Where Mindful Learning Begins
Where Mindful Learning Begins
Complete NCERT Solutions for Chapter 11 of the new Class 9 Science Exploration textbook (CBSE 2026-27) — every Think It Over, Activity, Pause & Ponder, Threads of Curiosity, Revise Reflect Refine, and Journey Beyond question on this one page, with full reasoning for every answer.
Reproduction — How Life Continues covers asexual reproduction (budding, fragmentation, spore formation, vegetative propagation) and sexual reproduction in both plants and humans, including the structure and function of reproductive organs, fertilisation, and adolescence. This chapter is a frequent source of Class 9 Science important questions and case-based questions, and these solutions work through every NCERT question with full biological reasoning, not just labelled diagrams.
Reproduction: How Life Continues explores the biological process by which every living being produces new individuals of its own kind. The chapter contrasts asexual reproduction — budding, spore formation, and vegetative propagation, which involve a single parent and produce genetically identical clones — with sexual reproduction, where meiosis and the fusion of gametes from two parents create genetic variation. It then follows this idea from flowers (pollination, fertilisation, fruit and seed formation) through the wide variety of reproductive strategies in animals, all the way to the human reproductive system, the menstrual cycle, pregnancy, childbirth, and reproductive health. Every question is solved here, section by section, exactly as the textbook presents them.
Vegetative propagation, budding in yeast and hydra, and spore formation in fungi — all producing genetically identical clones through mitosis.
Meiosis, gametes, pollination, fertilisation, and how mixing genetic material from two parents creates the variation species need to adapt.
The male and female reproductive systems, the menstrual cycle, pregnancy, childbirth, and reproductive health including contraception and STIs.
Asexual (vegetative) methods — cutting, grafting, layering, or tissue culture — are preferred when a farmer wants to rapidly multiply a plant that already has desirable traits (a particular high-yield fruit variety, for instance) and keep those exact traits unchanged in every new plant, since asexual reproduction produces genetically identical clones. This is especially useful for fruit trees and crops that take a long time to grow from seed, don't "breed true" from seed, or produce few viable seeds of their own.
Sexual reproduction (growing from seed) is preferred when a farmer wants genetic variation — for example, to breed new varieties combining desirable traits from two parent plants, to develop hardier or higher-yielding hybrids, or simply because most grain and vegetable crops are conventionally and economically grown from seed on a large scale.
Answer: sexual reproduction combines genetic material from two parents, producing offspring with new combinations of characteristics — this variation is valuable for complex organisms because it helps a population adapt to changing environments, resist new diseases, and evolve over time, which matters most for organisms with longer life spans and slower reproduction, since such a population cannot recover quickly if wiped out by a single unfavourable change.
Simple organisms like yeast and hydra often benefit more from speed than variation — asexual reproduction lets them multiply rapidly into large numbers of identical individuals without needing to find and combine with a partner, favouring fast population growth whenever conditions are favourable.
Key points to record for each technique:
Conclusion: all three are methods of vegetative (asexual) propagation — since only one parent plant is involved, each method produces a genetically identical copy of the desired parent variety, which is why they are so widely used in horticulture and agriculture.
Observation: yes — small, round outgrowths (buds) can be seen emerging from the parent yeast cells, sometimes with several buds attached at different stages, matching Fig. 11.6.
What this indicates: these buds show that the yeast cell is reproducing asexually by budding — a new daughter cell forms as an outgrowth on the parent cell, gradually enlarges, and eventually separates to live independently. This is direct visual evidence of asexual reproduction in a unicellular organism.
Observation: after a few days, thread-like structures (hyphae) with a round sac at the tip, containing tiny round spores, grow on the bread/roti surface — matching the Rhizopus and Aspergillus structures shown in Fig. 11.8.
Where the mould came from: it was not present when the bread was fresh — it grew from fungal spores that were already floating in the air and settled onto the moist bread, germinating once warmth and moisture became available. This supports Louis Pasteur's finding that new life always arises from pre-existing life, never spontaneously from non-living matter.
Conclusion: fungi reproduce asexually by producing enormous numbers of lightweight spores that disperse through air currents and germinate into a new colony wherever conditions are favourable.
With 3 pairs of beads, each pair independently contributes one of its two beads to a combination:
With 23 pairs of chromosomes (as in humans), the number of possible combinations becomes:
And this is even before accounting for crossing over or the random combination of gametes from two parents at fertilisation, which multiplies the possibilities further. This explains why siblings (other than identical twins) are never genetically identical to each other or to either parent.
