Where Mindful Learning Begins
Where Mindful Learning Begins
NCERT Class 9 Science Chapter 11 question answers for Reproduction: How Life Continues (CBSE 2026-27), covering every Think It Over, Activity, Pause & Ponder, Threads of Curiosity, Revise Reflect Refine and Journey Beyond question with full reasoning. Use it with your Class 9 Science Ch 11 notes to check each answer.
Reproduction: How Life Continues covers how new individuals arise, and these Class 9 Science Chapter 11 NCERT solutions explain asexual reproduction (budding, spore formation, cutting, grafting, layering and tissue culture), pollination and fertilisation in flowers, meiosis and variation, the human reproductive system and the menstrual cycle, with full biological reasoning for every question rather than just labelled diagrams.
Last updated 20 October 2026 · Reviewed by Suchita Arora, 13+ years teaching CBSE Maths & Science
Reproduction: How Life Continues explores how every living being produces new individuals of its own kind. It contrasts asexual reproduction — budding, spore formation and vegetative propagation, which involve one parent and produce genetically identical clones — with sexual reproduction, where meiosis and the fusion of gametes from two parents create genetic variation. It follows this idea from flowers (pollination, fertilisation, fruit and seed formation) through reproductive strategies in animals to the human reproductive system, the menstrual cycle, pregnancy and reproductive health. Every question is solved here, section by section, as complete Class 9 Science Chapter 11 NCERT solutions with answers.
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 and tissue culture.
These give offspring that are genetically identical to the parent plant.
So a farmer prefers them when he wants every new plant to have the same good traits (for example, a high-yielding fruit variety such as a grafted rose, banana or sugarcane).
They are also preferred when the crop is propagated from stems or tubers (potato, ginger, sugarcane) and when plants must be multiplied quickly on a large scale.
Sexual methods (growing from seeds): the offspring show variation, because the characters of two parents are mixed.
So a farmer prefers them when he wants new, hardier or disease-resistant varieties (hybrid seeds) and for cereal and pulse crops such as wheat, rice and maize, which are grown from seeds that are easy to store and sow.
Sexual reproduction mixes the characters of two parents, so the offspring show variation.
Variation helps a population to adapt to a changing environment and to survive new diseases. Over many generations it can even give rise to new species.
Complex animals and flowering plants live long, make fewer offspring and face many changes in their surroundings, so this variation is very useful for them.
Yeast and hydra are simple organisms. They can multiply quickly with just one parent, by budding, when conditions are favourable. Asexual reproduction needs no partner, saves energy and increases the population fast.
Sample observations (your own readings from the field may differ):
| Technique | What the gardener does | What is observed |
|---|---|---|
| Cutting | Cuts a shoot piece about 15–20 cm long with 3–4 nodes. Removes the lower leaves and plants half of it in compost-mixed soil at 45–60°. | Roots and new shoots appear from the nodes after watering. A new plant grows. |
| Grafting | Makes a slit in the rooted wild rose (Plant A), fits the stem of the yellow rose (Plant B) into it and wraps it with cloth or film. | After the wound heals, Plant B grows on the roots of Plant A and gives yellow roses. |
| Layering | Buries the middle part of a flexible lemon twig in soil, keeping its tip above the ground. | Roots grow from the buried part in 10–15 days. The twig is then cut off and grows as a new plant. |
In all three methods a part of one parent plant grows into a new plant. No seed or gamete is involved.
Do you observe buds? Yes. Many yeast cells show small, round outgrowths (buds) on the parent cell. Some buds are seen still attached and some have separated.
Do these features indicate that the yeast is duplicating? Yes. The bud grows in size, gets its own nucleus, and separates from the parent cell as a new yeast cell.
How do the observations help? They show that yeast reproduces asexually by budding, with a single parent and no gametes. In warm sugar solution the yeast gets food and warmth, so it multiplies fast and the number of cells increases.
The cotton plug lets air in but keeps dust and other microbes out.
Step 4 (daily observation): Day 1: no change. Day 2: a few white cottony patches appear. Day 3 onwards: the patches spread, and black (or green) dots appear on them.
Step 5: Yes, the mould is seen growing on the surface of the bread.
Step 8 (under the microscope): Yes, long thread-like structures (hyphae) are seen. At the tip of some threads there is a round sac, and inside it many tiny round structures (spores).
