THE WISDOM ACADEMY FOR CIVIL SERVICES YOUR SUCCESS,YOUR WAY,TO BUILD A NATION

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2 Page2 Dear students, DIRECTOR S MESSAGE NCERT forms an important base for preparation of civil services. Aspirants need to understand these books which are basic in nature. Student should be thorough with this books conceptually and well versed with the facts. There are number of subject like HISTORY, GEOGRAPHY, and POLITY. whose NCERT needs to be covered. Timely revision and re-reading becomes a challenging task for aspirant. Wisdom academy has come up with a solution by proving aspirant for comprehensive GIST with solved questions below the chapter. The purpose of providing these short summary notes is to travel with the aspirant in achieving their dream in competitive exam. ALL THE BEST!!!!

3 Page3 INDEX REPRODUCTION Chapter 1 : Reproduction in Organisms Chapter 2 : Sexual Reproduction in Flowering Plants Chapter 3 : Human Reproduction Chapter 4 : Reproductive Health UNIT VII : GENETICS AND EVOLUTION Chapter 5 : Principles of Inheritance and Variation Chapter 6 : Molecular Basis of Inheritance Chapter 7 : Evolution UNIT VIII : BIOLOGY IN HUMAN WELFARE Chapter 8 : Human Health and Disease Chapter 9 : Strategies for Enhancement in Food Production Chapter 10 : Microbes in Human Welfare UNIT IX : BIOTECHNOLOGY Chapter 11 : Biotechnology : Principles and Processes Chapter 12 : Biotechnology and its Applications X UNIT X : ECOLOGY Chapter 13 : Organisms and Populations Chapter 14 : Ecosystem Chapter 15 : Biodiversity and Conservation Chapter 16 : Environmental Issues

4 Page4 Asexual Reproduction REPRODUCTION IN ORGANISMS The period through which a certain organism lives is known as its life span. Reproduction is the process by which every organism ensures its continuity. It is the process through which organisms produce young ones, which in turn mature to give rise to their young ones. Reproduction can be: o Asexual Only one individual is involved o Sexual Two individuals (male and female) are involved Asexual Reproduction In this type, a single parent can produce offspring. The produced offspring are clones of each other (i.e., identical to each other and to the parent). It is commonly seen in unicellular organisms belonging to protista and monera. Here, the cell division itself is the mode of reproduction. Means of Asexual Reproduction Binary Fission In this process, the cell divides into halves, and each half develops into an adult (example: Amoeba, Paramecium). Budding In this process, the cell divides unequally to form buds, which remain attached to the parent initially, and then detach and develop into a mature cell (example: yeast). Formation of specialized structures o Conidia (Example: Penicillium) o Gemmules (Example: Sponges) o Buds (Example: Hydra) o Zoospores Microscopic, motile spores (Example: Algae) Vegetative propagation It means of asexual reproduction in plants. Different structures are capable of giving rise to new plants. o Runner (Example: Gladiolus) o Rhizome (Example: Ginger) o Sucker o Tuber (Example: Potato) o Offset o Bulb (Example: Onion) Sexual Reproduction: Pre-Fertilisation Events Sexual reproduction involves the formation of the male and female gametes in either the same individual or two individuals. These gametes fuse to form a zygote, which develops into a new individual. Offspring are not identical to each other or to the parents. So, sexual reproduction gives rise to diversity among living organisms. All organisms pass through two stages. o Juvenile phase Period of growth; non reproductive o Vegetative phase or reproductive phase In non-primate mammals like rats, sheep, dogs, cows and tigers, the cyclic change in the activities of the ovaries and the oviduct is called the oestrus cycle; in primates like monkeys, apes and humans, it is called the menstrual cycle. Certain mammals are called continuous breeders since they can reproduce throughout their reproductive phase, while some are called seasonal breeders since they can reproduce only in the

5 Page5 favourable seasons. Events in Sexual Reproduction Organisms reproducing sexually exhibit certain events. These are: o Pre-fertilisation events o Fertilisation events o Post-fertilisation events Pre-Fertilisation Events Events taking place before the fusion of the gametes Consist of: o Gametogenesis o Gamete transfer Gametogenesis Process of formation of gametes (male and female) Gametes are haploid In some organisms (like algae), they are almost similar (homo or isogametes), and cannot be categorised as male and female gametes. In others, the two gametes are morphologically and physiologically different (heterogametes), and are of two types antherozoid or sperm (male gamete) and egg or ovum (female gamete). In some organisms both the sexes are present in the same individual (monoecious or homothallic), and in others, they are present in two individuals (dioecious or heterothallic). In a unisexual flower, the male flower is called staminate and the female flower is called pistillate. Gamete formation takes place by cell division. In haploid parents, it is by mitosis; in diploid parents, it is by meiosis, with specialised cells called meiocytes undergoing meiosis..gamete Transfer For their fusion to take place, the gametes need to be transferred. In most organisms, the male gametes are motile, while the female gametes are non-motile, and the male gametes need a medium for their movement. A large number of male gametes do not make it to the female gamete, and hence, several thousands of male gametes are produced to overcome this loss. In angiosperms, the pollen grain carries the male gamete and the ovule carries the female gamete. Pollen grains are produced in the anther and need to be transferred to the stigma for fertilisation to occur. This is easy in monoecious plants as both the anther and the stigma are present close by; in dioecious plants, it takes place by pollination. Sexual Reproduction: Fertilisation Events Fertilisation is the most important event in sexual reproduction. This process is also called syngamy and leads to the formation of the zygote. However, in some organisms, zygote formation takes place without fertilisation, and is known as parthenogenesis (occurs in rotifers, honeybees and some lizards). In most aquatic organisms and amphibians, fertilisation takes place outside their body (in the water), and is termed as external fertilization.their eggs and offspring are highly vulnerable to predators and this threatens their survival up to adulthood. In most terrestrial organisms, fertilisation is internal, i.e., it takes place inside the female body. In this process, the male gamete is motile and reaches the female gamete to fuse with it, thereby forming zygote. Male gametes are produced in large numbers.

6 Page6 Sexual Reproduction: Post-Fertilisation Events Zygote Events taking place after fertilisation are called post-fertilisation events. The haploid gametes fuse to form a diploid zygote in all organisms. In external fertilisation, a zygote is formed in an external medium, and in internal fertilisation, a zygote is formed inside the individual. The development of a zygote depends upon the life cycle of an organism and its surroundings. In some organisms, the zygote does not develop immediately, and develops a thick wall around itself. This wall is resistant to damage and desiccation. Embryogenesis It is the process of development of the embryo from the zygote. The zygote undergoes cell division and differentiation. Cell division increases the number of cells of the embryo, and cell differentiation helps the cells undergo modifications to form specialised tissues and organs. Animals can be grouped into two categories based on how and where the development of the zygote takes place. These categories are: o Oviparous The fertilised egg is covered by a calcareous shell and is released into the outside environment. The development takes place inside the egg and the young one hatches out (example: birds and reptiles). o Viviparous The development of the zygote takes place inside the female body, and the developed young one is delivered outside (example: mammals, including humans). In flowering plants, the zygote is formed inside the ovule. o Zygote Develops into Embryo o Ovule Develops into Seed o Ovary Develops into Fruit Contains Seeds Disperse and germinate to form new plants

7 Page7 SEXUAL REPRODUCTION IN FLOWERING PLANTS Pre-Fertilisation Events Several hormonal and structural changes result in the development of a flower. Inflorescences bear the flower buds, and then the flowers. Flowers are the reproductive parts of a plant. In the flowers, the androecium (male reproductive part) and the gynoecium (female reproductive part) develop. Androecium The androecium consists of whorls of stamen. The stamen consists of the filament (long and slender stalk) and anther (bilobed structure). Filament is attached to the thalamus or to the petal. Anther: o A typical anther is bilobed and each lobe is dithecous (consists of two theca). o Theca are separated by a longitudinal groove running lengthwise. o The microsporangia are located at the corners, two in each theca. They further develop to form pollen sacs, which contain the pollen grains. Structure of microsporangium o The microsporangium is surrounded by four wall layers (epidermis, endothecium, middle layers, and tapetum).

8 Page8 o o The outer three layers are protective and help in dehiscence of anther to release the pollen grains. The tapetum provides nourishment to the developing pollen grains. In the young anther, the sporogenous tissue forms the centre of each microsporangium. Microsporogenesis It is the process of formation of microspore from PMC (Pollen Mother Cells). As development occurs in the anther, the sporogenous tissue undergoes meiosis to form microspore tetrad. Each cell of sporogenous tissue has capacity to give rise to a tetrad. Hence, each cell is a potential pollen or PMC. As the anther matures, the microspores get detached from each other and develop into pollen grains. Pollen grains Represent the male gamete and are spherical, having a two-layered wall: o Exine (outer) Hard layer made of sporopollenin, which is extremely resistant and can withstand high temperatures, acidic and alkaline conditions, and enzymes o Intine (inner) Thin and continuous layer made up of cellulose and pectin Mature pollen grain contains two cells: o Vegetative cell Large with irregular nucleus, contains food reserves o Generative cell Small and floats in the cytoplasm of the vegetative cell In 60% of the angiosperms, pollen grains are shed at 2-celled stage while in others generative cell undergoes mitosis to form two male gametes (3-celled stage). The viability of pollen grains after they are shed depends upon temperature and humidity. It ranges from 30 minutes to few months. Gynoecium and Formation of Female Gametophyte The gynoecium represents the female reproductive part of a flower. It may be mono-carpellary (one pistil) or multi-carpellary (many pistils). In multi-carpellary, the pistils may be fused in one (syncarpous) or free (apocarpous). Each pistil consists of: o Stigma Receives the pollen grains o Style Elongated, slender part below the stigma

9 Page9 o Ovary Bulged basal part containing the placenta, which is located inside the ovarian locule (cavity) o The placenta contains the megasporangia or ovules. Megasporangium The ovule is attached to the placenta by the funicle. The junction of the ovule and the funicle is called hilum. Each ovule has one or two protective layers, called integuments, which cover the rest of the ovule, except for a small opening called micropyle. The chalaza lying on the opposite side of the micropyle end represents the basal part of the ovule. Nucellus is present within the integuments and contains reserved food. The embryo sac or female gametophyte is located within the nucellus. Megasporogenesis The megaspore mother cell (MMC) gets converted into megaspores by the process of megasporogenesis. The MMC is large and contains a dense cytoplasm and a prominent nucleus. It undergoes meiosis to produce four megaspores. Female Gametophyte In most flowering plants, only one megaspore is functional while the other three degenerate. The single functional megaspore develops into the female gametophyte. This kind of development is called monosporic development. The nucleus of the functional megaspore divides mitotically to form 2 nuclei, which move towards the opposite ends, forming a 2-nucleate embryo sac. Two more mitotic divisions ensue, leading to the formation of 4-nucleate and 8-nucleate embryo sacs.

10 Page10 After the 8-nucleate stage, the cell walls are laid down and the typical female gametophyte (embryo sac) gets organised. Six of the 8-nuclei get surrounded by the cell wall and the remaining two, called polar nuclei, are situated below the egg apparatus in the large central cell. Three of the six cells are placed at the micropylar end and constitute the egg apparatus (2 synergids + 1 egg cell). The synergids have special thickenings at the micropylar end. These are together called the filiform apparatus. It helps in leading the pollen tubes into the synergids. Three cells are at the chalazal end, and are called antipodal cells. A typical angiosperm female gametophyte is 7-celled and 8-nucleated at maturity. Pollination It is the process of transfer of pollen grains from the anther to the stigma. Depending on the source of pollen, pollination can be divided as follows: o Autogamy It is the transfer of pollen grains from the anther to the stigma of the same flower. Autogamy requires the anther and the stigma to lie close. It also requires synchrony in the pollen release and stigma receptivity. Plants like Viola, Oxalis, etc., produce two kinds of flowers chasmogamous flowers (with exposed anther and stigma) and cleistogamous flowers (which do not open at all and only autogamy occurs). o Geitonogamy It is the transfer of pollens from the anther of one flower to the stigma of another flower in the same plant. Genetically, it is similar to autogamy, but it requires pollinating agents. o Xenogamy It is the transfer of pollen grains from the anther to the stigma of a different plant. Pollination causes genetically different types of pollens to be brought to a plant. Agents of Pollination Plants use air, water (abiotic agents) and animals (biotic agents) for pollination. Pollination by wind o It is the most common form of abiotic pollination. o Plants possess well-exposed stamens and large, feathery stigma. o Pollens should be light and non-sticky to be carried easily by winds. o Wind-pollinated flowers often have single ovule in the ovary and numerous flowers packed in an inflorescence. o It is common in grass. Pollination by water o It is rare in flowering plants, except for some aquatic plants like Vallisneria and Hydrilla. o In most water-pollinated plants, the pollen grains are long and ribbon-like, and are protected from wetting by mucilaginous covering. o In a majority of water plants like water hyacinth and water lily, flowers emerge above the water level and are pollinated by insects.

11 Page11 Pollination by animals o Majority of flowering plants use butterflies, bees, wasps etc., for pollination. o Most of the insect-pollinated flowers are large, colourful, fragrant, and contain nectar to attract the animal pollinators. These are called floral rewards. o Floral reward can be in the form of providing safe places to lay eggs (example: the tallest flower, Amorphophallus) o A symbiotic relationship exists between the plant, Yucca and its pollinator moth. The moth is dependent on the plant since the moth deposits its eggs in the locule of the ovary of the plant, and in return, the plant is pollinated by the moth. o The pollen grains are sticky and get stuck to the body of the pollinator. Out Breeding Devices Repeated self pollination leads to inbreeding depression. Plants have developed methods to prevent self pollination. Autogamy is prevented by following ways: o Pollen release and stigma receptivity not coordinated o Different positioning of the anther and the stigma o Production of unisexual flowers Ways to prevent both autogamy and geitonogamy: o Presence of male and female flowers on different plants, such that each plant is either male or female (dioecy). o This mechanism is present in several species of papaya. Pollen Pistil Interactions Pollination does not always ensure the transfer of compatible pollens. Hence, the pistil has the ability to recognise the right type of pollen to promote post- pollination events. If the pollen is of the wrong type, the pistil prevents pollen germination. This interaction is mediated by chemical components of the pollen and the pistil. Pollen pistil interaction is a dynamic process involving pollen recognition, followed by promotion or inhibition of the pollen. The pollen tube reaches the ovary and enters the ovule through the micropyle. Then, through the filiform apparatus, it reaches synergids. In this way, the pollen tube grows. Artificial Hybridisation & Double Fertilisation Artificial Hybridisation It is a method to improve crop yield. In this method, it is essential to ensure that the right kinds of pollen grains are used, and the stigma is protected from unwanted pollen grains. It is achieved by: o Emasculation The anther is removed from the bud if the female parent bears bisexual flowers. o Bagging The emasculated flower is covered by a bag so as not to allow contamination of the stigma by unwanted pollen grains. When the stigma of the bagged flower becomes receptive, the collected pollen grains are dusted onto the stigma, and then the flower is rebagged. If the female parent is unisexual, emasculation is not necessary. In this case, the female bud is directly bagged, and when the stigma turns receptive, suitable pollen grains are dusted onto it so as to allow germination. Double Fertilisation When the pollen grains fall on the stigma, the pollen tube enters one of the synergids and releases two male gametes. One of the male gametes moves towards the egg cell and fuses with it to complete the syngamy to form the zygote. The other male gamete fuses with the two polar nuclei and forms triploid primary endosperm nucleus (PEN). This is termed as triple fusion.

12 Page12 Since two kinds of fusion syngamy and triple fusion take place, the process is known as double fertilisation, and is characteristic of flowering plants. After triple fusion, the central cell becomes the primary endosperm cell (PEC). The primary endosperm nucleus gives rise to the endosperm, while the zygote develops into the embryo. Post-Fertilisation Events It includes development of endosperm and embryo, and maturation of ovules into seeds and ovaries into fruits. Formation of Endosperm The endosperm develops before the embryo because the cells of the endosperm provide nutrition to the developing embryo. The primary endosperm nucleus repeatedly divides to give rise to free nuclei. This stage of development is called free nuclear endosperm. Cell wall formation occurs next, resulting in a cellular endosperm. The endosperm may be either fully consumed by the growing embryo (as in pea and beans) or retained in the mature seed (as in coconut and castor). Development of Embryo The embryo develops at the micropylar end of the embryo sac where the zygote is situated. The zygote gives rise first to the pro-embryo, and then to the globular, heart-shaped, mature embryo. A typical dicot embryo consists of an embryonal axis and two cotyledons. The portion of the embryonal axis above the level of cotyledons is called epicotyl. It contains the plumule (shoot tip). The portion below the axis is called hypocotyl. It contains the radicle (root tip). The root tip is covered by the root cap.

13 Page13 In a monocot embryo, there is only one cotyledon. In grass, it is known as the scutellum, and is situated at one side of the embryonal axis. At its lower end, the embryonal axis has the radicle and the root cap enclosed in the coleorrhiza. The epicotyl lies above the level of the scutellum, and has the shoot apex and leaf primordia enclosed in hollow structures called coleoptiles. Seeds and Fruits Development of Seeds It is the last stage of sexual reproduction in angiosperms. Seeds are the fertilised ovules that are developed inside a fruit. A seed consists of: o Seed coat o Cotyledons o Embryonal axis Seeds may be albuminous (endosperm present; as in wheat and maize) or non-albuminous (endosperm absent; since it is consumed by the growing embryo; as in pea and beans). Some seeds such as black pepper and wheat have remnants of nucellus known as perisperm. The integuments of ovules harden to form the seed coat, and the micropyle facilitates the entry of oxygen and water into the seed. As it loses moisture, the seed may enter dormancy, or if favourable conditions exist, it germinates. Development of Fruits The ovary of a flower develops into a fruit. The walls of the ovary transform into the walls of the fruit (pericarp). Fruits may be fleshy, as in mango and orange, or can be dry, as in groundnut and mustard. In some plants, floral parts other than the ovary take part in fruit formation, as in apple and strawberry. In these, the thalamus contributes to fruit formation. Such fruits are called false fruits. Fruits that develop from the ovary are called true fruits. Some fruits develop without fertilisation, and are known as parthenocarpic fruits (example: banana). Apomixis and Polyembryony Some plants produce seeds without fertilisation. This process of seed formation is known as apomixis. Apomixis is a form of asexual reproduction mimicking sexual reproduction. In some species, apomixis occurs as the diploid egg cell is formed without meiosis, and develops into embryo without fertilisation.

14 Page14 In some varieties of citrus and mango, the nucellus cells divide and protrude into the embryo sac to develop into embryos. In such cases, each ovule may contain several embryos and this condition is called polyembryony. Apomixis is important for producing hybrid varieties of fruits and vegetables, and also for increasing crop yield multifold.

