and phosphorus in, the plasma by decreasing their release from the, bones and accelerating the uptake of calcium, and phosphorous by the bones., , Myxoedema : It is the deficiency of thyroid, hormones in adults. It is characterised by, a peculiar thickening and puffiness of skin, and subcutaneous tissue particularly of the, face and extremities. Patient lacks alertness,, intelligence. The patient suffers from slow heart, rate, low B.P., always feeling cold, low body, temperature and retarded sexual development., , E. Parathyroid gland :, Parathyroid gland is situated on the, posterior surface of the lobes of thyroid gland., Parathyroids are four in number and named as, superior and inferior parathyroid glands. The, cells of parathyroid glands are arranged in a, compact mass., The parathyroids secrete a peptide, hormone called parathormone (PTH). It is, also called Collip’s hormone. It regulates, calcium and phosphate balance between blood, and other tissues. Release of parathormone, increases blood calcium level. It draws calcium, from bones increases calcium absorption in the, digestive tract and reduces loss of calcium in, the urine. Secretion of parathormone is under, feedback control of blood calcium level., , Do you know ?, During pregnancy, hypothyroidism, causes, defective, development, and, maturation of growing baby., Simple goitre : (Iodine deficiency goitre) Iodine, is needed for synthesis of thyroid hormone. If, there is deficiency of iodine in the diet, it causes, enlargement of thyroid gland leading to simple, goitre. This disease is common in hilly areas., Addition of iodine to table salt prevents this, disease. Size of the thyroid gland is increased, but total output of thyroxine is decreased., , Hyoid bone, Epiglottis, Larynx, Thyroid, gland, Trachea, , Superior, parathyroid, gland, Inferior, parathyroid, gland, , Fig. 9.31 Parathyroid gland, , Fig. 9.30 Simple goitre, 213
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Concentration of calcium and phosphate, is maintained by parathormone and calcitonin., These two hormones form an antagonistic pair, like insulin and glucagon., Hyposecretion of parathormone lowers, concentration of calcium in the blood. This, increases excitability of nerves and muscles, causing muscle twitch and spasm. This is called, parathyroid tetany or hypocalcaemic tetany., Hypersecretion of parathormone is responsible, for more absorption of calcium from bones, i.e., demineralization of bones resulting in, softening, bending and fracture of bone. This, is called osteoporosis. It is common in women, who have reached menopause., Can you tell?, 1. With the help of a suitable diagram, describe the structure of thyroid gland., 2. How does fall and rise in blood calcium, stimulate secretion of parathyroids?, F., , Thymus gland :, Thymus gland is located in the upper, part of thorax on the dorsal side of the heart., It is soft, pinkish, bilobed mass of lymphoid, tissue. It is a prominent gland at birth but gets, gradually atrophied in the adult, so it is called, temporary gland., , It secretes the hormone thymosin. It has an, important role in the development of immune, system by maturation of T-lymphocytes., It also promotes production of antibodies, by providing humoral immunity., G. Adrenal gland/Suprarenal gland :, Adrenal glands have dual origin from, mesoderm and ectoderm. They are located, on the upper border of each kidney. Adrenal, glands are small, conical yellowish glands and, show two distinct regions, outer cortex and, inner medulla., 1. Adrenal cortex :, Adrenal cortex is derived from embryonic, mesoderm. Adrenal cortex secretes many, hormones together called corticoids. It is, differentiated into three concentric regions., a. Outer thin zona glomerulosa : It secretes, Mineralocorticods. They are, released, for regulating sodium and potassium ion, concentration. They regulate salt-water, balance, blood volume and blood pressure., Aldosterone (salt retaining hormone) is the, main mineralocorticoid. It balances Na-K, levels., , Capsule, Zona glomerulosa Zona, , Cortex, Medulla, , fasciculata Zona, Adrenal cortex, , reticularis Adrenal, Adrenal medulla, , Fig. 9.32 Histology of Adrenal gland, 214, , medulla
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b. Middle thick zona fasciculata : It is, responsible for secretion of Glucocorticoids, like cortisol. It regulates metabolism of, carbohydrates, proteins and lipids. Cortisol is, an important glucocorticoid. It is responsible, for increase in blood glucose level. It is also, immuno suppressive. It suppresses synthesis of, antibodies. So it is used in treatment of allergy., It prepares animals to face emergencies in, nature., c. Inner thin zona reticularis : It is, responsible for production of sex corticoids, (Gonadocorticoids). In males, they have, a role in development and maintenance of, external sex characters. Excess sex corticoids, in female causes adrenal virilism and hirsutism, (excess hair on face) while in males it causes, gynaecomastia i.e. enlarged breast. Androgens, and estradiols are the produced by the adrenal, cortex., Disorders related to Adrenal cortex :, a. Hyposecretion of mineralocorticoids and, glucocorticoids is responsible for Addison’s, disease. Characteristic features of this disease, are low blood sugar, low Na+ and high K+, concentration in plasma, increased loss of, Na+ and water in urine. It leads to weight loss,, weakness, nausea, vomiting and diarrhoea., b. Hyper secretion of glucocorticoids produces, Cushing’s disease. It leads to high blood sugar, level, excretion of glucose in urine, rise Na+ in, blood volume, high blood pressure, obesity and, wasting of limb muscles., Adrenal medulla : It develops from, ectoderm. It secretes two, hormones, adrenaline (epinephrine) and noradrenaline, (norepinephrine). Adrenaline is also known as, emergency hormone, also called 3F hormone, – (fight, flight and fright). Noradrenaline, regulates the blood pressure under normal, condition. It also acts as vasoconstrictor., , H. Pancreas :, It develops from endoderm. It is both, exocrine (studied in Digestive System) and, endocrine gland. Endocrine cells of pancreas, form groups of cells called Islets of Langehans., There are four kinds of cells in islets of, Langerhans which secrete hormones., I. Alpha () cells (20%) secrete glucagon., It stimulates liver for glucogenolysis to, increase blood glucose level., II. Beta () cells (70%) secrete insulin., It stimulates liver and muscles for, glycogenesis. This lowers blood glucose, level., III. Delta () cell (5%) secrete somatostatin, which inhibits the secretion of glucagon, and insulin. It also decreases the gastric, secretions, motility and absorption in, digestive tract., IV. PP cells or F cells (5%) secrete pancreatic, polypeptide (PP). It inhibits the release of, pancreatic juice., Disorder related to pancreas :, Diabetes mellitus (Hyperglycemia), This is the most common metabolic, endocrine disorder of pancreas. It leads to, increase in blood glucose level. This is due to, under activity of Beta cells, which results in, reduced secretion of insulin. In children, such a, condition is called insulin dependent diabetes, mellitus/ Type I (IDDM) The other form of, diabetes is Non insulin dependent diabetes, mellitus/ Type II (NIDDM). It is caused due, to failure of insulin to facilitate the movement, of glucose into cells. Reduced sensitivity to, insulin is called insulin resistance., , 215
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Can you tell?, 1. Distinguish between glucocorticoids and, mineralcorticoids., 2. Name the hormones secreted by the, adrenal cortex and state their role., 3. Write a note on Islets of Langerhans., 4. Pancreas is both exocrine as well as, endocrine gland. Give reason., In both disorders, blood glucose level, increases. Some of the glucose is excreted in, urine. It also causes excessive urination and, dehydration of body tissues. Degradation, of fats increases formation of ketone bodies, (ketosis). Administration of insulin lowers, blood glucose level., I. Gonads :, Gonads are sex organs (the testes and the, ovaries)., i. Ovaries : They produce, 1. Estrogen : These are secreted by developing, follicle. Estradiol is the main oestrogen. It is, responsible for secondary sexual characters, in female., 2. Progesterone : It is secreted by corpus, luteum of the ovary after ovulation. This, hormone is essential for thickening of, uterine endometrium, thus preparing the, uterus for implantation of fertilized ovum. It, is responsible for development of mammary, glands during pregnancy. It inhibits uterine, contractions during pregnancy., 3. Relaxin : It is secreted by the corpus luteum, of the ovary at the end of gestation period., It relaxes the cervix of the pregnant female, and ligaments of pelvic girdle for easy birth, of young one., 4. Inhibin : It is secreted by the corpus, luteum. Inhibin inhibits the FSH and GnRH, production., , ii. Testes :, Testes secrete male sex hormones called, androgens such as testosterone., Testosterone : It is secreted from interstitial, cells or Leydig cells by the influence of, luteinising hormone (LH). Rise in testosterone, level in blood above normal inhibits LH, secretion., It is also responsible for appearance of, secondary sexual characters such as facial and, pubic hair, deepening of voice, broadening of, shoulders, male aggressiveness, etc. It also, helps in maintenance of testes., J. Diffuse endocrine glands, Placenta :, It is the intimate connection between foetus, and uterine wall of the mother for physiological, exchange of the material. Placenta is a, temporary endocrine gland., During pregnancy, placenta secretes, hormones such as estrogen, progesterone, hCG, (Human Chorionic Gonadotropin) and human, placental progesterone. These hormones check, the contraction of uterine muscles and also, maintain the thickness of uterine endometrium, thus they help to maintain pregnancy., Gastro intestinal tract :, Do you know ?, Presence of HCG in urine sample, indicates pregnancy., In the gastrointestinal mucosa, certain cells, are endocrine in function. These cells produce, hormones which play vital role in digestive, processes and flow of digestive juices., 1. Gastrin : It stimulates gastric glands to, produce gastric juice., 2. Secretin : It is responsible for secretion of, pancreatic juice and bile from presence and, liver., 3. Cholecystokinin CCK/ Pancreozymin PZ, : This hormone stimulates the pancreas to, , 216
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release its enzymes and also stimulates gall, bladder to release bile., 4. Entero-gastrone / Gastric inhibitory, peptide (GIP) : It slows gastric contractions, and inhibits the secretion of gastric juice., , Hormone therapy/ HT : Hormone therapy is, the use of hormones in medical treatment. HT is, applied in Pregnancy, Menopause, Osteoprosis,, Growth hormone deficiency, Insulin Resistance,, Cancer, etc., , Kidney : It produces renin, erythropoietin, and calcitriol (calcitriol is the active form of, vitamin cholecalciferol (D3))., Heart : Atrial natriuretic hormone /ANF., Increases sodium excretion by kidneys and, reduces blood pressure., , Can you tell?, 1. Give significance of relaxin and inhibin., 2. Enlist hormones secreted by GI tract and, state their role., 3. Mention the role of heart and kidney in, hormone secretion., , Do you know ?, Chemicals that operate between members of the same species are social hormones or, pheromones. These are commonly also called sex attractants or external hormones., A pheromone is a volatile substance produced and discharged by an organism, which, induces a physiological response in other organism of the same species. Pheromones are, produced by many species of insects. Some pheromones enhance the chance of mating between, the sexes. These are called signaling pheromones used to induce a behavioral response. Social, insects such as ants make use of signaling pheromones to locate food sources and warn of, danger., Worker bees are females maintained in a sterile state by the pheromone called anti– queen, factor produced by queen. The factor spreads among the workers preventing maturation of, the ovaries of workers as long as the queen is present in the bee hive. Increase in colony size, results in dilution of pheromones and second queen may develop., , Activity :, 1. Categorise given activities into, appropriate type of reflex action., , 2. Prepare concept map of mechanism of, hearing., , Swimming, Dancing, Cycling, Salivation, Blinking of eyes, Sneezing, , 217
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Exercise, Q. 1 Multiple choice questions., 1. The nervous system of mammals uses, both electrical and chemical means to, send signals via neurons. Which part of, the neuron receives impulse?, a. Axon, b. Dendron, c. Nodes of Ranvier d. Neurilemma, 2., , a. skin colour, c. digestion, , 9. Which one of the following is a set of, discrete endocrine gland, a. Salivary, thyroid, adrenal, ovary, b. Adrenal, testis, ovary, liver, c. Pituitary, thyroid, adrenal, thymus, d. pituitary, pancreas, adrenal, thymus, , is a neurotransmitter., a. ADH, b. Acetyl CoA, c. Acetyl choline, d. Inositol, , 10. After ovulation, Graafian, changes into, a. Corpus luteum, b. Corpus albicans, c. Corpus spongiosum, d. Corpus callosum, , 3. The supporting cells that produce myelin, sheath in the PNS are, ., a. Oligodendrocytes, b. Satellite cells, c. Astrocytes, d. Schwann cells, , 7. Hormone thyroxine, adrenaline and nonadrenaline are formed from ---------a. Glycine, b. Arginine, c. Ornithine, d. Tyrosine, 8. Pheromones are chemical messengers, produced by animals and released, outside the body. The odour of these, substance affects, , follicle, , 11. Which one of the following pair correctly, matches a hormone with a disease, resulting from its deficiency?, a. Parathyroid hormone - Diabetes, insipidus, b. Leutinising hormone - Diabetes, mellitus, c. Insulin - Hyperglycemia, d. Thyroxine - Tetany, , 4. A collection of neuron cell bodies located, outside the CNS is called, ., a. Tract, b. Nucleus, c. Nerve, d. Ganglionl, 5. Receptors for protein hormones are, located, a. in cytoplasm, b. on cell surface, c. in nucleus, d. on Golgi complex, 6. If parathyroid gland of man are removed,, the specific result will be, a. onset of aging, b. disturbance of Ca++, c. onset of myxoedema, d. elevation of blood pressure, , b. excretion, d. behaviour, , 12., , is in direct contact of brain, in human, a. Cranium, c. Arachnoid, , b. Duramater, d. Piamater, , Q. 2 Very very short answer questions., 1. What is the function of red nucleus?, 2. What is the importance of Corpora, quadrigemina?, 3. What does the cerebellum of brain, control?, 4. Name the three ossicles of the middle, ear., 5. Name the hormone which is anti abortion, hormone, 6. Name an organ which acts as temporary, , 218
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endocrine gland., 7. Name the type of hormones binding to, DNA and alter gene expression., 8. What is the cause of abnormal elongation, of long bones of arms and legs and of, lower jaw., 9. Name the hormone secreted by the, pineal gland., 10. Which endocrine gland plays important,, role in improving immunity?, Q. 3 Match the organism with the type of, nervous system found in them., 1. Neurons, a. Earthworm, 2. Ladder type, b. Hydra, 3. Ganglion, c. Flatworm, 4. Nerve net, d. Human, Q. 4 Very short answer questions., 1. Describe the endocrine role of islets of, Langerhans., 2. Mention the function of testosterone?, 3. Give symptoms of the disease caused by, hyposecretion of ADH., Q. 5 Short answer questions, 1. Rakesh got hurt on his head when he fell, down from his motorbike. Which inner, membranes must have protected his, brain? What other roles do they have to, play?, 2. Give reason - Injury to medulla oblongata, may prove fatal., 3. Distinguish between the sympathetic and, parasympathetic nervous system on the, basis of the effect they have on:, a. Heart beat b. Urinary Bladder, 4. While holding a tea cup Mr. Kothari’s, hands rattle. Which disorder he may be, suffering from and what is the reason for, this?, 5. List the properties of the nerve fibres., 6. How does tongue detect the sensation of, taste?, 7. State the site of production and function, of Secretin, Gastrin and Cholecystokinin., , 8. An adult patient surffers from low heart, rate, low metabolic rate and low body, temperature. He also lacks alertness,, intelligence and initiative. What can be, this disease? What can be its cause and, care?, 9. Where is the pituitary gland located?, Enlist the hormones secreted by anterior, pituitary., 10. Explain how the adrenal medulla and, sympathetic nervous system function as, a closely integrated system., 11. Name the secretion of alpha, beta, and delta cells of islets of langerhans., Explain their role., 12. Which are the 2 types of goitre? What, are their causes?, 13. Name the ovarian hormone and give, their functions., Q. 6 Answer the following., 1. Complete the table., Location, Cell Type, PNS, , Function, Produce myelin, sheath, , Satellite cells, Oligodendrocytes Form myelin, sheath around, central axon, CNS, Phagocytose, pathogens, CNS, Form the, epithelial, lining of brain, cavities and, central canal., Q. 7 Long answer questions., 1. Explain the process of conduction of, nerve impulses upto development of, action potential, , 219, , PNS, .............., , 2. Draw the neat labelled diagrams of., a. Human ear, b. Sectional view of human eye, c. L. S. of human brain, d. Multipolar Neuron
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3. Answer the questions after observing the, diagram given below., 1 Nerve, , Presynaptic, neuron, , impulse, , 2, , Ca, , a. Growth of thyroid and secretion of, thyroxine., , 2+, , Ca2+, , Voltage-gated Ca2+, channel, , Synaptic end bulb, , b. Helps in relaxing pubic ligaments to, facilitate easy birth of young ones., c. Stimulate intestinal glands to secrete, , Cytoplasm, Synaptic cleft, Ca2+, 3, , Synaptic, vesicles, Neurotransmitter, , Neurotransmitter, receptor, Ligand-gated, channel closed, , 7. Write the names of hormones and the, glands secreting them for the regulation, of following functions., , Na+, , interstinal juice., d. Controls calcium level in the blood, , 4, 5, , Postsynaptic, neuron, , 6 Postsynaptic, , potential, , Ligand-gated, channel open, 7 Nerve, , impulse, , a. What do the synaptic vesicles contain?, b. What process is used to release the, neurotransmitter?, c. What should be the reason for the next, impulse to be conducted?, d. Will the impulse be carried by postsynaptic membrane carried even if one, pre-synaptic neuron is there?, e. Can you name the channel responsible, for their transmission?, 4. Explain the Reflex Pathway with the help, of a neat labelled diagram., 5. Krishna was going to school and on, the way he saw a major bus accident., His heart beat increased and hands and, feet become cold. Name the part of the, nervous system that had a role to play in, this reaction., 6. What will be the effect of thyroid gland, atrophy on the human body?, , e. Controls tubular absorption of water, in kidneys., f. Urinary elimination of water., g. Sodium, and, metabolism., , potassium, , ion, , h. Basal Metabolic rate., i., , Uterine contraction., , j. Heart beat and blood pressure., k. Secretion of growth hormone., l. Maturation of Graafian follicle., 8. Explain the role of hypothalamus, and pituitary as a coordinated unit in, maintaining homeostasis?, 9. What is adenohypophysis? Name the, homones secreted by it?, 10. Describe in brief, an account of disorders, of adrenal gland., 11. Explain action of steroid hormones and, proteinous hormones., 12. Describe in brief an account of disorders, of the thyroid., Project : Prepare animated powerpoint, presentataion to explain mechanisms of, hormonal action., , 220
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Human Health and Diseases, , 10, , Can you recall?, 1. Generally individuals are conscious about, their health. So define health., 2. Define infectious and non infectious, disease? Give their examples., Health does not simply mean ‘absence of, disease’ or physical fitness. In fact, it is difficult, to aptly define health. According to the World, Health Organization, health is defined as the state, of complete physical, mental and social wellbeing and not merely the absence of disease or, infirmity. In short, health is birth right of humans., Health also reflects the metabolic and functional, efficiency of living organisms. Hygiene is a, science of rules of health. To achieve good, health, it is therefore, necessary that we have, hygienic balanced diet, clean drinking water,, personal and community hygiene, regular, physical exercise, knowledge about diseases, and their effect on body, proper disposal of, waste and control of vectors., Everyday we are exposed to various foreign, bodies, including infectious agents like bacteria,, viruses, etc. Despite constant exposure to variety, of pathogens, most of us remain healthy. This is, due to fact that the human body has ability to, resist almost all type of these foreign bodies. The, system which protects us from various infectious, agents, is called immune system. Resistance, is the ability to prevent the damage or disease,, through our defense mechanism., 10.1 Immunity:, The term ‘immunity’ has traditionally, referred to as the resistance exhibited by the, host towards injury caused by pathogens and, their products. However, protection against, infectious diseases is only one of the many, , consequences of immune response, which is, entirely concerned with the reaction of the body, against any foreign antigen., Immunity is in fact the ‘‘freedom’’ or, ‘‘exempt’’. The concept of immunity is, believed to be started by Edward Jenner in, England. He developed cowpox vaccine for, the protection against the attack of small pox, (virus). Immunology is a branch of science, which deals with the study of immune system,, immune responses to foreign substances and, their role in resisting infection by pathogens., The most important characteristic of, immune system is that it distinguishes self, (body’s own cells) and non-self (foreign, molecules or invading cells). So, the immune, system differentiates between the body cells, and the invaders. Any foreign substance, invading body and capable of stimulating an, immune response, is called an antigen. The, protective chemicals produced by immune cells, in response to antigens are called antibodies., A. Types of immunity:, There are two types of immunity as Innate, or Inborn (inherited) immunity and Acquired or, Adaptive immunity., i. Innate immunity or Inborn immunity:, Innate immunity is the resistance to, infections that an individual possesses by virtue, of his or her genetic make-up. It is the natural, (inborn) defense system of the body. It is not, affected by prior contact with microorganisms, or immunization. It is nonspecific, when it, indicates a degree of resistance to infection, in general, or specific where resistance to a, particular pathogen is concerned. One form of, innate immunity comprises the various types of, barriers which prevent entry of foreign agents, into the body., , 221
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a. Epithelial surface :, The intact skin and mucous covering the, body, protect it considerably against invasion, by microorganism(s)., The healthy skin possesses bactericidal, activity due to the presence of high, concentrations of salt in drying sweat., Sebaceous secretions and long chain of, fatty acids have bactericidal and fungicidal, properties. The mucosa of the respiratory tract, has several innate mechanisms of defense. The, nose prevents entry of microorganisms to a, large extent, the inhaled particles being arrested, through hair at or near the nasal orifices. Those, that pass beyond are held by mucus lining the, epithelium and are swept back to pharynx, where they tend to swallowed or coughed out., The cough reflex is an important defence, mechanism of respiratory tract. The mouth is, constantly bathed in saliva which has inhibitory, effect on microorganisms. The acidity of, gastric secretions in the stomach destroys, microorganisms. The flushing action of urine, eliminates bacteria from the urethra. Spermine, and zinc present in semen are antibacterial., , pathogens activates the ‘Complement cascade’, to eliminate pathogens. The interferons are a, class of cytokines (soluble proteins) released, by virally cells infected with viruses and, certain white blood cells to stimulate other cells, to protect themselves from viral infection., c. Cellular factors in innate immunity :, Natural defence against the invasion of, blood and tissues by microorganisms and, other foreign particles, is mediated to a large, extent by phagocytic cells which ingest and, destroy them. Phagocytic cells (discovered, by Metchnikoff in 1882) are grouped as, microphages and macrophages. They remove, foreign particles that enter the body. A class of, lymphocytes called Natural killer (NK) cells is, important in nonspecific defence against viral, infections and tumors., d. Fever :, Increase in the body temperature following, the infection is a natural defense mechanism., It helps to accelerate the physiological, processes to destroy the invading pathogens., Fever stimulates the production of interferon, and helps in recovery from viral infections., e. Acute phase proteins (APPs):, Infection on injury leads to a sudden, increase in concentration of certain plasma, proteins, collectively called acute phase, proteins. These include C Reactive Protein, (CRP), Mannose binding protein, Alpha-1acid glycoprotein, Serum Amyloid P, etc., APPs are believed to enhance host resistance,, prevent tissue injury and promote repair of, inflammatory lesions., , Knowledge Enhancer:, The conjunctiva is freed of foreign, particles by the flushing action of lachrymal, secretions. Eyes become susceptible to, infection when lachrymal secretion is, absent. Tears contain the antibacterial, substance Lysozyme (Ist described by, A. Fleming). This is a thermolabile, low, molecular weight, basic protein which, acts as a muramidase. Lysozyme is active, only against some pathogenic Gram +ve, bacteria., b. Antimicrobial substances in blood and, tissues:, The complement system contains more, than 30 serum proteins, circulating in the blood, in an inactive state. The presence of microbial, , ii. Acquired immunity:, The resistance that an individual acquires, during life is known as “Acquired immunity”., It is also known as Adaptive or Specific, immunity”. It involves the formation of, antibodies in the body, which neutralize the, antigens. Acquired or Adaptive immunity has, the following unique features., , 222
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a. Specificity: It can produce specific, antibody or T-lymphocyte against a, particular antigen/pathogen., b. Diversity: It can recognize a vast variety, of diverse pathogens or foreign molecules., c. Discrimination between self and nonself: It differentiates between own, body cells (self) and foreign (non-self), molecules., , b. Passive immunity:, Passive immunity is acquired when readymade antibodies are received by the body cells., i.e. Body cells do not take any active part in the, production of immunity. Passive immunity can, be acquired either naturally or artificially., 1. Natural Acquired Passive immunity:, Before birth maternal antibodies are, transferred from mother to foetus, through placenta. After birth, antibodies, are transferred from mother to infant, through colostrum (first milk of mother), and continue throughout the period of, breast feeding. The antibodies received, by baby from mother remain in the, body for a short time. Therefore, natural, acquired passive immunity is short lived., , d. Memory: When the immune system, encounters a specific foreign agent for, the first time, it generates an immune, response and eliminates the invader. This, is called first encounter. The immune, system retains the memory of the first, encounter. As a result, a second encounter, with same pathogen brings about quicker, and stronger immune response., , 2. Artificially, Acquired, Passive, immunity: This immunity is developed, by injecting previously prepared, antibodies using serum from humans or, animals. For e.g. Antibodies obtained, from hyper immunised horses are, injected to humans against rabies, pathogens. It is short lived., , Types of Acquired Immunity:, Acquired immunity is of two types Active, and Passive., a. Active immunity:, It is the resistance developed by, individuals as a result of an antigenic stimulus., It also known as “Adaptive immunity”. Active, immunity may be natural or artificial., 1. Natural Acquired Active immunity:, Immunity acquired due to infection is, called natural active immunity. It is, developed after entry of pathogens in, the body. It is long-lasting immunity. e.g., person who has recovered from attack of, measles develops natural acquired active, immunity to measles, for the life time., 2. Artificial Acquired Active immunity:, It is the resistance induced by vaccines., Vaccine is introduced into the body to, stimulate the formation of antibodies by, the immune system. e.g. Polio vaccine,, BCG vaccine etc. such immunity may be, temporary or permanent., , B. Cells of Immune System:, There are two main types of cells involved, in the working of Immune system. They are (a), Lymphocytes and (b) Antigen Presenting cells., a. Lymphocytes:, Lymphocytes are the main cells of the, immune system. They, like the other blood, corpuscles, arise from the stem cells, the, haemocytoblasts, present in liver of the foetus, and in the bone marrow in adult. Some of, them undergo differentiation in the gut –, associated bursal lymphoid tissues (Tonsils,, Peyer’s patches) and are called Bursal or Blymphocytes; others are differentiated in the, thymus gland and are termed as T-lymphocytes., The mature lymphocytes pass into body fluids, (blood and lymph) and circulate in the body., , 223
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Many of them stay in the lymph nodes. The Blymphocytes and T-lymphocytes form humoral, or antibody-mediated immune system (AMIS), and cell-mediated immune system (CMIS), respectively. Both the immune systems need, antigens to come into action, but they respond, in different ways., Mechanism of response of T-lymphocytes to, antigens: On coming in contact with an antigen,, a T-lymphocyte forms clones of T-cells which, are similar but they perform different functions., The clone has four types of T-lymphocytes:, i., , Helper T-cells: Sensitized helper T-cells, produce lymphokines for performing, several types of functions like proliferation, of other T-cells, stimulation of Blymphocytes, macrophages, etc., ii. Killer T-cells or Cytotoxic T-cells: They, directly attack and destroy invading, microbes, infected body cells and cancer, cells. Killer T-cells bind to infected cell, and secrete perforins. Then perforins form, a hole in infected cell. It also releases, substances that kill the cell, hence the name, cytotoxic T-cell., iii. Suppressor T-cells: These cells suppress, entire immune system against attack on the, own body cells., iv. Memory T-cells: These are previously, sensitized cells which retain the, sensitization memory for long time in the, future., Mechanism of action of B-lymphocytes to, antigens:, B–lymphocytes are sensitized directly, by both antigens as well as by helper T-cells., Activated B-lymphocyte multiplies very fast, to produce clone of plasma cells and memory, B-cells. The plasma cells produce specialized, glycoproteins, called antibodies which are, circulated through body fluids (humor) like, blood and lymph. The antibody molecules may, bind to a cell membrane or they remain free., , The free antibodies have three main, functions:, i. Agglutination of particulate matter,, including bacteria and viruses. The, immobilized mass is then engulfed by, phagocytes., ii. Opsonisation or coating of bacteria to, facilitate their subsequent phagocytosis by, macrophages., iii. Neutralization of toxins released by, bacteria e.g. tetanus toxin., Each antibody is specific for a particular, antigen., b. Antigen Presenting cells:, Antigen presenting cells engulf invading, pathogens and process the antigens. Then, the processed antigens are presented on their, own surface. These cells are able to deliver, a stimulatory signal that is necessary for, activation of helper T-cell., 1., , Can you tell?, , Which is kind of immunity provided, by vaccination?, Can you recall?, 1. Why are vaccines considered as antigen, containing material?, 2. How are vaccines produced?, 3. Who was Edward Jenner?, C. Vaccination :, Administration of vaccine (i.e., inactivated pathogen or antigenic protection, of particular pathogen) to protect against a, particular pathogen, is called vaccination., The body’s immune system helps to, protect against pathogens that cause infection., It’s an efficient system, most of the time,. It, either keeps microorganisms out or tracks them, down and gets rid of them. However, some, pathogens can overwhelm the immune system., When this happens, it can cause serious illness., The pathogens most likely to cause problems,, are the ones the body doesn’t recognize., , 224
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Vaccination is a way to “teach” the immune, system as to how to recognize and eliminate, pathogenic organism. That way, body is always, prepared if you are ever exposed., Vaccination is an important form of, primary prevention, that can protect people, from getting sick. Vaccination has allowed us, to control diseases like measles, polio, tetanus, and whooping cough that once threatened, many lives. It’s important that as many people, as possible get vaccinated. Vaccinations don’t, just protect individuals, when enough people, are vaccinated. It also helps to protect the, society., , Vaccinations are safe:, Vaccines are considered to be safe. They, are rigorously tested and go through many, rounds of study, examination, and research, before they are used for the general public., Extensive research and evidence shows, that vaccines are safe their side effects are rare, and typically mild., Internet my friend, 1. Whether vaccination can be done during, or before pregnancy?, 2. Will it be helpful to protect the mother, and baby both?, 3. Which vaccines can be administered, before pregnancy? When can it be?, 4. How will you increase awareness in the, society on this issue?, , Do you know ?, How does vaccination work?, Healthy immune system defends against, invaders. Immune system consists of several, types of cells. These cells defend against, harmful pathogens. However, they have to, recognize an invader. Vaccination teaches, the body to recognize new pathogens causing, diseases. It stimulates the body to make, antibodies against antigens of pathogens., It also primes immune cells to remember, the types of antigens. This allows a faster, response to the pathogen in future., Vaccines work by exposing you to a safe, version of pathogen. Vaccines may be in the, form of:, • A protein or sugar from the pathogen., • A dead or inactivated form of a pathogen., • A toxoid containing toxin produced by a, pathogen., • A weakened (attenuated) pathogen., When the body responds to the vaccine,, it builds an adaptive immune response. This, helps to equip the body to fight off an actual, infection., , 10.2 Structure of Antibody:, Antibodies are glycoproteins which are, highly specific to specific antigens. They, are also known as Immunoglobulins (Igs),, produced in response to antigenic stimulation., Antibodies are produced by plasma cells which, in turn are formed by B–lymphocytes. The, mature plasma cells produce antibodies at an, extremely rapid rate i.e. about 2000 molecules, per second., Antigen binding site Variable region of, the heavy chain, N, , N, , Antigen, binding site, N, N, , Light chain, , Variable, region of the, light chain, , -s-s-s-s-, , C, , C, , Hinge, , Disulfide, bond, , Heavy chain, , Constant, region of the, light chain, , Constant region of, the heavy chain, , Internet my friend, C, , Find out different types of vaccines available, in the market and their significance., , C, , Fig. 10.1 : Structure of antibody, 225
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Structure:, Antibody is a ‘Y’ shaped molecule. Each, immunoglobulin molecule is made up of four, polypeptide chains. There are two heavy or Hchains and two light or L-chains. The four, polypeptide chains are held together by, disulfide bonds (-s-s-) to form a ‘Y’ shaped, structure. The region holding together arms, and stem of antibody, is termed as hinge. Each, chain of the antibody includes two distinct, regions, the variable region and the constant, region. Variable regions constitute the antigenbinding site (paratope). This part of antibody, recognizes and binds to the specific antigen to, form an antigen-antibody complex. Since most, antibodies carry two antigen binding sites, they, are said to be bivalent., , •, , Find out, , Collect information about IgG, IgA,, IgM, IgD and IgE antibodies from internet /, reference book / teacher and prepare a chart /, power point presentation., Formation of antigen-antibody complex:, Study of antigen-antibody interactions is, called serology. Each antibody is specific for a, particular antigen. Combining sites of antigen,, called antigenic determinants (epitopes) react, , with the corresponding antigen binding sites, of antibodies called paratopes. The antigen, binding sites (paratopes) are located on, the variable regions of the antibody. Small, variations in the variable regions make each, antibody highly specific for a particular, antigen. The variable region enables the, antibody to recognize the specific antigen, and bind to specific antigen in a lock and key, manner forming an antigen-antibody complex., Antigen on Blood Cells:, There are several known antigens on, the surface of human red blood cells. These, antigens give rise to different blood groups., There are many genetically determined blood, groups system like ABO, Rh, Duffy, Kidd,, Lewis, P, MNS, Bombay blood group, etc., ABO Blood Groups:, The A, B and O blood groups were, discovered by Karl Landsteiner in 1900. Later, on, the blood group AB was discovered by, Landsteiner’s students Decastello and Sturli, in 1902. Landsteiner was awarded the Nobel, prize for his discovery of human blood groups., He found two antigens or agglutinogens on, the surface of human red blood cells and, named them as antigen A and antigen B. He, also noticed the corresponding antibodies or, agglutinins in the serum called ‘a’ and ‘b’., , Antigen determinants (Epitopes), Paratopes of antibodies, bound to epitopes, , Antigen, Antigen, Virus, Globular, proteins, , Fig. 10.2 : Formation of antigen- antibody complex, 226
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Table 10.3 : ABO Blood groups in man, Blood group, A, B, , Genotype, IA IA or, IA IO, IB IB or, IB IO, IA IB, , AB, (universal acceptor), O, IO IO, (universal donor), , Antigen on, Antibody in, Surface of RBC, Serum, A, Antibody b, , Can donate Can receive, blood to blood from, A, AB, A, O, , B, , Antibody a, , B, AB, , B, O, , A and B, , Nil, , AB, , A, B, AB, O, , Nil, , Both Antibody a A, B, AB, O O, and Antibody b, , In ABO system, the blood groups are, determined by the presence or absence of, antigen A and antigen B, the blood group of, person is classified into four groups A, B, AB, and O., Blood group A : Individuals, with blood group, ‘A’ have the antigen A on the surface of their, red blood cells (RBCs) and antibody ‘b’ in their, plasma., Blood group B : Individuals with blood group, ‘B’ have the antigen B on the surface of their, RBCs and antibodies ‘a’ in their plasma., Blood group AB : Individuals with blood, group ‘AB’ have both antigens A and B on the, surface of their RBCs and no antibodies in their, plasma., Blood group O – Individuals with blood group, ‘O’ lack both antigens A and B on the surface, of their RBCs and show presence of both ‘a’, and ‘b’ antibodies in their plasma., , Rh (D) antigen induces a strong, immunogenic response when introduced, into Rh-ve individuals. Rh blood group is an, important factor in blood transfusion and is, involved in haemolytic diseases of the newborn, (HDN), which is called erythroblastosis, foetalis (destruction of the erythrocytes of the, foetus). It occurs when an Rh -ve mother, conceives Rh+ve foetus., The Rh +ve RBCs from the foetus may, enter the mother’s circulatory system during, child birth, causing her to produce anti-Rh, antibodies. As a result, subsequent Rh+ve, foetuses will be exposed to the anti-Rh, antibodies produced by mother, which result in, HDN. In order to prevent HDN, Rh -ve mother, is injected with the anti-Rh antibody during all, pregnancies carrying Rh +ve foetus., , Rh factor:, Rh is the most complex of the blood group, system. Rh –factor is an antigenic protein, present on the surface of the red blood cells in, the human beings. It was first discovered by, Landsteiner and Wiener (1940), on the surface, of RBCs of Rhesus monkey, so it is called Rhfactor (also called D antigen). Person having, Rh factor (D antigen) are called Rh positive, (Rh +ve) and those lacking D antigen are called, Rh negative (Rh -ve)., 227, , Can you tell?, 1. The blood group of Krutika is O Rh +ve., What would be the possible blood groups, of her parents?, 2. Mrunmayi is called as universal blood, acceptor. What is her blood group?, , Use your brain power, Can a person with blood group O Rh+ve, donate blood to a patient with blood group O, Rh-ve? Why?
