Chapter 7 · How do Organisms Reproduce?
NCERT Class 10 Science Chapter 7 Intext Questions (Page 126)
All 5 questions of NCERT Class 10 Science Chapter 7 Intext Questions (Page 126) — How do Organisms Reproduce? — in the book's order, each with its answer and a step-by-step solution.
- Q1How is the process of pollination different from fertilisation?Step-by-step solution →
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Pollination moves pollen to the stigma, while fertilisation is fusion of male and female gametes inside the ovule, producing the zygote.
They are two different stages of the same story, and they differ in four ways. (i) What happens: pollination is the transfer of pollen grains from the anther of the stamen to the stigma of the pistil, while fertilisation is the fusion of the male germ-cell produced by the pollen grain with the female gamete present in the ovule. (ii) Where it happens: pollination ends on the stigma, on the outside of the pistil, while fertilisation takes place inside the ovule, within the ovary. (iii) What it needs: pollination is brought about by external agents such as wind, water or animals, and is called self-pollination when the pollen stays in the same flower and cross-pollination when it goes from one flower to another; fertilisation needs no outside agent, only the pollen tube that grows out of the pollen grain and travels through the style to the ovary. (iv) What it produces: pollination produces nothing new, since nothing has joined, whereas fertilisation produces the zygote, which divides several times to form the embryo, so that the ovule becomes the seed and the ovary ripens into the fruit. Pollination always comes first, and it can happen without fertilisation following, but fertilisation in a flower cannot happen unless pollination has occurred. - Q2What is the role of the seminal vesicles and the prostate gland?Step-by-step solution →
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Their secretions form a fluid that eases the transport of sperms and nourishes them; sperms plus this fluid form semen.
The seminal vesicles and the prostate gland are accessory glands that lie along the path of the vas deferens and add their secretions to the sperms as the sperms pass. Their role is therefore twofold. (i) The secretions put the sperms into a fluid, which makes their transport out of the body much easier, since a sperm is only a tiny body of genetic material with a long tail and cannot travel through a dry tube. (ii) The same fluid provides the sperms with nutrition for the journey to the female germ-cell, which matters because a sperm carries no food store of its own. The sperms together with this fluid make up the semen. Neither gland produces the sperms themselves; sperms are formed in the testes, which also secrete the hormone testosterone. - Q3What are the changes seen in girls at the time of puberty?Step-by-step solution →
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In girls puberty brings body hair, oily skin and pimples, breast enlargement with darker nipples, the start of menstruation and new body awareness.
The changes fall into two groups. (i) Changes common to girls and boys: thick hair begins to grow in new parts of the body, in the armpits and in the genital area between the thighs, and the skin there can also become darker; thinner hair appears on the legs and arms and on the face; the skin frequently becomes oily and pimples may develop; and there is a new consciousness and awareness of one's own body and of the bodies of others. (ii) Changes seen in girls in particular: the breast size begins to increase, with darkening of the skin of the nipples at the tips of the breasts, and girls begin to menstruate at around this time. All these changes take place slowly, over months and years. They do not happen all at once, nor at an exact age, and they differ from one girl to another. Every one of them is an aspect of the sexual maturation of the body, which begins during adolescence, when the rate of general body growth slows down and the reproductive tissues begin to mature. - Q4How does the embryo get nourishment inside the mother's body?Step-by-step solution →
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The embryo is nourished through the placenta, where glucose and oxygen pass from the mother's blood to it and its wastes pass back.
Through the placenta. After fertilisation the zygote divides to form a ball of cells, and this embryo is implanted in the lining of the uterus, which has thickened and become richly supplied with blood to nourish it. The embryo then gets its nutrition from the mother's blood with the help of a special tissue called the placenta, a disc embedded in the uterine wall and joined to the embryo by the umbilical cord. The placenta contains villi on the embryo's side of the tissue, and on the mother's side are blood spaces which surround these villi. Because the finger-like villi dip into pools of the mother's blood, the arrangement provides a large surface area, so that glucose and oxygen can pass in quantity from the mother to the embryo. The traffic runs both ways: the waste substances that the developing embryo generates are removed by transferring them into the mother's blood through the same placenta. In this way the placenta feeds the embryo, supplies it with oxygen and carries its wastes away for the roughly nine months of development, doing the work that the digestive system, the lungs and the kidneys will take over after birth. - Q5If a woman is using a copper-T, will it help in protecting her from sexually transmitted diseases?Step-by-step solution →
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No; the copper-T only prevents pregnancy, while a condom protects against both pregnancy and infection.
No, it will not. The copper-T is a contraceptive device placed inside the uterus, and its only effect is to prevent pregnancy; it can also cause side effects due to irritation of the uterus. Sexually transmitted diseases, such as the bacterial infections gonorrhoea and syphilis and the viral infections warts and HIV-AIDS, are passed on because the sexual act is a very intimate connection of bodies, so the germs cross where the two bodies touch and exchange fluids. The copper-T covers neither the penis nor the vaginal passage, so it leaves that contact entirely unaffected and the germs pass exactly as they would without it. Protection from these infections needs a barrier method instead: using a covering called a condom for the penis during sex helps to prevent the transmission of many of them to some extent, and a similar covering worn in the vagina serves the same purpose. So the copper-T guards against pregnancy alone, while a condom guards against both pregnancy and infection.