Reproduction: How Life Continues Class 9 Notes, Diagrams and Questions

What Reproduction: How Life Continues is about

Weightage: This chapter is part of Unit I, World of Living, which carries 27 of the 80 theory marks in the school annual exam, shared with Cell: The Building Block of Life, Tissues in Action and Patterns in Life: Diversity and Classification.Source: CBSE Science (086) syllabus, Class IX 2026-27, course structure, Unit I World of Living

Key concepts

Reproduction and its two modes

NCERT section 11.1 Asexual Reproduction

Reproduction is the process by which living things produce new individuals of their own kind. It keeps a species going even though each individual has a limited life span (born → grows → matures → reproduces → dies).

	Asexual	Sexual
Parents	one	two (male and female gametes)
Gametes	none	sperm and egg
Cell division	mitosis	meiosis to make gametes
Offspring	genetically identical (clones)	a mix of both parents: variation
Speed	fast; numbers grow quickly in good conditions	slower
Seen in	bacteria, *Amoeba*, yeast, *Hydra*, sponges, many plants	most animals, flowering plants

Small differences from sexual reproduction build up over many generations, helping species adapt to changing environments and sometimes leading to new species.

Worked example

A strawberry plant spreads by runners (side stems that root and form new plants) and also produces seeds. Give one advantage of each method for the plant.

Try it first, then show the solutionSolution

1. Runners are asexual: new plants form quickly, need no pollinator and are copies of a parent already suited to that spot.
2. Seeds come from sexual reproduction: they carry a mix of genes (variation), and they can be carried to new places.
3. Variation means some offspring may survive a new disease or a change in climate.

Answer: Runners: fast, reliable copies of a well-suited parent. Seeds: variation and spread to new places.

Vegetative propagation and its uses

NCERT section 11.1 Asexual Reproduction

Vegetative propagation: new plants grow from vegetative parts (root, stem, leaf), not seeds. One parent → identical offspring.

• Natural: underground stems of potato (eyes) and ginger; stem pieces of money plant and sugarcane (nodes); leaf margins of *Bryophyllum* grow plantlets.

Artificial methods used by gardeners and farmers (Activity 11.1):

• Cutting: a piece of stem with nodes is planted (lower leaves removed, buried about half its length at 45° to 60°) and kept moist: roses, money plant, sugarcane.
• Grafting: a shoot (scion) of a desired variety (yellow or pink rose) is fitted into a slit in a rooted plant (stock, e.g. a hardy wild rose), bound and protected until it heals. Used for mango, roses, citrus.
• Layering: a flexible branch (lemon, jasmine) is bent and its middle buried; roots form in 10 to 15 days, then it is cut free.
• Tissue culture: many plantlets are grown from a few cells of a shoot tip on a nutrient medium in sterile conditions; gives virus-free banana plants and orchids in large numbers. Krishi Vigyan Kendras train farmers in modern grafting.

Advantages: identical plants with desired qualities; quicker fruiting; plants that make few or no seeds (banana, sugarcane) can be grown.
Disadvantage: no variation, so one disease can wipe out a whole crop.

Worked example

A farmer wants 5000 banana plants that are identical, high-yielding and free of virus, in a short time. Which method should he use and why? What is one risk?

Try it first, then show the solutionSolution

1. Tissue culture from shoot-tip (apical meristem) cells gives thousands of plantlets quickly.
2. Shoot-tip cells are usually free of virus, and all plantlets are clones of the chosen plant.
3. Risk: with no genetic variation, a new disease could affect all plants alike.

Answer: Tissue culture; fast, identical, virus-free plants; but no variation, so all are equally at risk from disease.

Budding and spore formation

NCERT section 11.1 Asexual Reproduction

Budding: a small outgrowth (bud) forms by repeated cell division at one spot on the parent, grows, and separates as a new individual.

• Yeast (Activity 11.2): a pinch of yeast in warm sugar solution, seen under a microscope after 1 to 2 hours, shows round buds on parent cells, sometimes in chains.
• *Hydra*: a bud grows on the body wall, develops tentacles and drops off; several buds may grow at once.

