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Downloaded from https:// www.studiestoday.com, , , , , , , , , , , , , , , , , , SYLLABUS, , 1. Asexual and sexual reproduction in animals., * Life cycle of a butterfly — may be observed directly if, possible (D)., 2. Reproduction in human beings., 3. Physical changes in human beings as a result of growth. —, 4. Adolescence and adulthood — problems related with adolescence., * Measuring height and weight of children in different classes — finding _, averages — peng results and ari at conclusions ee ae, , el pre oe = clad be, , , , , , Reproduction is the process of of reproduction in single-celled organism, —, , producing new individuals of the same kind., Reproduction also helps in the continuance, of the species. Different organisms, reproduce in different ways., , You have already studied that some, single-celled organisms, like amoeba,, , reproduce by simply dividing into two. |, , Some multicellular animals like hydra,, produce small buds which grow in size and, get separated. These are the asexual methods, of reproduction (not involving eggs or, sperms)., , However, most animals reproduce, sexually. In this process of reproduction, two, sexes produce special types of reproductive, cells i.e. males — the sperms and females — the, eggs. The sperms and the eggs fuse to form, a zygote, which ultimately gives rise to an, adult organism., , ASEXUAL REPRODUCTION IN ANIMALS, , 1. Fission (Binary fission or multiple, fission) — This is the most common ae, , LR 42 |, , e.g., amoeba, etc. It results in the division of, the parent amoeba into two daughter, amoebae (Fig. 5.1). First, the nucleus divides ©, into two, followed by the division of the, cytoplasm and then, the two separate and, live as new individuals., , NUCLEUS, , , , , , oo, , , , DAUGHTER AMOEBAE, , Fig. 5.1 Binary fission sion in, 2. Budding — Budding is, which buds grow on the ou, , Downloaded from https:// www.studiestoday.com

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ody (Fig. 5.2). These buds detach themselves, when they are big enough, for independent, xistence., , HYPOSTOME, , Downloaded from https:// www.studiestoday.com, , To produce a new individual, the sperm, has to reach the ovum of the opposite sex and, fuse with it. This process is called, fertilisation., , After the fertilisation of an ovum by a, sperm, a cell called the zygote is formed., The zygote grows by cell division and, produces an embryo. The embryo finally, grows to become a new individual., , | Wet a, . SPERMS (° fda O—t ~Gr@=p— (CF, : AND FORMING WHICH UNDERGOES AND es, ©) MEET Flse A ZYGOTE CELL DIVISION GROWS: joo, OVUM, , , , , , , , , , , , , , , , , , , , , , , , Fig. 5.2 Hydra, , 3. Regeneration - Animals like hydra, and starfish have a great power to regrow, ithe missing or lost parts of their body. This, process of generating lost parts is called, regeneration. Regeneration can also take, place for reproductive purposes. For example,, in hydra, if we cut it transversely into 2-3, pieces, each piece will regenerate and give, rise to a new individual., , SEXUAL REPRODUCTION IN ANIMALS, , Most animals reproduce sexually. In, sexual reproduction, the two sexes i.e., male, and female produce special types of, reproductive cells — sperms in the male and, eggs in the female., , TAIL NUCLEUS, , , , +—— 0.01 mm, , NUCLEUS, , , , , , CELL MEMBRANE, , CYTOPLASM, , -———— 0.05 mm, , Fig. 5.3 Human sperm and egg, , , , Fig. 5.4 Fertilisation and development, , LIFE CYCLE OF AN INSECT, Different insects have different methods, to grow from its egg stage to an adult stage., For example, the egg of a grasshopper hatch, out in a tiny hopper called nymph, which, feeds and grows into an adult., NYMPH, , oe, , , , , , ADULT, , Fig. 5.5 Stages in the life-cycle of Grasshopper :, showing incomplete metamorphosis, , But in case of a butterfly, the egg, hatches out in a larva, which undergoes, , transformation to form a pupa. This pupa, , Downloaded. from https:// www.studiestoday.com

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Downloaded from https:// www.studiestoday.com, , , , , , , , , , , , , , , , , , , , , , , ultimately gives rise to an Adult. In the case The complete t ormat, of a butterfly, the endian ofeggtoan tan adult butterfly described, adult undergoes the following stages : complete metamorphosis., , Egg — Larva + Pupa — Adult, , AST ENPAR, , , , , , A, , ———, MEAD, "aecingDR OP’ >. Werwess, PROLEGS, , ‘EGS SPRUCLES Lama, , Fig. 5.6 Life-cycle of a butterfly, , Life Cycle of a Butterfly, , The butterfly lays the fertilized egg on the, leaves. The new born that hatches from the, egg is called a larva. It passes through various, stages of development. The larva of the, butterfly, also called a caterpillar, is active, at this stage. It feeds, moves about and grows, in size. Once the larva is fully developed, it, stops moving and feeding, and develops into, pupa which isa resting stage. The larva spins, threads around itself to construct a cocoon, which protects the underlying pupa. During, this period, the pupa develops the features, of an adult, though it appears to be at rest., The pupa undergoes reorganisation of tissues, and organs and emerges out as a butterfly, after breaking open the cocoon. ai

