NCERT Solutions for Class 10 Science Chapter 7: How do Organisms Reproduce? (NCERT 2026–27)
These Class 10 Science Chapter 7 solutions cover How do Organisms Reproduce? from the NCERT textbook (rationalised, session 2026–27). You get every in-text “Questions” set and the complete end-of-chapter Exercises reproduced verbatim and solved in clear, exam-ready language — asexual and sexual reproduction, reproduction in flowering plants, the human reproductive systems, menstruation, contraception and reproductive health.
Class: 10Subject: Science (Biology)Chapter: 7Title: How do Organisms Reproduce?Type: In-text Qs + ExercisesSession: 2026–27
Chapter 7, How do Organisms Reproduce?, explains why and how living things make new individuals like themselves. The most basic event in reproduction is the creation of a DNA copy along with extra cellular apparatus, so that a cell can divide into two. Because no biochemical copying is perfectly accurate, small variations arise — these are usually harmless and are the raw material for survival of the species and for evolution. The chapter then surveys asexual modes (fission, fragmentation, regeneration, budding, vegetative propagation, spore formation) and sexual reproduction in flowering plants (pollination → fertilisation → seed and fruit) and in human beings (male and female reproductive systems, the menstrual cycle, the role of the placenta, contraception and reproductive health, including the importance of maintaining the sex ratio).
Key Concepts & Definitions
Reproduction: the process by which an organism produces new individuals of its own kind; it is not essential for an individual’s survival but is essential for continuity of the species.
Asexual reproduction: new individuals are formed from a single parent without the fusion of gametes (e.g. fission, budding, fragmentation, spore formation, vegetative propagation). Offspring are genetically almost identical to the parent.
Sexual reproduction: two parents contribute gametes that fuse (fertilisation) to form a zygote; it produces greater variation.
Fission: a unicellular parent splits to form daughter cells — binary (two) or multiple (many).
Regeneration / Budding: growth of a complete organism from a body part (Hydra, Planaria) / outgrowth of a bud that detaches as a new individual (Hydra, yeast).
Pollination & Fertilisation: transfer of pollen from anther/stamen to stigma; followed by fusion of male and female gametes to form the zygote.
Meiosis: reductional cell division that halves the chromosome number in gametes, so the original number is restored after fertilisation.
Reproduction at a glance: DNA copy + cellular apparatus → cell divides → 2 cells (similar, slightly varied).
Sexual cycle: Gamete (n) + Gamete (n) ⟶ fertilisation → Zygote (2n) → Embryo → New individual.
Chromosome balance: meiosis halves chromosomes in gametes (2n → n); fertilisation restores them (n + n = 2n).
In-text Questions — Page 114
1. What is the importance of DNA copying in reproduction?
ANSWERDNA carries the information (blueprint) for the body design and all the proteins of an organism. During reproduction, DNA copying ensures that this information is passed on to the offspring, so that the new individuals resemble the parent and inherit its characteristics.DNA copying also maintains the stability of features that allow the organism to occupy its niche. At the same time, the small, unavoidable errors in copying create variations — the basis of evolution and of the survival of the species when the environment changes.
2. Why is variation beneficial to the species but not necessarily for the individual?
ANSWERVariation is useful at the level of the whole population, not for every single individual. If the environment (niche) changes drastically — for example a rise in water temperature — most organisms suited to the old conditions may die.However, a few individuals carrying suitable variations (e.g. heat resistance) can survive and reproduce, so the species continues. An individual variation may give no advantage, or may even be harmful to that individual, but the presence of variation in the population as a whole improves the chances of survival of the species over time.
In-text Questions — Page 119
1. How does binary fission differ from multiple fission?
ANSWERBinary fission: the parent cell divides into two daughter cells. The nucleus divides once and the cytoplasm splits into two equal halves, e.g. Amoeba, Leishmania, many bacteria.Multiple fission: the parent cell divides into many daughter cells at the same time. The nucleus divides repeatedly first, and then the cytoplasm divides around each nucleus, e.g. Plasmodium (malarial parasite).