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10.3 Common Human Diseases:, Disease is defined as condition of disturbed, or deranged functioning of one or more organs, or organ systems of the body, caused due to, infections, defective diet or heredity. All human, diseases can be broadly categorized into, congenital diseases and acquired diseases., Congenital diseases are present from, birth; may be caused by genetic abnormality, or metabolic disorder. They may be permanent, and were practically incurable. However,, modern research has helped to cure some, inborn diseases through gene therapy, enzyme, replacement therapy, etc., Acquired diseases develop after the birth, and can be subdivided into (a) Communicable or, infectious diseases or (b) Non- Communicable, or Non-infectious diseases., The diseases which are transmitted from, infected person to another healthy person, either directly or indirectly, are known as, Communicable or Infectious diseases. Malaria, and other diseases which are to be studied in, this chapter, are examples of this type., , Many pathogens use another organism,, the ‘Vector’ to reach us. These vectors are, actually parasites which we regularly come, across. Parasite is an organism that lives in or, on the body of another organism and derives its, nutrition from that of host organism. Parasites, are two catagories viz. : 1. Ectoparasite E.g., bedbug 2. Endoparasite. E.g. Plasmodium, is a protozoan endoparasite of the mosquito, (vector) and human beings., A. Malaria :, It is a vector (mosquito) borne infectious, disease caused by protist - Plasmodium., There are four species of Plasmodium as, P. vivax , P. ovale, P. malariae, P. falciparum., Only P. falciparum causes serious illness while, others are rarely fatal. Based on the species,, there are 4 - types of malaria., Signs and symptoms of malaria :Symptoms of malaria begin to appear, about 7 to 15 days after the bite of infective, mosquito., , • Initial symptom are fever, headache, and, chills, may be difficult to recognize as, malaria., The diseases that cannot be transmitted, • Classical symptoms of malaria is cyclic, occurrence of high fever followed by, from infected person to another healthy one, sweating and sudden shievering. Such, either directly or indirectly are known as, entire episode lasts for four to six hours, Non- Communicable or Non - Infectious, and recurs every two days or three days., diseases. Cancer and deficiency diseases are, • Vomiting and convulsions., examples of this type., • Arthralgia ( joint pain), aneamia due to, Communicable diseases are caused by, rupturing of RBCs., pathogens like viruses, bacteria, fungi, helminth, • Haemoglobinuria, hepatomegaly (liver, worms, etc. All the disease causing organisms, enlargement)., are called ‘Pathogens’., • Retinal damage (eye)., • Cerebral malaria (brain infection)., Table 10.4 : Table showing different species of Plasmodium, Species of Plasmodium Incubation period Pattern of high fever, P. vivax, , 14 days, , High fever after 48 hr interval, , P. malariae, , 28 days, , High fever after 72 hr interval, , P. ovale, , 17 days, , High fever after 48 hr interval, , P. falciparum, , 12days, , High fever at irregular intervals between 22-48 hrs, 228
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Human skin, , Cycle in Mosquito, , Hepatic cell, , Sporozoites, (to salivary gland), , Cycle in Human, Hypnozoite, (hepatic dormancy), , Bursting oocyst, , Mature schizont, Merozoites, , Oocyst, , Erythrocyte, , Mosquito midgut, , Ookinete, , Trophozoite, , Zygote, , Ruptured, erythrocyte, , Macrogamete, , Erythrocytic, schizont, Newly infected, Erythrocyte, , Microgamete, , Gametocyte, , Fig. 10.5 : Stages in the life cycle of Plasmodium in mosquito and human, Mode of transmission :, Plasmodium is transmitted from one, person to other through an insect vector- female, Anopheles mosquito., When infected female Anopheles sucks, the human blood, it may transfer sporozoites, to human circulation. Sporozoites reproduce, asexually through fission (schizogony) in the, liver cells or erythrocytes. The cells formed, are now called merozoites. The cells formed, within erythrocytes function as gametocytes, (gamogony). Besides, it forms gametocytes, within erythrocytes (gamogony)., Gametocytes if taken up by female, Anopheles, fertilization occurs in its gut., Diploid zygote is formed which transforms into, oocyst. Oocyst forms large number of haploid, sporozoites through meiosis (sporogony)., Sporozoites migrate to salivary glands and are, ready to infect new human host., , Treatment of malaria includes Artemisinin, based combination therapies (ACTs). WHO, has recommended 5 different ACTs which, includes various combinations of artesunate,, sulfadoxine, pyrimethamine, etc. In addition,, quinine is also used., , Diagnosis and Treatment :, Malaria can diagnosed by microscopic, study of blood smear. Besides, other rapid, diagnostic tests based on nucleic acid, amplification techniques are also used., , B. Amoebiasis :, • Amoebiasis is also known as Amoebic, dysentry. It’s a common infection of human, gastro-intestinal tract, which affects 15 %, population of India., , Prevention and Control :, Prevention of mosquito bite by using, mosquito nets and insect repellents., Spraying insecticides and draining, stagnant water where mosquito lays eggs., Mosquito larve can be controlled by using, Gambusia fresh water fish (biocontrol)., Always Remember, The time interval from the invasion of, a pathogen to the development of clinical, manifestations, is known as Incubation, period., , 229
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• Amoebiasis is caused by a protist parasiteEntamoeba histolytica., Amoebulae Ectoplasm, , Prevention and Control : Wash hands with hot, water and soap after using toilets and changing, baby’s diaper., , Pseudopodium, , Drink boiled water. Otherwise, water, must be chlorinated and filtered. Avoid eating, unhygenic food. Vegetables must be properly, washed and cooked. Proper sanitary facilities, including sewage disposal help in prevention., , Endoplasm, , Division, , Metacystic, Amoeba, , Food vacuoles, Ingested, R.B.C., Nucleus, , Internet my friend, , Endosome Trophozoite, , Gather information about tropozoite, and its occurrence in the life cycle of other, parasitic protozoans., , Binary division, Excystment, Precystic form, , Cyst, wall, Glycogen, vacuoles Nucleus, , Endosome, , Chromatoidal, body, , C. Ascariasis :, It is an infectious disease of human, intestinal tract, caused by roundworm- Ascaris, lumbricoides.Ascaris lumbricoides is an, endoparasitic round worm or nematode., , Chromatoid, bodies, Cyst, , Binucleate cyst, , Quadrinucleate cyst, , Fig. 10.6 : Life cycle of Entamoeba histolytica, Signs and symptoms:, • Diarrhoea, flatulence, stool with mucus and, abdominal pains (cramps) are common., • Passing of blood with stool is common in, severe cases., • Hepatomegaly occurs if parasite enters the, liver. Liver develops amoebic liver abscess, accompanied with fever and pain in right, abdomen., Mode of transmission :, • Faeco-oral route., • Eating with dirty hands., • Contaminated food and water., Diagnosis and Treatment : Diagnosis of, amoebiasis is made through microscopic, examination of the stool sample., Amoebiasis is treated by the use of, Metronidazole and Tinidazole which can, destroy the E. histolytica in the digestive tract, as well as other tissues., , Signs and symptoms :, • Gastro-intestinal discomfort accompanied, with vomiting and fever., • Presence of live worms in feacal matter., • Pulmonary disorders occur in some, patients. Pneumonitis (inflammation in, alveolar wall)., • Loss of apetite and weight loss., • Eosinophilia (number of eosinophils is, increased)., Mode of transmission: Food and drinks, contaminated with the eggs of these worm is, the main mode of transmission. Eggs hatch, inside the intestine of the new host. The larvae, pass through various organs and settle as adults, in the digestive system., Diagnosis and Treatment: Diagnosis can be, done by microscopic examination of the stool., Anti-helminthic drugs like Piperazine,, Mebendazole, Levamisole, Pyrantel are, effective against Ascaris lumbricoides., , 230
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D. Filariasis/ Elephantiasis :, Filariasis is caused by thread like wormsnematodes. These nematode parasites are, transported from person to person via mosquito, bite. Filariasis can be divided into 3 subtypes, as 1) Lymphatic Filariasis, 2) Subcutaneous, Filariasis (e.g. Loa loa, Mansonella spp.) and, 3) Serous (abdominal)cavity Filariasis (e.g., Mansonella spp.)., , Swallowing, by man, Contaminated food, , Intestine, , Infective larva, develops within the, eggs, , Blood, , Soil, Heart, Fertilized eggs in, faeces, , Lymphatic Filariasis (Elephantiasis) is caused, by the worms - Wuchereria bancrofti, Brugia, malayi, Brugia timori., , Lungs, , Adult, Trachea, Adult worms, in intestine, Intestine, Oesophagus, , Pharynx, , Fig. 10.7 : Life cycle of Ascaris lumbricoides, Prevention and Control : Avoiding defaecation, in open space, prevents the spread of Ascaris., Personal hygienic habits like washing hand, with water and soap after using toilet are, also important. Washing vegetables throughly, before cooking and avoiding raw vegetables is, important for prevention of ascariasis., , 1 Mosquito takes a blood meal, (L3 larvae enter skin), , Mosquito Stages, , 8, , Signs and symptoms :• Edema with thickening of skin and, underlying tissue., • Wuchereria bancrofti affects the legs,, arms, breasts, scrotum, etc., • In lymphatic filariasis, worms infect, lymphatic system and causes enlargement, of lymph vessels and nodes. This is, elephantiasis i.e. limbs are swollen like, legs of elephant., • Lymphedema i.e. accumulation of lymh, fluid in tissue causing swelling., Human Stages, , Migrate to head and, mosquito’s proboscis, , 7 L3 larvae, Infective Stage, , 2 Adults in lymphatics, , Two moultings, , 6, L1 larvae, , 5, , Microfilariae, pentrate, mosquito’s midgut, and, migrate to thoracic muscles, , 4 Mosquito takes a blood, meal (ingests microfilariae), , 3 Adults produce sheathed, microfilariae that migrate into, lymph and blood channels, , Diagnostic Stage, , Fig. 10.8 : Mode of transmission - Filariasis (Wuchereria bancrofti), 231
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•, , Hydrocele i.e. testis are enlarged due to, accumulation of lymphatic fluid in testis., , Mode of transmission : Wuchereria bancrofti, is transmitted to human body by female Culex, mosquito., The larvae escape mosquito body and, arrive on the human skin. They penetrate, the skin, undergo two moultings before they, become adults and settle in the lymphatic, system. Incubation period can be as long as 816 months., Diagnosis and Treatment : Use of diethyl, -carbamazine citrate twice a day for three, weeks and thereafter for five days every six, month is effective against filarial worms., Prevention and Control : Avoid mosquito bite, by using mosquito nets and insect repellents., Eradication of mosquitoes is essential for, control of filariasis., E. Typhoid :, Typhoid is an acute infection of intestine., It is caused by Salmonella typhi. It is Gram -ve, bacteria found in intestinal lumen of infected, preson. Pathogenicity is due to “O”- antigen,, a lipopolysaccharide (LPS), present on surface, coat. Flagella contains “H”- antigen., Signs and Symptoms :, • Prolonged fever as high as 1040F., • General nausea, fatigue, headache., • Abdominal pain, constipation or diarrhoea., • Rose-coloured rash on skin., • White coat on tongue, cough., • Anorexia (loss of apetite)., • If not treated- breathlessness, irregular, heartbeats, haemorrhage., , Capsule (K antigen, or, vi in Salmonella), Somatic (O antigen,, or cell wall antigen), Flagella (H antigen), , Fig. 10.9 : Salmonella typhi, Diagnosis and Treatment :- Widal test is used, for diagnosis of typhoid. Treatment of typhoid, involves surgical removal of gall bladder in, severe cases. Antibiotics like Chloromycetin is, helpful treatment., For prevention of typhoid WHO, recommendes two vaccines as, oral, (Ty21a vaccine) and injectable (Typhoid, polysaccharide vaccine) sold as- typhim vi and, typherix., F. Pneumonia :, Pneumonia is an inflammatory condition, of lungs or alveoli of lungs. It is caused by a, variety of pathogens which may be viruses like, influenza virus, adenovirus, para influenza, and Respiratory Syncytial Virus (RSV) or, bacteria like Streptococcus pneumoniae or, fungal pathogens e.g. Pneumocystis jirovecii, and Pneumocystis carinii. Pneumonia can also, be caused by chemical burns or physical injury, to lungs., Signs and Symptoms :-, , Mode of transmission :, • It is a food and water borne disease., •, , •, , Insects like housefly and cockroaches, feeding on fecal matter, may transfer the, bacteria to food material., Poor hygiene habits and poor sanitation, conditions are responsible for the spread, of typhoid., , •, , Cough produces yellow or greenish, sputum or phlegm., , •, , High fever., , •, , Shortness of breath (Dyspnea)., , •, , Chest pain during deep breath or coughing., , •, , Loss of appetite, fatigue, headaches,, vomiting, joint pains and muscle aches., , Mode of transmission : Pneumonia mostly, spreads by direct person to person contact., , 232
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It can also spread via droplets released by, infected person or even by using shared clothes, and utensils., Diagnosis and Treatment :- Course of, treatment depends upon pathogen leading, to the disease. For bacterial pneumonia,, antibiotics like Benzyl penicillin, Ampicillin, and Chloramphenicol are effective., , Adenovirus, , Legionella, pneumophila, , Signs and Symptoms :, • Cough , sore throat, running nose and, fever., • Nasal congestion, sneezing., • Conjunctivitis (red eyes), • Muscle rashes, fatigue, headache,, shivering and loss of appetite., Prevention and Control :, • Staying away from person suffering from, common cold., • Washing hands with soap and water., • Use of handkerchief to cover the nose and, mouth during coughing and sneezing., • Alcohol based hand sanitizer can also be, used., Can you tell?, , Streptococcus, pneumoniae, , Why do we suffer from common cold, repetatively in our life, but other viral diseases, like Influenza or Small pox only once?, , Aspergillus, (mould), , Fig. 10.10 : Pneumonia -Infectious agents, Prevention and Control :• Vaccination is important prevention in, both children and adults., • Vaccines against Haemophilus influenzae, and Streptococcus pneumoniae in first, year of life, help greatly to reduce the, chances of causing Pneumonia., Internet my friend, Find out other modes of infection by, which a pathogen spreads from person to, person., G. Common Cold :, It is a viral infectious disease of upper, respiratory region. It is also known as, nasopharyngitis, acute viral rhinopharyngitis,, acute coryza or a cold ., It is caused by a group of viruses known as, Rhinoviruses and Coronaviruses., , H. Ring Worm (Dermatophytosis) :, It is fungal infection of skin. It is caused, by many fungal species belonging to the genera, Trichophyton and Microsporum. These fungi, feed on keratin in skin, hair and nails., Signs and Symptoms :, • Infected skin shows enlarged, red ring, caused due to ringworm., • Appearance of dry, scaly lesions on various, parts of the body. These red patches cause, intense itching., • Infection to nails is termed as, onychomycosis, in which nails become, thick, discoloured and disfigured., • Athlete’s foot is the fungal infection that, usually begins between the toes., Mode of transmission :- Ringworm spreads by, sharing of clothes, comb of infected person, etc., Close contact with infected person is another, mode of infection., Diagnosis and Treatment: Diagnosis is by, physical examination and treatment uses drugs, like nystatin, fluconazole, itraconazole, etc., , 233
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The fungus lives on, dead tissue of the skin, , i.e. tumor. When tumor is malignant, it is, described as cancer and has ability to invade, other tissues., , Microscopic, ringworm, , Cancer harms the body when cancerous, cells divide uncontrollably to form new lumps, or masses of tissue called neoplasm (except, in the case of leukemia). Tumors can grow, and interfere with the normal functioning of, various organs. They also release secretions, which alter body function(s)., , Fungal, hyphae, Ringworm, lesion, , Fig. 10.11 : Ring Worm, Prevention and Control :, Avoid close contact, sharing of clothes,, sport equipments. Washing clothes in hot water, with fungicidal soap help to destroy fungal, pathogen., I. Dengue :, Dengue fever is a painful, debilitating, vector borne disease, caused by any one of four, closely related dengue viruses. Dengue virus is, transmitted through the bite of female Aedes, mosquito. The mosquito takes up the dengue, virus when it sucks blood of a person suffering, from dengue. It can not spread directly from, one person to another person., Can you tell?, 1. Which are the diseases that can be, avoided by eradication of mosquitoes in, your area?, 2. What are the various ways in which, mosquitoes can be eradicated from any, area?, 3. What precautions will you take if you, are travelling in an area which has lot of, mosquitoes?, , It is one of the main killer diseases, nowadays. Physicians and researchers who, specialize in the study, diagnosis, treatment and, prevention of cancer are called oncologists., Tumors may develop anywhere in the, body. However, all tumors are not cancerous., There are two types of tumors: benign or, nonmalignant and cancerous or malignant., 1. Benign or Nonmalignant Tumor :, It grows slowly, may attain quite a large, size, but it remains restricted to the site of its, origin (localized) and does not spread to other, part of the body. This does not necessarily mean, that the benign tumors are not troublesome., Some benign tumors are harmful and fatal, e.g. brain tumor (A brain tumor may cause, death because the brain is squeezed against the, hard skull). Moreover, the benign tumors may, sometimes become malignant. e.g. Adenoma, and Fibroid., 2. Malignant tumor or cancer :, The growth rate of this tumor is rapid and, mortality rate is comparatively more than, benign tumor. Rapid growth of tumors causes, overcrowding and disruption of normal cells., The cancerous cells compete with the normal, cells for nutrients and finally kill them., , J. Cancer:, Abnormal, uncontrolled and purposeless, division of cells may lead to the formation/, development of mass of undifferentiated cells, , These cells are spread from one organ to, other via blood or lymph and form new tumors, called secondary tumors. This migratory, process is called metastasis., , 234
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Benign, , Malignant, , Normal tissue, cells, , Normal tissue, cells, , Connective, tissue capsule, Cancer cells, Abnormal cells, , Fig. 10.12 : Benign and Malignant Tumor, a. Types of Cancer:, There are five main types of cancers, according to the type of tissue affected. Cancers, are named according to the tissue from which, they arise., i. Carcinoma: Cancer that arise from, epithelial tissue covering or lining the, body organs is known as carcinoma. It, include breast cancer, lung cancer, cancer, of stomach, skin cancer. etc., ii., , Sarcoma: Cancer that arises from, connective tissue is called sarcoma. It, include bone tumors (osteosarcoma),, muscle tumors (myosarcoma), cancer of, cartilage (chondrosarcoma) and cancer, of adipose tissue (liposarcoma)., , v. Adenocarcinoma:, Adenocarcinoma, cancer arises in thyroid, pituitary adrenal, and other glandular tissues., •, , Find out, , Collect information about different, types of lymphoma and hereditary cancer, syndromes., b. Causes of Cancer:, Although, it is still not very clear as to how, the cancer is caused, several factors are now, known to be cancer- causing i.e. carcinogenic., These factors are as follows., , iii. Lymphoma: Cancer that arises from, lymphatic tissue, is called lymphoma. It, occurs in the lymphatic nodes, spleen and, tissues of immune system., , i., , iv. Leukemia: It is a type of blood cancer, in which there is excessive formation of, white blood cells (WBCs) or leucocytes, in the bone marrow. People suffering, from leukemia have very high leucocyte, count. The blood contains millions of, abnormal immature WBCs or leucocytes, that are incapable of fighting infections., There are various types of leukemia such, as monocytic leukemia, lymphoblastic, leukemia etc., , Chemicals : Several chemicals are known, to induce cancer. These include nicotine,, caffeine, products of combustion of coal, and oil. Several polycyclic hydrocarbons,, some sex hormone and steroids, if, given or secreted in large amounts, may, cause cancer. Breast cancer seems to, have hormonal relationship. It is more, commonly observed in women who avoid, breast feeding., , ii. Radiation : The x-rays, gamma-rays, cosmic rays, ultra-violet rays etc. are, carcinogenic. Incidence of skin cancer is, higher in the people working in very sunny, areas due to UV radiation in the sunlight., , 235, , iii. Viruses : Viruses causing cancer have, genes called viral oncogenes (v-onc genes).
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These viruses are also called oncogenic, viruses. e.g. EBV(Epstein-barr virus), HPV, (Human papiloma virus) etc., iv. Oncogenes : Several genes, called, cellular oncogenes (c-onc genes) or protooncogenes have been identified in normal, cells which when activated under certain, condition could lead to oncogenic, transformation of cells., v. Addiction : Different types addictions, likes smoking, chewing of tobacco lead to, cancer of mouth, lips and lungs. Alcohol, consumption may result in cancer of, oesophagus, stomach, intestine and liver., Drugs also cause cancer e.g. Marijuana,, anaerobic steroids etc., Try This, 1. Find the Oncocenters nearby your area., 2. Prepare a chart of types of cancer and, their preventive measures., 3. Organize a street-play on awareness, about cancer and present it in your area., Table 10.13 : Carcinogens and Organ, Affected, Carcinogen, Organ affected, Soot, Skin, lungs, Coal tar (3,4, Skin, lungs, benzopyrene), Cigarette smoke, Lungs, (N-nitrosodimethlene), Cadmium oxide, Prostate gland, Aflatoxin (a metabolite Liver, of Aspergillus flavus, a, mould), 2-naphthylamine and, Urinary bladder, 4-aminobiphenyl, Lungs, Mustard gas, Nickel and chromium, Lungs, compounds, Asbestos, Lungs, Diethylstilbestrol (DES) Vagina, Liver, Vinylchloride (VC), , c. Treatment of Cancer:, Cancer treatment consists of combination, of a number of therapies which are follows:, i., , Chemotherapy: Chemotherapy comprises, administration of certain anticancer drugs., The anticancer drugs check cell division, by inhibiting DNA synthesis or are more, toxic to cancerous cell than to normal, cells. Chemotherapy may lead to hair loss, or anaemia but both get corrected after the, treatment is stopped., ii. Radiotherapy: It is used in addition to, chemotherapy. In radiotherapy, the basic, principle is to bombard the cancerous tissue, or cells with the rays from radioactive, materials. For treatment, the cancer tissue, or cells are exposed to radiations from, radioactive materials such as cobalt,, iridium and iodine. The rays x-rays, gamma rays and charge particles are used, to destroy the cancerous tissue or cells but, cause minimum damage to the surrounding, normal tissue or cells., iii. Surgery: In surgery, the entire cancerous, tissue or cells are removed surgically. It, has limited utility. In certain cases such as, breast tumor or uterine tumor, the surgery, is most effective, but other treatments are, also given to kill any cancerous cell that, may have been escaped in surgery., iv. Immunotherapy: Tumor cell have been, shown to avoid detection and destruction, by immune system. Therefore, the patients, are given substances called biological, response modifiers such as α-interferon, which activates their immune system and, helps in destroying the tumor., v. Supportive therapy: Supportive therapy, is used to treat symptoms of cancer and, side effects of cancer treatments. Objective, of this therapy is to improve the quality of, life of cancer patient. This therapy varies, depending upon condition of individual, patient., , 236
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Over the matrix protein layers there is, an additional layer of lipids. Impregnated, with glycoprotein GP120 and GP 41, (Refer Fig. 10.14). The virus replicates in, actively dividing T4 lymphocytes and can, remain in a latent state/stage in the lymphoid, cells. The virus has unique ability to destroy, human T4 lymphocytes ., HIV is found in greatest concentration in, blood, semen and cerebrospinal fluid (CSF), and to lesser extent in tears, milk, urine, saliva,, cervical and vaginal secretions., , Do you know ?, The Tata Memorial Hospital is, situated at Khargar (Mumbai), Maharashtra, in India. It is a special cancer treatment and, research centre, closely associated with the, Advanced Centre for Treatment, Research, and Education in Cancer. It is recognized as, one of the leading cancer centres in South, Asia. It is an autonomous body funded and, controlled by Department of Atomic Energy,, Government of India which also oversees the, administration of Institute since 1962., , Gp120, , RNA, , Gp 41, , Matrix, proteins, (outer), Lipid, coat, , K. AIDS :, AIDS, the acquired immuno deficiency, syndrome, is a usually fatal illness caused, by a retrovirus (ss RNA) known as the, human immuno deficiency virus (HIV), which weakens the body’s immune system,, leaving the victim vulnerable to life –threating, opportunistic infections, neurological disorders, and unusual malignancies. AIDS can be called, a modern pandemic (world wide), affecting, both industrialized and developing countries., AIDS was first noticed in USA in 1981., In India, first confirmed case of AIDS was in, April 1986 from Tamil Nadu., Structure of HIV:, HIV is 100 to 140 nm in diameter. It, is spherical. Virus particle shows centrally, located two ss RNA molecules along with, reverse transcriptase enzymes. It is covered, by two layers of proteins. The outer layer is, of matrix protein (p17) while in inner layer is, capsid protein (p24)., , Capsid, Reverse proteins, transcriptase (inner), , Fig. 10.14 : Structure of HIV, The virus can be transmitted through :, Unsafe sexual contact: Including oral,, vaginal and anal sex., Blood : Via blood transfusions or needle, sharing., From mother to child (Transplacental):, A pregnant woman can transmit the virus, to her foetus through their shared blood, circulation, or a nursing mother can, transmit it to her baby from her breast, milk., Other methods of spreading of the virus, are rare and include accidental needle injury,, artificial insemination with infected donated, semen and transplantation with infected organs., AIDS virus has been found in urine, tears,, saliva, breast milk and vaginal secretions but, it seems not to be transmitted by these fluids, unless it gets into injuries., , 237
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Preventive measures:, AIDS has no cure, hence prevention is, the best choice. The following steps help in, preventing this dreadful disease-, , Always Remember, HIV infection is not spread by:, Causal contact such as hugging, insect, bite (mosquitoes), participation in sports,, touching items previously touched by a, person infected with the virus, hand shake,, sharing clothes, swimming pools etc., Clinical manifestations:, The clinical manifestations (symptoms), of AIDS have been classified into four broad, categories., i., Initial infection with the virus and, formation of antibodies, usually 2-8, weeks after initial infection., ii. Asymptomatic carrier state in which, no signs of disease, are seen. Incubation, period ranges for 6 months to 10 years., iii. AIDS related complex (ARC) with one, or more of the following clinical signs:, recurrent fever for longer than one, month, fatigue, unexplained diarrhea,, night sweats, shortness of breath, loss of, more than 10 per cent body weight, etc., iv. AIDS is the end stage of HIV infection., It is characterised by life threatening, opportunistic infections (like pneumonia,, tuberculosis, kaposi sarcoma, etc.)., , i., , People, particularly those in high –risk, group, should be educated about HIV, transmission., , ii., , Disposable needles and syringes should, be used and disposed off properly and, immidiately., , iii., , Sexual habits, immediately., , iv., , High-risk groups should refrain from, donating blood., , v., , Tooth brushes, razors, other articles that, can become contaminated with blood, should not be shared., , vi., , Before receiving blood, ensure that it has, been screened for not containing HIV, infections., , should, , be, , changed, , vii. Routine screening must be done for –, • Blood donors., • Organ donors (kidney, liver, lung, cornea)., • Donors of semen and growth hormone., • Patients undergoing hemodialysis and, females in high risk group who are, pregnant or contemplating pregnancy., , Do you know ?, •, •, , Every year, December 1st is observed as World AIDS Day., India started a National AIDS control Programme in 1987., “A red ribbon” is worn on World AIDS Day as a universal symbol, of awareness and support for people living with HIV., • In India, 4 AIDS reference centers have been established AIIMS – New Delhi., National Institute of Virology, Pune., Center of advanced research on Virology, Vellore., National institute of communicable diseases, New Delhi., • National AIDS Control Organization (NACO) was set up in year 1992 by the Ministry of, Health and Family Welfare. The aim of this organization is to prevent further transmission, of HIV, to decrease morbidity and mortality associated with HIV infection and to minimize, the socio-economic impact resulting from HIV infection., 238
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Laboratory diagnosis:, At first a test is used to detect the HIV, antibodies, while a second confirmatory test, is used to weed out any false positive results., The first test is ELISA (Enzyme-Linked, Immunosorbent Assay). The confirmatory test,, usually a Western Blot, is a highly specific, test. It is based on detecting specific antibody, to viral core protein and envelope glycoprotein., Treatment of AIDS :, Although AIDS has no cure, certain, medicines called as Antiretroviral drugs can, help in reducing the viral load and prolong the, life of HIV patient. Examples of these drugs, used in Antiretroviral therapy (ART) are TDF, (tenofovir), EFV(Efavirenz), Lamivudine, (3TC), etc., The advancements made in biological, sciences have helped us to deal effectively with, many infectious diseases. The use of vaccines, and immunization programmes have enabled, us to eradicate completely the dreadful diseases, like small pox.Alarge number of other infectious, diseases like polio, diphtheria, pneumonia and, tetanus have been controlled to a large extent, by the use of vaccines. Biotechnology is on, the verge of making available newer and safer, vaccines. Discovery of antibiotics and various, drugs has also enabled us to treat effectively, infectious diseases like tuberculosis., 10.4 Adolescence :, It is the period of begining with the, appearance of secondary sexual characters, and the termination with ceassation of somatic, i.e. body growth. It can also be regarded as, a transitional stage of physical and mental, development of child occurring between, puberty and the legal adulthood between 10 to, 19 years of age where individual is no loger a, child but not yet an adult., , development on many fronts like sexual and, reproductive maturity, mental development,, adult identity and transition from socioeconomic and emotional dependant to relative, independence., Stages of Adolescence :, Adolescents are defined are individual 10 to, 19 year age group. The government of India in, its National youth policy defines adolescents, as 13-19 years. Adolescents is divided in three, stage viz. early stage, middle stage and late, stage., i. Early period (10 to 14 years) :, The changes include begining of the, appearance of secondary sexual characters, ; growth reaches to its peak; rapid physical, growth; concrete thinking; defining boundries, of dependence/independence; self exploration;, developing body image; development of intense, friendship; seeking to counter instability and, evaluation., ii. Middle period (15 to 17 years) :, It is characterized by almost complete full, development of secondary sexual characteristic;, growth slows down, approximately 95 % of, the adult stature is attained; thinking is more, abstract; concrete thinking under stressful, conditions; reestablishing of body image, capable of long range thinking; sense of, leadership and all powerfulness; preoccupied, with romantic fantacy; ability testing to, attract opposite sex, peer group help defining, behavioral code etc., iii. Late period (18 to 19 years) :, It is characterized by establishment of total, physical maturity established abstract thinking,, intellectual and functional identity; peer group, recedes in favor of individual relationship,, stable relationship and change from childhood, to adulthood relationship., , Adolescence in fact is a phase rather than, fixed time period in the life. It is a phase of, 239
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Physical changes of adolescence :, • Growth spurt occurs in both boys and, girls. In boys muscles develop, skin, become oily, broadening of shoulders, cracking of voice, development of, underarm and chest hair, pubic hair, facial, hair, enlargement of penis and testis. In, girls development of breast, widening of, hip, development of underarm and pubic, hair, enlargement of uterus and ovaries., • Sexual development : Sex organs mature, and enlarge, sexual desire, errection, of penis in boys, sperm production,, ejaculation, ovulation, menstruation and, initiation of sexual behaviour., • Emotional and social changes : This, include establishing own identity, fantacy,, day dreaming, attention seeking behavior,, emotional instability full of energy, sexual, attraction. Rapid mood changes conflicts, with family, behavioural code (influence, by peer group) self exploration and, evaluation, formation of new relationship,, peer pressure etc., Always Remember, •, , •, •, •, , •, , •, , Avoid looking at your parents as the, enemy. Try to understand that your, parents are human beings, with their own, needs and feelings., Listen to your parents with an open mind,, and try to see their point of view., Share your feelings with your parents so, that they can understand you better., Live up to your responsibilities at home, and in school so that your parents will, be more inclined to grant you the kind of, independence you want and need., Bolster your criticisms of family, school, and government with suggestions for, practical improvements., Be as courteous and considerate to your, own parents as you would be to the, parents of your friends., , Mental Health and Adolesence:, Many of the emotional and social changes, have implication on the mental health. Most of, the mental health issues that people confront, as adults begin to appear in adolesence . The, mental health implication includes confusion, irritation, moodiness, frustration, nausea, less, concentration, hyper activities, anger, effects, on life styles like obesity, addictions, accidents,, leading to ill health etc. The mental illness in, fact is in terms of different forms of depression, like insomnia and loss of energy., Thus, mental illness (disorders or, unfavourable changes) is associated with, psychological or behaviour manifestation., These are broadly classified as either psychoses, or neuroses. Psychoses include delusions,, hallucinations, distrubance in the thinking, process, etc. The psychoses lead to Alzheimer’s, disease schizophrenia, depressive psychosis,, etc. Amnesia (loss of memory) Bullimia, (extreme over indulgence in food) Anxiety (fear, or appretension) Anorexia nervosa (emotional, aversion to food) depression (sadness, inactivity, reduced to enjoy life, etc.) Neuroses include, schizophrenia, illusions, hallucination, etc., Adolescence is thus characterized by, number of cognitive, emotional, behavioural,, physical and attitudinal changes which may, lead to positive personality development, depending upon the relation with parents or to, other conditions, to conflicts to others side. In, fact they view their friends peer group more, important and influential than their parents., This may lead to various kinds of addictions, like smoking, taking drugs, etc., Treatment :, Treatment of such disorders should be, preferentially, with, non-pharmacological, approch with due respect to rights of children., WHO has recommended evidence based, guidelines under mental health Gap Action, Programme (mhGAP)., , 240
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10.5 Addiction :, , This is a complex condition characterised, by compulsive use of substance despite of, its harmful consequences. Addiction may, involve the use of substances (drugs) such, as alcohol, opioids, cocaine, nicotine and, others or behaviours such as gambling., There is scientific evidence that the, addictive behaviours share key neurobiological, features. They intensely involve brain, pathways of reward and reinforcement,, affecting motivation, which involve the, neurotransmitter dopamine. It is important, to know that the neurological changes are, reversible after the substance-use or behaviour, is discontinued., Addiction overall result in the impairment, of physical, physiological and psychological, functions of the body., Causes of, Adolescence, , substances, , abuse, , during, , •, , Insufficent parental, monitoring., , •, , Lack of communication between child, and parents., , supervision, , and, , disappointments and failures as a part, of life. Channelize the energy of child, in sports, studies and other constructive, activities., 10.6 Drugs Abuse :, Surveys and statistics show that use, of drugs and alcohol has been on the rise, especially among the youth. This is really a, cause of concern as it could result in many, harmful effects. Proper education and guidance, would enable youth to safeguard themselves, against these dangerous behaviour pattern and, follow healthy lifestyle. The drugs, which are, commonly abused, are opioids, cannabinoids, and alkaloids of coca., a. Opioids :, These drugs binds to opioid receptors, present in central nervous system and gastrointestinal tract. Heroin, otherwise called, smack is chemically di-acetyl morphine. It is, extracted from latex of poppy plant Papaver, somniferum. Heroin is depressent and slows, down the activity of body., b. Cannabinoids :, , •, , Poorly defined rules., , •, , Family conflicts., , •, , Favorable parental attitudes towards, alcohol and drug uses., , •, , Expectations from drugs use., , Interact with receptors present in brain., Inhalation and ingestion of these substances, affect the cardiovascular system. These are, obtained from inflorescences and the parts of, Cannabis sativa. Marijuana, hashish, charas, and ganja are other different forms of drugs, obtained from this plant., , •, , Risk taking behavior., , c. Cocain :, , Methods /measures to control drug abuse :1. Always remember ‘Prevention is better, than cure’., 2. Avoid undue pressure – A child should, not be forced to perform beyond his /her, capacities in studies, sports and other, activities., 3. Education and Counselling of child, to face problems and stress, to accept, , This is an alkaloid obtained from coca, plant- Erythroxylum coca. It increases level, of neurotransmitter-dopamine. Its excessive, dosage causes extreme happiness, irritability,, paranoia., Hallucinogens (mind expanding drugs) :, These are alkaloids causing day-dreaming., Lycergic acid and cannabis are hallucinogenic, substances. Atropa bellodona and Datura, , 241
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spp. also have hallucinogenic properterties., Hallucination are unreal perceptions of unreal, object due to the disorder of nervous system., Do you know ?, Drugs like barbiturates, amphetamine,, benzo-diazepins, lysergic acid diethylamide, (LSD) are derived from plant Cannabis sativa, are used as a medicine. It help the patient in, contracting insomnia and depression., Addiction and Dependence :, Because of the perceived benefits,, drugs are used repeatedly. The most important, thing, which one fails to realize, is the inherent, addictive nature of alcohol and drugs. Addiction, is a psychological attachment to certain effects, –such as euphoria and a temporary feeling of, well-being –associated with drugs and alcohol., These drive people to take them even when, these are not needed, or even when their use, becomes self-destructive. With repeated use, of drugs, the tolerance level of the receptors, present in our body increases., Consequently the receptors respond, only to higher doses of drugs or alcohol leading, to greater intake and addiction. However, it, should be clearly borne in mind that use of, these drugs even once, can lead to addiction. In, the absence of any guidance or counselling, the, person gets addicted and becomes dependent, on their use. Dependence is the tendency of, the body to manifest a characteristic and, unpleasant withdrawal syndrome if regular, dose of drugs/ alcohol is abruptly discontinued., This is characterized by anxiety, trembling,, nausea and sweating, which may be relieved, when use is resumed., Effects of Drug/ Alcohol Abuse :, The immediate adverse effects of drugs, and alcohol abuse are manifested in the form, of reckless behaviour, vandalism and violence., , Excessive doses of drugs may lead to coma and, death due to respiratory failure, heart failure or, cerebral hemorrhage. A combination of drugs, or their intake along with alcohol generally, results in overdose and even deaths., The most common warning signs of drug, and alcohol abuse among youth include drop in, academic performance, unexplained absence, from school/college, lack of interest in personal, hygiene, withdrawal, isolation, depression,, fatigue, aggressive and rebellious behaviour,, deteriorating relationships with family and, friends, loss of interest in hobbies, change in, sleeping and eating habits, fluctuations in, weight, appetite, etc., There may even be some far-reaching, implications of drug/alcohol abuse. If an, abuser is unable to get money to buy drugs/, alcohol he/she may turn to crime. At times,, a drug/alcohol addict becomes the cause of, mental and financial distress to his/her entire, family and friends., Those who take drugs intravenously (direct, injection into the vein using a needle and, syringe) are likely to acquire serious infections, like HIV and hepatitis B. Use of alcohol during, adolescence may also have long-term effects, like loss balance, liver cirrhosis, pancreatitis. It, could lead to heavy drinking in adulthood., Chronic use of drugs and alcohol damages, nervous system and liver (cirrhosis). Use of, drugs and alcohol during pregnancy adversely, affects the foetus., Another misuse of drugs is that certain, sports persons use drugs to enhance, performance. They (mis)use narcotic, analgesics, anabolic steroids, diuretics and, certain hormones to increase muscle strength, and bulk and to promote aggressiveness and, overall improvement in their performance., Side-effects of the use of anabolic steroids, in females include masculinization (features, like males), increased aggressiveness, mood, , 242
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swings, depression, abnormal menstrual cycles,, excessive hair growth on the face and body,, enlargement of clitoris, deepening of voice., In males it includes acne, increased, aggressiveness, mood swings, depression, and, reduction of size of the testicles, decreased, sperm production, kidney and liver dysfunction,, breast enlargement, premature baldness,, enlargement of the prostate gland. These effects, may be permanent with prolonged use., , Prevention and Control :, The age-old adage (i.e. proverb) is, ‘prevention is better than cure’ holds true for, all addictions. It is also true that habits such as, smoking, taking drug or alcohol are more likely, to be taken up at a young age, more during, adolescence. It is best to identify the situations, that push an adolescent towards use of drugs, or alcohol, and to take remedial measures well, in time. In this regard, the parents and the, teachers have a special responsibility., , Use your brain power, Deaddiction may be difficult but not impossible. Collect information about NGOs,, working in the field of deaddiction., , Activity :, 1. Identify the name of the plant. Enlist different types of drugs derived/obtained from, the same., , 2. Prepare chart of different stages of adolesence mentioning the changes in growth,, sextual development and emotional and social changes., Stages, , I, , Changes, Growth, , Boy, , II, Girl, , 1., 2., 3., , 1., Sexual development 2., 3., 1., Emotional and social 2., 3., 243, , Boy, , III, Girl, , Boy, , Girl
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Exercise, Q. 1 Multiple Choice Questions, 1. Which of the following is NOT caused, by unsterilized needles?, a. Elephantiasis, b. AIDS, c. Malaria, d. Hepatitis B, , 9. Confirmatory test used for detecting, HIV infection is ................., a. ELISA, b. Western blot, c. Widal test, d. Eastern blot, 10. Elephantiasis is caused by ............, a. W. bancrofti, b. P. vivax, c. Bedbug, d. Elephant, , 2. Opium derivative is .............., a. Codeine, b. Caffeine, c. Heroin, d. Psilocybin, , 11. Innate immunity is provided by ..........., a. phagocytes, b. antibody, c. T- Lymphocytes, d. B- Lymphocytes, , 3. The stimulant present in tea is ............., a. tannin, b. cocaine, c. caffeine, d. crack, 4. Which of the following is caused by, smoking?, a. Liver cirrhosis, b. Pulmonary tuberculosis, c. Emphysema, d. Malaria, 5. An antibody is ..............., a. molecule that binds specifically an, antigen, b. WBC which invades bacteria, c. secretion of mammalian RBC, d. cellular component of blood, 6. The antiviral proteins released by a, virus-infected cell are called ............, a. histamines, b. interferons, c. pyrogens, d. allergens, 7. Both B-cells and T-cells are derived, from ...................., a. lymph nodes, b. thymus glands, c. liver, d. stem cells in bone marrow, 8. Which of the following diseases can be, contracted by droplet infection?, a. Malaria, b. Chicken pox, c. Pneumonia, d. Rabies, , Q. 2 Very Short Answer Questions, What is the source of cocaine?, Name one disease caused by smoking?, Which cells stimulate B-cells to form, antibodies?, What does the abbreviation AIDS stand, for?, Name the causative agent of typhoid, fever?, What is Rh factor?, What is schizont?, Name the addicting component found in, tobacco., Name the pathogen causing Malaria., Name the vector of Filariasis., Give the name of the causative agent of, ringworm., Define health., Q. 3 Short Answer Questions:, 1. What are acquired diseases?, 2. Differentiate between antigen and, antibody., 3. Name the infective stage of Plasmodium., Give any two symptoms of malaria., 4. Explain the mode of infection and cause, of elephantiasis., 5. Why is smoking a bad habit?, 244
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6. What do the abbreviations AIIMS and, CMIS denote?, 7. What is a carcinogen? Name one, chemical carcinogen with its target, tissue., 8. Distinguish between active immunity, and passive immunity., Q. 4 Short Answer Questions, Differentiate between B-cells and Tcells., What are the symptoms of malaria?, How does malaria spread?, Write a short note on AIDS., Give the symptoms of cancer., Write a note on antigens on blood cells., Write a note on antigens-antibody, complex., What are the various public health, measures, which you would suggest as, safeguard against infectious diseases?, How does the transmission of each of, the following diseases take place?, a. Amoebiasis, b. Malaria, c. Ascariasis, d. Pneumonia, What measure would you take to prevent, water-borne diseases?, Write a short note on typhoid., , Q. 5 Match the following., Column I, a. AIDS, b. Lysozyme, c. B-cells, d. T-helper cells, e. Antibody, , Column II, i. Antibody production, ii. Activation of B-cells, iii. Immunoglobulin, iv. Tears, v. Immuno deficiency, , Q. 6 Long Answer Questions, Describe the structure of antibody., Write a note on Vaccination., What is cancer? Differentiate between, bening tumor and malignant tumor., Name the main five types of cancer., Describe the different type of immunity., Describe the ill –effects of alcoholism on, health., In your view, what motivates the, youngsters to take to alcohol or drugs, and how can this be avoided?, Do you think that friends can influence, one to take alcohol/drugs? If yes, how, may one protect himself/herself from, such an influence?, , Project :, 1. Collect information about the, symptoms and preventive measures treatments for Dengue,, Swine flu and Tuberculosis (TB)., 2. Browse the information about COVID - 19 with respect to, a. Structure, b. Modes of infection, c. Preventive measures, d. Treatment, , 245
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11, , Enhancement of Food Production, Do you know ?, , Can you recall?, , Primary aim of plant breeding is, to obtain a new crop veriety superior to, the existing type, in all characters. This, purposeful manipulation incorporates various, objectives. which differ form plant to plant, depending upon its type and the use. Some, objectives are common- like yield, quality,, resistance, life cycle span, etc., while some, objectives will differ on the basis of the type, and use of plant., , 1. What are hybrid plants?, 2. Different examples of microbes used in, household production., 3. The types or groups of micro-organism, that produce antibiotics., 4. What are biofertilizers?, 5. What is the source of silk thread?, 11.1 Improvement In Food Production :, Food is one of the basic needs as it gives us, energy for everything. It keeps us alive, strong, and healthy. It can be defined as any thing solid, or liquid, which when swallowed, digested and, assimilated in the body, keeping us well. It is, organic, energy rich, non-poisonous, edible and, nourishing substance., Green plants synthesize their own food, through photosynthesis. But animals including, humans can not synthesize their food on their, own, hence are dependent on plants directly., The famine is responsible for dearth of, food, besides the rapid and dramatic increase, in world population over the time. To meet, the increasing demand for food, there is need, for improvement of food production, both, quantity wise and quality wise (nutritive)., Plant breeding and animal breeding help us, to increase the food production., 11.2 Plant breeding :, The, improvement, or, purposeful, manipulation in the heredity of crops and the, production of new superior varieties of existing, crop plants, constitute what is called plant, breeding. It is, therefore, an applied branch, of botany. It is infact an art and the science, of changing and improving the heredity of, plants. Plant breeding can be carried out by, using the applications of principles of genetics,, taxonomy, physiology, pathology, agriculture,, rDNA technology, etc., , Plant breeding is a method of altering, the genetic pattern of plants to increase their, value and utility for human welfare. The plant, breeding is done to increase crop yield, improve, quality, increase tolerance to environmental, stresses, make the plants resistant to pathogens, and increase tolerance to insect pest. Green, Revolution was the result of a sequence of, scientific breakthroughs and developmental, activities that successfully fought hunger, by increasing food production. Seeds with, superior quality, use of chemicals - pesticides, and fertilizers, and multiple cropping system, supported by the use of modern farm machinery, and proper irrigation system, helped for the, development of high-yielding and disease, resistant varieties in wheat, rice, maize, etc., In fact, plant breeding dates back to about, 10,000 years ago. The present day crops are the, result of domestication and acclimatization., , 246, , Do you know ?, Different methods of plant breeding, include Introduction, Selection, Hybridization,, Mutation breeding, Polyploidy breeding,, Molecular plant breeding, Tissue culture,, rDNA technology, SCP, etc.