Spore formation (Activity 11.3, bread mould): moist bread or roti in a warm (25 to 35 °C), dark, moist box grows fuzzy mould in about 3 days. Under the microscope (with cotton blue stain), *Rhizopus* shows thread-like hyphae with round sacs (sporangia) full of tiny spores; *Aspergillus* bears spores on a swollen tip.

• Spores are tiny, light, usually single-celled and made in huge numbers; they float in air and germinate when they land on a moist, food-rich surface.
• Mould came from spores in the air, not from the bread itself. Louis Pasteur showed that life comes only from pre-existing life.
• Cold slows spore growth, which is why refrigeration keeps food fresh.

Asexual methods rely on mitosis, so offspring are clones. Fungi are also useful: they break down waste and pollutants, and give antibiotics such as penicillin.

Worked example

Two slices of bread are moistened. Slice A is kept in a warm dark box; slice B is kept in a refrigerator. Predict and explain what happens after 3 days. What is the variable tested?

Try it first, then show the solutionSolution

1. Spores from the air settle on both slices.
2. In A, warmth and moisture let spores germinate and form hyphae and sporangia: visible mould.
3. In B, the cold slows or stops germination, so little or no mould appears.
4. Variable tested: temperature (moisture and bread type kept the same).

Answer: Mould grows on A but hardly on B; temperature is the variable.

Meiosis, chromosomes and variation

NCERT section 11.2 Sexual Reproduction

Chromosomes are thread-like structures in the nucleus that carry genetic information. Each species has a fixed number. Humans have 23 pairs (46): one of each pair from each parent.

If gametes carried 46, the number would double every generation. Meiosis prevents this: it halves the number from diploid (46) to haploid (23) in gametes (sperm, egg; in plants, male gametes in pollen and the egg in the ovule). Fertilisation restores 46 in the zygote.

Variation (Activity 11.4, beads): during meiosis the two chromosomes of each pair separate randomly. With 3 pairs there are $2^3=8$ possible combinations; with 23 pairs there are $2^{23}$ (over 8 million) for each parent, before even counting how chromosomes exchange parts. So children differ from parents and from brothers and sisters.

Variation helps species survive changing conditions (for example, some people tolerate low oxygen at high altitude, some digest milk as adults) and, over time, drives evolution.

Worked example

A student uses 4 pairs of beads, each pair standing for two forms of a character. How many different combinations can one 'gamete' carry? How many with the 23 human chromosome pairs?

Try it first, then show the solutionSolution

1. Each pair contributes one of 2 choices, independently.
2. 4 pairs: $2^4=16$ combinations.
3. 23 pairs: $2^{23}=8388608$ combinations.

Answer: 16; over 8.3 million.

The flower and pollination

NCERT section 11.2 Sexual Reproduction

In flowering plants (angiosperms), the flower is the reproductive organ.

Whorl (outside to inside)	Part	Job
1	Sepals (green)	protect the bud
2	Petals (coloured, often scented)	attract pollinators
3	Stamens (male): anther on a filament	anther makes pollen grains containing male gametes
4	Pistil (female): stigma, style, ovary	stigma receives pollen (often sticky); style is a tube to the ovary; ovary has ovules, each with an egg cell

Pollination = transfer of pollen from anther to stigma. Activity 11.6 (pea flowers in muslin bags): fruit forms in all set-ups except the bud whose stamens were removed before opening, so pollen must reach the stigma for fruit to form.

• Self-pollination: to the stigma of the same flower or another flower on the same plant (pea, tomato, wheat).
• Cross-pollination: to a flower on another plant of the same kind (papaya, whose male and female flowers are on different trees); gives more variation.

Agents (pollinators):

Agent	Flower features	Examples
Wind	small, dull; light, dry pollen in huge amounts; long feathery stigma	wheat, maize, rice
Water	pollen carried by currents	*Vallisneria*, *Hydrilla*
Insects	bright, scented, nectar; large sticky or spiny pollen; sticky stigma	sunflower, hibiscus, marigold
Birds	bright, often red	coral tree, hibiscus (sunbirds, Indian white-eye)

Wind-pollinated grasses release 5 to 10 lakh pollen grains per flower for 50 to 200 seeds; insect-pollinated sunflower releases 20 000 to 40 000 for 800 to 1000 seeds.

