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 9 of 22

Q161 CBSE 2025
1. (a)Name the method by which Amoeba and Leishmania reproduce. Write a major difference in the way they divide to produce new individuals.
2. (b)What is asexual reproduction ? Explain the process of budding in Hydra.
3. (c)Give two methods used to grow rose and jasmine plants by vegetative propagation.
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Amoeba and Leishmania divide by binary fission, in any plane and a definite plane respectively; Hydra buds; rose and jasmine use layering and grafting.
(a) Both reproduce by binary fission. In Amoeba the cell can split into two in any plane, whereas in Leishmania, which has a whip-like flagellum at one end of the cell, the cell divides in a definite plane, lengthwise, in relation to the flagellum. (b) Asexual reproduction is the production of new individuals by a single parent without the formation and fusion of gametes; the offspring are genetically similar to the parent. In Hydra, a bud develops as an outgrowth at one specific site by repeated cell division of its regenerative cells. The bud grows into a tiny individual and, when fully mature, detaches from the parent and becomes a new independent Hydra. (c) Layering and grafting (stem cuttings are also used).

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Q162 CBSE 2025
1. (i)Differentiate between self-pollination and cross-pollination.
2. (ii)Identify A, B and C in the diagram given below and write one function of each.
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Self-pollination is within one plant, cross-pollination between plants; A is the stigma, B the pollen tube, C the female germ cell.
(i) In self-pollination the pollen is transferred from the anther to the stigma of the same flower, or of another flower on the same plant, whereas in cross-pollination it is carried from the anther of a flower on one plant to the stigma of a flower on a different plant of the same kind. Self-pollination within a single flower is possible only in a bisexual flower, while cross-pollination occurs in unisexual flowers as well; within one flower it needs no external agent, while cross-pollination always requires wind, water, insects, birds or other animals; it involves one parent plant, while cross-pollination involves two; and its offspring are almost identical with the parent so that the variety stays pure, while the offspring of cross-pollination combine the characters of two parents, show new variations and are usually healthier and better adapted. (ii) A is the stigma, whose function is to receive the pollen grains at pollination and to provide the sticky, moist surface on which a grain germinates. B is the pollen tube, whose function is to carry the male germ cell from the pollen grain down through the style and into the ovule and deliver it to the female germ cell. C is the female germ cell, or egg, whose function is to fuse with the male germ cell in fertilisation and so form the zygote that grows into the embryo of the seed.

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Q163 CBSE 2025
1. (i)Name the type of asexual mode of reproduction shown in the given figure.
2. (ii)Identify the unicellular organism in the diagram.
3. (iii)List any two advantages of asexual reproduction over sexual reproduction.
4. (iv)Name and explain any one mode of asexual reproduction observed in Hydra.
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Leishmania divides by binary fission; asexual reproduction needs one parent and gives identical offspring quickly; Hydra reproduces by budding.
(i) Binary fission — more precisely longitudinal binary fission, which takes place in a definite orientation with respect to the whip-like flagellum of the cell. (ii) The organism is Leishmania, the protozoan that causes kala-azar. (iii) Two advantages of asexual over sexual reproduction: (1) only one parent is needed — no gametes, no mate and no fertilisation — so it is much faster and produces a large number of offspring in a short time; (2) the offspring are genetically identical to the parent, so a successful set of characters is passed on unchanged, and no energy is spent on gametes, on attracting a mate or on reproductive structures. (iv) Budding. Because of repeated cell division at one particular site on the body wall of Hydra, an outgrowth called a bud develops. The bud grows, and a mouth surrounded by tentacles appears at its free end; when it is fully developed it detaches from the parent body and lives as an independent new individual identical to the parent.

