Class 10 Science · Chapter 7

How do Organisms Reproduce?

434 Class 10 Science questions on How do Organisms Reproduce? from the NCERT textbook, NCERT Exemplar and CBSE board papers 2017–2026, each with its answer and a step-by-step solution.

NCERT exercises

Exercises (11) Intext Questions (Page 114) (2) Intext Questions (Page 119) (5) Intext Questions (Page 126) (5)

NCERT Exemplar exercises

Multiple Choice Questions (27) Short Answer Questions (21) Long Answer Questions (10)

CBSE Class 10 Science previous year papers, with answers →

Questions · page 14 of 22

Q261 CBSE 2022
1. (a)What happens when in a human female the egg released by the ovary is not fertilised ?
2. (b)Name one bacterial and one viral infection caused due to unsafe sex.
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If the egg is not fertilised, the thick uterine lining breaks down and leaves as menstruation; gonorrhoea is bacterial, HIV-AIDS viral.
(a) The egg lives for only about one day. In each monthly cycle the lining of the uterus becomes thick and spongy, ready to receive and nourish a fertilised egg; when the egg is not fertilised this lining is not needed, so it slowly breaks down and comes out through the vagina as blood and mucus. This is menstruation. It takes place roughly every month and usually lasts for about 2 to 8 days. (b) Bacterial infection: gonorrhoea (or syphilis). Viral infection: HIV-AIDS (or warts).

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Q262 CBSE 2022
1. (a)Name the reproductive and non-reproductive parts of bread mould (Rhizopus).
2. (b)List any two advantages of vegetative propagation.
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In Rhizopus the sporangia are reproductive and the hyphae are not; vegetative propagation gives earlier flowering and fruiting, and propagates seedless plants.
(a) Reproductive parts: the sporangia - the tiny blob-like heads on thin stalks - which contain the spores that can develop into new Rhizopus. Non-reproductive parts: the hyphae - the thread-like structures that spread over the bread. (b) Any two of: (1) Plants raised by vegetative propagation bear flowers and fruits earlier than plants grown from seeds. (2) Plants that have lost the capacity to produce seeds, such as banana, orange, rose and jasmine, can still be propagated. (3) All the plants produced are genetically similar enough to the parent plant to have all its characteristics, so a desirable variety is kept.

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Q263 CBSE 2022
(a) State one drawback of each of the following :
1. (i)Oral contraceptive pills
2. (ii)Copper-T (b) Under which category of contraceptive methods, is the use of condom kept ? In what way, its use is better as compared to other methods of contraception ?
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(a) Pills and copper-T can cause side effects; (b) the condom is a barrier method that also helps prevent sexually transmitted diseases.
(a)(i) Oral pills act by changing the hormonal balance of the body (so that eggs are not released), so they can cause side effects. (a)(ii) The copper-T, placed in the uterus, can cause side effects due to irritation of the uterus. (b) The condom is a barrier (mechanical) method of contraception. It is better because, besides stopping the sperm from reaching the egg, it also helps to prevent the transmission of many sexually transmitted diseases, such as gonorrhoea, syphilis and HIV-AIDS, and it has none of the hormonal or uterine side effects of the other two methods.

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Q264 CBSE 2022
Mention the functions of
1. (a)Placenta
2. (b)Fallopian tubes
3. (c)Uterus and
4. (d)Ovary in the human female reproductive system.
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The ovary produces eggs, the fallopian tube is where fertilisation occurs, the uterus nourishes the embryo, and the placenta links embryo and mother.
(a) Placenta: a disc-like tissue embedded in the wall of the uterus that connects the embryo to the mother. Glucose (nutrition) and oxygen pass through it from the mother's blood to the embryo, and the wastes produced by the embryo pass through it into the mother's blood to be removed. (b) Fallopian tubes: they carry the egg released by the ovary towards the uterus, and fertilisation - the meeting of the sperm and the egg - takes place in them. (c) Uterus: the fertilised egg (zygote), dividing as it travels down, is implanted in its thick, blood-rich lining; the embryo is protected and nourished there and develops into a baby until birth, when the rhythmic contractions of its muscles push the baby out. (d) Ovary: it produces the female germ cells, the eggs (in NCERT's account, one egg every month by one of the ovaries), and secretes female hormones such as oestrogen.