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yet : BUTTERFLY, , > Replace the old and dried leaves with |, ‘ fresh and tender leaves. Pour some |, | _ water on the blotting paper everyday to |, | keep it moist. Pick up 1 or 2 young |, caterpillars. |, > The caterpillars continue to feed, grow in |, size and moult (shed off their old skin) |, at regular intervals. Every time the |, Bs _ caterpillar moults, it increases in its size. |, _ Such moulting occurs 4-5 times. |, > In about 15-20 days, the caterpillars |, become fully grown and acquire green |, colour. These fully grown caterpillars do |, , of feeding. |, , t 1emsel, , , , , : yey stop feeding, they fix |, ¢ es on the leaves with a}, thread secreted by themselves |, and change into pupa (chrysalis). |, The larva keep spinning the thread |, und its body to construct a cocoon. |, oon protect the pupa whch |, ¢ stage and does not feed. |, [0-12 days from this time, |, , , , , , , , Downloaded from https:// www.studiestoday.com, , HUMAN REPRODUCTIVE SYSTEM, , Female — The eggs are produced from the, ovaries. The ovaries are two whitish oval, bodies, lying within the lower half of the, abdomen, one on each side of the uterus., There is an expanded, funnel-shaped tube, called oviduct or Fallopian tube close to each, ovary. It is through this tube that the egg, , passes down when released from the ovary., OVIDUCT (FALLOPIAN TUBE), , FUNNEL OF OVIDUCT, , OVARY, , INNER LINING OF, UTERUS, , MUSCULAR WALL, CERVIX (NECK OF UTERUS), , VAGINA, , OPENING OF VAGINA, , Fig. 5.7 The reproductive system of the, , human female, , The two oviducts open into the uterus or, womb. The uterus leads to the outside, through a muscular tube, called the vagina, (popularly known as birth canal). The urinecarrying urethra from the urinary bladder,, opens into the vulva just in front of the, vaginal opening., , Male - Sperms are produced in the testes., The testes lie outside the abdominal cavity, in a sac called the scrotum. In such an, arrangment, the testes are at a temperature,, 2 — 3°C lower than that of the body. This is, the most suitable temperature for sperm, production., , The testes consist of a mass of sperm-—, producing tubes. These tubes join to form, ducts leading to the epididymis which in, turn leads into a muscular sperm duct. The, two sperm ducts, one from each testis, open, at the top of the urethra., , The seminal vesicles are a pair of lobulated, glands, each opening into the corresponding, , , , 4s REESE, , Downloaded from https:// www.studiestoday.com

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Downloaded from https:// www.studiestoday.com, , sperm duct just before it unites with the urethra., The seminal vesicles produce a secretion which, serves as a medium for the transportation of the, sperms. The mixture of this fluid and the sperms, produce a milky fluid, called the semen., , TUBE FROM BLADDER, , SEMINAL VESICLE, , PROSTATE GLAND, COWPER'S GLANDS, SPERM DUCT, , URETHRA, , EPIDIDYMIS, , HEAD OF PENIS (GLANS), FORESKIN, TESTIS, , SCROTAL SAC (SCROTUM), , , , Fig. 5.8 The reproductive system of, the human male, , The base of the urethra is surrounded by, the prostate gland which pours an alkaline, secretion into the semen as it passes through, the urethra., , Two small ovoid glands open into the, urethra just before it enters the penis. These, glands are called Cowper’s glands. The, secretion of Cowper’s glands serves as a, lubricant., , The urethra passes through the penis and, carries either urine or semen., , Semen is a mixture of sperms and, secretions from seminal, prostate and, Cowper’s glands. It is a milky fluid. Its, average amount is 2 — 3 ml in a single, ejaculation, and contains 20,000,000 —, 40,000,000 sperms., , FERTILISATION, , During sexual intercourse, the semen gets, deposited in the female’s vagina. The sperms, (present in the semen) released in the vagina, actively swim upwards with the help of their, tail. Out of the millions of sperms released, into the vagina, only a few of them are able to, , , , climb up to the upper parts of oviducts. THe !, rest die on the way and are absorbed. If them, , happens to be an egg in the oviduct, it gets, fertilised by just one single sperm. During this —, , fusion, the tail of the sperm is left behind and —, , only the head part (which contains nucleus), , penetrates the egg. The nucleus of the sperm —, fuses with the nucleus of the egg. Thisis called —, , as fertilisation., IMPLANTATION, , The fertilised egg (zygote) soon starts —, developing and by the time it reaches the —, , uterus, a small ball of numerous cells is, , already formed. This is a kind of embryo |, , which forms a pit in the wall of the uterus, and gets fixed in it. This natural way of fixing, of the embryo in the wall of the uterus is, called implantation. This produces the state, of pregnancy. ., , By the end of five weeks of pregnancy,, the embryo is in quite advanced stage., During this period, the heart and circulatory, system are formed. After two months, limbs, are also formed., , GROWTH, Growth means any type of irreversible, , increase in the size and weight of |, , an individual during the process of, development., , In the growth process, a single-celled, fertilised egg i.e., a zygote divides and, redivides to form a cluster of cells. This, division is accompanied by another process, i.e., specialisation of cells. The specialisation, of cells lead to the formation of different parts, of the body. This whole process is called, , differentiation. This process also gives rise to various tissues, and further, various —, organs and organ systems. Thus, the zygote |, grows into an embryo, an embryo into a_, , baby, and a baby ultimately into an adult. —, , 6 La, , Downloaded from https:// www.studiestoday.com