NCERT Solutions for Class 9 Science Chapter 11: Reproduction: How Life Continues – Free PDF Download

Chapter 11, “Reproduction: How Life Continues,” is the core life-science chapter of the Class 9 Science “Exploration” (2026-27) textbook, covering asexual reproduction in simple organisms, vegetative propagation, flower structure, pollination, fertilisation, seed and fruit formation, and the basics of human reproduction, puberty, and reproductive health. These solutions were prepared by working through the official “Revise, Reflect, Refine” exercise (page 225) and every in-text feature of the chapter — Think It Over, Bridging Science and Society, Pause and Ponder, and the Let Us Explore/Experiment/Investigate/Find Out activities — and cross-checking the questions and answers against LearnCBSE, Vedantu, and other current 2026-27 “Exploration” edition sources so that wording, page numbers, and biology are accurate.

Last Updated: September 23, 2026

NCERT Solutions for Class 9 Science Chapter 11: Reproduction: How Life Continues

Revise, Reflect, Refine (NCERT Textbook, Page No. 225)

1. A flower’s anthers are removed before it matures. Later, pollen from another plant of the same species is dusted onto its stigma and seeds are produced. Which process has been ensured here?
(i) Self-pollination (ii) Cross-pollination (iii) Fertilisation (iv) Tissue culture
(ii) Cross-pollination. Removing the anthers stops the flower from pollinating itself, and since the pollen placed on the stigma comes from a different plant of the same species, the process ensured is cross-pollination.

2. Arrange the following stages of sexual reproduction in plants in the correct order:
(i) Pollen germination on stigma (ii) Fertilisation (iii) Pollination (iv) Formation of zygote
The correct order is: (iii) Pollination → (i) Pollen germination on stigma → (ii) Fertilisation → (iv) Formation of zygote. Pollen first lands on the stigma (pollination), it then germinates and grows a pollen tube down to the ovule, the male and female gametes fuse (fertilisation), and this fusion produces the zygote.

3. Assertion (A): The zygote formed after fertilisation immediately attaches to the uterus wall.
Reason (R): The uterus wall is always prepared to receive the zygote.
(i) Both A and R are true, and R is the correct explanation of A. (ii) Both A and R are true, but R is not the correct explanation of A. (iii) A is true, but R is false. (iv) A is false, but R is true.
(iv) A is false, but R is true. The zygote does not attach to the uterus wall immediately — it takes about a week, dividing repeatedly as it travels down the fallopian tube, before it implants in the uterus. Meanwhile, the uterine lining thickens with a fresh supply of blood vessels every menstrual cycle so that it is ready to receive and nourish an embryo if fertilisation occurs.

4. Why does asexual reproduction produce offsprings that are genetically identical to the parent?
Asexual reproduction involves only a single parent and no fusion of male and female gametes. The new individual is produced by mitotic (ordinary) cell division of the parent’s own cells, which copies the parent’s DNA exactly. Since there is no mixing of genetic material from two parents, the offspring is a genetic copy, or clone, of the parent.

5. Explain why the menstrual cycle stops during pregnancy.
During pregnancy, hormones (mainly progesterone, along with hCG from the developing embryo) keep the uterine lining thick and intact so that it can nourish and support the embryo. Since this lining is no longer shed every month, menstruation stops for the duration of the pregnancy.

6. Why are flowers that bloom at night white or light in colour as compared to flowers that bloom during the day?
Night-blooming flowers are usually white or pale so that they remain visible in dim light and can be easily located by night-active pollinators such as moths and bats. Many of them also release a strong scent, which compensates for the lack of bright colour and helps guide pollinators to the flower after dark. Day-blooming flowers, in contrast, rely on bright colours because there is enough daylight for pollinators like bees and butterflies to see them.

7. Why do vegetatively propagated plants tend to be more vulnerable to diseases than sexually reproduced plants?
Vegetatively propagated plants are produced asexually from a single parent, so they are genetically identical clones with almost no variation among them. If a disease-causing organism can infect one plant, it can infect all the genetically identical plants in the same way, since none of them carries a different combination of genes that might offer resistance. Sexually reproduced plants, on the other hand, show genetic variation, so some individuals may resist a disease that wipes out others.