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Q164 CBSE 2025
1. (i)Name and state the reproductive process taking place in (I) Plasmodium, and (II) Leishmania.
2. (ii)Name three techniques/devices used by human females to avoid pregnancy. Also mention the side effects of each.
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Plasmodium divides by multiple fission and Leishmania by binary fission; oral pills, Copper-T and tubectomy are three female methods, each with side effects.
(i)(I) Plasmodium reproduces by **multiple fission**. The nucleus of the single-celled parasite divides repeatedly to give many nuclei inside one cell; the cytoplasm then divides around each nucleus, and the parent cell breaks up, releasing many daughter cells simultaneously. (II) Leishmania reproduces by **binary fission**. The parent cell divides into two equal daughter cells, and the division always takes place in a **definite orientation** — lengthwise, along the long axis of the cell, with respect to the whip-like flagellum at one end — so each daughter receives a flagellum. (ii) Three techniques or devices used by human females, with their side effects: (1) **Oral contraceptive pills** — hormonal tablets that change the hormonal balance so that eggs are not released; side effects: they disturb the hormonal balance and may cause nausea, headache, weight gain, irregular bleeding and mood changes, and prolonged use can lead to more serious effects. (2) **Intrauterine contraceptive devices** such as the Copper-T or loop, placed in the uterus, which prevent fertilisation and implantation; side effects: irritation of the uterus, pain and excessive bleeding during periods, and the risk of infection or inflammation of the reproductive tract. (3) **Surgical method** — **tubectomy**, in which the fallopian tubes are blocked or cut so that the egg cannot meet a sperm; side effects: being an operation it carries a risk of infection and inflammation and of post-operative pain if not done properly, and it is normally irreversible. (The female condom, a barrier device, is an acceptable alternative: it may slip or tear and so is less reliable, and it can cause irritation or an allergic reaction.)

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Q165 CBSE 2025
(i) Name the part performing following functions in human male reproductive system :
1. (a)Carries sperm
2. (b)Production of male gametes
3. (c)Whose secretion makes the transport of sperms easier
4. (d)Provide suitable temperature for sperm formation (ii) Write any two characteristics of sperms. (iii) What are surgical contraceptive methods? Give the side effect caused by this procedure.
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The parts are vas deferens, testes, seminal vesicles with prostate and scrotum; sperms are motile and haploid; surgical methods block gametes.
(i) (a) Vas deferens (the sperm duct) carries the sperm; (b) the testes produce the male gametes, the sperms; (c) the seminal vesicles and the prostate gland, whose secretions make the transport of sperms easier and also nourish them; (d) the scrotum, which holds the testes outside the abdominal cavity and so keeps them at a temperature lower than the normal body temperature, as sperm formation requires. (ii) A sperm is a very small motile cell made up mainly of genetic material, with a head carrying the nucleus, a middle piece and a long tail that helps it swim towards the female germ cell; and it is haploid, carrying only half the number of chromosomes (23 in a human) so that the full number is restored at fertilisation. (iii) Surgical contraceptive methods block the passage of the gametes by an operation so that fertilisation cannot occur: in the male the vas deferens is cut and tied (vasectomy) and in the female the fallopian tubes are cut and tied (tubectomy). Side effect: if the operation is not performed properly under sterile conditions it can cause infection and other complications at the site of surgery.

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Q166 CBSE 2025
(a) Name the part performing following functions in human female reproductive system :
1. (i)production of eggs
2. (ii)site of fertilization
3. (iii)site of implantation
4. (iv)entry of the sperms (b) What changes are observed in the uterus : (i) subsequent to implantation of zygote and (ii) if an egg does not get fertilized ?
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The parts are the ovary, fallopian tube, uterus and vagina; the lining thickens after implantation or is shed as menstruation if no fertilisation occurs.
(a) (i) Ovary; (ii) Fallopian tube, that is the oviduct; (iii) Uterus, in its lining; (iv) Vagina. (b) (i) After the zygote implants, the lining of the uterus becomes still thicker and richer in blood vessels, and a placenta develops between the embryo and the uterine wall, with villi on the embryo's side and blood spaces on the mother's side, through which glucose and oxygen pass to the embryo and its wastes pass back to the mother; the uterus enlarges as the embryo grows. (ii) If the egg is not fertilised, the thick lining is no longer needed and breaks down, and it is shed through the vagina as blood and mucus. This is menstruation, lasting about two to five days and recurring about every twenty-eight days.

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Q167 CBSE 2025

In human female reproductive system state the changes that take place once fertilisation has taken place. Write the role of placenta in this process. What happens when the egg is not fertilised ?