Expected findings: sepals (usually green, outermost) and petals (usually the most colourful) are present in almost every flower you examine; stamens (male part) and pistil (female part) are present in most complete flowers, though some flowers are incomplete and naturally lack one or more parts (unisexual flowers). Cutting the ovary in transverse and longitudinal section under a dissecting microscope typically reveals ovules arranged inside it.
| Flower part | Inferred function |
|---|---|
| Sepal | Protects the flower bud before it opens |
| Petal | Attracts pollinators with colour, and sometimes scent |
| Stamen | Produces and releases pollen grains (male gametes) |
| Pistil | Receives pollen on its stigma; its ovary houses the ovules that develop into seeds after fertilisation |
| Treatment | Fruit formation |
|---|---|
| Flower bud (wrapped, stamens intact) | Yes |
| Flower bud with removed stamens (wrapped) | No |
| Flower with removed stamens (wrapped) | No |
| Flower (wrapped, stamens intact) | Yes |
| Flower (without muslin bag, stamens intact) | Yes |
Where fruits fail to form: only in the two treatments where the stamens were removed before pollination could occur (whether at the bud stage or the open-flower stage) — in both cases, the muslin bag also prevents any outside pollen from reaching the stigma.
Inference: the transfer of pollen (containing male gametes) from the anther to the stigma is essential for fruit formation. When stamens are removed and outside pollen is also blocked, pollination cannot happen at all, and no fruit develops — this confirms that pollination is a necessary first step towards fertilisation and fruit formation.
Pollen-to-seed ratio: wind-pollinated grasses release roughly 5,00,000–10,00,000 pollen grains per flower to form only about 50–200 seeds — a ratio of roughly 2,500:1 to as high as 20,000:1. Insect-pollinated plants release only about 20,000–40,000 pollen grains per flower to form about 800–1,000 seeds — a much tighter ratio of roughly 20:1 to 50:1.
Why the strategies differ: insect pollination is far more targeted (pollinators carry pollen directly to a compatible stigma), while wind pollination is essentially a numbers game — pollen is released randomly into the air, and only a tiny fraction happens to land on a compatible stigma, so vast quantities must be produced to ensure enough successful pollinations.
Why producing huge amounts of pollen is still effective: even though most wind-dispersed pollen never reaches a stigma, producing pollen is relatively low-cost for the plant compared to the cost of attracting pollinators (nectar, bright colour, fragrance). Since wind-pollinated plants don't need to invest in attracting anything, producing extremely large numbers of pollen grains compensates for the low probability of success per grain — quantity (wind) and precision (insects) are both evolutionarily successful strategies, just very different ones.
Answer: Fertilisation is about to happen. The male gamete travels down the pollen tube through the style and into the ovary, where it reaches an ovule and fuses with the egg cell inside it, forming a zygote.
Answer: both madar and dandelion seeds have fine, feathery/silky hair-like tufts attached to them, which is a clear adaptation for wind dispersal — these light, hairy structures let the seeds be carried away by air currents, sometimes over long distances, reducing competition with the parent plant and helping colonise new areas.
Answer: this is cross-pollination — the pollen is being transferred from the anther of a flower on one plant to the stigma of a flower on a different plant of the same type (both are maize, just different varieties), matching the chapter's definition of cross-pollination exactly.
Answer: in external fertilisation, eggs and sperm are released directly into the open environment (usually water), where fertilisation is left largely to chance and the resulting eggs are highly exposed — many are swept away by currents, never get fertilised, or are eaten by predators. To compensate for this low survival rate, animals like fish and frogs produce very large numbers of eggs, so that enough survive to develop into offspring. Animals with internal fertilisation protect the fertilised egg/embryo inside the mother's body, so far fewer eggs are needed to ensure some offspring survive.
Answer: Internal fertilisation. Since fertilisation happens inside the female's body, the gametes and the resulting fertilised egg/embryo are shielded from external threats such as predators, water currents, and harsh conditions — unlike external fertilisation, where gametes are released directly into the open environment.
Answer: Ravi is entering puberty/adolescence — the stage where the body undergoes rapid physical changes and the reproductive organs mature (sexual maturation), triggered by reproductive hormones. In boys, these changes typically include a growth spurt, broadening shoulders, and a deepening (cracking) voice.
March has 31 days, so from 5th March to 31st March is 26 days. The remaining 2 days of the 28-day cycle fall in April.
Rina is most likely to get her next period around 2nd April.