Worked example

Using the NCERT figures, compare roughly how many pollen grains are needed per seed in wind-pollinated maize (5 lakh pollen, 200 seeds) and insect-pollinated sunflower (20 000 pollen, 1000 seeds). Why can wind pollination still work?

Try it first, then show the solutionSolution

1. Maize: $\frac{500000}{200}=2500$ pollen grains per seed.
2. Sunflower: $\frac{20000}{1000}=20$ pollen grains per seed.
3. Insects carry pollen straight to a flower, so far less is wasted.
4. Wind scatters pollen at random, but producing enormous numbers of light pollen grains makes it likely that some land on the long feathery stigmas.

Answer: About 2500 versus 20 per seed; wind pollination succeeds by sheer numbers.

Fertilisation, seeds, fruits and dispersal

NCERT section 11.2 Sexual Reproduction

After pollination on a compatible stigma:
1. The pollen grain germinates and grows a pollen tube down through the style into the ovary.
2. The male gamete travels down the tube to the ovule.
3. It fuses with the egg cell: fertilisation, forming a zygote.
4. The zygote grows into an embryo.
5. The ovule becomes the seed; the ovary becomes the fruit. Other parts (petals, stamens) usually wither.

Seed dispersal spreads seeds away from the parent by wind (light, winged or hairy seeds: madar/*Calotropis*, dandelion), water (coconut), or animals (hooks, fleshy fruits). With water, air and a suitable temperature, the seed germinates.

Order: pollination → pollen germination on stigma → pollen tube growth → fertilisation → zygote → embryo → seed and fruit.

Plant breeding: selective breeding, artificial hybridisation (remove stamens, bag the flower, dust chosen pollen by hand) and genetic engineering give high-yielding and disease-resistant varieties. P. Maheshwari, 'Father of Indian Embryology', fused egg and male gamete in a test tube and grew plant embryos on artificial media.

Worked example

A plant breeder removes the anthers from a flower before it opens, bags it, and later dusts pollen from another variety on its stigma. Name the process ensured, and explain the purpose of each step.

Try it first, then show the solutionSolution

1. Removing anthers early prevents self-pollination.
2. Bagging keeps out unwanted pollen carried by wind or insects.
3. Dusting chosen pollen ensures cross-pollination with the desired variety; fertilisation then gives seeds with characters of both parents (artificial hybridisation).

Answer: Cross-pollination (artificial hybridisation).

Sexual reproduction in animals

NCERT section 11.3 Sexual Reproduction in Animals

External fertilisation: eggs and sperm are released into water and fuse outside the body (most fish, frogs). Many eggs are lost to currents and predators, so huge numbers are laid.

Internal fertilisation: fusion takes place inside the female's body (reptiles, birds, mammals). Embryos are better protected, so fewer eggs are needed.

Animal	Fertilisation	Eggs at a time	Survival of young
Fish	external	hundreds to thousands	low
Frog	external	5000 to 50 000	low
Lizard	internal	2 to 20	moderate
Bird	internal	1 to 15	moderate to high

Development:

• Fish, amphibians and insects give each egg only a little yolk, enough to make a larva, which feeds and grows, then changes into the adult (metamorphosis): egg → larva → pupa → adult in a butterfly; tadpole → frog.
• Reptile and bird eggs contain enough yolk for the young to hatch.
• In mammals, the embryo develops inside the mother and the young are fed on milk after birth.

The more care the young get, the fewer offspring a species usually produces.

Worked example

Why does a frog lay thousands of eggs while a pigeon lays two?

Try it first, then show the solutionSolution

1. Frog fertilisation is external in water; eggs and tadpoles are unprotected and many are eaten or washed away.
2. Laying thousands makes it likely that a few survive to adulthood.
3. Pigeon fertilisation is internal; eggs have shells and plenty of yolk, and parents incubate and feed the young, so most survive.

Answer: Low survival of unprotected frog eggs is balanced by large numbers; protected, cared-for pigeon eggs need few.

