Class 9 BiologyChapter 11Revise
Revise reproduction
29 flashcards that come back when due, 18 practice questions in exam styles, and one page to print.
Flashcards
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Asexual reproduction in one line?
One parent makes offspring genetically identical to itself, by mitosis.
What is vegetative propagation? Give three examples.
New plants from vegetative parts (root, stem, leaf). Potato and ginger (underground stems), sugarcane or money plant stem, Bryophyllum leaf.
Cutting: three key steps?
Strip the lower leaves, plant about half the length in soil with compost at 45 to 60 degrees, water regularly.
Grafting: what goes where?
A stem piece of Plant B (the variety you want) is fitted into a slit on rooted Plant A, then wrapped until it heals.
Layering: when is the twig cut from the parent?
Only after roots form on the buried part, about 10 to 15 days later.
Tissue culture starts from which tissue, and why do banana farmers like it?
The shoot tip (apical meristem). It gives mass-produced healthy plantlets, free of virus-infected stock, with high yields.
Two organisms that reproduce by budding?
Yeast (Activity 11.2) and hydra.
Why do mould spores spread so well?
Millions are made; they are light, usually single-celled and float on air currents until they find moisture and food.
What is a clone?
An offspring genetically identical to its parent, made by asexual reproduction (mitosis).
What did Louis Pasteur show about new life?
It always comes from pre-existing life, not from non-living matter. This led to the germ theory and to sterilisation.
Why is meiosis needed in sexual reproduction?
It halves the chromosome number in gametes, so fertilisation restores it instead of doubling it each generation.
Diploid and haploid in humans?
Diploid body cells: 46 (23 pairs). Haploid gametes: 23.
How many gamete types from 3 pairs of characters?
8, since 2 × 2 × 2. With n pairs, 2 multiplied by itself n times.
Why is variation important?
It helps some individuals adapt to changing environments; over time it contributes to evolution.
Four whorls of a complete flower, outside in?
Sepals, petals, stamens, pistil.
Parts of a stamen and of a pistil?
Stamen (male): filament and anther. Pistil (female): stigma, style, ovary with ovules.
Pollination: definition and two kinds?
Transfer of pollen from anther to stigma. Self (same flower or same plant) and cross (another plant of the same kind).
Marks of a wind-pollinated flower?
Light, small pollen in large numbers and a long, feathery stigma. Wheat, maize, rice.
Marks of an insect-pollinated flower?
Bright colours, nectar, scent; large sticky or spiny pollen; sticky stigma. Sunflower, hibiscus, marigold.
After fertilisation, what do the ovary and ovule become?
Ovary becomes the fruit; ovule becomes the seed.
Pollen per seed, wind versus insect (Table 11.3)?
Wind: thousands of grains per seed. Insect: only tens of grains per seed.
External versus internal fertilisation?
External: in water, frogs and most fish, many eggs, low survival. Internal: inside the female, reptiles, birds, mammals, fewer eggs, better survival.
Life cycle of a butterfly?
Egg, larva (feeding stage), pupa (body rebuilt), adult.
Path of sperm in the male system?
Testis, vas deferens, urethra. Seminal vesicles and prostate add nourishing fluids.
Parts of the female reproductive system?
Two ovaries, two oviducts (fallopian tubes), uterus, cervix, vagina.
Sperm versus egg (Table 11.5)?
Sperm: very small, millions, no stored nutrients, motile. Egg: large, few, stored nutrients, non-motile.
Typical 28-day cycle in four lines?
Days 1 to 5 menstruation; 6 to 14 lining rebuilds, egg matures; day 14 ovulation; 15 to 28 lining thick, breaks down around day 28 if no fertilisation.
Pregnancy: how long, and embryo or foetus when?
About nine months in three trimesters. Embryo for the first two months; foetus from about the ninth week.
Which contraceptive also reduces the spread of STIs?
The condom. Pills and IUDs prevent pregnancy only.
Practice questions
Questions in the styles CBSE uses: multiple choice, assertion and reason, case based and labelling a diagram. Each answer comes with the reason. Send any question to a friend; the link opens it here and carries nothing about you.