Answer: 46 chromosomes. The sperm contributes 23 chromosomes and the egg contributes 23 chromosomes; their fusion at fertilisation restores the full (diploid) number of 46 chromosomes in the zygote, matching the number found in normal human body cells.
Answer: condoms (and vaginal covers) act as a physical barrier that prevents direct contact between body fluids/tissues, making them the main protective device that reduces the transmission of Sexually Transmitted Infections (STIs) during sexual activity, while also helping prevent unwanted pregnancy.
Answer: the risk of contracting or transmitting Sexually Transmitted Infections (STIs), including HIV, remains. Oral contraceptive pills work by altering hormones to prevent ovulation/pregnancy — they create no physical barrier between partners, so they offer no protection against infections spread through direct sexual contact. Only barrier methods like condoms reduce this particular risk.
Advantages: an extended period of dependency gives the brain much more time to grow and develop after birth, and gives the young one a long window to learn complex behaviour, language, and social skills from parents and the community — contributing to humans' exceptional capacity for learning, culture, and cooperation, which are major evolutionary advantages.
Disadvantages: prolonged dependency requires a huge, sustained investment of parental time, energy, and resources (feeding, protection, teaching) over many years, and leaves human infants and children highly vulnerable, since they cannot survive or escape danger on their own — this makes strong social structures (family, community) essential for successful child-rearing.
Answer: The father. Every person has two sex chromosomes — females have XX and males have XY. The mother always contributes one of her X chromosomes to the baby (since she only has X chromosomes to give), while the father can contribute either an X chromosome or a Y chromosome (since he has one of each).
If the father's sperm carries an X chromosome, the baby will be XX (female); if it carries a Y chromosome, the baby will be XY (male). So it is the father's genetic contribution that determines the baby's biological sex, not the mother's.
Answer: this is a genuinely open question that biologists still actively study. In organisms that reproduce by simple division (an amoeba splitting in two, or budding in yeast), there isn't a single "parent" that keeps ageing separately from its "offspring" the way there is in humans — the original cell's contents are essentially divided between the resulting cells, so in one sense the "parent" doesn't continue as a separate, ageing individual at all; it becomes the offspring.
However, real populations of such cells do show signs of accumulated cellular damage (such as damaged proteins or cell components) building up over successive divisions, and some individual cells can show a reduced ability to divide over time. So while these organisms may not visibly "age" the way whole multicellular bodies do, accumulated damage and quality control during division still matter at the cellular level — making this a genuinely fascinating, still-active area of biological research rather than a settled answer.
Answer: (ii) Cross-pollination. Removing the anthers prevents self-pollination; deliberately dusting pollen from a different plant of the same species onto the stigma ensures the pollen came from another plant, matching the definition of cross-pollination.
Correct order:
(iii) Pollination → (i) Pollen germination on stigma → (ii) Fertilisation → (iv) Formation of zygote.
Pollen must first be transferred to the stigma (pollination); it then germinates and grows a pollen tube down through the style; the male gamete then fuses with the egg cell (fertilisation), which results in the formation of the zygote.
Answer: (iv) A is false, but R is true. The zygote does not attach immediately — it undergoes a series of mitotic divisions while travelling from the oviduct towards the uterus over several days before implanting into the uterine lining, so A is false. Meanwhile, the uterine lining does thicken in preparation before and around the time of ovulation as a normal part of every cycle (whether or not fertilisation actually happens), so it is generally ready to receive a zygote if one arrives — making R true.
Answer: asexual reproduction involves only one parent and relies on mitosis, a type of cell division that produces daughter cells with the exact same number and type of chromosomes as the parent cell. Since there is no combining of genetic material from two different parents (no gamete formation via meiosis, no fertilisation), the offspring inherit an identical copy of the parent's genetic material, making them genetically identical clones.
Answer: menstruation is the shedding of the uterine lining when an egg is not fertilised. During pregnancy, the zygote/embryo implants into the uterine lining, which is now needed to nourish and support the developing foetus throughout pregnancy. Since the lining must be maintained rather than shed, hormonal changes during pregnancy keep it intact instead of breaking it down, and ovulation is also suppressed — so the cycle pauses until after childbirth.
Answer: night-blooming flowers are usually pollinated by nocturnal pollinators (such as moths and bats) that rely more on scent, and on being able to see pale colours in dim light, rather than on bright colour contrast, which works better for daytime pollinators like bees and butterflies. White or pale-coloured petals reflect what little light is available (such as moonlight) more effectively than darker colours, making them easier for night-active pollinators to spot in the dark; many are also strongly fragrant to compensate for colour being a less useful signal at night.