Where did the mould come from? From spores already present in the air. They settled on the moist bread, found warmth and moisture, and began to grow and multiply rapidly.
The chamber is kept warm (25–35 °C) because spores need warmth and moisture to grow. At lower temperatures their reproduction slows down or stops, which is why we keep food in a refrigerator.
Spores are light, single-celled and produced in huge numbers. They float in the air and germinate into new moulds when they land on a suitable place.
Steps 2 and 3: picking one bead from each pair, one such combination is ‘light green, light blue, light red’ (blonde, straight hair, brown eyes).
Step 4: each pair gives 2 choices. The choices are independent, so they multiply.
The 8 combinations are:
| No. | Combination of beads | Characters |
|---|---|---|
| 1 | light green, light blue, light red | blonde, straight, brown eyes |
| 2 | light green, light blue, dark red | blonde, straight, black eyes |
| 3 | light green, dark blue, light red | blonde, curly, brown eyes |
| 4 | light green, dark blue, dark red | blonde, curly, black eyes |
| 5 | dark green, light blue, light red | black hair, straight, brown eyes |
| 6 | dark green, light blue, dark red | black hair, straight, black eyes |
| 7 | dark green, dark blue, light red | black hair, curly, brown eyes |
| 8 | dark green, dark blue, dark red | black hair, curly, black eyes |
Step 5: with 23 pairs of chromosomes, each pair gives 2 choices:
This is more than 83 lakh different combinations of characters in the gametes of one person.
This random mixing makes children genetically different from their parents and also from their siblings.
Table 11.1 (sample observations). Flowers: A = pumpkin female flower, B = pumpkin male flower, C = china rose (hibiscus), D = mustard.
| Flower part | A | B | C | D | Other feature(s) | Guess the function |
|---|---|---|---|---|---|---|
| Sepal | Yes | Yes | Yes | Yes | Green, leaf-like, outermost | Protects the flower in the bud stage |
| Petal | Yes | Yes | Yes | Yes | Coloured, often scented | Attracts insects and birds for pollination |
| Stamen | No | Yes | Yes | Yes | Thin filament with an anther at the tip; yellow powder (pollen) on the anther | Male part. Produces pollen grains with male gametes |
| Pistil | Yes | No | Yes | Yes | Stigma (sticky) at the top, a thin style, swollen ovary at the base | Female part. Receives pollen. Ovary contains ovules with egg cells |
Step 5: in the section of the ovary, small round ovules are seen attached inside it. Each ovule has an egg cell.
A complete flower has all four parts: sepals, petals, stamens and pistil. Flower A has no stamen and flower B has no pistil, so they are not complete.
Table 11.2 (observations):
| Treatment | Fruit formation |
|---|---|
| Flower bud (wrapped with muslin cloth bag) | Yes |
| Flower bud with removed stamens (wrapped with muslin cloth bag) | No |
| Flower with removed stamens (wrapped with muslin cloth bag) | Yes |
| Flower (wrapped with muslin cloth bag) | Yes |
| Flower (without muslin cloth bag) | Yes |
In which treatments are the flowers replaced by fruits? In all treatments except the flower bud whose stamens were removed.
Why does that bud give no fruit? Its stamens were removed before the flower opened, and the muslin bag kept out all outside pollen. So no pollen reached its stigma.
Why do the other treatments give fruit? In them, pollen had already reached the stigma (from its own anthers, or from visiting insects in the uncovered flower).
1. Pollen to seed ratio = pollen grains released ÷ seeds formed
Wind-pollinated grasses: smallest ratio uses the least pollen and the most seeds.
Largest ratio uses the most pollen and the fewest seeds.
So wind-pollinated plants use about 2,500 to 20,000 pollen grains for each seed.
Insect-pollinated plants:
and
So insect-pollinated plants use only about 20 to 50 pollen grains for each seed.
| Strategy | Pollen per flower | Seeds per flower | Pollen grains per seed |
|---|---|---|---|
| Wind (maize, wheat) | 5,00,000–10,00,000 | 50–200 | 2,500–20,000 |
| Insects (sunflower) | 20,000–40,000 | 800–1,000 | 20–50 |
Efficiency: insect pollination is much more efficient. It needs far fewer pollen grains per seed and gives more seeds per flower, because an insect carries pollen directly from flower to flower. Wind carries pollen in all directions and most of it is wasted.