2. How will an organism be benefited if it reproduces through spores?
ANSWERSpores are produced in very large numbers inside sporangia, so the organism can produce many offspring quickly. Each spore is light and easily dispersed by wind or water, helping the organism spread to new places.Spores are covered by a thick protective wall that keeps them safe in unfavourable conditions; they germinate only when they reach a suitable moist surface. This protection and wide dispersal greatly improve the chances of survival and continuation of the species (e.g. in Rhizopus).
3. Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
ANSWERIn complex multicellular organisms, the body is not a random mass of cells. Specialised cells are organised into tissues, tissues into organs, and organs are placed at definite positions to perform specialised functions.Because of this high degree of organisation, a small piece cannot reorganise itself into all the different tissues and organs needed for a complete body. Such organisms therefore depend on specialised reproductive cells and more complex (mostly sexual) modes of reproduction rather than regeneration.
4. Why is vegetative propagation practised for growing some types of plants?
ANSWERVegetative propagation allows plants such as banana, orange, rose and jasmine — which have lost the ability to produce viable seeds — to be grown. Plants raised this way bear flowers and fruits earlier than plants grown from seeds.All plants produced are genetically similar to the parent, so desirable characteristics are retained exactly. It is therefore a quick and reliable way to multiply useful plants (e.g. by layering or grafting in sugarcane, roses and grapes).
5. Why is DNA copying an essential part of the process of reproduction?
ANSWERDNA contains all the genetic information that decides the body design and characteristics of an organism. Copying the DNA ensures that this information is faithfully transmitted from parent to offspring, so that the offspring resemble the parents.It also maintains the body features needed for the organism to survive in its niche, while the slight copying errors introduce variations that are essential for the survival of the species and for evolution. Without DNA copying, no information would be passed on and reproduction could not occur.
In-text Questions — Page 126
1. How is the process of pollination different from fertilisation?
ANSWERPollination is the transfer of pollen grains from the anther (stamen) to the stigma of a flower, brought about by agents such as wind, water or animals. It can be self-pollination (same flower) or cross-pollination (different flower). No fusion of gametes occurs in pollination.Fertilisation is the fusion of the male germ-cell (from the pollen grain) with the female gamete (egg cell) inside the ovule, forming a zygote. Pollination always comes first and is followed by the growth of a pollen tube; fertilisation completes the sexual process.
2. What is the role of the seminal vesicles and the prostate gland?
ANSWERThe seminal vesicles and the prostate gland add their secretions to the sperms as they pass along the vas deferens. These secretions provide a fluid medium in which the sperms can move easily.The fluid also nourishes the sperms (supplying nutrients) and makes their transport towards the female germ-cell easier. Together with the sperms, these secretions form the semen.
3. What are the changes seen in girls at the time of puberty?
ANSWERAt puberty, girls show: increase in breast size with darkening of the skin of the nipples; growth of thick hair in the armpits and the genital area (which may darken); and thinner hair on arms and legs.The skin often becomes oily and pimples may appear, and girls begin to menstruate. These changes are signs of sexual maturation and prepare the body for reproduction.
4. How does the embryo get nourishment inside the mother’s body?
ANSWERThe embryo gets nourishment from the mother’s blood through a special disc-like tissue called the placenta, which is embedded in the uterine wall. The placenta has villi on the embryo’s side and blood spaces on the mother’s side surrounding the villi.This arrangement provides a large surface area through which glucose and oxygen pass from the mother to the embryo. Waste substances produced by the embryo are also removed by passing into the mother’s blood through the placenta.
5. If a woman is using a copper-T, will it help in protecting her from sexually transmitted diseases?
ANSWERNo. A copper-T is placed in the uterus only to prevent pregnancy; it does not create any barrier against the entry of disease-causing germs during the sexual act.Therefore it cannot protect a woman from sexually transmitted diseases (such as gonorrhoea, syphilis, warts or HIV-AIDS). Only a barrier method like a condom helps to prevent the transmission of such infections to some extent.
