NCERT Solutions Class 9 Science Ch 11 Reproduction 2026-27

• Asexual (vegetative) methods: preferred when the farmer wants many identical plants quickly and wants to keep a good trait such as high yield or disease resistance.
• Sexual methods (seeds): preferred when the farmer wants variation, to develop new varieties that resist diseases better or suit the environment better.

So asexual reproduction is used for uniformity and fast multiplication, and sexual reproduction for variation and crop improvement.

Complex animals and flowering plants use sexual reproduction because it produces genetic variation. This helps the species adapt to changing conditions and improves the chance of survival. They also have specialised reproductive organs for it.

Simple organisms like yeast and hydra mainly reproduce asexually because it is faster and simpler and needs only one parent. It allows rapid multiplication in stable surroundings where variation is not very important.

Fertilisation. The pollen tube reaches the ovule and the male gamete from the pollen fuses with the female gamete (egg) in the ovule to form a zygote.

Both are adapted for dispersal by wind.

• Madar seeds carry a tuft of fine, silky hairs.
• Dandelion seeds have a light, feathery parachute of hairs.

These hairs make the seeds very light and let the wind carry them over long distances. The seeds then land far from the parent plant, which reduces competition and helps the plant spread to new places.

This is cross-pollination. The pollen is transferred from the flower of one plant to the stigma of a flower on a different plant of the same species.

In external fertilisation, eggs and sperms are released into the surroundings (usually water). The chances of a sperm meeting an egg, and of the young surviving, are low, because many are eaten by predators or destroyed by unfavourable conditions. So a very large number of eggs is needed so that at least some survive to become adults.

In internal fertilisation, fertilisation and early development happen inside the female’s body, which is safe, so fewer eggs are enough.

In internal fertilisation. Fertilisation takes place inside the female’s body, which protects the gametes from predators, temperature changes and drying out.

Ravi is entering puberty (adolescence). It is the stage of life when rapid body changes, such as a growth spurt, broader shoulders and a change in voice, appear as the body becomes capable of reproduction.

1. Days left in MarchFrom 5 March to 31 March = 26 days.
2. Days still to add28 − 26 = 2 days into April

Her next period is most likely on 2 April.

The zygote has 46 chromosomes. It forms when a male gamete and a female gamete fuse, and each gamete brings 23 chromosomes:

Condoms (male or female) are the protective devices. A condom acts as a barrier and prevents direct contact and exchange of body fluids between partners, which reduces the spread of infections such as HIV, gonorrhoea and syphilis.

The risk of sexually transmitted infections (STIs) remains. Oral contraceptive pills only prevent pregnancy, by controlling ovulation. They do not act as a barrier, so body fluids can still be exchanged and infections such as HIV, gonorrhoea and syphilis can still spread.

Correct option: (b) Cross-pollination

Removing the anthers prevents self-pollination. When pollen from a different plant of the same species is placed on the stigma, the pollination is between different plants, which is cross-pollination.

Correct order: (iii) → (i) → (ii) → (iv)

1. Pollination: pollen reaches the stigma.
2. Pollen germination: the pollen tube grows through the style.
3. Fertilisation: the male gamete fuses with the egg.
4. Formation of the zygote.

Correct option: (d)

• A is false: fertilisation happens in the fallopian tube. The zygote divides several times as it travels to the uterus over some days and becomes a blastocyst, which then attaches (implants) to the uterus wall. It does not attach immediately.
• R is true: every month, under the effect of the hormones oestrogen and progesterone, the uterine lining thickens and is supplied with blood and nutrients, ready to receive a fertilised egg.

Asexual reproduction involves only one parent and takes place by mitotic cell division. There is no fusion of gametes and no mixing of genetic material, so the offspring get an exact copy of the parent’s DNA. They are genetically identical (clones).

After fertilisation, the zygote implants in the uterus. The body then releases hormones such as progesterone, which keep the uterine lining (endometrium) in place to nourish the developing embryo. Since the lining is not shed, menstruation does not occur during pregnancy.

Night-blooming flowers must attract pollinators in very low light. White or light-coloured flowers are easier to see in the dark, and they often have a strong fragrance to attract insects such as moths. Day-blooming flowers use bright colours to attract pollinators like bees in sunlight.

Vegetatively propagated plants are genetically identical (clones), so there is no variation among them. If a disease affects one plant, it can affect all the others in the same way.

Sexually reproduced plants show genetic variation, so some of them are likely to be resistant and survive. That is why plants grown by vegetative propagation are more susceptible to diseases.

The genetic diversity would decrease over the generations. In self-pollination, pollen is transferred within the same plant, so there is very little mixing of different genetic material and the offspring stay very similar to the parent. With little variation, the plants would become less able to adapt to changes in the environment and to resist diseases.

The farmer should use asexual (vegetative) propagation, such as cutting, layering, grafting or tissue culture. These methods are effective because they:

• produce genetically identical plants (clones),
• need only one parent,
• multiply plants quickly in a short time, and
• keep the desirable traits without any variation.

(i) Hypotheses:

• Pollen germination depends on the sugar concentration.
• There is an optimum sugar concentration at which germination is maximum.
• Very low or very high sugar concentrations reduce pollen germination.

(ii) Parameters kept the same:

• the kind and age of the pollen grains,
• the temperature and other surrounding conditions,
• the volume of the solution on each slide,
• the time allowed for germination, and
• the method of preparing the slides.

(i) Hypotheses:

• Beekeeping (managed pollinators) increases the efficiency of pollination.
• Better pollination gives a higher fruit set and a lower fruit drop.
• The decline in natural pollinators reduces the apple yield.

(ii) Parameters:

• Independent variable: the type of pollination (natural pollinators or a bee colony).
• Dependent variables: fruit setting and fruit drop.
• Controlled variables: the type of apple trees, soil, climate, irrigation and farming practices (kept the same as far as possible).

(iii) Comparison (reading the graph):

OR (inference): beekeeping improves pollination, which gives better fruit formation and less fruit loss. So managed pollination by a bee colony raises the apple yield considerably.

The claim is not correct.

1. The cycle length varies. It can be about 21 to 35 days, not always 28. Ovulation usually happens about 14 days before the next period, so it is not always on day 14 of the cycle.
2. Individual differences. Stress, illness, diet and hormonal changes can make ovulation earlier or later.

Unicellular organisms do not show ageing in the same way as multicellular organisms. When the parent cell divides, it splits into two new cells, so there is no old individual left behind.

However, ageing can still happen at the level of the cell. In yeast, for example, one cell can keep older cell parts and show signs of ageing after many divisions.