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1Multiple choice Asexual reproduction
Tiny plants grow along the notches of a Bryophyllum leaf and later take root. This is an example of:
New plants arise from a vegetative part, the leaf, with one parent and no seed.
Show the answer
B. New plants arise from a vegetative part, the leaf, with one parent and no seed.
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2Multiple choice Asexual reproduction
A farmer fits a twig of a sweet mango variety into a slit on a hardy, well-rooted mango plant and ties it with film. This method is:
Joining a stem piece of one plant onto a rooted plant so they grow as one is grafting.
Show the answer
C. Joining a stem piece of one plant onto a rooted plant so they grow as one is grafting.
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3Multiple choice Sexual reproduction
In a bead model like Activity 11.4, a gamete gets one bead from each of 5 pairs. How many different gametes are possible?
Each pair gives 2 choices: 2 × 2 × 2 × 2 × 2 = 32.
Show the answer
C. Each pair gives 2 choices: 2 × 2 × 2 × 2 × 2 = 32.
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4Multiple choice Flowering plants
You cut open a ripe pea pod and find peas inside. The pod and the peas developed from:
After fertilisation the ovary becomes the fruit (the pod) and the ovules become the seeds (the peas).
Show the answer
B. After fertilisation the ovary becomes the fruit (the pod) and the ovules become the seeds (the peas).
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5Multiple choice Flowering plants
Pollen of Hydrilla is carried from flower to flower by:
Hydrilla and Vallisneria are aquatic plants pollinated by water.
Show the answer
B. Hydrilla and Vallisneria are aquatic plants pollinated by water.
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6Multiple choice Animals
Which animal releases eggs and sperm into water, so fertilisation happens outside the body?
Frogs and most fish show external fertilisation in water. Lizards, birds and mammals fertilise internally.
Show the answer
C. Frogs and most fish show external fertilisation in water. Lizards, birds and mammals fertilise internally.
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7Multiple choice Human reproduction
What do the seminal vesicles and prostate gland do?
Their fluids nourish the sperm and help them remain active and move. Sperm are made in the testes.
Show the answer
C. Their fluids nourish the sperm and help them remain active and move. Sperm are made in the testes.
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8Multiple choice Human reproduction
Which of these events happens only when the released egg is not fertilised?
Ovulation and the build-up of the lining happen in every cycle, and implantation needs a zygote. With no fertilisation the unused lining is shed: that is menstruation.
Show the answer
B. Ovulation and the build-up of the lining happen in every cycle, and implantation needs a zygote. With no fertilisation the unused lining is shed: that is menstruation.
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9Multiple choice Human reproduction
Which method helps prevent both pregnancy and the spread of sexually transmitted infections?
Condoms act as a barrier, so they stop sperm and also reduce the passing of infections. The others prevent pregnancy only.
Show the answer
C. Condoms act as a barrier, so they stop sperm and also reduce the passing of infections. The others prevent pregnancy only.
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10Assertion and reason Asexual reproduction
Assertion (A) Mould spores can drift far from the colony that made them.
Reason (R) Spores are very light and usually single-celled, so air currents carry them easily.
Both true, and their lightness is exactly why the air can carry them so far. R explains A.
Show the answer
A. Both true, and their lightness is exactly why the air can carry them so far. R explains A.
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11Assertion and reason Flowering plants
Assertion (A) A maize plant sheds pollen in enormous quantities.
Reason (R) Maize relies on bees, drawing them in with bright petals and sweet nectar.
A is true: maize is wind pollinated and makes huge numbers of light pollen grains. R is false: wind-pollinated flowers do not need bright colours or nectar.
Show the answer
C. A is true: maize is wind pollinated and makes huge numbers of light pollen grains. R is false: wind-pollinated flowers do not need bright colours or nectar.
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12Assertion and reason Human reproduction
Assertion (A) A sperm carries 23 chromosomes, though the body cells of the man who made it carry 46.
Reason (R) Gametes are made by meiosis, which halves the number of chromosomes.
Both true: meiosis in the testes takes 46 down to 23 in each sperm. R explains A.
