Class 10 Science Chapter 7 — How Do Organisms Reproduce? (International Edition)

NCERT / RBSE Syllabus 2026–27 · Learn by doing · Includes three labelled diagrams

Author: Surendra Singh Chouhan — former Education Officer, Rajasthan. 34 years (1991–2025) in teaching, training and administration.
Based on: NCERT Class 10 Science textbook, Chapter 7, and the Board of Secondary Education, Rajasthan syllabus 2026–27.
Prepared: Compiled from the textbook, organised with AI assistance, reviewed by the author. All diagrams are original.
Published: 24 September 2026 · Last updated: 24 September 2026

Split an amoeba into two, and moments later both halves are living amoebas. Split a human being in half, and it simply dies.

Why the difference? And why does an organism need to reproduce at all — it is already managing nutrition, respiration and excretion just fine on its own?

How to read this — first you think or try it, then comes the explanation:
🔍 Wonder · 🧪 Try it · 📖 Understand · 🔗 Apply · ✅ Check yourself
"Check yourself" has three levels — 1, 2, 3.

Contents

1. Foundation check
2. Why reproduction matters
3. Asexual reproduction
4. Sexual reproduction in plants
5. The human reproductive system — male
6. The human reproductive system — female
7. Reproductive health
8. Your ladder
9. How to draw the diagrams
10. Marking scheme
11. Common mistakes
12. Final test
13. Glossary
14. For parents and teachers
15. Beyond NCERT

Foundation check

1. What is cell division? (Class 9)
2. In which organelle is DNA found?
3. Does every organism need two parents to produce offspring?

Answers

1. One cell splitting into two or more cells. 2. The nucleus. 3. No. Many organisms — such as amoeba and yeast — reproduce alone. This chapter makes that distinction clear.

1. Why reproduction matters

🔍 Wonder — Thousands of chemical reactions keep the body running every second. So why does reproduction get treated as a separate "life process" — it isn't even needed for an individual organism to stay alive?

🧪 Try it — Compare one physical trait — eye colour, height — across your grandparents, parents and yourself. Think first — is everyone identical?

Answer — Never. Every generation carries small differences — this is called variation. Blood group, height, skin tone — many such traits pass from one generation to the next with slight change, never an exact copy.

📖 Understand — Reproduction's basic job is copying DNA. The DNA in a cell's nucleus makes a copy of itself, and a new cell or organism is built on that copy. But this copying is never perfectly accurate — a little variation creeps in every time.

This variation is exactly what allows a species to survive a changing environment. If every member of a species were identical, a single adverse event — a disease, say — could wipe the whole species out. The same underlying logic showed up in Chapter 6 — Control and Coordination: an organism keeps itself in balance internally, and reproduction is how it keeps its species going across generations.

🔗 Apply — This is why reproduction is described as maintaining the continuity of the species, not the survival of any one individual.

✅ Check yourself

Level 1 What is the basic unit of reproduction? — Answer: DNA copying.
Level 2 Why is variation beneficial for a species? — Answer: Some variations help individuals survive a changing environment, keeping the species alive overall.
Level 3 What would happen if DNA copying were always 100% accurate? — Answer: No variation would ever appear, and every offspring would be identical to the parent. If the environment changed, the entire species could be threatened at once — so the small inaccuracy in copying is actually beneficial to the species.

One more term before we continue: the special reproductive cells that combine during sexual reproduction — sperm and egg in animals, pollen and egg cell in plants — are called gametes. Asexual reproduction, which the next section covers, forms no gametes at all — that is exactly why its offspring are near-identical copies of a single parent, while sexual reproduction (Sections 3–5) mixes gametes from two parents and produces variation.

2. Asexual reproduction

🔍 Wonder — An amoeba has no mate and no flower, yet its numbers keep growing. How?

🧪 Try it — Plant a piece of potato with an "eye" (bud) in soil and water it for a week. Think first — will a new plant grow, and will it need a seed?

What happened? A new plant appeared with no seed at all — because the bud on the potato grew directly into a plant. This is called vegetative propagation.

📖 Understand — Reproduction that needs only a single parent is called asexual reproduction. The offspring is nearly an identical copy of the parent.

