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 11 of 22

Q201 CBSE 2024
1. (a)Write one function each of ovary and testis in the human reproductive system.
2. (b)Give reason why : (i) testes are located outside the abdominal cavity. (ii) lining of the uterus becomes thick every month.
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The ovary makes eggs, the testis sperms; testes need a cooler temperature, and the uterine lining thickens monthly to nourish an embryo.
(a) Ovary: it produces the female gametes, the eggs (ova); it also secretes female hormones such as oestrogen. Testis: it produces the male gametes, the sperms; it also secretes the hormone testosterone. (b)(i) Sperm formation requires a temperature lower than the normal body temperature, so the testes are located outside the abdominal cavity, in the scrotum, where it is cooler. (b)(ii) The ovary releases one egg every month, so every month the uterus prepares to receive and nourish an embryo: its lining becomes thick and spongy with a rich blood supply. If fertilisation does not occur, the lining breaks down and is shed as blood and mucus (menstruation).

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Q202 CBSE 2024

Explain with the help of a labelled diagram, the process of reproduction in Hydra by budding. Name the cells used for reproduction in this process.

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Hydra buds from regenerative cells: a bud grows tentacles, detaches and becomes a new Hydra.
Hydra reproduces asexually by budding. At one specific site on the side of its body, regenerative cells divide repeatedly and produce a small outgrowth called a bud. The bud grows and develops tentacles at its free end, becoming a tiny individual still attached to the parent. When fully mature, it detaches from the parent body and becomes a new, independent Hydra (see the labelled diagram of the stages: parent Hydra, tentacles, bud, bud with tentacles, new Hydra). The cells used for reproduction in this process are the regenerative cells.

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Q203 CBSE 2024
List two roles of each of the following in human reproductive system :
1. (i)Seminal vesicles and prostate gland
2. (ii)Oviduct
3. (iii)Testis
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Glands add a nourishing fluid to sperms; the oviduct carries the egg and is the fertilisation site; the testis makes sperms and testosterone.
(i) Seminal vesicles and prostate gland: (1) They add their secretions to the sperms, so that the sperms are carried in a fluid which makes their transport easier; (2) This fluid also provides nutrition to the sperms. (ii) Oviduct: (1) It carries the egg from the ovary to the uterus (womb); (2) It is the site of fertilisation — the sperms travel up to the oviduct, where they may meet and fertilise the egg. (iii) Testis: (1) It forms the male germ cells, the sperms; (2) It secretes the hormone testosterone, which regulates the formation of sperms and brings about the changes seen in boys at puberty.

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Q204 CBSE 2024

Explain the events that take place once a sperm reaches the oviduct till it becomes a foetus. Write the role of placenta in pregnancy.

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Fertilisation in the oviduct gives a zygote that becomes an implanted embryo, then a foetus; the placenta supplies nutrients and removes wastes.
Events: (1) Fertilisation: in the oviduct the sperm meets the egg and fuses with it, forming a fertilised egg, the zygote. (2) The zygote divides repeatedly to form a ball of cells, the embryo. (3) Implantation: the embryo gets implanted in the lining of the uterus, which has become thick and richly supplied with blood. (4) The placenta develops, and through it the embryo gets nourishment from the mother's blood. (5) The embryo grows and its tissues and organs develop; once its body parts can be identified it is called a foetus, which goes on developing inside the uterus, the whole development taking about nine months. Role of the placenta: it is a disc-like tissue embedded in the uterine wall, with villi on the embryo's side and blood spaces on the mother's side. It provides a large surface area through which glucose and oxygen pass from the mother to the embryo, and through which waste substances produced by the embryo are transferred to the mother's blood for removal.

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Q205 CBSE 2024
1. (i)Name three techniques/devices used by human females to avoid pregnancy. Mention the side effects caused by each.
2. (ii)What will happen if in a human female (a) fertilisation takes place, (b) an egg is not fertilised ?
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Pills, Copper-T and tubectomy prevent pregnancy; after fertilisation the embryo develops in the uterus, otherwise the lining is shed as menstruation.
(i) Three methods used by women: (1) Oral contraceptive pills, which change the hormonal balance so that no egg is released; side effect: hormonal imbalance, because they change the body's hormonal balance. (2) A Copper-T or loop placed in the uterus; side effect: irritation of the uterus. (3) Surgical blocking of the fallopian tubes (tubectomy), so that the egg cannot reach the uterus; side effect: the surgery can cause infection and other problems if it is not performed properly. (ii) (a) If fertilisation takes place, the zygote divides and is implanted in the thick, blood-rich lining of the uterus; the embryo develops there, getting nutrition from the mother's blood through the placenta, the lining is kept (no menstruation) and the pregnancy continues for about nine months. (b) If the egg is not fertilised, it lives for about one day; the thickened lining of the uterus is not needed, so it breaks down and comes out through the vagina as blood and mucus. This is menstruation, which lasts about two to eight days and recurs roughly every month.