2. Why a huge amount of pollen is still effective:
Wind carries the pollen by chance, so only a tiny fraction lands on a stigma of the same kind of plant.
Producing millions of light grains makes sure that enough of them reach the stigmas, so seeds are formed.
Pollen is light and cheap to make, and the flower does not spend energy on petals, nectar or scent to attract insects. Grasses also grow close together, so the pollen cloud often reaches neighbouring flowers.
The pollen tube grows down through the style and reaches the ovary.
It carries the male gamete to the ovule.
The male gamete then fuses with the egg cell present in the ovule.
In the pictures, the madar (calotropis) seeds and the dandelion seeds carry tufts of fine, light hairs.
These hairs act like tiny parachutes. They make the seeds very light and let them float in the air.
So the wind can carry the seeds over long distances.
The two varieties are two different plants of the same species.
The seeds form only when pollen goes from the anther of one variety to the stigma of the other variety.
Transfer of pollen from a flower of one plant to the stigma of a flower of another plant of the same type is cross-pollination.
In external fertilisation (fish, frogs) the eggs and sperm are released into water.
Many eggs are never fertilised, because the sperm may not reach them.
Many of the fertilised eggs are destroyed by water currents or eaten by other animals, so very few young ones survive.
To make up for this loss, these animals produce a very large number of eggs (see Table 11.4: frog 5,000–50,000, fish 100s–1000s).
In internal fertilisation (lizards, birds, mammals) the fertilised egg or embryo is protected inside the female body or in a shelled egg, so more of the young ones survive and fewer eggs are enough (lizard 2–20, bird 1–15).
In internal fertilisation, the sperm and the egg meet inside the body of the female.
The fertilised egg or the embryo is protected inside the mother's body, or inside an egg that has yolk and a shell.
In external fertilisation the gametes are released in water, where they can be washed away or eaten.
A rapid increase in height, broadening of shoulders and cracking of the voice are physical changes seen in boys when their reproductive organs mature.
The testes start producing a hormone that brings about these changes, and sperm production begins.
Given: cycle length = 28 days, last period started on 5 March
To find: date of the next period
Next period = 5 March + 28 days.
March has 31 days, so 5 March + 26 days = 31 March. The remaining 2 days take us to 2 April.
The graph shows one full 28-day cycle. The lining starts shedding again at the end of the cycle, on about day 28, and the next cycle begins.
A sperm cell has 23 chromosomes and an egg cell has 23 chromosomes, because gametes are formed by meiosis, which halves the number.
The zygote is formed by the fusion of one sperm and one egg.
This is the same number as in the cells of the parents.
Sexually transmitted infections (STIs) such as gonorrhoea, herpes, syphilis, genital warts and HIV pass from an infected person to an uninfected person through close physical contact.
A barrier that stops the microbes from passing between the partners protects against them.
Condoms are the protective devices. They also help to prevent pregnancy.
Oral contraceptive pills contain hormones that change the release of eggs, so they help to prevent pregnancy.
They do not form any barrier between the partners.
So the microbes causing STIs (gonorrhoea, herpes, syphilis, genital warts, HIV) can still pass from one partner to the other.
Pills may also have side effects, because they alter the hormones.
Advantages:
1. The long period of care gives the child time to learn language, skills and social behaviour from parents and family.
2. The brain can keep developing and learning after birth.
3. The care and feeding (breast milk) by the mother give strong protection against disease and danger.
4. It builds strong family and social bonds.
Disadvantages:
1. Parents have to spend a lot of time, energy and resources for many years.
2. The baby is helpless against predators, hunger and disease if it is not cared for.
3. A mother can have fewer children, so the population grows slowly.
4. If the parents die or are unable to care, the child's survival is at risk.
Pollen grains will not reach the stigma, so no pollen tube will grow.
The male gamete will not reach the egg in the ovule, so there is no fertilisation and no zygote.
The ovary will not grow into a fruit and the ovules will not become seeds.
The flower will wither and fall off, and no new plant will grow from seeds.
Activity 11.6 showed this: the flower bud with stamens removed and covered with a muslin bag gave no fruit.