NCERT Exercises — Full Solutions
1. Asexual reproduction takes place through budding in
(a) Amoeba.(b) Yeast.(c) Plasmodium.(d) Leishmania.
ANSWER(b) Yeast.Yeast reproduces asexually by budding — it puts out small buds that grow and then separate to form new individuals. Amoeba and Leishmania reproduce by binary fission, and Plasmodium by multiple fission.
2. Which of the following is not a part of the female reproductive system in human beings?
(a) Ovary(b) Uterus(c) Vas deferens(d) Fallopian tube
ANSWER(c) Vas deferens.The vas deferens is part of the male reproductive system; it carries sperms from the testes. The ovary, uterus and fallopian tube are all parts of the female reproductive system.
3. The anther contains
(a) sepals.(b) ovules.(c) pistil.(d) pollen grains.
ANSWER(d) pollen grains.The anther is the upper part of the stamen (male part) and produces pollen grains, which carry the male gametes. Ovules are found inside the ovary of the pistil.
4. What are the advantages of sexual reproduction over asexual reproduction?
ANSWERGreater variation: sexual reproduction combines DNA from two different parents, creating new combinations of variations in every offspring. This makes the offspring genetically diverse rather than near-identical copies.Better survival & evolution: this variation increases the chance that some individuals survive when the environment changes, and provides the raw material for evolution. Useful new characters can also appear and be passed on.Because each new variation is built on variations already present in living parents, it is assured that these are not seriously harmful, so the species adapts and remains stable over generations.
5. What are the functions performed by the testis in human beings?
ANSWERProduction of sperms: the testes form the male germ-cells (sperms). They lie outside the abdominal cavity in the scrotum because sperm formation needs a temperature slightly lower than normal body temperature.Secretion of testosterone: the testes secrete the male hormone testosterone, which regulates the formation of sperms and brings about the changes in appearance (such as facial hair and voice change) seen in boys at puberty.
6. Why does menstruation occur?
ANSWEREach month one ovary releases an egg, and the uterus prepares to receive a fertilised egg by making its inner lining thick and spongy with a rich supply of blood, so that it can nourish an embryo.If fertilisation does not take place, the egg lives only about a day and the thick lining is no longer needed. The lining therefore slowly breaks down and is shed through the vagina as blood and mucous. This monthly process is called menstruation; it usually lasts about two to eight days.
7. Draw a labelled diagram of the longitudinal section of a flower.
ANSWERDraw a flower cut vertically through the middle and label these parts from outside inwards and base to tip: Sepal (outermost green leaf-like part), Petal (coloured part), the Stamen (male part = filament + anther, with pollen grains in the anther), and the Pistil (female part in the centre).Show the three parts of the pistil clearly: the swollen base = Ovary (containing ovules, each with an egg cell), the middle elongated stalk = Style, and the terminal sticky tip = Stigma. (Refer to NCERT Fig. 7.7 for the layout.)Description in words for revision: Stigma at the top → Style in the middle → Ovary at the base with ovules; stamens on the sides; petals and sepals surrounding the reproductive parts.
8. What are the different methods of contraception?
ANSWERBarrier methods: condoms on the penis or coverings worn in the vagina create a mechanical barrier so that sperms do not reach the egg. Condoms also help prevent many sexually transmitted infections.Hormonal methods (oral pills): drugs that change the hormonal balance so that eggs are not released and fertilisation cannot occur. As they alter hormones, they may cause side-effects.Intra-uterine devices (IUDs): devices such as the loop or copper-T are placed in the uterus to prevent pregnancy; they may cause side-effects due to irritation of the uterus.Surgical methods: blocking the vas deferens in the male (so sperms cannot pass) or the fallopian tube in the female (so the egg cannot reach the uterus) prevents fertilisation. Surgery can also be used to remove unwanted pregnancies.
