Cambridge IGCSE Biology 0610: Reproduction – Revision Notes

These notes condense topic 16 (Reproduction) of the Cambridge IGCSE Biology 0610 syllabus for examination in 2026, 2027 and 2028, sections 16.1 to 16.6. Core content is tested on Papers 1 and 3 and is needed by everyone; content marked “Extended only” is Supplement, tested on Papers 2 and 4. Section 16.6 has no Supplement content. For full explanations and worked examples, use the Reproduction study guide.

Also useful: Reproduction practice questions, the course hub, the printable checklist, and the free 10-minute Core and Extended diagnostics.

Definitions to learn word for word

• Asexual reproduction: a process resulting in the production of genetically identical offspring from one parent.
• Sexual reproduction: 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: the fusion of the nuclei of gametes.
• Pollination: the transfer of pollen grains from an anther to a stigma.
• Self-pollination (Extended only): transfer from an anther to the stigma of the same flower or a different flower on the same plant.
• Cross-pollination (Extended only): transfer from an anther to the stigma of a flower on a different plant of the same species.
• STI: an infection transmitted through sexual contact.

16.1 and 16.2 – asexual vs sexual (must-know distinction)

	Asexual	Sexual
Parents	One	Usually two
Gametes and fertilisation	None	Yes
Offspring	Genetically identical	Genetically different
Speed	Fast	Slower
Variation	None	Yes

Extended only: gamete nuclei are haploid; the zygote nucleus is diploid.

Extended only – the “discuss” frame. For wild populations, weigh speed and not needing a mate (asexual) against variation and the ability to adapt when the environment changes (sexual). For crops, weigh uniform, predictable plants with the grower’s chosen features (asexual) against the risk that one disease destroys a genetically identical crop, and the chance of new, improved varieties (sexual). A “discuss” answer needs points on both sides.

16.3 – flowers

Male: stamen = anther (makes pollen) + filament (holds anther up). Female: carpel = stigma (receives pollen) + style (holds stigma up) + ovary (contains ovules). Ovules contain the female gamete. Sepals protect the bud. Petals attract insects.

	Insect-pollinated	Wind-pollinated
Petals	Large, bright, scented	Small, dull or absent
Anthers	Inside flower	Hanging outside, long filaments
Stigmas	Inside, sticky	Feathery, hanging outside
Pollen	Larger, sticky or spiky, fewer grains	Smaller, lighter, smooth, huge numbers

Extended only – effects on a population.

	Self-pollination	Cross-pollination
Variation	Less	More
Capacity to respond to environmental change	Lower	Higher
Reliance on pollinators	Lower	Higher

Fertilisation in plants – method in steps

1. Pollen lands on the stigma (pollination).
2. (Extended only) A pollen tube grows from the grain down through the style.
3. (Extended only) The tube enters the ovule through the micropyle.
4. The pollen nucleus fuses with the nucleus in the ovule (fertilisation).

Germination needs: water, oxygen, suitable temperature. Not light. In an investigation, change one condition per tube and compare with a control that has all three.

16.4 – humans

Structure	Function
Testes	Make sperm
Scrotum	Holds testes outside body (cooler)
Sperm ducts	Carry sperm to urethra
Prostate gland	Adds fluid for sperm to swim in
Urethra	Carries semen out through penis
Penis	Places semen in vagina
Ovaries	Make eggs
Oviducts	Carry egg; site of fertilisation
Uterus	Site of implantation; fetus develops here
Cervix	Holds fetus in; widens at birth
Vagina	Receives sperm; birth canal

Gametes compared

	Sperm	Egg cell
Size	Much smaller	Much larger
Structure	Head with acrosome, flagellum, many mitochondria	Large cytoplasm with energy stores, jelly coat
Motility	Swims (motile)	Not motile
Numbers	Very large numbers	Few, usually one per cycle

Adaptations – feature plus job: flagellum → swimming; mitochondria → energy for swimming; acrosome enzymes → digest a way into the egg; energy stores → feed the early embryo; jelly coat changes at fertilisation → only one sperm enters.

Development: zygote → embryo (ball of cells) → implants in uterus lining. Placenta = exchange; umbilical cord = links fetus to placenta; amniotic sac + fluid = protect and cushion.

Extended only: at the placenta, oxygen, glucose, amino acids and other dissolved nutrients pass from mother’s blood to fetal blood; carbon dioxide and urea pass from fetal to mother’s blood. Some pathogens and toxins can cross and affect the fetus.

16.5 – hormones

Puberty: testosterone (testes) → facial and body hair, deeper voice, muscle growth. Oestrogen (ovaries) → breasts develop, hips widen, menstrual cycle starts.

