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How do Organisms, Reproduce?, , CHAPTER, , 8, , Recap Notes, Reproduction is the production of new, organisms from the existing organism of a, species that ensures continuity of population, of that species., X Types, of reproduction : Living, organisms reproduce by two ways-asexual, reproduction and sexual reproduction., X Asexual reproduction : It involves the, production of an offspring from a single, parent without the fusion of gametes., , X, , Basic features of asexual reproduction:, – Only one organism is involved; different, sexes are not involved., – All the cell divisions during this type, of reproduction are either mitotic or, amitotic., – New, individuals, produced, are, genetically identical to the parents., – It is a rapid mode of multiplication., – No gametes are formed and hence no, fertilisation takes place., , Asexual reproduction, , Fission, , Fragmentation, , A fully grown parent (unicellular organism) divides into two, or more daughter cells., , Parent body breaks into two or more fragments and each, fragment develops into a new organism, e.g., sponges, sea, anemones, starfish, etc., , Binary, , Division of parent body into, two equal and identical, daughter cells. Occurs under, favourable conditions. E.g.,, Amoeba, Paramecium, etc., , Multiple, , Many, individuals, are, formed from a single parent., Occurs under unfavourable, conditions., E.g.,, Amoeba,, Plasmodium, Monocystis, etc., , Spore formation, , Spore is microscopic unicellular reproductive structure that, germinates to produce new individuals after detaching from, the parent body, e.g., Rhizopus, Penicillium., Natural methods, , Propagation by roots, e.g., Dalbergia, Dahlia, sweet potato, etc., Propagation by stems:, Rhizome – Banana, ginger ; Bulb – Onion, garlic, Tuber – Potato, artichoke, Runner – Oxalis, Cyanodon, Corm – Colocasia, Propagation by buds on leaves, e.g., Bryophyllum, Begonia, etc., Micropropagation/ Tissue culture, , Production of large number of plants by cell or tissue culture, technique, e.g., commercial production of orchids, carnation,, Chrysanthemum, etc., , Regeneration, , Formation of whole organism from a small body fragment or, repair of the damaged cells, tissues or replacement of damaged, parts of body. E.g., Hydra, Planaria, lizard, etc., Budding, , Formation of new individual from small outgrowth called bud,, on the parent body, e.g., Hydra, yeast, etc., Vegetative propagation, , Formation of new plant from the parts like stem, root and, leaves of an existing plant., Artificial methods, Cutting, , Cutting of small pieces of stem, root or leaf having a bud to, grow new plant when put in soil, e.g., rose, sugarcane, etc., Layering, , A branch of plant is lowered and burried into soil to induce, adventitious root formation and then cut from parent plant,, e.g., jasmine, Hibiscus, etc., Grafting, , Method of obtaining superior quality plant from two different, plants by taking root system of one plant (stock) and shoot, system of another plant (scion), e.g., mango, apple, rubber, etc., , Flow chart: Types of asexual reproduction

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43, , How do Organisms Reproduce?, X, , X, , Sexual Reproduction : It may be, defined as the production of offspring, (new individuals) by the fusion of two, gametes (usually one from male parent, and the other from female parent) to form, a diploid zygote which develops into a, mature organism., – Advantages of sexual reproduction over, asexual reproduction are : (i) Fusion of, male and female gametes coming from, male and female organisms. Since the, fusing gametes come from two different, and sexually distinct individuals,, the offsprings exhibit diversity of, characters, and (ii) Meiosis during, gametogenesis provides opportunities, for new combination of genes. It plays, a prominent role in the origin of new, species and leads to variation required, for evolution., Sexual reproduction in flowering, plants : The reproductive part of, angiosperms is called flower., – Sepals are green while petals are, coloured. They form the non-essential, parts of flower., – Stamens and carpels are the essential, reproductive parts of the flower., – Stamen (androecium) is the male, reproductive part of the plant made, up of filament and anther. Anther, produces the pollen grains that contain, male gametes., – Carpel (gynoecium) is the female, reproductive part made up of stigma,, style and ovary. Stigma is responsible, for receiving pollen during pollination., Style is the middle part of carpel. It is, an elongated tubular structure which, connects stigma with ovary. The basal, swollen part of carpel is ovary. Each, ovule has an embryo sac that bears a, haploid egg (female gamete)., – The process of transfer of pollen grains, from the anther of a flower to the stigma, of the same flower or another flower is, known as pollination. It is of two types, - self pollination that takes place in, same flower (bisexual)or between two, flowers of the same plant and cross, pollination which takes place between, , X, , X, , X, , X, , X, , two flowers of different plants of same, species. Insects (entomophily), wind, (anemophily), water (hydrophily),, birds (ornithophily), etc., are the, various pollinating agents., After pollination, pollen grain on the, stigma germinates and grows a pollen, tube downwards through style to the, ovary. Two non-motile male gametes are, formed inside the tube during its growth, through the style., After reaching the ovary, pollen tube, enters the ovule through the micropyle., The tip of the tube finally pierces the, micropylar end of the embryo sac and, ruptures releasing two male gametes, into the embryo sac. During the act of, fertilisation, one male gamete fuses with, the egg to form the diploid zygote. The, process is called syngamy (or generative, fertilisation). The diploid zygote finally, develops into an embryo. The other, male gamete fuses with the two polar, nuclei to form the triploid (3n) primary, endosperm nucleus. The process is called, triple fusion (or vegetative fertilisation)., This mechanism involving two acts of, fertilisation in an embryo sac is called, double fertilisation., The ovary of flower develops into a fruit., Ovule gets converted into a seed on, maturation., Seeds, germinate, under, suitable, conditions such as optimum moisture,, air and warmth, etc., into a seedling and, eventually into a new plant., Sexual reproduction in human, beings : Human beings are unisexual, and there is a distinct sexual dimorphism., The reproductive systems of males and, females consist of many organs which, are distinguishable into primary and, secondary sex organs. The primary sex, organs are gonads, which produce gametes, (or sex cells) and secrete sex hormones., The secondary sex organs include, the genital ducts and glands which, help in transportation of gametes and, reproductive process., – The period of sexual maturity during, adolescence when reproductive organs

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44, , X, , become functional is called puberty., – Puberty is characterised by :, – Development of secondary sex organs, and secondary sex characters in both, male and female., In males :, – Enlargement of penis and scrotum., – Broadening of the shoulders and, increased muscle development., – Enlargement of larynx and thickening, of vocal cords producing deepening of, the voice., – Growth of pubic hair and extra hair, , X, , on the face, in the armpits and on the, chest., In female :, – Growth of breasts and external, genitalia (vulva)., – Growth of pubic hair and extra hair in, armpits., – Hair on beard, moustache and chest, are lacking., – Broadening of pelvis., – Initiation, of, menstruation, and, ovulation., , Male reproductive system, , Testes, , One pair, present outside the abdominal cavity within scrotal sacs which keep the, testicular temperature 2° - 3° C lower than that of normal body temperature. It is the site of, production of male gametes called sperms and also secretes a hormone called testosterone., Vas deferens, , Long, tubular structure present in pair that carries sperms to the seminal vesicles that, temporarily store sperm. Vas deferens along with seminal vesicle opens into ejaculatory, duct which leads to urethra., Urethra, , Common pathway for the flow of urine and semen, arises from the urinary bladder and is, joined by ejaculatory duct. Runs through the penis and opens outside through male genital, pore., Penis, , Long, thick muscular organ having erectile tissues. Tip of penis is called glans penis (soft, and highly sensitive), covered by foreskin., It is a copulatory organ which transfers semen into vagina of female during sexual, intercourse., Accessory reproductive glands, , Seminal vesicles : One pair, sac like, present between rectum and urinary bladder, and secrete mucus and alkaline watery fluid that contains fructose (source of energy for, sperms) which helps in the movement of sperms., Prostate gland : Single, large, surrounds urethra, secretes milky fluid into urethra that, helps sperms to swim., Bulbourethral or Cowper’s glands : One pair, very small, present at both sides, of urethra, secrete mucus to lubricate the end of penis and secrete alkaline fluid that, neutralises the acids from the urine., Flow chart : Male reproductive system