8. If all flowers in a type of plant were only capable of self-pollination, how would it affect the genetic diversity over several generations? Explain.
If a plant could only self-pollinate, its offspring would keep inheriting gene combinations from the same single parent generation after generation, so genetic diversity within the population would steadily decrease. Over many generations, the plants would become increasingly genetically uniform. This reduced diversity would make the population less able to adapt to changing environmental conditions and more vulnerable to being wiped out entirely by a single disease or pest, since there would be little variation for natural selection to act on.

9. A farmer wants to produce a large number of genetically identical plants quickly. Suggest suitable reproduction methods and explain why they are effective.
The farmer should use asexual (vegetative) propagation methods such as cutting, layering, grafting, or tissue culture. These methods produce new plants directly from the vegetative parts of a single parent plant through mitotic division, so every plant produced is a genetic copy of the parent with exactly the same desirable traits (yield, taste, disease resistance, and so on). They are also much faster than raising plants from seed, since the new plant does not have to go through pollination, fertilisation, and seed germination. Tissue culture is especially effective when very large numbers of identical, disease-free plants are needed quickly, because thousands of plantlets can be grown from a tiny piece of parent tissue in a laboratory.

10. Suresh prepares slides with pollen grains in different sugar concentrations (0%, 2.5%, 5%, 7.5%, 10%) to study the germination of pollen.
(i) What are the different hypotheses which can be tested using this setup?
(ii) What parameters should be kept the same in this setup?
(i) Possible hypotheses: pollen germination depends on the concentration of the sugar solution; there is an optimum sugar concentration at which pollen germination is maximum; and very low or very high sugar concentrations inhibit pollen germination.
(ii) To make sure sugar concentration is the only variable being tested, the following must be kept the same across all slides: the type and source of pollen grains, the volume of solution placed on each slide, the temperature and other environmental conditions, the time allowed for germination before observation, the light conditions, and the method used to prepare each slide.

11. Look at the picture given below and think in line with the given prompts and find out which type(s) of pollination might have been followed in these flowers – tomato, wheat, and papaya.
Tomato flowers have anthers positioned so close around the stigma that pollen falls directly onto it, so self-pollination is likely. Wheat flowers are known to be pollinated while still closed (cleistogamy), so self-pollination occurs before the flower even opens. Papaya plants bear male and female flowers on separate plants, so cross-pollination is essential — pollen must be carried from a male flower on one plant to a female flower on a different plant for fertilisation to occur.

12. In the lower Himalayan region of northern India, apples are an important cash crop. Apple fruit yield is declining, linked to climate change and a fall in natural pollinator populations. A researcher-farmer group compared two orchards: Place A, relying only on natural pollinators, and Place B, using managed beekeeping alongside natural pollinators. Fruit setting and fruit drop were recorded for both.
(i) What are the hypotheses the researcher-farmer group has thought of for this investigation?
(ii) What are the different parameters in the experiment?
(iii) Compare and analyse the data of two experimental orchards, Places A and B, in terms of high yields of apple fruits.
(iv) Based on your analysis, what do you infer from the data?
(i) Hypotheses: managed bee colonies increase pollination efficiency; better pollination leads to higher fruit setting and lower fruit drop; and a decline in natural pollinators reduces apple yield.
(ii) The independent variable is the type of pollination (natural pollinators only, versus natural pollinators plus managed beekeeping); the dependent variables are the fruit-setting rate and the fruit-drop rate; the controlled variables are the apple variety, soil, water, climate, and all other farming practices, which are kept the same at both sites.
(iii) Place A (natural pollination only) shows lower fruit setting and higher fruit drop, giving an overall lower yield. Place B (with managed bee colonies) shows higher fruit setting and lower fruit drop, giving an overall higher yield.
(iv) It can be inferred that adding managed bee colonies improves pollination efficiency, which increases fruit setting and reduces fruit drop. Beekeeping is therefore an effective strategy to raise apple yields, particularly in regions where wild pollinator populations are declining.