Answer: vegetative propagation produces genetically identical clones of the parent plant. Since all the resulting plants share exactly the same genetic makeup, if the parent (or propagated variety) is susceptible to a particular disease or pest, every single clone shares that same vulnerability — an entire crop of identical plants can be wiped out by the same pathogen. Sexually reproduced plants show genetic variation between individuals, so some may naturally resist a given disease, helping the overall population survive even if others are affected.
Answer: genetic diversity would decrease significantly over generations. Continuous self-pollination means each generation's genetic material comes from a single parent plant's own gametes, repeatedly recombining traits from the same limited genetic source rather than mixing in new genetic material through cross-pollination. Over many generations, this leads to increasingly uniform populations, reduces the plant's ability to adapt to changing conditions or new diseases, and can increase the expression of harmful recessive traits — all of which make the population more vulnerable to being wiped out by unfavourable changes.
Answer: the farmer should use asexual (vegetative) propagation methods such as cutting, grafting, layering, or — especially for large-scale, disease-free, rapid multiplication — tissue culture. These methods rely on mitosis rather than gamete formation and fertilisation, so every new plant is a genetically identical clone of the parent, preserving its desirable characteristics exactly, and they can produce large numbers of new plants quickly without waiting for seed production, germination, or the uncertainties of pollination. Tissue culture in particular (as used in banana farming) can mass-produce healthy, virus-free plantlets efficiently from just the shoot tip of a single plant.
(i) Possible hypotheses: pollen germination rate depends on sugar concentration; and there is likely an optimal sugar concentration at which pollen germinates best (too low a concentration may not provide enough energy or the right osmotic balance, while too high a concentration may draw water out of the pollen grain and inhibit germination).
(ii) Parameters to keep the same: the species/type of pollen used, temperature, incubation time, light conditions, humidity, the volume of solution on each slide, and all other aspects of the experimental setup — only the sugar concentration should be varied, so that any difference observed can be attributed to that one variable alone.
Tomato: since the stamens surround/cover the stigma within the same flower, pollen from the flower's own anthers is very likely to land directly on its own stigma — this points to self-pollination.
Wheat: since the flower opens only after pollination has already occurred, pollination must happen while the flower is still closed — meaning pollen from the flower's own anthers reaches its own stigma inside the closed flower. This is also self-pollination.
Papaya: since male and female flowers are often borne on separate trees, pollen must be carried from a male flower on one plant to a female flower on a different plant — this must be cross-pollination, since self-pollination isn't even possible when one plant doesn't bear both flower types.
(i) Hypothesis: introducing managed bee colonies (compared to relying only on declining natural/wild pollinators) will increase the fruit set percentage and reduce the fruit drop percentage in apple orchards, improving overall fruit yield.
(ii) Parameters: the independent variable is the pollination method (natural pollinators vs. bee colony); the dependent variables are fruit set % and fruit drop %; controlled parameters should include the apple variety, orchard management (irrigation, fertiliser, pruning), climate/location, and number of fruit-bearing branches monitored.
(iii) Comparing the data: Place B (with bee colony) shows a notably higher fruit set (about 40% vs. about 26% at Place A) and a much lower fruit drop (about 8% vs. about 35% at Place A).
(iv) Inference: introducing managed bee colonies significantly improves pollination efficiency — leading to more flowers developing into fruit (higher fruit set) and fewer developing fruits being lost prematurely (lower fruit drop) — most likely because managed bees provide a more reliable and abundant pollinator population than declining wild pollinators, resulting in more complete fertilisation and higher overall apple yield.
Answer: The claim is not entirely correct — it is an oversimplification.
Reason 1: day 14 is only the typical/average timing of ovulation in an idealised 28-day cycle. The menstrual cycle length varies naturally between individuals (and even cycle-to-cycle in the same individual) — the chapter itself states cycles typically range from 21–35 days, not a fixed 28 — so ovulation timing shifts accordingly and cannot be pinned to day 14 for everyone.
Reason 2: ovulation timing can also be affected by factors such as stress, illness, and other individual physiological differences, meaning even within one person, ovulation may not fall on exactly the same day every cycle. So "always on day 14" is only a rough approximation for a standard 28-day cycle, not a universal biological rule.
Answer: the Seed Village Programme (Beej Gram Yojana) is a Government of India initiative that promotes producing and distributing quality seeds of indigenous, locally-adapted crop varieties directly within villages, reducing farmers' dependence on external seed sources.