Method	Process	Example
Binary fission	A cell splits into two roughly equal halves (each parent produces exactly two offspring)	Amoeba, Paramecium
Multiple fission	A cell splits into many daughter cells at once, instead of just two	Malarial parasite (Plasmodium)
Budding	A bud forms on the parent's body and eventually separates	Yeast, Hydra
Spore formation	Thousands of tiny spores form and grow into new organisms under favourable conditions	Rhizopus (bread mould)
Regeneration	A cut-off piece of the body regrows into a complete new organism	Planaria (flatworm)
Fragmentation	The body breaks into pieces on its own, each piece becoming a new organism	Spirogyra (algae)

Vegetative propagation — a new plant grows directly from a root, stem or leaf, with no seed involved:

Kind	Method	Example
Natural	By roots	Sweet potato
	By stems	Ginger, potato
	By leaves	Bryophyllum
Artificial	Cutting — a piece of stem is planted directly	Rose, sugarcane
	Layering / grafting — a stem is rooted while still attached, or joined onto another plant's rootstock	Jasmine (layering), mango (grafting)

🔗 Apply — Farmers benefit from vegetative propagation: a plant with especially good fruit or flowers can be copied cheaply and quickly, without waiting for seeds.

✅ Check yourself

Level 1 Which method of reproduction does Hydra use? — Answer: Budding.
Level 2 How does vegetative propagation differ from growing from seed? — Answer: Vegetative propagation grows an identical plant directly from a root, stem or leaf (asexual); a seed is the result of sexual reproduction and carries variation.
Level 3 Why do gardeners grow an excellent rose variety from a cutting rather than from seed? — Answer: A plant grown from seed may vary because of sexual reproduction — traits could change. A cutting (vegetative propagation) is asexual, so the new plant matches the parent exactly — the same colour and fragrance are guaranteed.

3. Sexual reproduction in plants

🔍 Wonder — Why are flowers so colourful and fragrant — is that purely for beauty?

🧪 Try it — Take any large flower (a hibiscus works well) and identify the long tube-like structure at the centre (the pistil) and the thread-like structures around it (the stamens). Think first — which is the male part, which is female?

📖 Understand — The stamen is the male part — its anther produces pollen. The pistil is the female part — it has a stigma at the top, a style in the middle, and an ovary at the base, which contains ovules. A flower with both parts present is called bisexual (e.g. hibiscus); one with only a single part is unisexual (e.g. papaya, watermelon).

Pollination — pollen travelling from the anther to a stigma.

Type	Meaning
Self-pollination	Pollen from a flower reaches the stigma of the same flower
Cross-pollination	Pollen from one flower reaches the stigma of another — carried by wind, insects or water

Fertilisation — pollen on the stigma grows a tube down to the ovule, and fuses with the egg cell there to form a zygote. After this:

Ovule → seed · Ovary → fruit

🔗 Apply — Back to the opening question: colour and fragrance exist to attract insects, enabling cross-pollination — which brings more variation than self-pollination, as Section 1 explained.

✅ Check yourself

Level 1 What does the ovule become after fertilisation? — Answer: A seed.
Level 2 What is the difference between self- and cross-pollination? — Answer: In self-pollination, pollen reaches the same flower's stigma; in cross-pollination, pollen travels to another flower's stigma, often via wind, insects or water.
Level 3 Why is cross-pollination considered biologically better than self-pollination? — Answer: Cross-pollination mixes the genetic material of two different plants, producing more variation in the offspring — which improves a species' chance of surviving a changing environment, as covered in Section 1.

4. The human reproductive system — male

🔍 Wonder — Why do several physical changes appear suddenly during adolescence — a deeper voice, facial hair?

📖 Understand — Puberty (the onset of sexual maturity) begins around age 13–14 in boys. These changes are caused by the hormone testosterone, made by the testes. The testes sit outside the abdominal cavity, in the scrotum — at a temperature slightly lower than the rest of the body, because sperm production needs it that way. This hormone-driven adolescent change is the same principle covered for adrenaline and thyroxine in Chapter 6 — one hormone, effects across several organs.

Part	Function
Testes	Produce sperm and testosterone
Vas deferens	Carries sperm to the urethra
Seminal vesicle and prostate gland	Produce fluid that nourishes and helps sperm move
Urethra	Shared pathway for both urine and semen

✅ Check yourself

Level 1 Why is the scrotum located outside the body? — Answer: Sperm production requires a temperature slightly lower than normal body temperature.
Level 2 What does testosterone do? — Answer: It drives adolescent physical changes (deeper voice, facial hair) and supports sperm production.

5. The human reproductive system — female

🔍 Wonder — Why does a fixed monthly cycle occur in girls once adolescence begins?

Puberty begins around age 10–12 in girls — earlier than in boys — driven by two hormones released from the ovaries: estrogen and progesterone. Together they bring about adolescent body changes and drive the monthly cycle described below.

📖 Understand — The ovaries hold thousands of immature eggs from birth. From adolescence, one ovary releases an egg each month, which travels through the fallopian tube toward the uterus. Meanwhile, the uterus lining thickens and fills with blood — preparing to nurture an embryo.