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45, , How do Organisms Reproduce?, Female reproductive system, , Ovaries, Paired, almond shaped, present in the lower abdominal cavity near kidneys, connected by, ligament to the uterus., They are primary sex organs and perform two functions – production of female gametes, (eggs or ova) and secretion of female sex hormones (estrogen and progesterone). A mature, ovary contains a large number of ova in different stages of development., The formation of ova begins in female fetus before birth. At birth, each ovary contains, about 2-3 lakhs immature ova., One mature ovum is released from either of the ovary (ovulation) at the interval of every, 28 days during reproductive phase of a woman., Fallopian tubes (Oviducts), Paired tubes originating from uterus, on either side, extend upto the ovary of their, respective sides., Its terminal part is funnel-shaped with finger-like projections called fimbriae lying near, ovary. Fimbriae direct the ovum released from ovary into the Fallopian tube., Uterus, Single, inverted pear-shaped, highly muscular, hollow structure present in the pelvic, cavity, lying between urinary bladder and rectum., Development of fetus occurs inside it, hence called womb. The narrower lower part of, uterus is called cervix, which leads into vagina., Vagina, About 7-10 cm long tube where penis discharges sperms., Vagina acts as the passage for menstrual flow and also acts as birth canal during parturition, (child birth)., Flow chart : Female reproductive system, Menstrual cycle : Sexual cycle begins in a, female when she attains puberty. It occurs, under the control of sex hormones and repeats, every 28 days. It is marked by bleeding or, menstrual flow. A single egg is released, from either of the two ovaries and the inner, wall of uterus, endometrium, becomes, ready to receive it after fertilisation. If the, ovum gets fertilised by the sperm, a zygote, is formed and an embryo starts developing., Till the birth of the child, neither any egg is, released from ovary nor menstruation takes, place., , X, , X, , In the absence of fertilisation, the, egg is expelled through vagina along, with the bleeding caused by the, breaking of endometrium. This is called, menstruation. Menstruation usually, occurs 14 days after ovulation and lasts, for 3-5 days. After menstruation is over,, the endometrium gets repaired and uterus, once again becomes ready to receive the, next embryo., The first menstruation in a female’s life, is called menarche. The sexual cycle in, a woman continues upto the age of 45 to

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46, 55 years. The ovaries do not release any, further egg after that and this stage is, called menopause., Fertilisation : Fertilisation is internal, in human beings. The sperms produced in, testes of male are transferred into the vagina, of female during the intercourse. The ovum, released from ovary during ovulation is, swept into the adjacent Fallopian tube where, fertilisation takes place. Only one sperm, can enter into the ovum. Fusion of nucleus, of sperm and nucleus of ovum marks the, completion of fertilisation. It results in the, formation of single-celled zygote., Post fertilisation changes : The zygote, then undergoes repeated mitotic divisions to, form a blastula on the 7th day that descends, into uterus and gets implanted., X Specialised tissues of fetus and uterine, wall of the mother form a structure, called placenta. It is a mechanical and, physiological connection between an, embryo and uterine wall of the mother, through which nutrients and other useful, substances enter fetus from mother’s, blood and waste products are expelled, into mother’s blood., X The complete development of fetus, from, the initial stage of conception till the birth, of the young one, is called gestation., It is completed in about 280 days or, 40 weeks from the first day of the last, menstruation. Gestation is followed by, parturition (birth of child). Parturition, is the expulsion of fully formed young, one from the mother’s uterus after the, gestation period is over. It starts with, contraction of uterine wall under the, influence of oxytocin hormone. Relaxin, hormone from the ovary widens the pelvis, and vagina for child birth., Reproductive health : Reproductive, health is a total well-being in all aspects of, reproduction, i.e., physical, emotional, social, and behavioural., X Some of its problems and strategies are :, – Increasing population and methods to, check it, – Knowledge of reproductive organs, sex, education and sexually transmitted, , diseases (STDs), – Awareness about birth control devices, – Care of mother and child, – Prevention of sex abuse and sex-related, crimes., Population control : Continuous increase, in population may cause scarcity of food,, other natural resources, proper housing, and medical care, etc. Frequent pregnancies, also deteriorate mother’s health therefore,, regulation of conception is required., Preventive measures to avoid the pregnancy, are called contraception. Some of the, contraceptive methods are :, – Barrier methods : Physical devices, that prevent the entry of sperms into, vagina during copulation. They also, protect individuals from STDs., (a) Condoms or Nirodh – Thin rubber, tube worn over the penis., (b) Femidom – Thin rubber tube that, fits inside vagina., , –, , –, , –, , –, , (c) Diaphragm or Cervical cap –, Rubber cover that fits over the, cervix in vagina., Chemical methods : Spermicide, creams and jellies are applied in vagina, to immobilise or kill the sperms. Oral, contraceptive pills contain hormones, like estrogen and progesterone that, prevent ovulation., Intrauterine contraceptive devices, (IUCDs) : These are contraceptive, devices made of copper, plastic or, stainless steel. These include Copper-T, (CuT), Lippes’ loop, etc. A CuT is, inserted into uterus by a doctor, or a skilled nurse. They prevent, implantation in uterus., Natural methods : These include, rhythm method (avoid copulation, around the time of ovulation) and, coitus interruptus (withdrawal of penis, before ejaculation)., Surgical methods (Sterilisation) :, (a) Vasectomy : Procedure done, on males involving removal of a, small portion of the vas deferens, and ligation of two cut ends with

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47, , How do Organisms Reproduce?, , threads to prevent the sperms from, coming out., , X, , X, , (b) Tubectomy : Procedure done, on females involving removal of, a small portion of the Fallopian, tubes and ligation of cut ends with, threads to prevent the egg (ovum), to enter the uterus., Female to male ratio is declining due to, sex determination done by amniocentesis, or radio imaging techniques that are, legally banned by government., Abortion is the medical termination, of pregnancy (MTP) before the fetus, becomes viable. It is suggested by doctor, incase of complicated pregnancies which, are dangerous for the mother or fetus, or both. However, this method is widely, misused by people who do not want a, female child., , Sexually Transmitted Diseases : These, are infectious (communicable) diseases, caused by bacteria, protozoa and viruses, which spread from an infected person, to a healthy person by sexual contact., Human beings suffer from over 30 different, kinds of sexually transmitted diseases, (STDs). The common STDs are:, X Gonorrhoea is caused by a bacterium, Neisseria gonorrhoeae. Infection results in, inflammation of the mucous membrane of, the urinogenital tract, rectum, throat and, , X, , X, , eye. The victim feels burning sensation, and pain during urination. It spreads, by sexual contact and through infected, clothes. Penicillin and ampicillin are used, for its cure., Syphilis is caused by bacterium,, Treponema pallidum which affects the, mucous membrane of genital, rectal, and oral regions and causes lesions., Infection occurs by sexual intercourse,, and occasionally by kissing or close body, contact. Antibiotics such as penicillin, and tetracycline are used to cure it., AIDS (Acquired Immuno-Deficiency, Syndrome) : The disease AIDS is caused, by HIV virus. It is a fast spreading, incurable disease which weakens the, body’s immune system. It spreads by, unprotected sex, use of contaminated, needles, transfusion of infected blood,, etc. Few drugs like zidovudine or, azidothymidine are used to prolong, patients life., , Healthy Pregnancy : Malnutrition and, stress during pregnancy are the major causes, of ill health of pregnant women. Therefore it, is advisable that cigarette, LSD, marijuana, and alcohol should be avoided by the expecting, mothers as they cause harmful effects on the, fetus including mental retardation. Proper, spacing between subsequent pregnancies, should also be maintained for mothers to, regain their health.