9. How are the modes for reproduction different in unicellular and multicellular organisms?
ANSWERUnicellular organisms reproduce by simple methods involving the division of the single cell — binary fission (Amoeba), multiple fission (Plasmodium) or budding (yeast). One cell directly gives rise to new individuals.Multicellular organisms have bodies organised into specialised cells, tissues and organs, so they cannot simply divide cell-by-cell. They use more complex modes such as fragmentation, regeneration, budding, vegetative propagation, spore formation or sexual reproduction, often carried out by specific reproductive cells or organs.
10. How does reproduction help in providing stability to populations of species?
ANSWERReproduction continuously creates new individuals to replace those that die, keeping the population size and the species in existence over time. The consistency of DNA copying maintains the body-design features that let the organism use its particular niche.In this way reproduction keeps populations well-suited to their niches and balances the birth and death rates, giving stability. At the same time the variations it produces allow some individuals to survive environmental changes, so the species remains stable in the long run.
11. What could be the reasons for adopting contraceptive methods?
ANSWERTo avoid unwanted pregnancy: pregnancy makes major demands on a woman’s body and mind; if she is not ready, her health can be adversely affected. Contraception lets couples plan and space children.To prevent sexually transmitted diseases: barrier methods such as condoms help reduce the spread of infections like gonorrhoea, syphilis and HIV-AIDS.To control population growth: a rapidly expanding population makes it harder to improve everyone’s standard of living, so contraception helps keep the population in check and supports a healthier society.
Extra Practice Questions
Short Answer Type Questions
Q1. Define regeneration and give two examples.
ANSWERRegeneration is the ability of a fully differentiated organism to grow a complete new individual from a body part if it is cut or broken. Examples: Hydra and Planaria. It is carried out by specialised cells that proliferate and develop into different tissues, but it is not the normal mode of reproduction.
Q2. What is meant by self-pollination and cross-pollination?
ANSWERSelf-pollination is the transfer of pollen from the anther to the stigma of the same flower. Cross-pollination is the transfer of pollen from one flower to the stigma of a different flower, usually by wind, water or animals.
Q3. Why are the testes located outside the abdominal cavity in the scrotum?
ANSWERBecause the formation of sperms requires a temperature slightly lower than the normal body temperature. The scrotum, being outside the abdominal cavity, provides this cooler environment.
Q4. Distinguish between unisexual and bisexual flowers with examples.
ANSWERA unisexual flower has either stamens or pistil (e.g. papaya, watermelon). A bisexual flower has both stamens and pistil in the same flower (e.g. hibiscus, mustard).
Q5. What is tissue culture and where is it used?
ANSWERTissue culture is a technique in which cells or tissue from the growing tip of a plant are placed in an artificial nutrient medium where they divide to form a callus; the callus is then transferred to a medium with hormones to grow into plantlets. It lets many disease-free plants be grown from one parent and is commonly used for ornamental plants.
Long Answer Type Questions
Q1. Describe the process of reproduction in flowering plants from pollination to seed and fruit formation.
ANSWERPollen produced by the anther is transferred to the stigma of the pistil by wind, water or animals (pollination). On a suitable stigma, the pollen grain grows a pollen tube down through the style to reach the ovary. The male germ-cell travels through this tube and fuses with the egg cell in the ovule (fertilisation), forming a zygote. The zygote divides repeatedly to form an embryo inside the ovule. The ovule then develops a tough coat and becomes a seed, while the ovary grows and ripens into a fruit. The petals, sepals, stamens, style and stigma usually shrivel and fall off. Under suitable conditions the seed germinates, and the embryo grows into a new seedling.
Q2. Explain why sexual reproduction generates more variation than asexual reproduction, and why this matters.
ANSWERIn asexual reproduction a single parent copies its DNA, so offspring differ only by the few minor copying errors and are almost identical to the parent. In sexual reproduction, gametes from two different individuals fuse, and each individual already carries its own set of accumulated variations. Combining these through fertilisation produces entirely new combinations of variations in each offspring, so the offspring are genetically diverse. To keep the chromosome number constant, gametes are made by meiosis, which halves the chromosomes; fertilisation then restores the full number. This greater variation matters because, if the environment changes, some individuals are more likely to possess characters that help them survive and reproduce, ensuring the survival of the species and providing the raw material for evolution.