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After fertilisation the embryo implants in the uterus and the placenta nourishes it; if the egg is unfertilised, the lining is shed as menstruation.
Once fertilisation has taken place in the oviduct, the zygote divides to form an embryo, which is implanted in the thick, blood-rich lining of the uterus and goes on developing there; the lining is kept, so there is no menstruation during pregnancy, and after about nine months the child is born by rhythmic contractions of the muscles of the uterus. Role of the placenta: the placenta is a disc of special tissue embedded in the uterine wall, with villi on the embryo’s side surrounded by blood spaces on the mother’s side; this large surface lets glucose and oxygen pass from the mother’s blood to the embryo, and lets the waste substances produced by the embryo pass into the mother’s blood for removal. If the egg is not fertilised, it lives for about one day; the thick, spongy lining the uterus prepared is not needed, so it breaks down and comes out through the vagina as blood and mucus — menstruation, which takes place roughly every month and usually lasts about two to eight days.

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Q168 CBSE 2025
(a) Write one function each of the parts –
1. (i)petals
2. (ii)anther
3. (iii)style and
4. (iv)ovary of a bisexual flower. (b) Give one example each of a unisexual flower and a bisexual flower. Mention the changes which a flower undergoes after fertilization.
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Petals attract insects, anther makes pollen, style leads to the ovary; after fertilisation the ovule becomes the seed and the ovary the fruit.
(a) (i) Petals: brightly coloured petals attract insects, which bring about pollination. (ii) Anther: produces the pollen grains, which carry the male germ cells. (iii) Style: joins the stigma to the ovary; the pollen tube grows down through it to reach the ovary. (iv) Ovary: contains the ovules, each with an egg cell; after fertilisation it develops into the fruit. (b) Unisexual flower: papaya (or watermelon). Bisexual flower: Hibiscus (or mustard). After fertilisation the zygote divides to form an embryo within the ovule; the ovule develops a tough coat and becomes a seed; the ovary grows and ripens into a fruit; and the petals, sepals, stamens, style and stigma may shrivel and fall off.

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Q169 CBSE 2025
1. (i)In which form is the information for inheritance of features transmitted from one generation to the next generation ?
2. (ii)Differentiate between binary fission in Amoeba and Leishmania.
3. (iii)"Fragmentation cannot be a method of reproduction in all multicellular organisms." Justify this statement.
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Inheritance information is carried as DNA; Amoeba divides in any plane, Leishmania lengthwise; complex bodies cannot fragment because a piece lacks all tissues.
(i) The information for inheritance of features is transmitted from one generation to the next in the form of DNA, that is deoxyribonucleic acid, present in the chromosomes in the nucleus of the cell; its units are the genes, which carry the information for making proteins and so for the body design. (ii) In Amoeba the body has no fixed or definite shape, so binary fission is simple: the cell divides into two daughter cells along any plane, the plane of division not being fixed. In Leishmania the cell has a definite shape with a whip-like structure, a flagellum, at one end, so it has a definite orientation, and binary fission occurs in a definite plane, longitudinally along the length of the cell with respect to that end. (iii) Organisms with a complex body design are not simple collections of cells: their cells are organised into specialised tissues, organs and organ systems placed at definite positions. A fragment of such a body does not contain all the tissues and organs required, and its specialised cells can no longer divide to give rise to every other kind of cell, so it cannot grow into a new individual. Fragmentation works only in simple multicellular organisms of relatively simple body organisation, such as Spirogyra, where any piece of the filament grows into a new plant. Hence fragmentation cannot be a method of reproduction in all multicellular organisms.

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Q170 CBSE 2025
1. (i)Define placenta. State the structure and role of placenta in the development of embryo in human beings.
2. (ii)List three categories of contraceptives and give one example of each.
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The placenta exchanges glucose, oxygen and wastes between mother and embryo through villi; contraceptives are barrier, chemical and surgical.
(i) The placenta is a special disc-like tissue embedded in the wall of the uterus which connects the developing embryo to the body of the mother and through which substances are exchanged between them. Structure: it contains villi, finger-like projections of tissue on the side of the embryo, and on the side of the mother there are blood spaces surrounding these villi; this provides a very large surface area for exchange, while the two bloodstreams remain separate, and the embryo is joined to it by the umbilical cord. Role: glucose and oxygen pass from the mother to the embryo through the placenta, providing its nutrition and the oxygen for its respiration, and the waste substances generated by the embryo, such as carbon dioxide and urea, are removed into the blood of the mother through it. It also secretes hormones that maintain the pregnancy. (ii) Three categories of contraceptives are: barrier or mechanical methods, example the condom; chemical or hormonal methods, example oral contraceptive pills; and surgical methods, example vasectomy in the male or tubectomy in the female. Intra-uterine contraceptive devices such as the copper T form a further category.