15 Page15 HUMAN REPRODUCTION Male and Female Reproductive Systems Human beings reproduce sexually and are viviparous. In humans, the reproductive phase starts after puberty. It involves: o Gametogenesis o Insemination o Fertilisation o Implantation o Gestation o Parturition The Male Reproductive System Testes It is located in the pelvic region. It consists of: o A pair of testes o Accessory glands and ducts o External genitalia Situated within the scrotum, which protects the testes and also helps in maintaining the temperature. Each testis is 4 to 5 cm in length, and 2 to 3 cm in width, and has about 250 compartments called testicular lobules. Testicular lobules have seminiferous tubules which are the sites of sperm formation. Seminiferous tubules are lined by two types of cells: o Male germ cells They undergo meiosis to form sperms. o Sertoli cells They provide nourishment to the germ cells. Region outside the seminiferous tubules is called the interstitial space, which contains Leydig cells (interstitial cells). The Leydig cells produce androgens. Accessory Ducts and Glands Accessory ducts include: o Rete testis o Vasa efferentia o Epididymis o Vas deferens The seminiferous tubules open into the vasa efferentia through the rete testis. The vasa efferentia open into the epididymis, which leads to the vas deferens. The vas deferens opens into the urethra along with a duct from the seminal vesicle called the ejaculatory duct.

16 Page16 The ejaculatory duct stores the sperms and transports them to the outside The urethra starts from the urinary bladder, extends through the penis and opens via the urethral meatus. Accessory glands include: o A pair of seminal vesicles o Prostate gland o A pair of bulbourethral glands The secretions of these glands make up the seminal plasma, and provide nutrition and a medium of motility to the sperms. The Female Reproductive System It is located in the pelvic region: It includes: o A pair of ovaries o A pair of oviducts o Uterus o Cervix o Vagina o External genitalia o Mammary glands (not part of the reproductive system, but aids in child care) Ovaries They are the primary female sex organs. They produce the ovum and other ovarian hormones. They are located in the lower abdomen, and are 2 to 4 cm in length. They are connected by ligaments to the pelvic walls and to the uterus. Each ovary is covered by epithelium, and contains the ovarian stroma. The ovarian stroma is made up of: o Peripheral cortex o Inner medulla Oviducts They are also called fallopian tubes. They are 10 to 12 cm long, and extend from the ovary to the uterus. The part of each oviduct lying towards the ovary is funnel shaped, and is called infundibulum. It has fingerlike projections called fimbriae. The infundibulum leads to the ampulla, and then to the isthmus, which has a narrow lumen opening into the uterus.

17 Page17 Uterus It is also called womb, and is pear shaped. It is connected to the pelvic walls by ligaments. The uterine wall consists of: o External perimetrium o Middle myometrium o Internal endometrium, which lines the uterine cavity The endometrium undergoes changes during the menstrual cycle. Cervix and Vagina The cervix connects the uterus to the vagina. The cervix and the vagina constitute the birth canal. External Genitalia Consists of: o Mons pubis Fatty tissue covered by skin and pubic hair o Labia majora Extends from mons pubis and surrounds the vaginal opening o Labia minora Fold of skin beneath the labia majora o Hymen Partially covers the vaginal opening o Clitoris Lies at the junction of labia minora Mammary Glands Present in all female mammals It is paired and is glandular. Each breast contains 15 to 20 mammary lobes with alveoli which secrete milk. The alveoli open into the mammary tubules, which unite to form a mammary duct. Many mammary ducts constitute the mammary ampulla, which is connected to the lactiferous duct. Gametogenesis The testis and ovary produce the male and female gametes respectively by gametogenesis (spermatogenesis in males and oogenesis in females). Spermatogenesis

18 Page18 In males, sperms are produced by the spermatogonia (immature germ cells), which are present in the inner walls of the seminiferous tubules. Spermatogonia increase in number by mitosis. These are diploid. Some of the spermatogonia called primary spermatocytes periodically undergo meiosis. After the first meiotic division, two haploid and equal secondary spermatocytes are formed. These further undergo meiosis to give rise to four haploid spermatids. These spermatids are converted into sperms by spermiogenesis. The sperm head gets embedded in the Sertoli cells after spermiogenesis and is released from the seminiferous tubules by spermiation. Spermatogenesis starts at puberty by the action of the gonadotropin releasing hormone (GnRH), which in turn causes the release of two gonadotropins called Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH). LH acts on Leydig cells and causes them to release androgens, which stimulate the process of spermatogenesis while the FSH acts on the Sertoli cells, which help in spermiogenesis. Structure of a Sperm Oogenesis A mature sperm consists of: o Head o Neck o Middle piece o Tail The whole sperm is enclosed in a plasma membrane. The head consists of a haploid nucleus and a cap-like acrosome, which contains enzymes that aid in fertilisation. The middle piece contains several mitochondria, which produce energy for the motility of the sperm. Sperms released by the seminiferous tubules are transported by the accessory ducts. Secretions of epididymis, vas deferens, seminal vesicles, and prostate are essential for maturation and motility of sperms. The ovum is formed by the process of oogenesis.

19 Page19 It starts during embryonic growth and millions of gamete mother cells (oogonia) are formed in the foetal ovary. These cells undergo meiosis, but get temporarily arrested at the prophase and are called primary oocytes. Before reaching puberty, a large number of primary oocytes degenerate and the remaining ones get surrounded by layers of granulosa cells and new theca and are called secondary follicles. The secondary follicles are then converted into tertiary follicles that have characteristic fluid-filled cavity called antrum. At this stage, the primary oocyte present within the tertiary follicle completes meiosis, which results in the formation of haploid secondary oocyte and a tiny polar body. This tertiary follicle further changes into the Graafian follicle. The secondary oocyte is surrounded by the zone pellucida. Then the Graafian follicle ruptures to release the ovum by ovulation. Menstrual Cycle & Fertilisation

20 Page20 Menstrual cycle is the reproductive cycle in all primates and begins at puberty (menarche). In human females, menstruation occurs once in 28 to 29 days. The cycle of events starting from one menstruation till the next one is called the menstrual cycle. During the middle of the menstrual cycle, one ovum is released (ovulation). The cycle starts with the menstrual flow (3 to 5 days), caused due to the breakdown of the endometrium of the uterus. Blood vessels in liquid state are discharged, but this occurs only when the ovum is not fertilised. It is followed by the follicular phase.in this phase, the primary follicles mature into the Graffian follicles. This causes the regeneration of the endometrium. These changes are brought about by ovarian and pituitary hormones. In this phase, the release of gonadotropins (LH and FSH) increases. This causes follicular growth and the growing follicles produce oestrogen. The LH and FSH are at their peak in the middle of the cycle (14 th day), and cause the rupture of the Graffian follicles to release ovum. This phase is called the ovulatory phase. The remains of the Graffian follicles get converted into the corpus luteum, which secretes progesterone for the maintenance of the endometrium. In the absence of fertilisation, the corpus luteum degenerates, thereby causing the disintegration of the endometrium and the start of a new cycle. In humans, the menstrual cycle ceases to operate at the age of 50 years. This phase is known as the menopause. Fertilisation and Implantation During coitus, the semen is released into the vagina, passes through the cervix of the uterus and reaches the ampullary-isthmic junction of the fallopian tube. The ovum is also released into the junction for fertilisation to occur. The process of fusion of the sperm and the ovum is known as fertilisation. During fertilisation, the sperm induces changes in the zona pellucida and blocks the entry of other sperms. This ensures that only one sperm fertilises an ovum. The enzymatic secretions of the acrosomes help the sperm enter the cytoplasm of the ovum. This causes the completion of meiotic division of the secondary oocyte, resulting in the formation of a haploid ovum (ootid) and a secondary polar body. Then, the haploid sperm nucleus fuses with the haploid nucleus of the ovum to form a diploid zygote. Mitosis starts as the zygote moves through the isthmus of the oviduct (cleavage) and forms 2, 4, 8, 16 daughter cells called blastomeres. The 8 16 cell embryo is called a morula, which continues to divide to form the blastocyst. The morula moves further into the uterus. The cells in the blastocyst are arranged into an outer trophoblast and an inner cell mass. The trophoblast gets attached to the uterine endometrium, and the process is called implantation. This leads to pregnancy. The inner cell mass gets differentiated to form the embryo. Pregnancy, Parturition and Lactation Pregnancy After implantation, the trophoblast forms finger-like projections called chorionic villi, surrounded by the uterine tissue and maternal blood. The chorionic villi and the uterine tissue get integrated to form the placenta, which helps in supplying the developing embryo with oxygen and nutrients, and is also involved in the removal of wastes. The placenta is connected to the embryo by the umbilical cord. The placenta acts as an endocrine gland, and produces the human chorionic gonadotropins, human placental lactogen, oestrogen, progesterone and relaxin (later stages of pregnancy). These hormones support foetal growth and help in the maintenance of pregnancy. Hormones like oestrogen, progestogen, cortisol, prolactin, etc., are increased several folds in the maternal blood.

21 Page21 Immediately after implantation, the inner cell mass (embryo) gets differentiated into the ectoderm, mesoderm and endoderm, which give rise to the different tissues. This ability of the inner cell mass is due to the presence of multi-potent cells called stem cells. Most of the major organs are formed at the end of 12 weeks of pregnancy; during the 5 th month, the limbs and body hair are formed; by the 24 th week, the eyelids separate and eyelashes are formed. At the end of nine months, the foetus is fully formed. Parturition and Lactation Human pregnancy has the duration of 9 months. This duration is called the gestation period. At the end of this period, vigorous uterine contractions lead to the delivery of the foetus. This process is called parturition. Parturition is a neuro-endocrine mechanism, and is started by the signals from the developed foetus and the placenta, which produce the foetal ejection reflex. This causes the release of oxytocin from the pituitary, which causes stronger uterine contractions. This leads to the expulsion of the baby along with the placenta. During pregnancy, the mammary glands undergo differentiation, and milk is produced during the end of pregnancy. The milk produced during the first few days of lactation is known as colostrums.it contains several antibodies that aid the newborn to develop resistance.

22 Page22 REPRODUCTIVE HEALTH Reproductive Health It is defined as the total well being in all aspects of reproduction. India as a country ensures reproductive health to all, and since 1951, successive governments have introduced a number of programmes to ensure this, e.g., family planning and RCH (Reproductive and Child Healthcare) programmes. The aim of these programmes is to create awareness among people about the various aspects of reproductive health. Several audio-visual aids and pamphlets have been developed by both governmental and non-governmental organisations. Awareness is being created among school children by introducing sex education in schools. It is essential to provide medical assistance to people with problems related to STDs, pregnancy, contraception and infertility, especially in villages. Amniocentesis (foetal sex determination based on chromosomal pattern) has been banned to check female foeticide. Population Explosion Birth Control Improvement in the quality of life due to all-round development (better health facilities and improved conditions of living) has lead to a large increase in the world population (around 1 billion in the year 2000). The causes of population explosion are: o Decline in death rate (including maternal mortality rate and infant mortality rate) o Increase in the number of people in the reproducible age Population explosion causes a scarcity of every basic need. Therefore, it has become essential to check this increase in population. One-child norm, increasing the marriageable age and promoting contraceptive methods are some of the ways to check population explosion. It is essential to ensure birth control to check population explosion. Successive governments have come out with various programmes that encourage smaller families by means of various contraceptive methods. Contraceptive methods are of two types: o Natural means of contraception o Artificial means of contraception Natural Methods Avoiding the coming together of ovum and sperm o Periodic abstinence:avoiding coitus from days 10 to 17 of the menstrual cycle o Coitus interruptus: Withdrawal of penis before ejaculation o Lactational amenorrhea: It is the absence of menstruation during lactation. So, in the lactation period, the chances of conception are almost zero. Artificial Methods Physically preventing the coming together of ovum and sperm o Barriers: Include condoms, diaphragms, cervical caps and vaults o Intra uterine devices (IUDs): They release hormones to cause phagocytosis of sperms, or they release copper ions to decrease sperm motility. o Oral contraceptive pills: They contain hormones either progesterone or progesterone oestrogen combination. o Surgical methods: Include vasectomy (removal of a part of the vas deferens in males) and tubectomy (removal of a part of the fallopian tubes in females) Medical Termination of Pregnancy & Sexually Transmitted Diseases Medical Termination of Pregnancy (MTP)

23 Page23 Intentional or voluntary termination of pregnancy before the full term Also called induced abortion Has a role in decreasing population; becomes essential when continued pregnancy may prove to be fatal to the mother, foetus or to both In India, MTP is legal, but with certain strict conditions so as to prevent female foeticide. But in some places, MTP is used with amniocentesis, and when the foetus is female, it is aborted. Such practices can prove to be fatal to the mother as well. Sexually Transmitted Diseases (STDs) Diseases which are transmitted sexually are called STDs. Also called venereal diseases (VD) or reproductive tract infections (RTI) Some of the STDs are: o Gonorrhoea o Syphilis o Chlamydiasis o Genital herpes o Genital warts o Trichomoniasis o Hepatitis-B o AIDS (can also be transmitted by sharing injection needles or surgical instruments, blood transfusion, and from the infected mother to the foetus ) With the exception of AIDS, genital herpes and hepatitis-b, other diseases are curable. When not detected and treated in time, they can lead to pelvic inflammatory diseases, abortions, still births, ectopic pregnancies, infertility and even cancer. Therefore, prevention, and timely detection and cure of these diseases are essential to ensure reproductive health. Some of the preventive measures are: o Avoiding sex with unknown/multiple partners o Use of condoms o To check with a doctor when in doubt Infertility Many couples all over the world are unable to produce children. Some of the reasons for infertility are: o Congenital diseases o Drugs o Immunological and Psychological factors Specialised fertility clinics can help diagnose and treat infertility. The couples can be assisted to have children through techniques called assisted reproductive technologies (ART). Assisted Reproductive Technologies In vitro fertilisation (IVF): Fertilisation takes place outside the body (test tube baby). The following techniques are included in IVF. o ZIFT It stands for zygote intra fallopian transfer. In ZIFT, the sperm from a donor male and the ova from a donor female are fused in the laboratory. The zygote so formed is transferred into the fallopian tube at the 8 blastomeres stage. o IUT It stands for intra uterine transfer. In this technique, embryos with more than 8 blastomeres are transferred into the uterus. o GIFT It stands for gamete intra fallopian transfer. In GIFT, females who cannot produce ovum, but can provide suitable conditions for the fertilisation of ovum, are provided with ovum from a donor. o ICSI It stands for intra cytoplasmic sperm injection. In this method, sperm is directly injected into the cytoplasm of the ovum.

24 Page24 ` o Artificial insemination In this technique, the semen collected from the husband or a donor is injected into the vagina or uterus. This cures the infertility arising from the inability of the male partner to ejaculate, or due to low sperm count.

25 Page25 PRINCIPLES OF INHERITANCE AND VARIATION Genetics Genetics is a branch of biology dealing with inheritance and variation of characters from parents of offspring. Inheritance Process by which characters are passed on from parent to progeny Variation Degree by which the progeny differs from its parents Mendel s Experiments Gregor Johann Mendel known as the father of genetics proposed the laws of inheritance. He used garden pea as his sample. Large sampling size gave credibility to his collected data. Garden pea plant possessed certain completely opposite traits. Example tall and dwarf plants He worked on the following seven traits of garden pea: S. No. Character Dominant Recessive 1 Stem height Tall Dwarf 2 Flower colour Violet White 3 Flower position Axial Terminal 4 Pod shape Inflated Constricted 5 Pod colour Green Yellow 6 Seed shape Round Wrinkled 7 Seed colour Yellow Green True breeding pea lines were obtained by continuous self pollination for several generations. Fourteen true breeding pea lines were selected as pairs, which were similar except for one character with contrasting traits. Artificial cross pollination (hybridisation) was performed on such varieties to obtain first hybrid generation known as the first filial progeny or F 1. Inheritance of One Gene After hybridisation, the F 1 generation so obtained resembled only one of its parents (say, all tall; no dwarf). When 2 plants from F 1 generation were self pollinated, the second filial progeny or F 2 generation was obtained.

26 Page26 Revival of unexpressed trait (dwarf) was observed in some F 2 progeny. Both traits, tall and dwarf, were expressed in F 2 in ratio 3:1. Mendel proposed that something is being passed unchanged from generation to generation. He called these things as factors (presently called genes). Factors contain and carry hereditary information. Alleles Slightly different form of same factor Two alleles code for a pair of two contrasting traits. (e.g., tall and dwarf) Monohybrid Cross Cross that considers only a single character (e.g., height of the part) Studying the cross: o TT, tt, and Tt are genotypes while the traits, tall and dwarf, are phenotypes. o T stands for tall trait while t stands for dwarf trait. o Even if a single T is present in the genotype, phenotype is tall. When T and t are present together, T dominates and suppresses the expression of t. Therefore, T (for tallness) is dominant trait while t (for dwarfness) is recessive trait. o TT and tt are homozygous while Tt is heterozygous. o From the cross, it can be found that alleles of parental pair separate or segregate from each other and only one allele is transmitted to the gamete. o Gametes of TT will have only T alleles; gametes of tt will have only t alleles, but gametes of Tt will have both T and t alleles. Punnett square o Graphical representation to calculate the probability of all possible genotypes of offsprings in a genetic cross o Possible gametes are written on two sides, usually at top row and left columns, and combinations are represented in boxes.

27 Page27 o With the help of Punnet square, genotypic ratio in F 2 generation can be found. From the above given Punnet square, it is evident that genotypic ratio TT: Tt: tt is 1:2:1. o The ratio 1:2:1 or of TT: Tt: tt can be derived from binomial expression (ax + by) 2. o Gamete-bearing genes are in equal frequency of. o Hence, the expression can be expanded as Law of Dominance, Test Cross, Law of Segregation & Incomplete Dominance Mendel s Laws of Inheritance Based on his experiments, Mendel proposed three laws or principles of inheritance: o Law of Dominance o Law of Segregation o Law of Independent Assortment Law of dominance and law of segregation are based on monohybrid cross while law of independent assortment is based on dihybrid cross. Law of Dominance Test Cross According to this law, characters are controlled by discrete units called factors, which occur in pairs with one member of the pair dominating over the other in a dissimilar pair. This law explains expression of only one of the parental character in F 1 generation and expression of both in F 2 generation. Cross between F 2 progeny and its homozygous recessive parent This cross determines whether the dominant character is coming from homozygous dominant genotype or heterozygous genotype. (e.g., tallness coming from TT or Tt) When TT is crossed with tt, we obtain all Tt (tall) individuals in the progeny. Whereas when Tt is crossed with tt, we obtain Tt (tall) and tt (dwarf) individuals in the progeny. Therefore, if tallness is coming from TT, then we obtain all tall progenies in test cross. We obtain both tall and dwarf varieties in test cross, if tallness is coming from Tt.

28 Page28 Law of Segregation This law states that the two alleles of a pair segregate or separate during gamete formation such that a gamete receives only one of the two factors. In homozygous parents, all gametes produced are similar; while in heterozygous parents, two kinds of gametes are produced in equal proportions. Incomplete Dominance In incomplete dominance, F 1 generation has a phenotype that does not resemble either of the two parents, but is a mixture of the two. Example Flower colour in dog flower (snapdragon), where: o RR Red flowers o rr White flowers o Rr Pink flowers Here, genotypic ratio remains same as in Mendelian crosses, but phenotypic ratio changes since complete dominance is not shown by R (hence, incomplete dominance).