If the egg is fertilised by sperm along the way, the zygote attaches to the uterine wall and begins to grow — this is pregnancy. If fertilisation does not happen, the thickened lining breaks down and is shed with blood — this is called menstruation, which repeats roughly every 28 days.

🔗 Apply — Menstruation is not an illness — it is a sign the body is working as it should: preparing for a possible pregnancy each month, and a natural clearing cycle when that preparation isn't needed.

✅ Check yourself

Level 1 Where does fertilisation occur? — Answer: In the fallopian tube.
Level 2 Why does menstruation happen? — Answer: When the egg is not fertilised, the thickened uterus lining is no longer needed, so it breaks down and is shed along with blood.
Level 3 Why does the uterus lining thicken every month even though fertilisation usually does not occur? — Answer: The body cannot know in advance whether fertilisation will happen in a given cycle, so it prepares every time as if it might. When fertilisation doesn't occur, that preparation is no longer needed, so it is shed.

6. Reproductive health

📖 Understand — Contraceptive methods are used for population control and health protection:

Type	Example
Barrier method	Condom — prevents sperm and egg from meeting
Chemical / hormonal method	Pills — alter hormone balance to prevent an egg forming
Surgical method	Sterilisation — permanently blocks the vas deferens or fallopian tube

A condom's extra benefit — it also protects against sexually transmitted diseases (STDs) such as HIV-AIDS, gonorrhoea and syphilis, which the other methods do not.

Why this matters beyond the individual: widespread awareness and use of contraception is also a key tool for population control — keeping a country's population growth in balance with its resources — which is exactly why reproductive health is taught as part of the school science syllabus rather than left out.

Health note: this section is educational only. For any question about contraception, reproductive health, or a symptom, please consult a qualified doctor.

✅ Check yourself

Level 1 Which contraceptive method also protects against STDs? — Answer: The condom.
Level 2 What is the difference between sterilisation and the pill? — Answer: Sterilisation is a surgical procedure that permanently blocks the vas deferens or fallopian tube; the pill temporarily alters hormone balance to prevent egg formation.

Your ladder

Level	Total	If you got this many right	You are
Level 1	6	5+	Familiar
Level 2	6	4+	Proficient — board-exam ready
Level 3	3	2+	Skilled

How to draw the diagrams

1. Binary fission / budding (Fig. 1) — Draw a round cell with the nucleus dividing in the middle, then two equal circles separating. For budding, show a small circle attached to a larger one. Label: nucleus, cell wall, new daughter cell.

2. Flower structure (Fig. 2) — Petals above the stem, a long central tube (the pistil — stigma on top, style in the middle, a round ovary at the base containing ovules), thread-like stamens around it, each ending in an anther. Labels required: stamen, anther, stigma, style, ovary, ovule. Common mistake: swapping stamen and pistil — remember, stamens are always outer and numerous; the pistil is central and single.

3. Female reproductive system (Fig. 3) — Two ovaries top-left and top-right, two tubes (fallopian tubes) running to a central pouch-shaped uterus, vagina below. Label: ovary, fallopian tube, uterus, vagina.

Marking scheme

(An example of a typical examiner's approach — not an official scheme.)

Question (5 marks): Draw a labelled longitudinal section of a flower and explain the process of pollination and fertilisation.

Labelled diagram — stamen, pistil, ovary, ovule. 2 marks
Definition and types of pollination. 1 mark
The process of fertilisation. 1 mark
How the seed and fruit form. 1 mark

Common mistakes

Common mistake	Correct fact
"Pollination and fertilisation are the same thing"	Pollination is pollen reaching the stigma; fertilisation happens later, inside the ovule.
"Self-pollination is always the best method"	Cross-pollination brings more variation, so it is considered biologically better.
"Menstruation is an illness"	It is a natural monthly cycle, not an illness.
"Every contraceptive method protects against STDs"	Only the condom also protects against STDs.
"Ovary and ovule are the same thing"	The ovary is an organ (becomes the fruit); the ovule is a structure inside it (becomes the seed).

Final test — mixed

7+ correct = chapter mastered.

1. Name the method of reproduction used by amoeba.
2. What is the male part of a flower called?
3. What does the ovary become after fertilisation?
4. Why is the scrotum located outside the body?
5. When does menstruation not occur?
6. Which contraceptive method also protects against STDs?
7. Why is variation beneficial to a species?
8. (Chapter 6) Which part of the human brain controls breathing?
9. (Chapter 5) Which three things are needed for photosynthesis?