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Q265 CBSE 2022

Name the parts A, B and C of the diagram given below. Write a function of the part B.

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A is the pollen grain, B the pollen tube and C the female germ-cell; the pollen tube carries the male germ-cell to the egg.
A - Pollen grain; B - Pollen tube; C - Female germ-cell (the egg cell) inside the ovule. Function of B: after the pollen grain lands on the stigma, the pollen tube grows out of it, down through the style into the ovary, and carries the male germ-cell to the female germ-cell in the ovule, so that fertilisation can take place.

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Q266 CBSE 2022

What is placenta ? Why is it extremely essential for the development of embryo ?

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The placenta is a disc-like tissue in the uterine wall linking embryo and mother; it supplies glucose and oxygen and removes the embryo's wastes.
Placenta: a special tissue, a disc embedded in the uterine wall, that connects the developing embryo with the mother. It has villi on the embryo's side, and blood spaces on the mother's side that surround the villi. It is extremely essential because (1) the embryo gets its nutrition (glucose) and oxygen from the mother's blood through it: the villi provide a large surface area for glucose and oxygen to pass from the mother to the embryo; and (2) the waste substances produced by the developing embryo are removed by transferring them into the mother's blood through it. The embryo in the uterus depends on the placenta for all of these, so it is essential for its development.

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Q267 CBSE 2022

Explain briefly how vegetative propagation takes place in a ‘Bryophyllum’ plant.

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Buds in the notches of a Bryophyllum leaf fall on moist soil and each grows into a new plant.
In Bryophyllum, vegetative propagation takes place through the leaves. Buds are produced in the notches along the margin of the leaf. When these buds, or the leaf bearing them, fall on moist soil, each bud develops roots and a shoot and grows into a new plant. The new plants come from the leaf of a single parent, without seeds and without the fusion of gametes, so this is vegetative (asexual) propagation, and the new plants are genetically similar enough to the parent to have all its characteristics.

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Q268 CBSE 2022
What happens when
1. (a)A spirogyra filament attains maturation ?
2. (b)Planaria is cut into any number of pieces ?
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A mature Spirogyra filament breaks into fragments that grow into new filaments; each piece of a cut Planaria regenerates into a complete worm.
(a) When a Spirogyra filament attains maturity, it simply breaks up into smaller pieces called fragments. Each fragment grows into a new Spirogyra filament, a new individual. This is fragmentation, a method of asexual reproduction. (b) When a Planaria is cut into any number of pieces, each piece grows into a complete Planaria. This is regeneration: specialised cells in each piece proliferate to form a mass of cells, and these cells then change into the various cell types and tissues in an organised sequence called development, rebuilding the parts that are missing.

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Q269 CBSE 2022
1. (a)Name the process shown below and define it :
2. (b)Name the types of cells present in the organisms which exhibit this process.
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Regeneration: a fully differentiated organism grows new organisms from its body parts when cut; it is carried out by specialised cells.
(a) The process is regeneration (shown here in Planaria). Regeneration is the ability of a fully differentiated organism to give rise to new individual organisms from its body parts: if the organism is cut or broken up into many pieces, many of the pieces grow into separate, complete organisms. In the figure, one Planaria cut into three pieces gives three complete Planaria. (b) Specialised cells. They proliferate to make a large mass of cells, and different cells of this mass then change into the various cell types and tissues of the new organism.

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Q270 CBSE 2022

In the following figure showing a germinating gram seed, name the parts labelled as A, B and C : Why is part ‘B’ considered to be important during germination ?