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Practice Time, OBJECTIVE TYPE QUESTIONS, , Multiple Choice Questions (MCQs), 1. If there is no formation of egg cell during, the development of ovule, then after fertilisation, which of the following structure will not develop?, (a) Embryo, (b) Endosperm, (c) Seed, (d) Fruit, 2. Identify the parts labeled 1 and 2 in the, given figure., 1, 2, , (a), (b), (c), (d), , 1- micropyle, 2- epicotyl, 1- cotyledon, 2- embryo, 1-radicle , 2-plumule, 1-plumule, 2-radicle, , (b) Cotyledons store food., (c) Plumule develops into the root system., (d) Seeds contain the future plant called embryo., 6. Which of the following is not a surgical, method of birth control?, (i) Copper-T, (ii) Tubectomy, (iii) Vasectomy, (iv) Using condoms, (a) (i) and (iv), (b) Only (iv), (c) (ii), (iii) and (iv), (d) (i), (ii) and (iii), 7., (a), (c), (d), , IUCD is for, vegetative propagation (b), increasing fertility, avoiding miscarriage., , contraception, , 8. Which of the following diseases is transmitted, sexually?, (a) Sleeping sickness (b) Jaundice, (c) Elephantiasis, (d) Syphilis, , 3. Which of the following statements are, incorrect about puberty?, (i) Body shows starting of sexual maturity at, this stage., (ii) The rate of general body growth begins to, proceed faster as the reproductive tissues, begin to mature., (iii) Changes taking place in the body parts are, different in boys and girls., (iv) All the changes during puberty takes place, very fast., (a) (iii) and (iv), (b) (ii) and (iv), (c) (i), (ii) and (iii), (d) (i), (ii), (iii) and (iv), , 9. D N A c o p y i n g i s n e c e s s a r y d u r i n g, reproduction because, (a) it leads to the transmission of characters, from parents to offsprings, (b) it leads to variation, (c) it helps in survival of the species over time, (d) all of these., , Which of the following match is correct?, Cotyledon , – Food store, Plumule, _ Future shoot, Radicle, – Future root, All of these, , 11. The given figure shows the male reproductive, system in humans. Select the correct statements, regarding the given figure., , 4., (a), (b), (c), (d), , 5. Select the incorrect statement regarding, seeds., (a) Seeds have tough seed coat that protects, them from external environment., , 10. Which of the following is a sexually, transmitted viral disease?, (i) Gonorrhoea, (ii) Syphilis, (iii) Warts, (iv) HIV-AIDS, (a) (i), (iii) and (iv), (b) (ii) and (iv), (c) (iii) and (iv), (d) (i) and (ii), , R, , S, , P, T, Q

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49, , How do Organisms Reproduce?, , (i) Part labelled as Q produces the sperms., (ii) The hormone testosterone is produce in the, part labelled as S., (iii) Parts labelled as R and S produce secretions, that regulate the production of sperms., (iv) The part labelled as T is called vas deferens, which carries the sperms from testis to the, urethra., (v) Part labelled as P serves as the common, passage for both sperms and urine., (a) (i), (ii), (iii) and (v) (b) (iii), (iv) and (v), (c) (i), (iv) and (v), (d) (i), (iii) and (iv), 12., (a), (b), (c), (d), , Unisexual flowers contain, both stamen and carpel, only stamen, only carpel, either stamen or carpel., , 13. Sexual reproduction is the mode of, reproduction that, (i) depend on the involvement of two different, gametes., (ii) incorporates a process of combining DNA, from two gametes., (iii) gives better chances of variations as, compared to asexual reproduction., (iv) gives rise to genetically identical offspring., (a) (i) and (ii), (b) (i), (iii) and (iv), (c) (i), (ii) and (iv), (d) (i), (ii) and (iii), 14. The type of reproduction shown in the figure, is, , 16. The number of chromosomes in parents, and offsprings of a particular species remains, constant due to, (a) doubling of chromosomes before zygote, formation, (b) halving of chromosomes during gamete, formation, (c) doubling of chromosomes during gamete, formation, (d) halving of chromosomes after gamete, formation., 17. Which of the following is not a vegetative, propagule?, (a) Root, (b) Stem, (c) Leaf, (d) Seed, 18. Which of the following layers of uterus, breaks off during menstruation?, (a) Epimetrium, (b) Myometrium, (c) Endometrium, (d) Perimetrium, 19. Which of the following is celebrated as, “World AIDS Day”?, (a) September 1, (b) October 1, (c) November 1, (d) December 1, 20. Select the correct, Organism , (a) Bryophyllum –, (b) Hydra, –, (c) Paramecium –, (d) Spirogyra, –, , match., Mode of reproduction, Leaf bud, Binary fission, Multiple fission, Vegetative propagation, , 21. In humans, gestation is completed in, (a) 40 weeks, (b) 60 weeks, (c) 120 weeks, (d) 240 days., 22. Which of the following plants possess, unisexual flowers?, (a) Watermelon, (b) Hibiscus, (c) Mustard, (d) Both (b) and (c), (a) budding, (c) regeneration, , (b) agamogenesis, (d) fission., , 15. Factors responsible for the rapid spread of, bread mould on slices of bread are, (i) large number of spores, (ii) availability of moisture and nutrients in, bread, (iii) presence of tubular branched hyphae, (iv) formation of round shaped sporangia., Which of the above statements are true?, (a) (i) and (iii), (b) (ii) and (iv), (c) (i) and (ii), (d) (iii) and (iv), , 23. Which of the following is the correct sequence, regarding sexual reproduction in a flowering, plant?, (a) Pollination, fertilisation, seedling, embryo, (b) Seedling, embryo, fertilisation, pollination, (c) Pollination, fertilisation, embryo, seedling, (d) Embryo, seedling, pollination, fertilisation, 24. Which of the following organisms does not, depend on reproduction to exchange genetic, material?, (a) Lion, (b) Papaya, (c) Bacterium, (d) Cockroach