Show the answer
A. Both true: meiosis in the testes takes 46 down to 23 in each sperm. R explains A.
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13Assertion and reason Human reproduction
Assertion (A) A human egg is usually fertilised inside the uterus.
Reason (R) The dividing zygote implants in the inner lining of the uterus.
A is false: fertilisation happens in the oviduct. R is true: implantation is in the uterus lining.
Show the answer
D. A is false: fertilisation happens in the oviduct. R is true: implantation is in the uterus lining.
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14Case based Flowering plants
Saving the best seed
A farmer grows wheat from seed. One year a disease spreads through the field, yet a few plants stay healthy and give heavy ears of grain. She keeps seed only from those plants and sows it the next season. She does the same every year, and after several seasons most of her field stays healthy when the disease returns.
(i) Choosing plants with a wanted character to produce the next generation is called:
Picking the plants that show a desired character and letting only them reproduce is selective breeding.
Show the answer
B. Picking the plants that show a desired character and letting only them reproduce is selective breeding.
(ii) Why were a few plants healthy in the first place, when the others fell ill?
Each seed comes from the fusion of two gametes, so the plants in a field differ a little. Some of them happened to resist the disease.
Show the answer
A. Each seed comes from the fusion of two gametes, so the plants in a field differ a little. Some of them happened to resist the disease.
(iii) If every plant in the field were a clone of a single parent, selection would:
Clones are genetically identical, so there is no variation for the farmer to pick from.
Show the answer
B. Clones are genetically identical, so there is no variation for the farmer to pick from.
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15Case based Animals
Frog spawn in a pond
In the monsoon, Arjun counted a mass of about 5,000 frog eggs at the edge of a pond. Over the next weeks he saw tadpoles swimming and feeding on bits of rotting leaves. By the end of the season he could find only a few young frogs near the pond.
(i) The tadpole stage is best described as:
The tadpole is the larva of the frog: it hatches with little yolk and feeds before changing into the adult.
Show the answer
B. The tadpole is the larva of the frog: it hatches with little yolk and feeds before changing into the adult.
(ii) Where were these eggs fertilised?
Frogs show external fertilisation: the female releases eggs into the water and the male releases sperm over them.
Show the answer
B. Frogs show external fertilisation: the female releases eggs into the water and the male releases sperm over them.
(iii) Compared with a lizard, a frog's young have:
Table 11.4 rates frog survival low and lizard survival moderate.
Show the answer
B. Table 11.4 rates frog survival low and lizard survival moderate.
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16Case based Asexual reproduction
Three slices of bread
Riya placed three similar bread slices in closed boxes for four days: box A was warm with damp tissue, box B was warm and dry, and box C was moist but kept in the fridge. She checked each day without touching the bread.
(i) Which box most likely grew the most mould?
Mould spores need both warmth and moisture; only box A had both.
Show the answer
A. Mould spores need both warmth and moisture; only box A had both.
(ii) Where did the mould come from?
Mould spores float in the air and grow where they find moisture and food.
Show the answer
B. Mould spores float in the air and grow where they find moisture and food.
(iii) Which is the one variable Riya changed between boxes A and C?
A and C were both moist; one was warm, the other cold. Everything else stayed the same, so the test is fair.
Show the answer
B. A and C were both moist; one was warm, the other cold. Everything else stayed the same, so the test is fair.
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17Label the diagram Flowering plants
Label this longitudinal section of a flower.
The pistil runs up the middle: ovary at the base with ovules inside, then style, then stigma at the top. Stamens around it are filaments topped by anthers. Petals are the large coloured whorl; sepals the small green one below.
Show the answer
1: Stigma, 2: Style, 3: Anther, 4: Filament, 5: Petal, 6: Ovary, 7: Ovule, 8: Sepal. The pistil runs up the middle: ovary at the base with ovules inside, then style, then stigma at the top. Stamens around it are filaments topped by anthers. Petals are the large coloured whorl; sepals the small green one below.
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18Label the diagram Human reproduction
Name each numbered part of this female system schematic.
The ovaries sit at the ends of the oviducts, which lead into the uterus. The uterus narrows into the cervix, which opens into the vagina.