Answers — 1. Binary fission | 2. Stamen | 3. Fruit | 4. Sperm production needs a slightly lower temperature | 5. When fertilisation occurs (during pregnancy) | 6. Condom | 7. It improves a species' chances of surviving a changing environment | 8. Medulla | 9. Carbon dioxide, water, sunlight

Glossary

English	Hindi	English	Hindi
Variation	विविधता	Stigma	वर्तिकाग्र
Binary fission	द्विखंडन	Fertilisation	निषेचन
Budding	मुकुलन	Zygote	युग्मनज
Vegetative propagation	कायिक प्रवर्धन	Testis	वृषण
Pollination	परागण	Ovary	अंडाशय
Stamen	पुंकेसर	Menstruation	रजोधर्म

For parents and teachers

Five-minute check: List the six methods of asexual reproduction. Explain the difference between stamen and pistil. Why does menstruation happen? Which contraceptive method protects against STDs?

To try at home: vegetative propagation from a potato bud (one week), and identifying stamen/pistil in a large flower — both safe and visible to the naked eye. Once practice is done, revisit the Class 10 Science Mega Test (200 MCQs) for revision.

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Part 2 — Beyond NCERT: A Closer Look at Reproduction

This section goes beyond the RBSE/NCERT Class 10 syllabus and is not required for the board exam. It draws only on government and internationally reputed university sources, for curious readers who want to see where this chapter leads.

Mutation: the small copying errors that drive evolution

The small inaccuracies in DNA copying that this chapter treats as "variation" are, in more technical language, called mutations. Genetics laboratories around the world — including India's own Department of Biotechnology — build on exactly this principle to develop new, higher-yielding crop varieties, working with variations that arise naturally or are induced deliberately in a controlled setting.

Pollinators under pressure — a live agricultural concern

Understanding pollination is not just a textbook exercise. Agricultural universities across the world treat the declining population of pollinating insects, especially bees, as a serious ongoing concern, because most food crops depend on insects for cross-pollination. Some crops, almonds being a well-documented example, are so dependent on managed bee colonies that entire hives are transported to farms during the flowering season purely to ensure pollination happens at all.

Self- versus cross-pollination in plant breeding

University plant-breeding departments deliberately choose between self- and cross-pollination depending on the goal. Self-pollination is used to keep a desirable trait pure and unchanging across generations — useful for maintaining a specific crop variety. Cross-pollination is used when breeders want to introduce new traits from a different variety, accepting more variation in exchange for the possibility of improvement — a real-world extension of exactly the trade-off this chapter describes between the two methods.

The menstrual cycle as a hormone feedback loop

The chapter describes the uterus lining thickening and shedding on a roughly monthly cycle. Physiology departments describe this cycle as being driven by a rising and falling sequence of hormones released from the brain's pituitary gland and the ovaries, each triggering the next stage in turn. This is the same feedback logic covered for thyroxine and iodine in the previous chapter, applied here to a cycle rather than a single steady level.

Reproductive health as public policy

Reproductive health is not only a matter of individual biology — it is also public health policy. India's Ministry of Health and Family Welfare periodically updates national guidance on family planning and reproductive health, and government-run health centres across the country provide contraceptive counselling and services free or at low cost. For authoritative, current guidance, government health portals remain the most reliable source.

Why sex exists at all — a question biologists still debate

Asexual reproduction is faster, needs no mate, and passes on a full set of successful genes unchanged. Sexual reproduction is slower, needs two parents, and only passes on half of each parent's genes. Evolutionary biologists at universities worldwide have long treated this as a genuine puzzle — often called the "cost of sex" — because on paper, asexual reproduction looks like the more efficient strategy. The leading explanation taught in university biology departments is that the variation sexual reproduction generates is what allows a species to keep pace with disease-causing organisms and a constantly shifting environment, even though it costs more per generation. This is the same variation-versus-cost trade-off this chapter introduces in Section 1, examined at a much deeper level.

External versus internal fertilisation — a comparison this chapter doesn't cover

NCERT Class 10 focuses on human (internal) fertilisation, but comparative zoology draws a sharp line between two broad strategies across the animal kingdom:

Strategy	Where fusion of gametes happens	Typical examples	Trade-off
External fertilisation	Outside the body, usually in water	Most fish, frogs	Produces huge numbers of eggs since most are lost to predators or currents
Internal fertilisation	Inside the female's body	Reptiles, birds, mammals (including humans)	Produces far fewer offspring, but each has a much higher chance of survival, since the embryo is protected

This is precisely why a frog can lay hundreds of eggs at once while a human pregnancy usually produces one offspring — internal fertilisation trades quantity for protection and, eventually, for the kind of prolonged parental care this chapter's human reproduction sections describe.