29 Page29 Phenotypic Ratio 1:2:1 that denotes Red: Pink: White Genotypic Ratio 1:2:1 that denotes RR: Rr: rr What is Dominance? A diploid organism produces two copies of a gene, which need not be identical and may have minor alterations. Suppose a normal gene produces a product P. Then, the altered version of it must produce a non-functional product P or no product at all. The altered version of the gene must not perform the functions that a normal gene performs. It must affect the phenotype. The original gene is said to be dominant while the modified gene is recessive. Law of Segregation and Co-dominance Co-dominance In co-dominance, the F 1 progeny resembles both the parents. Example: ABO blood groups in human beings ABO blood groups are controlled by gene I. Gene I has three alleles, I A, I B and i. A person possesses any two of the three alleles. I A and I B dominate over i. But with each other, I A and I B are co-dominant. I A and I B contain A and B types of sugar, while i does not contain any sugar. Allele from Parent 1 Allele from Parent 2 Genotype of offspring Blood type of offspring I A I A I A I A A I A I B I A I B AB I A i I A i A I B I A I A I B AB I B I B I B I B B I B i I B i B i i i i O Multiple alleles: When more than two alleles control a character, as in human blood groups o Multiple alleles are used in population studies. Inheritance of Two Genes (Dihybrid Cross) & Law of Independent Assortment Inheritance of Two Genes (Dihybrid Cross) In dihybrid cross, we consider two characters. (e.g., seed colour and seed shape) Yellow colour and round shape is dominant over green colour and wrinkled shape.

30 Page30 Phenotypic ratio 9:3:3:1 Round yellow 9 Round green 3 Wrinkled yellow 3 Wrinkled green 1 Law of independent Assortment When two pairs of traits are combined in a hybrid, one pair of character segregates independent of the other pair of character. In a dihybrid cross between two plants having round yellow (RRYY) and wrinkled green seeds (rryy), four types of gametes (RY, Ry, ry, ry) are produced. Each of these segregate independent of each other, each having a frequency of 25% of the total gametes produced. Chromosomal Theory of Inheritance Rediscovery of Mendel s Work Mendel s work remained unrecognised for several years because of the following reasons. o Lack of communication and publicity o His concept of factors (genes) as discrete units that did not blend with each other was not accepted in the light of variations occurring continuously in nature. o Mendel s approach to explain biological phenomenon with the help of mathematics was also not accepted. o In 1990, three scientists Hugo devries, Correns and Von Tschermak independently rediscovered Mendel s work. Chromosomal Theory of Inheritance By 1900, due to the advancement in microscopy, chromosomes were also discovered. Sutton and Bovery discovered that the behaviour of chromosomes was parallel to the behaviour of genes. Chromosomes and genes both occur in pairs two alleles of a gene pair are located on homologous sites of homologous chromosomes. Sutton and Bovery further proposed that it is the pairing and separation of a pair of chromosomes that ultimately leads to segregation of the pair of factors they carry. Union of knowledge of chromosomal segregation with Mendelian principles constitutes chromosomal theory of inheritance.

31 Page31 Dihybrid Cross in Drosophila to Study Linkage and Recombination Linkage and Recombination Thomas Hunt Morgan discovered the basis of variations that sexual reproduction produced. He worked on fruit flies, Drosophila melanogaster. He chose Drosophila because of the following reasons: o They were suitable to grow on synthetic medium in laboratory. o Their life cycle is complete in two weeks. o Single mating produces many progeny flies. o Clear differentiation of sexes Easily distinguishable male and female o Hereditary variations clearly visible with low power microscopes Morgan s experiment o Dihybrid cross was carried out on fruit flies. Yellow bodied, white eyed females were crossed with brown bodied, red eyed males. o F 1 progeny was obtained, which were inter-crossed. o F 2 progeny was obtained and F 2 ratio was observed. o F 2 ratio was observed to be significantly different from 9:3:3:1 as observed in Mendelian dihybrid cross. Explanation of deviation from Mendelian ratio: o Genes involved are located on X chromosome. o When two genes are located on the same chromosome, the proportions of parental gene combinations were much higher than those of non-parental. o Linkage Physical association of genes on a chromosome o Recombination Non-parental gene combination EXCLUSIVE MAINS BATCH (TEST SERIES INCLUDED) MODULEWISE ADMISSION 1. An integrated approach is an approach where you need to understand topics holistically. The Wisdom academy has come up with strategy to complete the mains syllabus exhaustively in stipulated time of 3 months. 2. An integrated approach is the method where different topics are studied together, which are Scattered in general studies syllabus. So we have restructured different topics in 9 modules. Each module followed by a full length comprehensive test. 3. An integrated 9 module coverage of whole GS syllabus. 4. Separate session for essay writing will be conducted which includes 4 essay test. 5. All UPSC like exams will be conducted which will have essay and full length comprehensive test which will make you ready for ULTIMATE UPSC MAINS EXAM. 6. Total test-17 (9 module + 4 comprehensive + 4 essay). 7. Comprehensive checking of papers with due feedbacks 8. Officers feedback on test answers, writing sessions with officers in person via SKYPE etc 9. Test discussion with good answers along with model answers circulation from candidates themselves 10. MODULEWISE ADMISSION 11. We would be completing the course 25days prior to exam. Leaving aspirant enough time for revision. Following are the topics a candidate should study and represent answer as per requirement of General studies mains paper. OPEN SESSION **11th JUNE and 12th JUNE ANSWER WRITING WORKSHOP BY OFFICER REGISTER YOURSELF BY

32 Page32 Alfred Sturtevant utilised the knowledge of frequency of gene recombination as a measure of physical distance between two genes and to map their position on chromosomes. In this way, genetic maps were prepared, which are extensively used today for genome sequencing projects as in human genome project. Sex Determination in Various Animals Including Humans-Male and Female Heterogamety Sex Determination Henking discovered the genetic/chromosomal basis of sex determination by working on insects. He observed specific nuclear structures during spermatogenesis in insects. He named these structures as X bodies. He observed that after spermatogenesis, 50% of the sperm obtained these structures, while 50% did not. Later on, it was found that the X body observed by Henking was actually a chromosome and thus, this chromosome was named X chromosome. Chromosomes involved in sex determination are called sex chromosomes, while the other chromosomes are called autosomes.

33 Page33 XO type of sex determination o Other than autosomes, at least one X chromosome is present in all insects. o Some sperms contain X chromosomes, while some do not. o Eggs fertilised by sperms having X chromosomes become females. So, females have two X chromosomes. o Eggs fertilised by sperms not having X chromosomes become males. So, males have only one X chromosome. o Example of organisms with XO type of sex determination Insects XY type of sex determination o Males have X chromosome and its counterpart Y chromosome, which is distinctly smaller. Hence, males are XY. o Females have a pair of X chromosomes. Hence, females are XX. o Example of organisms with XY type of sex determination Humans and Drosophila Male heterogamety XO and XY types of sex determination are examples of male heterogamety. o In XO type, some gametes have X chromosomes, while some gametes are without X chromosomes. o In XY type, some gametes have X chromosomes, while some gametes have Y chromosomes. Female heterogamety ZW type of sex determination is an example of female heterogamety. o In ZW type, the female has one Z and one W chromosome, while the male has a pair of Z chromosomes. Mutation, Pedigree Analysis, & Genetic Disorders Mutation Alteration of DNA sequence resulting in changes in genotype and phenotype of organisms DNA helix runs in a chromatid, hence any change (insertion or deletion) in the DNA sequence affects the chromosome. Point Mutation Mutation arising due to change in single base pair of DNA as in sickle cell anaemia Frameshift Mutation Mutations arising due to deletion or insertion in DNA sequence Mutagens Chemical or physical agents that lead to mutations Example UV radiations Pedigree Analysis Pedigree analysis is the analysis of inheritance of traits in several generations of a family. A particular trait under study is represented in a family tree. By using pedigree analysis, inheritance of a specific trait, abnormality or disease, can be traced. DNA is believed to be the carrier of genetic information, which passes unaltered from generation to generation. Mutations occasionally alter the genetic material and genetic diseases are believed to be associated with these alterations only. Standard symbols in pedigree analysis are as follows:

34 Page34 Pedigree chart is represented as follows: Chart (a) represents inheritance of an autosomal dominant trait as in muscular dystrophy. Chart (b) represents inheritance of an autosomal recessive trait as in sickle cell anaemia. Genetic Disorders Include Mendelian disorders and chromosomal disorders Mendelian Disorders Characterized by mutation in a single gene Their mode of inheritance follows the principles of Mendelian genetics. Mendelian disorders can be o autosomal dominant (muscular dystrophy) o autosomal recessive (sickle cell anaemia) o sex linked (haemophilia) Haemophilia o Sex-linked recessive disease o Transmission From unaffected female (carrier) to male progeny o Females act as carriers of disease, but rarely suffer from haemophilia since for a female to become haemophilic, the mother should be carrier and father should be haemophilic. o In this disease, protein involved in blood clotting is affected. Therefore, even a simple cut results in uncontrolled bleeding.

35 Page35 Sickle cell anaemia o Autosomal recessive disease o Transmission From parent to offspring when both parents are carriers of disease o Pair of alleles Hb A and Hb S controls the expression of this disease. Hb A and Hb A Normal Hb A and Hb S Carrier of disease Hb S and Hb S Diseased o Cause of the disease Change in gene causes the replacement of GAG by GUG leading to the substitution of Glu by Val at sixth position of beta globin chain of haemoglobin. o The mutant haemoglobin so formed polymerises at low oxygen tension, resulting in change in shape of RBC to sickle-like. Phenylketonuria o Autosomal recessive disease o Phenylalanine Tyrosine The enzyme responsible for this conversion gets mutated. o Phenylalanine accumulates. Then, Phenylalanine Phenylpyruvic acid Accumulates in brain Mental retardation o Phenylpyruvic acid also gets excreted through urine since kidneys poorly reabsorb it. Chromosomal Disorders Total number of chromosomes in humans = 46 (23 pairs) Total 23 pairs = Autosomes (22 pairs) + Sex chromosomes (1 pair) Monosomy Lack of any one pair of chromosomes Trisomy Inclusion of an additional copy of chromosomes Aneuploidy Loss or gain of chromosomes due to failure of segregation of chromatids during cell division Chromosomal Disorders Total number of chromosomes in humans = 46 (23 pairs) Total 23 pairs = Autosomes (22 pairs) + Sex chromosomes (1 pair) Monosomy Lack of any one pair of chromosomes Trisomy Inclusion of an additional copy of chromosome Aneuploidy Loss or gain of chromosomes due to the failure of segregation of chromatids during cell division Down s Syndrome o Cause: Presence of an additional copy of chromosome 21 (Trisomy of 21) o Affected individual has short stature, small, round head, furrowed tongue, partially opened mouth, palm crease, congenital heart disease and mental retardation. Klinefelter Syndrome o Cause: Additional copy of X chromosome, i.e., 47 chromosomes (XXY) o Affected individual has an overall masculine development with gynaecomastia; individual is sterile Turner s Syndrome o Cause: Absence of one X chromosome, i.e., 45 chromosomes (XO). o Affected females are sterile; have rudimentary ovaries; secondary sexual characters are absent

36 Page36 MOLECULAR BASIS OF INHERITANCE DNA : Structure of Polynucleotide Chain DNA Polymer of deoxyribonucleotides Nucleoside = Nitrogenous base + Pentose sugar (linked through N glycosidic bond) Example adenosine, deoxyadenosine, cytidine, etc. Nucleotide = Nucleoside + Phosphate group (linked through phosphodiester bond) Many nucleotides link together through 3 5 phosphodiester bond to form polynucleotide chain (as in DNA and RNA). In course of formation of polynucleotide chain, a phosphate moiety remains free at 5 end of ribose sugar (5 end of polymer chain) and one -OH group remains free at 3 end of ribose (3 end of polymer chain). Double Helix Model for the Structure of DNA Scientists involved o Friedrich Meischer First identified DNA as an acidic substance present in nucleus and named it as Nuclein o Wilkins and Franklin Produced X-ray diffraction data for DNA structure o Watson and Crick Proposed double helix structure model for DNA based on X-ray diffraction data o Erwin Chargaff Proposed that in ds DNA, ratios A:T and C:G remain same and are equal to one Features of double helix structure of DNA: In a DNA, two polynucleotide chains are coiled to form a helix. Sugar-phosphate forms backbone of this helix while bases project in wards to each other. Complementary bases pair with each other through hydrogen bond. Purines always pair with their corresponding pyrimidines. Adenine pairs with thymine through two hydrogen bonds while guanine pairs with cytosine through three hydrogen bonds.

37 Page37 o o Packaging of DNA Helix Packaging of DNA Helix The helix is right-handed. Pitch 3.4 nm 10 bp in each turn The plane of one base pair stacks over the other in a double helix. This provides stability to the helix along with hydrogen bonding. Distance between two consecutive base pairs in a DNA = 0.34 nm = m Total number of base pairs in a human DNA = bp Total length of human DNA = = ~ 2.2 m 2.2 m is too large to be accommodated in the nucleus (10 6 m). Organisation of DNA in prokaryotes: o They do not have nucleus. DNA is scattered. o In certain regions called nucleoids, DNA (negatively charged) is organised in large loops and is held by some proteins (positively charged). Organisation of DNA in eukaryotes: o They have positively charged basic proteins called histones (positive and basic due to presence of positive and basic amino acid residues, lysine and arginine). o Histone octamer Unit of eight molecules of histone o DNA (negatively charged) winds around histone octamer (positively charged) to form nucleosome. o o o o 1 nucleosome has approx. 200 bp of DNA. Nucleosomes in a chromatin resemble beads present on strings. Beads on string structure in chromatin are further packaged to form chromatin fibres, which further coil and condense to form chromosomes during metaphase. Non-histone chromosomal proteins Additional set of proteins required for packaging of chromatin at higher level

38 Page38 Transforming principle, Hershey and Chase experiments, & Properties of genetic material Discovery of DNA as a Genetic Material Though principles of inheritance and discovery of chromosomes in nucleus were achieved long time back, there was confusion about which molecule acted as genetic material. Transforming Principle Griffith performed experiments with the bacteria Streptococcus pneumoniae. This bacterium has two strains S strain and R strain. S strain Bacteria R strain Bacteria o Produce smooth colonies on culture plate o Produce rough colonies on culture plate o Have a polysaccharide coat o Do not have a polysaccharide coat o Virulent (causes pneumonia) o Non-virulent (does not cause pneumonia) Griffith s experiment

39 Page39 Live R strain in the presence of heat-killed S strain produce virulence because somehow R strain bacteria is transformed by heat-killed S strain bacteria. Hence, it was concluded that there must be transfer of genetic material. Biochemical Nature of Transforming Material Avery, McLeod, and McCarthy worked to determine the biochemical nature of genetic material responsible for transformation. This suggests that DNA has to be the genetic material. Hershey and Chase Experiment to Confirm DNA as the Genetic Material Hershey and Chase worked on bacteriophages (viruses that infect bacteria). When a bacteriophage infects a bacterium, the viral genetic material gets attached with the bacterial genetic material and bacteria then treats the viral genetic material as its own to synthesise more viral particles. Hershey and Chase worked to discover whether it was a protein or DNA that entered the bacteria from virus. They labelled some phages with radioactive sulphur and the others with radioactive phosphorus. These radioactive phages were used to infect E. coli. E.coli was then blended and centrifuged to remove viral particles. It was observed that bacteria with radioactive DNA were radioactive while those with radioactive proteins lost their radioactivity. This showed that it is the DNA that enters the bacteria from viruses and not proteins. Hence, it was concluded that DNA is the genetic material. Properties of the Genetic Material It should be able to replicate (duplicate to produce its identical copy). It should be chemically and structurally stable.

40 Page40 It should have scope for changes that are essential for evolution. It should follow the Mendelian principles of inheritance. Difference between DNA and RNA: DNA RNA 1. Has deoxyribose sugar 2. Has ribose sugar 3. 5-methyl uracil (thymine) is present. 5. Mostly DNA acts as the genetic material. 4. Uracil is present in place of thymine. 6. RNA acts as a messenger and adaptor. It acts as a genetic material in some viruses. 7. DNA is stable. 8. Presence of 2 OH group at every nucleotide makes RNA labile and easily biodegradable. 9. Chemically less reactive, mutates slowly 11. DNA requires RNA for protein synthesis. DNA RNA Protein 10. Mutation in RNA is faster. 12. RNA directly codes for proteins. Why DNA is more stable than RNA? In RNA, a 2 OH group is present at every nucleotide. This makes RNA unstable and degradable. Presence of thymine in place of uracil confers additional stability to DNA. RNA being a biocatalyst is more reactive. DNA is double-stranded having complementary strand, which resists the changes by repair mechanism. DNA Replication with Experimental Proof Machinery and Enzymes Involved What is DNA Replication? DNA replication is the phenomenon in which a duplicate copy of DNA is synthesised. In replication, two strands of the DNA helix separate and each strand acts as a template for synthesising new complementary strands. After completion of replication, the two copies so produced will have one parental and one newly synthesised strand. This scheme of replication is called semi-conservative replication.

41 Page41 Experiment to Prove That DNA Replicates Semi-Conservatively Performed by Messelson and Stahl E.coli was grown in a medium containing heavy isotope 15 N as the nitrogen source. 15 N was incorporated into newly synthesised DNA as well and the DNA became heavy DNA. Heavy DNA molecule can be differentiated from normal DNA by density gradient centrifugation using cesium chloride as the gradient. Then, cells were again transferred into a medium with 14 N as nitrogen source. Samples were taken from this media and their DNA was extracted. E.coli divides every 20 minutes. Therefore, the DNA extracted after 20 minutes had a hybrid density. DNA extracted after 40 minutes had equal amount of hybrid and light intensities. This implies that the newly synthesised DNA obtained one of its strands from the parent. Thus, replication is semi-conservative. Mechanism of DNA Replication Replication occurs in S phase of cell cycle. Enzyme involved - DNA polymerase (DNA dependent DNA polymerase) Replication requires energy. Source of energy Deoxyribonucleoside triphosphates (DNTPs) DNTPs have dual purpose Act as substrates and provide energy also Replication initiates at specific regions in DNA called origin of replication. DNA polymerase polymerises a large number of nucleotides in a very short time. During the course of replication, two parent strands do not completely open, but a small opening forms in which replication occurs. This small opening forms a replication fork. DNA polymerase can polymerise only in one direction that is '. Therefore, replication occurs smoothly at to end of DNA. (continuous replication, but occurs discontinuously at to end) The discontinuous fragments so formed are joined by DNA ligase.