In a flower bud, the green sepals form the outermost whorl and cover all the inner parts.
They protect the delicate petals, stamens and pistil in the bud stage from sun, rain, dryness and insects.
When the flower blooms, the sepals remain at the base. They support the petals and the other parts of the flower.
Petals are coloured and often have a fragrance.
These features attract insects, birds and other pollinators to the flower.
When a pollinator visits the flower for nectar, pollen sticks to its body and is carried to the stigma of another flower.
Petals also help to protect the inner parts of the flower.
Some fungi can break down plastic. Aspergillus tubingensis is reported to degrade polyurethane plastic, and Pestalotiopsis microspora has also been reported to do so.
These fungi release enzymes that break the chemical bonds of the plastic. They then use it as food.
Fungi grow fast by spore formation and degrade organic wastes and pollutants, so such fungi may help in managing plastic waste in future.
Every person has two sex chromosomes. Females have XX and males have XY.
The mother has only X chromosomes, so every egg carries an X chromosome.
The father has X and Y, so half of his sperm carry X and half carry Y.
The baby's sex depends on which sperm fuses with the egg:
| Sperm (father) | Egg (mother) | Zygote | Baby |
|---|---|---|---|
| X | X | XX | Girl |
| Y | X | XY | Boy |
So there is an equal chance of a girl or a boy.
When an amoeba divides by binary fission, the parent cell becomes two new cells. No old parent body is left behind, so there is no natural death of old age as in a tree or a human.
Yeast reproduces by budding. The bud is a new cell, but the original (mother) cell remains.
Studies show that a mother yeast cell can produce only a limited number of buds. It slowly gets worn out and finally stops dividing. So the mother cell does age.
The new bud starts afresh. So the line of yeast cells can go on, while a single cell can age.
Scientists are still studying this question, because divisions produce only ‘almost’ identical copies. Damage can pass unequally to the two cells.
Removing the anthers stops the flower from getting pollen from its own stamens, so self-pollination is prevented.
Pollen is then brought from another plant of the same species to its stigma.
Pollen transferred from the anther of one plant to the stigma of another plant of the same kind is cross-pollination.
Tissue culture is a method of asexual reproduction, so (iv) is wrong. Fertilisation takes place after pollination, so the process ensured by dusting the pollen is pollination.
Step 1: (iii) Pollination. The pollen lands on the stigma.
Step 2: (i) Pollen germination on the stigma. The pollen grain produces a pollen tube that grows through the style to the ovule.
Step 3: (ii) Fertilisation. The male gamete fuses with the egg cell.
Step 4: (iv) Formation of the zygote. The fertilised egg is the zygote.
Assertion A: the zygote is formed in the oviduct. It first divides again and again by mitosis while it travels to the uterus, and only then implants in the lining of the uterus. It does not attach immediately. So A is false.
Reason R: the lining of the uterus becomes thick and rich in blood vessels in every cycle, ready to receive a zygote if one arrives. Taking R in this sense, it is true.
(Strictly, the lining is shed during menstruation, so ‘always’ is not exact. Of the four options, (iv) is the only one that matches A being false.)
Asexual reproduction needs only one parent, and no gametes are formed.
The new individual develops by mitosis, a cell division in which each daughter cell receives the same number of chromosomes, identical to those of the parent cell.
There is no mixing of genetic material from a second parent.
So the offspring have the same genetic material as the parent and are called clones.
In the menstrual cycle the lining of the uterus becomes thick and rich in blood vessels to receive a zygote. If no egg is fertilised, the lining is shed as menstruation.
When an egg is fertilised, the zygote divides and implants in the thick lining of the uterus. It takes its nourishment from this lining.
So the lining is not needed to be shed. It stays and supports the growing embryo and foetus for about nine months.
Since pregnancy has begun, the body does not release new eggs each month.
Therefore, there is no menstruation during pregnancy.
Flowers need pollinators, and flowers that bloom at night are visited by night-flying pollinators such as moths and bats.
At night there is very little light. Dark colours cannot be seen in the dark, but white or light colours reflect the little light that is available.
So they stand out clearly and attract the night pollinators. Many of them also have a strong fragrance.
Day-blooming flowers are visible in sunlight, so they can be brightly coloured to attract insects and birds.