Human reproductive systems, fertilisation and the menstrual cycle

NCERT section 11.5 Reproduction in Human Beings

Male system:

• Testes (in the scrotum, kept slightly cooler than the body, which sperm production needs) make sperm and the male hormone that brings changes at puberty.
• Sperm pass along the vas deferens to the urethra (common passage for urine and sperm). Seminal vesicles and prostate add fluids that nourish sperm and help them move. Each sperm has a head with genetic material and a tail for swimming.

Female system:

• Two ovaries make eggs and female hormones.
• Oviducts (fallopian tubes) carry the egg towards the uterus, a muscular bag where the baby develops; it opens through the cervix into the vagina.

Gametes (formed by meiosis, 23 chromosomes each): sperm are tiny, millions, motile, no stored food; eggs are large, few, non-motile, with stored food.

Fertilisation: an egg released by ovulation meets a sperm in the oviduct; they fuse to form a zygote (46 chromosomes). It divides by mitosis while moving to the uterus and implants in the thick lining: pregnancy begins. (IVF: fertilisation in a lab dish; India's first, in 1978, by Subhash Mukhopadhyay.)

Menstrual cycle (typically 21 to 35 days, often 28; from about age 10 to 14 until menopause around 50):

Days (28-day cycle)	Event
1 to 5	menstruation: lining sheds with some blood
6 to 14	lining rebuilds; an egg matures
about 14	ovulation
15 to 28	lining thick and rich in blood vessels; if no fertilisation, it breaks down and the cycle restarts

The unfertilised egg lives about a day. During pregnancy, menstruation stops because the lining is needed to nourish the embryo.

Sex of the baby: mother always gives X; father gives X (girl, XX) or Y (boy, XY), so the father's sperm decides.

Worked example

Rina's cycle is a regular 28 days and her last period began on 5 March. When is her next period expected, and roughly when did ovulation occur?

Try it first, then show the solutionSolution

1. Next period: 5 March + 28 days = 2 April.
2. Ovulation is around day 14 of the cycle: 5 March is day 1, so day 14 is about 18 March.
3. Cycles vary between people and months, so these are estimates.

Answer: About 2 April; ovulation around 18 March.

Pregnancy, childbirth and reproductive health

NCERT section 11.5 Reproduction in Human Beings

Pregnancy lasts about nine months, in three trimesters:

• 1st: zygote → embryo; major organs begin forming; from about week 9 it is called a foetus.
• 2nd: the foetus grows bigger and stronger; the mother feels movements.
• 3rd: rapid growth; preparation for birth.

Childbirth: strong contractions of the uterus muscles push the baby out through the birth canal; doctors may help by medical or surgical means when needed. After birth: breastfeeding (complete nutrition and protection from disease), warmth, timely vaccines. The mother needs a balanced diet, regular check-ups, rest and family support, and must avoid smoking, alcohol and unprescribed medicines. Post-partum low mood is a treatable condition; ASHA workers help families.

Maturity: adolescent bodies become able to reproduce before emotional maturity (handling feelings, clear communication, thoughtful decisions) develops.

Sexually transmitted infections (STIs): gonorrhoea, syphilis, herpes, genital warts, HIV (which can lead to AIDS); some are not yet curable. Condoms reduce their spread.

Birth control (contraception):

Type	Example	How it works
Barrier	condoms, vaginal covers	stop sperm reaching the egg; condoms also cut STI risk
Hormonal	oral pills	change hormones so eggs are not released; may have side effects
IUD	copper-T	placed in the uterus to prevent pregnancy; may irritate the uterus
Surgical	blocking vas deferens or fallopian tubes	sperm and egg cannot meet

India's CDRI, Lucknow developed a once-a-week non-hormonal pill, free under the National Family Planning Programme. Prenatal sex determination is banned by law in India to stop sex-selective abortion and protect the sex ratio.

Menstrual hygiene: use clean pads (preferably biodegradable), cups or tampons; change pads every 4 to 6 hours; wash with water and wash hands; wrap and bin used pads (never flush); dry reusable pads fully. Menstruation is a normal sign of health.

Worked example

A married couple who do not want a child for a few years ask a health worker which method of contraception also protects against sexually transmitted infections, and which methods can be stopped later. What should the health worker explain?