42 Page42 Transcription Unit --- Structure and its Relationship with a Gene Transcription Transcription is the process of formation of RNA molecules from the DNA. During transcription, only a segment of DNA from only one of the strands participates. Both strands are not copied during transcription because: o If both strands get transcribed at the same time since the sequences of amino acid would be different in both (due to complementarity), then two RNA molecules with different sequences will be formed, which in turn give rise to two different proteins. Therefore, one DNA would end up giving rise to two different proteins. o Two RNA molecules so formed will be complementary to each other, hence would end up forming a double-stranded RNA leaving the entire process of transcription futile. Transcriptional Unit A transcriptional unit has primarily three regions: o Promoter Marks the beginning of transcription; RNA polymerase binds here o Structural gene Part of the DNA that is actually transcribed o Terminator Marks the end of transcription Template Strand and Coding Strand Enzyme involved in transcription, RNA polymerase (DNA dependent RNA polymerase), catalyses in only one direction i.e., 5 to 3. Therefore, the strand with polarity 3 5 acts as a template (Template Strand). The strand with polarity 5 3 acts as coding strand (which is a misnomer since it does not code for anything). Coding strand has sequence similar to RNA formed after transcription except for the change that thymine is present instead of uracil. Gene The DNA sequence which codes for trna or rrna molecule defines a gene. Cistron Segment of DNA that contains the genetic code for a single polypeptide The structural genes could be of two types: o Monocistronic (mostly in eukaryotes) o Polycistronic (mostly in prokaryotes) Monocistronic genes have two parts: o Exon Sequences that code for a particular character and is expressed in a matured and processed mrna o Intron Interrupting sequences that do not appear in a mature and processed mrna Regulatory genes Sequences that do not code for anything, but have regulatory functions Types of RNA & Transcription Process Types of RNA mrna (messenger RNA) It serves as a template for protein synthesis. DNA is transcribed to form an mrna, which in turn is translated to form protein. [Central dogma of molecular biology] trna (transfer RNA) It brings amino acids during translation and reads the genetic code.

43 Page43 rrna (ribosomal RNA) These are the work benches of translation. They play a structural and catalytic role during translation. Transcription Process Transcription has three steps initiation, elongation, and termination. Initiation: o RNA polymerase binds with the promoter to initiate the process of transcription. o Association with initiation factor (σ) alters the specificity of RNA polymerase to initiate the transcription. Elongation: o RNA polymerase uses nucleotide triphosphate as substrate, and polymerisation occurs according to complementarity. Termination: o Termination occurs when termination factor (P) alters the specificity of RNA polymerase to terminate the transcription. As the RNA polymerase proceeds to perform elongation, a short stretch of RNA remains bound to the enzyme. As the enzyme reaches the termination region, this nascent RNA falls off and transcription is o terminated. Complexities Associated with Transcription In prokaryotes: o There is no clear demarcation between cytosol and nucleus. Therefore, translation can begin even before transcription is completed. Thus, in prokaryotes, transcription and translation are coupled. In eukaryotes: o Three different kinds of RNA polymerases are present. RNA polymerase I transcribes rrna. RNA polymerase II transcribes hnrna (mrna precursor). RNA polymerase III transcribes trna, snrna, and srrna. o The precursor of mrna, i.e. hnrna, contains both introns and exons. Introns are removed and exons are joined by a process called splicing. o Capping In this, methyl guanosine triphosphate is added to the 5 end of hnrna. o Tailing In this, adenylate residues are added to the 3 end of hnrna.

44 Page44 o When hnrna is fully processed, it is known as mrna, which is transported out of the nucleus to get translated. Genetic Code and Study of Mutations Genetic Code Genetic code directs the sequence of amino acids during the synthesis of proteins. George Gamow proposed that if 20 amino acids are to be coded by 4 bases, then the code should be made up of three nucleotides. 4 3 = 64 (4 2 = 16), which is less than 20; so, the codon was proposed to be triplet. Har Gobind Khorana developed a chemical method to synthesise RNA molecules with defined combination of bases. Nirenberg developed cell-free systems for protein synthesis, which helped the code to be deciphered. The enzyme known as Severo Ochoa enzyme (polynucleotide phosphorylase) helped to polymerise RNA with defined sequences in a template independent manner. It finally gave rise to the checker-board for genetic code. Salient features of genetic code: o Codon is triplet. 4 3 = 64 (61 codons code for amino acids while 3 are stop codons) o One codon codes for a single specific amino acid. Codons are unambiguous. o Codons are degenerate since some amino acids are coded by more than one codon. o Genetic code is universal. 1 codon codes for same amino acid in all species.

45 Page45 o o Codons are read continuous. They lack punctuations. AUG has dual functions Codes for Methionine and acts as a start codon Effects of Mutations on Genetic Code Mutations include insertions, deletions, and rearrangements. Mutation results in changed phenotype and diseases such as sickle cell anaemia. (Change Glu Val in gene coding for beta globin chain of haemoglobin) Such mutations are called joint mutations. Insertion or deletion of a single base pair disturbs the entire reading frame in mrna. Such mutations are called frameshift mutations. Frameshift mutations hold the proof of the fact that codon is triplet because if we insert three or multiple of three bases followed by the deletion of same number of bases, then the reading frame will remain unaltered. Structure of trna; Process of Translation; Regulation of Gene Expression trna trna is an adapter molecule. On one hand, it reads the genetic code and on the other hand, it binds to specific amino acids. trna has an anticodon loop that has bases complementary to the mrna code and an amino acid acceptor end where it binds to the corresponding amino acid. Initiation trna This trna is essential for initiation of translation and has AUG in anticodon loop and Met in amino acid acceptor end. There are no trnas for stop codons. Translation The mrna contains the genetic information, which is translated into the amino acid sequence with help of trna. Amino acids are polymerised to form a polypeptide. Amino acids are joined by peptide bond. First of all, charging of trna (amino-acylation of trna) takes place. In this, amino acids are activated in the presence of ATP and are linked to their corresponding trna. Ribosomes are the workbenches for translation. Ribosomes have 2 subunits: a large subunit and a small subunit. Smaller subunit comes in contact with mrna to initiate the process of translation. Translational unit in an mrna is the region flanked by start codon and stop codon. Untranslated regions (UTR) are the regions on mrna that are not themselves translated, but are required for efficient translation process. They may be present before start codon (5 UTR) or after stop codon (3 UTR). Initiator trna recognises the start codon. (Initiation) Then t-rna-amino acid complexes bind to their corresponding codon on the mrna and base pairing occurs between codon on mrna and trna anticodon.

46 Page46 trna moves from codon to codon on the mrna and amino acids are added one by one. (Elongation) Release factor binds to stop codon to terminate the translation. (Termination) Regulation of Gene Expression Regulation of gene expression could be exerted at following levels. o Transcriptional level (following of primary transcripts) o Processing level (splicing) o Transport of mrna from nucleus to cytoplasm o Translational level In addition, metabolic, physiological, or environmental conditions regulate the expression of genes. Expression of genes coding for enzymes is required only when substrate for that enzyme is available. For example: Lactose Glucose + Galactose E.coli synthesises beta-galactosidase, only when lactose is available. Regulation in prokaryotes o Gene expression is regulated by controlling the rate of transcriptional initiation. o The activity of RNA polymerase at a given promoter is regulated by accessory proteins. The accessory proteins affect the ability of a promoter to recognise start sites. o A regulatory protein could be activator or repressor. o Accessibility of promoter is also affected by operators. Operator is the region located adjacent to promoter. o Each operon has a specific operator and a specific repressor. o Usually operator binds to a repressor protein. Regulation of Lac Operon Lac Operon Operon An arrangement where a polycistronic gene is regulated by a common promoter and regulatory genes Lac operon, trp operon, his operon, val operon are the examples of such systems. The elucidation of lac operon as a transcriptionally active system was first done by geneticist Jacob and biochemist Monod. Genes constituting lac operon: Gene Nature Function i gene Inhibitor It codes for repressor of lac operon. z gene Structural It codes for β-galactosidase. Lactose Galactose + Glucose y gene Structural It codes for permease, which increases the permeability of cell to β-galactosidase. a gene Structural It codes for transacetylase. All genes involved in lac operon are required for metabolism of lactose. Inducer Lactose acts as an inducer for lac operon since it regulates the switching on and off of the operon.

47 Page47 If lactose is provided to the growth media of bacteria in absence of any other carbon source, then it is transported inside the cells by permease. For permease to be present and lactose to enter inside the cells, low level of expression of lac operon must be present all the time. Regulation in Absence of Inducer In absence of inducer, i gene transcribes to synthesise repressor mrna, which translates to form repressor. This repressor binds with the operator region of operon and prevents RNA polymerase to transcribe genes z, y, and a (negative regulation). Therefore, in absence of the products of these genes, metabolism of lactose ceases. Regulation in Presence of Inducer Inducer binds with the protein product of gene i (repressor) and inactivates it. This inactivated repressor is unable to inactivate RNA polymerase enzyme and z, y, and a genes synthesise their respective mrna, which in turn gets translated to form β-galactosidase, permease, and transacetylase. In presence of all these enzymes, the metabolism of lactose proceeds in a normal manner. Human Genome Project (HGP) Joint venture of US department of energy and National Institute of Health (NIH); later joined by Welcome Trust (UK) Launched in 1990, completed in 2003 This project worked towards the determination of complete DNA sequence of humans. DNA is the storehouse of genetic information and determining its sequence of base pairs can solve many medical, agricultural, environmental, and evolutionary mysteries. Relationship of HGP with Bioinformatics Human genome (genome refers to the totality of genes that are present in a human being) contains base pairs. Cost of sequencing 1 bp = US $ 3 Cost of sequencing bp = US $ 9 billion Enormous sequence data so generated would have required 3300 books containing 1000 pages each just for a human genome. Hence, for storing, retrieving, and analysing this enormous data, a new branch of biology has been developed known as bioinformatics. Genomes of many non-human models such as bacteria, yeast, Caenorhabditis elegans, Drosophila, plants (rice and Arabidopsis) have also been sequenced.

48 Page48 Methods to Identify Genes Two methods identifying ESTs (Expressed sequence Tags) and sequence annotation ESTs As the name suggests, this refers to the part of DNA that is expressed, i.e. transcribed, as mrna and translated into proteins thereafter. It basically focuses on sequencing the part denoting a gene. Annotation In this approach, entire genome (coding + non-coding) is sequenced and later on function is assigned to each region in the genome. Genome Sequencing DNA from the cells is isolated and is randomly broken into fragments of smaller sizes. These fragments are cloned into suitable host using vectors. Cloned fragments amplify in the host. Amplification facilitates an easy sequencing. Common vectors used BAC (Bacterial artificial chromosomes) and YAC (Yeast artificial chromosomes) Common hosts Bacteria and yeasts Automated sequencers are used to sequence these smaller fragments (Sanger sequencing). The sequences so obtained are arranged based on overlapping regions within them (alignment). Alignment of the sequences is also done automatically by computer programs. Then these sequences are annotated and assigned to each chromosome. Preparation of Genetic and physical maps on Genome 2 methods are used restriction polymorphism and microsatellites Restriction polymorphism Specialized enzymes called restriction endonucleases are used to cut the genome at specialized sites called restriction endonuclease recognition site and maps are prepared based on it. Microsatellites These are repetitive DNA sequences. Observations from HGP Human genome contains ( million) nucleotide bases. An average gene consists of 3000 bases. However, the size of genes varies. Largest gene is dystrophin (2.4 m bases). Total number of genes in human genome 30,000 Over 50% of the discovered genes have unknown functions. Less than 2% of genome is coding. Large portion of genome consists of repeating sequences. Repetitive sequences have no coding function. They are repeated over hundred to thousand times. They may have a role in evolution, chromosome structure, and dynamics. Chromosome with most genes Chromosome 1 (2968) Chromosome with fewest genes Chromosomes Y (231) SNPs (single nucleotide polymorphism) occur at about 1.4 million locations in human DNA. They are believed to have significance in explaining diseases and evolutionary history of human beings. DNA Fingerprinting Introduction DNA fingerprinting is a method for comparing the DNA sequences of any two individuals. 99.9% of the base sequences in all human beings are identical. It is the remaining 0.1% that makes every individual unique. It is a really difficult and time-consuming task to sequence and compare all bases in two individuals. So, instead of considering the entire genome, certain specific regions called repetitive DNA sequences are used for comparative study. Basis of DNA Fingerprinting Repetitive DNA is separated from bulk genomic DNA since it appears as a distinct peak during density gradient centrifugation. Major peak: Formed by bulk DNA Smaller peak: Satellite DNA

49 Page49 Satellites are of two types micro-satellites and mini satellites, depending upon the base composition, length of segment and the number of repetitive units. Satellites do not code for proteins, but have a major role to play in DNA fingerprinting. Polymorphism is actually a result of mutation. A germ cell mutation (which can pass on to the next generation through sexual reproduction) gives rise to polymorphism in populations. In other words, an inheritable mutation if observed in higher frequencies in a population is known as polymorphism. Polymorphisms arise normally in non-coding sequences because mutations in non-coding sequences do not affect an individual s reproductive ability. Methodology of DNA fingerprinting VNTR (variable number of tandem repeats) are satellite DNAs that show high degree of polymorphism. VNTRs are used as probes in DNA fingerprinting. First of all, DNA from an individual is isolated and cut with restriction endonucleases. Fragments are separated according to their size and molecular weight on gel electrophoresis. Fragments separated on electrophoresis gel are blotted (immobilised) on a synthetic membrane such as nylon or nitrocellulose. Immobilised fragments are hybridised with a VNTR probe. Hybridised DNA fragments can be detected by autoradiography. VNTRs vary in size from 0.1 to 20 kb. Hence, in the autoradiogram, band of different sizes will be obtained. These bands are characteristic for an individual. They are different in each individual, except identical twins. Applications of DNA Fingerprinting DNA fingerprinting is widely used in forensics since every DNA of every tissue from an individual has the same degree of polymorphism. DNA fingerprinting forms the basis of paternity testing since a child inherits polymorphism from both its parents. It can be used for studying genetic diversity in a population and evolution.

50 Page50 EVOLUTION Origin of Life Year Scientist Theory/Experiment Conclusion 1927 Lemaitre Big Bang theory The universe expanded from explosion of a primordial, hot substance Oparin and Haldane Chemical evolution preceded organic evolution Simple organic molecules originated from inorganic precursors Stanley Miller and Urey Synthesis of biomolecules by creation of similar conditions as primitive atmosphere on laboratory scale Amino acids were synthesised from ammonia, oxygen, and carbon dioxide inside specialised apparatus. Urey and Miller experiment Primitive atmosphere had high temperature, volcanic storms, and reducing atmosphere, containing CH 4, NH 3, H 2, etc. Urey and Miller took the same compounds in a closed flask along with water vapour at 800 º C and created an electric discharge. Formation of biomolecules such as amino acids, simple sugars, fats, etc. was observed in the flask. Theories of Evolution The theory of special creation or divine intervention was challenged by Charles Darwin. He made observations on his sea-trip around the world aboard H.M.S. Beagle and concluded that all existing living forms share similarities among themselves and also with other life forms, which existed millions of years ago of which many are extinct.

51 Page51 The evolution of life forms has been gradual and those life forms better fit in environments that leave more progeny. This is called natural selection and is a mechanism of evolution. Alfred Wallace working in the Malay Archepelago also came to the same conclusion. Evidences of Evolution Fossils They represent plants and animals that lived millions of years ago and are now extinct. Different aged rock sediments contain fossils of different life-forms, which probably died during the formation of the particular sediment. Comparative anatomy and morphology It shows evidences of the similarities and differences between living forms of today and that of the prehistoric times. Some of the examples of comparative anatomy and morphology are: Homologous organs All mammals share the same pattern of forelimbs. Though they perform different functions, they are anatomically similar. This is called divergent evolution and the structures are called homologous structures (common ancestors). Analogous organs The pair of organs is not anatomically similar, but performs the same function (e.g., the wings of butterflies and birds). This is called convergent evolution. Adaptive melanism In England, it was noted that before industrial revolution, the number of white-winged moths was more than that of dark melanised moth. However, after industrialisation, there were more of dark melanised moths. The explanation was that after industrialization, the tree trunks became darker with deposits of soot and smoke and hence, the number of dark moths increased in order to protect themselves from predators while the white-winged ones were easily picked up by the predators. Similarly, the herbicide and pesticide resistant plants and animals and antibiotic resistant bacteria are some of the evidences that point towards evolution. Adaptive Radiation During his exploration of the Galapagos Islands, Darwin noticed that there were many varieties of finches in the same island. They varied from normal seed eating varieties to those that ate insects. This process of evolution starting from a single point and radiating in different directions is called adaptive radiation. The other example for this is the evolution of the Australian marsupials from a single ancestor. Placental mammals also exhibit similarities to their corresponding marsupial. Example: placental wolf and the Tasmanian wolf When more than one adaptive radiation occurs in an isolated geographical area, the phenomenon is called convergent evolution.

52 Page52 Biological Evolution & Mechanism of Evolution According to Darwin, evolution took place by natural selection. The number of life forms depends upon their ability to multiply and their life span. Another aspect of natural selection is the survival of the fittest, where nature selects the individuals, which are most fit, to adapt to their environment. Branching descent and natural selection are the two important concepts of Darwin s theory of evolution. The French naturalist Lamarck observed that evolution occurs due to the use or disuse of particular organs or body parts. For example, giraffe have developed long necks as a result of attempts to eat leaves high up on trees. Darwin also observed that variations are inheritable and the species fit to survive the most, leaves more offsprings. Hence, the population s characteristics change, giving rise to the evolution of new life forms. Mechanism of Evolution Darwin did not quite explain how evolution gave rise to different species of the same organism. Mendel mentioned about inheritable factors, which influenced the phenotype of an organism. Hugo de Vries based on his work on evening primrose suggested that variations occurred due to mutations. Mutations are random and directionless while the variations that Darwin talked about were small and directional. Hugo de Vries gave the name saltation (single step large mutation) to the mutations which brought about speciation. Hardy-Weinberg Principle The frequency of occurrence of alleles of a gene in a population remains constant through generations unless disturbances such as mutations, non-random mating, etc. are introduced. Genetic equilibrium (gene pool remains constant) is a state which provides a baseline to measure genetic change. Sum total of all allelic frequencies is 1. Individual frequencies are represented as p and q such as in a diploid, where p and q represent the frequency of allele A and a. The frequency of AA is p 2, that of aa is q 2, and that of Aa is 2pq. Hence, p 2 + 2pq + q 2 = 1, which is the expansion of (p + q) 2. When the frequency measured is different from that expected, it is indicative of evolutionary change. Hardy-Weinberg equilibrium is affected by gene flow or gene migration genetic drift (changes occurring by chance) mutation genetic recombination natural selection Sometimes, the change in allele frequency is so prominent in the new sample of population that they become a different species and the original drifted population becomes the founder. This effect is called founder effect. The advantageous mutations that help in natural selection over the generations give rise to new phenotypes and result in speciation. Evolution of Plants and Animals Evolution of Plants Cellular life forms occurred on earth about 2000 million years ago. Some of these cells had the ability to produce oxygen through reactions similar to photosynthesis. Slowly, single-celled organisms became multicellular. Seaweeds and some plants probably existed around 320 million years ago.

53 Page53 Evolution of Animals Animals evolved about 500 million years ago. The first of them to evolve were invertebrates. Jawless fishes evolved around 350 million years ago. Some of the fishes could go on land, and then come back to water. These were the first amphibians. In 1938, a fish Coelacanth, which was thought to be extinct, was caught in South Africa. This variety of fish, called lobefins, is believed to have evolved into the first amphibians. Amphibians evolved into reptiles. In the next 200 million years, reptiles of different sizes dominated the earth. However, about 65 million years ago, some of them such as dinosaurs disappeared. The first among the mammals were small shrew-like mammals. During continental drift when North America joined South America, primitive mammals suffered, but pouched mammals of Australia survived the same drift because of lack of competition from other mammals.