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called wide/ distant crosses. Interspecific and, intergeneric hybrids are seldom to occur in the, nature., The main steps of the plant breeding, program (Hybridization) are as follows :, , Know the Scientist :, Dr. Norman E. Borlaug:, An American biologist, who has been, called “Father of the Green Revolution”,, “Agriculture’s greatest spokesperson” and, “The Man Who Saved a Billion Lives., Dr. Borlaug, a 1970 Nobel Laureate,, was honoured for his work in the ‘Green, Revolution,’ saving millions of lives from, famine in India, Mexico, and the Middle, East., Dr. M. S. Swaminathan:, He has been called the “Father of Green, Revolution in India” for his role in introducing, and further developing high-yielding, varieties of wheat in India. He advocated, moving India to sustainable development,, especially using environmentally sustainable, agriculture, sustainable food security and the, preservation of biodiversity. He is pioneer in, mutation breeding in India. He developed, new varieties of wheat like sonora, NP 165, and sarbati., , 1. Collection of Variability :, Wild species and relatives of the cultivated, species having desired traits, should be collected, and preserved. The entire collection having, all the diverse alleles (i.e. variations) for all, genes in a given crop, is called germplasm, collection. Variations are useful in the selection., Germplasm conservation can be done in, following ways• In situ conservation : It can be done with, the help of forests and Natural Reserves., • Ex situ conservation : It is done through, botanical gardens, seed banks, etc., , A. Hybridization and its technique :, It is the cheif method that offers greater, possibilities in the crop improvement than, other methods. The use of this method is the, only effective means of combining together the, desirable characters of two or more varieties., By this method, one can create new genetic, combinations of already existing characters, and new genetic variations. It also exploits and, utilizes hybrid-vigour., Internet my friend, Try to know more about the hybrid-vigour., Hybridization can be intravarietal,, intervarietal (between two varieties of the same, species), interspecific (between two species, of the same genus) and intergeneric (between, two genera of the same family). As parental, plants are distantly related, such crosses are also, , 2. Evaluation and Selection of Parents :, It is an important and essential step. The, collected germplasm is evaluated (screened), to identify plants with desirable characters., The selected parents must be healthy, vigorous, and should show desirable but complementary, features. The selected parents are selfed for, three to four generations to make them pure, or homozygous. It is made sure that only pure, lines are selected, multiplied and used in the, hybridization., 3. Hybridization :, The variety showing maximum desirable, features is selected as female (recurrent) parent, and the other one as male parent (donor) which, lacks good characters found in recurrent parent., The pollen grains from anthers of male, parent are collected and then artificially dusted, over stigmas of emasculated flowers of female, parent. Pollination is followed by seed and fruit, formation in due course. The seed, thus obtained, represents the hybrid generation., The hybrid F1 progeny is selected and, evaluated forthe desired combinations of, characters., , 247
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Chart 11.1 : Steps of Hybridization technique, Collection of variability from germ plasm/ gene, bank, Evaluation and selection of parents, Selection of parent plants with different qualities, Selected parents selfed for three to four generations to, make them homozygous or true breeding, Identification of parents as male parent (donor) and, female parent (recurrent), , performance is recorded. The selected lines, are then grown for three generations at least in, natural field, in different agroclimatic zones., Finally variety is released as new variety for use, by the farmers., Many high yielding, hybrid varieties of rice,, wheat, sugarcane, millets, developed through, hybridization, have helped farmer community, to attain record agricultural production in India, since 1961. This is called green revolution., Indian Hybrid Crops :, , Collection of pollen grains from the flowers of male, parent, , 1. Wheat and Rice :, In 1960s, wheat and rice production, increased tremendously., Norman, E., Borlaug developed semi-dwarf varieties of, wheat. Sonalika and Kalyan Sona are two of, the hybrid wheat varieties, grown in India., Semi-dwarf rice varieties were taken from, IR−8 (International Rice Research Institute), and Taichung native−I (from Taiwan) and, introduced in India. Jaya, Padma and Ratna are, the better-yielding, semi-dwarf rice varieties that, were developed later., , Removal of stamens from the flowers of the female, parent (emasculation), Artificial cross pollination by using pollen grains, collected from male parent, Bagging, tagging of the emasculated flower of female, parent, Development of fruit and seed representing F1, (hybrid)generation, Selection and testing of F1 hybrid for combination of, desirable characters, Field trials for yield (productivity), Testing and the release of variety, , 4. Selection and Testing of Superior, Recombinants :, The F1 hybrid plants showing superiority, over both the parents and having high hybridvigour, are selected. Such hybrids are then selfed, for few generations to make them homozygous, for the said desirable characters till there is a, state of uniformity, so that the characters will not, segeregate further., 5. Testing, Release and Commercialization of, New Cultivars :, The newly selected lines are evaluated, for the productivity and other features like, disease resistance, pest resistance, quality, etc., Initially, these plants are grown under controlled, conditions of water, fertilizers, etc. and their, , 2. Sugarcane :, • Saccharum barberi is a native of North, India and S. officinarum belongs to South, India., • S. officinarum has thicker stem and high, sugar contents, but it does not grow well in, North India., • These two varieties were crossed to get, the desirable qualities of both (high sugar, content, thicker stem and the ability to grow, in North India). CO -419, 421, 453 are high, yielding and having high sugar contents, are developed in India at Coimbatore, (Tamilnadu)., 3. Millets :, • Hybrid maize (Ganga-3), Jowar (CO-12),, and Bajra (Niphad) have been successfully, developed in India., • These varieties are high yielding and, resistant to water stress., , 248
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Plant Breeding for Disease Resistance :, Some of the diseases caused in plants arePathogen, Fungi, , Bacteria, Viruses, , variety of rice, NP 836 variety of wheat (rust, resistant), Indore-2 variety of cotton (resistant, to bollworm), Regina-II variety of cabbage, (resistant to bacterial rot), etc., , Plant disease, Brown rust of wheat, Red rot of sugarcane, Late blight of potato, Black rot of crucifers, Tobacco mosaic virus, , The basic objective of breeding for disease, resistance is to develop inherent quality in the, plant to prevent the pathogen from causing, the disease. Such varieties of plants are called, disease resistant plants. The basic technique used, is the same as for normal hybridization process., Some disease resistant plants developed are :, Crop, , Variety, , Resistant, to, Disease, Wheat, Himgiri, Leaf and stripe, rust, hill bunt, Brassica, Pusa Swarnim White rust, Cauliflower Pusa Shubra Black rot and, Curl blight black, rot, Chilli, Pusa, Chilli, mosaic, Sadabahar, virus, Tobacco, mosaic virus and, leaf curl, B. Mutation Breeding :, Mutation is sudden heritable change in, the genotype, caused naturally. It can also be, induced by application of chemical mutagens., Natural (physical) mutagens are : High temperature, high concentration of CO2, X rays,, UV rays., Chemical mutagens are : Nitrous acid, EMS, (Ethyl- Methyl- Sulphonate), Mustard gas,, Colchicine, etc., Seedlings or seeds are irradiated by CO60, exposed to UV bulbs, X ray machines, etc., Mutagens cause gene mutations and, chromosomal, aberrations., The, treated, seedlings are then screened for resistance to, diseases/ pests, high yield, etc. e.g. Jagannath, , Plant Breeding for Developing a Resistance, to Insect Pest:, Insects being herbivores, incur heavy loss in, the quantity and quality of crops. Resistance in, crops can be developed by following ways :, • Development of morphological characters, like hairy leaves in cotton and wheat, develop vector resistance from jassids and, cereal leaf beetle, respectively., • Solid stem in wheat leads to resistance to, stem borers., • Biochemical characters provide resistance, to insects and pests. For example, the high, aspartic acid, and low nitrogen and sugar, content in maize, lead to resistance against, stem borers., • The nectar-less cotton having smooth leaves, develop resistance against bollworms., Some pest-resistant varieties areCrop, Variety, Brassica Pusa Gaurav, Flat bean Pusa sem 2, Pusa sem 3, Okra, Pusa Sawani,, Pusa A-4, , Insect pest, Aphids, Jassids, aphids and, fruit borer, Shoot and fruit borer, , 11.3 Tissue culture :, It is actually a collection of different, techniques. It is infact, emerged as a technique, of plant biotechnology. Here, isolated cells,, tissues, organs are grown ‘in vitro’ on a solid/, liquid nutrient medium, under aseptic and, controlled conditions of light, humidity and, tempreature, for achieving different objectives., The part of plant used in tissue culture is called, explant., Plant tissue culture is based on principle, of Totipotency which is an inherent ability of, living plant cell to grow, divide, redivide and, give rise to a whole plant. Haberlandt (1902), , 249
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for the first time conceived this idea and, developed the concept of in vitro cell culture, (plant morphogenesis)., The plant tissue culture medium contains all, essential minerals, sources for carbohydrates,, proteins and fats, water, growth hormones,, vitamins and agar (for callus culture). The, most commonly preferred medium for tissue, culture is MS (Murashige and Skoog) medium., Based on the nature of explant : There are, three types viz, cell culture, organ culture and, embryo culture., Based on the type of in vitro growth : There, are two tyes viz. Callus culture (solid medium), and Suspension culture (liquid medium)., Maintenance of aseptic, conditions, :, Aseptic condition is essential so as to avoid, contamination by other harmful microorganisms. It is accomplished by sterilization, of : glass ware (use of detergents, hot air, oven), nutrient medium (by autoclave under, constant pressure of 15 lb/sq inch for continous, 20 minutes), Explant (by treatment of 20%, ethyl alcohol and 0.1% HgCl2), Inoculation, chamber (Laminar air flow) - by using UV, ray tube for 1 hour before performing actual, inoculation of explant on the sterilized nutrient, medium., , Other conditions maintained are :, Temperature - 180C to 200C, pH of nutrient, medium 5 to 5.8 and aeration particularly for, suspension culture., In callus culture the solid medium is used., The development and organisation of tissue, is lost. Hence, the cells of explant, divide and, redivide to form a mass of undifferentiated cells,, called callus. It is maintained on solid medium., Callus can be induced to form organs like root, (rhizogenesis) and shoot (caulogenesis) and, thus the plantlet. No shaker (agitator) is needed., In suspension culture small groups of, cells or a single cell are used as explant in the, liquid medium. The liquid medium is constantly, agitated by using shakers (agitators) so that, there is constant mixing of medium and the, explant., Both the callus and suspension cultures die, in due course of time. Therefore, subculturing, is neccessary for continuation of the technique., Micropropagation (Clonal Propagation) :, Organogenesis via shoots is considered, as one of the most widely used commercial, method of regeneration of plant., Micropropagation is also known as, clonal propagation. It is the only process, adopted by Indian plant biotechnologists in, , Callus, , Shoot, Explant, , Root, Mother plant, , Multiple, plants, , Organogenesis, Hardening, , Fig. 11.2 : Steps in plant tissue culture (callus culture), 250
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Advantages of microporpagation:, Do you know ?, Applications of tissue culture :, There are various application of tissue culture, in forestry, agriculture, horticulture, genetic, enginearing, physiology, etc. The different, applications of tissue culture include Production of disease free plants and haploid, plantlets, micropropagation, production of, secondary metabolites, protoplast culture,, culture of rare plants, somaclonal variations, production of stress resistant plants, etc., different industries, mainly for the commercial, production of ornamental plants like orchids,, Chrysanthemum, Eucalyptus, etc. and fruit, plants like banana, grapes, Citrus, etc., , 1. It helps in rapid multiplication of plants., 2. A large number of plantlets are obtained, within a short period and from a small, space., 3. Plants are obtained throughout the year, under controlled conditions, independent, of seasons., 4. Genetically similar plants (clones) are, produced (formed) by this method., Therefore desirable characters (genotype), and desired sex of superior variety are, kept constant for many generations., 5. The rare plant and endangered species, are multiplied by this method and such, plants are saved., , Chart 11.3 : Flow chart for tissue culture technique., Cleaning of glass ware, sterilization of glass ware and instruments in an oven/ autoclave, Selection and preparation of nutrient medium- MS medium with known concentrations and, proportions of different components., Sterilization of medium in an autoclave for continuous 20 minutes under constant pressure, of 15/ lb/ inch2., Preparation of plant material (explant) includes isolation of explant followed by surface, sterilization and rinsing with water. Explant is obtained from the growing stock plant., Inoculation of the explant in the culture flask containing sterilized nutrient medium., Inoculation is done in the laminar air flow cabinet unit., Incubation of the inoculated explant. Here cells of explant grow, proliferate to form callus,, within 2-3 weeks., Sub culturing of the callus (if callus is to be maintained for longer period, callus is divided, into 3-4 segments and then transferred to fresh culture medium)., Organogenesis - Initiation of rooting and shooting, that eventually leads to plantlet, formation., Hardening - Plantlets are transferred to polythene bags containing sterilized soil and kept at, low light and high humid conditions for suitable period of time., Transferred to field, 251
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6. With the help of somatic hybrids (cybrids),, we are able to obtain new variety in short, time span., Do you know ?, High yielding varities of Banana viz., ‘Shrimati’, ‘Basarai’ and G- 9 are mostly, used in Maharashtra., 11.4 Single cell protein (SCP) :, By 2050, the world would need to produce, 1,250 million tonnes of meat and dairy products, per year, to meet global demand for animalderived protein at current consumption levels., However, growing demand for protein will, not be met sustainably by increasing meat and, dairy production because of the low efficiency, of converting feed to meat and dairy products., More over, human population in, underdeveloped and even in the developing, countries is suffereing from protein malnutrition,, resulting into variety of nutritional diseases., To fight with this, efforts are undertaken by, conventional methods to increase the food yield, by different methods of crop improvement,, use of biofertilizers, biopesticides, chemical, fertilizers and high yielding varieties (green, revolution). The efforts in other direction are, also undertaken in nonconventional way., One such way is production of SCP- single, cell proteins. Improtance of SCP was realised, during World War I., Single-cell protein refers to the crude, or, a refined edible protein, extracted from pure, microbial cultures or from dead or dried cell, biomass., Microorganisms like algae, fungi, yeast,, and bacteria have very high protein content in, their biomass. These microbes can be grown, using inexpensive substrates like agricultural, waste viz. wood shavings, sawdust, corn cobs,, paraffin, N-alkanes, sugarcane molasses, even, human and animal wastes., , The microorganisms utilize the carbon, and nitrogen present in these materials and, convert them into high-quality proteins that, can be used as a supplement, in both human, and animal feed. Besides proteins, SCP is also, rich in vitamins, vitamin B complex, minerals, and fats. The single-cell proteins can be readily, used as fodder for achieving fattening of calves,, pigs, in breeding fish and even in poultry and, cattle farmimg. The microorganisms used for, the production of SCP are as follows :, Fungi : Aspergillus niger, Trichoderma viride, Yeast : Saccharomyces cerevisiae, Candida, utilis, Algae : Spirulina spp, Chlorella pyrenoidosa, Bacteria : Methylophilus methylotrophus,, Bacillus megasterium., Advantages of Single-Cell Protein :, • Microorganisms have a high rate of, multiplication that means, a, large, quantity of biomass can be produced in a, comparatively short duration., • The microbes can be easily genetically, modified to vary the amino acid, composition. They have high protein, contents- 43% to 85% (W/W basis)., • A broad variety of raw materials, including, waste materials, can be used as a substrate, for SCP. This also helps in decreasing the, number of pollutants., • SCP serves as a good source of vitamins,, amino acids, minerals, crude fibres, etc., 11.5 Biofortification, It is a method in which crops are breed, (produced) for having higher levels of vitamins,, minerals and fats (i.e. better nutritive value)., Due to this, problem of malnutrition can be, overcome. Following objectives were considered, for the breeding program :, , 252, , •, •, •, •, , Protein content and quality, Oil content and quality, Vitamin content, Micronutrient content and quality
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Biofortification can be achieved through, conventional selective- breeding practices and, also through r-DNA technology. It focusses on, making plant food more nutritive as plants grow, or develop., Some examples of biofortification :, • Fortified Maize having twice the amount, of amino acids- lysine and tryptophan., • Wheat -Atlas 66 has a high protein content, and Iron-fortified rice has 5 times more, iron, are developed., • Vegetable crops like carrot and spinach, have more vitamin A and minerals., • Vitamin C enriched bitter gourd, tomato, have been developed by IARI., 11.6 Animal husbandry :, Animal husbandry is an agricultural, practice of breeding and raising livestock. It is, not only a skill of farmers but also is as much, a science, as it is an art., Animal husbandry deals with care and, breeding of livestock like buffaloes, cows,, pigs, horses, cattles, sheeps, camels, goats, etc., which are useful to humans. It also includes, poultry farming, fish farming, bee keeping,, sericulture, lac culture, etc. Animals like honey, bees, silk worms, prawns, crabs, birds, fishes,, pigs, cattles, sheeps and camels have been used, by humans for the products like milk, eggs,, meat, wool, honey, silk, etc., During the conventional practices of, animal breeding, just taking care is not enough, to give maximum yield. Although India and, china have 70% of world livestock population,, surprisingly the productivity serves only 25%, of the world farm produce., So professional approach is needed to, boost the production. It requires management, procedures, new technologies to be employed, in various farm system to achieve improvement, in quality and productivity. Industrial principles, of production, processing and marketing are to, be employed., , Management of farms and farm animals :, Farm management starts from selection of, high yielding breeds, their food requirements,, supply of adequate nutritional sources,, cleanliness of the environment and maintenance, of health. Management of farm animals includes, veterinary supervision, vaccination, high, yielding cross breed development, production, and preservation of products, distribution and, marketing., A. Animal breeding :, Breeding of animals is an important aspect, of animal husbandry. Animal breeding aims at, increasing the yield of animals and improving, the desirable qualities of the products., Breed:, A group of animals related by descent, and similar in most characters like general, appearance, features, size, configuration, etc.,, are said to belong to a breed., Animal breeding is done for getting, improved breeds with desirable qualities of, product and to increase yield of animals,, Desirable characters such as increased, production of milk, quality of product, quality, of meat or maximum yield of eggs per year, etc., are necessarily achieved through animal, breeding., Can you tell?, Find out the name of common breeds, of cattle and poultry in the farms, found in, your area., Breeding can be of two main types inbreeding and outbreeding :, a. Inbreeding : It involves breeding of closely, related individuals for 4 to 6 generations., Inbreeding increases homozygosity. By, inbreeding, pure lines of animals can, be obtained. Inbreeding is helpful in the, elimination of harmful recessive genes and for, the accumulation of superior genes. Inbreeding, has the demerit that it usually reduces the, fertility and productivity., , 253
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b. Outbreeding: It involves breeding of, unrelated animals. The animals may be of the, same breed but having no common ancestors, for 4 to 6 generations., Outcrossing involves breeding between the, animals of different species. It is also known as, interspecific hybridization. Outcrossing helps, to remove the inbreeding depression., Crossbreeding involves the breeding, of superior male of one breed with superior, female of another breed. By cross-breeding,, new animal breeds of desirable characters are, developed. e.g. Hisardale is a new breed of, sheep developed from crossing of Bikaneri ewe, and Marino rams in Punjab., Interspecific hybridization involves, breeding of animals of two different but related, species. It result in the formation (production), of animals with desirable characters from both, the parents. But such breeding is not always, successful e.g. Mule is a breed obtained from, horse and donkey., Artificial, insemination, technique, involves controlled breeding experiments., Semen from selected superior males is collected, and preserved in frozen state or injected into, the genital tract immediately. It is useful to, overcome problem of normal mating and, convenience of transportation., Multiple Ovulation Embryo Transfer, (MOET) involves the technology which, provides the chances of successful production, of hybrids. In this method, cow is administered, with FSH like hormone, to induce follicular, maturation and then the super ovulation is, brought about. In each cycle, 6 to 8 eggs mature, simultaneously. The cow is either mated with, an elite bull or artificially inseminated. The, blastocysts at 8 to 32 cell stage are recovered, non-surgically and transferred to surrogate, mothers. This technology is successfully used, in cattles, sheeps, rabbits, buffaloes, etc., High milk yielding breeds of female and high, , quality meat yielding bulls have been found to, be successful, to increase herd size in a short, period., B. Dairy farm management :, Dairy industry involves production,, processing and distribution of milk and, milk products. Milk is a valuable food stuff, universally consumed by human beings. Milk, yield mainly depends on the quality of breeds in, the farm. Selection of good breeds having high, yielding potential under the climatic conditions, of inhabiting area, and disease resistance is the, basic requirement. In India, cows and buffaloes, are mainly used for dairy farms. Sahiwal,, Sindhi, Gir are Indian breeds and Jersy, Brown, Swiss, Holstein are exotic breeds, which are, used in dairy farming. Buffaloes are restricted, to some part of Asia only., In India, six breeds occur viz, Jaffarabadi,, Mehsana, Murrah, Nagpuri, Nili, Surati,, which are all good milk producers. Cattles, have to be well looked after. Quality and, quantity of fodder in proper ratio, should be, given. Silage made from legumes and grasses,, maize and jowar, makes good feed. Silage, is supplemented with oil cakes, minerals,, vitamins and salts. Cleanliness and hygiene of, the cattles and handlers is of more importance, while milking, storage and transport of milk, and milk products. In recent years, much of, these processes are mechanised, which reduce, the chance of direct contact with the product., The shed must be cleaned daily. It should be, spacious with adequate facilities for feeding,, watering and lighting., Do you know ?, Regular visit of veterinary doctor to, dairy farm is mandatory, why ?, Milk, processing,, marketing, and, distribution, play an important role in dairy, industry. Variety of milk product like curd,, cream, butter, ghee, condensed milk, khoa,, , 254
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cheese must be prepared from extra milk and on, demand. An additional income can be obtained, in the cattle farms from cow dung, manure, fuel, cakes and gobar gas for cooking and lighting., C. Poultry farm management :, Poultry includes number of bird species, such as chicken, ducks, turkey, and fowls which, are domesticated for their eggs and meat., Can you tell?, 1. What is layer ?, 2. What is broiler ?, Allied professions to poultry include, processing of eggs and meat, marketing, of poultry products, compounding and, sale of poultry feed, poultry equipment,, pharmaceuticals, feed additives, etc., Selection of proper and disease free breed,, suitable and safe farm condition, proper, feed and water, hygiene and health care,, are important requirements for poultry farm, Management. On the basis of their origin,, different types of poultry breeds are : American, breeds Plymouth Rock, New Hampshire,, Rhode Island Red; Asiatic breeds are Brahma,, Cochin and Langshan; Mediterranean breeds, are Leg horn, Minorca; English breeds include, Australorp; Indian breeds are Chittagong,, Aseel, Brahma, and Kadaknath., Leghorn is best layer (for eggs) while, Playmouth rock, Rhode Island Red, Aseel,, Brahma and Kadaknath, are preferred as, broilers (for meat)., Management of layers, requires purchase, of high yielding chicken, well ventilated, farms, proper feed, debeaking, lighting,, waterer, sanitation, culling and vaccination., Management of broilers requires selection, of breed, housing, temperature, ventilation,, lighting, floor space and broiler feed. Different, types of poultry diseases are:, , i. Viral diseases like Ranikhet, Bronchitis,, Avian influenza (bird flu), etc. Few years, back, bird flu have seriously influenced poultry, farming and human infection too., ii. Bacterial diseases mainly includes, Pullorum, Cholera, Typhoid, TB, CRD (chronic, respiratory disease), Enteritis, etc., iii. Fungal diseases are Aspergillosis, Favus, and Thrush., iv. Parasitic diseases include lice infection,, round worm, caecal worm infections, etc., v. Protozoan diseases e.g. Coccidiosis is a, protozoan disease., D. Apiculture or bee keeping :, Apiculture or bee keeping deals with an, artificial rearing of honey bees to obtain bee, products like honey, wax, pollens, bee venom,, propolis (bee glue) and royal jelly as well as, pollinating agents for crop plants., , Fig. 11.4 : Bee hive, Bee keeping is an ancient cottage industry., Honey is a food of high nutritive value and, also finds uses in the indigenous system of, medicines., Can you tell?, Why are honey bees called as best, pollinators?, The four species of honey bees commonly, found in India are Apis dorsata (rock bee or, wild bee), Apis florea (little bee), Apis mellifera, (European bee) and Apis indica (Indian bee)., , 255
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seasons, handling and collection of honey, bee, wax and other products. Periodic inspection for, cleanliness of hive boxes, activity of bees and, queen, condition of brood, provision of water,, is very much necessary., Many Indian crop fields need the services, of honey bees as the pollinators. Bee keeping in, the crop field of sunflower, mustard, safflower,, chilly, cabbage, cucumber, legumes, fruits like, apple, mango, citrus, etc. help in increasing, the productivity of honey as well as crops, tremendously., , Knowledge enhancer :, For bee keeping, Apis mellifera and Apis, indica are the suitable species, hence they, are known as domesticated species., , Worker, , Queen, , Drone, , Fig. 11.5 : Honey bee (Apis mellifera), Polymorphism in honey bee :, Bee keeping is practiced in the areas, where sufficient wild shrubs, fruit orchards, and cultivated crops are present. Bee keeping, requires the equipments like bee hive boxes,, with comb foundation sheets, bee veil, smoker,, bee brush, gloves, gumshoes, uncapping knife,, swarm net, queen excluder, overall hive tool,, etc., Outer cover with, crown board, Inner cover, , E. Fishery :, Fishery is a branch of applied biology, which deals with the catching, processing, fish, farming and marketing of fish, and other useful, aquatic animals such as, prawns, lobsters,, oysters, mussels and crabs. Three division of, fishery are- inland fishery, marine fishery and, estuarine fishery., Inland fishery includes culturing and, capturing of fish from fresh water bodies like, ponds, lakes, dams and river. Inland aquatic, area of our country covers about 40 to 50 lakh, acres. The common fresh water fish are Labeo, rohita (rohu), Catla (catla), Cirrhina mrigala, (mrigala) and other carps., , Honey super, Frames with, wax foundation, Queen excludor, , Rohu fish, , Catla fish, , Mrigal fish, , Common carp, , Hive bodies, Entrance reducer, Floor board, Bottom stand, Grass carp, , Fig. 11.6 : Artificial bee hive, Artificial bee hive :, For successful bee keeping one must be, familiar with the habits of bees, selection, of suitable location, catching and hiving of, swarms, management of hives during different, 256, , Silver carp, , Fig. 11.7 : Fresh water fish forms
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Knowledge enhancer :, Fish farming or culturing of edible and, commercially important fish is only possible, in fresh water bodies., Marine fishery includes capture of fish, from sea water. Indian coastal line is about, 7500 km long. The common marine fish, are Harpadon (Bombay duck), Sardinella, (sardine),, Rastrelliger, (mackerel), and, Stromateus (pomphret)., Can you tell?, , F. Sericulture :, Sericulture is the branch of applied, zoology which deals with rearing of silkworm, and production of silk. Like other farming,, sericulture also involves skill and scientific, knowledge for rearing and development. It, require less investment and can be started in, small space. It is the oldest business and large, number of families are associated with the, production of silk in India. Disabled, older, persons, handicapped people can successfully, do this job., Adult female, Eggs on mulberry leaf, , 1. Give the names of estuaries found in, Maharashtra and where these estuaries, are located., 2. Enlist the names of different fish found at, an estuary., , Cocoon, , Estuarine fishery includes capture of fish, from estuary. Estuary is a place where river, meets the sea. e.g. Sunderban area in west, bengal., The common factors for the maintenance, of fish farm, includes selection of suitable, site, excavation of ponds, requirements of, hatchery tank, nursery tank, rearing tank,, stocking tank or ponds, water source, manures,, supplementary feed, etc. The culture fishery, may be monoculture (only one species) or, polyculture (many species) type., After catching the fishes, fish spoilage is, prevented by different preservation methods, like chilling, freezing, freeze drying, sun, drying, smoke drying, salting and canning. In, addition to the source as nutritious food, fish, yield a number of by-products which are of, commercial value. They are fish oil, fish meal,, fertilizers, fish guano, fish glue and isinglass., These by-products are widely used in paints,, soaps, oils, and medicine. Prawns and Lobsters, have market value all over the world. Fishery, provides good job opportunities and self, employment to many people., , Eggs, , Mature, caterpillar, , Dorsal horn, , Spiracles, , Adominal pseudo, legs, , Head, Thoracic true, legs, , Fig. 11.8 : Life cycle of silk moth (Mulberry, silk worm), Internet my friend, Collect information about life cycle of, silk moth., The best quality silk called mulberry silk,, is produced by silkworm Bombyx mori, while, Tussar silk and Eri silk are of inferior quality., The quality and quantity of silk depends on the, quality of mulberry leaves on which the larvae, feed., Rearing, development and looking after, the silkworms, involve skill and labour for, constant watch. A little negligence can spoil, the complete industry. Silkworm larvae may, be infected by protozoans, viruses and fungi., Besides these, ants, crows, birds, and other, predators are ready to attack these insects,, hence the cages of these larvae must be, managed to prevent predators attack., , 257
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Fertilization, Egg laying, , Adult male, Complete, metamorphosis, , Male comes, out from anal, operculum, , End of egg laying, (Yellow spots indicate, , Life Cycle of Lac Insect, , Adult female, Incomplete, metamorphosis, , shrinking of female), , Hatching, (Orange spots indicate, eggs are about to hatch), , Pupa, , Larvae, (also called as crawlers), Larvae settling on host, , Fig. 11.9 : Life Cycle of Lac Insect, Can you tell?, 1. What are the different stages found in life, cycle of silkworm?, 2. Process of cocoon formation., 3. Which process is involved in silk, production from cocoon ?, G. Lac culture :, Lac is produced by an insect Trachardia, lacca, which is quite small in size and colonial, in habit. Resin like substance is produced by, Dermal glands of female lac insect. Insect feeds, on succulent twigs of certain plants like ber,, peeple, palas, kusum, babool, etc and secretes, pink coloured resin, that hardens on coming in, contact with air forming lac. It is produced on, a large scale all over India., Lac is a complex substance having large, amount of resin together with sugar, water,, minerals and alkaline substances., Natural lac is always contaminated., Shellac is pure form of lac obtained by washing, and filtering. Lac insect is a native of India and, our share is 85 % of total lac produced in the, world. Products of lac play a vital role in the, economy of the farmers. Lac is used in bangles,, toys, woodwork, inks, mirrors, etc. Production, , of lac requires an artificial inoculation of plants, which give better and regular supply of good, quality and quantity of lac., 11.7 Microbes in human welfare :, Biotechnology is the applications of, ‘Scientific and Engineering principles for the, processing of materials by biological agents, to provide goods and service to humans or for, human welfare’., There are variety of microorganisms like, algae, fungi, bacteria, viruses, protozoans,, nematodes, etc. and their products that exhibit, benificial activities which are used for welfare, of humans in regard to food, health, industry,, agriculture, medicine, biocontrol, etc. These, organisms are used variously in food and feed, technology, industry, waste utilization, energy,, etc., Microbes in food preparation :, The development of biotechnology, occurred in two phases viz, traditional (till, 1971) and modern (after 1970). Traditional, biotechnology is based on the fermentation, principle by using fermenting bacteria. These, were used in the preparation of variety of, indigenous fermented food products., , 258
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1. Dosa, Dhokla and Idli:, The dosa, idli and dhokla are fermented, products produced due to activity of bacteria., They are fermented preparation of rice and, black Gram with air borne Leuconostoc and, Streptococcus species of bacteria. CO2 produced, during fermentation causes puffing up of the, dough., Can you tell?, Name the microbes used in fermentation, of dhokla., Find out, Names of some edible mushrooms, and poisonous mushrooms., 2. Microbes as the Source of Food :, Some microbes or their fruiting bodies are, directly used as a source of food, as they are, rich in vitamins and proteins. The term “SCP”, or “single cell protein” denotes, dead and dried, cells of microbes like bacteria, algae, molds, and yeasts., Some mushrooms and truffles are directly used, as food. They belong to higher fungi. They, produce large, fleshy fruting bodies which are, edible. Fruting bodies are sugar free, fat free, but rich in proteins, vitamins, minerals and, amino acids. The food in the fruting body is, low caloried., 3. Dairy Products:, Lactic acid bacteria (LAB) like, Lactobacillus are added to milk. It ferments, lactose sugar of milk into lactic acid. Lactic, acid causes coagulation and partial digestion of, milk protein casein. Milk is changed into curd,, yoghurt and cheese. The starter or inoculum, used in preparation of milk products actually, contains millions of lactic acid bacteria (LAB)., i. Curd:, Indian curd is prepared by inoculating milk, with Lactobacillus acidophilus. It also checks, growth of disease causing microbes., , ii. Yoghurt (= yogurt):, It is produced by curdling milk with, the help of Streptococcus thermophilus and, Lactobacillus bulgaricus., iii. Butter Milk:, The acidulated liquid left after churning of, butter from curd, is called butter milk., iv. Cheese:, The milk is coagulated with lactic acid, bacteria and the curd formed is filtered to, separate whey. The solid mass is then ripened, with growth of mould that develops flavour in it., Different varieties of cheese are known by their, characteristic texture, flavor and taste which, are developed by different specific microbes., The ‘Roquefort and Camembert cheese’ are, ripened by blue-green molds Penicillium, roquefortii and P. camembertii respectively., The large holes in Swiss cheese are developed, due to production of a large amount of CO2, by a bacterium known as Propionibacterium, shermanii., 11.8 Role of Microbes in Industrial, Production:, During fermentation, variety of products, like alcoholic beverages, organic acids,, vitamins,, growth hormones,, enzymes,, antibiotics, etc. are produced., Do you know ?, These are actually the secondary, metabolites produced during idio phase and, are not required by micro-organisms for their, growth. The type of substrate and the type of, micro-organism result into the production of, particular secondary metabolites., Production on an industrial scale requires, growing microbes in very large vessels, called, fermenters. The main function of a fermenter is, to provide a controlled environment for growth, of a microorganism, or a defined mixture of, microorganisms, to obtain the desired product., , 259
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Yeast movement, , a. Production of Alcoholic Beverages :, Beverage is a liquid used or prepared for, drinking e.g. tea, coffee, beer, wine, which, acts as stimulant. Alcoholic beverages are, the products of alcoholic fermentation of, specific substrates. Use of microbes in malking, alcoholic beverages, is known since vedic, period- 5000 to 7000Bc., Microbes, especially, yeast, have, been used from time immemorial for the, production of beverages like wine, beer,, whiskey, brandy or rum. For this purpose,, the yeast Saccharomyces cerevisiae var., ellipsoidis (commonly called Brewer’s Yeast), is used for fermenting malted cereals and fruit, juices to produce ethanol. Among the, beverages, Wine and Beer are produced without, distillation whereas whiskey, brandy and, rum are distilled beverages. Tubular tower, fermenter is used for large scale production of, alcohols., Several traditional drinks and foods are, also made through fermentation by yeast., Today, a traditional drink of the coastal region,, in South India, is made by fermenting the sugar, sap extracted from palm plants and coconut, palm. The famous wine of Goa, traditionally, known as ‘fenny’ is made by fermenting fleshy, pedicels of cashew fruits., , directly from glucose (e.g. gluconic acid) or, formed as end products from pyruvate or, ethanol., Organic acid, Microbes used, i. Citric acid, Aspergillus niger, ii. Gluconic acid, Aspergillus niger, iii. Fumaric acid, Rhizopus arrhizus, iv. Acetic acid (vinegar), Acetobacter aceti, The organic acids are further used variously, e.g. citric acid is used in confectionary, fumaric, acid in resins as wetting agents and gluconic, acid in medicine for solubility of Ca++., c. Production of vitamins:, Vitamins are some organic nitrogenous, compounds which are capable of performing, many life-sustaining functions inside our body., These compounds cannot be synthesized by, humans (except vitamin D), and therefore they, have to be supplied in small amounts in the diet., Microbes are capable of synthesizing the, vitamins and hence they can be successfully used, for the commercial production of many, of the vitamins e.g. thiamine, riboflavin,, pyridoxine, folic acid, pantothenic acid, biotin,, vitamin B12, ascorbic acid, beta-carotene (provitamin A) and ergosterol (provitamin D)., Vitamins are manufactured by fermentation, using different microbial sources as mentioned, below:, Name of the vitamin, Microbial source, i. Vitamin B2, , Alcohol, , i. Neurospora gossypii, ii. Eremothecium ashbyi, , ii. Vitamin B12, , Fermenter, , Pseudomonas denitrificans, , iii. Vitamin C Aspergillus niger, Can you recall?, Heat exchanger pump, , 1. What are antibiotics?, 2. Who invented first antibiotic?, , Fig. 11.10 : Tubular tower fermenter, b. Production of organic acids:, Microbes are also used for the commercial, and industrial production of certain organic, acids. These compounds can be produced, , d. Production of Antibiotics:, Antibiotics are probably the most important, group of compounds synthesized by industrial, , 260
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microorganisms. Most antibiotics are secondary, metabolites. They have therapeutic importance, and are used in medical treatment. These are, produced in small amounts by certain microbes, (like bacteria, fungi and few algae), which, inhibit growth of other microbial pathogens., Therefore, they are used in medicine. The, antibiotics are antibacterial, antifungal, etc., Antibiotics have greatly improved our, capacity to treat deadly diseases such as, plague, whooping cough, diphtheria, leprosy,, etc., Use your brain power, Can antibiotics kill viruses?, Some common antibiotics and their, microbial sources are listed below :, Table 11.11 : Antibiotic producing microbes, Antibiotic produced Microbial sources, Chloromycetin, , Streptomyces, venezuelae, Streptomyces, erythreus, Penicillium, chrysogenum, Streptomyces griseus, , Erythromycin, Penicillin, Streptomycin, Griseofulvin, Bacitracin, , Penicillium, griseofulvum, , Enzymes are proteins known as biocatalysts. Due to their ability to promote, reactions more quickly at body temperature and, more efficiently. Many microbes synthesize, and excrete large quantities of enzymes, into the surrounding medium. Using this, feature of these tiny organisms, many enzymes, are produced commercially. These enzymes, are Amylase, Cellulase, Protease, Lipase,, Pectinase, Streptokinase and many others., Several industrial sectors, use enzymes, from microorganisms for specific applications., In the textile industry, enzymes are able to, improve the quality of the fabrics. In the, pulp and paper industry, they are involved in, biomechanical pulping and bleaching, in the, food industry, they are used in the fermentation, processes for the production of bread and, drinks such as wine and beer, also they, participate in the extraction of substances, such, as carotenoids and olive oil; lipases are used in, detergent industry, because they have superior, cleaning properties, increasing the brightness, and removing of oil stains; they are also used, in cosmetics, animal feed and agricultural, industries, among others. Following are the, few examples of enzymes used in industrial, food processing:, Name of the enzyme Microbial source, , Bacillus licheniformis, , Oxytetracycline /, Terramycin, , Streptomyces, aurifaciens, , Can you recall?, What are Enzymes? How are they, classified?, e. Production of Enzymes:, In living beings, enzymes play a key role, in metabolic reactions and therefore, these are, essential for the survival of such beings., , Invertase, , Saccharomyces cerevisiae, , Pectinase, , Sclerotinia libertine,, Aspergillus niger, , Lipase, , Candida lipolytica, , Cellulase, , Trichoderma konigii, , f. Gibberellin production:, Gibberellin is a group of growth hormones, mainly produced by higher plants and fungi, to promote growth by stem elongation. The, first gibberellin was isolated by two Japanese, scientists -Yabuta and Sumiki (1938) from rice, seedlings infected with the fungus Gibberella, fujikouri., , 261