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50, 25. ––––––– is the portion on which grafting is, done and it provides the roots., (a) Stock, (b) Scion, (c) Bud, (d) None of these, 26. External fertilisation takes place in, (a) fish and frog, (b) frog and monkey, (c) dog and goat, (d) goat and fish., 27. Match the columns and select the correct, option from the given codes., Column I, Column II, A. Parturition (i) The act of expulsion of, fully grown foetus from, mother’s uterus, B. Menopause (ii) Release of one ovum from, one of the ovaries every, month, C. Gestation, (iii) Phase, during, which, menstruation ceases, D. Ovulation (iv) Complete development of, the fetus inside the womb, , (a), (b), (c), (d), , AAAA-, , (iv), B - (ii), C - (i), D - (iii), (i), B - (iii), C - (iv), D - (ii), (iv), B - (iii), C - (i), D - (ii), (i), B - (ii), C - (iv), D - (iii), , 28., (a), (b), (c), (d), , Tissue culture technique is used for, growing disease free plant, rapid multiplication of plant, multiplication of sterile plants, all of these., , 29. Human seminal plasma, the fluid part of, semen, is produced by contributions from which, of the given part?, A. Prostate gland, B. Bulbourethral gland, C. Urethra, D. Seminal vesicles, (a) A and D only, (b) A only, (c) A, B, C and D, (d) A, B and D only, 30., are, (a), (b), (c), (d), , Examples of vegetatively reproducing plants, , (a), (b), (c), (d), , By removing all the flowers of plant P, By removing all the anthers of all the flowers, By removing all the carpels of all the flowers, None of these, , tomato, okra, onion, cauliflower, potato, ginger, onion, sugarcane, cauliflower, onion, potato, tomato, okra, onion, ginger, sugarcane., , Case Based MCQs, Case I : Read the following passage and answer, questions from 31 to 35., P and Q are two monoecious plants. P bears, bisexual flowers whereas Q bears unisexual, flowers. P does not need a pollinating agent, whereas pollinating agent is required in case, of Q., 31. Select the option that correctly identifies, plant P and Q., (a) P - Papaya, Q - Marigold, (b) P - Pea, Q - Cucurbit, (c) P - Sunflower, Q - Orchid, (d) P - Tulip, Q - Daffodil, 32. Select the correct option regarding plants P, and Q., (a) Seed setting is assured in plant P even if all, its flowers are emasculated., (b) Male flowers of plant Q always open only, after the female flowers of the plant are, pollinated., (c) Female flowers of plant Q can reproduce by, cross pollens or self pollens depending upon, the genus to which plant Q belongs to., (d) P is a cross pollinated plant whereas Q is a, self pollinated plant., 33. How can self pollination be avoided in plant P?, , 34. Which of the following holds true for plant Q?, (a) Plant Q bears complete flowers., (b) Plant Q bears either male flowers or female, flowers but never both., (c) Sexual reproduction in plant Q may or may, not give rise to genetic variations., (d) All of these, 35. Select the correct statement., (a) Flowers of plant P produce large number of, pollen grains as compared to flowers of plant, Q., (b) Sexual reproduction in plant P does not, bring variations., (c) Sexual reproduction in plant P often gives, rise to new varieties due to accumulation of, genetic variations., (d) Both (a) and (b), Case II : Read the following passage and answer, questions from 36 to 40., X, Y and Z are three sexually transmitted, diseases (STDs). X and Z are caused by bacteria, whereas Y is caused by virus P. Virus P lowers the

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51, , How do Organisms Reproduce?, , immunity of a person and leads to an incurable, disease. X starts as painless sores on genitals, rectum or mouth. Z causes painful urination and, abnormal discharge from genitals., 36. Select the option that correctly identifies, disease X, Y and Z?, X, Y, Z, (a) AIDS, Syphilis, Gonorrhoea, (b) Syphilis, AIDS, Gonorrhoea, (c) Gonorrhoea Syphilis, AIDS, (d) Syphilis, Gonorrhoea, AIDS, 37., (a), (b), (c), (d), , Identify virus P from the given paragraph., Human papilloma virus, Human adenovirus, Human immunodeficiency virus, Human cytomegalovirus, , 38. What are the symptoms of disease Y?, (a) Weight loss, (b) Fever or night sweats, , (c) Fatigue and weakness infections, (d) All of these, 39. Select the incorrect statement regarding, diseases X and Y., (a) Both X and Y can spread from infected, mother to unborn baby during pregnancy., (b) Both X and Y can spread from infected partner, to healthy partner by unprotected sex., (c) Y can also spread through use of contaminated, needles and blood transfusion., (d) None of these, 40. How can disease Y be prevented?, (a) By following polygamy and having protected, sex., (b) Use of sterilised needles for injecting, medicines, blood tests, etc., (c) Collecting blood from unknown donors, without background check by blood bank, professionals., (d) All of these, , Assertion & Reasoning Based MCQs, For question numbers 41-50, a statement of assertion followed by a statement of reason is given. Choose the correct, answer out of the following choices., (a) Both assertion and reason are true, and reason is correct explanation of the assertion., (b) Both assertion and reason are true, but reason is not the correct explanation of the assertion., (c) Assertion is true, but reason is false., (d) Assertion is false, but reason is true., 41. Assertion : In human male, testes are extra, abdominal and lie in scrotal sacs., Reason : Scrotum acts as a thermoregulator, and keeps testicular temperature lower by 2°C, for normal spermatogenesis., 42. Assertion : Vagina acts as copulation canal, and fertilisation canal both., Reason : Insemination occurs in vagina of female., 43. Assertion : One pollen mother cell forms, four microspores., Reason : Microspores are formed due to, reduction division., 44. Assertion : Regeneration cannot be regarded, as reproduction., Reason : Most organism would not normally, depend on being cut up to be able to reproduce., 45. Assertion : Spores of Rhizopus can survive, under extreme climatic conditions., , Reason : Spores are the reproductive parts in, Rhizopus., 46. Assertion : Contraceptive pills can cause, side effects in females., Reason : They prevent pregnancy by blocking, the incoming sperms., 47. Assertion : Male gametes are motile., Reason : They are free-living diploid cells., 48. Assertion : Corolla is a floral part., Reason : It helps in pollination., 49. Assertion : The uterine line in human, females becomes thick and spongy every month., Reason : The lining breaks and comes out, through the vagina as blood and mucus if, fertilisation does not occur., 50. Assertion : Gametogenesis is the production, of gametes through the meiosis., Reason : In oogenesis polar bodies are formed.