54 Page54 Origin and Evolution of Man Year Evolution Characteristics 15 million years ago Dryopithecus (ape-like) and Ramapithecus (man-like) Hairy and walked similar to chimpanzees 3 4 million years ago Man-like primates Not tall, but walked straight 2 million years ago Australopithecines, also called Homo habilis,lived in East Africa Used stone weapons and ate fruits; human-like with brain capacity of cc; not meat eaters 1.5 million years ago Homo erectus Brain capacity of about 900 cc; were meat eaters 1,000 40, 000 years ago Neanderthal man Brain capacity of 1400 cc; used hides 75, , 000 years ago Homo sapiens When we compare the skulls of an adult human being, baby chimpanzee, and adult chimpanzee, we observe that skull of baby chimpanzee resembles human being more as compared to adult chimpanzee.

55 Page55 What is Health? COMMON DISEASES IN HUMANS Health is the state of complete physical, mental, and social well being. Health increases productivity and ensures longevity. Ways to Ensure Good Health Balanced diet Personal hygiene Exercise Awareness about prevention and control of diseases Proper waste disposal and control of vectors Vaccination Why do Diseases Occur? Genetic reasons Innate deficiencies and inheritable defects Infections Sedentary life style Junk food, consumption of alcohols/drugs, lack of exercise Pathogenic Diseases Pathogens are the parasites that enter the human body through various means, then multiply, and interfere with normal vital activities. Bacterial Diseases Viral Diseases Typhoid o Pathogen Salmonella typhi o Spreads through Contaminated food and water o Site of infection Small intestine o Symptoms High fever, stomach pain, headache, loss of appetite, constipation, and intestinal perforations in severe cases o Confirmatory test Widal test Pneumonia o Pathogens Streptococcus pneumoniae and Haemophilus influenzae o Spreads through Droplets/aerosols released from infected person, sharing of glasses or utensils o Site of infection Alveoli (gets filled with fluid, difficulty in breathing) o Symptoms Fever, chills, cough, headache, lips and nails become grey in severe cases Common cold o Pathogen Rhino viruses o Site of infection Nose and respiratory passage o Spreads through Droplets released from coughing or sneezing, or contaminated objects o Symptoms Nasal congestion and discharge, sore throat, cough, headache, tiredness Protozoan Diseases Malaria o Pathogen Plasmodium sps. (P.vivax, P. falciparum, P. malaria) o Vector Female Anopheles mosquito o Symptoms High grade fever, chills Amoebiasis o Pathogen Entamoeba histolytica o Vector Housefly o Site of infection Large intestine o Symptoms Constipation, abdominal pain, cramps, stools with mucous, and blood clots

56 Page56 Fungal Diseases Ringworms o Pathogens Genera Microsporum, Trichophyton, and Epidermophyton o Spreads through Towels, clothes, comb (Fungus is acquired from soil) o Symptoms Appearance of dry, scaly lesions on various body parts with intense itching Diseases Caused by Worms Ascariasis o Pathogen Round worm, Ascaris o Spreads through Water, vegetables, fruits contaminated by faeces of infected person o Symptoms Internal bleeding, muscular pain, fever, anaemia, blockage of intestinal passage Elephantiasis (filariasis) o Pathogen Wuchereria (W.malayi and W.bancrofti) o Spreads through Bite of female mosquito vector o Symptom Chronic inflammation of the organs, usually the lymphatic vessels of lower limb Life Cycle of Plasmodium Plasmodium requires two hosts to complete its life cycle. When female Anopheles mosquito bites a healthy human being, it releases Plasmodium, which lives in its body as sporozoite (infectious form). The parasites multiply (asexual reproduction) in the liver cells and finally burst the liver cells. Sporozoites are released in blood. Parasites enter RBCs and further multiply (asexual reproduction) here and finally burst RBCs also. Bursting of RBCs is accompanied by release of a toxic substance called haemozoin (associated with fever and chills). In the RBCs, only sporozoites change into gametocytes (sexual stage). Gametocytes multiply. When the diseased person is bitten by a female Anopheles mosquito, gametocytes are introduced into the mosquito. Gametocytes fertilise and develop inside the intestine of mosquito to form sporozoites. Sporozoites are stored in the salivary glands of mosquito and are released into the healthy person who is bitten by this mosquito.

57 Page57 Immunity What is immunity? The ability of body to fight the disease-causing organisms is called immunity. Types of immunity Immunity is of two types innate immunity and acquired immunity. Innate immunity It is present from the time of birth. It is non-specific. It consists of 4 kinds of barriers. o Physical barriers Skin and mucus coating of respiratory, gastrointestinal, and urogenital tract prevent entry of microbes into body. o Physiological barriers Acid in stomach, saliva in mouth, tears from eyes o Cellular barriers Blood has leukocytes such as polymorpho nuclear leukocytes, monocytes, etc. and tissue has macrophages which phagocytose the microbes. o Cytokine barriers Special proteins called interferons are secreted by virus-infected cells that prevent the further spread of viral infection. Acquired immunity It is acquired, which means that it is produced in response to an encounter with a pathogen based on memory. It is pathogen specific. o When a pathogen for the first time infects a person, low intensity immune response is generated (primary response). o When the same pathogen attacks again, intensified immune response in generated, thereby preventing the occurrence of disease (secondary response). o Acquired immunity involves two types of cells B-lymphocytes and T- lymphocytes. o B-lymphocytes Secrete proteins called antibodies in response to pathogens Antibodies are specialized proteins with 4 peptide chains (2 light and 2 heavy), hence denoted as H 2 L 2. IgA IgM, IgE, etc. are examples of some of the antibodies. They generate humoral immune response (found in blood). o T-lymphocytes They help B-cells to produce antibodies. They generate cell -mediated immune response. This response helps the body to differentiate between self and non-self as occurs in case of graft rejection. Difference between active immunity and passive immunity Active Immunity o This is the naturally acquired immunity produced in the host body in response to an antigen. o Immunization and body naturally getting immune to a microbe that had caused infection previously are examples of active immunity. Passive immunity o When ready-made antibodies are provided to an individual to protect against foreign agents o Colostrums present in mother s milk contain IgA. Also, the foetus gets antibodies from mother through placenta. How does vaccination help? Vaccines are nothing but inactivated pathogens. These inactivated pathogens when introduced in the body produce a primary immune response and antibodies are produced against the pathogen. Memory B and T-cells are produced. Now when the pathogen again attacks the person, memory B and T-cells generate a massive immune response and the pathogen is killed. Problems of immune system Allergies o Exaggerated immune response to certain antigens present in environment o Allergens Substances in response to which allergy is produced E.g., dust, pollen, etc.

58 Page58 o Antibodies involved IgE type o During allergic reactions, chemicals such as histamines and serotonins are released. o Symptoms Sneezing, watery eyes, difficulty in breathing, etc. o Allergy test Patient is injected with small doses of allergens to monitor his response. o Antihistamines, adrenalins, and steroids may be given so that the symptoms of allergy subside. Autoimmunity o In autoimmunity, body generates immune response against its own cells. o Reasons Genetic and other unknown reasons o Example Rheumatoid arthritis is an autoimmune disease. Human immune system Lymphoid organs are of two types primary lymphoid organs and secondary lymphoid organs. Primary lymphoid organs consist of bone marrow and thymus. Here, immature lymphocytes are differentiated to form antigen-sensitive lymphocytes. o Bone marrow Here, all blood cells including lymphocytes are produced. o Thymus It is responsible for maturation of T-lymphocytes. This lobed organ is situated near the heart and keeps on reducing in size as the age increases. Secondary lymphoid organs Lymphocytes migrate here after attaining maturity. It includes spleen, lymph nodes tonsils, Peyer s patches, and appendix. o Spleen Large bean-shaped organ containing lymphocytes and phagocytes, which acts as a filter for blood o Lymph nodes Located at different points throughout the immune system, they trap the antigens present in lymph or tissue fluid, and these antigens cause activation of lymphocytes and generation of immune response. MALT (Mucosal-associated lymphoid tissue) Lines major tracts (respiratory, digestive, urogenital, etc); constitutes 50% of lymphoid tissue in body AIDS & Cancer AIDS (Acquired Immuno Deficiency Syndrome) Caused by HIV (Human Immunodeficiency Virus) [HIV is a retrovirus (RNA virus)] Transmission of HIV occurs through: o Sexual contact with infected person o Sharing infected needles (as in case of intravenous drug abusers) o Transfusion of contaminated blood o Infected mother to child through placenta Time lag between infection and appearance of symptoms Few months to many years (5-10 years) How does AIDS infection spread? o Virus enters the body of a person and enters macrophages.

59 Page59 o Here, virus replicates (viral RNA reverse transcribes to viral DNA, which gets incorporated into hosts DNA and subsequently new viral particles are produced). o o o o o Cancer Macrophages become a virtual HIV factory. Thereafter, HIV enters helper T-lymphocytes, replicates, and produces progenies. As the progenies are released, they attack other T-lymphocytes. Therefore, T-lymphocytes start decreasing in number and immune response of the person becomes weak. Even infections which could be overcome easily start aggravating. Diagnosis of AIDS By ELISA (Enzyme Linked Immuno Sorbent Assay) Treatment No permanent cure; antiretroviral therapies can prolong the life of patient Prevention of AIDS o Ensuring use of disposable syringes o Screeningblood from blood banks o Advocating safe sex o NACO (National AIDS Control Organization) and many NGOs are doing a lot to create awareness among people. The process of development of cancer is called oncogenic transformation. Normal cells have the property of contact inhibition (stoppage of growth on coming in contact with other cells), but cancer cells lose this property. As a result, cancer cells divide continuously to give rise to mass of cells (tumours). Tumours are of 2 types benign and malignant. Benign tumours Remain confined to their original location and do not spread Malignant tumours These exhibit metastasis i.e., the cells sloughed from such tumours reach distant sites and wherever they reach, new tumour is formed. Malignant tumours actually represent cancer. The cells actively divide, grow, and starve the normal cells of vital nutrients. Causes of cancer

60 Page60 o Carcinogens Physical, chemical, and biological agents that cause cancer Example - ionizing radiations (X-rays and gamma rays), non-ionizing radiations (UV) o Oncogenic (cancer-causing) viruses They have viral oncogenes (cancer-causing genes). o Sometimes normal genes in our body called proto-oncogenes get converted into cellular oncogenes that cause cancer. Diagnosing cancer o Biopsy and histopathological studies o Biopsy Suspected tissue is cut into thin sections and examined microscopically o Radiography, CT scan (computed tomography), and MRI (Magnetic resonance imaging) are techniques of diagnosing cancers. o C T Scan 3-D imaging of internals of an organ is generated by X-rays. o MRI Scan Pathological and physiological changes in a living tissue are detected by using magnetic fields and non-ionising radiations. o Immunological and molecular biological diagnostic techniques can all be used to detect cancers. o Identifying certain genes, which make an individual susceptible to cancers, can help to prevent cancers. Treatment of cancer o Radiotherapy Tumour cells are irradiated to death. Also, proper care is taken for protecting surrounding normal tissues. o Chemotherapy Drugs specific for particular tumours are used to kill cancer cells. They have side effects such as hair loss, anaemia, etc. o Immunotherapy Biological response modifiers such as α- interferons are used. They activate the immune system of patient and helps in destroying the tumour. Commonly Abused Drugs Opioids (Heroin) Cannabinoids Cocaine Source: Acetylation of morphine extracted from the latex of poppy plants (Papaver somniferum) Consumed by: Snorting or injection Properties: White, bitter and odourless Mode of action: Binds to opioid receptors present in the CNS and GI tract Effect: It is a depressant; slows down body functions Source: Inflorescences of the plant Cannabis sativa Consumed by: Inhalation or oral ingestion Mode of action: Binds to cannabinoid receptors present in the brain Effect: Affects the cardiovascular system Source: Coca plant Erythroxylum coca, found in South America Consumed by: Snorting Mode of action: Interference with transfer of neurotransmitter, dopamine Effect: Stimulates the CNS, producing a sense of euphoria and increased energy; excessive dosages cause hallucination Drugs Normally Used as Medicines Nicotine Drugs like barbiturates, amphetamines, benzodiazepines, LSD (Lysergic acid diethyl amides) are used as medicines to help patients with mental illness and insomnia. Morphine: It is a pain killer which is used for patients who have undergone surgery, but it is also abused. Present in tobacco, which is smoked, chewed or snuffed Mode of action: Stimulates the adrenal gland to release adrenaline and nor-adrenaline Effect: Increases blood pressure and heart rate

61 Page61 Ill Effects of Smoking Increased risk of diseases like bronchitis, emphysema, coronary heart disease, gastric ulcer and cancer (throat, lung and urinary bladder) Increased carbon monoxide levels in blood, leading to oxygen deficiency Alcohol / Drug Abuse Causes of alcohol/ Drug Abuse Alcohol / drug abuse normally starts in adolescence (period between yrs transition phase between childhood and adulthood). Many adolescents are motivated towards drugs/ alcohol due to curiosity and experimentation. Peer pressure, academic stress, unstable family structure further incline youth towards alcohol/ drug abuse. Perception of consuming alcohol / drug being cool and progressive and use of alcohol/drug in television, movies, etc. further promote this habit. Alcohol/ Drug Addiction When a person uses alcohol/ drug repeatedly, he becomes addicted. Addiction refers to psychological attachment to certain effects such as euphoria and temporary feeling of well-being associated with use of alcohol or drugs. In addiction, tolerance level of receptors present in our body increases towards the drug. This drives the person to use them even when they are not required or when they tend to harm his health / family life. Subsequently, the user runs into a vicious circle of addiction and subsequent dependence. Dependence leads to manifestation of withdrawal syndrome on discontinuation of use. Withdrawal syndrome Anxiety, nausea, sweating, shakiness, and sometimes may be lethal Effects of Alcohol/ Drug Abuse Immediate effect Vandalism, violence, and reckless behaviour Drop in academic performance, lack of interest in personal hygiene, rebellious behaviour, and change in eating and sleeping patterns, weight and appetite fluctuations Mental, psychological, and financial loss not only to the user, but also to his family Those who take drugs intravenously have a high risk of acquiring deadly diseases such as AIDS and hepatitis B. Damage to nervous system and liver (cirrhosis) Use of anabolic steroids by sportsperson have adverse effects: o In females Increase of masculinity, aggressiveness, depression, abnormal menstrual cycle, facial hair growth, enlargement of clitoris, and deepening of voice o In males Acne, aggressiveness, depression, reduction in size of testicles, decreased sperm production, enlargement of prostate gland, breast enlargement, premature baldness Ultimately, prolonged use of alcohol/drugs leads to coma and death. Preventing Alcohol/ Drug Abuse It is better to prevent the inclination of an individual towards alcohol/ drugs right from adolescence. Some of the ways of prevention are: o Avoid peer pressure Understand the unique personality and capabilities of a child o Education and counselling A child must be taught to accept success and failure equally. Especially during adolescence, he must be inclined towards constructive activities such as music, yoga, sports, reading based on his interest. o Help from parents and peers This includes proper guidance, advice, and trust to overcome problems such as stress and guilt. o Identifying danger signals If any sign of symptom of alcohol / drug abuse is seen in the adolescent by family or friends, then it should not be ignored because prevention is better than cure. Seeking medical help Psychologists and rehabilitation programs surely help an addict. Medical help should be sought to prevent further damage.

62 Page62 STRATEGIES FOR ENHANCEMENT IN FOOD PRODUCTION Animal Husbandry Introduction The practice of breeding and raising livestock is called animal husbandry. It includes breeding of livestock (cows, buffaloes, pigs, etc.), poultry farming, and fisheries. Farm Management Dairy Farm Management o Milk yield is dependent upon the quality of breed selected. Quality encompasses yielding potential and disease resistance. o Care of cattle Proper accommodation, adequate water, feeding in a scientific manner (quality of fodder), hygiene, visits by a veterinary doctor o All these processes nowadays have become mechanised and proper record keeping is followed. Dairy Farm Management o Poultry includes meat from birds such as chicken, ducks, and turkey. o The main emphasis in poultry farming is selection of a disease-free and healthy breed. o Safe farm conditions, proper feed, water, and hygiene are also necessary. Animal Breeding Breed A group of animals related by descent and similar in most characters such as general appearance, features, size, etc. Aims of breeding: o To increase yield of animals o To improve desirable qualities in produce Breeding is of two types inbreeding and out-breeding. Inbreeding o Mating of more closely related individuals of same breed for four generations o Superior females and superior males are identified and mated. o Superior females Produce more milk per lactation o Superior males Give rise to a superior progeny o Inbreeding increases homozygosity. It evolves a pure line. o It accumulates superior genes, but also threatens to accumulate harmful recessive genes o Continuous inbreeding may reduce fertility and productivity. This problem is called inbreeding depression. o Out-breeding provides a solution to inbreeding depression. Out-breeding It includes out-crossing, cross-breeding, and interspecific hybridisation. o Out-crossing It is the mating between animals of same breed, but not having common ancestors for 4 5 generations. It is usually used for animals, which have below average productivity and growth rate. o Cross-breeding It is the mating between superior male of one breed with superior female of another breed. Superior qualities of both the breeds combine and this is known as hybrid vigour. The progeny so formed is called hybrid. A hybrid may be used as it is or may be further subjected to inbreeding. Example: Hisardale sheep is a hybrid of Bikaneri ewes and Marino rams. o Interspecific Hybridization Males and females of different, but related species are mated. Progeny has desirable features of both the species. Example Mule is an interspecific hybrid of donkey and horse. Controlled Breeding Techniques

63 Page63 Apiculture Fisheries Artificial Insemination Semen is collected from the male and injected into the reproductive tract of the female. Semen can be frozen for later use or used immediately. Multiple Ovulation Embryo Transfer (MOET) Technology o Cow is administered with FSH-like hormone, which induces follicular maturity and super ovulation. o In super ovulation, instead of one egg/cycle, 6 8 eggs are produced per cycle. o The cow is either naturally mated with a superior bull or artificially inseminated. o Fertilized egg is recovered at 8 32 cell stages non-surgically and transferred to a surrogate mother. o Using this technique, high milk-yielding breeds of females and lean meat-yielding bulls have been bred successfully. Apiculture is the practice of bee-keeping. It includes maintenance of beehives for production of honey. Uses of apiculture: o Honey has a high nutritive value and medicinal value. o Honeybees also produce beeswax that is used in preparation of polishes and cosmetics. o Most commonly reared species of honeybee is Apis indica. Bee-keeping is not labour intensive. It is relatively easy, but requires some specialized knowledge about o nature and habits of bees o selection of suitable location for keeping beehives o catching and hiving of swarms o beehive management during different seasons o handling and collection of honey and beeswax Include catching, processing, and selling of fishes, shellfishes, and other aquatic animals (prawn, crab, lobster, etc.) Edible freshwater fishes Catla and Rohu Edible Marine fishes Hilsa, pomfrets, and sardines Aquaculture and pisciculture are the technologies to commercially rear fishes. The fisheries industry is flourishing in our country and Blue Revolution is on the verge of being implemented. Plant Breeding What is Plant Breeding? It is the purposeful manipulation of plant species in order to create desired plant types which are better suited for cultivation, give better yields, and are disease resistant. Classical plant breeding: It includes crossing of superior pure lines and selection of plants with desired characteristics. Modern plant breeding: It includes the use of molecular biology and genetics. Desirable plant traits wished to be incorporated by plant breeding o Increased crop yield o Improved quality o Tolerance to environmental stresses o Pathogen resistance o Tolerance to insects and pests Steps Involved in Breeding a New Genetic Variety of a Crop Collection of genetic variability o Genetic variability is availed from the wild relatives of the crop. o Hence, all the wild varieties and relatives of the crop are collected and preserved. o The natural genes available in a population are utilised by this method.