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Extra information: Streptokinase enzyme, (TPA) is produced by the bacterium, Streptococcus spp. It has fibrinolytic effect., Hence, it is used as a ‘clot buster’ for clearing, blood clots in the blood vessels of patients,, which may cause heart attack., Statins produced by the yeast Monascus, purpureus have been produced on commercial, scale. It is a blood-cholesterol lowering agent., This agent acts as competitive inhibitor, of the enzyme responsible for synthesis of, cholesterol., , Do you know ?, The oil eating bacteria can clean up, crude spills. Collect more information about, these bacteria., , About 15 different types of gibberellins, have been isolated. Gibberellins have many, practical applications. They are used to induce, parthenocarpy in apple, pear, etc. They are, used in breaking the dormancy of seed and, also in inducing flowering in Long Day Plants, (LDP). They are also used to enlarge the size, of grape fruits., 11.9 Microbes in Sewage Treatment:, Sewage is a matter carried off, in, drainage. It is a municipal waste containing, human excreta, house hold waste, dissolved, organic matter and even pathogenic microbes, (bacteria, viruses, protozoans, nematodes and, microfungi). It also includes discharged water, from hospital waste, slaughter house waste,, animal dung, etc. Discharge from industrial, waste (contains toxic dissolved organic and, inorganic chemicals), tannery, pharmaceutical, waste, etc. also add to sewage., Extra Information : Sewage is also a, potential source of pathogenic bacteria,, viruses and protozoa. The causative agents, of dysentery, cholera, typhoid, polio and, infectious hepatitis may occur in sewage., The bacteria from the soil are also present, in the sewage. During the course of sewage, decomposition,, initially, aerobic, and, facultative anaerobic organisms predominate, which are then followed by strict anaerobic, especially methogenic bacteria that produce, methane (CH4) and CO2., , Composition of Sewage:, Sewage consists of approximately 99.5%, to 99.9% water and 0.1 to 0.5% inorganic and, organic matter in suspended and soluble form., Composition of sewage varies depending upon, the type of waste discharged into water from, different industries. e.g. textile, chemicals,, pharmaceuticals, dairy, canning,, brewing,, meat packing, tannery, oil refineries and meat, industries, etc., Microorganisms in Sewage:, Various types of micro-organisms are, also present in sewage. Bacteria, viruses,, fungi, protozoa, nematodes, algae, etc. are, found in sewage. However, their number and, type, fluctuate depending upon the sewage, composition and source of sewage. Raw, sewage may contain millions of bacteria per, ml. These include coliforms, fecal Streptococci,, anaerobic spore forming bacilli and other types, originating in the intestinal tract of humans., Before waste water is made available for, human use, it has to be treated properly, so as, to remove organic matter, inorganic salts and, pathogens as well. Sewage treatment process, includes four basic steps as follows:, 1. Preliminary Treatment:, The preliminary treatment includes, Screening and Grit Chamber., i. Screening : Sewage and waste water, contains plenty of suspended, floating, materials, coarse and solid particles along, with dissolved substances. The suspended, objects are filtered and removed. This is, done in screening chambers. The sewage, is passed through screens or net in the, chambers. Larger suspended or floating, objects are held back in the screening, , 262
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chambers. These have to be removed before, the biological treatment., ii. Grit Chamber : After screening, the filtered, sewage is then passed into series of grit, chambers. These chambers contain large, stones (pebbles) and brick-ballast. Coarse, particles settle down by gravity. Thus,, passage of filtered sewage removes much of, the coarse particulate matter., , mechanically and air is pumped into it. Aerobic, bacteria grow vigourously and form flocs., Flocs are the masses of bacteria held together, by slime and fungal hyphae to form mesh like, masses. These aerobic microbes consume the, major part of the organic matter present in, the effluent, as they grow. Due to this BOD, (Biochemical Oxygen Demand) of the effluent, is significantly reduced., , 2. Primary treatment (physical treatment):, After the preliminary treatment, the, sewage water is pumped into the primary, sedimentation tank. The sedimentation of, suspended solid or organic matter occurs in, this tank. About 50-70% of the solids settle, down. There is reduction of about 30-40% (in, number) of coliform organisms. The organic, matter which is settled down, is called primary, sludge which is removed by mechanically, operated devices. The supernatant (effluent) in, the primary sedimentation tank still contains, large amount of dissolved organic matter and, micro-organisms which can then be removed, by the secondary treatment., , 4. Tertiary treatment:, Once the BOD of waste water is reduced, it, is passed into a settling tank. Here the bacterial, flocs are allowed to sediment. The sediment, is now called activated sludge. Small part of, this is passed back in to aeration tank and the, major part is pumped in to large tanks called, anaerobic sludge digesters. In these tanks,, anaerobic bacteria grow and digest the bacteria, and fungi in the sludge. During this anaerobic, digestion, gases such as methane, hydrogen, sulphide, CO2, etc. are produced. Effluents, from these plants (digester) after chlorination,, are released in natural water bodies like rivers, and streams. Chlorination kills pathogenic, bacteria. Digested Sludge is then disposed., , 3. Secondary, treatment, (biological, treatment):, The primary effluent is passed into large, aeration tanks. Here it is constantly agitated, Screening, , Grit setting, , Primary treatment, , Waste, water, Removal of suspended, solid particles, , Preliminary treatment to, remove heavy solids, , Secondary, Treatment, , Settled sewage, Tertiary treatment, Aeration, Treated, tank, Effluent, (Aerobic bacteria), , Activated sludge, Water to recycle, Anaerobic bioreactor, (digester), , Sludge cake, to dispose, , (Anaerobic bacteria), , Fig. 11.12 : Diagrammatic representation of various stages in wastewater treatment, 263
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11.10 Microbes in Energy Genration :, Many, developing, countries, are, encouraging for installation of biogas plants, to meet out the requirement of energy. Biogas, is used as a domestic as well as industrial, fuel. It is a non-conventional and renewable, source of energy and is obtained by microbial, fermentation. Biogas is a mixture of methane, CH4 (50-60%), CO2 (30-40%), H2S (0-3%) and, other gases (CO, N , H ) in traces. Biogas is, 2, , Biogas, Gas-holder, Dung water, , (CH4+CO2+. ... ), , Sludge, , Charge pit, , 2, , highly inflamable and is used as a source of, energy., , Digester, , Plant wastes, animal wastes, domestic, wastes, agriculture waste, municipal wastes,, forestry wastes, etc. are commonly used, for biogas production. Cattle dung is most, commonly employed substrate for biogas, production. It is a rich source of cellulose from, plants., Biogas Production:, Most commonly used models of biogas, plants are KVIC and IARI. The digester used, for biogas production is called Biogas Plant. A, typical biogas plant using cattle dung as a raw, material, consists of digester and gas holder., Digester is made up of concrete bricks and, cement, or steel. There is cylindrical gas holder, or gas tank above it to collect gases. Digester, has a side opening (charge pit) into which raw, material as cow dung is fed. The digester is, partly burried in the soil., Anaerobic digestion involves in three, processes :, i., , Hydrolysis or solublization : In initial, stage raw material (cattle dung) is mixed, with water in equal proportion to make, slurry which is then fed into the digester., Here anaerobic hydrolytic bacteria (e.g., Clostridium, Pseudomonas) hydrolyse, carbohydrates into simple sugars, proteins, into amino acids and lipids into fatty acids., , Fig. 11.13 : Biogas plant, ii. Acidogenesis : In this stage, facultative, anaerobic, acidogenic bacteria and obligate, anaerobic organisms, convert simple, organic material into acids like formic, acid, acetic acid, H2 and CO2., iii. Methanogenesis :, This is last stage in which anaerobic, Methanogenic bacteria like Methanobacterium,, Methanococcus convert acetate, H2 and CO2, into Methane, CO2 and H2O and other products., 1. 12mol CH3COOH, 12CH4 + 12CO2, (acetic acid), , 2. 4mol H.COOH, (formic acid), , 3. CO2 + 4H2, , methane, , CH4 + 3CO2 + 2H2O, CH4 + 2H2O, , Benefits:, It is a cheap, safe and renewable source of, energy. It can be easily generated, stored, and transported., It can be used for domestic lighting,, cooking, street lighting as well as small, scale industries., It burns with blue flame and without smoke., It helps to improve sanitation of the, surrounding., It iseco-friendly and does not cause pollution, and imbalance of the environment. Sludge, which is left over is used as a fertilizer., , 264
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11.11 Role of Microbes as Biocontrol Agents:, , Table 11.14 : Microbes and their host, , The term biocontrol refers to the use of, biological methods to control diseases and, pests. The natural method of eliminating and, controlling insects, pests and other diseasecausing agents, is by using their natural,, biological enemies. This is called biocontrol, or biological control., , Pathogen, Bacteria:, Bacillus, thuringiensis (Bt), B., papilliae, and, B.lentimorbus, Fungi:, Beavueria bassiana,, Entomophthora., pallidaroseum, and, Zoopthora radicans, Protozoans:, Nosema lacustae, , The agents which are employed for this, are called biocontrol agents. Microbes are one, among them. These microbes include bacteria,, fungi, viruses and protozoans. Microbes as, biocontrol agents act in three ways, either they, cause the disease to the pest or compete or kill, them. Chemicals, insecticides and pesticides, are extremely harmful to human beings and, also pollute our environment. Hence, the use, of biocontrol measures will greatly reduce our, dependence on toxic chemicals and pesticides., , Host, Caterpillars,, cabbage worm,, adult beetle,etc., Aphid crocci,, A., unguiculata,, mealy bugs, mites,, white flies etc, , Grasshopper,, caterpillars,, crickets, Viruses:, Caterpillars, and, Nucleopolyhedrovirus Gypsy moth, ants,, (NPV) and Granulovirus wasps and beetles., (GV), , Examples of Microbial bio-control :, , Bioherbicides :, , i., , Weeds are the unwanted plants that grow, in agricultural fields, ponds, lakes, etc. Weeds, compete with the main crop in the farm- land for, water, space, minerals, light, air, etc. and also, act as collateral hosts for several pathogens., Microbes are also used as herbicides. Many, dicot herbs that grow in the field of cereals as, weeds, can be killed by certain microbes. For, examples :, , Bacillus thuringiensis (Bt) is used to get, rid of butterfly, caterpillars where dried, spores of Bacillus thuringiensis are mixed, with water and sprayed onto vulnerable, plants such as Brassicas and fruit trees., These spores are then eaten by the insect, larvae. In the gut of the larvae, the toxin, (cry protein) is released and the larvae get, killed eventually., , ii. Trichoderma species are free-living fungi, found in the root ecosystem (rhizosphere)., These are effective as biocontrol agents of, several soil borne fungal plant pathogens., The fungus produces substances like, viridin, gliotoxin, gliovirin, etc. that inhibit, the other soil borne pathogens attacking, root, rhizomes, etc. causing rot disease., , II. Microbial Herbicides and Their Host :, , Four groups of biocontrol agents are, known. They are bacteria, fungi, viruses and, protozoans., I. Microbial Pesticides and their host :, The corelation is depicted as per the, following table :, 265, , Pathogenic fungi as mycoherbicides:, iii. Phytophthora palmivora - controls milk, weed in orchards., iv. Alternaria, hyacinth., , crassa, , -, , controls, , water, , v. Fusarium spp.- control most of the weeds., Bacterial pathogen as herbicides:, i., , Pseudomonas spp.- attacks several weeds, , ii. Xanthomonas spp.- attacks several weeds, iii. Agrobacterium spp.- attacks, weeds, , several
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3. Insects as herbicides :, i., , 1., , N2 fixing Biofertilizers: The nitrogen, fixing microorganisms which convert, atmospheric nitrogen into nitrogenous, compounds like nitrites and nitrates via, ammonia. Nitrogen fixing microorganisms,, also called diazotrophs, are of two types:, iii. Symbiotic N2 fixing microorganisms:, for eg. Rhizobium, Anabaena, Frankia., These are always associated generally, with underground parts i.e. roots of, higher plants., iv. Free-living or Non- Symbiotic N2 fixing, microorganisms:, e.g., Azotobacter,, Nostoc,, Clostridium,, Beijerinkia,, Klebsiella, etc., , 2., , Phosphate solubilizing biofertilizers:, These are the bacterial species which, solubilize the insoluble inorganic, phosphate compound, such as rock, phosphate. For eg. Pseudomonas striata,, Bacillus, polymyxa, Agrobacterium,, Microccocus, Aspergillus spp., etc., , Tyrea moth - controls the weed Senecio, jacobeac, , ii. Cactoblastis cactorum - controls cacti, weeds., 11.12 Role of Microbes as Biofertilizers:, Fertilizers are nutrients which are, necessary for the growth of plants and thus, for the productivity of cultivated plants. Use, of fertilizers for increasing productivity is one, of the aspects of green revolution. Fertilizers, are classified as inorganic (chemical) and, organic (biological). Inorganic fertilizers, are synthetic where mineral salts of NPK are, mixed in definite proportion and then dusted, in the field. Non-judicious or excessive use of, such fertilizers lead to pollution of soil, air and, ground water. Soil becomes acidic., Organic fertilizers are biological in origin, and include Farm Yard Manure (FYM),, compost and green manure. Use of these, fertilizers increases the fertility of soil., , 3. Compost making biofertilizers:, Composting is a natural process that, turns organic material into a dark rich, substance called as compost or humus., The composting process is dependent, on microorganisms to break down, organic matter into compost. There are, many types of microorganisms found in, active compost such as bacteria, fungi,, actinobacteria, protozoa and rotifers., , Now a days for better and sustainable, agricultural, production, farmers, use, biofertilizers and practise organic farming., Biofertilizers are mostly N2 fixing, living, microorganisms which enrich the nutrient, quality of soil. They include bacteria,, cyanobacteria and fungi., Biofertilizers are commercial preparation, of ready-to-use live bacterial or fungal, formulations. Their application to plant, soil or, composting pits, helps to enrich the soil fertility, due to their biological activity., Use of Biofertilizers is cost effective, and eco-friendly. They play a vital role in, maintaining a long term soil fertility and, sustainability., , 4. Cyanobacteria as biofertilizers :, Many cyanobacteria are aquatic and, terestrial, free-living or symbiotic, aerobic,, photosynthetic, N2 fixing, heterocystous or, non-heterocystous forms. e.g. Anabaena,, Nostoc, Plectonema, Oscillatoria, etc., Anabaena, Nostoc and Tolypothrix are, associated with lichens while Anabaena, is associated with plants like Azolla and, Cycas., , Types of Biofertilizers:, On the basis of nature and function, biofertilizers are divided into following groups266
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less irrigated lands. The association of VAM, with crop plants helps in conversion of less, productive field into more productive field., , Do you know ?, Classification of Biofertilizers :, On the basis of nature or group of, organisms, biofertilizers are classified as, bacterial fertilizers and fungal fertilizers., Bacterial fertilizers include eubacteria, and cyanobacteria. On the basis of function,, bacterial fertilizers are further grouped as, nitrogen fixing, phosphate solubalizing and, compost making biofertilizers. Cynobacterial, biofertilizers, on the basis of function, are, nitrogen fixing type., Fungal, biofertilizers, include, mycorrhizal fungi. On the basis of function,, they are classified as ectomycorrhizae and, endomycorrhizae., , Benefits of Mycorrhiza :, 1. Selective absorption of P, Zn, Cu, Ca, N,, Mn, Br and Fe., 2. Enhance water uptake., 3. Induce growth by secreting hormones., 4. Offer protection to host plant from other, microbes, by secreating antibiotics., Do you know ?, , 5. Fungal biofertilizers:, Mycorrhiza is a fugus. It forms symbiotic, association with the underground parts like, rhizomes and root of higher plants occuring, in thick humid forests. These are discovered, by Frank (1885). Their are two types viz,, Ectomycorrhizae and Endomycorrhizae., , , Ectomycorrhizae: They have well, developed mycelium that forms mantle, on the outside of the roots. This increases, absorptive surface area of roots and, accelerates uptake of water and nutrients (N,, P, Ca and K). Due to this the plant vigour,, growth and yield increase. Some hyphae of, mycorrhizal fungus, penetrate into the root, and forms hartig-net in the intercellular, spaces of root cortex., , Endomycorrhizae: They grow in between, and within the cortical cells of roots. Fungal, hyphae penetrate the cells and form finely, branched arbuscules intracellularly and, form vesicles mostly in the intercellular, speces of cortical cells. Hence they are called, Vesiculo Arbuscular Mycorrhizae or VAM., Now a days they are described as AM fungi., The plants with VAM grow luxuriantly in, , Now a days, mycorrhiza are classified, into 8 different types viz, Ectomycorrhizae,, Endomycorrhizae,, Ectendomycorrhizae,, Orchidaceous, mycorrhizae,, Ericoid, mycorrhizae,, Arbutoid, mycorrhizae,, Monotrapoid mycorrhizae and Ophioglossoid, mycorrhizae., Use your brain power, Why are healthy root nodules pink in, colour?, Biofertilizer microorganisms:, 1. Rhizobium: Rhizobia are rod shaped,, motile, aerobic, gram negative, non, spore forming, nitrogen-fixing bacteria, containing Nod genes and Nif genes. They, form symbiotic association with roots, of leguminous plants. They bring about, nodule formation on the roots and multiply, inside the nodule. They fix atmospheric, nitrogen into organic forms, which can, be used by plants as nutrients. For eg. R., leguminosarum is specific to pea. and R., phaseoli to beans., 2. Azotobacter: It is the important and well, known free living, nitrogen fixing, aerobic,, non-photosynthetic, non-nodule forming,, bacterium, intimately associated with roots, of grasses and certain plants. It is used as a, Bio-fertilizer for all non-leguminous plants, especially rice, cotton, vegetables, etc., , 267
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Root nodules, , Root branch, , Fig. 11.17 : Azolla, , Fig. 11.15 : Root system of Leguminous, plant, , Photosynthetic zone, Root nodule, Anabaena, , Root, , Bacterial colonies, in cortical cells, , Cavity, Dorsal lobe, , Xylem, , Phloem, , Fig. 11.18 : L. S. of Azolla leaf showing, filamentous Anabaena, , Fig. 11.16 : T. S. of root nodule, , In the dorsal lobe, Anabaena filaments, are present in the aerenchyma, which fixes, nitrogen. Azolla can be used as biofertilizer, in the rice field., , 3. Azospirillum: It is free living, aerobic, nitrogen fixing bacterium associated with, roots of corn, wheat and jowar. It fixes the, considerable quantity of nitrogen (20-40kg, N/ha) in non – leguminous plants such as, cereals, millets, cotton, oilseed, etc., , Benefits of Biofertilizers :, 1. Low cost and can be used by marginal, farmers., 2. Free from pollution hazards., 3. Increase soil fertility., 4. BGA as biofertilizers secret growth, promoting substances, organic acids,, proteins and vitamins., 5. Azotobacter supply nitrogen and, antibiotics in the soil., 6. Biofertilizers increase physico-chemical, properties of soil- like texture, structure,, pH, water holding capacity of soil by, providing nutrients and organic matter., , 4. Anabaena : It is a genus of multicellular,, filamentous cyanobacteria that exits as, plankton. It has ability to fix nitrogen and, also forms symbiotic relationships with, certain plants, such as the coralloid roots of, Cycas and Anthoceros thallus. It has some, specialized and colourless cells, called, Heterocysts which are the sites for nitrogen, fixation., 5. Azolla: Azolla is a free-floating water fern., Azolla plant consist of a floating rhizome, (stem) with small overlapping bi-lobed, leaves and roots. The leaf shows dorsal and, ventral lobe., , Now in our country many biofertilizers, are available in market to reduce the use of, chemical fertilizers and thus, the pollution., , 268
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Activity :, 1. Visit fish market and enlist different types of fresh water and marine water fish, mentioning their local names and scientific names., Type, , Local Name, , Scientific Name, , Detail Information, , 1., 2., 3., 4., 5., 6., 7., 2. Label the different parts of the fermenter and mention functions of each part., , 269
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Exercise, Q. 1 Multiple Choice Questions., , 8. MOET technique is used for ............, a. production of hybrids, b. inbreeding, c. outbreeding, d. outcrossing, 9. Mule is the outcome of .............., a. inbreeding, b. artificial insemination, c. interspecific hybridization, d. outbreeding, , 1. Antibiotic Chloromycetin is obtained, from ....................., a. Streptomyces erythreus, b. Penicillium chrysogenum, c. Streptomyces venezuelae, d. Streptomyces griseus, 2., , Removal of large pieces of floating, debris, oily substances, etc. during, sewage treatment is called ................, a. primary treatment, b. secondary treatment, c. final treatment, d. amplification, , 3. Which one of the following is free living, bacterial biofertilizer?, a. Azotobacter, b. Rhizobium, c. Nostoc, d. Bacillus thuringiensis, 4. Most commonly used substrate for, industrial production of beer is ............., a. barley, b. wheat, c. corn, d. sugarcane molasses, 5. Ethanol is commercially produced, through a particular species of .............., a. Aspergillus, b. Saccharomyces, c. Clostridium, d. Trichoderma, 6. One of the free-living anaerobic, nitrogen-fixer is ....................., a. Azotobacter, b. Beijerinckia, c. Rhodospirillum, d. Rhizobium, 7. Microorganisms also help in production, of food like ................., a. bread, b. alcoholic beverages, c. vegetables, d. pulses, , Q. 2 Very Short Answer Questions:, 1. What does make idlies puffy?, 2. Name any two bacterial biofertilizers., 3. What is the microbial source of vitamin, B12?, 4. What is the microbial source of enzyme, Invertase?, 5. Milk start to coagulate when Lactic, Acid Bacteria (LAB) is added to warm, milk as a starter. Mention any two other, benefits of LAB., 6. Name the enzyme produced by, Streptococcus, bacterium., Explain, importance in medical sciences., 7. What is breed?, 8. Define estuary., 9. What is shellac?, Q. 3 Short Answer Questions., 1. Many microbes are used at home during, preparation of food items. Comment on, such useful ones with examples., 2. What is biogas? Write in brief about the, production process., 3. Write a note on biocontrol agents., 4. Name any two enzymes and antibiotics, with their microbial source., 5. Write priciples of farm management., 6. Give economic importance of fishery., 7. Enlist the species of honey bee mentioning, their specific uses., , 270
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8. What are A, B, C and D in the table given, below :, Types of, Name, microbe, Fungus, , Commercial, product, A, , Penicillin, , Bacterium Acetobacter aceti, , B, , C, , Aspergillus niger, , Citric acid, , Yeast, , D, , Ethanol, , Q. 4 Long Answer Questions., 1. Explain the process of sewage water, treatment before it can be discharged, into natural bodies. Why this treatment is, essential?, 2. Write a note on lac culture., 3. Describe various methods of fish, preservation., 4. Give an account of poultry diseases., 5. Give an account of mutation breeding, with examples., 6. Describe briefly various steps of plant, breeding methods., , Project :, Collect information about, A) Different types of worms/organisms used in sericulture, B) How is silk obtained and isolated, C) Types of silk, D) Job potential of sericulture, , 271
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12, , Biotechnology, Can you recall?, , 1. What is Biotechnology?, 2. How do genetically modified organisms, are produced?, 3. Which are the benefits of Biotechnology?, You are already aware of what, biotechnology is. It is the product of interaction, between the biological science and technology., It is infact, an applied branch of biology. The, term biotechnology was first used by Karl, Ereky in 1919 to describe a process for large, scale production of pigs., 12.1 Biotechnology, It is defined by different organizations in, different ways. It has been brodly defined as, ‘the development and utilization of biological, forms, products or processes for obtaining, maximum benifits to man and other forms of, life’. According to OECD (Organization for, Economic Cooperation and Development,, 1981)- ‘It is the application of scientific and, engineering principles to the processing of, materials by biological agents to provide, goods and service to the human welfare’., It uses scientific priciples of microbiology,, genetics biochemistry, chemical engineering,, mathematics, statistics, computers, industrial, processes, etc. Biological agent means plants, and animal cells, microorganisms, enzymes or, their products., History of origin of biotechnology is as, old as human civilization. Development of, biotechnology in terms of its growth, occurred, in two phases viz, Traditional biotechnology, and Modern biotechnology., Traditional, biotechnology, (old, biotechnology) was primarily based on, fermentation technology using microorganisms, as in the preparation of curd, ghee, soma,, , vinegar, yogurt, cheese making, wine making,, etc. It became an art of kitchen in indian, houses. It was more an art than science. Till, that time people did not know as to how exactly, the process occurs and the organisms causing, this process. The contributions made by several, chemists, biochemists and microbiologist,, over the time, could explain the mechanism of, process and also the nature of microorganisms, causing the process., During 1970 a new technique of, ‘recombinant DNA technology was developed, and then established by Stanley Cohen and, Herbert Boyer in 1973. This technique has, changed the overall outlook, then. The technique, permits to change/ modify genetic (heritable), material for getting new specific products., The combination of biology and production, technology based on genetic engineering, evolved into modern biotechnology (new, biotechnology)., There are two major features of technology, that differenciate modern biotechnology from, classical or old biotechnology viz,, i., , Capablity of science to change the genetic, material for getting new specific products, through rDNA technology, polymerase, chain reaction (PCR), microarrays, cell, culture and fusion, and bioprocessing., , ii. Ownership of technology and its sociopolitical impact., Now, the, conventional, industries,, pharmaceutical industries, agro industries,, food industries, etc. are also focussing attention, to produce biotechnology- based products., 12.2, Principles, and, Processes, of, Biotechnology :, Modern biotechnology is based on two, core techniques viz. genetic engineering and, chemical engineering., , 272
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Genetic engineering deals with alteration, of genetic material (DNA and RNA) while, chemical engineering deals with maintaining, sterile environment, for, manufacturing, variety of useful products including vaccines,, antibodies, enzymes, organic acids, vitamins,, therapeutics, etc., Genetic engineering is defined as the, manupulation of genetic material towards a, desired end and in a directed and predetermined, way, using in vitro process. Manipulation, of genes involve repairing of the defective, genes or replacing of defective genes by, healthy genes or normal genes; artificially, synthesizing of a totally new gene; transfer, of genes into a new location or into a new, organism; introducing an all together new, gene; manipulation of genes for improvement, of living organisms; combining of genes from, two organisms, altering the genotype; gene, cloning etc. Therefore, the genetic engineering, is alternatively called recombinant DNA, technology or gene cloning., Extra information :, John E. Smith (1996) gave definition of, genetic engineering as ‘the formation of new, combination of heritable material by the, insertion of nucleic acid molecule produced, by whatever means outside the cells, into any, virus, bacterial plasmid or other vector system, so as to allow their incorporation into a host, organism in which they do not occur naturally, but in which they are capable of continued, propagation’., Technique of gene cloning and rDNA, technology :, In gene cloning, a gene of known function, can be transferred from its normal location, into a cell (that of course does not contain it), via a suitable vector. The transferred gene is, replicated normally and is handed over to the, next progeny., , A. Tools and techniques for gene cloning/, rDNA technology :, Before we venture into a procedure of, gene cloning, let us know briefly, the basic, requirements for the technique., I. Different instruments (devices) :, Macromolecule such as DNA, RNA,, proteins, etc. are synthesized in the living, cells which vary in their molecular weight,, solubility, presence of charges, absorbance, of light, etc. Several techniques are used to, isolate and charaterize the macromolecules., The size of different types of molecules, varies and therefore their molecular, weights also vary. The techniques used, on the basis of molecular weight, are, gel permeation, osmotic pressure, ion, exchange chromatography, spectroscopy,, mass spectrometry, electrophoresis, etc., Electrophoresis is the separation of charged, molecules, applying an electric field. It, is applied for the separation of DNA,, RNA and proteins. DNA being negatively, charged, migrates to anode. Small, fragments of DNA molecules, move faster, and thus separate faster. Use of Agarose gel, electrophoresis, PAGE, SDA PAGE are the, different methods of electrophoresis., Polymerase chain reaction (PCR) :, Polymerase chain reaction (PCR) is, another device used for gene cloning or gene, multiplication in vitro. It is the amplification of, gene of interest, through PCR., In 1985, Kary Mullis made an important, discovery (contribution) in the form of, an extremely powerful technique called, polymerase chain reaction (PCR). PCR can, generate a billion copies of the desired segment, of DNA or RNA, with high accuracy and, specificity, in a matter of few hours. The process, of PCR is completely automated and involves, automatic thermal cycles for denaturation, and renaturation of double stranded DNA., , 273
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1 copy of desired gene, , The device required for PCR is called thermal, cycler., PCR is in vitro amplification of a desired, DNA segment, which requires : DNA containing, the desired segment to be amplified, several, molecules of four deoxyribonuclueoside, triphosphates (dNTPs), excess of two primer, molecules, heat stable DNA polymerase and, appropriate quantities of Mg++ ions., , 1, Denaturation (90-98 0C), , First cycle completes, , DNA strands, separated, , Internet my friend, Collect the information from internet, about PCR machine., , 2, Annealling of primers, (40-60 0C), Replicating DNA, strands using, Tag polymerase, (70-75 0C), , 3, 2 copies of, desired gene, (renaturation), , Second cycle continues to form, 4 copies of desired DNA, , Mechanism of PCR:, At the start of PCR, the DNA segment,, and excess of two primer molecules, four, deoxyribonucleosides triphosphates and the, thermostable DNA polymerase are mixed, together in ‘eppendorf tube’ and the following, operations are performed sequentially (Figure)., Step i : The reaction mixture is heated to a, temperature (90–98 oC) to separate two strands, of desired DNA. This is called denaturation., Step ii : The mixture is allowed to cool (40–, 60 oC) that permits pairing of the primer to the, complementary sequences in DNA. This step, is called annealing., Step iii : The temperature (70–75 oC) allows, thermostable Taq DNA polymerase to use, single-stranded DNA as template and adds, nucleotides. This is called primer extension. It, takes arround two minutes duration., , Cycle continous to produce, 2n copies of DNA, , Fig. 12.1 : DNA replication through, polymerase chain reaction., One cycle takes arround 3 to 4 minutes., To begin second cycle, DNA is again heated, to convert double stranded DNA into single, strands., In an automatic thermal cycler, the above, three steps are automatically repeated 20-30, times. Thus, at the end of ‘n’ cycles 2n copies, of DNA segments, are produed. The machine, performs the entire operations automatically, and precisely., Once the desired number of cycles is, completed, the amplified DNA segment is, purified by gel electrophoresis. After its, sequencing, the amplified DNA segment can be, inserted into a cloning vector. Desired gene can, also be obtained from gene library., , 274
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II. Biological tools :, There are three types of biological tools, used viz, enzymes, cloning vectors (vehicle, DNA) and competent host (cloning organisms), for transformation with recombinant DNA., A. Enzymes : Different enzymes include, Lysozymes, Nucleases such as exonucleases, endonucleases, restriction endonucleases,, DNA ligases, DNA polymerases, alkaline, phosphatases, reverse transcriptases, etc., i. Restriction enzymes :, Enzymes that cut the phosphodiester bands, of polynucleotide chains are called nuclease., There of two types - exonuclease and, endonuclease. Exonucleases cut nucleotides, from the ends of DNA strands whereas, endonuclease cut DNA from within. During, the 1970s, it was found that bacteria contain, nucleases that would recognize short nucleotide, sequence with duplex DNA and cut., The phosphodiester back bone at highly, specific sites on both strands of duplex, is, cut by these enzymes, called restriction, endonucleases or simply restriction enzymes., They were given this name because they, are used by the bacteria to destroy various, viral DNAs that might enter the cell, thereby, restricting the potential growth of the virus., , Thus, restriction enzymes serve as defence, mechanism. The bacteria protect its own DNA, from nucleolytic attack by methylating the bases, at susceptible sites, a chemical modification, that blocks the action of the enzyme., The restriction enzymes are thus the, molecular scissors that are used to recognize, and cut DNA at specific sequences. The sites, recognized by them, are called recognition, sequences or recognition sites. Different, restriction enzymes found in different organisms, recognize different nucleotide sequences and, therefore cut DNA at different sites. Table, encloses list of some restriction endonucleases, and the site at which they cleave DNA., , Activity :, Find out the biological source of following, restriction enzymes and discuss the their, recognition sequences :, Pst I, Sal I, Taq I, Xer III, Mbo II, Hpa I,, BgII, Kpn I, Not I., ii. Recognition sequences :, The sequences recognized by restriction, enzymes are 4 to 8 nucleotides long and, characterized by a particular type of internal, symmetry. Consider the particular sequence, recognized by the enzyme EcoRI ., , Table 12.2 : Source and recognition sequences (indicated by arrow) of various restriction enzymes:, Restriction, Enzyme, , Source, (Organism and, strain), , Recognition sequence, , 5’, , Alu I, , ---A- G- -C -T--- 3’, 3’, ---T- C- -G-A--- 5’, , Arthobacter luteus, , Bacillus, Bam HI, amyloliquefaciens H, EcoRI, , Escherichia coli, Ry13, , Hind II, , H. influenzae Rd, , 5’, , ---G- -G-A-T-C-C---3’, 3’, ---C-C-T-A-G- -G---5’, 5’, , Product, , 5, , End, products, produced, Blunt ends, , ---A-G, C-T---3, 3, ---T-C, G-A---5, 5, ---G G-A-T-C-C---3 Sticky ends, 3, ---C-G-T-A-G G---5, , ---G- -A-A-T-T-C---3’ 5---G A-A-T-T-C---3 Sticky ends, ---C-T-T-A-A- -G--- 5’ 3---C-T-T-A-A G---5, 5’, G-A-C--3’ Blunt ends, --G-T-C- -G-A-C--3’ 5’--G-T-C, 3’, 3’, --C-A-G, C-T-G--5’, --C-A-G- -C-T-G--5’, , 3’, , 275
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3’------- C T T A A G, , 5’, , 5’------- G A A T T C, , 3’, , host cell. Vectors may be plasmids,, bacteriophages (M13, lambda virus),, cosmid, phagemids, BAC (bacterial, artificial chromosome), YAC (yeast, artificial, chromosome),, transposons,, baculoviruses and mammalian artificial, chromosomes (MACs),. Most commonly, used vectors are plasmid vectors (pBR, 322, pUC, Ti plasmid) and bacteriophages, (lamda phase, M13 phage). Plasmids and, bacteriophages are most commonly used as, vectors., , When one reads the sequence in opposite, direction (3’ to 5’ or 5’ to 3’) it is identical/, same., DNA showing palandromic sequence, G AAT T C, , 3’, , 5’, , 3’, , 5’, CTTAAG, , Eco RI recognitio, sequence, , Restriction enzyme, EcoRI, 5’, , 3’, , Smith, Nathan and Arber achieved, the discovery of restriction enzymes. For this, spectacular achievement, they were awarded, Nobel Prize for physiology and medicine in, 1978. Since restriction enzymes have been, used for genetic manipulation by dissecting,, analyzing and re-configuration the genetic, information at molecular level., , 5’, , AATTC, , 5’, , G, , 3’, , Do you know ?, 3’, , 5’, , 3’, , G, CTTAA, , Fig. 12.3 : Mode of action of EcoRl to cleave, DNA, , Do you know ?, There are three types of restriction, enzyme viz,, Type I - Which fuction simultaniously as, endonuclease and methylase e.g. E co K., Type II - Which have separate activities for, cleaving and methylation; they are more, stable and are used in rDNA technology e.g., E co RI, BgII; these enzymes cut DNA at, specific sites within the pallindrome., Type III - Which cut DNA at specific nonpallindromic sequences e.g. HpaI, MboII., There are thousands of type II R. E. enzymes, are recognized/ discovered., , A sequence with this type of symmetry, is called a palindrome. When the enzyme, EcoRI attacks this palindrome, it breaks each, strand at the same site in the sequence, which, is indicated by the arrow between the A and G, residues., 3’ ---- C T T, AA G, 5’ ---- G A A T T C, , 5’, 3’, , Restriction enzymes either cut straight, across the DNA in the region of palindrome to, give blunt ends or cuts producing short, single, stranded projections at each end of DNA to, produce, cohesive or sticky ends or staggered, ends., B. Cloning vectors (vehicle DNA) - Vectors, are DNA molecules that carry a foreign, DNA segment and replicate inside the, , A good vector should have the ability of, independent replication so that as the vector, replicates (through ori gene) and large number, of copies of the DNA insert will be formed., Moreover vector should be able to easily, introduce into host cells., , 276
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A vector should have marker genes for, antibiotic resistance; must contain unique, cleavage site in one of the marker genes for, restriction enzyme; it should have at least, suitable control elements like promoter,, operator, ribosomal binding sites, etc. The, plasmids obtained naturally do not posses all, the characteristics. Hence, they are constructed, by inserting gene for antibiotic resistance., e.g. pBR 322, pBR 320, pACYC 177 are the, constructed plasmids. pBR 322 is mostly used, in rDNA technology in plants., i. Plasmid : The plasmids most commonly, used in recombinant DNA technology are, those that replicate in E. coli. Investigators, have engineered these plasmids to optimize, their use as vectors in DNA cloning., Polylinker, HindIII, Sphl, Pstl, Sall, Xbal, BamHl, Smal, Kpnl, Sacl, EcoRl, , ori, , Region into which, foreign DNA can, be inserted, , transposon, with the new DNA, can still be, inserted into the host cell’s chromosomes., A plant cell containing this DNA, can then, be grown in culture or induced to form a, new, transgenic plant., C. Competent host (cloning organism) used, are usually the bacteria like Bacillus, haemophilus, Helicobacter pyroli and E., coli., Mostly E. coli is used for the transformation, with recombinant DNA, 12.3 Methodology for rDNA technology :, The steps involved in gene cloning are as, follows :, a. Isolation of DNA (gene) from the donor, organism :, i. The desire gene to be cloned has to be, obtained from the source organism (donor)., Initially the cells of the donor organism are, sheared with the blender and treated with, suitable detergent. Genetic material from, the donor is removed isolated and purified, by using several techniques. Isolated DNA, can be spooled on to a glass rod., ii. Isolated purified DNA is then cleaved, , ampr, , Fig. 12.4 : Plasmid cloning vector showing, a replication origin (ori), a drug resistance, gene (ampr ) and a region in which foreign, DNA can be inserted., ii. Plasmid vectors for plants : An important, vector for carrying new DNA into many, types of plants is a plasmid that is found in, Agrobacterium tumefaciens. This bacterium, lives in the soil and causes a plant disease, called crown gall, which is characterized, by the presence of over- growths, or tumors,, in the plant. A. tumefaciens contains a, plasmid called Ti (for tumor-inducing). The, Ti plasmid contains a transposon, called T, DNA, which inserts copies of itself into the, chromosomes of infected plant cells. The, , by using restriction enzymes particularly, Restriction Endonucleases (RE). These, enzymes cleave DNA at specific sites,, called restriction sites and break the DNA, into fragments. There are several types of, restriction endonucleases. Cleaved DNA, fragments have cohesive, sticky, staggered, ends or blunt ends., From cleaved DNA fragments, a fragment, containing desired gene is isolated and selected, for cloning. This is now called foreign DNA, or passanger DNA. A desired gene can also, be obtained directly from genomic library or, cDNA library., , 277