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52, , SUBJECTIVE TYPE QUESTIONS, , Very Short Answer Type Questions (VSA), 1. What is the function of pollen grains in, flowers?, 2. What changes occur in the flower after, fertilisation?, 3. Mention any one limitation of vegetative, propagation., 4. Why is fertilisation in flowering plants not, possible without pollination?, 5., , Name the parts in human body where, , sperms and eggs are produced., 6. Why copper - T cannot protect a woman from, sexually transmitted diseases?, 7. Why is cell division considered as a type of, reproduction in unicellular organisms?, 8., , How regeneration is carried out?, , 9., , Name any two type of asexual reproduction., , 10. Name the parts of a bisexual flower that are, not directly involved in reproduction., , Short Answer Type Questions (SA-I), 11. Some flowers of pumpkin and bottle gourd, develop fruits whereas other flowers fail to, develop fruits. What may be the possible reason?, , 16. Pollination brings male gamete in close, proximity to the female reproductive part., Justify the statement., , 12. Give reasons for the following :, (i) Oral pills help in birth control., (ii) Petals of flowers are variously coloured., , 17. How Spirogyra reproduces?, , 13. How population growth can be prevented?, , 19. Why do multicellular organisms use complex, way of reproduction?, , 14. State two differences between budding in, Hydra and budding in yeast., 15. Do you think sex-education is necessary in, schools?, , 18. How do insects help in pollination?, , 20. Describe the role of prostate gland, seminal, vesicle and testes in the human male reproductive, system., , Short Answer Type Questions (SA-II), 21. Why is variation so important?, 22. Name and explain in brief the four different, methods of contraception., 23. List two functions each of the following parts, of human female reproductive system., (a) Ovaries (b) Fallopian tubes (c) Uterus, , 26. Answer the following., (a) What happens to the zygote after fertilisation, in flowering plants?, (b) What is germination?, (c) Identify the labelled parts A, B and C of the, given figure., , 24. What happens when the egg is not fertilised, in human females?, 25. Label the parts ‘A’, ‘B’, ‘C’, ‘D’, ‘E’ and ‘F’ in, the following figure. Assign the role played by, ‘B’ and ‘F’., , A, C, , B, , 27. What does HIV stands for? Is AIDS an, infectious disease? List any four modes of, spreading AIDS., 28. What is vegetative propagation? How does, vegetative propagation take place in potato?, Embryosac, , 29. (a) Why has Government of India prohibited, prenatal sex determination by law? State its

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53, , How do Organisms Reproduce?, , benefits in the long run., (b) Unsafe sexual act can lead to various, infections. Name two bacterial and two viral, infections caused due to unsafe sex., 30. (a) List few disadvantages of vegetative, propagation?, (b) What is placenta? Explain its functions in, humans., 31. Reproduction is linked to stability of, population of a species. Justify the statement., , 32. Differentiate between natural and artificial, vegetative propagation in plants., 33. Suppose there is no meiosis and the, gametes are formed by mitotic divisions. What, kind of situation do you expect under such, circumstances?, 34. Write a short note on tissue culture., 35. Why does the body show sexual maturation, at puberty?, , Long Answer Type Questions (LA), 36. Describe the structure of human male, reproductive system. Write down the role of, each part., 37. What is the significance of sexual mode of, reproduction?, 38. Answer the following., , OBJECTIVE TYPE QUESTIONS, 1. (a) : In ovule, a male gamete fuses with egg cell to, form zygote. The zygote develops into multicellular embryo, by repeated cell divisions. Hence, if egg cell will be absent, in ovule, then embryo will not formed., 2., , (d) : In the given figure 1 is plumule and 2 is radicle., , 3. (b) : During puberty a whole new set of changes occurs, that cannot be explained simply as body enlargement. All of, these changes take place slowly, over a period of months, and years and the rate of general body growth begins to, slow down, while reproductive tissues begin to mature., 4. (d) : Cotyledon- food store; plumule-future shoot;, Radicle - Future root, 5., , (c) : Plumule develops into the shoot system., , 6. (a) : Both copper-T and condoms provide mechanical, barrier for the sperms so that they cannot reach to the, uterus., 7. (b) : Intrauterine Contraceptive Device (IUCD) is for, contraception. It is inserted into the uterus by a doctor, where it prevents implantation of the embryo., 8. (d) : Syphilis is a sexually transmitted disease which is, caused by a bacterium, Treponema pallidum. It affects the, genital, rectal and oral regions causing lesions., , (a) G i v e r e a s o n s f o r a v o i d i n g f r e q u e n t, pregnancies by women., (b) E x p l a i n t h e f o l l o w i n g m e t h o d s o f, contraception giving one example of each., (i) Barrier method, (ii) Chemical method, (iii) Surgical method, , 9. (d) : DNA copying is important for reproduction., Additional copies of DNA are made during replication, which, is necessary for the new cells formed after cell division., Moreover, minor alternations during the process of DNA, copying result in the production of variations. Such variations, are useful for the survival of species over time., 10. (c) : Many diseases can be sexually transmitted. These, include bacterial infections such as gonorrhoea and syphilis,, and viral infections such as warts and HIV-AIDS., 11. (c) : Here the parts labelled as P, Q, R, S and T are, penis, testis, prostate gland, seminal vesicle and vas deferens,, respectively., The testes of man produce sperms from puberty onwards,, throughout his life. The testes also produce the male sex, hormone-testosterone. The function of seminal vesicle is to, produce viscous fluid which stimulates uterine contraction to, help sperms move forward into the Fallopian tube of female., Through small ducts, prostate gland pours its secretion into, urethra. Prostate gland secretes milky fluid which helps in, the mobility of sperms., Vas Deferens is a straight tube which carries the sperms, to the seminal vesicles. Penis is a long and thick muscular, organ made up of mostly erectile tissue. Urethra carries urine, from the bladder as well as sperms from the vasa deferentia,, through the penis.

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54, 12. (d) : A flower which contains either stamen or carpel, is called a unisexual flower e.g., papaya and watermelon., 13. (d) : Sexual reproduction may be defined as the, production of offsprings (new individuals) by the fusion of, two gametes (usually one from male parent and the other, from female parent) to form a diploid zygote which develops, into a mature organism. The sexual mode of reproduction, incorporates such a process of combining DNA from two, different individuals during reproduction. It results in reestablishment of the number of chromosomes and the DNA, content in the new generation that leads to variation., 14. (c) : Regeneration is the formation of the whole body, of an organism from its own small fragment., 15. (c) : A spore is a single or several celled reproductive, structure that detaches from the parent and on getting, suitable medium like moisture and nutrients as in case, of bread mould, gives rise, directly or indirectly, to a new, individual., 16. (b) : Gametes formation involves meiosis or reduction, division. The gamete mother cell is diploid (2n), i.e., it has, two sets of chromosomes. This single diploid cell divides by, meiosis to form 4 haploid (n) daughter cells. Each daughter, cell becomes a gamete, either male or female. Each gamete, possesses single set of chromosomes. Fusion of these, gametes results in the formation of a zygote having a double, set of chromosomes i.e., diploid (2n) (one set of paternal and, the other set maternal). Thus the number of chromosomes, in parents and offsprings of a particular species remains, constant., 17. (d) : Vegetative reproduction or propagation in plants, is a method of asexual reproduction in which the plant parts, other than seeds are used as propagules. Among flowering, plants, every part of the body such as root, stem, leaf or bud, takes part in vegetative reproduction, e.g., in guava, buds, present on the roots can grow into leafy shoots., 18. (c) : Endometrium is the inner layer of the uterus which, is highly vascular and breaks off during menstruation., 19. (d) : December 1 is celebrated every year as the World, AIDS day to spread information about AIDS among the, public., 20. (a) : Buds produced in the notches along the leaf, margin of Bryophyllum fall on the soil and develop into new, plants., 21. (a) : In human females, gestation is completed in, about 280 days or 40 weeks from the first day of the last, menstruation., , 22. (a) : The flower may be unisexual (papaya, watermelon), when it contains either stamens or carpels, or bisexual, (Hibiscus, mustard) when it contains both stamens and, carpels., 23. (c) : During sexual reproduction in flowering plants,, first of all pollination occurs that brings pollen onto stigma, of flower. Pollen germinates to form pollen tube through, which male gamete reaches female gamete. Fertilisation, occurs resulting in zygote formation which later develops, into embryo. Embryo remains inside seed and on getting, favourable conditions germinate into seedling., 24. (c) : Bacterium does not depend on reproduction to, exchange genetic material., 25. (a) : Grafting is the method of obtaining a superior, quality plant from two different plants by taking the root, system of one plant and the shoot system of another. The, plant whose root system is taken is called stock while the, plant whose shoot system is taken is called scion., 26. (a) : External fertilisation is the fertilisation that takes, place outside the body of an organism. Aquatic organisms, experience this type of fertilisation, e.g., fish and frog in, which fertilisation takes place in water., 27. (b) : Release of mature ovum from the ovary is called, ovulation., The complete development of fetus, from the initial stage of, conception till the birth of the young one, is called gestation., Parturition is the act of expelling the full-term young one, from the mother’s uterus at the end of gestation., The sexual cycle in a woman continues upto the age of 45, to 55 years. After that the ovary becomes dormant and do, not release any further egg. This stage is called menopause., On the arrival of menopause, menstruation in female also, ceases to occur., 28. (d) : Tissue culture technique is useful in obtaining, virus free plants disease free plants homozygous diploids in, quick commercial propagation of plants and multiplication, of sterile plants., 29. (d) : Seminal plasma is a complex fluid comprised, of secretions from bulbourethral glands, seminal vesicles,, prostate gland and sperm from testes., 30. (b) : Vegetative reproduction in potato occurs by tuber,, in ginger by rhizome, in onion by bulb and in sugarcane by, stem cutting., 31. (b)   32. (c), 33. (b) : If anthers of flowers are removed then chances, of self pollination become negligible. Cross pollens can, be artificially dusted on stigmas of flower for cross, pollination.

