Cambridge IGCSE Biology 0610: Reproduction – Study Guide

This guide teaches topic 16 (Reproduction) of the Cambridge IGCSE Biology 0610 syllabus for examination in 2026, 2027 and 2028, sections 16.1 to 16.6. Core outcomes are tested on Papers 1 and 3 and are needed by every candidate; Supplement outcomes, labelled “Extended only”, are tested on Papers 2 and 4. Section 16.6 is Core only.

Useful pages for this topic:

• Course hub: Cambridge IGCSE Biology and printable checklist
• Reproduction – Revision Notes for final-weeks recall
• Reproduction – Practice Questions with worked answers
• Free 10-minute diagnostics: Core and Extended

What this topic covers

Section	What you must be able to do	Tier
16.1 Asexual reproduction	Define it; identify examples	Core
	Discuss advantages and disadvantages in the wild and for crops	Extended only
16.2 Sexual reproduction	Define it and fertilisation	Core
	Haploid gametes, diploid zygote; advantages and disadvantages	Extended only
16.3 Sexual reproduction in plants	Flower parts and functions; wind vs insect pollination; pollination; fertilisation; germination conditions	Core
	Self- and cross-pollination and their effects; pollen tube growth	Extended only
16.4 Sexual reproduction in humans	Reproductive systems; gametes; implantation; umbilical cord, placenta, amniotic sac and fluid	Core
	Exchange across the placenta; pathogens and toxins crossing it	Extended only
16.5 Sex hormones in humans	Testosterone and oestrogen at puberty; menstrual cycle	Core
	Sites of oestrogen and progesterone production; FSH, LH, oestrogen and progesterone in control	Extended only
16.6 Sexually transmitted infections	STIs, HIV and AIDS, transmission and control	Core

16.1 Asexual reproduction

Asexual reproduction is a process resulting in the production of genetically identical offspring from one parent. There are no gametes and no fertilisation.

You must identify examples from diagrams or information. Look for one parent and offspring that grow from part of it: bacteria dividing in two, yeast budding, potato tubers, bulbs such as onions, and plantlets on the leaves of some plants.

Extended only – advantages and disadvantages

	In a wild population	In crop production
Advantages	Only one parent needed, so no mate or pollinator required; fast; a well-adapted parent’s features are kept in a stable environment	Every plant has the same desirable features (yield, flavour); quick and reliable
Disadvantages	No variation, so a new disease or environmental change can affect all individuals; offspring close to the parent compete for resources	A single disease can destroy the whole crop; no new varieties arise without sexual reproduction

16.2 Sexual reproduction

Sexual reproduction is a process involving the fusion of the nuclei of two gametes to form a zygote, and the production of offspring that are genetically different from each other. Fertilisation is the fusion of the nuclei of gametes.

Extended only. Gamete nuclei are haploid (one set of chromosomes); the zygote nucleus is diploid (two sets). Sexual reproduction gives variation, so a population can adapt when the environment changes, and crop breeders can combine useful features. The disadvantages are that it is slower, usually needs two parents (and often pollinators), and good combinations of features may not be passed on intact.

Worked example 1 – chromosome numbers (Extended)

A cat’s body cells contain 38 chromosomes. State the number in a cat egg cell and in a cat zygote.

• Body cells are diploid, so haploid = 38 ÷ 2 = 19 in the egg cell.
• The zygote forms when two haploid nuclei fuse: 19 + 19 = 38.

16.3 Sexual reproduction in plants

Parts of an insect-pollinated flower

Part	Function
Sepals	Protect the flower while it is a bud
Petals	Brightly coloured and often scented to attract insects
Stamen (anther + filament)	Male part
Anther	Makes and releases pollen grains
Filament	Holds the anther up
Carpel (stigma + style + ovary)	Female part
Stigma	Receives pollen grains
Style	Holds the stigma up; the pollen tube grows through it
Ovary	Contains and protects the ovules
Ovules	Contain the female gamete; become seeds after fertilisation

You must be able to draw and label these, so practise a clear half-flower drawing with ruled label lines.

Wind-pollinated flowers and pollen

Feature	Insect-pollinated	Wind-pollinated
Petals	Large, coloured, scented	Small, green or absent
Anthers	Inside the flower	Hang outside on long filaments, so wind shakes pollen out
Stigmas	Inside, sticky	Large, feathery, hang outside to catch pollen from the air
Pollen grains	Larger, sticky or spiky to cling to insects, fewer	Smaller, light, smooth, made in very large numbers

Pollination is the transfer of pollen grains from an anther to a stigma. Fertilisation happens when a pollen nucleus fuses with a nucleus in an ovule. Pollination and fertilisation are not the same event.

Extended only. Self-pollination is transfer to the stigma of the same flower or another flower on the same plant. Cross-pollination is transfer to the stigma of a flower on a different plant of the same species. Self-pollination gives less variation, so the population is less able to respond to environmental change, but it relies less on pollinators. Cross-pollination gives more variation and a better capacity to respond to change, but depends on pollinators (or wind) and on other plants being nearby.

After pollination, a pollen tube grows out of the pollen grain, down through the style to the ovary, and enters the ovule through a small gap (the micropyle). The pollen nucleus moves down the tube and fuses with the nucleus in the ovule (Extended only).

Germination

Seeds need water, oxygen and a suitable temperature to germinate. Light is not in the list.

Worked example 2 – a germination investigation

Four tubes each held 20 seeds on cotton wool and were left for five days.