Vegetatively propagated plants come from one parent, so they are genetically identical (clones).
They all have the same weaknesses. If one plant is susceptible to a disease, all of them are.
So a disease can spread quickly and may destroy the whole crop.
Sexually reproduced plants have variation. Some of them may be resistant to the disease and survive, so the species continues.
In self-pollination, the pollen comes from the same flower or the same plant, so only one parent plant supplies the genetic material.
The seeds that form will be very similar to the parent. There is little mixing of characters from different plants.
Over several generations the genetic diversity will go down, and the plants will become almost alike.
Such a population cannot adapt well when the environment changes or a new disease appears, because it has no variation to select from.
Cross-pollination avoids this, because it brings together the genes of two different plants.
Suitable methods: vegetative propagation by cutting, grafting, layering, and tissue culture.
Why they are effective:
1. They are asexual methods, so they use only one parent. The new plants are clones and have exactly the same good characters.
2. A new plant grows directly from a part of the parent plant, so there is no need to wait for flowering, pollination and seed formation. It is fast.
3. Many new plants can be made from one parent plant. In tissue culture, thousands of plantlets can be grown from a small piece of tissue such as a shoot tip.
4. Tissue culture also gives healthy, virus-free plants.
The set-up has one changing factor, the sugar concentration. So the hypotheses are about how sugar affects pollen germination:
1. Pollen germination needs sugar, so pollen in 0% sugar will not germinate (or will germinate least).
2. The percentage of germinated pollen increases as the sugar concentration increases, up to a particular concentration.
3. Beyond that best concentration, a more concentrated solution reduces germination.
4. The length of the pollen tube also depends on the sugar concentration.
Only the sugar concentration should change. All these must be the same on every slide:
1. The type (species) and the age of the pollen grains.
2. The amount of pollen put on each slide.
3. The volume of the solution.
4. The temperature and the humidity.
5. The time for which the slides are kept before observing.
6. The method of observation (the same microscope and magnification).
The stamens cover the stigma, so the pollen falls on the stigma of the same flower.
This is the transfer of pollen within the same flower.
The flowers open only after pollination has already taken place.
So the pollen reached the stigma of the same flower before it opened.
Male flowers and female flowers are on different trees.
So the pollen must be carried from a male tree to the female tree by wind or insects.
1. Keeping bee colonies in the orchard will increase the fruit setting of apple, compared with depending on natural pollinators.
2. Pollination by bee colonies will reduce the premature fruit drop.
3. The decline in natural pollinators is one of the reasons for the falling yield, so adding bees will improve the yield.
Changed (independent) factor: the method of pollination, natural pollinators (Place A) or bee colonies (Place B).
Measured (dependent) parameters: fruit setting (number of fruits ÷ total number of fruit-bearing branches) and fruit drop (premature falling of developing fruits), both in per cent.
Parameters to keep the same: variety and age of the apple trees, orchard management (watering, manure, pest control), and the area and number of branches studied.
| Parameter | Place A (natural) | Place B (bee colony) | Difference |
|---|---|---|---|
| Fruit set (%) | 26 | 40 | 14 more at B |
| Fruit drop (%) | 35 | 8 | 27 less at B |
Fruit set: it is higher at Place B.
So fruit set at B is about 54% higher than at A.
Fruit drop: it is much lower at Place B.
So fruit drop at B is about 77% less than at A.
More fruits set and fewer fruits fall, so a higher yield of apples is obtained at Place B.
Pollination by bee colonies increases the fruit setting and decreases the fruit drop, so it increases the apple yield.
Beekeeping also gives honey, so the farmer gets extra income.
A limit of the study is that Places A and B are different locations. Other factors, such as climate and soil, may also play a part. So the experiment should be repeated at more places to be sure.
The claim is not correct. Ovulation is the release of a mature egg from the ovary. It happens around the 14th day only in a typical 28-day cycle.
Reason 1: the length of the cycle is not the same for everyone. It is typically 21–35 days, often around 28 days. In a longer cycle ovulation happens later than day 14, and in a shorter cycle it happens earlier.
Reason 2: the cycle can change in the same person from month to month, because of stress, illness or changes in hormones. So the day of ovulation can shift.