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Q206 CBSE 2024
1. (i)What are spores ? On which structures are they formed ? How do they overcome unfavourable conditions ? Name the organism which multiplies with the help of these structures.
2. (ii)Give two reasons why some plants are grown by the method of vegetative propagation. List two methods used to grow plants vegetatively.
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Rhizopus spores form in sporangia and have thick protective walls; vegetative propagation (layering, grafting) gives earlier flowering and multiplies seedless plants.
(i) Spores are tiny reproductive cells, each of which can develop into a new individual. They are formed inside sporangia, the tiny blob-like structures on thin stalks that rise from the hyphae of bread mould. Each spore is covered by a thick wall that protects it in unfavourable conditions until it comes into contact with a moist surface, where it begins to grow. Rhizopus (bread mould) multiplies by these spores. (ii) Reasons: (1) Plants raised by vegetative propagation bear flowers and fruits earlier than those produced from seeds. (2) Plants that have lost the capacity to produce seeds, such as banana, orange, rose and jasmine, can still be propagated. (The new plants are also genetically similar to the parent plant and keep all its characteristics.) Methods: layering and grafting (growing plants from stem cuttings is another).

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Q207 CBSE 2024
(a) What is puberty ? Write any two changes that occur in boys during early teenage years. (b) List two functions performed by testis in human males. Mention one role each of
1. (i)Vas deferens,
2. (ii)Seminal Vesicle
3. (iii)Urethra and
4. (iv)Scrotum in human male reproductive system.
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Puberty is when the reproductive tissues mature; the testis makes sperms and testosterone, and the scrotum keeps it at a lower temperature.
(a) Puberty is the period of adolescence when the rate of general body growth slows down and the reproductive tissues begin to mature. Two changes in boys: new thick hair grows on the face (moustache and beard) and in the armpits and genital area; the voice begins to crack and becomes deeper. (b) Functions of the testis: it produces the sperms (male germ cells), and it secretes the hormone testosterone, which regulates sperm formation and brings about the changes of puberty in boys. (i) Vas deferens: carries sperms from the testis towards the urethra. (ii) Seminal vesicle: adds a secretion that nourishes the sperms and makes their transport easier. (iii) Urethra: common passage for sperms and urine; carries the sperms out of the body. (iv) Scrotum: holds the testes outside the abdominal cavity, at the lower temperature that sperm formation requires.

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Q208 CBSE 2024
1. (a)Name any two sexually transmitted diseases.
2. (b)Prenatal sex determination is prohibited by law. Why ?
3. (c)Name any three methods of contraception stating one side-effect of each.
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Gonorrhoea and HIV-AIDS are STDs; the ban prevents female foeticide; pills, Copper-T and surgery are contraceptive methods with side-effects.
(a) Any two of: gonorrhoea, syphilis (bacterial), warts, HIV-AIDS (viral). (b) Prenatal sex determination can be misused for illegal sex-selective abortion of female foetuses (female foeticide), which lowers the child sex ratio; the ban protects a healthy female-male sex ratio in society. (c) (1) Oral pills stop the release of eggs by changing the hormonal balance of the body; side-effect: hormonal imbalance, which can cause nausea, headache or irregular bleeding. (2) Copper-T or loop placed in the uterus; side-effect: irritation of the uterus. (3) Surgery, vasectomy or tubectomy; side-effect: infection or other problems if the operation is not performed properly.