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A is the plumule, B the cotyledon and C the radicle; the cotyledon is important as it stores food for the germinating seed.
A – Plumule (grows into the shoot); B – Cotyledon (the seed leaf that stores food); C – Radicle (grows into the root). Part B, the cotyledon, is important because it stores food: during germination the growing plumule and radicle use this food, and they depend on it until the seedling has green leaves and can make its own food by photosynthesis.

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Q271 CBSE 2022

Suggest any two contraceptive methods to control the size of human population and explain them.

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Condoms (a mechanical barrier) stop sperms reaching the egg, and oral pills change the hormonal balance so that no egg is released.
Any two of the following, each with its explanation: (1) Mechanical barrier: a condom on the penis, or a similar covering worn in the vagina, prevents the sperms from reaching the egg, so fertilisation does not take place. (2) Oral pills: they change the hormonal balance of the body so that eggs are not released, and fertilisation cannot occur. Also accepted: a loop or copper-T placed in the uterus to prevent pregnancy; surgical blocking of the vas deferens (vasectomy), which prevents the transfer of sperms, or of the fallopian tube (tubectomy), which stops the egg from reaching the uterus.

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Q272 CBSE 2022
(a) In the given diagram, name the parts where
1. (i)pollen grains are produced, and
2. (ii)pollen grains are transferred. (b) What happens to ovule and ovary after fertilisation ?
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Pollen is made in the anthers (D) and transferred to the stigma (A); the ovule becomes the seed and the ovary the fruit.
(a) (i) Pollen grains are produced in D, the anthers of the stamens. (ii) Pollen grains are transferred to A, the stigma at the tip of the carpel; this transfer from anther to stigma is pollination. (b) After fertilisation the ovule develops into the seed: the zygote inside it divides to form the embryo, and the ovule develops a tough coat. The ovary grows rapidly and ripens to form the fruit, which encloses the seeds.

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Q273 CBSE 2022

What is Regeneration ? Explain the process of regeneration in Planaria.

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Regeneration is the ability of an organism to grow new individuals from body parts; each piece of a cut Planaria grows into a complete worm.
Regeneration is the ability of a fully differentiated organism to give rise to new individual organisms from its body parts: if the organism is cut or broken into pieces, many of the pieces grow into separate, complete individuals. Regeneration in Planaria: when a Planaria is cut into a few pieces, each piece can grow into a complete worm. Regeneration is carried out by specialised cells, which proliferate and make a large number of cells. From this mass of cells, different cells undergo changes to become the various cell types and tissues of the missing parts. These changes take place in an organised sequence called development, so each piece becomes a complete Planaria.

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Q274 CBSE 2022
Mention the changes that occur in the following after fertilisation in a flower :
1. (a)Petals
2. (b)Zygote
3. (c)Ovary
4. (d)Ovule
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After fertilisation the petals wither, the zygote becomes the embryo, the ovary ripens into the fruit and the ovule becomes the seed.
(a) Petals: They shrivel (wither) and usually fall off. (b) Zygote: It divides several times to form an embryo within the ovule. (c) Ovary: It grows rapidly and ripens to form the fruit. (d) Ovule: It develops a tough coat and is gradually converted into a seed.

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Q275 CBSE 2022

Name the reproductive parts of an angiosperm. Where are these parts located ? Explain the structure of its male reproductive part.

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Stamens and pistil are the reproductive parts, located in the flower; a stamen has a filament bearing an anther with pollen sacs.
Reproductive parts: the stamens (male reproductive part) and the pistil or carpel (female reproductive part). Location: in the flower - in a bisexual flower the pistil is at the centre and the stamens are around it. Structure of the male reproductive part (the stamen): it consists of a thin stalk, the filament, which bears at its tip the anther. The anther contains pollen sacs in which the yellowish pollen grains, carrying the male germ-cells, are produced.

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Q276 CBSE 2022

What is puberty ? Mention any two changes that are common to both boys and girls in early teenage years.