64 Page64 o Entire collection of plants/seeds (wild types/relatives) of the given crop, which has all the diverse alleles for all genes, is called germplasm collection. Evaluation and selection of parents o From the available genetic variability, the germplasm is analysed and evaluated to identify the plants with desirable traits. Crop hybridisation among selected parents o Two selected parents are crossed (hybridised). This facilitates the combination of desired traits from two different plants. o Pollen grains from one plant are dusted over the stigma of the other plant. Selection of superior recombinants o Among the hybrid progeny, those plants are selected which have the desired character combination. o Careful scientific evaluation of progeny is required for selection. o This step yields the plant that is superior to both the parents. Testing, release and commercialisation o Selected yields are evaluated for traits like quality, disease resistance, insect resistance, etc. o These crops are grown in research fields and their performance is recorded under ideal conditions. o This crop is then grown by farmers at several locations, for at least three growing seasons. o The crop is evaluated by comparing with the best available local crop cultivar (which acts as a reference). Indian Hybrid Crops Wheat and Rice Sugarcane Millets In 1960s, wheat and rice production increased tremendously. Norman E. Borlang developed semi-dwarf varieties of wheat. Sonalika and Kalyan sona are two of the hybrid wheat varieties grown in India. Semi-dwarf wheat varieties were taken from IR 86 (International Rice Research Institute) and Taichung native I (from Taiwan). Jaya and Ratna are the better-yielding, semi-dwarf rice varieties that were later introduced. Saccharum barberi is a native of North India and S. officinarum belongs to South India. S. officinarum has thicker stems and higher sugar content, but it does not grow well in North India. These two varieties were crossed to get the desirable qualities of both (Higher sugar content, thicker stems and the ability to grow in North India). Hybrid maize, jowar and bajra have been successfully developed in India. These varieties are high yielding and resistant to water stress. Applications of Plant Breeding If resistance to a particular disease is already present in a plant, it reduces the dependence of the plant on fungicides and bacteriocides. Before breeding, one must know the causative agent of a disease, and its mode of transmission. Some common diseases: o Fungal brown rust of wheat, red rot of sugarcane and late blight of potato o Bacterial black rot of crucifers o Viral tobacco mosaic Disease resistance can be provided by conventional breeding, mutational breeding or genetic engineering. Conventional breeding: It includes the basic steps of screening, germplasm, hybridisation, selection, testing and release. o Example wheat variety, Himgiri (resistant to leaf/stripe rust and hill bunt) and Brassica variety, Pusa swarnim (resistant to white rust) are bred by conventional breeding. o One limitation of this method is that the genes for disease resistance are limited in number.

65 Page65 Mutational breeding:in this method, genetic variations are created, which then result in the creation of traits not found in the parental type. o Mutations are induced with the help of mutagens (like chemicals) or irradiation. o The plants in which the desired character (in this case, the desired resistance) has come through mutation are selected. Genetic engineering: o Certain wild varieties have disease-resistant characteristics, but they are low yielding. o Disease-resistant genes from such varieties are introduced in high-yielding varieties through recombinant DNA technology. o Example resistance to the yellow mosaic virus in bhindi was transferred from a wild species to produce a new disease-resistant variety of bhindi, Parbhani Kranti. Pest-Resistant Crops Certain morphological characters (like hairy leaves, solid stems of wheat) naturally provide resistance from insects and pests. Similarly, biochemical characters provide resistance from insects and pests. For example, the high aspartic acid and low nitrogen and sugar content in maize lead to resistance against maize stem borers. Such varieties are bred with non-resistant varieties to produce pest-resistant hybrids. Example Pusa Gaurav variety of Brassica is resistant to aphids. Improvement in Food Quality A large number of people all over the world suffer from micronutrient, protein and vitamin deficiencies (hidden hunger) since they cannot afford to buy food rich in these nutrients. Such deficiencies lead to diseases, mental retardation and reduced lifespan. An alternative to this problem is to breed crops that are rich in nutrients. This approach is called bio-fortification of crops. Objectives of bio-fortification are to improve o Protein content and quality o Oil content and quality o Vitamin content o Micronutrient and mineral content Examples o Maize hybrids developed in the year 2000 have twice the amount of lysine and tryptophan compared to other maize hybrids. o Atlas 66 (a wheat variety having higher protein content) Single-Cell Protein & Tissue Culture Single-Cell Protein (SCP) Single-cell protein means that microbes are used as a source of protein. Microorganisms, despite being very small, are capable of producing tonnes of proteins due to their higher rates of biomass production. Just like mushroom culture, it is expected that microbes will soon be accepted as a source of food. Presently, Spirulina, an alga is widely accepted as a source of SCP. It is economical and eco-friendly as well. It can be grown on economical substrates like waste water from potato processing plant, straw, molasses or even sewage. Tissue Culture Tissue culture is the process of developing a complete plant from a part of a plant. The plant part is called an explant. Explants can be grown in sterile conditions in special nutrient media to regenerate complete plants. Nutrient media contain a carbon source (such as sucrose), organic salts, vitamins, amino acids and phytohormones.

66 Page66 Hence, propagation is achieved for a large number of plants in a short duration. This process is called micropropagation. Somaclones All the plants obtained by tissue culture are called somaclones since they are genetically identical to each other as well as the parent plant. Somatic hybridisation It refers to the hybridisation of the somatic parts of two plants. Protoplasts are isolated and fused to get a hybrid protoplast, which grows further to form a new plant. This new plant is called a somatic hybrid. E.g., protoplasts of potato and tomato have been actually fused to form a Pomato, but this plant is not commercially viable. Applications of tissue culture o Many important plants like apple, banana and tomato have been grown on laboratory scale by using this method. o This method can be used to recover a healthy plant from a diseased plant. Example a plant inflicted with virus may not have virus in its apical and axillary meristems. Hence, these parts can be cultured to obtain a healthy plant.

67 Page67 MICROBES IN HUMAN WELFARE Microbes - Household and Industrial applications Household Applications Lactic acid bacteria (LAB) o Milk Curd o LAB produces acids that coagulate and partially digest milk proteins. o Small amount of curd that is added to the milk for curdling acts as an inoculum containing thousands of LABS, which further multiply. o LAB enhances the nutritional value of milk by increasing Vitamin B 12. o LAB present in stomach prevents infections. Fermentation o Dosaand idli dough is fermented by bacteria, which produces CO 2 gas and gives it a puffed-up appearance. o Dough used for making breads is fermented by baker s yeast (Saccharomyces cerevisiae). Toddy (a traditional drink from South India made by fermenting sap from palm trees) Cheese making o The bacterium Propionibacterium sharmanii is used in Swiss cheese to give it its characteristic holes by producing large amount of carbon dioxide. o Roquefort cheese is ripened by growing certain fungi on them to give them their specific flavour. Industrial applications For industrial purposes, microbes are grown in large vessels called fermentors. On industrial scale, fermented beverages, antibiotics, enzymes, and other bioactive molecules are prepared using microbes. Fermented beverages Saccharomyces cerevisiae, also called brewer s yeast, is used to prepare wine, beer, whisky, brandy, rum, etc. depending upon the type of raw material and processing. If fermented broth is distilled, then brandy and rum are produced while wine and beer are produced without distillation. Antibiotics o Certain microorganisms inhibit the growth of other microorganisms wherever they grow. o Antibiotics are chemical substances produced by certain microbes that kill or retard the growth of other microbes (disease-causing microbes). o Penicillin discovered by Alexander Fleming was the first antibiotic to be discovered. o Fleming discovered it by chance when he was working on the bacterium Staphylococcus. He discovered that growth of Staphylococcus ceases in the culture plates where Penicillium notatum was grown.

68 Page68 o Later on, its use as an effective antibiotic was established by Chain and Florey. Chemicals, enzymes, and bioactive agents Microorganism Substance produced Fungus Aspergillus niger Citric acid Bacterium Acetobacter aceti Acetic acid Bacterium Clostridium butylicum Butyric acid Bacterium Lactobacillus Lactic acid Yeast S.cerevisiae Ethanol Bacterium Streptococcus Streptokinase (used as a clot buster for removing clots from blood vessels of patients with myocardial infarction) Fungus Trichoderma polysporum Cyclosporin A (used as immune-suppressive agent in organ transplantation) Yeast Monascus purpureus Statins (lower blood cholesterol levels) Microbes: Applications in Sewage Treatment and Biogas Production Microbes in Sewage Treatment Sewage basically consists of human excreta. It may contain many microbes, which may be pathogenic also. Sewage disposal is a huge problem. It cannot be directly disposed into rivers and streams. Hence, it has to be treated first in sewage treatment plants (STPs). The heterotrophic microbes present in the sewage itself aid in its treatment. Treatment of sewage includes two stages primary treatment and secondary treatment. Primary Treatment Involves physical removal of particles by filtration and sedimentation o Initially, sequential filtration is used to remove floating debris. o Then, grit (soil + small pebbles) are removed by sedimentation. Solids that settle down form the sludge while the supernatant forms the effluent. o Effluent is taken for secondary treatment. Secondary Treatment o Effluent is passed to aeration tank Constant agitation Air pumped Vigorous growth of bacteria Floc formation Consumption of organic matter by bacteria Decrease in BOD

69 Page69 o BOD is the amount of oxygen required by bacteria to oxidise all the organic matter present in the effluent. o Naturally, if organic matter decreases BOD decreases Pollution decreases What is a floc? Floc = Bacteria + Fungal filaments (in a mesh-like structure) o When BOD and hence pollution is reduced, effluent is passed into a settling tank. Here, flocs settle down and it is known as Activated Sludge. o In anaerobic sludge digesters, anaerobic bacteria act on the activated sludge to produce biogas (CH 4, CO 2, H 2 S). o The effluent from secondary treatment plant is released into water bodies. o Microbial technology for sewage treatment is so effective that no human technology has been able to beat it till date. Microbes in Production of Biogas Microbes produce many gases during their metabolism. The type of gas produced depends upon the substrate they grow on and the type of microbe. Anaerobic bacteria usually produce methane along with CO 2 and H 2. Such bacteria are called methanogens.example - Methanobacterium Methanogens are commonly found in anaerobic sludge (as in sewage treatment) and in the rumen of cattle. In the rumen of cattle, these bacteria help in cellulose digestion. Hence, excreta of cattle (gobar) are rich in methanogens. Biogas is also called gobar gas. Biogas Plant Components of biogas plant: o Concrete tank Here, slurry of dung is fed. It is a feet deep tank. o Floating cover Placed on slurry; rises as the gas is produced o utlet It is connected to the pipe. o Pipe It supplies the biogas to nearby houses. o Outlet for spent slurry Spent slurry can be used as a fertiliser. Biogas plant is usually set up in rural areas since cow dung is available in abundance there. Biogas is used for cooking and lighting. Biogas technology in India is due to the efforts of: o IARI (Indian Agricultural Research Institute) o KVCI (Khadi and Village Industries Commission)

70 Page70 Microbes: Bio control Agents and Biofertilizers Microbes as Bio control Agents Chemical insecticides and pesticides are harmful as: o They kill the useful and harmful life forms indiscriminately. o They are toxic to human beings as well as in the long run. o If all insects of a particular species are killed, then the natural predator-prey relationship and food chains will get distorted. Hence, biological means to eradicate pests can be used. This requires knowledge of the life forms (predator + prey) that inhabit a particular area, their life cycles, and patterns of feeding and preferred habitats. Example Ladybirds and dragonflies are used to get rid of aphids and mosquitoes. Microbes can also act in the same manner. Bacillus thuringiensis (Bt) is used to control butterfly caterpillars. This bacterium is available in sachets as dried spores, which are sprayed on the crops. The spores get into the gut of the larvae and kill it while the other insects remain unperturbed. By methods of genetic engineering, the genes of B. thuringiensis responsible for killing the larvae have been incorporated into the plants. Cotton plant with Bt gene incorporated is called Bt-cotton. The fungus Trichoderma living in roots of plants acts as a bio control agent against several plant pathogens. Baculoviruses, particularly genus Nucleopolyhedrovirus,are also used as narrow spectrum insecticidal agents. Bio control agents are particularly useful when useful insects are required to be conserved under IPM (integrated pest management programmes). Microbes as bio-fertilizers Chemical fertilizers contribute to the pollution. Bio-fertilizers are organisms that enrich the nutrient quality of the soil. Many bacteria, fungi, and cyanobacteria act as biofertilizers. They act as bio-fertilizers by living in symbiotic association with root nodules of leguminous plants such as Rhizobuim. These bacteria fix atmospheric nitrogen and enrich the nitrogen content of soil. Fungi also form symbiotic associations with plants (Mycorrhiza) such as Glomus. They absorb phosphorus and pass it to plants. Cyanobacteria such as Nostoc, Anabaena, etc. also fix atmospheric nitrogen and act as bio-fertilizers especially in paddy fields UPSC EXCLUSIVE MAINS TEST SERIES BATCH Comprehensive checking of papers with due feedbacks. 2. Test discussion with good answers along with model answers circulation from candidates themselves. 3. Officer s feedback on test answers, writing sessions with officers in person via SKYPE etc. 4. Separate session for essay writing will be conducted which includes 4 essay test. 5. All UPSC like exams will be conducted which will have essay and full length comprehensive test which will make you ready for 6. ULTIMATE UPSC MAINS EXAM. 7. Total test-17 (9 modules + 4 comprehensive + 4 essays). We would be completing the test course 25 days prior to exam. Leaving aspirant enough time for revision. Following are the topics a candidate should study and represent answer as per requirement of General studies mains paper. OPEN SESSION **11th JUNE and 12th JUNE ANSWER WRITING WORKSHOP BY OFFICER REGISTER YOURSELF BY

71 Page71 BIOTECHNOLOGY: PRINCIPLES AND PROCESSES What is biotechnology? Biotechnology refers to the technology using biology, which has applications in agriculture, food processing industry, medicine diagnostics, bioremediation, waste treatment, and energy production. The European Federation of Biotechnology (EFB) defines biotechnology as the integration of natural science and organisms, cells, parts thereof and molecular analogues for products and services. Basis of Modern Biotechnology Genetic engineering Introduction of foreign genetic material (DNA/RNA) into the host s genome and altering its phenotype Aseptic techniques Involves maintenance of contamination-free ambience in chemical engineering processes for manufacture of products such as antibiotics, vaccines, etc.this is done so as to enable the growth of only desired microbes responsible for a bioprocess. Genetic Engineering Asexual reproduction preserves the genetic information while sexual reproduction preserves variations. Plant and animal hybridization procedures often result in introduction of undesirable genes along with desirable ones. Genetic engineering overcomes this limitation. Genetic engineering includes: o Creation of recombinant DNA o Gene cloning o Gene transfer into host organism The introduced piece of DNA does not replicate in the host unless it is integrated with the chromosome of host. For getting replicated, the foreign DNA must integrate into the host DNA sequence having origin of replication. When this integration occurs, foreign DNA is replicated and many copies are formed. This process is called cloning (the process of formation of multiple identical copies of DNA). Construction of a Recombinant DNA Plasmid (autonomously replicating, circular, extra-chromosomal DNA) is isolated. Plasmid DNA acts asa vector since it is used to transfer the piece of DNA attached to it to the host. Plasmid DNA also contains genes responsible for providing antibiotic resistance to the bacteria. Plasmid DNA was cut with a specific restriction enzyme ( molecular scissors that cut a DNA at specific locations). The DNA of interest (to be inserted) was also cut with the same restriction enzyme. The DNA of interest is hybridised with the plasmid with the help of DNA ligase to form a Recombinant DNA. Recombinant DNA is then transferred to a host such as E.coli, where it replicates by using the host s replicating machinery. When E.coli is cultured in a medium containing antibiotic, only cells containing recombinant DNA will be able to survive due to antibiotic resistance genes and one will be able to isolate the recombinants. Restriction Enzymes as Tools of RDT Restriction enzymes are specialised enzymes that recognise and cut a particular sequence of DNA. Nucleases are of two types: o Endonucleases Cut the DNA at specific positions within the DNA o Exonucleases Cut the DNA at the ends (Remove the nucleotides at the ends of the DNA) Every restriction enzyme identifies different sequences (Recognition sequences). Over 900 restriction enzymes have been isolated, all of which recognise different sequences.

72 Page72 Recognition sequences are pallindromic- Pallindromes are the sequence of base pairs that read same both backwards and forwards (i.e., same and direction). Example: Restriction enzymes cut a little away from the centre of pallindrome site, but between the same two bases on the opposite strands. As a result, overhangs (called sticky ends) are generated on each strand. Sticky ends form hydrogen bonds with their complementary counterparts with help of DNA ligases. All these processes form the basis of RDT. Naming restriction enzyme o I st letter Genus of the organism from which the enzyme is derived o II nd and III rd letters Species of the organism o IV th letter Name of the strain o Roman number Order of isolation E.g., In EcoRI Derived from E.coli, strain R. It is the I st to be discovered. Gel Electrophoresis The fragments obtained after cutting with restriction enzymes are separated by using gel electrophoresis.

73 Page73 Electric field is applied to the electrophoresis matrix (commonly agarose gel) and negatively charged DNA fragments move towards the anode. Fragments separate according to their size by the sieving properties of agarose gel. Smaller the fragment, farther it moves. Staining dyes such as ethidium bromide followed by exposure to UV radiations are used to visualise the DNA fragments. DNA fragments are visible as bright orange coloured bands in the agarose matrix. These bands are cut from the agarose gel and extracted from the gel piece (elution). DNA fragments are purified and these purified DNA fragments are used in constructing recombinant DNAs. Cloning vectors & host as tools of RDT Cloning Vectors Plasmids and bacteriophages are commonly used as cloning vectors. Both of these have the ability to replicate within the bacterial cells independent of the chromosomal DNA. Bacteriophages Have high copy number (of genome) within the bacterial cell Plasmids May have 1 2 copy number to copy number per cell If foreign DNA is linked to these vectors, then it is multiplied to the number equal to the copy number of vector. Features present in the vector itself help in the easy isolation of recombinants from the non-recombinants. Components of a plasmid cloning vector Origin of replication (ori) o Replication starts from ori. Any fragment of DNA when linked to ori can be made to replicate. o With the help of this, the genetic engineer may control copy number of the recombinant DNA. To recover a high number, suitable origin of replication must be chosen. Selectable marker o These genes help to select recombinants over non-recombinants. o Antibiotic resistance genes such as amp R (ampicillin resistant), tet R (tetracycline resistant) serve as selectable markers usually. Cloning sites o These sites refer to the recognition sites for restriction enzymes (such as EcoRI, Hind III, PvuI, BamHI, etc.) o These are the sites where restriction enzymes cut the DNA. o Cloning process becomes completed when more than one recognition sites are present. o Therefore, ligation is carried out only at the restriction sites present on the antibiotic resistance genes. How antibiotic resistance genes help in selecting recombinants? Suppose tet R gene has Bam HI recognition site. When BamHI is used for restriction, foreign DNA fragment is inserted within the tet R gene. Hence, tetracycline resistance is not present in the recombinants. Recombinants will grow on the media containing ampicillin, but will die on media containing tetracycline.