Menstrual cycle (about 28 days): days 1–5 lining lost → lining rebuilds and thickens → egg matures in a follicle in the ovary → ovulation about day 14 → lining kept thick → if no implantation, lining is lost and the cycle repeats.

Must-know distinction – ovary vs uterus in the cycle

Stage	In the ovary	In the uterus lining
Days 1–5	A new follicle starts to develop	Lining breaks down and is lost
Days 6–13	Egg matures inside the follicle	Lining repairs and thickens
About day 14	Ovulation: egg released	Lining thick
Days 15–28	Empty follicle becomes the corpus luteum (Extended detail)	Lining kept thick, ready for implantation

Questions often give a graph of lining thickness against days. Read the day numbers from the axis, and say “lining” or “endometrium” – not “uterus wall breaks down”.

Must-know distinction – the three support structures: the placenta exchanges substances, the umbilical cord carries the fetus’s blood to and from the placenta, and the amniotic fluid inside the amniotic sac protects the fetus from knocks. Do not give the placenta’s job to the fluid, or the other way round.

Extended only – hormone table

Hormone	Source	Key effect
FSH	Pituitary gland	Follicle develops; oestrogen made
Oestrogen	Ovary (follicle); placenta in pregnancy	Lining thickens; inhibits FSH; triggers LH surge
LH	Pituitary gland	Ovulation; corpus luteum forms
Progesterone	Corpus luteum; placenta in pregnancy	Maintains lining; inhibits FSH and LH

Sequence to learn: FSH → oestrogen rises → LH surge → ovulation → progesterone from corpus luteum → no pregnancy → corpus luteum breaks down → progesterone falls → menstruation → FSH rises.

16.6 – STIs (all Core)

• HIV is a pathogen that causes an STI; HIV infection may lead to AIDS.
• Transmission: unprotected sex; sharing needles; infected blood transfusion; mother to baby (placenta, birth, breast milk).
• Control: condoms; fewer partners; testing, treating and informing partners; screening blood; not sharing needles; education.

Quick self-test

1. A dog’s body cells contain 78 chromosomes. How many are in a dog sperm cell, and in a dog zygote? (Extended)
2. Name the part of a flower that receives pollen.
3. Give two ways the anthers of a wind-pollinated flower differ from those of an insect-pollinated flower.
4. State the three conditions a seed needs to germinate.
5. In a germination test, 42 out of 50 seeds germinated. Calculate the percentage germination.
6. Give one structural difference between an egg cell and a sperm cell, other than size.
7. State the function of the scrotum.
8. What happens to the embryo after it forms from the zygote?
9. A woman’s regular 28-day cycle begins on 10 June. On about which date will she ovulate?
10. Name the structure that produces progesterone in the second half of the menstrual cycle. (Extended)
11. Explain why a woman does not ovulate during pregnancy. (Extended)
12. State two ways HIV can be transmitted other than by sexual contact.

Answers

1. Sperm cell 39; zygote 78.
2. The stigma.
3. Any two: they hang outside the flower; they are on long filaments; they are loosely attached so the wind shakes pollen out.
4. Water, oxygen and a suitable temperature.
5. (42 ÷ 50) × 100 = 84 %.
6. Any one: the egg has a jelly coat / energy stores in the cytoplasm; the sperm has a flagellum / acrosome / many mitochondria.
7. Holds the testes outside the body, where it is cooler.
8. It implants into the lining of the uterus.
9. 10 June is day 1, so day 14 is 23 June.
10. The corpus luteum (in the ovary).
11. Progesterone stays high (from the corpus luteum, then the placenta), which inhibits FSH and LH, so no follicle matures and no LH surge triggers ovulation.
12. Any two: sharing needles; transfusion of infected blood; from mother to baby across the placenta, at birth or in breast milk.

Where marks are usually lost

• Writing “fusion of gametes” instead of fusion of the nuclei of gametes.
• Treating pollination and fertilisation as the same event.
• Adding light, or carbon dioxide, to the list of germination conditions.
• Giving a feature of a gamete without saying how it helps (for example “mitochondria” with no mention of energy for swimming).
• Saying the mother’s and fetus’s blood mix in the placenta.
• On an Extended “discuss” question, giving advantages only and no disadvantages.
• Saying FSH or LH is made by the ovary.
• Writing that progesterone “causes” menstruation. It is the fall in progesterone that leads to the lining breaking down.
• Stating a control method for STIs without explaining how it reduces spread.

Next steps

Try the Reproduction practice questions, revisit the study guide for any gaps, and look back at topic 15 with the Drugs revision notes.

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.