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Q209 CBSE 2024
(i) Write the function of the following parts of a bisexual flower :
1. (1)stigma
2. (2)pollen tube and
3. (3)anther (ii) Name the (1) future shoot and (2) future root of a germinating seed. (iii) Name the parts of the flower that develop into (1) seed and (2) fruit after fertilization.
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Stigma receives pollen, pollen tube carries male germ-cells, anther makes pollen; plumule and radicle are future shoot and root; ovule becomes seed, ovary fruit.
(i) (1) Stigma: Receives the pollen grains during pollination; the pollen grain germinates on it. (2) Pollen tube: Grows out of the pollen grain, through the style, to the ovule and carries the male germ-cell to the female germ-cell for fertilisation. (3) Anther: Produces the pollen grains, which contain the male germ-cells. (ii) (1) Future shoot: Plumule; (2) Future root: Radicle. (iii) (1) Seed: Develops from the ovule; (2) Fruit: Develops from the ovary.

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Q210 CBSE 2024
(i) Draw a diagram showing spore formation in Rhizopus and label the
1. (a)reproductive and
2. (b)non-reproductive parts. Why does Rhizopus not multiply on a dry slice of bread ? (ii) Name and explain the process by which reproduction takes place in Hydra.
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Spores grow only on moist surfaces, so Rhizopus does not multiply on dry bread; Hydra reproduces by budding.
(i) Diagram (see the figure): a moist slice of bread covered by thread-like hyphae; upright stalks rise from them, each ending in a round sporangium full of spores. (a) Reproductive parts: the sporangia and the spores inside them (the blob-on-a-stick structures). (b) Non-reproductive parts: the thread-like hyphae. Rhizopus does not multiply on a dry slice of bread because its spores begin to grow only when they come into contact with a moist surface; a dry slice gives them no moisture, so the spores do not germinate and no hyphae grow. (ii) Hydra reproduces by budding, a kind of asexual reproduction. Its regenerative cells divide repeatedly at one specific site and form an outgrowth, the bud. The bud grows into a tiny individual with a mouth and tentacles and, when fully mature, detaches from the parent to become a new, independent Hydra.

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Q211 CBSE 2024
1. (i)Study the diagram given below and name the parts marked as A, B and C. What happens when B reaches C in the ovary ? Mention its significance.
2. (ii)Write the post fertilisation changes that occur in a flower.
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A, B and C are the male germ-cell, pollen tube and female germ-cell; fertilisation forms a zygote, then the ovule becomes a seed.
(i) A: male germ-cell; B: pollen tube; C: female germ-cell (egg), inside the ovule. When the pollen tube (B) reaches the female germ-cell (C) in the ovule, the male germ-cell is released and fuses with the female germ-cell. This fusion is fertilisation, and it forms a zygote. Significance: the zygote divides to form an embryo that can grow into a new plant, so seeds can form; fertilisation combines germ-cells from two parents, which brings variation; and it restores the normal number of chromosomes and amount of DNA in the new generation. (ii) After fertilisation, the zygote divides several times to form an embryo within the ovule; the ovule develops a tough coat and is gradually converted into a seed; the ovary grows rapidly and ripens to form a fruit; and the petals, sepals, stamens, style and stigma may shrivel and fall off.

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Q212 CBSE 2024
(a) Write two functions each of the following parts in human female reproductive system :
1. (i)Ovary
2. (ii)Oviduct
3. (iii)Uterus (b) Describe the structure and function of placenta.
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Ovary makes eggs and hormones; oviduct carries eggs and hosts fertilisation; uterus nourishes embryo; placenta passes oxygen, glucose and wastes between mother and embryo.
(a) (i) Ovary: produces the eggs (female germ cells), one egg being released every month; secretes female hormones such as oestrogen. (ii) Oviduct: carries the egg from the ovary towards the uterus; is the site where the sperm meets the egg and fertilisation takes place. (iii) Uterus: the zygote implants in its thick, blood-rich lining; it holds and nourishes the developing embryo through the placenta, and its muscles contract rhythmically to push the baby out at birth. (b) Structure: the placenta is a disc-shaped tissue embedded in the uterine wall, with finger-like villi on the embryo’s side and blood spaces on the mother’s side that surround the villi. Function: this gives a large surface area through which glucose and oxygen pass from the mother’s blood to the embryo, and the wastes produced by the embryo pass into the mother’s blood to be removed.