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Donor cell, , Vector, (a plasmid or bacteriophage), , Do you know ?, A, , Gene library is a collection of different, DNA sequences from an organism where, each sequence has been cloned into a vector, for ease fo purification, storage and analysis., There are two types of gene libraries on the, basis of the source of DNA used., • Genomic library : It is a collection of, clones that represent the complete genome, of an organism. The genomic library of, prokaryotes can be constructed by using, plasmid vector. It is because prokaryotic, genome does not contain repeatitive, DNA., • cDNA library : It represents the library, of eukaryotic organisms only. DNA is, produced from isolated mRNA by reverse, transcription. The DNA so made is called, complementary DNA (cDNA). The, library is called cDNA library. Eukaryotic, DNA genome contains introns, regulatary, genes and repeatitive DNA. Hence, the, establishment of genomic library in, eukaryotes is not meaningful, , Vector, , Isolation of, desired DNA, Target, DNA, , Enzymatic, fragmentation, by restriction, enzyme, , B, C, , Joining of target DNA and, cloning vector by DNA ligase, , Target, DNA, , rDNA, D, , Host bacteria, , Vector DNA, , E, , Introduction into a bacterial, host cell (Transformation, viral infection), Transformed host, cell containing rDNA, molecule, , F, , G, , Identification and, selection Amplification, Cell multiplication, Protein production from, cloned gene, Protein encoded by, insert DNA, , Protein harvesting, , Fig. 12.5 : Outline of the process of, recombinant DNA technology, , b. Insertion of desired foreign gene into a, cloning vector (vehicle DNA) :, The foreign DNA or passanger DNA is now, inserted into a cloning vector or vehicle DNA., The most commonly used cloning vectors are, plasmids of bacteria and the bacteriophage, viruses like lamda phage and M13. The most, commonly used plasmid is pBR 322., Plasmids are isolated from the vector, organims i.e. bacterium. By using same RE, (which is used in the isolation of the desired, gene from the donor), plasmid i.e. vector DNA, is cleaved., Now by using enzyme DNA ligase, foreign, DNA is inserted/ integrated into the vector, DNA. The combination of vector DNA and, foreign DNA is now called Recombinant, DNA or Chimeric DNA and the technology is, reffered to as rDNA technology., , c. Transfer of rDNA into suitable competent, host or cloning organism :, Finally the recombinant DNA is now, introduced i.e. transferred for expression into, a competent host cell of the suitable cloning, organism which is usually a bacterium., Host cell takes up naked rDNA by process, of ‘transformation’ and incorporates into, its own chromosomal DNA which finally, expresses the trait controlled by passenger, DNA. The transfer of rDNA into a bacterial, cell is assisted by divalent Ca++. The cloning, organisms used in plant biotechnology are, E.coli and Agrobacterium tumifaciens. The, host/ competent cell which has taken up rDNA, is now called transformed cell., Foreign DNA can also be transferred, directly into the naked cell or protoplast of the, competent host cell, without using vector. This, , 278
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is done by using techniques like electroporation,, microinjection,, lipofection,, shot, gun,, ultrasonification, biolistic method, etc. But, in plant biotechnology the transformation is, through Ti plasmids of A. tumifaciens., d. Selection of the transformed host cell :, The transformation process generates a, mixed population of transformed (recombinant), and non-transformed (non-recombinant) host, cells. For isolation of recombinant cell from, non-recombinant cell, marker gene of plasmid, vector is employed. For example, PBR322, plasmid vector contains different marker gene, (Ampicillin resistant gene and Tetracycline, resistant gene). When pst1 RE is used, it knocks, out Ampicillin resistant gene from the plasmid,, so that the recombinant cell become sensitive, to Ampicillin., e. Multiplication of transformed host cell:, Once transformed, host cells are separated, by the screening process. In this step the, transformed host cells are introduced into fresh, culture media., At this stage the host cells divide and, redivide along with the replication of the, recombinant DNA carried by them., , Animal biotechnology, (Tissue culture, generative, meicine, immunotechnology, GM, animals, pharmacogenomics,, gene therapy), , Environmental biotechnology, (Pollution control, biofuels,, bioremediation, biodiversity), , f. Expression of the gene to obtain the desired, product:, The next step involves the production, of desired products like alcohol, enzymes,, antibiotics, etc. Finally the desired product is, separated and purified through downstream, processing using suitable bioreactor., Do you know ?, The Centre for Cellular and Molecular, Biology (CCMB) located in Hyderabad, is, a premier research organization in frontier, areas of modern biology including DNA, fingerprinting and Molecular approaches in, animal breeding. The objectives of the Centre, are to conduct high quality basic research and, training in frontier areas of modern biology,, and promote centralized national facilities, for new and modern techniques in the interdisciplinary areas of biology., 12.4 Applications of Biotechnology:, Biotechnology is an umbrella term covering, a broad spectrum of scientific applications used, in many sectors, such as health and agriculture., Industry, environment and genomics., , Plant biotechnology, (plant cell and tissue culture,, GM crops, marker-assisted, selection), , Industrial biotechnology, (Enzyme biotechnology,, protein engineering, metabolic, engineering, metabolomics), , Biotechnology, , Microbial biotechnology, (Microbial genomics,, biofertilizers, biopesticides,, IPM), , Fig. 12.6 : Applications of Biotechnology, 279, , Genomics, Whole genome sequencing,, gene function, reverse, genetics, bioinformatics)
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Tabel 12.7 : Human proteins produced by, rDNA technology to treat human diseases, Disorder/ Diseases/, Health condition, 1. Anaemia, 2. Asthma, 3. Atherosclerosis, 4. Parturition, 5. Blood clots, , 6. Cancer, , 7. Diabetes, 8. Emphysemo, 9. Haemophilia A, 10. Haemophilia B, 11. Hepatitis B, , synthesized DNA sequence of insulin for two, chains A and B and separately inserted into two, PBR322 plasmid vector. Insulin production by, recombinant DNA technology is designed by, Gilbert and Villokomaroff in 1978., , Recombinant, protein(s), Erythropoeitin, Interleukin-1 receptor, Platelet derived, growth factor, Relaxin, Tissue plasminogen, Activator (TPA), Urokinase, Interferons, tumour, necrosis factor, interleukins,, macrophage, activating factor, Insulin, 1- Antitrypsin, , The genes are inserted by the side of βgalactosidase gene of the plasmid. The, recombinant plasmids were then separately, transformed into E. coli host. The, host, produced penicillinase + pre-pro insulin., Insulin is later separated by trypsin treatment., , Factor VIII, Factor IX, Hepatitis B vaccine, , a. Healthcare Biotechnology :, It refers to a medicinal or diagnostic, product or a vaccine. This technology has, a tremendous impact on meeting the needs, of patients. Biotechnology offers patients, a variety of new solutions such as: unique,, targeted and personalized therapeutic and, diagnostic solutions for organ transplant, stem, cell technology, genetic counselling, forensic, medicine, gene probes, genetic fingerprinting, and karyotyping are outcomes of biotechnology., , Vaccine production:, A vaccine is a biological preparation that, provides active acquired immunity against a, certain disease. Usually a vaccine consists of, a biological agent that represents the diseasecausing microorganism. It is often made from a, weakened or killed form of the microorganism,, its toxins or one of its surface protein antigens., Biotechnology has offered modern, diagnostictestkits-rickettsial,bacterialandviral, vaccines along with radiolabelled biological, therapeutics for imaging and analysis., Vaccines have eliminated small pox,, polio and other deadly diseases for the last, several decades. Biotechnology has made, advancements in vaccination by making, recombinant vaccines that have the potential, to eradicate non-communicable diseases like, cancer. Naked DNA vaccines, viral vector, vaccines and plant-derived vaccines are found, to be most effective against a number of, bacterial and viral disorders., , Human insulin :, Insulin is a peptide hormone produced by, β-cells of islets of Langerhans of pancreas. It, was discovered by sir Edward Sharpey Schafer, (1916) while studying Islets of Langerhans., , Collect the information pertaining to, recombinant vaccines and their types protein vaccines and DNA vaccines., , Insulin is essential for the control of blood, sugar levels. Diabetes mellitus is a disease, in which some people cannot make insulin, themselves. Hakura et al (1977), chemically, , Oral vaccines: a novel approach :, The latest hot spot in the field of vaccine, research is the development of vaccine which, can be taken orally. Immunogenic protein of, , Internet my friend, , 280
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certain pathogens is found to be active when, administered orally. The gene corresponding to, such proteins is isolated and a gene construct is, produced. This is introduced and expressed in, a plant genome, which results in production of, such immunogenic proteins in the parts of the, plant where it is expressed. These when fed into, animals or mainly humans, the person becomes, vaccinated against certain pathogen. Such, vaccines are also known as edible vaccines., An exciting invention is production of ‘melt, in the mouth’ vaccines that can be administered, by placing them under your tongue that, delivers it into the blood stream. The most, important example is the production of flu, vaccine by Bacillus which melts in the mouth., The tremendous benefit of such vaccines, is the, comfort of administeration, low cost and ease, of storage., b. Agriculture :, Application of Biotechnology in Agriculture, involves scientific techniques such as Genetically, Modified Organisms, Bt Cotton, Pest Resistant, Plants. It helps in modifying plants, animals,, and microorganisms and improve their, agricultural productivity., Tissue Culture is used in Micropropagation, i.e. large-scale propagation of plants in very, short durations. Tissue culture technique is also, the best method for storing germplasm and, maintaining a specific genetic type (Clone)., This technique is used in those plants, which, produce recalcitrant seeds or produce highly, variable seeds., Recalcitrant means the reduction in, the seed moisture contents below certain, levels and freezing drastically reduces the, servival and thus present difficulty in storage., Here, subcellular damage of seeds occur, accompanied by consequent loss of viability,, when dried., , c. Gene therapy:, A gene is a stretch of DNA required to, make a functional product such as part or all of, a protein. During gene therapy, DNA that codes, for specific genes is delivered to individual, cells in the body., Gene therapy is the treatment of disease, by replacing, altering or supplementing a gene, that is absent or abnormal and whose absence, or abnormality is responsible for the disease., Most, if not all, diseases have a genetic, factor. The genetic factor can be wholly or, partially responsible for the disease. For, example, in disorders such as cystic fibrosis,, haemophilia, and muscular dystrophy, changes, in a gene directly result in the condition., In other conditions, such as high, cholesterol and high blood pressure, genetic, and environmental factors interact to cause, disease. There are more than 5000 different, human genetic diseases known to be caused, by single gene defects e.g. sickle cell anaemia,, thalassemia, Tay-sach’s, disease, cystic, fibrosis, Huntington’s chorea, haemophilia,, alkaptonuria, albinism, etc., Gene therapy is being used in many ways., For example, to:, • Replace missing or defective genes;, • Deliver genes that speed the destruction of, cancer cells;, • Supply genes that cause cancer cells to, revert back to normal cells;, • Deliver bacterial or viral genes as a form, of vaccination;, • Deliver DNA to antigen expression and, generation of immune response;, • Supply of gene for impairing viral, replication;, • Provide genes that promote or impede the, growth of new tissue; and, • Deliver genes that stimulate the healing of, damaged tissue., , 281
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disease,, familial, hypercholesterolemia,, haemophilia, phenylketonuria, cystic fibrosis,, sickle cell anaemia, Duchenne muscular, dystrophy, emphysema, thalassemia etc., , Do you know ?, Delivery of genes into cells :, Genes can be delivered by three ways :, i. Ex vivo delivery where cells are removed, from the patients and then gene is, introduced using viral or non-viral vectors, e.g. Parkinsons disease, a neurological, disorder., ii. In vivo delivery where therapeutic genes, are directly delivered in the cells at the, target sites of the diseased tissue in the, patient- like intravenous infusion genes, to treat cancer are injected directly into, tumor., iii. Use of virosomes (Liposome + inactivated, HIV), bionic chips are the other methods, of gene delivery., Forms of gene therapy :, a. Germ line gene therapy : In this method, healthy genes can be introduced into germ, cells like sperms, eggs, early embryos. It, allows transmission of the modified genetic, information to the next generation. Though it, is highly effective in counteracting the genetic, disorders, it is not encouraged for application, in human beings due to a variety of technical, and ethical reasons., b. Somatic cell gene therapy : In this type the, gene is introduced only in somatic cells like, bone marrow cells, hepatic cells, fibroblasts, endothelium and pulmonary epithelial cells,, central nervous system, endocrine cells and, smooth muscle cells of blood vessel walls., Modification of somatic cells only affects, the person being treated and the modified, chromosomes cannot be passed on the future, generations. Somatic cell gene therapy is the, only feasible option and the clinical trials have, already employed for the treatment of acquired, disorders such as cancer and rheumatoid arthritis, and blood disorders including SCID, Gaucher’s, , d. Genetically Modified Organisms (GMOs):, These are living organisms whose genetic, material has been artificially manipulated in a, laboratory through genetic engineering. This, creates combinations of plant, animal, bacteria,, and virus genes that do not occur in nature or, through traditional crossbreeding methods., Most GMOs have been engineered to, withstand the direct application of herbicide, and/or to produce an insecticide. However,, new technologies are now being used to, artificially develop other traits in plants, such, as a resistance to browning in apples, and to, create new organisms using synthetic biology., Despite biotech industry promises, there is, no evidence that any of the GMOs currently, on the market, offer increased yield, drought, tolerance, enhanced nutrition, or any other, consumer benefit., I. Transgenic Plants :, The human race is very dependent on, agriculture and as world populations continue to, expand, there must be continuous reassessment, of agricultural practices to optimize their, efficiency. Since early times human beings have, sought to improve the quality and productivity, of agriculturally important plants. This was, done by selection and traditional breeding, procedures that were painstakingly slow and, difficult. Traditional breeding programmes, involve sexual crosses, which resulted in the, high quality of present day food plants such, as wheat, rice, corn, potato, etc. More recently,, biotechnological approaches have been applied, to these plants to create genetic variations that, are beneficial for mankind., First transgenic plant produced was, tobacco. More then 60 transgenic dicot plants, and several monocot plant like maize, oat,, , 282
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rice, wheat are known. Tomato, soybean,, potato, sugar beet, grapes, brinjal, cotton are, other transgenic plants. Transgenic plants are, being looked up as bioreactors for molecular, farming i.e. for production of novel drugs like, interferons, edible vaccines, antibodies, amino, acids, immunotherapeutic drugs, etc., Advantages of GM food-plants :, The ways in which one thinks that, genetically modified plants can help, are listed, as follows:, a. Insect pest resistance:, It can help farmers to reduce their use of, chemical pesticides, which in turn can reduce, the cost of producing food. However, an, alternative has been available for more than, 30 years which is a biological insecticide from, the bacterium, Bacillus thuringiensis (Bt)., However, the use of B. thuringiensis sprays is, limited because of low stability of the protein, in the field., Bt cotton is one of the best transgenic, plants known for its insect resistance property., Insect resistant plants contain either a gene, from B. thuringiensis or the cowpea trypsin, inhibitor gene. The gene called cry gene present, in B. thuringiensis produces a protein that forms, crystalline inclusions in bacterial spores. When, ingested by a susceptible insect, a combination, of high pH and the enzyme proteinase of the, insect’s midgut, processes them hydrolytically, to release the core toxic fragments., , The effect of these fragments is seen within, minutes of ingestion, beginning with midgut, paralysis and ending with disruption of midgut, cells of insect. Bt toxin activity has been against, many species of insects within the orders of, Lepidoptera, Diptera, and Coleoptera., Golden rice - a transgenic food crop used, to reduce vitamin A deficiency disease., Similarly, the gene of α-amylase inhibitor, (αAl-Pv) has been isolated from adzuki bean, (Phaseolus vulgaris) and transferred to tobacco, and this gene works against pests like Zabrotes, subfasciatus and Callosobruchus chinensis., b., Improved, nutritional, qualities, (biofortification):, Transgenic plants have also been produced, to provide functional food and neutraceuticals., For millions of people in developing countries,, rice is the main item in their diet. Because, rice does not contain many essential nutrients,, malnutrition is very common in these countries., Especially terrible is the blindness that, results from a lack of vitamin A. This vitamin, is abundant in milk and in vegetables such as, carrots, which most of the poor people of the, world cannot afford. To solve this problem,, Swiss researchers created transgenic rice, (golden rice) and transgenic mustard (golden, mustard) varieties that are high in vitamin A., The golden colour is due to vitamin A. They, hoped that this rice, if grown and eaten in, developing countries, would reduce the diseases, associated with vitamin A deficiency (VAD)., , Table 12.8 : Some transgenic plants produced for functional food and neutraceuticals, Substance, , Potential benefit, , Crop, , Provitamin A, , Anti-oxidant, , Rice, , Phytoene synthase, lycopene cyclase, , Vitamin E, , Anti-oxidant, , Canola, , γ- tocopherol methyl trasnferase, , Flavonoids, , Anti-oxidants, , Tomato, , Chalone isomerase, , Fructants, , Low calories, , Sugarbeet, , 1-sucroese: sucrase fructosyl transferase, , Iron, , Iron fortification, , Rice, , Ferritin, metallothioein, phytase, , 283, , Transgene
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Improvement in oil content and oil quality of, oil crops like soybean, oil palm, rapeseed and, sunflower, have been achieved by transfer of, ‘Arabidopsis genes’., Iron deficiency is also a serious nutritional, problem, affecting an estimated 30% of the, world population. For production of transgenic, crops that will produce food rich in iron, an iron, storage protein (ferritin) is targeted. Ferrritin is, found in many animals, plants and bacteria., The genes for ferritin protein isolated from, soybean and Phaseolus have been transferred, to rice., , d. Plants as factories :, To produce novel biochemicals and, vaccines (Biopharmaceuticals), plants are, potential factories or bioreactors for high, value biochemicals like starch, sugar, lipids,, proteins, and products like fine chemicals,, perfumes and adhesive compounds as well as, industrial lubricants, biodegradable plastic and, even ‘renewable’ energy crops to replace fossil, fuels., , Do you know ?, •, , Genetically, engineered, herbicide, tolerant plants are developed as in maize,, wheat and many other monocot plants., , •, , Genetically engineered disease resistant, plants (against bacterial and viral, pathogenes) are also developed in crop, plants like tomato, potato and tobacco., , •, , Plants deficient in amino acids like, methionine, lysine and tryptophan are, genetically engineered by introducing, genes from other sources so as to make, the seeds protein rich. e.g. Leguminous, plants (pulses), maize, etc., , •, , Most of these physiological changes are, due to endogenous enzyme activity. Genetic, engineering has made it possible to slow down, these activities. In the tomato the enzyme, polygalacturonase breaks down the cell wall, constituent- pectin, leading to softening of, fruit during ripening. Thus, the fruits are easily, bruised and damaged on shipment. By inhibiting, the polygalacturonase by antisense genes, the, tomato (genetically modified tomatoes are, called Flavr savr tomatoes) can remain on the, vine until mature and be transported in a firm, solid state., , Biopharmaceuticals, are, proteins,, hormones, antibodies, vaccines or enzymes, isolated from transgenic plants. Some of the, proteins that are being produced by transgenic, crop plants:, , Similarly, genetically engineered plants, tolerant to abiotic stresses such as high, temperature, water, cold, etc. are also, developed., , c., Modification, in, Post-harvest, characteristics:, Diseases and pests, bruising on soft fruits, and vegetables, heat and cold storage, overripeness, loss of flavours and odours, etc., lead to great deal of losses during storage and, transport of crops., , • Human growth hormone with the gene, inserted into the chloroplast DNA of, tobacco plants., • Humanized antibodies against such, infectious agents as HIV, Respiratory, syncytial virus (RSV), Herpes simplex, virus (HSV), the cause of "cold sores", • Protein antigens to be used in vaccines, for e.g. Patient-specific antilymphoma (a, cancer) vaccines. B-cell lymphomas are, clones of malignant B cells expressing on, their surface a unique antibody molecule., Currently many novel products have been, commercially exploited for their products such, as:, , 284
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a. A ‘superglue’ produced by tobacco plants, with genes encoding for powerful adhesive, proteins, enables marine mussels to stick, to rocks. It will be especially valuable, as a biochemical glue for body repairs, during surgery., b. Transgenic plants, containing oilencoding gene from marine algae,, produce oil that has nutritional value, similar to cod- liver oil., c. Plant that will produce the antimalarial, drug, Artemisinin., d. Genetically engineered opium poppy to, produce more powerful painkillers., e. Transgenic plants producing edible, vaccines:, Genetically altered plants can provide, protection to infectious diseases. Plant products, acting as vaccines would be inexpensive to, produce and thus, can easily be made available, in developing countries. Potatoes, tomatoes,, bananas, soybeans, alfalfa and cereals are, the most common foods proposed for edible, vaccine delivery., II. Transgenic animals:, Many transgenic animals such as mice, rats,, rabits, pig, sheep, cows, fowls, fish have been, produced through rDNA technology. The term, transgenic animal refers to an animal in which, , there has been a deliberate modification of the, genome - the material responsible for inherited, characteristics - in contrast to spontaneous, mutation. Foreign DNA is introduced into the, animal, using recombinant DNA technology,, and then must be transmitted through the germ, line so that every cell, including germ cells, of, the animal contain the same modified genetic, material., A representative, but non-inclusive, list, of purposes for which transgenic animals, have been used, indicates the wide-ranging, application of this biotechnology:, • in medical research, transgenic animals, are used to identify the functions of specific, factors in complex homeostatic systems, through over- or under-expression of a, modified gene (the inserted transgene);, • in toxicology: as responsive test animals, (detection of toxicants);, • in mammalian developmental genetics;, • in molecular biology, the analysis of the, regulation of gene expression makes use, of the evaluation of a specific genetic, change at the level of the whole animal;, • in the pharmaceutical industry, targeted, production of pharmaceutical proteins,, drug production and product efficacy, testing;, , Transgenic fowl, for meat and eggs, , Transgenic fish for, protein rich meat, , Transgenic mouse as, animal model for research, , Transgenic cow as, bioreactor, , Fig. 12.9 : Transgenic animals, 285
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• in biotechnology: as producers of specific, proteins;, • genetically engineered hormones to, increase milk yield, meat production;, genetic engineering of livestock and, in aquaculture affecting modification, of animal physiology and/or anatomy;, cloning procedures to reproduce specific, blood lines; and, • developing animals specially created for, use in xenografting., , The main objectives for improved animal, breeding programmes coupled with this new, technology of gene transfer are given below., • Efficiency of meat production, • Improved quality of meat, • Milk quality and quantity, • Egg production, • Wool quality and quantity, • Disease resistance in animals, • Production of low-cost pharmaceuticals, and biologicals, , a. Transgenic mice and cancer research :, Through laboratory investigations with, transgenic mice that have been modified using, a particular oncogene (cancer causing gene), and thus developed a certain type of cancer,, questions concerning the relationship between, oncogenes and cancer development could be, answered. Theoretically, such animals can also, be used for research into cancer treatment and, prevention of malignancy., In the laboratory of Philip Leder in, Harvard (USA) the transgenic mouse model, for the investigation of the breast cancer was, developed. The oncogenes myc and ras were, analysed to find out if they lead to breast cancer, in mice transformed with these genes., , c. Transgenic cattle for food production :, Of the few research reports describing the, use of transgenic technologies in cattle only, one is directed towards a food production, application. Researchers introduced additional, copies of bovine beta or kappa casein into, dairy cattle and evaluated the effect on milk, production and composition. Transgenic, offspring had an 8 to 20% increase in beta, casein and a two-fold increase in kappa casein., , b. Transgenic farm animals :, With the advent of technology, the intention, of researchers is diverted to produce transgenic, farm animals from which the mankind can, derive greater benefits. Many of the farm, animals are improved for their meat production, ability while some of them are improved for, milk yields and quality, and disease-free status., At the beginning of the century, a dairy cow, provided 2,000 to 3,000 liters of milk a year., , d. Transgenic cattle for human therapeutic, production :, A second application for genetically, modified cattle is the production of human, therapeutic proteins. Human proteins that, have been expressed in milk include human, lactoferrin, human alpha lactalbumin, human, serum albumin and human bile salt stimulated, lipase. The mammary gland in dairy cows is, an excellent protein production factory. On the, other hand, one transgenic cow would be more, than sufficient for production of annual world, supply of factor IX (plasma thromboplastin, component) that is used in the treatment of, haemophilia., , In 1990 Tracy, the transgenic cow was, Today, Holstein cow provides 6,000 liters born in Scotland, and could produce a human, on average and up to 8,000 – 10,000 for the protein in her milk for human therapeutics., best ones. A century ago, a hen laid about 70, Antibodies are currently used for many, eggs a year whereas today the best races lay, different human clinical applications; including, up to 250 eggs per year. This could be possible, treatment of infectious disease, cancer,, because of the advent of biotechnology., 286
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transplanted organ rejection, autoimmune, diseases and for use as antitoxins. To make, a human antibody product, the genetically, modified cows are immunized with a vaccine, containing the disease agent., e. Transgenic Sheep :, Gene transfer technology is applied to, sheep to produce transgenic sheep which, are able to achieve better growth and meat, production as well as to serve as bioreactors., Human growth hormone gene is introduced, in sheep for promoting the growth and meat, production., Bacterial genes, cys E and cys M, are, concerned with biosynthesis of cysteine amino, acids involved in formation of keratin protein, found in wool. Both these genes are identified,, cloned and introduced in sheep to increase wool, production and to improve the quality of wool., f. Transgenic pigs :, The objective of gene transfer in pigs is to, increase growth and meat production and to act, as bioreactors., Pigs are regarded as the most suitable, animals to be bred for heart transplant because, a pig’s heart is about the same size as a human, heart, and pig heart valves have been used in, human heart surgery for over a decade. The pig, clone is the first step towards providing animal, organs and tissues for human transplants, (xenotransplantation)., g. Transgenic fish :, The commercially important fish like, Atlantic salmon, catfish, goldfish, Tilapia,, zebra-fish, common carp, rainbow trout, etc., are transfected with growth hormone, chicken, crystalline protein and E.coli hygromycin, resistance gene. Transgenic fish showed, increased cold tolerance and improved growth, and it is the quantity and quality of fish proteins, as well as its preservation, are the factors, affecting the economic value of fish., , h. Transgenic chicken :, Also carry and express foreign genes. They, could be used to improve the genetic make-up, of existing strains with respect to built-in (in, vivo) resistance to viral and coccidial diseases,, better feed efficiency, lower fat and cholesterol, levels and high protein containing eggs, and, better meat quality., 12.5 Bioethics, bio-piracy and bio-patent :, Bioethics:, Ethics usually deals with the matters, related to socially acceptable moral duty,, conduct and judgement. In otherwords, it helps, to regulate the behaviour of cummunity by, some set of standards. However the concepts, differ according to culture and traditions., Moreover concepts change with the time due, to shifting of perception of values which are, affected by progress in science and technology., Bioethics helps to study moral vision, decision, and policies of human behaviour in relation to, biological phenomena or events. Ethics deals, with ‘Life’ e.g. in vitro fertilization, sperm bank,, gene theropy, cloning, gene manipulations,, euthanasia, death, maintaining those who are, in comatose state, prenatal genetic selection,, etc., The era of biotechnology has brought wide, spectrum on new topics like cloning, transgenic,, gene therapy, eugenics, rDNA technology, etc., The use of all these has drawn a wide range, of reactions in the society. The reactions are, based on individual’s own perception and, moral. Ethical aspects pertaining to the use of, biotechnology seems to be more controversial, and frightening. These concerns are broadly, summarized below :, Use of animals causes great sufferings to, them; voilation of integration of species caused, due to transgenosis; transfer of human genes, into animals and vice versa; indiscriminate use, of biotechnology pose risk to the environment,, health and biodiversity., , 287
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The introduction of Genetically Modified, Organisms (GMOs) has led to a wider debate, on bioethical concerns affecting social,, economic and environmental spheres. These, include the effects on non-target organisms,, insect resistance crops, gene flow and the loss, of diversity as well as the issue on interfering, with nature in which the modification process, itself is disrupting the natural process of, biological entities. Ethics in biotechnology also, includes the general subject of what should and, should not be done in using recombinant DNA, techniques, 12.6 Effects of Biotechnology on the, Environment :, a. Herbicide Use and Resistance :, Effects on the environment are a particular, concern with regard to GMO crops and food, production. One area of development involves, adding the ability to produce pesticides and, resistance to specific herbicides. These traits, are helpful in food production, allowing, farmers to use fewer chemicals, and to grow, crops in less than ideal conditions. However,, herbicide use could be increased, which will, have a larger negative effect on the surrounding, environment. Also unintended hybrid strains of, weeds and other plants can develop resistance, to these herbicides through cross-pollination,, thus negating the potential benefit of the, herbicide. One such herbicide that has already, been added is RoundUp. Crops of RoundUpready soybeans have already been implemented, into agricultural practices, possibly conferring, RoundUp resistance to neighboring plants., b. Effects on Untargeted Species :, Bt corn, which produces its own pesticide,, is also in use today. It has adverse effects on, Monarch butterfly populations, which are not, the original target of the pesticide. It can also, have unintentional effects on neutral or even, beneficial species., , 12.7 Effects of Biotechnology on Human, Health :, a. Allergies :, GMO crops could potentially have negative, effects on human health as well. Consumers, have developed unexpected allergic reactions., e.g. Researchers used a gene from the Brazil, nut to increase the production of Methionine, in soya beans. The insertion of this gene, inadvertently caused allergic reactions to the, soya bean in those with known nut allergies, (“Biotech Soybeans”)., b. Long-Term Effects :, Because GMO technology has been, available for such a short amount of time, there, is relatively little research which has been, conducted on the long-term effects on health, which we cannot anticipate at this point., c. New Proteins :, Proteins that have never been ingested, before by humans are now part of the foods, that people consume every day. Their potential, effects on the human body are as of yet, unknown., d. Food Additives :, GMOs also present us with possibilities, of introducing additional nutrients into foods,, as well as antibiotics and vaccines. This, availability of technology can provide nutrition, and disease resistance to those countries, that don’t have the means to provide these,, otherwise., However, there is possibility of the creation, of antibiotic and vaccine-resistant strains of, diseases., This shows that the vast advances in life, sciences and our multicultural and pluralistic, modern societies create numerous bioethical, problems requiring some stringent regulation., In terms of GMOs, the Indian Government, has set up the Genetic Engineering Approval, Committee (GEAC). This organization makes, decisions regarding the validity of research, involving GMOs and addresses the safety of, GMOs introduced for public use., , 288
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12.8 Biopatent and Biopiracy :, a. Biopatent :, Patent is a special right granted to the, inventor by the goverment. Patent is a personal, property of inventor. It can be sold like any, other property. A patent consists of three, parts - grant (aggrement with the inventor),, specification (subject matter of invention) and, claims (scope of invention to be protected)., Biopatent is a biological patent. Biopatents, are awarded for strains of microorganisms,, cell lines, genetically modified strains, DNA, sequences, biotechnological processes, product, processes, product and product applications., Biopatents are awarded to recognize real, innovative contributions made by the inventor, to the cause of human welfare. The awards, are given to inculcate encouragement and, values in developing scientific culture and in, emphasizing the role of biology in shaping, human society., Indian patent allows ‘process patent’ and, not the ‘product patent’. Biopatent allows the, patent holder to exclude others from making,, using, selling or importing protected invention, for a limited period of time. Duration of, biopatents is five years from the date of the, grant or seven years from the date of filing the, patent application, which ever is less., First biopatent was patented pertaining, to, genetically, engineered, bacterium, ‘Pseudomonas’ used for clearing oils spills., Patent under the title ‘control of plant gene, expression’ was issued jointly to Delta and, Pineland company and U. S. department of, agriculture. Patent is based on a gene that, produces a protein toxic to plant thus, do not, allow seeds to germinate. However, this patent, was not granted by Indian goverment. Such, a patent is considered morally unacceptable, and fundametally unequitable. This is because, financially powerful corporations would aquire, monopoly over biotechnological process. This, in turn would pose a threat to global food, security., , b. Biopiracy :, Pirates in general terms are those who, steal and kill others to enrich themselves., Biopirates are those who do not kill but steal, the patent (misuse the patent). Biopiracy is, defined as ‘theft of various natural products, and then selling them by getting patent without, giving any benefits or compensation back to, the host country’. In short, it is unauthorized, misappropriation of any biological resource, and indigenous knowledge., Most developed,, industrialized, and, financially rich nations are poor in biodiversity, or traditional knowledge whereas developing, and underdeveloped nations have ample of, biodiversity and they traditionally better know, the use of their bio-resources. Traditional, Knowledge naturally includes a deep, understanding of ecological processes and the, ability to sustainably extract useful products, from the local habitat. Most Traditional, Knowledge is handed down through, generations. This helps them to develop modern,, commercial applications that save the makers, time, money and effort., Components of Traditional Knowledge that, are especially relevant to our global survival, include knowledge of:, • Food, crop varieties and agricultural/, farming practice, • Sustainable management of natural, resources and conservation of biological, diversity, • Biologically important medicines, The conservation of species, habitat, and, biodiversity are essential to the continued, survival of indigenous and rural people., By conserving the customs and habitat of, indigenous persons, we concurrently reduce, emissions from deforestation and ecosystem, degradation. Furthermore, the opportunity for, cultural survival is a basic human right. The, traditional knowledge is facing a problem of, bio-piracy., , 289
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The act of Piracy is unauthorized, publication or reproduction of another person’s, work or material. When someone indulges in, piracy, the accused is using someone’s work, illegally or without taking any permission., The innovations and discovery of the, pharmaceutical and agricultural researches, are not new as to qualify as invention as they, are based on centuries of knowledge of the, traditional societies., Examples of Biopiracy :, • Patenting of Neem (Azadirachta indica) :, The people of India in a variety of ways, have used neem, since time immemorial., Indians have shared the knowledge of the, properties of the neem with the entire world., Pirating this knowledge, the USDA and an, American MNC W.R. Grace in the early 90s, sought a patent from the European Patent Office, (EPO) on the “method for controlling on plants, by the aid of hydrophobic extracted neem oil.”, The patenting of the fungicidal properties of, Neem, was an example of biopiracy., • Patenting of Basmati :, Basmati is a long-grained, aromatic variety, of rice indigenous to the Indian subcontinent., In 1997 the US Patent and Trademark, Office (USPTO) granted a patent to a Texas, based American company Rice Tec Inc for, “Basmati rice line and grains” having trade, , name Texmati. The patent application was, based on 20 very broad claims on having, “invented” the said rice. Due to peoples, movement against Rice Tec in March 2001, the, UPSTO has rejected all the claims., • Haldi (Turmeric) Biopiracy :, Two American researchers of Indian, origin of the University of Mississippi Medical, Center, put a claim to the US Patent and, Trademark Office, maintaining that they, had discovered haldi's healing properties., Surprisingly, they were granted a patent in, March 1995 for something you had known for, years and our ayurvedas for centuries., It meant they had exclusive rights over any, such haldi drug and were in a position to make, millions of dollars. The Council of Scientific, and Industrial Research (CSIR) applied to, the US Patent Office for a reexamination and, they realized the mistake and cancelled the, patent. This was after Indian scientists shouted, from rooftops about how we are losing our, traditional knowledge to marauding foreign, companies who have started poaching on our, ancient healing techniques., It is the need of hour to launch genetic, literacy movement in Indian school and colleges, for better understanding of opportunities, and risks related to biotechnology and also, to promote the safe and meaningful use of, technologies of modern life sciences., , Activity :, Collect information on the use of Biotechnology in pollution control., , 290
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Exercise, Q. 1 Choose the correct option, 1. The bacterium which causes a plant, disease called crown gall is ................, b. Helicobacter pylori, c. Agrobacterium tumifaciens, d. Thermophilus aquaticus, e. Bacillus thuringienesis, , 6. Recognition sequence of restriction, enzymes are generally ..............., nucleotide long., a. 2 to 4, b. 4 to 8, c. 8 to 10, d. 14 to 18, , 2. The enzyme nuclease hydrolyses, ............... of polynucleotide chain of, DNA., a. hydrogen bonds, b. phosphodiester bonds, c. glycosidic bonds, d. peptide bonds, , Q. 2 Very short answer type questions., 1. Name the vector which is used in, protuction of human insulin through, recombinent DNA technology., 2. Which cells from Langerhans of, pancreas do produce a peptide hormone, insulin?, 3. Give the role of Ca++ ions in the transfer, of recombinent vector into bacterial host, cell., , 3. In vitro amplification of DNA or RNA, segment is known as ..............., a. chromatography, b. southern blotting, c. polymerase chain reaction, d. gel electrophoresis, , 4. Expand the following acronyms which, are used in the field of protechnology., , 4. Which of the following is the correct, recognition sequence of restriction, enzyme hind III., a. 5’ ---A-A-G-C-T-T 3’, 3’, ---T-T-C-G-A-A 5’, b. 5’ ---G-A-A-T-T-C 3’, 3’, ---C-T-T-A-A-G 5’, c. 5’ ---C-G-A-T-T-C 3’, 3’, ---G-C-T-A-A-G 5’, d. 5’ ---G-G-C-C 3’, 3’, ---C-C-G-G 5’, 5. Recombinant protein .................. is used, to dissolve blood clots present in the, body., a. insulin, b. tissue plasminogen activator, c. relaxin, d. erythropoietin, , i. YAC, , ii. RE, , iii. dNTP, , iv. PCR, , v. GMO, , vi. MAC, , 5. Fill in the blanks and complete the chart., GMO, i. Bt cotton, ii. ..................., , Purpose, ...................., Delay the softening of, tomato during ripening., ii. Golden rice, ...................., iv. Holstein cow, ...................., Q. 3 Short answer type questions., 1. Explain the properties of a good or ideal, cloning vector for rDNA technology., 2. A PCR machine can rise temperature, upto 100 0C but after that it is not able, to lower the temperature below70 0C, automatically. Which step of PCR will, be hampered first in this faulty machine?, Explain why?, , 291, , 3. In the process of rDNA technology, if two, separate restriction enzymes are used to
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cut vector and donor DNA then which, problem will arise in the formation of, rDNA or chimeric DNA? Explain., 4. Match and write the pairs., , Q. 4 Long answer type questions., 1. Define and explain terms., i. Biopiracy, ii. Biopatent, iii. Bioethus, , Rcombinent protein It’s use in or for, , 2. Explain the steps in process of rDNA, technology with suitable diagrams., , i. platelet derived, growth factor, , a. Anemia, , 3. Explain the gene therapy. Give two types, of it., , ii. -antitrypsin, , b. cystic fobrosis, , 4. How are the transgenic mice used in, cancer research?, , iii. Relaxin, , c. Haemophilia A, , 5. Give the steps in PCR or polymerase, chain reaction with suitable diagrams., , iv. Erythropoietin, , d. Diabetes, , 6. What is a vaccine? Give advantages of, oral vaccines or edible vaccines., , v. Factor VIII, , e. Emphysema, , vi. DNA ase, , f. Parturition, , 7. Enlist different types of restriction, enzymes commonly used in rDNA, technology? Write on their role., 8. Enlist and write in breif about the, different biological tools required in, rDNA technology., , g. Atherosclerosis, , Project :, Visit the tissue culture laboratory in your area. Prepare powerpoint presentation on tissue, culture methodology and its applications., , 292