Hermaphroditism — when one animal is both male and female

The chapter distinguishes stamens and pistils as separate structures within one bisexual flower, but a comparable idea exists in the animal kingdom too. Certain animals, most famously the earthworm, are hermaphrodites — a single individual possesses both male and female reproductive organs. Even so, most hermaphroditic animals still exchange sperm with a partner rather than fertilising themselves, which zoologists treat as evolution's way of preserving the genetic-mixing benefit of sexual reproduction even in an organism that could, in theory, reproduce entirely alone.

Cloning — asexual reproduction, deliberately engineered

When Dolly the sheep was cloned in 1996 by researchers at the Roslin Institute in Scotland, it demonstrated — on a mammal, for the first time — a principle this chapter already covers in plants: an entire organism can, in principle, be grown from the genetic material of a single parent, with no fertilisation involved. Cloning is, at its core, an engineered form of the same asexual-reproduction logic behind vegetative propagation, just applied with far more sophisticated laboratory technique and, in animals, far more ethical and technical complexity.

Assisted reproductive technology — when fertilisation needs help

When natural fertilisation does not succeed, medical science offers In Vitro Fertilisation (IVF) — where an egg and sperm are combined in a laboratory dish rather than inside the body, and the resulting embryo is later placed in the uterus. IVF and related techniques are regulated in India under the Assisted Reproductive Technology (Regulation) Act, overseen by the Ministry of Health and Family Welfare, precisely because they touch on the same reproductive processes — gametes, fertilisation, embryo implantation — that this chapter introduces at the school level.

Embryonic development — what happens after implantation

The chapter stops at the zygote attaching to the uterine wall, but university embryology courses trace what follows in stages: the zygote divides repeatedly to form a ball of cells, which implants in the uterine lining (the event this chapter calls "pregnancy" beginning); over the following weeks it develops into an embryo with the beginnings of organs, and later into a foetus with recognisable human form, nourished throughout by the placenta — an organ this chapter does not name but which forms specifically to pass nutrients and oxygen from mother to developing child.

Hand-pollination — when farmers do the insect's job

The chapter explains that insects carry out cross-pollination naturally, but in some crops this process is done by hand. Vanilla, for instance, is pollinated by a single species of bee found only in its native Mexico; everywhere else it is commercially grown — including Madagascar, which produces most of the world's vanilla — farm workers pollinate each flower individually with a small tool, flower by flower, because no local insect performs the job. It is a striking real-world illustration of just how essential the pollination process this chapter describes actually is to global agriculture.

How we came to understand reproduction — a short history

For most of recorded history, many naturalists — including Aristotle — believed some simple organisms arose through spontaneous generation, appearing directly from non-living matter rather than from reproduction at all. In the 1660s, the Italian physician Francesco Redi challenged this with a controlled experiment on maggots and meat, showing flies would not appear unless other flies had access to lay eggs there first — one of biology's earliest deliberately controlled experiments. Around the same period, the Dutch tradesman Antonie van Leeuwenhoek, using microscopes he built himself, became the first person to observe sperm cells, opening an entirely new scale at which reproduction could be studied. It was not until Louis Pasteur's experiments in the 1860s that spontaneous generation was conclusively disproved for good, cementing the principle this chapter opens with — that every organism arises from the reproduction of a previous one, carrying forward its DNA with only small variations.

See also — related topics beyond this chapter

• Genetics and heredity — how the variation this chapter introduces is passed on and expressed (covered in Chapter 8)
• Evolution by natural selection — how variation, over many generations, drives the emergence of new species
• Cell division (mitosis and meiosis) — the cellular machinery underlying both asexual reproduction and gamete formation (Class 9 and 10 foundations)
• Endocrinology — the broader study of hormones, of which reproductive hormones are one branch (see Chapter 6)

Sources for this section

• ncert.nic.in — NCERT, Government of India
• ePathshala — Ministry of Education, Government of India
• mohfw.gov.in — Ministry of Health and Family Welfare, Government of India

Note: nothing from these sources has been copied into this text; all statements above are written in the author's own words for general educational understanding, and are not medical or professional advice.

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Continue reading
← Previous: Chapter 6 — Control and Coordination (6 marks)
→ Next: Chapter 8 — Heredity and Evolution (7 marks)

Related material

• Chapter 6 — Control and Coordination (English)
• Class 10 Science Mega Test — 200 MCQs
• All Class 10 Notes

Based on the Class 10 Science (Code 07) syllabus 2026–2027 of the Board of Secondary Education, Rajasthan, Ajmer — Chapter 7, marks weightage 8. Textbook: Science, NCERT. All diagrams are original.