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Q213 CBSE 2024
1. (a)Name a unisexual and a bisexual flower.
2. (b)Define cross pollination. State how it is carried out.
3. (c)Observe the diagram given below and name the parts marked as ‘A’ and ‘B’. Mention the function of each of these parts.
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Papaya is unisexual and Hibiscus bisexual; cross-pollination uses wind, water or animals; A, the plumule, becomes the shoot and B, the radicle, the root.
(a) Unisexual flower: papaya (or watermelon), which has either stamens or a pistil. Bisexual flower: Hibiscus (or mustard), which has both stamens and a pistil. (b) Cross-pollination is the transfer of pollen grains from the anther of one flower to the stigma of another flower of the same kind. It is carried out by agents such as wind, water and animals (insects, birds), which carry the pollen from one flower to the other. (c) The drawing is an opened seed. A is the plumule, which grows into the shoot; B is the radicle, which grows into the root. The two lobes are the cotyledons, which store food for them.

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Q214 CBSE 2024
(i) Name the organ that produces sperms as well as secretes hormone in human male reproductive system. Name the hormone it secretes and write its function. (ii) Name the part of the human female reproductive system where
1. (i)fertilisation occurs and
2. (ii)implantation of zygote takes place.
3. (iii)Explain how the embryo gets its nourishment inside the mother’s body.
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The testes make sperms and testosterone; fertilisation occurs in the oviduct, implantation in the uterus, and the placenta nourishes the embryo.
(i) The testes produce the sperms and also secrete the hormone testosterone. Function of testosterone: It regulates the formation of sperms and brings about the changes in appearance seen in boys at puberty. (ii) Fertilisation occurs in the oviduct (fallopian tube), and implantation of the zygote takes place in the lining (wall) of the uterus. (iii) The embryo gets its nutrition from the mother's blood through a special tissue, the placenta, a disc embedded in the uterine wall. The placenta has villi on the embryo's side, surrounded by blood spaces on the mother's side; this gives a large surface area across which glucose and oxygen pass from the mother to the embryo, and the wastes of the embryo pass into the mother's blood to be removed.

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Q215 CBSE 2024
1. (i)What is vegetative propagation ? Is this process sexual or asexual ? Justify your answer.
2. (ii)List three advantages of practising the process/technique by the farmers.
3. (iii)Select two plants from the following which are obtained by this technique : Banana, Papaya, Jasmine, Mustard
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Vegetative propagation is asexual, as one parent and no gametes are involved; banana and jasmine are obtained this way.
(i) Vegetative propagation is the development of new plants from vegetative parts of a parent plant (root, stem or leaf) instead of from seeds. It is asexual: only one parent is involved, no gametes are formed and no fertilisation takes place, so the new plants are genetically similar to the parent. (ii) Plants raised this way bear flowers and fruits earlier than those raised from seeds; plants that have lost the capacity to produce seeds (such as banana, rose and jasmine) can be propagated; all the new plants are genetically similar to the parent and keep its desirable characteristics. (iii) Banana and jasmine.

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Q216 CBSE 2024
(i) List two functions each of the following parts of the human female reproductive system :
1. (1)oviduct
2. (2)uterus
3. (3)ovary (ii) How does the embryo get nourishment inside the mother’s body ? Explain briefly.
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Oviduct, uterus and ovary each perform two functions; the embryo is nourished by the mother's blood through the placenta.
(i) Oviduct: carries the egg from the ovary to the uterus; fertilisation takes place in it. Uterus: the zygote gets implanted in its thick, blood-rich lining; it nourishes and protects the embryo through the placenta until birth, when its muscles contract rhythmically to push the baby out. Ovary: produces the eggs (one egg a month from one of the ovaries); produces hormones such as oestrogen. (ii) The embryo gets nourishment from the mother's blood through the placenta, a disc embedded in the uterine wall. Villi on the embryo's side are surrounded by blood spaces on the mother's side, which gives a large surface area for glucose and oxygen to pass from the mother to the embryo; the embryo's wastes pass back into the mother's blood.