13. A student claims, “In humans, ovulation always happens on day 14 of the menstrual cycle.” Critically examine this claim and state whether the claim is correct or not. Give at least two reasons for your answer.
The claim is not correct. First, day 14 is only an approximation based on an “average” 28-day cycle; menstrual cycle length varies considerably between individuals (commonly anywhere from about 21 to 35 days), so ovulation timing shifts accordingly and is not fixed at day 14 for everyone. Second, even within the same person, ovulation timing can vary from cycle to cycle due to factors such as stress, illness, changes in hormone levels, body weight, and lifestyle, so it cannot be treated as occurring on a fixed calendar day every time.

In-Text Questions (Think It Over, Bridging Science and Society, Pause and Ponder, and Let Us Explore/Experiment/Investigate/Find Out Activities)

Think It Over (Page 208), Question 1: When does a farmer prefer asexual or sexual methods of reproduction for crops production?
A farmer prefers asexual (vegetative) propagation — such as stem cuttings in sugarcane, tubers in potato, or suckers in banana — when identical plants with a known set of desirable traits are wanted quickly and uniformly, or when a crop does not reliably produce viable seed. Sexual reproduction through seed is preferred when the farmer wants genetic variation, for example to develop new or hybrid varieties, or is growing crops such as wheat, rice, and maize that are conventionally raised from seed and benefit from the disease resistance and adaptability that genetic variation provides.

Think It Over (Page 208), Question 2: Why do you think most complex animals and flowering plants use sexual reproduction, while many simple organisms, like yeast and Hydra, mainly reproduce asexually?
Simple organisms such as yeast and Hydra have simple body plans and short life cycles, so asexual reproduction — which is fast, energy-efficient, and does not require a partner — lets them multiply rapidly when conditions are favourable. Complex organisms such as flowering plants and animals have longer life cycles and more complex bodies that must survive in changing environments, so they rely on sexual reproduction because it produces genetically varied offspring; this variation improves the chances that at least some offspring can adapt to new conditions, resist disease, and avoid extinction.

Think It Over (Page 211), Question 3: Are there other methods of asexual reproduction in organisms?
Yes. Besides budding and vegetative propagation, other common modes include binary fission, in which a single-celled organism such as Amoeba divides into two roughly equal daughter cells; multiple fission, in which an organism such as Plasmodium divides into many daughter cells simultaneously; fragmentation, in which the body of an organism such as Spirogyra breaks into pieces that each grow into a new individual; spore formation, in which organisms such as Rhizopus and ferns produce spores that germinate into new individuals under favourable conditions; and regeneration, in which organisms such as Planaria and starfish can regrow a complete new individual from a body fragment.

Bridging Science and Society (Page 212), Question 1: Do you know any fungus that can degrade plastic?
Yes. Certain fungi are known to break down some types of plastic. Aspergillus tubingensis, for instance, can degrade polyurethane plastic, and Pestalotiopsis microspora — found in the Amazon rainforest — has been studied for its ability to use plastic as a food source, even in low-oxygen conditions. This makes such fungi of interest for tackling plastic pollution.

Bridging Science and Society (Page 213), Question 2: How many combinations of characters can gametes carry?
The number of possible gene combinations a gamete can carry depends on the number of chromosome pairs the organism has, because each pair is distributed independently into gametes during meiosis. This is given by the formula 2ⁿ, where n is the number of chromosome pairs. For example, an organism with 2 pairs of chromosomes can produce 2² = 4 different combinations, while in humans, who have 23 pairs of chromosomes, this works out to 2²³ = 8,388,608 possible combinations — one reason gametes, and hence offspring, show so much genetic variety.

Bridging Science and Society (Page 214), Question 3: Flowers also enhance the aesthetics of the plants as they are coloured and/or fragrant. How are these features of flowers useful for reproduction?
The bright colours and pleasant fragrance of flowers are not just decorative — they act as visual and chemical signals that attract pollinators such as insects, birds, and bats. By drawing these pollinators to visit the flower, colour and fragrance increase the chances that pollen will be carried from one flower to another, which is essential for pollination and successful sexual reproduction in flowering plants.

Bridging Science and Society (Page 215), Question 4: Can you guess the function of the most attractive part of a flower, the coloured petals?
The coloured petals, together with any scent they produce, function mainly to attract pollinators such as insects and birds. By making the flower conspicuous and appealing, petals increase the likelihood that a pollinator will visit and, in doing so, transfer pollen and enable fertilisation.