74 Page74 On the other hand, non-recombinants will grow on medium containing ampicillin as well as on medium containing tetracycline. In this way, antibiotic resistance gene helps in selecting transformants. Alternate selectable marker Other than antibiotic resistance genes, alternative markers can be used. One of them is gene coding for galactosidase. When foreign gene is inserted within -galactosidase gene, the enzyme -galactosidase gets inactivated (insertional inactivation). Then the bacteria are grown on a chromogenic substrate. Non-recombinants will produce blue-coloured colonies. Recombinants will produce colourless colonies. Cloning vectors for plants and animals Ti plasmid (tumour-inducing plasmid) refers to the plasmid of Agrobacterium tumefaciens. o A. tumefaciens is a plant pathogen. It produces tumours in the plants it infects. o Ti plasmid can be modified into a cloning vector by removing the genes responsible for pathogenicity. Retrovirus These are the viruses that infect animals. They produce cancers in animals. o Retroviruses can be disarmed to be used as a cloning vector. Competent host Competent host refers to the bacterial cells that have the ability to take up the vector (containing Recombinant DNA). Methods to introduce recombinant DNA into competent host: o Cells are treated with divalent cations (e.g. Ca 2+ ). Then, these cells are incubated with recombinant DNA on ice, followed by heat shock (at 42º), and then putting them back on ice. By this, bacteria are able to take up recombinant DNA. o Microinjection Recombinant DNA is directly injected into the nucleus of animal cell. o Biolistics (Gene Gun) Cells are bombarded with high velocity micro particles of gold or tungsten. o Disarmed vector as in case of A. tumefaciens and retrovirus Processes of RDT Isolation of Genetic Material (DNA) For the processes of RDT, DNA must be available in its pure form. First of all, cells are treated with specific chemicals to break open the cell to release cellular components such as DNA, RNA, proteins, etc. This is done by enzymes such as lysozymes (bacterial cell), cellulase (plant cell), and chitinase (fungal cell). Contaminants such as RNA and proteins are digested with the help of ribonucleases and proteases respectively. Addition of chilled ethanol ultimately precipitates out the purified DNA, which can be seen as collection of fine threads in the suspension. Cutting of DNA at Specific Locations DNA is cut into fragments with the help of restriction enzymes. Fragments generated after restriction are isolated with the help of gel electrophoresis. Recombinant DNA is obtained by hybridising gene of interest with vector, with the help of enzyme DNA ligase. Polymerase Chain Reaction (PCR) Recombinant DNA can be amplified by PCR. Several identical copies of it can be synthesised in vitro. Two sets of primers (chemically synthesised oligonucleotide stretches that are complementary to a region of DNA), enzyme DNA polymerase,and deoxynucleotides are added. PCR consists of 3 steps:

75 Page75 o o o Denaturation Double helical DNA is denatured by providing high temperature. DNA polymerase does not get degraded in such high temperatures since the DNA polymerase used in this reaction is thermostable as it is isolated from thermophilic bacteria, Thermus aquaticus (Taq). Extension Replication of DNA occurs in vitro. This cycle is repeated several times to generate up to 1 billion identical copies of the DNA. Insertion of Recombinant DNA into Competent Cells Insertion of recombinant DNA into host is done by several methods: o Transformation in case of bacteria o Disarmed vectors, biolistics, and micro-injections in case of plant and animal cells o The cells bearing recombinant DNA are selected because the recombinants exclusively have selectable marker present in them (similar to antibiotic resistance). Obtaining the Foreign Gene Product This is the stage for which the recombinant DNA was produced. The cell containing recombinant DNA will produce a novel protein product (desirable product/recombinant protein). For large scale production of the desirable product (antibiotics, vaccines, enzymes), optimum conditions are to be provided. Continuous culture Used culture media is drained from one side and fresh culture media is added from the other side. o Cells are kept throughout in their log/exponential phase. o Larger biomass is produced by this method leading to higher yield. Bioreactors Large vessels in which large volumes ( litres) of culture can be produced o Optimal growth conditions for microbes are present (temperature, ph, substrate, salts, vitamins, etc.).

76 Page76 o o A bioreactor has the following components - agitator system, oxygen delivery system, foam control system, temperature and ph control system, sampling ports. Downstream Processing Biosynthesis of many compounds such as enzymes, alcohols, and antibiotics take place within the bioreactor. The products so obtained are crude and require separation, purification, and finishing, which is done under downstream processing (DSP). DSP makes a crude bio product marketable. After proper separation and purification, preservatives are added and the finished product is made to undergo clinical trials and quality checks before being sent to market.

77 Page77 BIOTECHNOLOGY AND ITS APPLICATIONS Genetically Engineered Crops Bt Cotton Genetically engineered crops have desirable genes (as of insect/pest resistance, giving better yield) incorporated in them. Genetically modified crops have o more tolerance to abiotic stresses such as cold, drought, salinity, heat, etc. o insect/pest resistance o reduced post-harvest losses o efficient mineral usage by plants o enhanced nutritional value (e.g., Vitamin A rich rice) Bacillus thuringiensis is a bacterium that produces proteins to kill certain insects such as lepidopterans (armyworm), coleopterans (beetles), and dipterans (flies/ mosquitoes). B. thuringiensis produces a protein crystal containing a toxic protein (inactivated state). Inactivated toxin Activated toxin (gut of insect) Activated toxin binds to the epithelial cells in the midgut of insect and creates pores that cause lyses and swelling and eventually death of insect. This toxin is encoded by a gene called Cry in the bacterium. Genes encoded by Cry IAc and Cry II Ab control cotton bollworms and those encoded by Cry IAb control corn borer. Cry genes are introduced into the cotton plants to produce Bt cotton, which is an insect resistant variety of cotton. RNA Interference (RNAi) RNAi is a method adopted to prevent infestation of roots of tobacco plants by a nematode Meloidegyne incognitia. In RNAi, a complementary RNA binds to mrna to form a ds RNA, which cannot translate and hence, its expression is blocked (Silencing). This complementary mrna may come from o infection by RNA viruses o transposons (mobile genetic elements) RNAi exists naturally in eukaryotes as a method of cellular defence. Nematode specific genes (DNA) were introduced in the host plant. The introduced DNA forms both sense and anti-sense RNA. Two strands being complementary to each other bend and form ds RNA, leading to RNAi. mrna of nematode is silenced and the parasite cannot survive in the transgenic host. Applications of Biotechnology in Medicine Recombinant Therapeutics With the help of RDT, mass production of efficient therapeutic drugs can be accomplished. These are safe and do not induce unwanted immunological response. Genetically Engineered Insulin Insulin is in great demand due to increase in number of patients with adult onset diabetes. Insulin extracted from animal source (example, slaughtered cattle and pigs) induce allergy in humans. Insulin as a pro-enzyme consists of 3 peptide chains A, B, and C. Pro-enzyme insulin Mature insulin Mature insulin consists of only two peptide chains A and B. Both these chains were separately isolated and introduced in plasmids of E. coli to produce insulin chains.

78 Page78 Gene Therapy Separately produced chains A and B were extracted and combined by creating a disulphide bond to form mature human insulin. Gene therapy is an attempt to deal with genetic or congenital diseases. This aims at correction of a genetic defect by delivery of a normal gene into an individual or embryo to take over or compensate the function for a non-functional gene. The first disease to have a gene therapy is ADA (Adenosine deaminase) deficiency. In this, the gene coding for enzyme ADA gets deleted leading to deficiency of ADA and problems in immune system. ADA deficiency can also be treated with: o Bone marrow transplantation o Enzyme replacement therapy Gene therapy for ADA deficiency: o Lymphocytes isolated from patient s blood are cultured in-vitro. o Functional ADA cdna are then introduced into the cultured lymphocytes. o These lymphocytes are returned back to the patient s body. Lymphocytes are not immortal. Therefore, repeated infusion of genetically engineered lymphocytes is required. Permanent cure Introduction of gene isolated from bone marrow cells producing ADA into cells at early embryonic stages Molecular Diagnosis Recombinant DNA technologies, PCR, ELISA (enzyme linked immuno sorbent assay) are some of the technologies of molecular diagnosis. Early diagnosis of bacteria and virus in body, when the concentration is extremely low, can be done by PCR since it amplifies the DNA several folds. PCR is used to detect HIV virus in suspected AIDS patients and mutations in genes in suspected cancer patients. ELISA is based on antigen-antibody interactions. In the presence of an antigen, the antibody produced against it can be detected. Hybridisation with a radioactive probe In this approach, gene is hybridized with a radioactive probe and autoradiography is used for detection. The regions where mutation is present in the gene will not appear in the photographic film since probe will not be able to bind with that part. Transgenic Animals & Biopiracy Transgenic Animals Animals that have their DNA manipulated to possess or express an extra gene are called transgenic animals. Till date, transgenic rats, rabbits, pigs, sheep, cows, and fish have been produced. Reasons for Producing Transgenic Animals Study of normal physiology o Transgenic animals serve as models to study genetics, regulation and down regulation of genes, and their corresponding effects on physiology. o They give information about the biological role of a particular factor in the body. Study of diseases o They act as models to study genetic basis of diseases. o These studies aid in finding possible treatments of diseases. o Transgenic models exist of various human diseases such as cancer, cystic fibrosis, rheumatoid arthritis, Alzheimer s, etc. Biological products o Treatment of diseases often requires certain products that are expensive to make. o Transgenic animals can be produced that have genes, coding for that particular product.

79 Page79 o Example Human protein α-1-antitrypsim used to treat emphysema is isolated by this method. o In 1997, first transgenic cow Rosie produced human protein-enriched milk, which contained α- lactalbumin and was nutritionally more suitable for human babies. Vaccine safety tests o Transgenic mice are used to test vaccines for their safety before they are used for humans. o Example Transgenic mice are used to check polio vaccines. Chemical safety testing o Transgenic animals contain genes that make them more sensitive to toxic substances than nontransgenic. o Toxicity testing in such animals helps us to obtain results in less time. Ethical Issues Associated with Transgenic Animals Biopiracy Indian government has set up an organization GEAC (Genetic Engineering Approval Committee), which makes decisions regarding validity of GM research and its use for public utility. Modification which may result in the loss of biological significance of animals cannot go beyond regulation. Unpredictable results may be observed, if these organisms are introduced in natural ecosystem. Patents for transgenic varieties also create problems as many indigenous varieties are claimed by multinational companies as their own inventions. For example A new variety of Basmati was claimed by an American company through patenting. This new variety was actually derived by Indian farmers by crossing Indian Basmati with semi-dwarf varieties. Similarly Neem and turmeric, which have been used for ages in Indian medicines, are also matters of dispute for patent rights. Use of bio-resources by MNCs and other organisations without proper authorisation from countries and people concerned without compensatory payment Industrialized and developed nations are economically rich, but poor in biodiversity while opposite prevails for developing nations. Therefore, developed countries exploit traditional knowledge and resources of poor countries for commercialisation. This is a matter of injustice since inadequate compensation and benefit sharing is given to poor countries in return. Therefore, steps should be taken by developing countries to prevent this exploitation. The Indian parliament has recently introduced second amendment of Indian patents bill to deal with these issues.

80 Page80 ORGANISMS AND ENVIRONMENT Abiotic Factors Ecology deals with interactions among different organisms and their environment. Organisms get adapted to their environment for their survival and reproduction. The rotation of the earth about its axis brings about changes in the environment, leading to different seasons. This leads to the formation of various biomes such as desert, grassland, etc. Life not only exists in favourable habitats, but also in harsh and extreme conditions. The environment of an organism can be divided into: o Abiotic factors o Biotic factors Some of the major abiotic factors that interact with the organisms are: o Temperature It is the most relevant abiotic factor since all organisms require an optimum temperature for their metabolism and other body functions. Depending upon their ability to tolerate temperature range, organisms are of two types- stenothermal (restricted to a narrow range of temperature) and eurythermal (can tolerate a wide range of temperature). o Water Water also is a major influencing factor. Life on earth is impossible without water as it forms the major constituent of all living cells. In oceans where quantity of water is not a limitation, the quality of water becomes one. Depending upon the ability to tolerate salinity, organisms can be stenohaline (restricted to narrow range of salinity) and euryhaline (tolerant to wider range of salinity). o Soil The nature and composition of soil differs from one place to another depending upon the climate, weathering process, and soil development method. The characteristic features such as soil composition, grain size, percolation, water holding capacity, etc. determine the native of the organisms it can support. o Light The major source of light on earth is the Sun. Light is essential for plants to perform photosynthesis. Certain plants become adapted to perform photosynthesis under very low light since they are constantly overshadowed by tall trees. Many plants also depend on light for their flowering (photoperiodism). The availability of light on land is comparatively higher than that in water. Responses to Abiotic Factors Adaptations All organisms in order to sustain maximum functionality maintain a constant internal environment (homeostasis). An organism may adopt one of the following strategies for homeostasis: o Regulate Certain animals have the ability to maintain a constant temperature and a constant osmolarity to keep up their homeostasis. Mammals have a constant body temperature (37 C) irrespective of the outside temperature. In summers, to maintain the temperature, we sweat and in winters we shiver, which produces heat. o Conform Animals and plants except mammals do not have a constant body temperature and their body temperature changes in accordance with the outside temperature. Such organisms are called conformers. Conformers have not evolved. They have become regulators since regulation is energetically more expensive. o Migrate The organism can move temporarily from stressful habitats to more hospitable areas and return once the period changes. Birds can migrate from cold regions to relatively warmer regions during winter and vice-versa during summers. o Suspend Some organisms cease to be metabolically active during stressful period. They suspend all activity and enter a period of dormancy. For example Spores in bacteria and lower plants; and hibernation (winter sleep) and aestivation (summer sleep) in animals Similarly, zooplankton enter diapause, a stage of suspended development during unfavourable conditions.

81 Page81 Population Adaptations are certain characteristics that organisms develop in order to survive and reproduce better in their habitat. These adaptations can be physiological, behavioural, or morphological. Some of the adaptations are: o Desert plants have thick cuticle on their leaf surface and stomata arranged in deep pits to reduce water loss. Their special photosynthetic pathway CAM enables their stomata to remain closed during day time. Their leaves are reduced to spines and photosynthesis is carried out by flattened stems. o Animals of colder regions have shorter limbs and ears to minimise heat loss (Allen s rule) and the body is covered by thick fur to reduce the heat loss. Their body has a thick layer of fat (blubber) below their skin that acts as an insulator to minimise heat loss. o People living in high altitudes have high RBC production and increased breathing rates. o Some desert animals are capable of burrowing in order to escape the heat. In addition, some desert animals such as kangaroo rat are able to meet their water requirement through internal fat oxidation. They also have ability to concentrate their urine. It is a group of similar individuals living in a geographical area, sharing similar resources, and capable of interbreeding. Population has certain attributes, which individual organisms do not possess: o Birth rate per capita births o Death rate per capita deaths o Sex ratio Ratio of number of males to females in a population Age distribution o A population can be composed of individuals of different age groups. o Age distribution plot for a given population is given by the age pyramid. o The structure of the age pyramid determines the growth status of the population, whether it is growing, stable, or declining. Population size, more technically, is referred to as population density (N), which indicates the number of individuals inhabiting a particular niche. If the population is huge, then relative density is measured instead of absolute density whose measurement is time-consuming. Population Growth The size of a population is an ever-changing aspect since it depends upon availability of food, predation, weather conditions, etc. This gives us an idea whether a certain population is growing or declining. Some of the reasons for the increase or decrease in population: o Natality (B) Number of births during a given period in the given population o Mortality (D) Number of deaths during a given period in the given population o Immigration (I) Number of individuals of the same species who have come into the habitat from elsewhere during a given period o Emigration (E) Number of individuals of the same species who have left the habitat and gone elsewhere during a given period If N is the population at time t, then its density at t + 1 is N t + 1 = N t + *(B + I) (D + E)+

82 Page82 Growth Models Exponential Growth When the resources are unlimited, population tends to grow in an exponential pattern. o If the population size is N and the birth and death rates (not per capita) are b and d respectively, then increase or decrease in N at t (time period) is given by, dn /dt = (b d) N If (b d) = r, then dn/ dt = rn r is the intrinsic rate of natural increase. Or, N t = N 0 e rt Where, N t Population density at time t N 0 Population density at time 0 r Intrinsic rate of natural increase e Base of natural logarithms ( ) Logistic growth When the resources are limited leading to competition between individuals and survival of the fittest, the population tends to grow in a logistic manner. o In this kind of growth, there is an initial lag phase followed by acceleration or deceleration phases and finally asymptote, when it reaches its carrying capacity (K). o When N in relation to t is plotted, it results in a sigmoid curve called the Verhulst Pearl Logistic growth given by, N Population density at time t r Intrinsic rate of natural increase K Carrying capacity Life History Variations Populations tend to increase their reproductive fitness in order to survive better. This is known as Darwinian fitness (high r value). Some of the trends they follow in course of achieving this: o Some organisms breed only once in their lifetime. Example - Salmon, Bamboo o Some breed many times. Example - Birds, mammals o Some produce a large number of small-sized offsprings. Example - Oyster o Some produce small number of large-sized offsprings. Example - Birds, Mammals

83 Page83 Population Interactions A natural habitat consists of many organisms living together and these organisms communicate and interact with each other. For example, plants depend on insects for pollination. Interspecific interactions are interactions between two different species of organisms. They can be either beneficial or harmful to one or both partners. Interspecific interactions Predation It is beneficial to the predator while the prey is harmed. o It acts as a means of transfer of energy to the next higher trophic level and of maintaining balance in the ecosystem. o For plants, herbivores are predators and some plants produce secondary metabolites, thorns, or poisonous chemicals to ward off predators. o Similarly, animals also camouflage themselves to protect themselves from predators. Some preys are poisonous or distasteful (Monarch butterfly is highly distasteful because of a special chemical it acquires during its caterpillar stage by feeding on poisonous weeds) so as to avoid predators. Competition It occurs only in closely related species wherein they share the same type of habitat and food resources. o However, for competition to take place resources need not be always scarce and competition does not necessarily take place between same species. o In competition, the fitness of one species is significantly lower in presence of another species and survival of fittest ultimately takes place. o Gause s Competitive Exclusion Principle states that two closely related species competing for the same resource cannot co-exist indefinitely and the competitively inferior will be eliminated eventually. o Moreover, some species may develop mechanisms to facilitate their co-existence. Parasitism In this interaction, one of the partners is benefited because it resides outside or inside the body of the host and gets free accommodation and food while the host is affected due to loss of nutrients. o Parasites in nature have developed a wide variety of adaptations such as hooks and suckers for attachment, loss of digestive system, high reproducing capacity, etc. o Parasites can live either outside (ectoparasites) or inside (endoparasites) the body of the host organisms. o Brood parasitism is seen in birds in which the parasitic bird lays its egg in the nest of the unassuming host bird, which takes care of them until they hatch. For example, Koel lays its eggs in the nest of the crow. Commensalism In this interaction, one of the partners is benefited while the other is neither benefited nor harmed. For example, an orchid growing as an epiphyte on the mango tree The orchid gets support while the mango tree is unaffected. Mutualism or symbiosis In this interaction, both the partners are benefited. For example, lichens, interaction of algae and fungi, where both are benefited The fungi give support to the algae while the algae prepare the food for the fungi.