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Organisms and Populations, are adapted to their environments, not only, for their survival but also for propagation, (multiplication)., , Can you recall?, 1. What is an ecosystem?, 2. What are the abiotic and biotic 30, components of an ecosystem?, Natural world around us shows amazing, diversity of forms and complexity of relations., To understand these, we have to study, levels of organization in the living world, viz. macromolecules, cells, tissues, organs,, individual organism, population, communities,, ecosystems and biomes., You have already studied in school, that, ecology is a study of the interactions among, organisms and between the organisms and their, physical (abiotic) environment. Term ecology, was first used by Reiter but E. Haeckel gave, substance to the term (introduced) ecology., Ecological grouping of organisms is, nothing but ecological hierarchy. There are four, sequential levels with increasing complexity, of ecological (biological) organizations viz,, Organism, Populations, Communities and, Biomes. Individual organism is the basic, unit of ecological hierarchy. Organisms of, same kind inhabiting a geographical area, constitute population. Several populations of, different species in a particular area constitute, community that interact with one another, in several ways. Biome constitutes a large, regional terrestrial unit delimited by a specific, climatic zone having major vegetation zone, (plant communities) and the associated fauna., There are six major groups of terrestrial biomes., We shall explore first two levels viz, organism, and populations., 13.1 Organisms and the environment, around:, Ecology at the level of organism is basically, the study of animal or plant physiology which, helps us to understand how the organisms, , Mean annual temperature (0C), , 13, , 25, , Desert, , Grassland, , 22, , Tropical forest, , 15, , Temperate forest, , 10, 5, , Coniferous forest, , 0, -5, , -10, , Arctic and alpine tundra, , -15, 50, , 100, , 150, , 200, , 250, , 300, , 350, , 400, , 450, , Mean annual precipitation/ rainfall (cm), , Fig. 13.1 : Distribution of major Biomes, with respect to annual temperature and, precipitation, You have studied in earlier classes about, the rotation of earth around the Sun and the tilt, of its axis, cause seasons. These seasons with, annual variation in precipitation in the form of, rain and snow, gives rise to formation of major, biomes of the earth like desert, rain forest,, grassland, tundra, etc., Regional and local variations within each, biome lead to the formation of a variety of, habitats. Major biomes of earth are shown, in Fig. 13.1. On the Earth, life exists even in, extreme and harsh habitats like scorching, deserts of Rajasthan, perpetually rain-soaked, forests of North Eastern states and high, mountain tops of Himalayas., Find out, What are the key differences that, make such a great variation in the physical, and chemical conditions of different habitats?, Here, we must remember that it is not only, the physico-chemical (abiotic) components, that make up the habitat of an organism, but, the habitat also includes biotic components like, , 293
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Table 13.2 : The differences between, Habitat and Niche can be summarized as :, , plants, pathogens, parasites, and predators of, the organism. We assume that over a period, of time, the organism had through natural, selection, evolved adaptations to optimize its, survival and reproduction in its habitat., Do you know ?, Ethology - The term was coined by Hilaire, (1854) but was popularised by W. M. Wheeler, (1902). The term denotes (speaks for) the, study of behaviour of animals in relation to, their environment., , Habitat, , Niche, , A habitat is an area,, where a species lives, and interact, with, the other factors and, prosper., , A niche is a concept,, of how an organism, lives or survives in, the, environmental, conditions., , Habitat consists of Niches do not contain, numerous niches., such components., Effect of temperature, Flow of energy from, rainfall and other one organism to other, abiotic factors., through ecosystem., , Ecology - The term was introduced by E., Haeckel (1865) for the relationship of animals, and plants with their surroundings., , Habitat, supports Niche supports a, numerous species at single species at a, a time., time., , Bionomics - Lankester (1890) coined this term, for the study of relation between organisms to, their environment., , Niche is an activity, Habitat is a physical, performed, by, place., organisms., Habitat is not species Niche, is, specific., specific., , Environmental biology (modern ecology), - The term was introduced in 20th century, (G. L. Clarke 1964, Odum 1969) giving, emphasis on the functional or physiological, interrelationships between the organism and, their surroundings., Biosphere - All the ecosystems on earth, constitute biosphere., Habitat and Niche :, Habitat is a place or the set of environmental, conditions around the organism to which it must, adapt to survive and prosper. The term Niche is, used to denote the functional role played by an, organism in its environment (J. Grinnell 1917)., Niche includes various aspects of the life of an, organism like diet, shelter, etc., A habitat defines the physical space of, an organism with the other living or nonliving factors, while niche describes how, that organism is linked with its physical and, biological environment. In colloquial language, habitat is a postal address while niche is the, profession of organism., , species, , Definition of Habitat :, Place or area where a particular species, lives, is its habitat. Factors like the sunlight,, average rainfall, annual temperatures, type, of soil present and other abiotic (topographic), factors, affect the presence of organisms. These, factors help in determining the presence of the, particular type of species in the environment., Pond, river, ocean, etc. are the examples, of habitat as many organisms are found in, the same place or habitat. These habitats can, be arboreal, terrestrial, aerial, aquatic, etc., The immediate surrounding of an organism,, sometimes also referred to as microhabitat,, is an important concept to remember when, working with sedentary or weakly motile, organisms., Definition of Niche :, The term niche was first time used by ‘J., Grinnell’. The term ecological niche is still, not well understood and is sometimes even, misused., , 294
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Niche is described as a position of a species, in the environment like, what they do for their, survival? how they fulfill their needs of shelter,, food? etc. Niche deals with the flow of energy, from one organism to another and hence, it is, important to understand, what an organism, eats, how it interacts with other organisms,, etc. As soon as the niche is left vacant, other, organisms fill that position. The niche is, specific to each species, which means no two, species can share the same niche., If the species creates its own unique, niche in an ecosystem, it would be helpful in, reducing competition for resources among, species. By taking an example of a bird, it, can be understood that how these birds differ, in their eating habits, where some birds eat, only insects, some only fruits and some can eat, both and anything they come across. So here, we can conclude that these birds living in the, same habitat differ in their niches because of, different eating habits., Three types of niches are found:, a. Spatial or habitat niche : It deals with the, physical space occupied by the organisms., , We have seen earlier in the chapter that, each habitat type is regulated by a number of, abiotic or physico- chemical factors., Key abiotic factors that influence any, habitat are ambient temperature, availability, of water, light and type of soil., 13.2 Major Abiotic Factors :, Temperature:, It is the most ecologically relevant, environmental factor. Average temperature, on land varies from subzero levels in polar, areas and high altitudes, upwards upto 50oC in, tropical deserts in summer. Temperature also, varies seasonally. It decreases progressively, from the equator towards the poles and from, plains to the mountain tops. There are some, unique habitats such as hot springs (80 to, 1000C) and deep-sea hydrothermal vents where, average temperatures usually 400o C. Ambient, temperature affects the enzyme kinetics of the, cell and thus, the entire metabolism, activity, and other physiology of the organism., Only few organisms can tolerate and thrive, in a wide range of temperatures (eurythermal),, but, a vast majority of them are restricted to a, narrow range of temperatures (stenothermal)., , b. Trophic niche : It is on the basis of trophic, level of an organism in a food chain., c. Multidimensional or hypervolume niche:, It considers number of environmental factors, (both biotic and abiotic), the resulting space, will be a hypervolume; not something that can, be perceived by the human mind. This space is, called the hypervolume niche. Alternatively,, it is the position of an organism in the, environmental gradient., For every species, there is a fundamental, niche and a realized niche. Fundamental niche, is the niche in the absence of all competitors,, this is highly improbable in nature. Hence,, realized niche is more realistic approach, in, the presence of competition for the resources, available in the habitat., , Find out, 1. Give names of eurythermal and, stenothermal animals and plants?, 2. What will be the effect of increasing, global temperatures on the different, habitats and the organisms found in those, habitats?, Water: Availability of water is an important, factor affecting the organisms. As we know,, life on earth originated in water, its availability, is so limited in deserts that only special, adaptations are required to survive there. The, productivity and distribution of plants are also, heavily dependent on water., , 295
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Organisms living in water bodies such as, oceans, lakes and rivers, have their own waterrelated problems. For aquatic organisms the, chemical composition and pH of water are, important., The dissolved salt concentration (measured, as salinity in parts per thousand), is less than, 5ppt in fresh waters of streams , lakes and, rivers, and 30-35ppt in the seas and oceans., It may go up to 100ppt in some hypersaline, lagoons., Some organisms are tolerant for a wide, range of salinities (euryhaline) but others are, restricted to a narrow range (stenohaline)., Many fresh water animals cannot live for long, in sea water and vice versa because of the, osmotic problems, they would face., Find out, Give examples of an animal and plant, that can survive in fresh water as well as sea, water?, Light: Plants use light for photosynthesis,, which is only source of energy for the entire, ecosystem. Photosynthesis can occur only in, presence of sunlight. Many species of small, plants (herbs and shrubs) growing on forest, floor are adapted to perform photosynthesis, optimally under very low light conditions, because they are constantly overshadowed by, tall trees., For animals too, diurnal and seasonal, variations in light intensity and duration, (photoperiod) are clues for timing their foraging,, reproductive and migratory activities. The, availability of light on land is closely linked, with that of temperature, since the sun is the, source for both., Find out, What is the source of energy for the, life in deep ocean trenches where sunlight, does not reach?, , Soil: The nature and properties of soil are, dependent on the climate, the weathering, process., Various characteristics of the soil such, as soil composition, grain size, determine, the percolation and water holding capacity, of the soil. These characteristics along with, pH, mineral composition and topography,, determine the vegetation of an area. Vegetation, in turn dictates the type of animals., The abiotic factors that determine the type, of habitat, also show considerable diurnal and, seasonal variations. The plants and animals, must adapt to these changes in order to survive, and flourish in the habitat. During the course, of their evolution, many species have evolved, a relatively constant ‘internal’ environment, that permits all biochemical reactions and, physiological functions to proceed with, optimum rate, and allow the species to flourish., The organisms try to maintain the constancy of, its internal environment (homeostasis) despite, variations in the external environmental, conditions. To survive and flourish in any, environment, organisms must adapt to the, changes in the environment for which there are, following possibilities :, i., , Regulate: Some organisms are able to, maintain homeostasis by physiological, and behavioural changes which ensure, constant body temperature, constant, osmotic concentration, etc. All birds and, mammals are capable of such regulation, (thermoregulation and osmoregulation)., , ii. Conform: Most of animals and plants, cannot maintain a constant internal, environment. Their body temperature, changes with the ambient temperature. In, aquatic animals, the osmotic concentration, of the body fluids changes with that of the, ambient water osmotic concentration. These, animals and plants are simply conformers., , 296
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Some species have evolved the ability, to regulate, within a limited range of, environmental conditions, beyond which, they simply conform. If the stressful, environment is localized or only for a short, period of time, the organism may migrate, or suspend its activities., iii., , Migrate: The organism can move away, temporarily from the stressful habitat to, a more hospitable area and return when, stressful period is over. Many animals,, particularly birds, during winter undertake, long-distance migrations to more hospitable, areas., , iv. Suspend: In plants, seeds serve as means to, tide over periods of stress; they germinate to, form new plants under favourable moisture, and temperature conditions. They do so by, reducing their metabolic activity and going, into a state of ‘dormancy’. In animals, the, organism, if unable to migrate may go into, hibernation during winter e.g. polar bear., Some snails and fish go into aestivation to, avoid summer heat., , organism (morphological, physiological, and, behavioural) that enables the organism to, survive and reproduce in its habitat., Many desert plants have a thick cuticle, on their leaf surfaces and have their stomata, in deep pits to minimize loss of water through, transpiration. They also have a special, photosynthetic pathway (CAM - Crassulacean, acid metabolism) that enables their stomata, to remain closed during daytime. Some desert, plants like Opuntia, have their leaves reduced, (modified) to spines and the photosynthetic, function is taken over by the flattened stems., Mammals from colder climates generally, have shorter snout, ears, tail and limbs to, minimize the loss of body heat (Allen’s Rule.), In the polar seas, aquatic mammals like seals, have a thick layer of fat (blubber) below their, skin acting as an insulator to reduce loss of, body heat., Can you tell?, 1. What is homeostasis?, 2. Why do animals need to maintain, homeostasis?, 3. What are the adaptations in animals, living under crushing pressure at great, depths of ocean?, , Internet my friend, Find out the difference between, hibernation and aestivation., Do you know?, 1. Adaptation of plants for aquatic and, desert habitats., 2. Adaptations of animals for aquatic and, desert habitats., 13.3 Adaptation :, To cope up with extreme variations in, their environment, some organisms respond, through physiological adjustments, while, others do so behaviourally (like migration)., These are their adaptations. Therefore, we, can say that adaptation is an attribute of the, , Some organisms show behavioural, responses to cope with variations in their, environment. Desert lizards manage to keep, their body temperature fairly constant by, behavioural adaptations. They bask in the sun, and absorb heat, when their body temperature, drops below the comfort zone, but move into, shade, when the ambient temperature starts, increasing. Some species burrow into the sand, to hide and escape from the heat., 13.4 Population :, In nature, we rarely find isolated, single, individuals. They live in groups in a welldefined geographical area, share or compete, , 297
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for similar resources, potentially interbreed, and thus form a population., Although, it is an individual organism that, has to cope with changes in the environment, it, is at the population level that natural selection, operates to evolve the desired traits. Population, ecology is, therefore, an important area of, ecology because it links ecology to population, dynamics, genetics and evolution., A population has certain attributes of, its own, which are different from those of an, individual. Basic physical characteristics, of population are - its size and density. Size, speaks for the number of individuals in a, population while density tells us number of, individuals present per unit space, in a given, time. Besides size and density, the other, characteristics include natality, mortality,, immigration, emigration, age pyramids,, expanding population, population growth, forms and biotic potential. An individual has, birth and death, but a population has birth rate, and death rate., Natality is the birth rate of a population., It has the greatest influence on a population’s, growth. Natality is a crude birth rate or specific, birth rate. Crude birth rate is used when, calculating population size (number of births, per 1000 population/year), whereas specific, birth rate is used relative to a specific criterion, such as age. E.g. If in a pond, there were 200, carp fish last year and through reproduction, 800 new fish are added, taking the current, population to 1000, we calculate the birth rate, as 800/200 = 4 offspring per carp per year., •, , •, , It must be remembered, that absolute, natality will be always more than realized, natality., Mortality is the death rate of a population., Mortality rate or death rate, is a measure of, the number of deaths (in general, or due to, a specific cause) in a particular population,, in proportion to the size of that population,, per unit of time. Mortality rate is typically, expressed in deaths per 1,000 individuals per, year. Thus, a mortality rate of 9.5 (out of 1,000), in a population of 1,000 would mean 9.5 deaths, per year in that entire population, or 0.95% out, of the total., •, , Absolute Mortality : the number of deaths, under ideal conditions (with no competition,, abundance of resources such as food and, water, etc.)., • Realized Mortality : the number of deaths, when environmental pressures come into, play., It must be remembered that absolute, mortality will be always less than realized, mortality., Sex ratio: The sex ratio of the population, affects and is reciprocally affected by birth,, death, immigration, and emigration rates., It is measured as the ratio of the number, of individuals of one sex to that of the other, sex. The males and females in a ratio of 1:1, is generally the most common evolutionary, stable strategy (ESS)., , Absolute Natality : the number of births, under ideal conditions (with no competition,, abundance of resources such as food and, water, etc.)., Realized Natality : the number of births, when environmental pressures come into, play., 298, , Can you tell?, What can be the causes of deviation, from 1: 1 sex ratio in natural habitat?, Internet my friend, 1. Find out the sex ratio of Indian population, and the state of Maharashtra., 2. What are the reasons behind deviation of, sex ratio among Indian population?
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Age distribution and Age pyramid:, A population is composed of individuals, of different ages. If the age distribution (per, cent individuals of a given age or age group) is, plotted for the population, the resulting structure, is called an age pyramid. For the purpose of, simplicity, the entire population is divided into, three age groups as Pre-Reproductive (age 014 years), Reproductive (age 15-44 years), and Post- reproductive (45-85+ years)., Use your brain power, From the age pyramids given below, (Fig.13.3)- what will be your forecast for, 15 years from now for the populations of 1., Kenya, 2. Australia, 3. Italy and 4. Hungary., The size of the population it can support, tells us a lot about its status in the habitat. The, population size, in natural habitat, could be, as low as less than 10 (Siberian cranes in bird, sanctuary) or go into millions (Chlamydomonas, in a pond)., Population size, more technically called, population density (designated as N), need, not necessarily be measured in numbers only., Although total number is generally the most, appropriate measure of population density, it is, in some cases either meaningless or difficult to, determine., , Male, , Female, , Rapid Growth, e.g. Kenya, Nigeria, Ages 0 -14 years, , Male, , In an area, if there are millions of termites, / ants but only a few animals which feed on, them, stating that the population density of, these predators is low, will be misleading., In such cases, the biomass is a more, meaningful measure of the, population, size. Total number is again not an easily, adoptable measure, if the population is huge, and counting is impossible or very timeconsuming. Sometimes, for certain ecological, investigations, there is no need to know the, absolute population densities; relative densities, serve the purpose equally well. For instance,, the number of birds / insects caught per trap is, good enough measure of their total population, density. We are mostly obliged to estimate, population sizes indirectly, without actually, counting them or seeing them. The tiger census, in our national parks and tiger reserves is often, based on pug marks and fecal pellets., Population Growth :, The size of a population for any species is, a dynamic parameter. It keeps changing with, time, depending on various factors including, food, predation pressure and adverse weather., In fact, these changes in population density, that give us some idea whether it is flourishing, or declining., , Female, , Slow Growth, e.g. United States, Australia, Ages 15-44 years, , Male, , Female, , Zero Growth, e.g. Denmark, Italy, , Male, , Female, , Negative Growth, e.g. Germany, Hungary, , Ages 45 - 85+ years, , Fig. 13.3 : Age pyramids for countries with rapid, slow, zero and negative population, growth rates., 299
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Growth Models: Does the growth of a, population with time show any specific and, predictable pattern? We have been concerned, about unbridled human population growth and, problems created by it in our country and it is, therefore natural for us to be curious if other, animal populations in nature behave the same, way or show some restraint on growth., , Every species is capable of growing, exponentially under unlimited resource, conditions, and reach enormous population, densities in a short time. Darwin showed how, even a slow growing animal like elephant, could reach enormous numbers. (provided food, and space remain unlimited)., But resources like food and space are not, always unlimited. They may be in the beginning;, but as the population density increases, so does, the competition for those resources, resulting, in slowdown in the rate at which the original, population was growing. This results in logistic, or sigmoid growth curve., ii. Logistic growth: competition between, individuals for limited resources will weed out, the ‘weaker’ ones. Only the ‘fittest’ individuals, will survive and reproduce. In nature, a given, habitat has enough resources to support a, maximum possible number, beyond which, no further growth is possible. Let us call this, limit as nature’s carrying capacity (K) for that, species in that habitat., Growth (size or weight of the organism), , Density of population in a habitat during a, given period, fluctuates due to changes in four, basic processes. New births (B) and Immigration, contribute to an increase in population density., Deaths (D) and Emigration lead to decrease, in population density. Immigration (I) is the, number of individuals of the same species that, have come into the habitat from elsewhere, during the time period under consideration., Emigration (E) is the number of individuals of, the population who left the habitat during the, time period., So, if N is the population density at time ‘t’,, then its density at time ‘t +1’ can be calculated, as,, Nt+1 = Nt + [(B + I) – (D + E)], , i. Exponential growth:, Resources like food, space are essential, for any growth of a population. Ideally,, when resources in the habitat are unlimited,, each species has the ability to fully realize, its innate potential to grow in numbers. Then, the population grows in an exponential or, geometric proportion., , Diminishing, growth phase, Stationary phase, , Log or, exponential phase, , Lag phase, , Population size, , Time, , Fig. 13.5 : Logistic growth curve of population, , Time, , Fig. 13.4 : Exponential growth curve of, population, , A population growing in a habitat with, limited resources show initially a lag phase,, followed by phases of acceleration and, deceleration and finally an asymptote, when, the population density reaches the carrying, capacity. A plot of population density (N) in, 300
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relation to time (t) results in a sigmoid curve., This type of population growth is called, Verhulst-Pearl Logistic Growth., Since resources for growth for most animal, populations, are finite and become limiting, sooner or later, the logistic growth model is, considered a more realistic one., Internet my friend, Gather from Census-data the population, figures for India for the last 100 years, plot, them and check which growth pattern is, evident?, , Think about it, 1., 1. What will happen when carrying capacity, of any habitat is exceeded?, 2. What could be the reasons behind, enormous increase in human population?, , It is obvious that in nature, animals,, plants and microbes do not and cannot live in, isolation but interact in myriad ways to form, a biological community. Interactions may be, intraspecific i.e. existing between organisms, of same population, and interspecific -between, members of different species. The interspecific, interactions occur between minimum two, organisms- plants/ animals/ plant and animal., Such interaction may be classified as four types, viz, neutralism, negative (harmful), positive, (benificial), and both positive and negative, interactions. Even in simplest communities,, many interactions exist, not all may be easily, seen. Interspecific interactions arise from the, interaction of populations of two different, species. These interactions could be beneficial,, detrimental or neutral (neither harm nor benefit), to one of the species or both., Table 13.6 : Interspecific Interactions, , Under a particular set of selection, pressures, organisms evolve towards the most, efficient reproductive strategy. Some produce, a large number of small-sized offspring, (Oysters, pelagic fishes) while others produce, a small number of large-sized offspring (birds,, mammals)., Think about it, What can be the reason behind the, different reproductive strategies adopted by, monocot plants like cereals/ pulses and dicot, plants like mango?, 13.5 Population Interactions :, There is no natural habitat, which has, only one species or animals or plants. For any, species, the minimal requirement is another, species as food. Even a plant species, which, has photosynthetic abilities, cannot survive, alone; it needs soil microbes to break down the, organic matter in soil and release the inorganic, nutrients., 301, , Sr., no., , Type of interactions with, subdivisions, , I, , Neutralism - no significant, effect, II Negative interactions, a. Competition - direct, interference type, b. Competition - resource use type, c. Amensalism, III Positive interactions, a. Symbiosis (Mutualism), b. Commensalism, c. Protocooperation, IV Both positive and negative, interactions, a. Parasitism, b. Predation, + = benifited, - = inhibited, O = not affected, , Species, A, O, , B, O, , -, , -, , -, , -, , -, , O, , +, +, +, , +, O, +, , +, +, , -
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The various types of interactions are, classified as per the nature of these interactions, to one or both the species. Both the species are, benefited in mutualism and both are harmed in, competition., In parasitism and predation only one, species benefits (parasite and predator,, respectively) and the interaction is detrimental, to the other species (host and prey, respectively)., The interaction where one species is benefitted, and the other is neither benefitted nor harmed is, called commensalism. In amensalism, on the, other hand one species is harmed whereas the, other is unaffected., Mutualism:, This interaction is obligatory and, interdependent. It benefits both, the, species. Lichens represent an intimate,, mutualistic relationship between a fungus, and photosynthetic algae or cyanobacteria., The most spectacular and evolutionarily, fascinating examples of mutualism are found, in plant-animal relationships. Plants need the, help of animals for pollinating their flowers, and dispersing their seeds. Animals obviously, have to be rewarded in the form of pollen and, nectar for pollinators and juicy and nutritious, fruits for seed dispersers., , But the mutually beneficial system should, also be safeguarded against ‘cheaters’, for, example, animals that try to steal nectar, without aiding in pollination. Plant-animal, interactions often involve co-evolution of the, mutualists, that is, the evolutions of the flower, and its pollinator species are tightly linked with, one another., Competition:, Competition is the type of interaction, where both the species are at a loss. Totally, unrelated species may compete for the same, resource e.g. in shallow creeks on the west, coast of Mumbai, visiting flamingos and, resident fish compete for their common food,, the zooplankton. Secondly, resources need not, always be limiting for competition to occur., In competition, the feeding efficiency of one, species is reduced due to the interference or, inhibitory presence of the other species, even if, resources (food and space) are abundant, e.g., Leopards do not hunt in close proximity of lion, pride. Therefore, competition is best defined as, a process in which the fitness of one species is, significantly lower in the presence of another, species., , Alga, , Fungus, Lichen, , Fig. 13.7 : V. T. S. of Lichen thallus showing, Algal and fungal components, , Fig. 13.8 : Co-evolution of humming birds, and plants, Gause’s ‘Competitive Exclusion Principle’, states that two closely related species, competing for the same resources cannot coexist indefinitely and the competitively inferior, one will be eliminated eventually. This may be, 302
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true if resources are limiting, but not otherwise., In interspecific competition with sufficient, resources, species facing competition will, evolve mechanisms that promote co-existence, rather than exclusion. One such mechanism is, ‘resource partitioning’. If two species compete, for the same resource, they could avoid, competition by choosing different times for, feeding., , Fig. 13.9 : Lion standing over dead, leopard- removing competition, A species whose distribution is restricted, to a small geographical area because of the, presence of a competitively superior species, is, found to expand its range when the competing, species is removed., Parasitism:, Parasitism has evolved in so many, taxonomic groups from plants to higher, vertebrates. Many parasites have evolved to, be host-specific (they can parasitize only a, single species of host) in such a way that both, host and the parasite tend to co-evolve, against, each other. In accordance with their life styles,, endoparasites evolved special adaptations, such as the loss of unnecessary sense organs,, presence of adhesive organs or suckers to cling, on to the host, loss of digestive system and high, reproductive capacity., The life cycles of parasites are often, complex, involving intermediate hosts or, vectors to facilitate transfer to the host. The, malarial parasite Plasmodium vivax needs, a vector (mosquito) to spread to other hosts., , Majority of the parasites harm the host., They may reduce the survival, growth and, reproduction of the host and may lead to death, of the host, thus reducing its population density., They might render the host more vulnerable to, predation by making it physically weak., Use your brain power, 1. Should an ideal parasite be able to thrive, within the host without harming it?, 2. Why didn’t natural selection lead to, the evolution of such totally harmless, parasites?, Parasites that feed on the external surface, of the host organism are called ectoparasites., The most familiar examples of this group are, the lice on humans and ticks on dogs. Many, marine fish are infested with ectoparasitic, copepods. Cuscuta, a parasitic plant that is, commonly found growing on hedge plants, has, lost its chlorophyll and leaves in the course of, evolution. It derives its nutrition from the host, plant which it parasitizes., Brood parasitism in birds is a fascinating, example, in which the parasitic bird lays its, eggs in the nest of its host bird and lets the, host bird incubate them. During the course of, evolution, the eggs of the parasitic bird have, evolved to resemble the host’s egg in size and, colour to reduce the chances of the host bird, detecting the foreign eggs and ejecting them, from the nest. Eggs of the parasitic bird (Asian, koel) hatch before that of its host (Common, Indian crow)., , 303, , Fig. 13.10 : Crow feeding Asian Koel, hatching in its own nest.
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Predation:, When we think of predator and prey, most, probably it is the tiger and the deer that readily, come to our mind, but a sparrow eating any, seed is no less a predator., Although grazers are animals eating plants,, classified as herbivores, they are, not very, different from predators. Predators play many, important roles. They keep prey populations, under control. Without them, prey species, would reach very high population densities and, cause ecosystem instability e.g. in absence of, frogs, locusts increase in density and destroy, large tracts of agricultural lands. Biological, control, methods adopted in agricultural pest, control are based on the ability of the predator to, regulate prey population. Predators also help in, maintaining species diversity in a community,, by reducing the intensity of competition among, competing prey species., When certain exotic species are introduced, accidentally or intentionally into a new, geographical area, they become invasive, and start spreading rapidly due to absence, of natural predator, e. g. zebra mussels in the, intertidal zone of North America., Internet my friend, Name the invasive species of plants and, animals in India., If a predator over exploits its prey, then the, prey might become extinct and following it, the, predator will also become extinct for lack of, food. This is the reason why predators in nature, are ‘prudent’., Prey species have evolved various defenses, to reduce the impact of predation. It is a kind, of ‘evolutionary arms race’. Better camouflage, for concealment, faster speed for escape are for, the prey and the predator has to counter these,, by its own means. Some species of insects and, frogs are cryptically coloured (camouflaged), to avoid being detected easily. The Monarch, , butterfly is highly distasteful to its predator, (bird) because of a special chemical present, in its body. Interestingly, the butterfly acquires, this chemical during its caterpillar stage by, feeding on a poisonous weed., , Fig. 13.11 : Adult Monarch butterfly, displaying warning colour pattern, For plants, herbivores are the predators., Plants therefore have evolved variety of, morphological and chemical defenses against, herbivores. Thorns (Acacia, Cactus) are, the most common morphological means, of defense. Many plants produce and store, chemicals that make the herbivore sick. When, chemicals/ produce are eaten, they inhibit, feeding or digestion of predator and disrupt, reproduction or even kill it. Calotropis growing, in abandoned fields, produces highly poisonous, cardiac glycosides and that is why you never, see any cattle or goats browsing on this plant., A wide variety of chemical substances that, we extract from plants on a commercial scale,, (nicotine, caffeine, quinine, strychnine, opium,, etc.,) are secondary metabolites produced by, them actually as defences against grazers and, browsers., Commensalism:, This is the interaction in which one species, benefits and the other is neither harmed nor, benefited. An orchid growing as an epiphyte on, , 304
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a branch of mango tree, will get benefit while, the mango tree derives no benefit. The cattle, egret and grazing cattle in close association,, is a classic example of commensalism. Cattle, egrets always forage close to cattle, as cattle, move they flush out insects that might be, difficult for the egrets to find and catch., Another example of commensalism is, the interaction between sea anemone that has, stinging tentacles and the clown fish that lives, among them., The fish gets protection from predators, which stay away from the stinging tentacles., The anemone does not appear to derive any, benefit by hosting the clown fish., , Do you know ?, The instrument used to measure the hight, of forest trees is called hypsometer., World Environment day, , - 5th June, , World Population day, , - 11th July, , World Earth day, , - 22nd April, , World Ozone day, , - 16th Saptember, , Fig. 13.12 : Commensalism- Cattle egret with buffalo and Clown fish in the tentacles of Sea, anemone, 305
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Activity :, Prepare chart for various interactions existing in the plant community or animal, community around you and paste the photographs of the same., , 306
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Exercise, Q. 1 Multiple choice questions., Which factor of an ecosystem includes, plants, animals and microorganisms?, a. Biotic factor b. Abiotic factor, c. Direct factor d. Indirect factor, An assembladge of individuals of, different species living in the same habitat, and having functional interactions is, ................, a. Biotic community, b. Ecological niche, c. Population, d. Ecosystem, , 3. Name the type of association:, a. Clown fish and sea anemone, b. Crow feeding the hatchling of Koel, c. Humming birds and host flowering, plants, 4. What is the ecological process behind the, biological control method of managing, with pest insects?, Q. 3 Short answer questions., 1. How is the dormancy of seeds different, from hibernation in animals?, 2. If a marine fish is placed in a fresh water, aquarium, will it be able to survive? Give, reason., , Association between sea anemone and, Hermit crab in gastropod shell is that of, ................, a. Mutualism, b. Commensalism, c. Parasitism, d. Amensalism, , 3. Name important defense mechanisms in, plants against herbivores., 4. An orchid plant is growing on the branch, of mango tree. How do you describe this, interaction between the orchid and the, mango tree?, , Select the statement which explains best, parasitism., a. One species is benefited., b. Both the species are benefited., c. One species is benefited, other is not, affected., d. One species is benefited, other is, harmed., , 5. Distinguish between the following:, a. Hibernation and Aestivation, b. Ectotherms and Endotherms, c. Parasitism and Mutualism, , Growth of bacteria in a newlly, innoculated agar plate shows ................, a. exponential growth, b. logistic growth, c. Verhulst-Pearl logistic growth, d. zero growth, Q. 2 Very short answer questions., 1. Define the following terms :, a. Commensalism, b. Parasitism, c. Camouflage, , 6. Write a short note on, a. Adaptations of desert animals, b. Adaptations of plants to water, scarcity, c. Behavioural adaptations in animals, 7. Define Population and Community., Q. 4 Long answer questions., 1. With the help of suitable diagram describe, the logistic population growth curve., 2. Enlist and explain the important, characteristics of a population., Project :, Study the age pyramid of human population, in your area, , 2. Give one example for each :, a. Mutualism, b. Interspecific competition, 307
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14, , Ecosystems and Energy flow, Can you recall?, , 1. What is environmental biology?, 2. Meaning of the term habitat., 3. Importance of ecology for humans., An ecosystem is a self regulatory and, self sustaining structural and functional unit of, nature (biosphere). It contains both biotic and, abiotic components. Biotic components interact, with each other and also with the surrounding, environment. Tansley (1935) coined the, term ecosystem. Ecosystems vary greatly, in size from a small pond to large oceans or, small farmland to village. Entire biosphere, can be considered as one global ecosystem,, made up of many local ecosystems. Since the, earth ecosystem is too big and too complex, to be studied, it is divided into two basic, categories, viz. terrestrial and aquatic. Forest,, grassland and desert are the types of terrestrial, ecosystems while lakes, wetlands, rivers and, estuaries are the types of aquatic ecosystems., The ecosystems can also be classified as, Natural ecosystems and Artificial ecosystems., Natural ecosystems do not require any human, inputs, in other words they are self-sustainable., Artificial ecosystems e.g. a farm land, a fish, tank or even a large pond used for rearing fish,, require constant input in terms of energy or, materials., In this chapter, we will study and, analyse the structure of the ecosystem, in order, to appreciate the input (productivity), transfer, of energy (food chain/web, nutrient cycling), and the output (degradation and energy loss)., We will also look at the relationships, chains, and webs that are created because of the energy, flows within the system., , 14.1 Ecosystem :, Structure and Function :, We have already studied the various, biotic and abiotic components of the, environment. We know that all these biotic, and abiotic components influence each other., Let us now look at these components with an, integrated approach and see how the flow of, energy takes place in ecosystem. Interaction, of biotic and abiotic components, results in, a physical structure that is characteristic for, each type of ecosystem. Identification and, enumeration of plant and animal species of an, ecosystem gives its species composition., Emergent layer, Canopy, Understorey, Shrub, layer, , Fig. 14.1 : Stratification of plants in forest, Biotic and abiotic components differ as the, locations vary in space and time. The variation, due to space results in spatial pattern. There are, two types of spatial patterns. viz. Stratification, and Zonation., Vertical distribution of different species of, plants and animals occupying different levels,, is known as stratification. For example, trees, occupy top vertical strata or layer of a forest,, shrubs the second and herbs and grasses occupy, the bottom layer. Similar stratification is also, observed in the open seas as epipelagic, mesopelagic, bathy-pelagic and benthic zones., , 308, , Find out, Stratification of animals in amazon, rain forest.