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Puberty is the period when the reproductive tissues mature as general growth slows; new body hair and oily skin occur in both sexes.
Puberty: the period during adolescence when, as the rate of general body growth begins to slow down, the reproductive tissues begin to mature. Any two changes common to both boys and girls: (1) Thick hair grows in new parts of the body, such as the armpits and the genital area between the thighs, and it can become darker; thinner hair can also appear on the legs, arms and face. (2) The skin frequently becomes oily and pimples may appear. (Also acceptable: they become conscious and aware of their own bodies and those of others in new ways.)

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Q277 CBSE 2022
1. (a)Differentiate between binary fission in Amoeba and binary fission in Leishmania.
2. (b)How does reproduction take place in malarial parasite ?
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Amoeba divides in any plane, Leishmania lengthwise in a definite plane relative to its flagellum; the malarial parasite reproduces by multiple fission.
(a) Binary fission in Amoeba: Amoeba has no definite shape, and the splitting of its cell into two daughter cells can take place in any plane. Binary fission in Leishmania: Leishmania has a whip-like flagellum at one end, and its binary fission takes place in a definite plane in relation to this flagellum - lengthwise, that is, longitudinal binary fission - with each daughter cell getting a flagellum. (b) The malarial parasite (Plasmodium) reproduces by multiple fission. Its nucleus divides repeatedly to form many nuclei, each nucleus is surrounded by a little cytoplasm, and the single cell divides into many daughter cells at the same time; these are released and each grows into a new parasite.

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Q278 CBSE 2022
Name the part/organ of the human female reproductive system
1. (a)where contraceptive devices such as loop or copper-T are placed to prevent pregnancy.
2. (b)which is blocked to prevent the transfer of eggs.
3. (c)where formation of green cells as ova takes place.
4. (d)from where the embryo gets nutrition from the mother’s blood.
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Uterus, fallopian tube (oviduct), ovary and placenta, for (a) to (d) respectively.
(a) Uterus: the loop or copper-T is placed in the uterus. (b) Fallopian tube (oviduct): when it is blocked, the egg cannot reach the uterus. (c) Ovary: the female germ cells (ova) are formed in the ovaries. (d) Placenta: a tissue embedded in the uterine wall, through which the embryo gets nutrition from the mother's blood.

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Q279 CBSE 2022
(a) Mention one function each of the following organs in human male reproductive system :
1. (i)Testis
2. (ii)Scrotum
3. (iii)Vas deferens
4. (iv)Prostate gland (b) Name the type of germ cell which (i) is motile, and (ii) stores food.
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Testis makes sperms, scrotum keeps testes cooler, vas deferens carries sperms, prostate adds fluid; the sperm is motile, the egg stores food.
(a) (i) Testis: makes the male germ cells, the sperms (it also secretes the hormone testosterone). (ii) Scrotum: holds the testes outside the abdominal cavity, where they stay a little cooler than the normal body temperature — the lower temperature that sperm formation requires. (iii) Vas deferens: carries the sperms from the testis to the urethra. (iv) Prostate gland: adds its secretion to the sperms, so that they are in a fluid which makes their transport easier and also provides nutrition. (b) (i) The male germ cell (sperm) is motile. (ii) The female germ cell (egg, or ovum) stores food.

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Q280 CBSE 2022

In flowering plants, the pollen grains are transferred to stigma by pollination but the female germ cells are present in the ovary. Explain with the help of a labelled diagram (only concerned parts), how the male germ cell reaches the ovary.

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After pollination, a pollen tube carries the male germ-cell from the stigma through the style to the ovule, where it fuses with the egg.
After pollination the pollen grain germinates on the stigma: a pollen tube grows out of the pollen grain and travels down through the style to reach the ovary. The male germ-cell passes down inside this tube. In the ovary the tube enters an ovule and releases the male germ-cell there, and it fuses with the female germ-cell (egg) in the ovule. This fusion is fertilisation, and it forms the zygote. Labelled diagram (only the parts concerned): pollen grain on the stigma, pollen tube running down the style, the male germ-cell in the tube, ovary, ovule and the female germ-cell inside the ovule (see the figure).

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