Bridging Science and Society (Page 216), Question 5: What do you think will happen if pollination does not occur?
If pollination does not occur, no pollen reaches the stigma, so fertilisation cannot take place. Without fertilisation, the ovule does not develop into a seed and the ovary does not develop into a fruit, so the plant fails to reproduce sexually and no new seeds or fruit are produced from that flower.

Pause and Ponder (Page 217), Question 1: In a China rose (Hibiscus or gudhal) plant, a pollen tube grows and continues through the style after pollen lands on the stigma. Which process is about to happen next?
The next process is fertilisation. The pollen tube grows down through the style carrying the male gametes, reaches the ovule inside the ovary, and one male gamete fuses with the female gamete (egg cell) to form a zygote.

Pause and Ponder (Page 217), Question 2: Look at the pictures of Calotropis (madar) seeds and dandelion seeds. Can you guess what kind of seed dispersal these seeds are adapted for?
Both Calotropis and dandelion seeds are adapted for dispersal by wind. Their seeds are very light in weight and bear fine, hair-like or feathery structures that increase air resistance, allowing them to float and be carried by wind currents over long distances away from the parent plant.

Pause and Ponder (Page 217), Question 3: A farmer plants two varieties of maize side by side, but notices that seeds form only when pollen from one variety reaches the stigma of the other. What type of pollination is this?
This is an example of cross-pollination, since seed formation depends on pollen being transferred from the flower of one plant (or variety) to the stigma of a flower on a genetically different plant, rather than pollen fertilising the same flower or plant.

Pause and Ponder (Page 218), Question 4: Why do animals with external fertilisation generally produce more eggs than animals with internal fertilisation?
In external fertilisation, eggs and sperm are released into the surrounding environment, typically water, where fertilisation is left largely to chance and many gametes are lost to currents, predators, or unfavourable conditions before fertilisation can occur. Producing a very large number of eggs improves the odds that enough of them will be fertilised and survive. In internal fertilisation, gametes meet and fuse inside the protected environment of the female’s body, so far fewer eggs are needed to ensure successful fertilisation and development.

Pause and Ponder (Page 218), Question 5: In animals, which fertilisation method are the gametes more protected?
Gametes are more protected in internal fertilisation, since fertilisation and the earliest stages of embryo development occur inside the female’s body, sheltered from predators, temperature changes, and other external hazards that gametes released into the open environment would face during external fertilisation.

Pause and Ponder (Page 222), Question 6: Ravi suddenly notices that he is growing taller rapidly, his shoulders are broadening, and his voice cracks. What stage of life is he entering?
Ravi is entering adolescence, the stage of puberty, during which the body undergoes rapid physical and hormonal changes such as a growth spurt, broadening of the shoulders, and deepening of the voice as the reproductive organs mature.

Pause and Ponder (Page 222), Question 7: Rina’s period occurs every 28 days. Her last period was on the 5th of March. On which day is she most likely to get her next period?
Counting 28 days forward from 5th March gives 2nd April, so Rina is most likely to get her next period on or around 2nd April.

Pause and Ponder (Page 222), Question 8: A human zygote is just formed. How many chromosomes does it have?
A human zygote has 46 chromosomes, arranged as 23 pairs — 23 chromosomes contributed by the egg from the mother and 23 chromosomes contributed by the sperm from the father.

Pause and Ponder (Page 223), Question 9: What protective devices can be used during sexual activity to reduce the spread of STIs?
Condoms are the main protective device used during sexual activity to reduce the spread of sexually transmitted infections (STIs), as they form a physical barrier that limits the exchange of body fluids that can carry infection-causing organisms.

Pause and Ponder (Page 223), Question 10: If a couple uses oral contraceptive pills but not condoms, which risks remain and why?
The risk of sexually transmitted infections (STIs) remains, because oral contraceptive pills work by preventing ovulation or fertilisation and so only protect against pregnancy — they do not act as a physical barrier and offer no protection against infections passed on through sexual contact. Only barrier methods such as condoms reduce that risk.