84 Page84 ECOSYSTEM Ecosystem is the interaction of living things among themselves and with their surrounding environment. There are two basic ecosystems terrestrial and aquatic. Structure of Ecosystem Productivity The interactions between the various biotic and abiotic factors of an ecosystem lead to the maintenance of the ecosystem. Stratification is the vertical distribution of the different species occupying the different levels. For example, trees occur at a higher level then shrubs. The various aspects taken into consideration to study the functioning of ecosystem are: o Productivity o Decomposition o Energy flow o Nutrient cycling A constant supply of sunlight is required for the proper functioning of any ecosystem. The amount of biomass produced per unit area over a time period by plants during photosynthesis is defined as the primary productivity. It is expressed as weight (g 2 ) or energy (Kcal m 2 ). Productivity can be mainly divided into gross primary productivity (GPP) and net primary productivity (NPP). GPP is the rate of production of organic matter during photosynthesis. NPP = GPP Respiratory losses (R) Secondary productivity is defined as the rate of formation of new organic matter by consumers. Primary productivity depends upon o type of plant species inhabiting a particular area o photosynthetic capacity of plants o nutrient availability Annual net productivity for whole biosphere is about 170 b tons of organic matter. Decomposition Energy Flow It is the process of breakdown of complex organic matter into inorganic substances such as carbon dioxide, water, nutrients, etc. Fragmentation Breaking down of detritus (dead plant and animal remains, faecal matter) into smaller particles by detritivores (decomposers) Leaching - Process by which these inorganic matters enter the soil Catabolism Process by which detritus is degraded into simpler inorganic substances by bacterial and fungal enzymes Humification Accumulation of humus in the soil. Humus is resistant to microbial action and decomposes at an extremely slow rate. It acts as a reservoir of nutrients. Mineralization Process by which humus further degrades to release minerals into the soil It is an oxygen consuming process and is controlled by the chemical composition of detritus and climatic conditions. Sun is the sole source of energy for all ecosystems on the earth. Plants and other photosynthetic organisms utilize less than 50% of the solar radiation known as the photosynthetically active radiation (PAR). In an ecosystem, plants are called producers and all animals depend upon the plants directly or indirectly for their food. Hence, they are known as consumers or heterotrophs.

85 Page85 The consumers can be further divided into primary consumers (herbivores), secondary consumers (primary carnivores), and tertiary consumers (secondary carnivores). Food chain The energy flow among the various constituent animals is known as the food chain. Food web The interconnection of the various food chains is called the food web. Trophic level Every organism occupies a specific level in their food chain known as the trophic level. Standing crop Each trophic level contains a certain amount of living material at a certain time known as the standing crop. The number of trophic levels in a food chain is restricted since the energy transfer follows the 10 percent law i.e., only 10% of the energy is transferred from a lower trophic level to a higher one. Ecological Pyramids The energy relationship between the different trophic levels is represented by the ecological pyramids. Their base represents the producers or the first trophic level while the apex represents the tertiary or top level consumer. Ecological pyramids are of 3 types: o Pyramid of number o Pyramid of biomass o Pyramid of energy In most ecosystems, the three pyramids are upright except in some cases: o The pyramid of biomass is inverted in an ocean ecosystem since a small standing crop of phytoplankton supports a large number of zooplankton. o The pyramid of number can be inverted when, say, a large tree is eaten by small insects. o However, the pyramid of energy is always upright. A trophic level represents a functional level and not a single species as such. Also, a single species may become a part of more than one trophic level in the same ecosystem at the same time depending upon the role it plays in the ecosystem. Limitations of ecological pyramids: o The ecological pyramids do not take into account the same species belonging to more than one trophic level. o It assumes a simple food chain that almost never exists in nature. It does not explain food webs. o Saprophytes are not given a place in ecological pyramids even though they play a vital role in ecosystem. Ecological Succession The composition of all ecosystems keeps on changing with change in their environment. These changes finally lead to the climax community. Climax community It is the community which is in equilibrium with its environment. Gradual and fairly predictable change in the species composition of a given area is called ecological succession. Sere(s) It is the sequence of communities that successively change in a given environment. The transitional communities are called seral stages or seral communities. Succession happens in areas where no life forms ever existed as in bare rocks, cool lava, etc. (primary succession), or in areas which have lost all life forms due to destructions and floods (secondary succession). Primary succession takes hundreds to thousands of years as developing soil on bare rocks is a slow process. Secondary succession is faster than primary succession since the nature does not have to start from scratch. During succession, any disturbances (natural/man-made) can convert a particular seral stage to an earlier one.

86 Page86 Hydrarch succession It takes place in wet areas and converts hydric conditions to mesic. Xerarch succession It takes place in dry areas and converts xeric conditions to mesic. Pioneer species These are the species that first invade a bare area. On land, these could be lichens that secrete enzymes to dissolve the rock surfaces for soil formation while in water, pioneer species could be phytoplanktons. The ultimate result of all successions is a climax community, a mesic. Nutrient Cycling Carbon Cycle The amount of nutrients present in the soil at a given time is known as the standing state. Nutrients are never lost from the ecosystem. They are only recycled from one state to another. The movement of nutrients through the various components of the ecosystem is called nutrient cycling or biogeochemical cycles. They are of two types: o Gaseous Reservoir for these types of cycles exist in the atmosphere. o Sedimentary Reservoir for these types of cycles exist in the earth s crust. About 49% of the dry weight of living organisms is made up of carbon. The ocean reserves and fossil fuels regulate the amount of CO 2 in the atmosphere. Plants absorb CO 2 from the atmosphere for photosynthesis, of which a certain amount is released back through respiratory activities. A major amount of CO 2 is contributed by the decomposers who contribute to the CO 2 pool by processing dead and decaying matter. The amount of CO 2 in the atmosphere has been increased considerably by human activities such as burning of fossil fuels, deforestation. Phosphorus Cycle Phosphorus is an important constituent of cell membranes, nucleic acids, and cellular energy transfer systems. Rocks contain phosphorus in the form of phosphate. When rocks are weathered, some of the phosphate gets dissolved in the soil solution and is absorbed by plants. The consumers get their phosphorus from the plants. Phosphorus returns back to the soil by the action of phosphate-solubilising bacteria on dead organisms.

87 Page87 BIODIVERSITY AND CONSERVATION Biodiversity occurs not only in the species level, but also in the macromolecular levels. Biodiversity as described by Edward Wilson is the combined diversity at all levels of biological organisation. The most important forms of biodiversity are: o Genetic diversity (diversity at the genetic level) o Species diversity (diversity at the species level) o Ecological diversity (diversity at the ecosystem level) There are close to 1.5 million plants and animals that have to be discovered and described. More species have been discovered in temperate regions as compared to tropics. According to an estimate made by Robert May, global species biodiversity is about 7 million. Of the total species discovered so far, 70% are animals and 22% are plants. Of the animals, 70% are insects. India has 2.4% of the world s land and 8.1% of the total species diversity. According to May s estimate, 78% of the biodiversity is still to be discovered. Applying this to India s biodiversity figures, there still is a scope for discovery of over 1 lakh species of plants and 3 lakh species of animals. Patterns of Biodiversity Latitudinal gradients The plants and animals are not distributed evenly worldwide. The diversity of living forms decreases as we go from the equator towards the poles. A huge amount of plants and animals are concentrated in the tropical region because of the following reasons. Tropical environment is less seasonal and almost constant and predictable as compared to temperate environment. Tropics receive the major part of the solar energy, which contributes to great productivity. Speciation is dependent upon time. Tropical areas have remained undisturbed for millions of years unlike temperate regions, which have experienced frequent glaciations in the past. Species-Area relationships Alexander von Humboldt observed that biodiversity increases with increase in explored area. This relationship can be given by, log S = log C + Z log A Where, S = Species richness A = Area Z = Slope of the line (regression co-efficient) C = Y-intercept Value of Z is found to lie in the range of 0.1 to 0.2 for comparatively smaller areas such as countries while for very large areas such as entire continents, the slope of the line is much steeper with Z value lying from 0.6 to 1.2. Importance of biodiversity & Loss of Biodiversity What is the importance of biodiversity on the Earth? There is no exact answer to this question, but experiments conducted by many ecologists have demonstrated that a system with greater biodiversity is more stable and has greater productivity. In the long run, biodiversity is related with overall health of our ecosystem and survival of human race on the earth. Characteristics of a stable community: o It should not show much variation in productivity from year to year. o It must be either resistant or resilient to occasional disturbances. o It must be resistant to invasion by alien species. Loss of Biodiversity

88 Page88 Due to human activities, the natural wealth is getting lost rapidly. The last 20 years have seen the loss of 27 species. Some of the causes of this loss are: o Habitat loss and fragmentation This is the major cause for loss of biodiversity. Habitat destruction is caused by human activities such as deforestation and increasing pollution, leading to the loss of many plants and animals. o Over-exploitation Humans due to their greed and increased exploitation of natural resources have contributed to the endangerment of commercially important species of plants and animals. Example Species such as Steller s sea cow and passenger pigeon have been extinct due to over exploitation by humans. o Alien-species invasion The unintentional or deliberate introduction of alien species causes the declination of the indigenous species. Example Nile perch introduced in Lake Victoria led to the extinction of more than 200 species of cichlid fish in the lake. o Co-extinction When a plant or animal becomes extinct, another plant or animal which is dependent on it in an obligatory way also becomes extinct. Example In case of plant-pollinator mutualism, the extinction of one partner will eventually lead to the extinction of other also. Biodiversity Conservation Biodiversity conservation is necessary because of the following reasons: o Many commercially important products are obtained by nature such as food, fibre, wood, and countless industrial products. o Certain activities and products cannot be accomplished without the help of nature such as production of oxygen and pollination. o Intangible benefits such as aesthetic pleasure are derived from nature. o Conserving the species we share our planet with and passing the rich legacy of biodiversity to our future generations is our ethical duty. Biodiversity can be conserved by: o In-situ conservation - In order to conserve biodiversity better, some of the world s biodiversity hotspots (with high degree of biodiversity and endemism) have been identified and are protected. In India, biosphere reserves, wildlife sanctuaries, and national parks are built for this purpose. o Ex-situ conservation - The threatened species of plants and animals are taken out of their habitats and are kept in special settings as in zoological parks, botanical gardens, and wildlife parks. Nowadays, the gametes of endangered species can be preserved viable by methods such as cryopreservation and can be fertilized in-vitro followed by propagation through tissue culture methods. Similarly, seeds can be preserved in seed banks.

89 Page89 ENVIRONMENTAL ISSUES Pollution is the undesirable change brought about by chemical, particulate matter, or biological materials to air, water, or soil. Air Pollution Air is a complex, dynamic natural entity, which is essential for supporting life on earth. Air pollutant is a substance that causes harm to the humans and other living organisms. Some of the common pollutants of air: o Nitrogen dioxide o Sulphur dioxide o Carbon monoxide and carbon dioxide o Volatile organic compounds o Particulate matter Control of Air Pollution Air pollution causes severe respiratory disorders in humans and other animals and also affects plants. It can be controlled by the following ways: o Fitting smokestacks and smelters, with filters to separate pollutants from the harmless gases o Particulate matter can be removed by using an electrostatic precipitator. It contains electrode wires maintained at several thousand volts, which produce electrons. These electrons cling on to dust particles and give them a net negative charge and are attracted by collecting plates, which are grounded. The velocity of air passing through the plates should be low enough to allow the dust to fall. o A scrubber can be used to remove gases such as SO 2 wherein the exhaust passes through a spray of water or lime.

90 Page90 o o Vehicular pollution can be reduced by using less polluting fuels such as CNG, which is more efficient and less costly as compared to petrol or diesel. In 2002, all the buses were switched to CNG in Delhi and this has indeed led to a fall in pollution levels in the city. Vehicles can be fitted with catalytic converters that have metals such as platinum, palladium, and rhodium as catalysts. These catalysts carry out the following conversions: Unburnt hydrocarbons CO 2 and H 2 O Carbon monoxide Carbon dioxide Nitric oxide Nitrogen gas Unleaded petrol must be used with catalytic converters as presence of lead in the petrol inactivates the catalyst. Greenhouse Effect It is a natural phenomenon that keeps the earth s atmosphere warm. o Without this phenomenon, the temperature of the earth would become too cold for living beings to survive. o The greenhouse gases (CO 2, methane, etc.) absorb the heat of sun and the earth and emit it back to the earth s surface. o Thus, these gases prevent a part of heat rays from escaping into atmosphere. o This cycle is repeated many times to maintain the earth s temperature to an optimum 15ºC. The concentration of these gases has increased due to increased industrialisation, leading to the heating up of the earth s surface (global warming). This has increased the overall temperature of the earth, resulting in changes in the earth s climate. During the last century, the temperature of earth has increased by 0.6ºC. This increase in temperature is ultimately believed to cause the melting of polar ice caps, rise in the sea level, and submerging of the coastal areas. Greenhouse effect can be controlled by reducing the use of fossil fuels, which produce greenhouse gases on burning, afforestation, efficient energy usage, etc. Water Pollution Water is very essential for the maintenance of life on earth. Due to human activities, water bodies have become polluted all over the world. Some of the common pollutants and their sources are: o Domestic sewage It mainly contains organic matter, which is biodegradable. Microorganisms involved in their degradation consume a lot of oxygen and the BOD of the water body increases leading to the death of fishes and other aquatic life. Sewage also contains many pathogenic microbes, which may cause the outbreak of many diseases such as typhoid, jaundice, etc. o Industrial Effluents Industrial effluents contain inorganic toxic substances, which may undergo biomagnification (increase in concentration of a toxin at successive trophic levels). The toxin gets accumulated in the body of an organism and is passed on to the next level. For example, DDT and other heavy metals such as mercury, cadmium, etc. o Thermal wastewater discharge Heated water flowing out of the thermal power plants increase the temperature of the water body. It eliminates the cold water species and promotes the warm water species. In the long run, it causes damage to the indigenous biodiversity of the water body. Eutrophication o It is the ageing of a water body due to nutrient enrichment of its water. It can be natural or artificial. o The natural process takes thousands of years, but due to human activities, this process has got accelerated (accelerated/cultural eutrophication). o Release of nutrient rich sewage and industrial effluents lead to introduction of nutrients such as nitrogen and phosphorus and increase in temperature and BOD of the water body, causing increased biological activity, thereby leading to algal blooms. This results in the loss of indigenous flora and fauna. o In some cases, large masses of floating plants (bog) develop, finally converting the water body into land.

91 Page91 Control of Water Pollution Solid Waste Raw sewage can be treated using biological and other means to remove the solid, suspended, and inorganic materials before it is released back into the environment. Nitrogenous fertilizers can be denitrified using microbes, which can convert nitrate and nitrite into gaseous nitrogen by a process called de-nitrification. Integrated wastewater management as practiced in Arcata, California- In this approach, the water is first treated by conventional means such as filtration, sedimentation, and chlorine treatment, followed by bioremediation. (Marshes having appropriate plants, bacteria, fungi, and algae were seeded, which assimilate dangerous pollutants such as heavy metals) Consists of all the unwanted undesired materials thrown into the dustbin It may be composed of biodegradable or non-biodegradable wastes. Open dumps used for disposing solid waste serves as breeding ground for rats and flies. Therefore, sanitary landfills are used as a substitute for these. Biodegradable wastes can be either aerobically on anaerobically broken down using microbes. The nonbiodegradable waste can be recycled, reused, or dumped in landfills. Hospital wastes also contain hazardous materials, which have to be disposed properly. Hospital wastes are generally incinerated. Irreparable computers and other electronic goods make up e-wastes, which are either dumped in land fills or are incinerated. E-waste can be recycled also to recover metals such as copper, iron, silicon, gold, etc. To use the plastic waste in an efficient way, polyblend, a fine powder of recycled modified plastic, has been developed. When polyblend is mixed with bitumen, it can be used to lay roads with greater water repellent capacity and greater life. Agrochemicals and Radioactive Wastes Agrochemicals The increased use of pesticides, fertilizers for increasing the produce has led to eutrophication and biomagnifications in water sources. In order to check this, the concept of organic farming is increasingly becoming popular. In this technique, instead of using chemical fertilizers and pesticides, natural materials and techniques such as organic manure (cow dung manure), compost, biological pest control, and crop rotation are used. This leads to a balanced soil, which does not cause soil infertility, but causes the rejuvenation of the soil. Radioactive Wastes Nuclear energy is a non-polluting energy except the threats posed by accidental leakage and difficult disposal of radioactive waste. Radioactive substances cause severe damages such as mutations and cancer in lower doses and higher doses can be lethal. Radioactive wastes should be suitably pre-treated in shielded containers buried under rock surfaces about 500 m under the earth s surface. Improper Utilisation of Resources Natural resources can get degraded by their improper use. o Soil erosion and desertification Over-cultivation, overgrazing, deforestation, and poor irrigation techniques lead to soil erosion and desertification. o Water logging and soil salinity - Lack of proper drainage leads to water logging, which affects the crops and also leads to increase in the salinity of the soil. Ozone Depletion and Deforestation Ozone Depletion The ozone layer is found in the upper part of the stratosphere.

92 Page92 Deforestation It protects the earth from the harmful UV rays of the Sun. High energy UV rays break the bonds within the molecules such as DNA and proteins. Ozone is formed by the action of UV rays on oxygen molecule and its thickness is measured in Dobson units (DU). The ozone layer is getting depleted by the action of chlorofluorocarbons (CFCs) found in refrigerants and perfumes. The CFCs are acted upon by UV rays in the stratosphere, liberating the Cl atoms, which act as catalysts to degrade ozone into molecular oxygen. The ozone depletion is particularly greater in Antarctica, resulting in the formation of a large thinned ozone layer commonly known as ozone hole. The UV rays of shorter wavelength cause skin cancers, mutations in the cellular DNA, snow-blindness, cataract, etc. To check this ozone depletion, Montreal Protocol was passed in 1987 to control the use of substances that cause ozone depletion. It is the unlimited cutting of trees and conversion of forests into cultivable land. In the beginning of 20 th century, India had 30% of its area under forests, which was reduced to just 19.4% by the end of 20 th century. Deforestation is a result of a number of human activities such as increased population and the demand for land. Trees are cut for timber, fuel, and also for Slash and burn agriculture, also called Jhum cultivation. In this, trees are cut and plant remains in the forest are burned since the ash acts as a fertilizer. Some of the major effects of deforestation are the increase in carbon-dioxide levels, loss of habitat for wild animals, soil erosion, and consequent desertification. Deforestation can be controlled by reforestation and afforestation. In 1980s, the concept of Joint Forest Management was introduced by the government of India. In this, support of local communities was taken for conservation of forests and in return, the local people were free to use the products obtained from the forests.