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55, , How do Organisms Reproduce?, , 34. (c), 35. (b) : Self pollination does not bring about genetic, variations., 36. (b) : X could be Syphilis, Y could be AIDS and Z could, be gonorrhoea., 37. (c) : Human immunodeficiency virus (HIV) causes, immunodeficiency syndrome a condition characterised, by progressive failure of immune system allowing life, threatening conditions., 38. (d)    39. (d), 40. (b) : Sterilised needles are free from any kinds of, germs., 41. (a) : In males, testes are present outside the body, (extra abdominal) in the scrotal sacs. Spermatogenesis, takes place in testes. This process needs temperature 2°C, lower than the normal internal body temperature. The low, temperature is maintained by the scrotal sacs. The scrotal, sacs have muscles which constantly contract and relax the, loose scrotal skin. It helps to keep the testicular temperature, at 35°C. So scrotum acts as a thermoregulator and helps in, spermatogenesis., 42. (d) : Vagina is a muscular tube starting from the lower, end of uterus upto the outside. The vagina receives the male, penis during copulation. The great elasticity of its wall also, allows the passage of the baby during childbirth. Hence it, acts as copulatory as well as birth canal., Insemination is the process to introduce semen into the, vagina whereas the fusion of gametes occurs in the fallopian, tube., 43. (b) : The sporogenous cells of anther may directly, function as a microspore mother cells (also called pollen, mother cells or PMCs) or they may undergo a few mitosis to, add up to their number before entering meiosis. Each PMC,, by a meiotic division, gives rise to a group of four haploid, microspores. The aggregates of four microspores are referred, to as microspore tetrads., 44. (a) : Simple animals like Hydra and Planaria can be, cut into many number of pieces and each piece grows, into a complete organism. This is known as regeneration., Regeneration is carried out by specialised cells. These cells, proliferate and make large numbers of cells. From this, mass of cells, different cells undergo changes to become, various cell types and tissues. These changes take place in, an organised sequence referred to as development. However,, regeneration is not the same as reproduction, since most, organisms would not normally depend on being cut up to, be able to reproduce., , 45. (b) : The spores are covered by thick walls that protect, them until they come into contact with another moist surface, and can begin to grow. Thus, spores can survive under, extreme climatic conditions., 46. (c) : Oral pills are used to check ovulation. These are, mainly hormonal preparations and contain estrogen and, progesterone. They are called oral contraceptives. They, change the hormonal balance of the body so that eggs are, not released and fertilisation can not occur., 47. (c) : In humans, the female gametes are large as they, contain the food stores and the male gametes are small, and motile so that they can easily travel inside the female, reproductive system and reach the site of fertilisation. Male, gametes are haploid cells., 48. (b) : The corolla adds to the beauty of the flower and, is thus an adaptation to attract insects for pollination., 49. (b) : One egg is produced every month by one of the, ovaries. The uterus prepares itself every month to receive and, nurture the growing embryo. The lining thickens and is richly, supplied with blood to nourish the growing embryo. If the, egg is not fertilised, this lining is not needed any longer. So,, the lining slowly breaks and comes out through the vagina, as blood and mucous. This cycle takes place roughly every, month and is known as menstruation. It usually lasts for, about two to eight days., 50. (b) : Gametogenesis is the production of haploid, gametes by diploid multicellular organisms through the, process of meiosis. The production of female gametes or ova, (egg) is called oogenesis and the production of spermatozoa, (sperm) is called spermatogenesis. Oogenesis occurs within, the follicles of the ovaries. The meiosis of oocytes always, results in haploid cells of unequal size. When a primary, oocyte undergoes meiosis a large haploid secondary oocyte, and a very small first polar body are formed. A second, meiotic division produces a large ootid and very small second, polar body. The first polar body may or may not divide during, the second meiotic division into two additional second polar, bodies. All the polar bodies are nonfunctional., , SUBJECTIVE TYPE QUESTIONS, 1. Pollen grains produce male gametes which fertilise the, egg cell present in the ovule., 2. After fertilisation, the flower withers. The sepals and the, petals dry up, the ovary converts into fruit, the ovule forms, the seed and the zygote forms the embryo which is enclosed, in the seed.

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56, 3. One limitation of vegetative propagation is that it does, not show genetic variation., 4. Pollination allows pollen grains to reach carpel which, contains the egg. Thus, fertilisation which involves fusion of, male and female germ cells can occur only after pollination., 5. Sperms are produced in testes (males) and eggs are, produced in ovary (female)., 6. Copper-T is an intrauterine device which acts as, contraceptive but does not provide protection against, sexually transmitted diseases as it does not provide any, barrier against mixing of body fluids from two individuals., , 9. (i) Fragmentation, , (ii) Budding, , 10. The parts of a bisexual flower that are not directly, involved in reproduction are : sepals (calyx), petals (corolla), and thalamus., 11. Pumpkin and bottle gourd bear unisexual flowers. Some, flowers are male and others are female. Male flowers do, not develop fruits. They produce pollen grains. The female, flowers posses carpels which develop fruits after fertilisation., Therefore, only female flowers develop fruits but not the, males., , 7. Cell division results in the formation of two daughter, cells, i.e., it results in the production of more individuals of, the organism like the process of reproduction., , 12. (i) Oral pills contain the hormone estrogen and, progesterone which check ovulation., (ii) The petals of the flowers are coloured to attract, pollinators for cross pollination., , 8. Regeneration is carried out by specialised cells which, proliferate and make large numbers of cells. From this mass, of cells, different cells undergo changes to become various, cell types and tissues., , 13. Population growth can be prevented by family planning, programmes which involve various types of birth control, measures like mechanical, chemical, surgical and natural, methods., , 14. Differences between budding in Hydra and budding in yeast are as follows:, Budding in Hydra, , Budding in Yeast, , (i) Buds produced are multicellular., , Buds produced are unicellular., , (ii) Buds get detached from parent body soon., , Buds may remain attached to the parent body, Daughter buds, , Developing bud, , Tentacles, , Nucleus, New Hydra, , Developing, bud, , Body, A, , Parent Hydra, B, , C, , New Hydra, separated, from parent, , 15. A correct knowledge about reproductive organs,, adolescence related changes, sexually transmitted, diseases, etc., will save the young minds from myths and, misconceptions about sex related aspects and help them, to lead a reproductively healthy life. Thus, sex-education is, necessary in schools., 16. Pollination is the process of transfer of pollen grains, from the anther of a flower to the stigma of the same or, another flower. Pollen grains bear male gametes which are, carried to the ovary of a flower with the help of pollen tubes., Hence, pollination brings male gametes in close proximity to, the female reproductive part., 17. Spirogyra reproduces through the fragmentation, process., Fragmentation is the mode of reproduction in which, parent body breaks into two or more fragments and each, , A Vacuole B, , C, , D Mother E, cell, , fragment develops into a new individual. It is a method of, reproduction in many filamentous algae, mycelial fungi and, thalloid bryophytes., The given figure shows the process of fragmentation in, Spirogyra.