Try it first, then show the solutionSolution

1. Only barrier methods such as condoms also reduce the spread of STIs, because they stop body fluids passing between partners.
2. Condoms, oral pills (including the once-a-week non-hormonal pill) and the copper-T can be stopped or removed when the couple wants a child.
3. Surgical methods (blocking the vas deferens or fallopian tubes) are meant to be permanent, so they do not suit a couple planning a child later.

Answer: Condoms protect against STIs; condoms, pills and copper-T are reversible; surgical methods are meant to be permanent.

Science in real life: Reproduction: How Life Continues

Each concept, met in an everyday situation. Read the situation, try the problem, then check the solution. The one-line hook is what to remember.

Topics in this chapter

• Asexual Reproduction and Vegetative Propagation
• Flower, Pollination, Fertilisation and Gametes

Reproduction: How Life Continues: formulas and key facts

Asexual vs sexual

Asexual: one parent, mitosis, clones. Sexual: two parents, meiosis for gametes, variation.

Chromosome numbers (humans)

$Bodycell46(23pairs);spermandegg23;zygote23+23=46.$

Gamete combinations

With n chromosome pairs: $2^n$ combinations per parent (3 pairs → 8; 23 pairs → 8 388 608).

Flower parts

1. 1.Sepals
2. 2.petals
3. 3.stamens (anther + filament)
4. 4.pistil (stigma + style + ovary with ovules).

After fertilisation

$Ovule\to seed;ovary\to fruit;zygote\to embryo.$

Plant sequence

1. 1.Pollination
2. 2.pollen germinates
3. 3.pollen tube
4. 4.fertilisation
5. 5.zygote
6. 6.seed and fruit
7. 7.dispersal
8. 8.germination.

Human pathway

1. 1.Ovulation
2. 2.fertilisation in oviduct
3. 3.zygote
4. 4.implantation in uterus
5. 5.embryo
6. 6.foetus (from about week 9)
7. 7.birth at about 9 months.

Menstrual cycle

21 to 35 days (often 28): days 1 to 5 menstruation; about day 14 ovulation; lining thickens after.

Sex determination

Mother X; father X or Y: XX girl, XY boy.

Contraception

Barrier (condom), hormonal (pills), IUD (copper-T), surgical (block vas deferens or fallopian tubes).

Reproduction: How Life Continues: diagrams to practise

Practise each one on paper: draw it from the checklist, then tick off every label.

How the school exam asks Reproduction: How Life Continues

The question patterns to expect, and the method that works for each.

Tricks to remember Reproduction: How Life Continues

Short memory aids. Say each one aloud once, then use it on a question the same day.

• Mi-TWO-sis copies, Meiosis mixes

  Mitosis makes identical copies (asexual); meiosis mixes and halves (gametes).

  Use it when: Linking division to reproduction type.

• Sepals Protect, Petals Pull, Stamens Supply, Pistil Prepares

  Sepals protect, petals pull in pollinators, stamens supply pollen, pistil prepares seeds.

  Use it when: Functions of flower parts.

• OVule → seed, OVary → fruit

  The smaller (ovule) becomes the smaller (seed); the bigger (ovary) becomes the bigger (fruit).

  Use it when: Post-fertilisation changes.

• Many eggs, little care

  External fertilisation: many eggs, little care; internal: few eggs, more care.

  Use it when: Animal reproduction strategies.

• 1-5, 14, 28

  Bleed days 1 to 5, ovulate about day 14, restart around day 28.

  Use it when: Menstrual cycle questions.

Reproduction: How Life Continues: exam-level solved questions

Ordered from exam level to HOTS. Cover the solution, write your own, then compare step by step.

Case-study practice (Section E style)

Read the situation, then answer every part. In a school exam set on the board pattern this is a 4-mark question split into 1 + 1 + 2 marks.

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Where students lose marks in Reproduction: How Life Continues

The slips examiners see most often, and what to write instead.

• ✗Mistake: Saying fertilisation happens in the uterus

  The baby develops there.

  Wrong working

  Sperm meets the egg in the uterus.