Pause and Ponder (Page 224), Question 11: In many animals, the young ones can walk or find food soon after birth, but human babies are completely dependent for a long time. What might be some advantages and disadvantages of this for humans as a species?
The advantages include that a long period of dependency gives parents time to protect and nourish the infant while its brain and body continue developing outside the womb, and it allows the child extended time to learn language, complex motor skills, and social behaviour, which supports the advanced learning ability that distinguishes humans. The disadvantages include that a human infant cannot survive without sustained parental care, and that parents must invest a great deal of time, energy, and resources over many years, with the infant being at greater risk if that care is not available. On balance, this prolonged dependency is thought to support the extended brain development and learning that make humans a highly adaptable species.

Let Us Explore – Activity 11.1 (Page 209): Study and observe the methods of vegetative propagation — cutting, grafting, and layering.
Cutting: a healthy stem cutting is taken from a parent plant, its lower leaves are removed, and it is planted at an angle in soil mixed with compost; with regular watering, roots and new leaves develop from the nodes to form a new plant identical to the parent. Grafting: a cutting (scion) from one plant is joined onto a slit made in a rooted plant (stock), the joint is bound and protected, and with care the two parts fuse and grow as a single plant combining traits of both. Layering: a flexible stem is bent down and its middle portion is buried in soil while still attached to the parent; once roots develop from the buried part, it is cut away to grow as an independent new plant. All three methods are effective ways to propagate plants that are genetically identical to the parent, useful in agriculture and horticulture for quickly multiplying plants with desirable traits.

Let Us Explore – Activity 11.2 (Page 211): Study the process of budding in yeast under a compound microscope.
Under the microscope, small round outgrowths (buds) can be seen forming on parent yeast cells; as a bud develops, the nucleus of the parent cell divides, one daughter nucleus moves into the bud, and the bud grows until it detaches to become a new, independent yeast cell. This shows that yeast reproduces asexually by budding, multiplying rapidly through mitotic cell division under favourable conditions and producing offspring genetically identical to the parent.

Let Us Experiment – Activity 11.3 (Page 211–212): Study the growth of mould on moist bread or roti.
A piece of moist bread left in warm, dark conditions develops white, cotton-like growth that later turns black or greenish. Under the microscope, thread-like hyphae forming a network (mycelium) are visible, with round sporangia (spore sacs) at the tips containing numerous tiny spores. These features match Rhizopus (common bread mould), which is distinguished from Aspergillus by its spherical sporangia, as Aspergillus instead bears spores in chains. This shows that bread mould reproduces asexually: spores present in the air settle on the moist bread, germinate, and grow into new thread-like fungal structures.

Let Us Explore – Activity 11.4 (Page 213): Understand how variation arises due to random combination of chromosomes, using coloured beads to represent chromosome pairs.
Picking one bead at random from each of several pairs of differently coloured beads, to simulate the random selection of one chromosome from each homologous pair during gamete formation, produces many different colour combinations; with three pairs, up to eight different combinations are possible, matching the 2ⁿ rule. This demonstrates that random assortment of chromosome pairs during reproduction creates unique genetic combinations in each individual. In humans, with 23 pairs of chromosomes, this random mixing can generate an enormous number of possible combinations, which is essential for genetic variation, adaptation to changing environments, and the process of evolution.

Let Us Explore – Activity 11.5 (Page 214–215): Observe and identify the different parts of flowers by studying various flowers from the surroundings.
Examining a typical flower shows that the sepals are usually green and protect the flower bud before it opens; the petals are colourful and attract pollinators; the stamen, made up of an anther and a filament, is the male part that produces pollen; and the pistil (carpel) is the female part, consisting of the stigma, style, and ovary, with the ovary containing ovules. Each part of the flower has a specific role, and together they make the flower well adapted for pollination, fertilisation, and seed formation.

Let Us Investigate – Activity 11.6 (Page 215): Study the role of pollination (self and cross-pollination) in fruit formation using different flower treatments in a pea plant.
An intact flower bud, whether left open or wrapped in a muslin bag, still forms fruit because self-pollination can occur within its own closed structure before the flower opens; but a flower bud with its stamens removed and then wrapped in a muslin bag (preventing pollen from any outside source from reaching it) fails to form fruit, showing that pollination did not occur. In contrast, a flower with its stamens removed but left unwrapped, or an untreated flower, still forms fruit, since pollen from another flower can reach its stigma. This shows that pollination — the transfer of pollen from stamen to stigma, whether from the same flower or another flower — is essential for fertilisation and fruit formation.