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How do Organisms Reproduce?, , 18. In entomophily (insect pollination), when an insect visits, a flower for nectar, the pollen grains get deposited on the, body of insect. When this insect visits another flower, some, of the pollen grains stick to stigma of another flower. This, leads to pollination., 19. In multicellular organisms, cells are organised into, specialised groups; tissues, organs or organ systems, each, of which occupy specific locations in the body. In such an, organised condition cell-by-cell division would be impossible., Hence, multicellular organisms need complex methods of, reproduction., 20. Prostate glands - Secretion of the prostate gland, nourishes and activates the spermatozoa to swim., Seminal Vesicles - They produce an alkaline secretion which, forms 60% of the volume of semen. Alkaline nature of the, removal fluid helps to neutralise the acidic environment of, the male urethra as well as that of female reproductive tract, which otherwise would inactive and kill sperms., Testes are responsible for producing sperm and secreting, male sex hormones e.g., testosterone., 21. Variation is so important because, (i) Populations of organisms normally live and interact with, definite kinds of ecological niches. If there is an alteration, in the ecological conditions of such places, the population, of organisms will get damaged and may be wiped out. The, variants of the organisms, however, may have better chances, of survival. The surviving individuals may reproduce and, develop a kind of population which is suited to the changed, niche., (ii) It makes some individuals better fitted in the struggle, of existence., (iii) It helps the individuals to adapt themselves according, to the changing environment., (iv) It allows breeders to improve races of useful plants and, animals for increase resistance, better yield, quicker growth, and lesser input., (v) Preadaptation caused by the presence of neutral, variations are extremely useful for survival against sudden, changes in environment e.g., resistance against a new, pesticide or antibiotic., (vi) It constitutes raw material for evolution., (vii) It gives each organism a distinct individuality., 22. Contraception literally means prevention of pregnancy., Different methods for the prevention of pregnancy are as, follow:, (i) Barrier methods in which a mechanical barrier such as, condom, cervical cap or diaphragm is used for preventing the, , 57, entry of sperms in the female genital tract or vagina. Thus,, sperms and egg do not meet and fertilisation is prevented, from taking place., (ii) Chemical methods of contraception are those in which, release of eggs from the ovary can be prevented by the, intake of pills by the female. The oral pills are hormonal, preparations and are also termed as oral contraceptives., (iii) Intra-Uterine Contraceptive Devices (IUCDs) are placed, in the uterus to prevent pregnancy. These devices are very, effective and popularly used by females. Copper-T and Lippes, Loop are examples of IUCDs. These devices are placed in the, uterus by skilled personnel., (iv) Surgical method : Contraception can also be brought, about by surgically removing or tying a part of vas deferens, (vasectomy) in the male and removing or tying a part of, fallopian tube (tubectomy) in the female. Surgery should be, performed by well trained doctors under sterile conditions., 23. , (a) Ovaries : (i) It produces ovum., (ii) It secretes female sex hormone., (b) Fallopian tubes : (i) It conveys the ovum from the ovary, to the uterus., (ii) It acts as site for fertilisation., (c) Uterus : (i) It nourishes the fertilised ovum which, develops into the fetus., (ii) It holds the fetus till the baby is mature enough for, birth., 24. One egg is produced every month by one of the ovaries., The uterus prepares itself every month to receive and nurture, the growing embryo. The lining thickens and is richly supplied, with blood to nourish the growing embryo. If the egg is not, fertilised, this lining is not needed any longer. So, the lining, slowly breaks and comes out through the vagina as blood, and mucus. This cycle takes place roughly every month and, is known as menstruation. It usually lasts for about two to, eight days., 25. In the given figure,, A  = Pollen grain, B  = Pollen tube, C  = Stigma, D  = Style, E  = Ovary, F  =, Ovule., Role of B : Pollen tube acts as carrier of male gametes to, the embryo sac., Role of F : Ovule becomes seed after fertilisation., 26. (a) After fertilisation, the zygote divides several times to, form an embryo within the ovule. The ovule develops a tough

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58, coat and is gradually converted into a seed. The ovary grows, rapidly and ripens to form a fruit. Meanwhile, the petals,, sepals, stamens, style and stigma may shrivel and fall off., (b) Germination is the process included all changes that, take place from the time when a dry, viable seed starts to, grow when placed under suitable condition of germination, to the time when the seedling becomes established on the, substratum., (c) A – Plumule, B – Radicle, C – Cotyledon, 27. HIV stands for Human Immunodeficiency Virus., Yes, AIDS is an infectious disease. It is transmitted sexually, or through exposure to contaminated blood., Four modes of spreading AIDS are :, (i) Unprotected sex with an infected partner, (ii) Use of contaminated needle and syringes, (iii) Use of contaminated razors for shaving, (iv) Transfusion of infected blood or blood products., 28. Vegetative propagation is the process of formation, of the plant from vegetative propagules or units, such as, stem, root, leaf, buds, etc. Tuber of potato is the swollen, underground stem and bears number of nodes or eyes. Each, eye bears one or many buds. New plants are produced from, the buds on the eyes of the stem tuber., 29. (a) Prenatal sex determination was banned in India in, 1994. This was done to prevent sex selective abortion. It is, being used to kill the normal female fetus. This killing of the, unborn girl child is called female feticide which is reducing, the number of girls drastically in some societies of our, country. Due to reckless female feticide, male–female sex, ratio is declining at an alarming rate. Its benefit in the long, run is that the female-male ratio could be maintained for a, healthy society., (b) Bacterial diseases due to unsafe sex are gonorrhoea,, syphilis., Viral diseases due to unsafe sex are AIDS, genital herpes., 30. (a) Some disadvantages of vegetative propagation are:, (i) Plants produced by this technique possess less vigour., (ii) They are more prone to diseases., (iii) They show no genetic variations., (b) Placenta is a specialised tissue between fetus and, uterine wall of mother. It develops finger-like processes, called villi, which grows into tissue of the uterus., Functions of placenta are listed below :, (i) Provides nutrition, (ii) Helps in the exchange of gases such as oxygen and, carbon dioxide, (iii) Helps in the excretion, that is the removal of nitrogenous, waste material from the fetal blood to that of the mother., , (iv) It secretes hormones such as estrogen and progesterone., (v) Placenta provides protection by partitioning the blood, of the fetus and the mother. Thus, unwanted materials such, as germs cannot contaminate the blood of the fetus., (vi) Acts as a storage of glycogen. This glycogen gets, converted to glucose and fulfils the energy requirement of, the fetus., 31. Reproduction is the only means to ensure the continuity, of a species. During reproduction, DNA passes from one, generation to the next. Copying of DNA takes place with, consistency but with minor variations. This consistency, leads to stability of species. Hence, reproduction is linked to, stability of a species population. By reproduction, organisms, produce large number of new individuals of their own kind, out of which several get perished and only some survive., These surviving organisms replace the naturally dying, members of the population. Hence, the population as a, whole is not affected and remains stable., 32. Differences between natural and artificial propagation, in plants are as follows:, S., Natural propagation, Artificial propagation, No., (i), , Some most common, natural methods of, vegetative propagation in, plants are:, , It includes growing, plants by man-made, methods. Some common, artificial methods are :, , (ii), , Modified tuberous roots, can be propagated, vegetatively when planted, in soil (e.g., Sweet potato)., , Cutting of stem of, sugarcane, grapes, etc.,, which when grown in, soil develop into a new, plant., , (iii), , Underground, modified stems such as, rhizomes (e.g., ginger,, banana, etc.), corms, (e.g., Colocasia, etc.),, bulbs (e.g., garlic, onion,, etc.), tuber (potato),, sucker (mint) and subaerial stems such as, offset (Eichhornia), stolon, (strawberry), etc. develop, into new plants., Some plants develop, adventitious buds on their, leaves which develop, into new plants (e.g.,, Bryophyllum)., , Grafting is a process, in which branches of, two similar plants, one, potted plant and the, other of a good quality, plant are obliquely cut, and placed over each, other and tied by a tape, and left for a month or, so. A new plant thus, develops., , (iv), , In layering, the roots are, artificially induced on the, stem branches before, they are detached from, the parent plant for, propagation.