  Right working

  Fertilisation usually happens in the oviduct (fallopian tube); the zygote then moves to the uterus and implants.

  ✓Do this: Oviduct = meeting place; uterus = growing place.

  Usually costs: 1 mark.

• ✗Mistake: Confusing pollination with fertilisation

  Both involve pollen.

  Wrong working

  Fertilisation is the transfer of pollen to the stigma.

  Right working

  Pollination is pollen transfer to the stigma; fertilisation is fusion of the male gamete with the egg in the ovule.

  ✓Do this: Pollination = travel; fertilisation = fusion.

  Usually costs: 1 to 2 marks.

• ✗Mistake: Saying the ovary becomes the seed

  Ovary and ovule sound alike.

  Wrong working

  After fertilisation, the ovary becomes the seed and the ovule the fruit.

  Right working

  The ovule becomes the seed; the ovary becomes the fruit.

  ✓Do this: OVule-seed, OVary-fruit.

  Usually costs: 1 mark.

• ✗Mistake: Thinking mould arises from the bread

  It was not visible earlier.

  Wrong working

  Bread turns into fungus when it gets old.

  Right working

  Spores from the air land on moist bread and germinate; life comes from pre-existing life.

  ✓Do this: Always name the spores as the source.

  Usually costs: 1 mark.

• ✗Mistake: Saying birth-control pills prevent STIs

  All contraceptives are lumped together.

  Wrong working

  Pills protect against pregnancy and STIs.

  Right working

  Only barrier methods like condoms reduce STI transmission; pills only prevent egg release.

  ✓Do this: Barrier = blocks contact; hormones = block ovulation.

  Usually costs: 1 to 2 marks.

NCERT exercise guide: Reproduction: How Life Continues

What each exercise in the NCERT chapter tests, how to approach it, and a question of the same kind solved step by step. Questions here are written in our own words.

Practice questions on Reproduction: How Life Continues

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQExam level

   The part of a flower that becomes the fruit is the
   (a) ovule
   (b) ovary
   (c) stigma
   (d) anther

   Hint

   OVary → fruit.

   Answer

   (b) ovary

2. Q2 · 1 mark · MCQExam level

   In humans, the sex of a baby is determined by
   (a) the egg
   (b) the sperm
   (c) the uterus
   (d) the mother's diet

   Hint

   Who can give a Y?

   Answer

   (b) the sperm

3. Q3 · 1 mark · Assertion-reasonExam level

   Assertion (A): Wind-pollinated flowers produce huge amounts of pollen.
   Reason (R): Most wind-carried pollen never reaches a stigma.
   (a) A and R are both true, and R explains A correctly.
   (b) A and R are both true, but R does not explain A.
   (c) A is true, R is false.
   (d) A is false, R is true.

   Hint

   Random travel.

   Answer

   (a)

4. Q4 · 2 marks · Very short answerExam level

   Name the parts of the pistil and state the function of each.

   Hint

   Three parts.

   Answer

   Stigma: receives pollen (often sticky). Style: tube through which the pollen tube grows. Ovary: contains ovules with egg cells; becomes the fruit.

5. Q5 · 2 marks · Very short answerHarder exam level

   Give the steps of layering and name one plant propagated this way.

   Hint

   Bend and bury.

   Answer

   Bend a flexible branch and bury its middle in soil, keeping the tip out; water it; roots form in 10 to 15 days; then cut it from the parent. Example: lemon (also jasmine).

6. Q6 · 3 marks · Short answerHarder exam level

   List the features of insect-pollinated flowers and of wind-pollinated flowers.

   Hint

   Attract versus scatter.

   Answer

   Insect: bright petals, scent, nectar, large sticky or spiny pollen, sticky stigma (sunflower, marigold). Wind: small dull flowers, no scent or nectar, huge amounts of light dry pollen, long feathery stigma (wheat, maize, rice).

7. Q7 · 2 marks · Very short answerHarder exam level

   Compare sperm and egg on size, number, stored food and movement.

   Hint

   Table 11.5.

   Answer

   Sperm: very small, millions, no stored food, actively motile. Egg: large, few (one per month), stored food, non-motile.