Show the answer
1: Ovary, 2: Oviduct, 3: Uterus, 4: Cervix, 5: Vagina. The ovaries sit at the ends of the oviducts, which lead into the uterus. The uterus narrows into the cervix, which opens into the vagina.
Memory aids
Memory aid
Cut, join, bend
Cutting cuts. Grafting joins. Layering bends.
Each name tells you what the gardener does to the plant.
Memory aid
One parent, one copy
Asexual = one parent + mitosis = clone
Sexual = two parents + meiosis + fertilisation = variation.
Memory aid
Di is two, ha is half
46 to 23 and back to 46
Diploid body cells hold pairs; haploid gametes hold half. Fertilisation adds 23 + 23.
Memory aid
Two to the power
3 pairs give 8, 4 give 16, 5 give 32
Each pair doubles the number of possible gametes.
Memory aid
S, P, S, P
Sepals, Petals, Stamens, Pistil
The four whorls from the outside in. The pistil reads top down: stigma, style, ovary.
Memory aid
O to F, O to S
Ovary to Fruit, Ovule to Seed
The bigger word becomes the bigger thing.
Memory aid
Count the plants
One plant: self. Two plants: cross.
Pollen moving between flowers of one plant is still self-pollination.
Memory aid
Eat, change, grow up
Egg, larva, pupa, adult
Larva is the feeding stage, pupa is where the body is rebuilt.
Memory aid
5, 14, 28
Period ends about day 5, ovulation about day 14, cycle about 28 days
For a typical cycle only; real cycles run 21 to 35 days.
One page summary
One page summary
Class 9 Biology, Chapter 11: Reproduction: How Life Continues
Everything in the chapter on one page.
Asexual (11.1, 11.1.1)
- One parent, mitosis, identical offspring (clones).
- Vegetative: potato, ginger, sugarcane, money plant, Bryophyllum.
- Cutting at 45 to 60°, grafting (B on A), layering (roots in 10 to 15 days).
- Tissue culture: shoot tip, healthy banana plantlets.
- Budding: yeast, hydra. Spores: Rhizopus, Aspergillus.
Sexual, variation (11.2, 11.2.1)
- Two parents both give genetic material.
- Meiosis halves chromosomes: 46 to 23 in humans.
- Animals: sperm, eggs. Plants: pollen carries male gametes to ovule.
- 3 bead pairs give 8 gametes (Activity 11.4).
- Variation helps adapt; leads to evolution.
Flowers (11.2.2, 11.2.3)
- Sepals, petals, stamens (filament, anther), pistil (stigma, style, ovary).
- Ovule holds the egg cell.
- Pollination: anther to stigma; needed for fruit (Activity 11.6).
- Self: same flower or plant. Cross: another plant, same kind.
Pollinators, seeds (11.2.4, 11.2.5)
- Wind: light pollen, feathery stigma (wheat, maize, rice).
- Water: Vallisneria, Hydrilla. Insects: sunflower, hibiscus, marigold.
- Birds: coral tree, hibiscus (white-eye, sunbirds).
- Pollen tube, fertilisation, zygote, embryo.
- Ovary to fruit, ovule to seed. Wind needs far more pollen per seed.
Animals (11.3, 11.4)
- External: frogs, most fish; many eggs, low survival.
- Internal: reptiles, birds, mammals; fewer eggs, more protection.
- Little yolk: larva feeds, then changes (butterfly, frog).
- Butterfly: egg, larva, pupa, adult.
- Mammals: young develop inside, fed on milk.
Humans (11.5.1 to 11.5.10)
- Male: testes (scrotum), vas deferens, urethra; seminal vesicles, prostate.
- Female: ovaries, oviducts, uterus, cervix, vagina.
- Fertilisation in oviduct; zygote divides, implants: pregnancy.
- Cycle 21 to 35 days (often 28); ovulation about day 14; period 3 to 7 days.
- Pregnancy about 9 months, 3 trimesters; foetus from about week 9.
- Of the methods, only condoms also help prevent STIs. Prenatal sex determination banned in India.
numford.com. Section numbers follow NCERT Exploration, Grade 9; the wording is our own.