Why saving indigenous seeds matters:
Uses: IVF (In-Vitro Fertilisation) helps couples facing infertility to conceive by combining an egg and sperm outside the body, in a laboratory dish, and later implanting the resulting fertilised egg into the uterus. It can help when there are blocked fallopian tubes, low sperm count or motility, unexplained infertility, or when other fertility treatments haven't worked. India holds a significant place in IVF history — Subhash Mukhopadhyay of Kolkata pioneered India's first test tube baby (Kanupriya Agarwal, nicknamed "Durga") through experimental IVF work in 1978.
Drawbacks/challenges: IVF can be expensive and is not always successful on the first attempt, often requiring multiple cycles; it involves physically and emotionally demanding hormone treatments for the woman; there is a somewhat increased chance of multiple pregnancies (twins/triplets) if more than one embryo is implanted, carrying additional risks of its own; and access and affordability remain limited in many areas with fewer specialised fertility clinics.
(i)–(ii) Crops by propagation method: crops commonly grown by vegetative propagation include sugarcane (stem cuttings), potato (tubers), banana (tissue culture/suckers), and various fruit trees (grafting); most cereals (wheat, rice, maize), pulses, and many vegetables are conventionally grown from seed.
(iii) Indigenous vs. hybrid seeds: the choice often comes down to a trade-off — hybrid varieties usually give higher, more uniform yield, while indigenous varieties offer resilience, lower cost, and self-sufficiency, since farmers can save and reuse indigenous seed year to year (unlike many hybrids, which don't "breed true" from saved seed). Hybrid varieties are typically developed through controlled cross-breeding (artificial hybridisation) of selected parent varieties.
(iv) Farm animal breeds: indigenous breeds are typically hardier and better adapted to local conditions and diseases (though often lower-yielding), while hybrid/crossbred breeds are bred for higher productivity (e.g., milk yield) but may need more careful management and can be less resistant to local diseases.
(v) Report summary: asexual reproduction (vegetative propagation) is used for many high-value fruit/plantation crops to preserve exact desirable traits quickly, while sexual reproduction (from seed) is used for most staple grain and vegetable crops and to breed new, improved varieties through controlled cross-pollination — the two approaches serve complementary, essential roles across different parts of agriculture.
Pollination strategies: many fruit and vegetable crops (mustard, sunflower, most fruit trees) depend heavily on insect pollinators like bees and butterflies, while cereals (wheat, rice, maize) are largely wind-pollinated and need no insect visitors at all.
Reasons for declining pollinator populations: excessive or indiscriminate pesticide use, loss of natural habitat and wildflower forage due to urbanisation and monoculture farming, climate change affecting flowering times and pollinator activity, and diseases affecting bee colonies.
Possible solutions: reducing or better-timing harmful pesticide use, planting wildflower borders near crops to support pollinators, introducing managed bee colonies (as seen in the apple orchard case study), and raising farmer and community awareness about protecting natural pollinators.
Observing your school garden: record the different types of pollinators (bees, butterflies, moths, flies, beetles, birds) and which specific plants each one visits most — this kind of simple data collection builds a real picture of local pollinator diversity and activity.
Longitudinal section (L.S.): cutting a fruit lengthwise usually shows the seeds arranged along a central axis or attached to the inner wall in a line — this arrangement traces directly back to how the ovules were arranged inside the original ovary (as shown by comparing the tomato flower's ovary structure in Fig. 11.24(c) to the fruit's L.S. in Fig. 11.24(a)).
Transverse section (T.S.): cutting across the fruit typically shows seeds arranged in a ring or in distinct chambers (locules) — for example, a tomato's T.S. shows several seed-containing chambers arranged around the centre, directly reflecting the number of chambers (carpels) originally present in the ovary.
Linking to the ovary: since the fruit develops from the ovary and the seeds develop from the ovules inside it, the number and arrangement of seeds and chambers you observe in a fruit's L.S. and T.S. is essentially a direct "record" of the internal structure of the ovary of the original flower of that same species.
Every living thing must reproduce to continue its kind — asexually through a single parent and mitosis, producing fast, identical clones, or sexually through two parents, meiosis, and the fusion of gametes, producing genetically varied offspring — and from a Bryophyllum leaf sprouting a plantlet to a nine-month human pregnancy, the same underlying biology of gametes, fertilisation, and development connects flowers, animals, and humans alike.
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