Tube	Conditions	Seeds germinated	Percentage
A	Dry cotton wool, 25 °C	0	0 %
B	Moist cotton wool, air, 25 °C	18	90 %
C	Boiled, cooled water with a layer of oil, 25 °C	0	0 %
D	Moist cotton wool, air, 4 °C	1	5 %

Percentage = (seeds germinated ÷ 20) × 100, so tube B = (18 ÷ 20) × 100 = 90 %. Compare each tube with B, the control: A shows water is needed, C shows oxygen is needed (boiling removes dissolved oxygen and the oil stops more dissolving), and D shows a suitable temperature is needed. Keep the seed type, seed number and time the same in every tube.

16.4 Sexual reproduction in humans

Male part	Function
Testes	Make sperm (and testosterone)
Scrotum	Holds the testes outside the body, where it is cooler
Sperm ducts	Carry sperm from the testes to the urethra
Prostate gland	Adds fluid that sperm swim in
Urethra	Carries semen (and urine) out through the penis
Penis	Becomes erect to place semen in the vagina

For the female system (ovaries, oviducts, uterus, cervix, vagina), learn: ovaries make eggs; oviducts carry the egg and are where fertilisation happens; the uterus is where the fetus develops; the cervix holds the fetus in place and widens at birth; the vagina receives sperm and is the birth canal. The practice questions test these.

Gametes. Fertilisation is the fusion of a sperm nucleus with an egg cell nucleus. Sperm are adapted by a flagellum for swimming, many mitochondria to release energy, and enzymes in the acrosome to digest a way into the egg. The egg has energy stores in its cytoplasm for the early embryo, and a jelly coat that changes at fertilisation so only one sperm enters. Compare them: sperm are much smaller, have a flagellum, are motile and are made in very large numbers; eggs are larger, have no flagellum, are not motile and are released in small numbers (usually one per cycle).

Development. The zygote divides to form an embryo, a ball of cells, which implants in the uterus lining. The placenta is where exchange with the mother’s blood happens; the umbilical cord carries the fetus’s blood to and from it; the amniotic sac holds the amniotic fluid, which cushions and protects the fetus.

Extended only. Oxygen and dissolved nutrients such as glucose and amino acids diffuse from the mother’s blood to the fetus’s blood in the placenta; carbon dioxide and urea diffuse the other way. The two bloods do not mix. Some pathogens (for example the rubella virus and HIV) and toxins (for example nicotine) can still cross the placenta and affect the fetus.

16.5 Sex hormones in humans

At puberty, testosterone (from the testes) causes growth of facial and body hair, a deeper voice, more muscle and growth of the penis and testes, with sperm production starting. Oestrogen (from the ovaries) causes breast development, wider hips, growth of pubic and underarm hair, and the start of the menstrual cycle.

The menstrual cycle (Core). It lasts about 28 days. Days 1–5: the uterus lining breaks down and is lost (menstruation). The lining then thickens again. In the ovary an egg matures inside a follicle and is released at ovulation, around day 14. The lining stays thick in case an embryo implants; if not, it breaks down and the cycle restarts.

Worked example 3 – using cycle days

Menstruation starts on 3 March in a regular 28-day cycle. Estimate the date of ovulation and of the next menstruation. Day 1 is 3 March, so day 14 is 16 March (ovulation) and day 29, the next day 1, is 31 March.

Extended only.

Hormone	Made by	Role
FSH	Pituitary gland	Makes a follicle develop and stimulates oestrogen production
Oestrogen	Ovary (developing follicle)	Repairs and thickens the uterus lining; inhibits FSH; high levels trigger LH release
LH	Pituitary gland	Causes ovulation; the empty follicle becomes the corpus luteum
Progesterone	Corpus luteum in the ovary	Maintains the lining; stops FSH and LH, so no new follicle develops

If there is no pregnancy, the corpus luteum breaks down, progesterone falls, the lining is lost and FSH rises again. In pregnancy, the corpus luteum keeps making progesterone at first, then the placenta makes progesterone and oestrogen, so the lining is kept and no ovulation happens.

16.6 Sexually transmitted infections

A sexually transmitted infection (STI) is an infection transmitted through sexual contact. HIV (human immunodeficiency virus) is a pathogen that causes an STI, and HIV infection may lead to AIDS. HIV is transmitted in body fluids: by unprotected sexual intercourse, by sharing needles, through transfusion of infected blood, and from mother to baby during pregnancy, birth or breastfeeding. The spread of STIs is controlled by using condoms (a barrier to body fluids), having fewer sexual partners, testing and treating infected people and informing their partners, screening donated blood, not sharing needles, and education.

Worked example 4 – an “Explain” answer on STI control

Explain how using condoms and testing people for HIV can reduce the spread of HIV. [3]

• HIV is passed on in body fluids during sexual contact. [1]
• A condom is a barrier, so body fluids are not exchanged during intercourse. [1]
• Testing finds infected people who may not know they have HIV, so they can be treated and their partners told and tested. [1]

Each method needs its own “how”: naming “condoms” and “testing” earns nothing without the reason.

Common errors

• Saying fertilisation is the fusion of gametes rather than of their nuclei.
• Mixing up pollination (transfer of pollen) with fertilisation (fusion of nuclei).
• Calling ovules “eggs” in plants or eggs “ovules” in humans.
• Adding light to the germination conditions.
• Writing that the placenta mixes the two bloods.
• Naming the wrong gland: FSH and LH come from the pituitary, not the ovary.
• Saying antibiotics cure HIV. HIV is a virus (see the Drugs study guide).

Next, use the revision notes and tick off each outcome on the checklist.

Official syllabus

Cambridge IGCSE Biology 0610 syllabus for examination in 2026, 2027 and 2028 (Version 3), Cambridge Assessment International Education, part of Cambridge University Press & Assessment. Topic 16 Reproduction, sections 16.1–16.6.