Let Us Find Out – Activity 11.7 (Page 217), Question 1: Compare and analyse wind-pollinated grasses (which release about 5,00,000–10,00,000 pollen grains per flower and form roughly 50–200 seeds) and insect-pollinated plants such as sunflower (which release about 20,000–40,000 pollen grains per flower and form roughly 800–1,000 seeds), in terms of pollen-to-seed ratio and pollination efficiency.
Wind-pollinated plants have a very high pollen-to-seed ratio, since huge numbers of pollen grains are released into the air but only a small fraction ever reach a stigma, so relatively few seeds form per flower despite the massive pollen output. Insect-pollinated plants have a much lower pollen-to-seed ratio because pollinators carry pollen directly and efficiently from one flower to another, so a smaller number of pollen grains produces a larger number of seeds. Wind pollination is therefore a comparatively inefficient but high-volume strategy, while insect pollination is a more targeted and efficient one.

Let Us Find Out – Activity 11.7 (Page 217), Question 2: Explain why producing a very large number of pollen grains can still be an effective pollination strategy.
Even though wind carries pollen in a random, undirected way and most pollen grains never reach a stigma of the same species, releasing an extremely large number of pollen grains increases the statistical chance that at least some of them will, by chance, land on a suitable stigma. This “wastage” is compensated for by sheer quantity, making wind pollination a reliable, if inefficient, reproductive strategy for plants that do not depend on animal pollinators.

Why This Chapter Matters

Reproduction: How Life Continues connects directly to the cell biology and heredity concepts students meet elsewhere in the Class 9 Science syllabus — cell division underlies both asexual reproduction and gamete formation, while the chapter’s discussion of chromosome combinations and genetic variation lays the groundwork for the study of heredity and evolution in later classes. Understanding pollination, fertilisation, and vegetative propagation also has practical value for agriculture, from grafting fruit trees to using pollinators like bees to raise crop yields, and the sections on puberty, the menstrual cycle, and reproductive health give students accurate, age-appropriate scientific knowledge about their own bodies. Together, these threads make this chapter a bridge between plant and animal biology and a foundation for more advanced biology topics in Class 10 and beyond.

More on This Chapter

Extra Questions | Revision Notes | Formulas Handbook

Frequently Asked Questions

What is the difference between self-pollination and cross-pollination?
In self-pollination, pollen from the anther of a flower lands on the stigma of the same flower or another flower on the same plant, producing offspring genetically similar to the parent. In cross-pollination, pollen is transferred from the anther of a flower on one plant to the stigma of a flower on a genetically different plant of the same species, usually with the help of agents such as wind, water, insects, or birds, producing offspring with greater genetic variation.

Why do asexually and sexually produced offspring differ in genetic diversity?
Asexual reproduction involves a single parent and ordinary cell division, so the offspring are genetic clones of the parent with no new variation. Sexual reproduction involves the fusion of gametes from two parents, each carrying a unique, randomly assorted combination of chromosomes, so the offspring inherit a new mix of genes from both parents. This is why sexually produced offspring show far more genetic variation than asexually produced ones.

How many chromosomes does a human zygote have, and where do they come from?
A human zygote has 46 chromosomes in 23 pairs — 23 chromosomes from the mother’s egg and 23 chromosomes from the father’s sperm — formed the moment the two gametes fuse during fertilisation.

Does ovulation always happen on day 14 of the menstrual cycle?
No. Day 14 is only a textbook approximation based on an average 28-day cycle. Actual cycle length varies between individuals and can even vary from cycle to cycle in the same person due to factors like stress, health, and hormone levels, so ovulation is not fixed to a specific calendar day for everyone.

Why are wind-pollinated flowers usually small and dull while insect-pollinated flowers are large and colourful?
Wind-pollinated flowers do not need to attract anything, since pollen is simply carried by air currents, so they save energy by staying small, dull-coloured, and often scentless while producing enormous amounts of light, dry pollen. Insect-pollinated flowers rely on attracting pollinators, so they invest energy in bright colours, fragrance, and nectar to draw insects, birds, or bats, which then carry pollen more precisely and efficiently between flowers.

Written by Satish

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