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Horizontal distribution of plants and, animals on land or in water, is called zonation., Zonation is observed in aquatic (wetlands) as, well as terrestrial ecosystems, but it is easily, seen at the junction of the two. Edges of a large, lake or beach show pronounced zonation in the, form of Inter-tidal, Littoral, Sub-littoral zones., Zonation, , High Tide, Low Tide, , Subtidal, Mudflats, Channels, are rich in, are important invertebrate, habitat for fish, life for, at low tide., shorebirds., They allow, Algal mat, good drainage grow here, and flooding, also., in Mudflats., , Low Marsh High Marsh, is good, supports, habitat for, pickleweed, cordgrass, and patches of, insects,, cordgrass. A, herons and, good habitat, egrets and, for Savannah, the clapper, Sparrow and, rail., Clapper Rail, , Fig. 14.2 : Zonation in wetland, •, , Think about it, , Why is zonation more pronounced at, the edges of habitat?, The biotic and abiotic components of an, ecosystem are all linked together to function as, an ‘ecosystem unit’ through various processes, like, Productivity, Decomposition, Nutrient, cycling and Energy flow. In fact, these are, functional aspects of ecosystem., Any ecosystem must perform these, four processes for its sustainance (to be self–, sustaining). The ecosystem understudy may, be as small as a pond or entire biosphere as, a whole. The process of productivity involves, conversion of inorganic chemicals into organic, material with the help of the radiant energy, of the sun by the autotrophs and consumption, of the autotrophs by heterotrophs. The, Decomposition is the break down of dead, organic material and mineralization of the, dead matter. The nutrient cycling is the storage, , and transport of nutrients. (minerals released, in decomposition process are used again by, autotrophs). The energy flow is unidirectional, flow of energy from producers to consumers, and finally dissipation and loss as heat., Example- Think of a small pond ecosystem., It is fairly a self-sustainable unit that explains, the complex interactions which exist in any, aquatic ecosystem. A pond is a shallow water, body in which all the above four aforesaid, basic processes of an ecosystem are observed., The abiotic component is water with all the, dissolved inorganic and organic substances and, also the rich soil deposit at the bottom of the, pond. The solar input, the cycle of temperature,, day-length and other climatic conditions, regulate the rate of function of the entire pond., The producers include the phytoplankton,, algae and other aquatic plants. The consumers, are represented by the zooplankton, aquatic, insects and fish. The decomposers are the fungi,, bacteria located at the bottom of the pond., a. Productivity :, A constant input of solar energy is the basic, requirement for any ecosystem to function, and sustain. Productivity refers to the rate of, generation of biomass in an ecosystem. It is, expressed in units of mass per unit surface (or, volume) per unit time, for instance grams per, square metre per day (g/ m2/ day). The mass, unit may relate to dry matter or to the mass, of carbon generated., It can be divided into gross primary, productivity(GPP)and netprimaryproductivity, (NPP). Gross primary productivity of, an ecosystem is the rate of production of, organic matter during photosynthesis. Plants, themselves use a considerable proportion of, this GPP for their respiration. Hence, gross, primary productivity minus respiratory losses, (R) constitute the net primary productivity, (NPP)., , 309, , GPP – R = NPP
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Net primary productivity is the, available biomass for the consumption, to, heterotrophs (herbivores, carnivores and, decomposers). The annual net primary, productivity of the whole biosphere is, approximately 170 billion tons (dry weight) of, organic matter. Of this, the productivity of the, oceans is only 55 billion tons. Rest of course, is, from land based ecosystems., , By the process of leaching, water soluble, inorganic nutrients go down (percolate) into the, soil horizon and get precipitated as unavailable, salts. Bacterial and fungal enzymes degrade, detritus into simpler inorganic substances. This, process is called as catabolism. It is important, to note that all the above steps in decomposition, operate simultaneously on the detritus., A tree grows in the soil., , Some are eaten by, herbivors. Nutrients and, energy enter food web., , Use your brain power, What could be the reason for the low, productivity of ocean?, Primary productivity (GPP) depends on the, plant species inhabiting a particular area. It also, depends on a variety of environmental factors,, availability of nutrients and photosynthetic, capacity of plants. Therefore, it varies in, different types of ecosystems. Secondary, productivity is defined as the rate of, formation of new organic matter by consumers., Alternatively, it is the rate of assimilation of, food energy at the level of consumers. It is the, amount of energy available to consumer for, transfer to the next trophic level., b. Decomposition :, Decomposers break down complex organic, matter into inorganic substances like carbon, dioxide, water and nutrients, and the process, is called decomposition. Dead remains of, plants and animals, including fecal matter,, constitute detritus, which is the raw material, for decomposition. The important steps in the, process of decomposition are fragmentation,, leaching, catabolism, humification and, mineralization., Detritivores (e.g. earthworm) break down, detritus into smaller fragments or particles., This process is called fragmentation., , Leaves partially, consumed and, begin to lose form, and become litter., , A leaf falls to the, ground., , Some, nutrients, leach into soil, by chemical, action., , Further, decomposition, by decomposers., Soil rich in, Mineralization Organic content, , Fig., , 14.3, , :, , Decomposition, , cycle, , Humification and mineralization occur, during decomposition in the soil. Humification, leads to accumulation of partially decomposed,, a dark coloured, amorphous, colloidal organic, substance called humus that is resistant to, microbial action and undergoes decomposition, at an extremely slow rate. Humus formation, changes soil texture and increases water, holding capacity of soil., Being colloidal in nature humus serves as, a reservoir of nutrients. The humus is further, degraded by some microbes and release of, inorganic nutrients occurs by the process, known as mineralisation., Decomposition as a process requires, oxygen. Temperature and soil moisture are, the most important factors that regulate, decomposition indirectly to help soil microbes., Warm and moist environment favours, decomposition whereas low temperature and, anaerobic conditions inhibit decomposition., , 310
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Can you recall?, 1. What is a food chain?, 2. What are trophic levels in a food chain?, 14.2 Energy Flow :, Sun is the only source of energy for all, ecosystems on the earth except for the deep-sea, ecosystems. Of the total incident solar radiation,, less than 50 % of it is photosynthetically active, radiation (PAR). Plants and photosynthetic, bacteria (autotrophs) fix energy to prepare food, from simple inorganic materials. Plants capture, only 2-10 % of the PAR and this small amount, of energy sustains the entire living world., Therefore, it is very important to know, how the solar energy captured by plants flows, through different organisms of an ecosystem., Directly or indirectly, all organisms are, dependent for their food on producers. Hence, there is unidirectional flow of energy from, sun to producers and then to consumers. The, direction can not be reversed. Energy can be, used only once in the ecosystem., The autotrophs need a constant supply, of energy to synthesize the molecules they, require. The autotrophs are called producers., In a terrestrial ecosystem, major producers, are herbaceous and woody plants. Likewise,, producers in an aquatic ecosystem are, phytoplankton and algae., Find out, 1. Is there any presence of living organisms, in the perpetual darkness of deep oceanic, trenches?, 2. In absence of solar radiation, what is their, source of energy?, 3. Which organisms do serve as producers in, the food chains of deep oceans?, All animals directly or indirectly, depend on plants for their food. They are hence, , called consumers (heterotrophs). If they feed, directly on the plants, they are called primary, consumers, and if the animals eat other animals, which eat plants, they are called secondary, consumers. Likewise, you could have tertiary, consumers too., The primary consumers are also known, as herbivores. Some common herbivores are, insects (grasshopper, aphids), birds (parrot), and some mammals (sheep, cattles, goat,, donkey) in terrestrial ecosystem and molluscs, in aquatic ecosystem. The consumers that feed, on these herbivores are carnivores, (secondary, consumers). Those animals that depend on, the primary carnivores for food are called, secondary carnivores., Examples, Man, lion, , Tertiary, Consumer, , Fourth Trophic level, (Top carnivore), , Secondary, Consumer, , Third trophic, level (Carnivores), , Birds, fish, and wolf, , Primary, Consumer, , Second trophic, level (Herbivores), , Zooplankton,, grasshopper, and cow, , Primary, Producer, , First Trophic level, (Photoautotrophs), , Phytoplankton,, grass, trees, , Chart 14.4 : Trophic levels, You have studied several food chains, and food webs that exist in nature. Food chains, are always straight and usually have four or, five trophic levels. There are three types of food, chains viz. grazing, detritus and parasitic., Starting from the plants (or producers) food, chains and food webs are formed such that an, animal feeds on a plant or on another animal, and in turn is food for another. The energy, trapped by the producer, is either passed on to, a consumer or remains trapped till the producer, organism dies. Death of organism is the, beginning of the detritus food chain/web., , 311
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A simple grazing food chain (GFC) is, depicted below:, Deer, , Leopard, (Secondary, consumer), , (Primary, Consumer), , The detritus food chain (DFC) begins, with dead organic matter. It is composed, of decomposers which are heterotrophic, organisms, mainly fungi and bacteria. They, meet their energy and nutrient requirements, by degrading the detritus. These are known as, saprotrophs. Decomposers secrete enzymes, that breakdown dead organic materials, into simple, inorganic materials, which are, absorbed by them. Detritus food chain may be, connected with the grazing food chain at some, levels. In a natural ecosystem, some animals, like cockroaches, crows, bears, man, etc. are, omnivores. Omnivores eat producers as well, as consumers. These natural interconnection of, food chains make it a food web., , 1. What could be the connecting points, between the GFC and DFC?, 2. How will you classify man as carnivore, Every, organism, occupies, a place, (primary/, secondary), or omnivore?, Why?in, ecological, community, to the, source, 3. How many, trophicaccording, levels human, beings, and function, method of, its food. Organisms, in aobtaining, food chain?, occupy a specific place in the food chain that is, their trophic level. Producers belong to the first, trophic level, herbivores (primary consumer), to the second and carnivores (secondary, consumer) to the third trophic level., , 900 Joules of, energy lost to, environment, , 100 Joules, Energy, , (Producer), , Eagle, Python, Wolf, Rat, Frog, , Butterfly, Fruit fly, , Grasshopper, , Corn, , Mangoes, A flowering plant, , Lavenders, , Fig. 14.5 : Food web, , 9 Joules of, energy lost to, environment, , 10 Joules, Energy, , (Herbivore), , (Carnivore), , Fig. 14.6 : Energy loss with increasing, trophic level, , Thrush, Dragonfly, , 90 Joules of, energy lost to, environment, , 1000 Joules of, Light Energy, , Grass, (Producer), , Use your brain power, , The amount of energy available, decreases at each successive trophic level., The number of trophic levels in any food, chain is restricted as the transfer of energy, follows ‘10% Law’ (R. Lindermann, 1942)., The law states that ‘only 10 % of the energy, is transferred to each trophic level as net, energy, from the previous trophic level’. In, nature, it is possible to have different trophic, levels - producer, herbivore, primary carnivore,, secondary carnivore, tertiary carnivore and, ultimate carnivore., , Can you tell?, •, , From the given food web diagram, give, the trophic levels where the eagle is present., , Think about it, , What is the maximum number of, trophic levels in a food chain?, 312
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Beyond secondary carnivores, however, the amount of energy available is too less,, hence, there is no tertiary carnivore that feeds, exclusively on secondary carnivore, even, though the secondary carnivore many times will, feed on herbivores directly. This is the reason, why food chains do not exist in isolation, but, are always interconnected to form food web, that maintains the stability of an ecosystem., , Tertiary, Consumer, Secondary, Consumers, Primary, Consumers, Producers, , 14.3 Ecological Pyramids :, Ecological pyramid is a graphic, representation of the relationship between the, organisms of various successive trophic levels, with respect to energy, biomass and number., , •, , 900 kg grasses, , 2nd Trophic, level, 1st, Trophic, level, , Think about it, , How would you explain inverted, pyramid of biomass in oceanic ecosystem?, , The base of each pyramid represents the, producers or the first trophic level while the, apex represents tertiary or top level consumer., Any calculations of energy content, biomass,, or numbers, has to include all organisms at that, trophic level., , Tertiary, consumer, Secondary, consumers, Primary, consumers, , The three ecological pyramids which are, usually studied are : Pyramid of biomass,, Pyramid of numbers and Pyramid of energy., , In most well balanced ecosystems, all the, pyramids, of number, energy and biomass are, upright, i.e. producers are more in number and, biomass than the herbivores, and herbivores, are more in number and biomass than the, carnivores. There are exceptions to this, e.g., oceanic ecosystem show inverted biomass, pyramid., , 100 kg mice, , Fig. 14.7 : Pyramid of Biomass, , Pyramid is a structure which has broader, base that gradually narrows upwards forming, an inverted cone like structure. This concept, was developed by C. Elton in 1927., , The relative number of individuals per, unit area at different trophic levels, constitutes, the number pyramid; of biomass/ unit, area, is biomass pyramid and of amount of, accumulated energy per unit area, is energy, pyramid., , 4th Trophic, level, 10 kg, owls, 3rd Trophic, 50 kg snakes, level, , 5, , 5000, , 500,000, , Fig. 14.8 : Pyramid of Numbers, Similarly, pyramid of numbers can also be, sometimes inverted. e.g. if we plot the number, of insects on a single tree, smaller birds feeding, on insects, and parasites on those birds, we get, an inverted pyramid., , 313, , Use your brain power, What will happen, if in the above, example, we substitute larger bird of prey, feeding on small insect eating birds?
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Pyramid of energy is always upright,, can never be inverted, because when energy, flows from a particular trophic level to the next, trophic level, some energy is always lost as, heat at each step. In smaller food chains, more, energy is available than in the longer food, chains., Tertiary, consumers, 0.1%, Secondary, consumers 1%, , Primary consumers 10%, , Producers 100%, , Fig. 14.9 : Pyramid of Energy, There are certain limitations of, ecological pyramids. It assumes a simple food, chain, something that almost never exists in, nature. It does not accommodate a food web., Moreover, saprophytes are not given any place, in ecological pyramids even though they play a, vital role in the ecosystem., A given species may occupy more than, one trophic levels in the same ecosystem at, the same time, e.g. a sparrow is a primary, consumer when it eats seeds, fruits, peas, and, a secondary consumer when it eats insects and, worms., 14.4 Nutrient Cycles :, We have studied in earlier classes, that all organisms need a constant supply of, nutrients to grow, and reproduce. The amount of, nutrients, such as carbon, nitrogen, phosphorus,, calcium, etc. present in the soil, varies in, different kinds of ecosystems on a seasonal, basis. These nutrients, which are never lost, from the ecosystems, are recycled indefinitely., The movement of nutrient elements through, , the various components of an ecosystem, is, called nutrient cycling. Another name of, nutrient cycling is biogeochemical cycle. Here,, essential elements are cycled from abiotic to, biotic world and back., Types of Nutrient cycles : There are two types, of nutrient cycles viz. (a) gaseous and (b), sedimentary. The reservoir for gaseous type of, nutrient cycle (e.g., nitrogen, carbon cycle) is, the atmosphere and for the sedimentary cycle, (e.g. phosphorus cycle) the reservoir is Earth’s, crust. The function of the reservoir is to meet, with the deficit, which occurs due to imbalance, in the rate of influx and efflux in any ecosystem., Carbon Cycle :, All life forms on earth are carbon based, because carbon is the main component of, all the organic compounds of protoplasm. It, constitutes 49% of dry weight of organisms. If, we look at the total quantity of global carbon,, we find that 71% carbon is found dissolved in, oceans. This oceanic reservoir regulates the, amount of carbon dioxide in the atmosphere., Sunlight, Atmospheric, CO2, , Industrial, commercial, residential, Human and, automotive, Photosynthesis, respiration Vegetation emissions, plant, Organic, respiration, carbon, Organism decay, Root, Dead organisms and, respiration, waste products, , Human uses, , Fossil fuels, , Fig. 14.10 : Carbon cycle, Carbon that is a part of rocks and fossil, fuels like oil, coal and natural gas, has been, away from the rest of the carbon cycle for a, long time. These long-term storage places, , 314
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are known as “sinks”. When fossil fuels are, burned, carbon that had been underground is, released back into the air as carbon dioxide., The element carbon is a part of seawater,, the atmosphere, rocks such as limestone and, coal, soils, as well as all living things., • Carbon as CO2 moves from the atmosphere, to plants. Through the process of, photosynthesis, carbon dioxide is pulled, from the air to produce food., • Carbon moves from plants to animals,, through food chains, i.e. the carbon present, in plants moves to the animals., • Carbon moves from living things to the, atmosphere. Each time you exhale, you are, releasing carbon dioxide gas (CO2) into the, atmosphere., • Decomposers also contribute substantially, to CO2 in atmosphere, by their processing of, waste materials and dead organic matter of, land and oceans., • When fossil fuels burn to power factories,, power plants, motor vehicles, most of the, carbon quickly enters the atmosphere as, carbon dioxide gas. Each year, 5.5 billion, tons of carbon is released through combustion, of fossil fuels. Of this massive amount, 3.3, billion tons stays in the atmosphere. Most, of the remainder is dissolved in seawater, and deposited as calcium or magnesium, carbonate compounds which make up shells, of marine animals., • Burning of wood, forest fire and combustion, of organic matter, fossil fuel and volcanic, activity, are additional sources for releasing, CO2 in the atmosphere., • Carbon moves from the atmosphere to the, oceans. The oceans and other water bodies,, absorb some carbon in the form of CO2 from, the atmosphere. The carbon is dissolved into, the oceanic water. Some amount of the fixed, carbon is lost to sediments and removed, from circulation., , • Fossil, , fuels represent a reservoir, of, carbon. Carbon cycling occurs through, atmosphere, ocean and through living and, dead organisms. Human activities have, significantly influenced the carbon cycle., • Rapid deforestation and massive burning, of fossil fuel for energy and transport, have, significantly increased the rate of release of, carbon dioxide into the atmosphere., Thus, the entire carbon cycle is run, by basic processes viz. Photosynthesis,, Respiration, Decomposition, Sedimentation, and Combustion., Phosphorus Cycle :, Cyclic movement of phosphorus through, hydrosphere, lithosphere and biosphere, constitutes phosphorus cycle., Phosphorus is a major constituent of, biological membranes, nucleic acids and, cellular energy transfer systems. Many animals, also need large quantities of this element to, make shells, bones, hooves and teeth., The natural reservoir of phosphorus is, rock, which contains phosphorus in the form of, phosphates. When rocks are weathered, minute, amounts of these phosphates dissolve in soil, solution and are absorbed by the roots of the, plants. Herbivores and other animals obtain, this element from plants. The waste products, and the dead organisms are decomposed by, phosphate-solubilizing, bacteria, releasing, phosphorus. Unlike carbon cycle, there is, no respiratory release of phosphorus into, atmosphere., There are two major differences between, carbon and phosphorus cycle. Atmospheric, inputs of phosphorus through rainfall are much, smaller (meagure) than carbon inputs, and, secondly, exchanges of phosphorus between, organism and environment are negligible as, compare to carbon., Unlike carbon and nitrogen, Phosphorus, is always in short supply and hence acts as, , 315
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Rain, , Geological uplifting, , Plants, Weathering of, phosphate from, rocks, , Runoff, , Phosphate in solution, Phosphate in, Animals, , Detritus settling, , soil, Leaching, , to bottom, , Sedimentation = new rocks, Decomposers, , Fig. 14.11 : Phosphorus Cycle, limiting factor for the plant growth. Sudden, influx of phosphorus in the form of agricultural, runoff or industrial effluents rich in phosphate, content, leads to eutrophication in water, bodies. Eutrophication is due to overgrowth, of algae at the instance of high phosphorus, disolved in water. The overgrowth of algae, kills or harms the aquatic life., Internet my friend, What are the long term and short-term, effects of eutrophication in water bodies?, 14.5 Ecological Succession :, Succession : It is a spatial pattern which occurs, over the time. Time is a crucial factor. The, ecosystem is occupied by the pioneer species., As time passes, species diversity increase, giving way to more complex organisms., , Eventually, it leads to climax community., Climax community does not evolve further., The gradual and predictable change in the, species composition of a given area is called, ecological succession. The change is sequential, and environmentally regulated., Process of succession involves sequential, steps like Nudation, Invasion, Ecesis,, Aggregation, Competition and co-action,, Reaction and stabilization., During succession, some species colonize, an area and their populations become more, numerous, whereas populations of other species, decline and even disappear., The entire sequence of communities that, successively change in a given area, constitute, what is called sere(s). Alternatively, it is an, entire gradient of organisms from pioneer stage, to climax stage.The individual transitional, , 316
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communities are termed seral communities. In, the successive seral stages, there is a change in, the diversity of species of organisms, increase, in the number of species and organisms as well, as an increase in the total biomass., The present day communities in the world, have come to be, because of succession that, has occurred over millions of years since life, started on earth. Succession is hence a process, that starts where no living organisms were, present before - like on a newly formed volcanic, island. This is called primary succession., Other examples of areas where primary, succession occurs are newly cooled lava,, rocks and newly created pond or reservoir. The, establishment of a new biotic community is, generally very slow. Before a biotic community, of diverse organisms can become established,, there must be soil. Depending mostly on the, climate, it takes natural processes, several, hundred to several thousand years to produce, fertile soil on bare rock., Secondarysuccession beginsinareaswhere, natural biotic communities have been destroyed, such as in abandoned farm lands, burned or cut, forests, lands that have been flooded, etc. Since, some soil or sediment is present, succession is, faster than in primary succession. Description, of ecological succession usually focuses, on changes in vegetation. However, these, vegetational changes in turn affect food and, shelter for various types of animals. Thus, as, succession proceeds, the numbers and types of, animals and decomposers also change. At any, time during primary or secondary succession,, natural or human induced disturbances (fire,, deforestation, etc.), can convert a particular, seral stage of succession to an earlier previous /, preceding stage. Also, such disturbances create, new conditions that encourage some species, and discourage or eliminate other species., Succession of Plants :, Based on the nature of the habitat – whether, it is water (or very wetland areas) or it is on, very dry areas – succession of plants, is called, , hydrarch (hydrosere) or xerarch (xerosere),, respectively., Hydrarch succession takes place in wetter, areas and the successional series progress from, hydric to the mesic conditions. As against this,, xerarch succession takes place in dry areas, and the series progress from xeric to mesic, conditions. Hence, both hydrarch and xerarch, successions lead to medium water conditions, (mesic) – neither too dry (xeric) nor too wet, (hydric)., The species that invade a bare area, are, called pioneer species. In primary succession, on rocks these are usually crustose lichens, which are able to secrete acids to dissolve, rock, helping in weathering of rocks and soil, formation. These pave the way for bryophytes,, mosses that are able to take hold in the small, amount of soil., They are, with time, succeeded by, herbaceous plants, and after several more, stages, ultimately a stable climax forest, community is formed. The climax community, remains stable as long as the environment, remains unchanged., In primary succession of aquatic habitat,, (steps 1 to 7 in fig. 14.13) the pioneers are, the small phytoplankton. They are replaced, with time by rooted-submerged plants (e.g., Hydrilla), rooted-floating angiosperms (e.g., Lotus) followed by free-floating plants (e.g., Pistia), then reed swamp (e.g. Typha), marshmeadow (e.g. Cyperus), scrub (e.g. Alnus) and, finally the trees (e.g. Quercus). The climax, again would be a forest. With passage of time,, the water body is converted into land., In secondary succession, the species that, invade depend on the condition of the soil,, availability of water, the environment as also, the seeds or other propagules present. Since, soil is already there, the rate of succession is, much faster and hence, climax is also reached, more quickly. Figure 14.14 shows the sequence, of stages 1 to 8 in a forest ecosystem after fire., , 317
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Bare rock, , Lichens, , Small, annual, plants,, lichens, , Perennial, herbs,, grasses, , Grasses, shrubs, shadeintolerant trees, , Pioneer stages, , Intermediate stages, , Shade-tolerant trees, , Climax community, , Fig. 14.12 : Xerarch Succession of Plants, , 1 Phytoplankton stage, , 4 Reed-swamp stage, , 2 Submerged plant stage, , 5 Marsh-meadow stage, , 3, , Submerged and free, floating plant stage, , 14.6 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 ecosystem services,, for example, healthy forest ecosystems purify, air and water, mitigate droughts and floods., The Millennium Ecosystem Assessment, report 2005 defines Ecosystem services as, benefits people obtain from ecosystems and, identifies four categories of ecosystem services, as follows., , 6 Scrub stage, , •, , Supporting services include services such, as nutrient cycling, primary production, soil, formation, habitat provision and pollination, maintaining balance of ecosystem., , •, , Provisioning services include food, (including, seafood), raw materials, (including timber, skins, fuel wood), genetic, resources (including crop improvement, genes, and health care), water, medicinal, resources (including test and assay, organisms) and ornamental resources (furs,, feathers, ivory, orchids, butterflies, etc.), Regulating services include Carbon, sequestration, Predation regulates prey, populations, Waste decomposition and, detoxification, Purification of water and air,, and pest control., , 7 Climax forest, , Fig. 14.13 : Hydrarch Succession of Plants, It is important to understand that succession,, particularly primary succession, is a very slow, process, maybe requiring thousands of years, for the climax to be reached., Another important fact to understand is, that all the successions whether taking place in, water or on land, proceed to a similar climax, community – the mesic., , •, , 318
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Forest, , Forest fire, , 1, , Severe forest fire, , 2, , 7, , 8, , Forest stage, , Total nudation of forest land, , 3, , 6, , Wood land stage, , 4, , 5, , Shrubs, , Soil and herbs, Terrestrial plants, , Fig. 14. 14 : Secondary succession in a forest ecosystem after fire, •, , Cultural services include cultural, spiritual, and historical, recreational experiences,, science and education, and Therapeutics, (including animal assisted therapy), Following are the main ecological, services :, Fixation of atmospheric CO2 and release, of O2 are the most important services provided, by an ecosystem. Photosynthetic activity of, photoautotrophs sequesters carbon (in CO2, form) from the atmosphere and releases O2 as a, , byproduct. O2 not only purifies air but is also, used for respiration by all aerobes., Pollination of plants brought about by, wind, water or other biotic agencies, is also an, important ecosystem service, without which, there would be no crops and no fruits., Though the value of all such services of, biodiversity is difficult to determine, it seems, reasonable to think that biodiversity should, carry a hefty price tag., , Activity :, 1. Fill in the banks in the given diagram and identity., , 2. Collect information and prepare a chart of the sequential steps involved in the, ecological succession, explaining each step., 319
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Exercise, Q. 1 Multiple choice questions, 1. Which one of the following has the, largest population in a food chain?, a. Producers, b. Primary consumers, c. Secondary consumers, d. Decomposers, , Q. 2 Very short answer question., 1. Give an example of ecosystem which, shows inverted pyramid of numbers., 2. Give an example of ecosystem which, shows inverted pyramid of biomass., 3. Which mineral acts as limiting factor for, productivity in an aquatic ecosystem., , 2. The second trophic level in a lake is, a. Phytoplankton, c. Benthos, , 4. Name the reservoir and sink of carbon in, carbon cycle., , b. Zooplankton, d. Fishes, , Q. 3 Short answer questions., 1. Distinguish between upright and, inverted pyramid of biomass, , 3. Secondary consumers are, a. Herbivores, b. Producers, c. Carnivores, d. Autotrophs, , 2. Distinguish between Food chain and, Food web., , 4. What is the % of photosynthetically, active radiation in the incident solar, radiation?, a. 100%, b. 50 %, c. 1-5%, d. 2-10%, , Q 4. Long answer questions., 1. Define ecological pyramids and describe, with examples, pyramids of number and, biomass., , 6. Givethetermusedtoexpressacommunity, in its final stage of succession?, a. End community, b. Final community, c. Climax community, d. Dark community, 7. After landslide which of the following, type of succession occurs?, a. Primary, b. Secondary, c. Tertiary, d. Climax, 8. Which of the following is most often, a limiting factor of the primary, productivity in any ecosystem., a. Carbon, b. Nitrogen, c. Phosphorus, d. Sulphur, , 320, , 2. What is primary productivity? Give, brief description of factors that affect, primary productivity., 3. Define decomposition and describe, the processes and products of, decomposition., 4. Write important features of a, sedimentary cycle in an ecosystem., 5. Discribe carbon cycle and add a note, on the impact of human activities on, carbon cycle., Project :, 1. Collect the information on the various, services offered by dense forest, ecosystem., 2. Collect the information of various, types of pollinators and the impact of, human activity on them.
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15, , Biodiversity, Conservation and Environmental Issues, Can you recall?, , 1. You have learnt about Chipko movement, and efforts of Shri. Jadav Payeng in, school. What is the importance of such, activities?, 2. Why should we have national parks and, sanctuaries?, 3. We have read about how Indian scientists, won the battle for patent of Turmeric and, Basmati rice. Why was gaining these, patents essential?, 4. What is in situ and ex situ conservation?, Diversity is variety. This variety of life is, called biodiversity. Biodiversity includes a vast, array of species of microorganisms- viruses,, algae, fungi, plants and animals occurring on, Earth, either in terrestrial or aquatic habitat, and the ecological complexes of which they, are part., The diversity is with respect to size, (microscopic to macroscopic), shape, colour,, form, mode of nutrition, type of habitat,, reproduction, motility, duration of life cycle, span, etc. This is actually due to the attempt, of living beings to accomodate with different, environmental conditions (like climatic,, edaphic, topographic, geographic, etc.), or situations, solely for their survival and, perpetuation. In doing so, living organisms, adapt themselves to overcome different, situations and thus develop distinct but, different features and that has actually lead to, the diversity in them. The diversity in features, become infused in the life cycle. In short, these, adaptations in different environments serve as, basis for diversity., , Definition of Biodiversity : It is the part of, nature which includes the differences in the, genes among the individuals of a species; the, variety and richness of all plants and animal, species at different scales in a space - local, regions, country and the world; and the types of, ecosystem, both terrestrial and aquatic, within, a defined area., The term biodiversity was actually coined, by Walter Rosen (1982) but the term was, popularised by sociologist Edward Wilson to, describe combined diversity at all the levels of, biological organisation., Biodiversity that we see today, is the, outcome of over 3.5 billion of years of, evolutionary history mainly influenced by, natural processes and of late by influence of, humans., In this chapter, we shall study the basic, concepts of biodiversity such as levels and, patterns of biodiversity, expanse, importance,, loss and conservation methods and efforts, undertaken., 15.1 Levels of Biodiversity:, Diversity of living world can be observed, at various levels, ranging from molecular, to ecosystem level. Major hierarchial and, interrelated levels are genetic diversity, species, diversity (community), and ecosystem diversity, (ecological)., , 321, , Can you tell?, What can you say about species, diversity A and B?, A, , B
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a. Genetic diversity:, It is the intraspecific diversity. It is the, diversity in the number and types of genes, as well as chromosomes present in different, species and also the variation in the genes and, their alleles in the same species. It includes, variation within a population and diversity, between populations that are associated, with adaptation to local conditions. Genetic, variations (e.g. allelic genes) lead to individual, differences within species. Such variations pave, way to evolution. They also improve chances, of continuation of species in the changing, environmental conditions or allow the best, adapted to survive. Existence of subspecies,, races are examples of genetic diversity. Greater, the diversity, better would be sustenance of a, species. You know about 1000 varieties of, mangoes and 50,000 varieties of rice or wheat, in India., Another case of genetic diversity is : a, medicinal plant Rauwolfia vomitoria which, secretes active component reserpine, is found, in different Himalayan ranges. This plant, shows variations in terms of potency and, concentration of active chemical, from location, to location., Genetic diversity or variability is essential, for a healthy breeding population of a species., b. Species diversity:, It is the interspecific diversity. The, number of species of plants and animals that, are present in a region, constitutes its species, diversity. Some areas or regions are richer, in species than in the other regions. Species, diversity deals with variety of species (species, richness) as well as number of individuals of, different species (species evenness) observed, in area under study. E.g. amphibian species, diversity is more in western ghats than in eastern, ghats. Natural undisturbed tropical forests have, much greater species richness than monoculture, plantation of timber plant, developed by forest, plantation. India is one among 15 nations that, are rich in species diversity., , c. Ecological (Ecosystem) diversity:, It is related to the different types, of ecosystems/ habitats within a given, geographical area. There are a large variety, of ecosystems on Earth having their own, complement of distinctive interlinked species,, based on the differences in the habitat. It, can be described for a specific geographical, region. Generally, there may be one or many, different types of ecosystems in a region. Thus,, ecosystem diversity is very high in India while, it is quite low in Norway. In India, we can find, a great variety of ecosystems - deserts, rain, forests, deciduous forests, estuaries, wetlands,, grasslands, etc. The Western ghats show great, ecosystem diversity while regions like Ladakh, and Rann of Kutch do not show variance like, we observe in Western ghats., The diversity of life at all the three levels, is now rapidly being modified by modern, man., 15.2 Patterns of Biodiversity:, There are two patterns viz, Latitudinal, and Altitudinal gradient and species-area, relationship., Think about it, What are latitudes and longitudes?, Which of these imaginary lines are more, significant with reference to diversification, of living beings? Why?, a. Latitudinal and altitudinal gradients :, Biodiversity, barring Arid/ Semiarid and, aquatic habitat, show latitudinal and altitudinal, gradient., Latitudinal : Ecological studies have revealed, that the distribution of diversity is not uniform, around the Globe. Species richness exhibits, latitudinal gradient for many plants and, animals (if not all). It has been observed that, species richness is high at lower latitudes and, there is a steady decline towards the poles., , 322
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Altitudinal : It speaks for the height from mean, sea level (MSL) upwards. Species diversity, is more at lower altitudes than at the heigher, altitudes. It is because at heigher altitudes,, change in the climatic conditions and drastic, seasonal varitations, lead to the decrease in the, species diversity., b. Species-Area relationships :, Scientists have tried to establish relationship, between species diversity and the size of the, habitat. It is considered that number of species, present is directly proportional to the area. It, is understood that larger areas may have more, resources that can be distributed amongst the, inhabitant species. Does this always hold true?, German, naturalist, Alexander Von, , S = CAZ, log S = log C + Z log A, , Species richness, , Factors like overall stability of tropical, regions for millions of years, lesser climatic, changes throughout the year and availability, of plenty of sunlight that favoured speciation., Tropical areas have less often experienced, drastic disturbances like periodic glaciations, observed at poles. Such a stability over millions, of years might have favoured speciation., Lesser migrations in tropics might have, reduced gene flow between geographically, isolated regions and favoured speciation., Scientists also have considered availability of, more intense sunlight, warmer temperatures, and higher annual rainfall in tropics, as factors, responsible for bountifulness of these regions., In more or less constant climatic conditions, and abundance of resources, some animals, enjoy food preferences. For e.g. fruits being, available throughout the year in rain forests,, variety of frugivorous organisms is obviously, more as compared to the temperate regions., In short, species richness or diversity for, plants and animals decreases as we move, away from equator to the poles. It is maximum, in tropical rain forests e.g. Amazon rain forest, (40,000 plants, 1300 birds, 427 mammals,, 3000 species)., , Area, , Fig. 15.1 : Graph showing species area, relationship, Humboldt observed that species richness does, increase with the increase in area but upto, a limit. Observe the graph for species-area, relationship. For many species this curve is a, rectangular hyperbola. If we consider S to be, species richness, A as area under study, C as the, Y intercept and Z as the slope of the line, this, relationship can be described by the equation,, log S=log C+ Z log A., On logarithmic scale this relationship is a, straight line, as observed in the figure above., For smaller areas, value of Z ranges, between 0.1 to 0.2 regardless of species or, region under study., But for the larger areas like the entire, continents, slopes are closer to vertical axis i.e., steeper. This observation indicates that in very, large areas, number of species found, increase, faster than the area explored., Can you tell?, 1. What is biodiversity? Explain genetic, diversity with suitable example., 2. Species richness goes on decreasing as, we move from equator to pole. Explain., Importance of species diversity to the, ecosystem:, Let us now understand whether we really, need all the diversity around us. What if few, species are lost permanently?, , 323
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A community is said to be stable, if, average biomass production remains fairly, constant over a period of time. It should be, strong enough to withstand disturbances and, recover quickly. It also must be resistant to, invasive species. David Tillman carried out, various field experiments and proved that, species richness does help the stability of an, ecological community. Rich diversity leads to, lesser variation in biomass production over a, period of time. This is called ProductivityStability Hypothesis., Paul Ehrlich, an ecologist from Stanford, gave an analogy to explain significance of, diversity. It is called Rivet Popper Hypothesis., He compared Aeroplane to ecosystem and, the species as rivets that keep all parts of, the aeroplane together. Ofcourse, there are, thousands of rivets needed to hold all the parts, of the aeroplane together. If each passenger, decides to pop even one rivet or in other words,, if one species gets extinct, initially not much of, the turbulence will be experienced but slowly,, as number of popped rivets will increase, there, will be a serious threat to the safety of the, aeroplane. Also, which rivets are removed will, also matter., Suppose, rivets at key positions such as, the ones that bind the wings to the body of the, aeroplane, are removed, situation will become, serious. Thus, we can say that relationship, between diversity and well being of ecosystem, is not linear. But it is certain that loss of species, may not pose threat to the ecosystem only, initially. Loss of key species will certainly, cause threat in very short span of time. It will, affect food chains, food web, energy flow,, natural cycles, etc. In short it will affect the, balace of ecosystem., 15.3 Biodiversity Current Scenario, How many species do really exist on earth, and how many of them are found in India? It is, difficult to come to consensus about the exact, , number of species that are present on earth, today. Though over 1.5 million species have, been documented as per IUCN data (2004) so, far, we are yet to study lot more than these. We, are also unaware about speciation process that, might have continued. Most of the studies that, have been carried out are in temperate regions., Tropical rain forests, the major diversity hubs,, are yet to be explored completely. Some, exorbitant numbers like existence of 20 to 50, million varieties have been made. But Robert, May has given convincing estimate of about, 7 million species round the globe. Observe, the given pie charts and find out the relative, share of various plant and animal groups in the, existing knowledge of biodiversity., A., , Known species of Organism, Total, , =, , roughly 1,800,000, , Eubacteria, , species, Protists, Fungi, Plants, Animals, , B. Known species of Animals, Total = roughly 1,315,378 species, Vertebrates, 58,498 species, , Invertebrates, 1,256,880 species, Crustaceans, Echinoderms, Sponges, Cnidarians, Rotifers, Flatworms, Mollusks, Annelid worms, Nematode worms, Arachnids, Insects, , Fish, Amphibians, Reptiles, Birds, Mammals, , C., , Known species of Plants, Total = 287,655 species, , Mosses, Flowering plants, (monocots), , Ferns, Conifers, , Flowering plants, (dicots), , 324, , Fig. 15.2 : Graphic representation of known, animal and plant groups
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In the diagrams, we do not find any data, of prokaryotes. Several moneran species are, not cultivable under laboratory conditions., Also, conventional taxonomic methods are, not suitable for identification of prokaryotic, species., India boasts a handsome share of 8.1% of, total biodiversity wealth of the earth. One of the, 12 megadiversity countries of the globe, India, has 2.4% of total land area of the world. We, have identified around 45000 plant species and, nearly double the number of animal varieties, from our natural wealth. If we consider May’s, estimate of global biodiversity, we have, recorded only 22% of our natural wealth. This, situation underlines the need of taxonomists, to study the biodiversity. But major concern is, the possibility of loss of these varieties before, we identify them because of activities like, reclamation and deforestation., Do you know ?, Recently a group of naturalists proved, that a lizard from Amboli ghat of Maharashtra, was misidentified. They proved it on the basis, of DNA profiling as well as number of glands, and scales present on the legs of the lizard., Earlier thought to be Hemidactylus brookii,, the lizard is now renamed as Hemidactylus, varadgirii in the honour of renowned, herpetologist and conservationist, Dr. Varad, Giri. They also proved that brookii variety is, not found in India., Internet my friend, 1. Find out information about Zoological, Survey of India and Botanical Survey of, India., 2. You may visit Zoological Survey of India,, Pune office and find out how information, about natural wealth is conserved., , 15.4 Loss of Biodiversity:, Loss of biodiversity leads to the overall, imbalance in the ecosystem. The chief serious, aspect of loss of biodiversity is extinction of, species. There are three types of extinction viz,, natural extinction, mass extinction and manmade (anthropogenic) extinction., Damage to biodiversity takes place due to, both, natural and manmade reasons. Natural, reasons include forest fires, earthquakes,, volcanic eruptions etc. Manmade reasons, are habitat destruction, hunting, settlement,, overexploitation and reclamation., Major mass extinction events occured, between Cretaeous and Coenozoic period;, between Triassic and Jurassic period;, between Permian and Triassic period;, between Devonian and Carbaniferous period;, between Ordovician and Silurian period in, the geological time scale where plants as well, as animal groups underwent mass extinction., We are aware of five mass extinctions, during various stages of history of earth (e.g., ice age). The current loss of biodiversity is, considered to be the Sixth extinction which, is progressing at an alarming rate which is, estimated to be 100 to 1000 times faster than, prehuman times. Ecologists blame this to, the human intervention in natural habitats., They do not forget to warn that if the current, trend continues, we might lose about 50% of, diversity. Loss of biodiversity in any area, can lead to the decline in plant production,, lower resilience to environmental disturbance, like flood. It may also lead to alteration in, environmental processes like disease cycles,, plant productivity etc., Causes of Biodiversity losses:, There are four major causes popularly, known as, ‘The Evil Quartet’., i. Habitat loss and fragmentation:, It is the prime cause of destruction., Reduction in vast natural habitats and local, degradation by pollution, create crisis situation, for the living beings. Loss of local habitat due, , 325