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Q171 CBSE 2025
When a girl is born, the ovaries already contain thousands of immature eggs. On reaching puberty, some of these start maturing. One matured egg is released every month by one of the ovaries. The two oviducts unite into an elastic bag-like structure known as uterus.
1. (a)Write the site of fertilization in human female.[1]
2. (b)How does the uterus prepare itself to receive and nurture the growing embryo ? Explain.[1]
3. (c)(i)What happens when the egg is not fertilized ?[2]
4. (c)(ii)OR : How does the developing embryo get nutrition from the mother's blood ? Explain.[2]
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Fertilisation occurs in the oviduct; the uterine lining thickens for implantation; an unfertilised egg leads to menstruation; the placenta nourishes the embryo.
(a) Fertilisation takes place in the oviduct, also called the fallopian tube. (b) Every month the lining of the uterus becomes thick and spongy and is richly supplied with blood, so that a fertilised egg can be implanted in it and the growing embryo can be nourished and protected there. (c)(i) An unfertilised egg lives for only about one day. The thick, spongy lining that the uterus had prepared is then no longer needed, so it slowly breaks down and comes out through the vagina as blood and mucus. This is menstruation; it happens roughly every month and usually lasts about two to eight days. (c)(ii) The embryo gets its nutrition from the mother's blood through the placenta, a special disc-shaped tissue embedded in the uterine wall. It bears villi on the embryo's side, and on the mother's side there are blood spaces that surround these villi. This gives a large surface area across which glucose and oxygen pass from the mother's blood to the embryo, while the waste substances the embryo generates are passed back into the mother's blood through the same placenta.

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Q172 CBSE 2024
Which one of the following statements is NOT true ?
1. (a)DNA carries the information for inheritance of features from parents to the next generation.
2. (b)DNA is the information source for making proteins.
3. (c)Change in the information leads to different proteins.
4. (d)Features will remain the same even if the protein changes.
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(d) Features will remain the same even if the protein changes.

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Q173 CBSE 2024
In the given diagram the leaf shown belongs to which plant ?
1. (a)Hibiscus
2. (b)Money plant
3. (c)Mustard
4. (d)Bryophyllum
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(d) Bryophyllum

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Q174 CBSE 2024
The plants that can be raised by the method of vegetative propagation are :
1. (a)Sugarcane, roses, grapes
2. (b)Sugarcane, mustard, potato
3. (c)Banana, orange, mustard
4. (d)Papaya, mustard, potato
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(a) Sugarcane, roses, grapes

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Q175 CBSE 2024
The part of the flower which attracts insects for pollination is/are :
1. (a)Stigma and style
2. (b)Sepals and petals
3. (c)Petals only
4. (d)Sepals only
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(c) Petals only

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Q176 CBSE 2024
Part(s) of a flower which attracts insects for pollination is (are)
1. (a)petals and Sepals
2. (b)anther and Stigma
3. (c)petals only
4. (d)sepals only
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(c) petals only

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Q177 CBSE 2024
The part of seed which is a source of food during germination of seed is :
1. (a)Cotyledon
2. (b)Radicle
3. (c)Plumule
4. (d)Embryo
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(a) Cotyledon

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Q178 CBSE 2024
The incorrect statement about placenta is :
1. (a)It is a disc embedded in the uterine wall.
2. (b)It contains villi on the embryo’s side of the tissue.
3. (c)It has a very small surface area for glucose and oxygen to pass from mother to the embryo.
4. (d)The embryo gets nutrition from the mother’s blood through it.
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(c) It has a very small surface area for glucose and oxygen to pass from mother to the embryo.

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Q179 CBSE 2024
Select from the following the part/parts of a flower which attracts/attract insects for pollination :
1. (a)Petals only
2. (b)Sepals only
3. (c)Anther and Stigma
4. (d)Petals and Sepals
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(a) Petals only

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Q180 CBSE 2024
Which one of the following statements is TRUE for Hydra, Amoeba and Spirogyra ?
1. (a)They are multicellular.
2. (b)They are unicellular.
3. (c)They reproduce sexually.
4. (d)They reproduce asexually.
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(d) They reproduce asexually.

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