Q3. Describe the structure and functions of the human female reproductive system.
ANSWERThe female reproductive system consists of a pair of ovaries, two oviducts (fallopian tubes), the uterus, the cervix and the vagina. The ovaries produce the female germ-cells (eggs) and also secrete hormones; a girl is born with thousands of immature eggs, and from puberty one egg matures roughly every month. The released egg travels through the thin oviduct, where it may meet sperms that have entered through the vagina, so fertilisation occurs in the oviduct. The fertilised egg (zygote) divides to form an embryo that is implanted in the thick, blood-rich lining of the uterus, where it grows. The embryo obtains nourishment from the mother’s blood through the placenta, develops over about nine months, and the baby is finally pushed out by rhythmic contractions of the uterine muscles. If the egg is not fertilised, the lining is shed as menstruation.
MCQs & Assertion–Reason
1. The malarial parasite Plasmodium reproduces by:
For each Assertion–Reason question, choose: (A) Both true and the Reason correctly explains the Assertion; (B) Both true but the Reason is not the correct explanation; (C) Assertion true, Reason false; (D) Assertion false, Reason true.
A-R 1. Assertion: DNA copying is a basic event in reproduction.
Reason: DNA carries the information for body design that must be passed on to the offspring.
A-R 2. Assertion: Offspring produced by asexual reproduction show very little variation.
Reason: They are formed from a single parent without the fusion of gametes.
A-R 3. Assertion: The testes are located in the scrotum outside the abdominal cavity.
Reason: Sperm formation requires a temperature higher than the normal body temperature.
A-R 4. Assertion: A copper-T cannot protect a woman from sexually transmitted diseases.
Reason: A copper-T is placed in the uterus only to prevent pregnancy and forms no barrier against germs.
A-R 5. Assertion: Vegetative propagation is useful for growing banana and seedless oranges.
Reason: These plants have lost the capacity to produce viable seeds.
Mixing up pollination (transfer of pollen) with fertilisation (fusion of gametes); pollination always comes first.
Writing the vas deferens as a female organ — it belongs to the male system.
Saying a copper-T or oral pill prevents STDs — only barrier methods (condoms) help against infections.
Calling regeneration the same as reproduction — most organisms do not normally depend on being cut up to reproduce.
Forgetting that meiosis halves the chromosome number so it is restored after fertilisation.
How to score full marks in this chapter
Learn the examples that go with each asexual mode (Amoeba/Leishmania – binary fission, Plasmodium – multiple fission, yeast/Hydra – budding, Spirogyra – fragmentation, Hydra/Planaria – regeneration, Rhizopus – spores). For diagram questions, practise the labelled longitudinal section of a flower and the human reproductive systems. In contraception answers, group methods as barrier, hormonal, IUD and surgical, and clearly state which one also prevents STDs. Use precise terms — pollination, fertilisation, zygote, placenta, menstruation — to earn full marks.
Frequently Asked Questions
What is Class 10 Science Chapter 7 about?
Chapter 7, How do Organisms Reproduce?, explains how living things produce new individuals. It covers DNA copying and variation, asexual modes (fission, fragmentation, regeneration, budding, vegetative propagation, spore formation), sexual reproduction in flowering plants, the human reproductive systems, the menstrual cycle, contraception and reproductive health.
How is pollination different from fertilisation?
Pollination is the transfer of pollen grains from the anther to the stigma by wind, water or animals, with no fusion of gametes. Fertilisation is the later fusion of the male germ-cell with the egg inside the ovule to form a zygote. Pollination always happens first.
Why is variation useful for a species?
Variation produced during reproduction means that if the environment changes, some individuals carrying suitable variations can survive and reproduce, so the species continues. It also provides the raw material for evolution, even though a single variation may give no advantage to an individual.
Are these Class 10 Science Chapter 7 solutions free?
Yes. All ClearStudy NCERT Solutions for Class 10 Science are free and follow the official NCERT textbook for session 2026–27.