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Q217 CBSE 2024
Asexual reproduction involves a single parent to produce offsprings without the formation of gametes. It occurs by the following ways : Fission, Budding, Fragmentation, Spore formation and Regeneration. In one of the methods like regeneration, Planaria A is cut horizontally into three pieces – L, M and N and Planaria B is cut vertically into two equal halves – O and P.
1. (a)Which of the cut pieces of the two Planaria could regenerate to form a complete organism ?[1]
2. (b)Give an example of another organism which follows the same mode of reproduction as Planaria.[1]
3. (c)(i)What is the meaning of ‘development’ in regeneration ?[2]
4. (c)(ii)OR : Differentiate between regeneration and fragmentation.[2]
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All pieces (L, M, N, O, P) regenerate; Hydra is another example; development is the organised sequence of changes forming the lost parts.
(a) All the pieces: L, M and N of Planaria A, and O and P of Planaria B, can each regenerate into a complete organism. (b) Hydra. (c)(i) In regeneration, specialised cells in the cut piece divide and make a large number of cells. From this mass of cells, different cells change into the various cell types and tissues of the missing parts. These changes take place in an organised sequence, and this organised sequence of changes is called development. OR (c)(ii) Regeneration: occurs in fully differentiated organisms (Hydra, Planaria) when the body is cut or broken; specialised cells divide and develop into the lost parts; it is not the normal way these organisms reproduce. Fragmentation: occurs in simple multicellular organisms (Spirogyra); the body breaks up into pieces by itself on maturing, and each piece simply grows by cell division into a new individual; it is a normal method of reproduction.

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Q218 CBSE 2024
Pollination is an important process in sexual reproduction of plants. It is an essential process that facilitates fertilisation in plants. Pollinating agents can be wind, water, insects and birds. Several changes take place in the flower after the fertilization has taken place.
1. (a)Write the main difference between self-pollination and cross-pollination.[1]
2. (b)Name the part of the flower which attracts insects for pollination. What happens to this part after fertilisation ?[1]
3. (c)(i)Define fertilisation. What is the fate of ovules and the ovary in a flower after fertilisation ?[2]
4. (c)(ii)OR : In a germinating seed, which parts are known as future shoot and future root ? Mention the function of cotyledon.[2]
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Petals attract insects and then shrivel; ovules become seeds, the ovary a fruit; plumule is the future shoot, radicle the future root.
(a) In self-pollination, pollen is transferred from the anther to the stigma of the same flower; in cross-pollination, it is transferred from the anther of one flower to the stigma of another flower. (b) The petals (brightly coloured) attract insects. After fertilisation, the petals shrivel and fall off. (c)(i) Fertilisation is the fusion of the male germ cell (from the pollen grain) with the female gamete (egg) in the ovule, forming a zygote. After fertilisation, the ovules develop into seeds and the ovary ripens into the fruit. (c)(ii) The plumule is the future shoot and the radicle is the future root. The cotyledon stores food for the growing embryo.

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Q219 CBSE 2024
Plantation drives are often carried out especially during monsoon season for the protection of our environment. Such programmes need a lot of saplings for tree plantation. Plants are propagated by sexual or asexual means in fields and nurseries. Over the years horticulturists have developed asexual methods that use vegetative parts of the plants to multiply. Many plants can reproduce by this method naturally as well as by artificial means.
1. (a)Which specific part of the plant is used for sexual and asexual means of propagation to produce a new plant ?[1]
2. (b)Give one example of (i) a flower, and (ii) a fruit grown by vegetative propagation.[1]
3. (c)(i)List two advantages of growing plants by vegetative propagation.[2]
4. (c)(ii)OR : Describe an activity to show how potatoes reproduce asexually.[2]
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Seed for sexual, a vegetative part for asexual propagation; vegetative plants flower earlier; potato buds grow into new plants.
(a) For sexual propagation the seed is used: formed in the flower after fertilisation, it grows into a new plant. For asexual propagation a vegetative part of the plant — the root, stem or leaf — is used. (b) (i) Rose (or jasmine). (ii) Banana (or orange, or grapes). (c)(i) Any two of these: plants raised by vegetative propagation bear flowers and fruits earlier than those produced from seeds; it allows the propagation of plants such as banana, orange, rose and jasmine that have lost the capacity to produce seeds; all the plants produced are genetically similar enough to the parent plant to have all its characteristics. (c)(ii) Cut a potato into small pieces so that some pieces contain a notch (bud) and some do not. Place the pieces on wet cotton spread in a tray, keep the cotton moist, and observe them for a few days. Only the pieces with a bud develop green shoots and roots, which shows that the buds of a potato grow into new plants — the potato reproduces asexually, by vegetative propagation.

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Q220 CBSE 2023
During adolescence, reproductive phase starts and :
1. (a)general growth rate begins to slow down
2. (b)height becomes less
3. (c)the body weight is reduced
4. (d)hair growth decreases
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(a) general growth rate begins to slow down

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