Reason 3: in the first years after puberty (age 10–14) and in the years before menopause (around age 50), cycles are often irregular.
The word ‘always’ makes the claim wrong. The correct statement is that ovulation takes place around the middle of the cycle, about the 14th day in a typical 28-day cycle.
About the programme: under the Seed Village Programme, farmers are helped to grow and store good quality seeds in their own village. This makes quality seed available locally and cheaply, and reduces dependence on outside sources.
Why it is important to save indigenous seeds:
1. Indigenous (local) seeds are adapted to the local soil, climate, water and pests, so they grow well with fewer fertilisers and pesticides.
2. They keep the genetic diversity of crops. This diversity helps crops to survive new diseases, pests and climate change.
3. Farmers can save seeds from their own crop and sow them again, so they do not have to buy seeds every year. Seeds of hybrid varieties do not breed true when saved and resown.
4. Many indigenous varieties have special taste, nutrition and cultural value, and once lost, they cannot be brought back.
5. It protects food security and the farmer's independence.
Report on IVF (In-vitro Fertilisation)
What it is: an egg and a sperm are combined outside the female body, in a laboratory dish. The fertilised egg (embryo) is then placed in the uterus to begin a possible pregnancy. The baby is commonly called a ‘test tube baby’.
History in India: Dr Subhash Mukhopadhyay of Kolkata pioneered India's first test tube baby, Kanupriya Agarwal (nicknamed Durga), in 1978.
Uses:
1. Helps couples who cannot have a baby naturally, for example when the fallopian tubes are blocked.
2. Helps when the sperm count of the male is low or the sperm do not reach the egg.
3. Helps in other cases where fertilisation does not take place inside the body.
Drawbacks:
1. It is costly, and success is not certain. It may need many attempts.
2. The hormone medicines can have side effects, and the process can cause physical and emotional stress.
3. It can lead to twins or more babies at once, which increases health risks.
4. There are ethical and social questions that need discussion in the class.
Sample report (replace with the answers from the farmers you interview):
Sugarcane (stem cuttings), potato, ginger and turmeric (underground stems), banana (suckers or tissue culture), rose and mango (cutting and grafting).
Wheat, rice, maize, mustard, gram, peas, beans, tomato, brinjal and cucumber.
Farmers use hybrid seeds for higher yield, uniform crop and disease resistance. They use indigenous seeds for low cost, good local adaptation, and because they can save the seeds for the next season.
Developing hybrids: the stamens are removed from the flower of one plant, and the flower is covered with a bag to stop self-pollination. Pollen with the desired character, from another plant, is transferred on to its stigma by hand. The seeds formed give the hybrid variety.
| Type | Examples | Features |
|---|---|---|
| Indigenous | Gir, Sahiwal and Tharparkar cows, Murrah buffalo | Hardy, tolerate heat and local diseases, need less feed, give less milk |
| Hybrid (crossbred) | Jersey or Holstein crosses with local cows | Give more milk, but need more feed, care and medical attention |
Asexual methods (cutting, grafting, layering, tissue culture): fast, give plants identical to the parent with the same good traits, and are useful for fruit trees, sugarcane, potato, banana and flowers.
Sexual methods (seeds): give variation, which helps in developing new hybrid and disease-resistant varieties, and seeds are easy to store, transport and sow.
Farmers use both methods according to the need of the crop.
Sample findings (use your own observations):
| Crop | Pollinator | Strategy |
|---|---|---|
| Wheat, rice, maize | Wind | Light pollen in large numbers; long, feathery stigma |
| Sunflower, mustard, pumpkin, cucumber | Bees and other insects | Bright flowers, nectar and scent; sticky or spiny pollen |
| Tomato, pea | Mostly self-pollinated (insects help) | Pollen falls on the stigma of the same flower |
| Hibiscus, coral tree | Birds such as sunbirds, and insects | Large, bright flowers with nectar |
Honey bees, wild bees, butterflies, flies, wasps, birds and wind.
Reasons: heavy use of pesticides, loss of flowering plants and nesting places, growing a single crop over large areas, climate change and diseases of bees.
Solutions: use fewer pesticides, grow flowering plants and a mix of crops, protect hedges and wild areas, keep bee colonies (beekeeping), and spread awareness among farmers.