8. Q8 · 3 marks · Short answerHarder exam level

   In the pea experiment, which of these bagged set-ups give fruit: (i) a bud (ii) a bud with stamens removed (iii) an open flower with stamens removed (iv) an open flower? Explain.

   Hint

   Pea self-pollinates, often before opening.

   Answer

   (i), (iii) and (iv) give fruit; (ii) does not. Pea flowers self-pollinate, often before opening; in (iii) pollination had already happened before the stamens were removed. In (ii) the stamens were removed before any pollen was shed and the bag kept other pollen out, so no pollination and no fruit.

9. Q9 · 3 marks · Short answerHarder exam level

   Name four methods of contraception and say how each works. Which also reduces STI risk?

   Hint

   Barrier, hormonal, IUD, surgical.

   Answer

   Condom (barrier: stops sperm reaching the egg); oral pill (hormones stop egg release); copper-T IUD (placed in the uterus to prevent pregnancy); surgery (blocking vas deferens or fallopian tubes so sperm and egg cannot meet). Only condoms also reduce STI risk.

10. Q10 · 5 marks · Long answerHarder exam level

    Describe the three trimesters of human pregnancy and two ways to care for the mother's health.

    Hint

    Embryo, foetus, growth.

    Answer

    1st trimester: zygote becomes an embryo; major organs start forming; from about week 9 it is a foetus. 2nd: the foetus grows bigger and stronger; movements are felt. 3rd: rapid growth and preparation for birth. Care: balanced diet rich in protein, vitamins and minerals; regular check-ups; rest and light exercise as advised; avoiding smoking, alcohol and unprescribed medicines; emotional support from family.

11. Q11 · 3 marks · Short answerHOTS / competency

    Human babies stay dependent on adults for years, unlike a calf that walks within hours. Suggest one advantage and one disadvantage of this for the human species.

    Hint

    Brain growth and learning versus risk and cost.

    Answer

    Advantage: the brain keeps developing after birth and the long childhood allows learning of language, skills and culture from adults. Disadvantage: infants are vulnerable for a long time, need much parental time and resources, and fewer children can be raised at once.

12. Q12 · 3 marks · Short answerHOTS / competency

    Prenatal sex determination is banned in India. Using the idea of sex ratio, explain why such a law is needed and why the father, not the mother, decides the baby's sex biologically.

    Hint

    XX and XY.

    Answer

    Where a gender is preferred, sex-selective abortion reduces the number of girls, causing an unequal sex ratio that harms society; the ban protects against this. Biologically, the mother gives only X chromosomes; the father's sperm carries either X or Y, so the sperm that fertilises the egg decides the sex.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.Name two plants that reproduce from underground stems.Show answer

   Potato and ginger.

2. 2.What is grafting?Show answer

   Joining a shoot (scion) of a desired plant to a rooted plant (stock) so they grow as one.

3. 3.Name an organism that reproduces by budding.Show answer

   Yeast or Hydra.

4. 4.Which cell division produces gametes?Show answer

   Meiosis.

5. 5.How many chromosomes are in a human egg?Show answer

   23.

6. 6.Name the male and female parts of a flower.Show answer

   Stamen (male); pistil (female).

7. 7.Define pollination.Show answer

   The transfer of pollen from an anther to a stigma.

8. 8.What does the ovary become after fertilisation?Show answer

   The fruit.

9. 9.Where does fertilisation take place in human females?Show answer

   In the oviduct (fallopian tube).

10. 10.Which contraceptive method also reduces the spread of STIs?Show answer

    Condoms (barrier method).

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐Can you compare asexual and sexual reproduction in a table?
• ☐Can you describe cutting, grafting, layering and tissue culture?
• ☐Can you draw budding in yeast and Hydra and spores in Rhizopus?
• ☐Can you explain why gametes have half the chromosomes?
• ☐Can you label a flower and give each part's function?
• ☐Can you match pollination agents to flower features?
• ☐Can you put the stages from pollination to seed in order?
• ☐Can you compare external and internal fertilisation?
• ☐Can you name the parts of the human systems and their jobs?
• ☐Can you explain the menstrual cycle and three birth-control methods?

Reproduction: How Life Continues: frequently asked questions