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to human activities, creates threat to migratory, birds as well as those animals that need larger, territories. Tropical rain forests are being lost, at an alarming rate. Tropical rain forest cover, has reduced from 14% to 6% over the years., , resources which in turn causes threats to various, organisms. Can you corelate this with dirth, of fish, we observe now a days? Dodo bird,, stellar sea cow and passenger pigeon are few, examples of extinction due to overexploitation., iii. Alien species invasion:, , Do you know ?, Great Indian Bustard alias Maldhok is, a critically endangered bird. It is considered, as flagship species of grasslands. We lost last, Maldhok from Maharashtra in 2018. Now this, bird is found in Rajasthan and Gujrat. It is, an example of local extinction due to habitat, loss and hunting., ii. Over-exploitation:, Basic difference between human beings, and other animals is that, humans have the, tendency to accumulate beyond their needs., This has resulted in the overexploitation of, , When a new species gets introduced into, any ecosystem accidentally or intentionally,, there are chances that it proves harmful for, existing species. Sometimes, it can lead to, extinction of local species. In such a case, it is, called as invasive species. E.g. the carrot grass, (Parthenium), Lantana and water hyacinth, (Eichhornia). Introduction of predator fish Nile perch in Lake Victoria, proved deleterious, for 200 local species of Cichlid fish., In India, introduction of African catfish, Clarias gariepinus for aquaculture purpose has, proved harmful to endemic catfish varieties., One of the major reasons of such a harmful, effect of alien species is, lack of local predator., iv. Co-extinctions:, Many a times, organisms are associated, with each other in obligatory way. In such, cases, extinction of one variety leads to loss, of associate variety from the ecosystem. e.g.,, Extinction of host fish causes extinction of, unique parasites. Coevolved plant-pollinator,, also will have such a threat., , a. Dodo bird, , b. Stellar sea cow, , c. Passenger pigeon, , We are aware of threat to diversity and, loss of species from earth. When any species, is totally eliminated from earth, it is called, extinct. e.g. Dinosaurs. When the number of, members of a species starts dwindling, it is said, to be endangered. The International Union for, Conservation of Nature and Natural Resources, (IUCN) maintains a Red Data Book also, known as Red List, where conservation status, of plant and animal species is recorded., , Fig. 15.3 : Examples of extinction due to, over-exploitation, 326
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Internet my friend, What is ballast water and how can it bring, about introduction of alien species into any, ecosystem?, , Do you know ?, Many a times, we read about leopard, attacks on humans or about elephants, from Karnataka destroying, agricultural, lands and orchards in Sindhudurg region, of Maharashtra. With increase in human, population, man started encroaching forest, land. Animals either out of sheer curiosity, (in case of young leopards) or for lack of, sufficient resources, venture out from their, original place. This results in Man-Animal, conflict., Various measures are adapted by, forest department to minimise this tussle., e.g., Government not only gives monetary, compensation to farmers affected by elephant, attacks, but even the forest department, conducts community meetings to, train, locals to face the attack. Also, measures like, appointing experts to tame the wild elephants, with the help of domesticated elephants, and, sensitising people towards wild life are most, important part of such activities., Do you know ?, The IUCN system uses a set of five, quantitative criteria to assess the extinction, risk of a given species. These criteria are : The, rate of population decline; The geographic, range; Whether the species already possesses, a small population size; Whether the species, is very small or lives in a restricted area;, and Whether the results of a quantitative, analysis indicate a high probability of, extinction in the wild., , After a given species has been thoroughly, evaluated, it is placed into one of following, several categories., 1. Extinct (EX), a designation applied to, species in which the last individual has, died or is not recorded., 2. Extinct in the Wild (EW), a category, containing those species whose members, survive only in captivity, 3. Critically Endangered (CR), a category, containing those species that possess an, extremely high risk of extinction with very, few surviving members (50)., 4. Endangered (EN), a designation applied, to species that possess a very high risk of, extinction as a result of rapid population, decline of 50 to more than 70 percent over, the previous 10 years (or three generations)., 5. Vulnerable (VU), a category containing, those species that possess a very high risk, of extinction as a result of rapid population, decline of 30 to more than 50 percent over, the previous 10 years (or three generations)., 6. Near Threatened (NT), a designation, applied to species that are close to becoming, threatened or may meet the criteria for, threatened status in the near future., 7. Least Concern (LC), a category containing, species that are pervasive and abundant, after careful assessment, 8. Data Deficient (DD), a condition applied, to species in which the amount of available, data related to its risk of extinction, is, lacking in some way., 9. Not Evaluated (NE), a category used to, include any of the nearly 1.9 million species, described by scientists, but not assessed by, the IUCN, Can you tell?, 1. Explain how loss of species diversity can, harm ecosystem?, 2. Give various categories of endangered, species explained by IUCN., 3. What do you understand by invasive, species? How does it affect local, population?, 327
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15.5 Conservation of Biodiversity :, Conservation of biodiversity means, protection,, upliftment, and, scientific, management of biodiversity to maintain, its optimum level and to derive sustainable, benefits for the present and future strategies., Why to conserve Diversity?, The reasons for conservation of biodiversity, can be classified into three categories:, a. Narrowly utilitarian reasons:, Since time immemorial, humans are, reaping material benefits from biodiversity., It may be deriving resources for basic needs, such as food, clothes, shelter or industrial, products like resins, tannins, perfume base etc., For aesthetic use as in ornaments or artefacts., Medicinal use of plants and animals, is another, major factor. It shares 25% of global medicine, market. Around 25000 species are put to use, by tribals worldwide as traditional medicines., Several are yet to be explored for their potential, as medicinal plants., Nowadays bioprospecting of economically, important species is carried out. Bioprospecting, is systematic search for development of, new sources of chemical compounds, genes,, micro-organisms, macro-organisms, and other, valuable products from nature., b. Broadly utilitarian reasons:, If we find out the cost of oxygen cylinder, and try to calculate the value of oxygen we, breathe with such ease; we will understand, what nature is giving us for free! Animals play, a crucial role in pollination and seed dispersal., Amazon forest is estimated to produce 20%, of total oxygen of earths atmosphere. We need, to consider recreational use of diversity too., You must have come across the news, about devastating fires in amazon rainforest in, August 2019., These are mainly caused in Brazil and, are more manmade than natural. The slash, , and burn policy of locals to reclaim forestland, has caused a towering 906000 hectares of, forest devastation, only in the year 2019. We, the humans, need to rethink about our attitude, towards nature!, c. Ethical reasons:, We have no right to destroy the diversity, simply because we share the earth with them!, All living beings have equal right to survive, irrespective of their known or prospective, economic use., Internet my friend, Visit www.gotul.org.in to find out, information about various efforts for, biodiversity conservation in Maharashtra., How do we conserve biodiversity?, Conservation means sustainable use of, natural resources. There are two main types of, conservation strategies :, a. In situ conservation:, Protectionof anorganismwillautomatically, takes place, if its natural habitat is protected., e.g. Announcing Kanha forest as tiger reserve., This is called in situ conservation. This is the, most appropriate method of conservation. It is, nothing but conservation ‘at home’. Around, 34 Biodiversity hotspots have been identified, by the conservationists. These are the regions, with high species richness as well as density., These areas need to be protected strategically, by setting legislative measures apart from, awareness and conservation., In situ conservation also includes, introduction of, varieties, traditionally, used into farming and horticulture. E.g. In, Maharashtra, Pawra tribals in Satpuda have, protected varieties of corn with different, coloured kernels., , 328
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India has three of world’s biodiversity, hotspots (the areas with high density of, biodiversity), Western ghats, Indo-Burma, and Eastern-Himalayas. It has been estimated, that protection of these diversity rich hotspots, could reduce extinction rate by almost 30%., India, at present has 14 biosphere reserves,, 90 national parks and 448 wildlife sanctuaries., In Maharashtra, there are 5 national parks and, 11 sanctuaries., Internet my friend, Collect the information about protected, areas, biosphere reserves, national parks, and wild life sanctuaries., Can you recall?, What are sacred groves?, Indian culture and traditions are always, connected with nature and rituals are laid, down to protect biodiversity. In many cultures,, stretches of forests were set aside and protected, in the name of Almighty, which are called, sacred groves., Such sacred groves are found in Khasi, and Jaintia hills in Meghalaya, Western ghat, regions of Maharashtra and Karnataka, Aravali, hills of Rajasthan and Bastar, and Chanda and, Sarguja areas of Madhya Pradesh., , Sacred groves serve the only chance of, survival for some endangered varieties of, animal and plant species. Tribals do not allow, to cut even a single branch of tree from sacred, grove. But with the increasing lust and greed,, are sacred groves safe? We must think about it., b. Ex situ conservation:, Sometimes when a species is critically, endangered, special measures have to be under, taken to protect it. It might be protected in, captivity, as one of the measures of protection., This is called Ex situ conservation. In this type, of conservation, living beings are protected, away from their natural habitats in special, settings. Wild life safari parks, zoological, parks and botanical gardens serve this purpose., Animals which have decreased in number, are, allowed to breed in captivity in order to protect, them.Eg crocodile bank of Chennai., Seed banks are established to conserve wild, varieties of food grains and vegetables. Now a, days, modern techniques like tissue culture, in, vitro fertilization of eggs and cryopreservation, (preservation at low temperature -1960C), of gametes, are used to protect endangered, species., By now we have, thus, understood the, immense importance of biodiversity and dire, need to protect it., , Do you know ?, , Dr. Akira Miyawaki studied native forests of Japan especially, the old shrine groves and developed a technique of growing dense plantations in short time. It is, a technique for restoration of natural vegetation on degraded land. In this technique, after soil, testing, the landmass is dugout and soil is mixed with local biomass and humus. Plantation is, done in layers and saplings are planted close to each other. Due to this, sunlight doesn’t reach, soil retaining the moisture. Close proximity of plants leads to faster vertical growth than lateral., Also, it promotes natural selection. Native varieties are planted and the forest develops at almost, ten times faster than the natural way. It requires a caring period of 3 years after which it grows, and develops its own diversity naturally. In India, this technique is adapted at several places, including remote districts like Chandrapur as well as metro cities like Mumbai and Bengaluru., Though there is debate about feasibility of the technique, it is certainly helping in retaining and, recharging groundwater table, supporting local biodiversity and curbing air pollution by adding, to green cover., 329
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Know the Conservationist, , Internet my friend, , Rahibai Popere, seed, mother of Maharashtra., Hailing from remote, village in Ahmednagar, district, Rahibai runs, seed bank for 54 crops, and 116 varieties. Crops include wild, varieties of brinjal, guava, mango, spinach,, methi, millets, pulses, hyacinth beans and, peas. She also trains farmers and students for, seed selection, enhancement of soil fertility,, pest management and control. She is among, 3 Indians on BBC list of ‘100 women, 2018’., , Find out information about LACONES,, Hyderabad., 15.6 Biological diversity Act 2002:, India participated in Earth Summit,, Rio de Janeiro and is a party to Convention, on Biological Diversity (CBD-1992)., In order to provide framework for the, sustainable management and conservation of, our country’s natural resources, government, passed Biological Diversity Act (BD Act) in, the year 2002 in compliance with CBD. The, law broadly defines biodiversity, as plants,, animals and microorganisms and their parts,, their genetic materials and by-products. It, excludes value added products and human, genetic material., Regulation of access to Indian biological, resources as well as scientific cataloguing of, traditional knowledge about ethnobiological, materials, were the main objectives for, proposing this act., Athree-tier system has been established with, National Biodiversity Authority (NBA) at the, national level, the State Biodiversity Boards, (SBBs) at the state level, and Biodiversity, Management Committees (BMCs) at the, local level for approval of utilization of any, biological resource for commercial or research, purpose. It is mandatory for foreigners, NRIs, as well as Indian citizens and institutions to, seek permission from NBA before exploiting, local resource. NBA has powers of civil court., Not seeking approval of NBA, can incur jail, and fine up to 10 lakh rupees., , Can you recall?, 1. What is pollution? Enlist its types., 2. Define pollutant. How are our daily, activities responsible for pollution?, 15.7 Environmental issues:, Exponential growth of human population, coupled with industrial development, has, resulted in the rampant loss of natural resources, over last ten decades., This uncontrolled exploitation of nature, disturbed the delicate balance between living, and non-living components of biosphere., Utilization and production of synthetic, materials and construction activities have, pumped several undesired substances in, ecosphere. This has resulted in severe pollution., Noise, pollution, Water, pollution, , Can you tell?, 1. Differentiate between in situ and ex situ, conservation., 2. Name any two modern methods of ex situ, conservation of species., 3. Write a note on BD Act 2002., , Types, of, pollutions, , Air, pollution, , 330, , Soil, pollution, , Radioactive, pollution
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Any substance that causes pollution, is, called Pollutant. In order to protect and improve, the quality of our environment, the Government, of India has passed the Environment Protection, Act 1986., a. Air Pollution :, Effect of air pollution :, Respiratory surfaces of living beings, are constantly interacting with air. Any, unfavourable alteration in air quality, affects, the respiratory system. Severity of damage, depends on concentration of pollutant,, duration of exposure and the organism. Even, in case of plants, air pollution results in poor, yield of crops and premature death of plants., Nowadays automobiles are omnipresent. They, are major cause for atmospheric (air) pollution., Regular maintenance of vehicles and use of, lead-free petrol or diesel can reduce pollutant, from exhausts., Types of air pollutants :, Air pollutants are of two types – particulate, pollutants and gaseous pollutants., Particulate air pollutants may be solid, or liquids. Particles with diameter 10 μm may, settle in the soil but particles with 1 μm or, less remain suspended in the air. According, to Central Pollution Control Board (CPCB),, particulate matter of size 2.5μm or less in, diameter (PM2.5) are responsible for causing, the greatest harm to humans., These fine particulates can be inhaled deep, into the lungs and are responsible for irritation,, inflammation and damage to lungs. In addition, to this, it causes breathing and respiratory, disorders and premature deaths., Smoke, smog, pesticides, heavy metals,, dust and radioactive elements are the examples, of particulate pollutants., Use your brain power, Does particulate matter help to reduce, atmospheric temperature?, , Gaseous pollutants include CO2, CO, SO2,, NO, NO2 etc., Carbon di-oxide is a greenhouse gas., In the past, levels of CO2 in the atmosphere, remained low. Due to burning of fossil fuels,, as well as increasing deforestation the levels of, CO2 are rising at alarming rate. Photosynthesis, process balances CO2 : O2 ratio of the air to, a great extent. CO2 is also removed from the, air by weathering of silicate rocks forming, limestone. A jet plane in a single trip across the, Atlantic uses 35 tonnes of oxygen and releases, 70 tonnes of CO2. We are going to discuss the, role of CO2 in global warming later in this, chapter., Carbon monoxide (CO) :, It is a poisonous gas produced by, incomplete combustion of fuel such as coal or, wood. Vehicular exhausts are the largest source, of CO., Use your brain power, State the effects of CO on human body., Nitrogen di oxide (NO2) and nitrogen, monoxide (NO):, These are released by automobiles and, chemical industries as waste gases. NO2 when, combines with water vapours forms nitric acid., It causes irritation to eyes and lungs. At high, concentration, it causes injury to lungs, liver, and kidneys., Control measures:, Various ingenious mechanisms have been, developed to control emission of gaseous and, particulate pollutants through vehicles and, industries. Few examples are explained below:, Electrostatic precipitator :, It is most widely used for removing, particulate matter like soot and dust present in, industrial exhaust. It can remove almost 99%, particulate matter present in exhaust from a, thermal power plant., , 331
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Precipitator, Positively charged, collector plates, Negatively, charged, metal grid, , Smoke particles, attracted to, collector plates, , Catalytic converters:, Motor vehicles equipped with catalytic, converter should use unleaded petrol because, lead in the petrol, inactivates the catalyst., Carbon monoxide (CO), Hydrocarbons, (HC), , Clean gas, stream, Gas stream containing particles, picks up negative charge, , Fig. 15.4 : Electrostatic precipitator, , Internet my friend, Find out information about carbon foot, print. Think about measures to reduce your, own carbon foot print., Exhaust gas Scrubbers are used to clean air, for both dust and gases by passing it through, dry or wet packing material. It can remove, gases like SO2. In the scrubber, the exhaust is, passed through a spray of water or lime., , Sprayers, , Treated, Flue gas, , Flue gas, with SO2, Collection, tank, CaSO3·2H2O, Boiler, SO2 scrubber, , Smokestack, CaO + H2O, , Water, (H2O), , Carbon, dioxide (CO2), , 1. Exhaust gasses, 3. The, 2. The exhaust gasses, enter the reduction, then enter the oxidation exhaust that, block of the catalyst block of the catalyst where exits the, where the oxides, converter, hydrocarbons and the, of nitrogen react newly formed oxygen react, is less, forming nitrogen, to form carbon dioxide., harmful., and oxygen., N2, CO, CO2, N2, Nox, O2, Nox, O2, H2O, CO, HC, HC, , Particles removed, , In this method, high voltage is applied, and electric discharge takes place which, causes ionisation of air in the smokestack., Free electrons in the ionised air get attached, to the gaseous/dust particles moving up the, stack. These negatively charged particles, move towards the positive electrode and settle, down there. These particles are removed by, vibrations of the electrodes and collected in the, reservoir., , Nitrous oxide, (Nox), , Nitrogen (N2), , Fig. 15.6 : Catalytic converter, Controlling Vehicular Air Pollution : A case, study of Delhi, In the year 1990, Delhi ranked fourth, among 41 most polluted cities of the world., In response to PIL (Public Interest Litigation),, Supreme court of India sent orders to Delhi, government to take appropriate actions., In response, several measures were taken by, Delhi Government. By 2002, all the city buses, were converted to run on CNG (compressed, natural gas). CNG is advantageous over other, fuels because it is economic, burns efficiently, and is adulteration proof fuel., According to new fuel policy, the norms, are set to reduce sulphur and aromatic content, of petrol and diesel. Another provision is, upgradation of engines. For this, Bharat, stage emission standards (BS) are set. These, standards are equivalent to Euro norms and, have evolved on similar lines as Bharat Stage, II (BS II) to BS VI from 2001 to 2017. Let us, observe how the norms have changed in the, following table 15.7, , Fig. 15.5 : Exhaust gas Scrubber, 332
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Table 15.7 :Bharat stage emission standards, in cities of India., Vehicle Norms, Cities of, Implementation, 4, Bharat All metro cities, wheelers Stage II, 4, Bharat Throughout the country, wheelers Stage III since October 2010, 4, Bharat 13 mega cities (Delhi and, wheelers Stage IV NCR, Mumbai, Kolkata,, Chennai,, Bengaluru,, Surat, Kanpur, Agra,, Lucknow, Solapur) since, April 2010., 2, Bharat Throughout the country, wheelers Stage III since October 2010, 3, Bharat Throughout the country, wheelers Stage III since October 2010, , Do you know ?, Pradhan Mantri Ujjwala yojana, (Pradhan Mantri clean fuel programme), It was launched by Prime Minister of, India, on 1st May 2016 to distribute 50 million, LPG connections to women of BPL families., In many BPL families, chullhas are used, where incomplete combustion of wood and, coal leads to CO poisoning. Use of LPG helps, in reducing such household air pollution., , Do you know ?, Inspite of all the measures, New, Delhi and adjoining areas witnessed great, smog between 1st to 9th November 2016. Air, pollution at this time peaked on both 2.5PM, and 10PM levels. This is reported as one of, the worst levels of air quality since 1999., Colder weather and stagnant winds, trap, smoke from various sources like firecrackers,, burning crop stubbles, lit garbage and road, dust. Citizens suffered breathlessness, chest, muscle contraction, irritation in eyes, asthma, and allergy. Administration took certain, measures like closing educational institutions,, suspending of construction or demolition, work, undertaking vacuum cleaning of roads, etc. Even Badarpur thermal power plant was, temporarily closed down. Do you think mere, setting standards is not enough? We must, encourage means like car pooling and use of, public transport., Can you tell?, , Have you noticed that BS V is missing in, above table? Note that, in 2001, Bharat stage, II emission norms were set for CNG and LPG, vehicles. It stipulates that emission of sulphur, be controlled at 50 ppm in diesel and 150ppm, in petrol. Aromatic hydrocarbons should be just, 42% in concerned fuel. The aim is to reduce, sulphur emission to 50ppm in petrol and diesel, along with aromatic hydrocarbons to 35%., Government of India directly adapted BS VI, in the year 2018, skipping BS V. These efforts, decreased the levels of CO2 and SO2 in Delhi., , 1. Describe any 2 particulate and gaseous, pollutants., 2. Explain various technologies used for, removing particulate matter from different, sources of air pollution., 3. What are the ill effects of noise pollution, on human health?, 4. Give any norms for reducing sulphur and, aromatic contents of petrol and diesel., b. Noise pollution :, In India, the Air (Prevention and control, of pollution) Act 1981, amendment 1987,, includes noise as an air pollutant. Noise is an, undesired high level of sound. Noise causes, psychological and physiological changes in, human beings. There is dire need of creating, awareness about noise pollution caused during, festivals and processions in our society., , 333
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Exposure to extremely high sound level, (150 decibels or more) generated during a takeoff of a jet plane or rocket, may damage ear, drums and cause permanent hearing loss., Noise also can cause sleeplessness,, increased heartbeat, altered breathing pattern, and psychological stress. Noise may negatively, interfere with child’s learning and behaviour, pattern. The common sources of noise pollution, are machines, transportation, construction, sites, industries etc., , Activity :, , Increased utilisation and discharge of harmful, waste water in water bodies has caused severe, pollution., Most of the water pollution is manmade., Polluted water may be turbid, foul smelling,, and may contain number of pathogens, heavy, metals, oils etc., Realising the importance of maintaining, the cleanliness of the water bodies, Government, of India has passed the Water (prevention and, control of pollution) Act 1974 to safe guard, our water resources., , Find out different sources of noise, pollution in your surrounding., , Can you recall?, , Reduction of noise in our industries can, be brought about by use of sound absorbent, materials or by muffling the noise. Laws which, prohibit blowing horn in the areas of schools, and hospitals, need to be implemented strictly, to curb decibel levels., Govt. of India has rules and regulations, against firecrackers and loudspeakers. Supreme, court of India has banned loudspeakers at, public gatherings after 10pm., Internet my friend, , 1. Where does domestic waste water go in, urban and rural areas?, 2. What is importance of sewage treatment, plant?, Domestic sewage and Industrial Effluents:, Even a small quantity of about 0.1%, impurities in water, can make it unfit for, human consumption. Solids are relatively easy, to separate but dissolved salts such as nitrates,, phosphates, other nutrients and toxic metal ions, as well as organic compounds, are difficult to, remove., Domestic sewage is one of the most, common source of water pollution. It contains, biodegradable organic matter. It readily, gets decomposed by bacteria and other, microorganisms. They use organic matter as, substrate and utilise some amount of sewage., , We have studied about health effects of, noise pollution on humans. How does this, pollution affect birds? Does it affect marine, life? Find out., Can you recall?, 1. Define water pollution., 2. When will you call a water body polluted?, c. Water Pollution and its Control:, Water has been a controlling factor in, distribution and density of living beings in an, area. Human water consumption increased, many folds with increased industrialisation., , It is possible to estimate biodegradable, organic matter in sewage water by measuring, Biochemical Oxygen Demand (BOD). It is, the amount of dissolved oxygen required by, microorganisms for decomposing the organic, matter present in water. It is expressed in, milligram of oxygen per litre (mg/L) of water., High BOD indicates intense level of microbial, pollution., , 334
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Microorganisms involvedin biodegradation, of organic matter in water body consume lot, of dissolved oxygen. This results in sharp, decline in oxygen level of water which leads, to mortality of fish and other aquatic creatures., , Stinking eutrophic lake with coloured and turbid, water, , Presence of large amount of nutrients in, water causes excessive growth of planktonic, free-floating algae specially, blue green algae., This is called algal bloom which gives colour, to the water bodies. Algal bloom often releases, toxins in water. So, fish die due to toxicity., Quality of water deteriorates and becomes, toxic for human beings and other animals., , Death of aquatic animals including fish, , Another threat to aquatic ecosystem, is, water hyacinth (Eichhornia crassipes). It is, an aquatic plant, native of amazon basin,, highly problematic invasive species. It was, first introduced in India for its lovely purple, coloured flowers. But, now it is a nuisance as, it grows excessively and covers entire water, body. This plant grows faster than our ability, to remove it. It is commonly called ‘Terror of, Bengal’., Natural Eutrophication is aging of a lake, due to nutrient enrichment of water. Depending, on the size of the lake, climatic conditions and, other factors, natural aging of lakes require, thousands of years. However, due to pollutants, from human activities like effluents from, agricultural lands, industries and homes (house, hold) have accelerated this aging process. This, phenomenon is called Cultural or Accelerated, Eutrophication. Observe the flow chart and, understand the process of eutrophication., This results in non-availability of dissolved, oxygen for aquatic organisms. This leads to, death of fish and other aquatic organisms. Its, decomposition further depletes the dissolved, oxygen. So, a lake can literally get choked to, death., A few substances usually present in, industrial waste waters can undergo biological, magnification. The phenomenon through which, , Loss of species diversity, , Reduced contents of dissolved oxygen, , Increase in organic loading of lake, Death of submerged plants due to reduced, light, Biological enrichment of water (algal bloom,, planktonic algae and higher plants), Nutrient enrichment of water, , Fig. 15.8 : Eutrophication, certain pollutants get accumulated in tissues in, increasing concentration along the food chains, (successive trophic levels) is called Biological, Magnification (Biomagnification), , Fish-eating birds of prey, 25 ppm, Large fish, 2 ppm, Small fish, 0.5 ppm, Zooplankton, 0.04 pp, , Water, 0.000003 ppm, , Fig. 15.9 : Biomagnification of DDT, Many of the pesticides are non-degradable., So, they get accumulated in the tissues of, organisms. They neither get metabolised nor, are excreted., , 335
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They are passed on to the next trophic, level. This is commonly seen in case of DDT, and Mercury. Observe the food chain in the, given figure. It shows how biomagnification of, DDT takes place., Use your brain power, Why do you think the amount of DDT, is maximum in birds?, Thermal pollution of water is caused, due to rise in temperature of water. The main, source of thermal pollution are the thermal, and nuclear power plants. The power plants, use water as coolant and release hot water. As, many organisms are sensitive to temperature,, sudden rise in temperature leads to loss of flora, and fauna., , When the pit of an ecosan toilet fills up, it, is closed and sealed. After about 8-9 months,, the faeces are completely composted to organic, manure.There are working EcoSan toilets in, many areas of Gujrat, Kerala, Tamilnadu and, Sri Lanka., Recycling of sewage water by reverse, osmosis will help to solve the problem of not, only scarcity of water but also the disposal of, sewage water. At Tirumala hills, millions of, pilgrims visit. Every building here has R.O., system which solves the problem of huge, water demand. Recycling of sewage water, is seen in many townships in Mumbai. Rain, water harvesting is encouraged and made, mandatory for new constructions by Municipal, Corporation., Can you tell?, 1. Explain BOD and its effects on aquatic, ecosystem., 2. Ecological sanitation is the need of the, day. Justify., 3. Explain the phenomenon of biological, magnification., , Internet my friend, 1. Find out biomagnification of diclofenac, and DDT in birds., 2. Find out various types of agrochemicals, which have ill effects on ecosystem., Measures to reduce sewage water:, In order to conserve water and prevent, creation of sewage, ecosan is a sustainable, system for handling human excreta using dry, composting toilets. This is a practical, efficient, and cost-effective solution for human waste, disposal., Ecological sanitation (Ecosan) is an approach, to sanitation provision which safely reuses, excreta in agriculture. It reduces the need for, chemical fertilizers., Ecosan toilet is a closed system that does, not need water. It is an alternative to leach pit, toilets in place where water is scarce or where, there is risk of ground water contamination., It is based on the principle of recovery and, recycling of nutrients from excreta to create a, valuable resource for agriculture., , Solid Waste Management :, You have already studied about solid waste, management in ninth standard., Can you recall?, 1. Why is it necessary to separate wet and, dry garbage?, 2. What are the six R’s to combat solid, waste?, Solid waste is everything that goes to trash., It includes wastes from home, offices, stores,, schools, hospitals etc. Wastes are collected, and disposed by municipality. Municipal solid, waste generally consists of paper, food, plastic,, glass, metals, rubber, leather, textile etc;, Burning reduces volume of the waste., Generally, it is not burnt to completion. So, open dumps become breeding ground for rats, and flies., , 336
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Sanitary landfills are substitute for open, burning dumps. Here wastes are dumped in, depression or trench. Everyday wastes are, added to this pit. Landfills get filled very, soon especially in metro cities. The amount of, garbage generated is too high. In addition to, this, there is a danger of chemicals percolating, and reaching down to ground water and, contaminate this water source., All wastes can be categorised in three, types1. Bio degradable, 2. Recyclable, 3. Non bio degradable, Our rag pickers and kabadiwallahs do, a great job of separation of materials for, recycling. Primary goal of all citizens should, be to reduce generation of waste., The biodegradable materials can be put, into deep pits in the ground and left for natural, degradation. Non biodegradable wastes have, to be disposed off., Maharashtra, government, in, a, rd, notification on 23 June 2018 banned use, of plastic to fight pollution caused due to, extensive use of plastic. Ban on the use, sale,, distribution and storage of plastic material., Mission-Plastic Free Maharashtra :, The union environment ministry has, amended rules in 2016 in order to strengthen, the implementation of environmentally sound, management of hazardous waste in the, country., It also includes ban on use of Thermocol., Large amount of use of plastic can be, avoided, if we inculcate the habit of carrying, cloth bags when we go for shopping and, strictly refusing plastic bags from the venders., Goverment should charge high penalty/fine, for the individuals not abiding by this rule., Hospitals generate harmful waste that, contains disinfectants, harmful chemicals and, also pathogenic microorganisms., , Such wastes require careful treatment and, disposal. You are aware of colour code for, disposal of biomedical waste., Irreparable computers and other electronic, goods as well as electrical waste are known, as e wastes. They are buried in landfills or, are completely burnt. Major part of e waste, generated by developed countries are exported, to developing countries like China, India and, Pakistan. During recycling process of this, waste, metals like copper, iron, silicon, nickel, and gold are recovered. Developed countries, have facilities for recycling of e waste. In, developing countries, manual participation, is involved. So, workers are exposed to toxic, substances from e waste. Treatment of e waste, should be carried out in environment friendly, manner., You have already studied about radioactive, pollution., Can you recall?, 1. What is greenhouse effect?, 2. Enlist greenhouse gases., 3. How do you corelate green house effect, and global warming?, 15.8 Greenhouse effect and Global warming:, Greenhouse effect : It is responsible for heating, of earth’s surface and atmosphere. Without, greenhouse effect, the average temperature, of Earth would have been -180C rather than, average of 150C., Of the solar radiation that reaches earth,, Clouds and gases reflect about 1/4th and absorb, some of it. But half of total incoming radiations, reach the earth’s surface and heat it. Small, portion of it, is reflected back. Earth’s surface re, emits the heat in the form of infrared radiations., Part of these radiations do not escape into the, space because atmospheric gases (CO2, CH4), absorb a major portion., , 337
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Natural Greenhouse, Effect, , Less, re-emitted heat, , More heat escapes, into space, SUN, , Re-radiated heat, , Human Enhanced, Greenhouse Effect, Less heat escapes, into space, SUN, , Re-radiated heat, , Fig. 15.10 : Greenhouse effect, The molecules of these gases radiate heat, This rise in temperature leads to, energy and a major part of it comes back to unfavourable changes in environment and, earth’s surface. Thus reheating the earth. This resulting in odd climatic changes.(eg; EI, cycle is repeated many times. Hence CO2 and Nino effect). EI Nino effect results in melting, CH4 are commonly called greenhouse gases., of polar ice caps and Himalayan snow caps, The atmosphere around the earth acts as which may be the cause for submerging of the, glass wall of a greenhouse. It absorbs solar coastal areas., radiations from the sun and radiates it to, earth. Atmosphere prevents infrared radiations, emitted by the earth to escape into the space., Gases responsible for this effect are, carbon di-oxide (CO ), Methane, (CH ), 2, 4 ,, chloroflorocarbons (CFC), Nitrous oxide (N2O), and water vapours., Because of burning of fossil fuels in, industries, by automobiles, burning of, agricultural wastes, levels of CO2 are increasing., Biogas plants, paddy fields, cattle sheds add, methane to atmosphere. Chloroflorocarbons, are emitted by fire extinguishers and air, conditioners., Global warming :, Increase in atmospheric concentration of, green house gases, has resulted in the heating, of Earth or rise in the temperature. During, past century, the temperature of the Earth has, increased by 0.60C, most of it during last three, decades., 338, , Do you know ?, In order to overcome the problem, of global warming, Chewang Norphel, Ice, Man of India has built 13 artificial glaciers., He is an Indian civil engineer from Ladakh., Norphel noticed a small stream had, frozen solid, under the shade of a group of, poplar trees, though it flowed freely elsewhere, in his yard., The reason for this phenomenon :, The flowing water was moving, quickly to freeze while the sluggish trickle, of water beneath the trees, was slow enough, to freeze. Based on this, he created artificial, glaciers by diverting a river into a valley,, slowing the stream by constructing checks., The artificial glaciers increase the, ground water recharge, rejuvenating the, spring and providing water for irrigation., He constructed them at lower elevations, so, that they melt earlier expanding the growing, season.
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Global warming can be controlled by, reducing use of fossil fuel, improving efficiency, of energy usage, reducing deforestation,, planting trees and checking of human, population growth., Do you know ?, El Nino effect is a climate cycle in, pacific ocean with global impact on weather, pattern. The cycle begins when warm water, in the western tropical pacific ocean shifts, eastwards along the equator towards the, coast of America. Normally, this warm water, pools near Indonesia and Philippines., La Nina is a climatic pattern that, describes the cooling of surface ocean, waters along the tropical west coast of south, America., 15.9 Ozone depletion :, Ozone is a form of oxygen.In the, stratosphere, ozone is photo-dissociated and is, generated by absorption of short wave length, UV radiations., O3 → O2 +[O], O + [O] → UV RAYS → O, 2, , 3, , Generation and dissociation of ozone are in, equilibrium leading to steady concentration of, ozone in the stratosphere (12 to 15 kilometers, from Earth’s surface in the atmosphere)., This ozone layer acts as shield that absorbs, UV radiations from the sun and protects, all types of life on earth. Absorption of UV, radiations by ozone blanket is proportional, to its thickness. Thickness is more above the, poles than at the equator. UV rays are highly, injurious to living organisms since DNA and, proteins of living organisms absorb UV rays, and its high energy breaks the chemical bonds, within these molecules., Thickness of the ozone in a column of air, from the ground to the top of the atmosphere is, measured as Dobson units (DU)., , The ozone shield has been disturbed due, to increased rate of ozone degradation by, Chlorofluorocarbon (CFC). CFCs move, upwards and reach stratosphere. UV rays act on, them and release Cl atoms. Cl degrades ozone, releasing molecular oxygen. Cl atoms act as, catalyst. So they remain in the stratosphere and, continue the effect of ozone degradation. This, results in ozone depletion. Although it occurs, widely in the stratosphere, the depletion is, particularly marked over the Antarctic region., This has resulted in formation of large area of, thinned ozone layer, commonly called ozone, hole., UV radiations of wave length shorter than, UV-B i.e. 100-280nm are almost completely, absorbed by earth’s atmosphere, given that, the ozone layer is intact. UV-B (wavelength, 280-322nm) damages DNA and mutation, may occur. It causes aging of skin, damage to, skin cells and various types of skin cancers. In, human eye, cornea absorbs UV-B radiations, and a high dose of UV-B causes inflammation, of cornea called snow blindness, cataract, etc; Such exposure may permanently damage, cornea., Recognising the harmful effects of ozone, depletion, an international treaty, known as the, Montreal Protocol was signed at Montreal, (Canada) in 1987 to control emission of ozone, depleting substances., Later many more efforts have been made, and protocols have laid down definite roadmaps, separately for developing and developed, countries for reducing emission of CFCs and, other ozone depleting chemicals., , 339, , Can you tell?, 1. How pollution by domestic garbage can, be controlled?, 2. Give effect of CFC on ozone shield., 3. Give an account of possible effects of, global warming., 4. Plastic ban in Maharashtra is an essential, step. Give reason.
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Internet my friend, 1. Find out more about artificial glaciers., 2. Collect information about colour code, used for biomedical waste., 15.10 Deforestation :, Deforestation is conversion of forest area, into non-forest area. According to an estimate,, almost 40% forests are lost in the tropics and, only 1% in temperate region. The scenario of, deforestation is grim in India. At the beginning, of 20th century, forest cover was about 30% in, India. By the end of the century, it got reduced, to 19.4 %. The National Forest Policy 1988 of, India has recommended 33% forest cover for, the plains and 67% for the hills., Deforestation takes place by conversion, of forest to agricultural land so as to feed the, growing human population.Trees are cut for, timber, firewood, for keeping cattle in farm and, for other purposes., Slash and burn agriculture commonly, called Jhum Cultivation in north eastern, parts of India, where farmers cut down trees, of the forest and burn the plant remains. The, ash is used as fertilizer and the land is used for, farming and cattle grazing. After cultivation,, the area is left for several years so as to allow, its recovery., Major Effect of Deforestation is, the increased concentration of CO2 in the, atmosphere because trees hold lot of carbon in, their biomass, are lost with deforestation., It leads to the loss of biodiversity due to, habitat destruction, disturbs hydrologic cycle,, causes soil erosion and desertification in, extreme cases., Can you tell?, 1. How Jhum cultication has led to, deforestation in recent years?, 2. Comment on deforestation status of the, world and its major effects., , Reforestation is the process of restoring a, forest that once existed but was distroyed or, removed at some time in past. Reforestation, occurs naturally in a deforested area. We, can speed up this by plantation of tree with, due consideration to biodiversity that existed, before., Best example of peoples participation, in reforestation is Saalumara Thimmakka,, an Indian environmentalist from state of, Karnataka noted for her work in planting, and tending to 385 banyan trees along a 4km, stretch of highway between Hulikal and Kudur., She has also planted nearly 8000 other trees., Her work has been honoured with the National, Citizens Award of India. She was also conferred, with Padma Shri in 2019., Moirangthem Loiya from Manipur, dedicated 17 years of his life to restore, Punshilok forest. He left his job and took over, the task of bringing back the lost glory of, 300 acres forest land. He planted a variety of, trees like, bamboo, oak, ficus, teak, jackfruit, and magnolia. Today the forest has over 250, varieties of plants including 25 varieties of, bamboo. It is now selected as home by great, diversity of animals too., Can you recall?, What is Chipko movement?, Case study of people’s participation in, conservation of forests., History of people’s participation in India, can be traced back to 1731. The ministers of, the king of Jodhpur in Rajasthan tried to cut, forest to procure wood for a new palace. Local, Bishnoi community known for peaceful coexistence with nature, opposed king’s men., A Bishnoi woman Amrita Devi hugged, the trees and lost her life in an attempt for, protecting the forest. Her three daughters and, hundreds of other Bishnois too lost their lives., , 340
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The Government of India has recently instituted, Amrita Devi Bishnoi Wildlife protection, Award for individuals or community from, rural areas that have shown extraordinary, courage and dedication in protecting wildlife., In 1980s, realising the significance, of participation of local communities,, Government of India introduced the concept, of Joint Forest Management (JFM) so as, to work closely with local communities for, protecting and managing forests. In return, for, their services to the forest, the communities get, benefit of various forest products (Fruits, gum,, rubber, medicine etc.) and thus the forest can be, conserved in a sustainable manner., 15.11 Mission Harit Maharashtra :, An ambitious project of planting 50, crore trees in four years was taken up by, Government of Maharashtra in the year 2016., Under this project yearly targets were given, to each district. The plantation drive is in line, with National Forest Policy (NFP) which aims, at maintaining 33% forest cover in the country., A 24-hour toll free helpline number 1926, called ‘Hello Forest’ has been set up to provide, information regarding plantation, protection, and for mass awareness., , The Forest Department has created a, mobile application called ‘My Plants’ to record, details of the plantation such as numbers,, species and location. Authorities are expected, to take care of saplings in the first year i.e.,, year 2016, 2.87 crore saplings were planted., In 2017, 5.17 crore and in 2018, 15.17crore, plantation count was achieved! In the year, 2019, the government aimed at a phenomenal, 33 crore sapling plantation which was launched, at Anandwan, Warora., The government has decided to adapt, Japanese Miyawaki method of plantation, for this project. State Forest Department and, Social Forestry Department have run successful, pilot plantation programmes using Miyawaki, pattern in various districts like, Beed, Hingoli,, Pune, Jalgaon, Aurangabad etc., Use your brain power, Floods in Sangli and Kolhapur in, August 2019, were responsible for many, problems during and after the floods. Think, and enlist different types of problems faced, by flood affected areas., , Activity :, Complete the following chart :, All species, Evaluated, Adequate data, Threatened categories, , NE, , Not, Evaluated, , DD, , LC, , NT, , VU, , EN, , Near, Endangered, Threatened, Increasing risk of extinction, , 341, , CR, , EW, , EX, , Extinct in, the wild, , Extinct
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Exercise, Q. 1 Choose the correct option, 1. Observe the graph and select correct, option., A, , Saecies richness, , B, , Area, , a. Line A represents, S=CA2, b. Line B represents, log C= log A +, Z log S, c. Line A represents, S=CAZ, d. Line B represents, log S= log Z + C, log A, 2. Select odd one out on the basis of Ex, situ conservation., a. Zoological park, b. Tissue culture, c. Sacred groves, d. Cryopreservation, 3. Which of the following factors will, favour species diversity?, a. Invasive species b. Glaciation, c. Forest canopy, d. co extinction, 4. The term “terror of Bengal’ is used for, ., a. algal bloom, b. water hyacinth, c. increased BOD d. eutrophication, 5. CFC are air polluting agents which are, produced by, ., a. Diesel trucks, b. Jet planes, c. Rice fields, d. Industries, , protection of endangered species., 3. Where was ozone hole discovered?, 4. Give one example of natural pollutant., 5. What do you understand by EW category, of living being?, Q. 3 Short answer type questions., 1. Dandiya raas is not allowed after 10.00, pm. Why?, 2. Tropical regions exhibit species richness, as compared to polar regions. Justify., 3. How does genetic diversity affect, sustenance of a species?, 4. Green house effect is boon or bane?, Give your opinion., 5. How does CO cause giddiness and, exhaustion?, 6. Name two types of particulate pollutants, found in air. Add a note on ill effects of, the same on human health., Q. 4 Long answer type questions., 1. Montreal protocol is an essential step., Why is it so?, 2. Name any 2 personalities who have, contributed to control deforestation in, our country. Elaborate on importance of, their work., 3. How BS emission standards changed, over time? Why is it essential?, 4. During large public gatherings like, Pandharpur vari mobile toilets are, deployed by the government. Explain, how this organic waste is disposed., 5. How Indian culture and traditions, helped in bio-diversity conservation?, Give importance of conservation in, terms of utilitarian reasons., Project : Find out at least 2 plant and animal, varieties native to Maharashtra which are, endangered. Find out their IUCN status and, reasons for the same. Suggest conservation, measures., , Q. 2 Very short answer type questions., 1. Give two examples of biodegradable, materials released from sugar industry., 2. Name any 2 modern techniques of, 342