Pollinator record: note the name or picture of each pollinator, the plant it visits, the time of the day and what it collects (nectar or pollen). Compile the data of the class in a table and discuss how pollination occurs in different plants.
Sample observations (cut the fruits carefully, with the help of an elder):
| Fruit | L.S. and T.S. | Attachment of seeds |
|---|---|---|
| Tomato | Several chambers with jelly-like pulp seen in the T.S. | Seeds attached to the central part (placenta) in each chamber |
| Lady finger (okra) | Five chambers seen in the T.S. | Seeds attached along the inner walls near the centre |
| Brinjal | Many seeds in soft pulp | Seeds attached to the central pulpy part |
| Papaya | One large hollow cavity | Many seeds attached to the inner wall |
| Orange | Many segments around the centre in the T.S. | Seeds attached to the central axis of each segment |
Link with the ovary: a fruit develops from the ovary of the flower, and the seeds develop from the ovules.
In the L.S. and T.S. of a tomato flower, the ovary has the same chambers, and the ovules are attached at the same place as the seeds in the fruit.
So the number of chambers and the attachment of the seeds in the fruit match the structure of the ovary of the same plant.
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.
Seven extra questions in the style of the textbook, for independent practice. Attempt each one on paper first, then tap to check.
A new plant grows from a vegetative part (the bud in the eye of the tuber).
One cell divides into two equal cells.
A bud grows on the parent body, enlarges and separates.
| Basis | Asexual reproduction | Sexual reproduction |
|---|---|---|
| (i) Number of parents | One | Two (usually) |
| (ii) Gametes | Not formed | Male and female gametes are formed (by meiosis) and fuse |
| (iii) Offspring | Genetically identical to the parent (clones) | Show variation. A mix of characters of both parents |
| Examples | Yeast, hydra, bread mould, potato | Flowering plants, fish, birds, humans |
Gametes are formed by meiosis, which halves the number of chromosomes.
Each mitotic division doubles the number of cells, and every cell has the same number of chromosomes as the zygote.
Banana plantation: the plants are clones, so they are genetically identical. If one plant is not resistant to the fungus, none of them is.
The disease will spread from plant to plant and may destroy the whole plantation.
Wheat field grown from seeds: the seeds come from sexual reproduction, so the plants differ a little from each other. Some plants may be resistant, and they will survive and give seeds.
So the loss in the wheat field is likely to be less.
Reducing the risk: grow more than one variety of banana in the plantation, or use tissue culture from healthy shoot tips so that the plantlets are free from infection. Also grow different crops in turns.
Given: cycle length = 35 days, last period began on 10 January (day 1)
10 January + 35 days. January has 31 days.
In a typical cycle, the egg is released about 14 days before the next period starts.
So the egg is released about day 21. Day 1 is 10 January, so day 21 is 30 January.
The length of the cycle is not the same for everyone, but is typically between 21 and 35 days.
Ovulation is on about day 14 only in a 28-day cycle. In Meera's longer cycle, it happens later.
Method: select three groups of female flower buds on pumpkin plants of the same variety and age.
| Set-up | Treatment | Expected result |
|---|---|---|
| 1 | Female flower covered with a muslin bag, so that no insect can reach it | No fruit. No pollen reaches the stigma |
| 2 | Female flower left uncovered, so bees can visit it | Fruit forms. Bees carry pollen from the male flowers |
| 3 | Female flower covered with a bag, pollinated by hand with pollen from a male flower and covered again | Fruit forms. Pollen is supplied without bees |
Things kept the same: variety and age of the plants, water, manure and sunlight, and the size of the muslin bags.
Conclusion: in set-up 1 pollen cannot reach the stigma, because pumpkin has male and female flowers separately, so there is no fruit. Fruit forms in 2 and 3 when pollen reaches the stigma.
So pollination, by bees or by hand, is necessary for fruit formation, and bees are pollinators of pumpkin.
| Function | Part of the flower |
|---|---|
| (i) Produces pollen | Anther (of the stamen) |
| (ii) Receives pollen | Stigma (of the pistil) |
| (iii) Develops into the fruit | Ovary |
| (iv) Develops into the seed | Ovule |
| (v) Contains the egg cell | Ovule (in the ovary) |
| (vi) Protects the bud | Sepals |
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