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59, , How do Organisms Reproduce?, , 33. Normally the two haploid gametes fuse to form one, diploid zygote. The zygote develops into a mature organism., At maturity, the organism develops sex organs and gametes, are formed from diploid cells by meiosis resulting in the, formation of haploid gametes. This process continues, generation after generation. Now if there is no meiosis, at the time of gamete formation the gametes formed as a, result of mitosis will be diploid. The two diploid gametes, will fuse to form a 4n zygote which develops in tetraploid, organism. Again this 4n organism will develop 4n gametes, which fuse to form 8n zygote. The number of chromosomes, will continue to double after each generation and a time will, come when there will be only DNA on earth., 34. Tissue culture is a modern technique of vegetative, propagation in which tissues from the growing tip of a plant, are removed and placed in an artificial medium where they, divide rapidly to form a small group of cells or callus which, is again transferred to another medium containing hormones, for growth and differentiation. The plantlets are then placed, in the soil so that they can grow into mature plants. This, technique is commonly used for ornamental plants., 35. There is a need for specialised cell types in multicellular bodies to carry out specialised functions. The creation, of germ-cells to participate in sexual reproduction is another, specialised function. Human beings also develop special, tissues for reproduction. However, while the body of the, individual organism is growing to its adult size, the resources, of the body are mainly directed at achieving this growth and, the maturation of the reproductive tissue is not likely to be a, major priority. So, during puberty maturation of reproductive, tissues takes place to attain sexual maturity and the rate of, general body growth slows down., 36. Human male reproductive system consists of testes,, scrotum, vas deferens, urethra and penis., (a) Testes : The human male possesses two testes, which, are the primary reproductive organs, lying outside the, abdominal cavity. The two testes are the male gonads, which, are the sites where male gametes, i.e., sperms are produced., The testes also produce the male sex hormone-testosterone., The testes of man produce sperms from puberty onwards,, throughout his life., (b) Scrotum: The scrotum is a pouch of skin that hangs, between the legs. It is divided internally into right and left, scrotal sacs by a partition. The two testes lie in respective, scrotal sacs. The scrotum acts as a thermoregulator and, provides an optimal temperature for the formation of sperms., The sperms develop at a temperature 2 – 2.5°C lower than, the normal body temperature., , Ureter, Urinary bladder, , Vas deferens, , Prostate, gland, Urethra, Penis, , Seminal vesicle, Cowper’s gland, , Scrotum Testis, Human male reproductive system (side view), , (c) Vas deferens : This is a straight tube, about 40 cm, long, which carries the sperms from epididymis towards the, urethra., (d) Urethra: It is about 20 cm long tube that arises from the, urinary bladder to carry urine. It runs through the penis and, opens to the outside through male genital pore. The contents, of two seminal vesicles, and sperms from vas deferens also, join the urethra. Thus urethra carries urine from the bladder,, as well as sperms from the vasa deferentia through the, penis., (e) Penis: Penis is a long and thick muscular organ made, up of mostly erectile tissue. At the time of sexual act, the, erectile tissue gets filled with blood causing the penis to, become erect. It is inserted into the vagina of the female, where sperms are ejaculated for the purpose of reproduction., 37. Sexual reproduction may be defined as the production, of offsprings (new individuals) by the fusion of two gametes, (usually one from male parent and the other from female, parent) to form a diploid zygote which develops into a, mature organism. Gamete formation involves meiosis or, reduction division. The gamete mother cell is diploid (2n),, i.e., it has two sets of chromosomes. This single diploid cell, divides by meiosis to form 4 haploid (n) daughter cells. Each, daughter cell becomes a gamete, either male or female., Each gamete possesses single set of chromosomes. Thus,, this division involves copying of the DNA as well as the, cellular apparatus. There is a stage in such nuclear division, where crossing over of chromosomes take place. This is very, important step which results in a slight different composition, of chromosomes in gametes. Fusion of these gametes results, in the formation of a slightly different individuals which, show variations. The variations which lead to the appearance, of such characters which fit to the changing environment, result in the survival of the species. Chances of variation,, therefore, are much more in sexual mode of reproduction

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60, as compared to asexual reproduction. Moreover, chances of, the production of compatible generations are also more in, sexual reproduction., 38. , (a) Having pregnancies too frequently and giving child, birth at quick succession reduce mother’s health and vitality, and cause mental strain. Health of children is also affected, due to nutritional deficiencies., (b) (i) Barrier method: These are physical devices to prevent, the entry of sperm into the female genital tract during, copulation. They also protect against sexually transmitted, diseases, e.g., condoms. Condoms are thin, strong rubber, sheaths used by man to cover the erect penis. It is simple, but effective and widely used contraceptive that has no side, , effects. It checks pregnancy by preventing deposition of, semen in the vagina., (ii) Chemical method: Foam tablets, jellies, pastes, creams, and spermicides are some common chemicals used by, females. These are placed in vagina. These chemicals adhere, to the mucous membrane and immobilise and kill the sperms., (iii) Surgical method: Surgical methods include – vasectomy, and tubectomy. Vasectomy is a small surgical operation, performed in males. It involves removal of a small portion, of the sperm duct (or vas deferens) by surgical operation., The two cut ends are then ligated (tied) with threads. This, prevents the sperms from coming out. Tubectomy is done in, females where oviducts are cut and the cut ends are tied, with threads., , 