Question 1
Paper 4 short-answer style1 markName the part of the female reproductive system where fertilisation takes place. (1 mark)
Model answer
The oviduct (Fallopian tube).
Why this scores
One mark for 'oviduct'.
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Detailed notes on Reproduction for Cambridge IGCSE Biology, covering key concepts, explanations, examples, and exam-focused revision points.
Male + female reproductive systems. Sperm + egg fuse in the oviduct. Fetus develops in the uterus, supported by the placenta.
Mapped to the Cambridge IGCSE 0610 syllabus (2026-2028).
Testes make sperm + hormone. Tube delivers them out via penis.
Parts (and their functions):
| Part | Function |
|---|---|
| Testis (in scrotum) | Produces SPERM and testosterone |
| Scrotum | Sac holding testes outside body (sperm needs cooler temp) |
| Sperm duct (vas deferens) | Carries sperm from testis to urethra |
| Glands (prostate, seminal vesicles) | Produce SEMINAL FLUID (nourishes sperm) |
| Urethra | Tube through penis; carries semen (and urine, separately) |
| Penis | Organ for delivering sperm into vagina |
Sperm cells.
Semen.
Worked qualitative. Why are testes outside the body in the scrotum?
Cambridge tip. Memorise the path of sperm: testis → sperm duct → urethra → penis.
Ovary makes eggs. Oviduct is the route + fertilisation site. Uterus holds the developing baby.
Parts:
| Part | Function |
|---|---|
| Ovary (one each side) | Produces EGGS (ova) and oestrogen + progesterone |
| Oviduct (Fallopian tube) | Carries egg from ovary to uterus; SITE OF FERTILISATION |
| Uterus (womb) | Muscular sac where embryo/fetus develops; lining thickens monthly |
| Cervix | Ring of muscle at base of uterus |
| Vagina | Muscular tube; receives penis; birth canal |
Egg cells (ova).
Worked qualitative. Why is the egg so much bigger than the sperm?
Cambridge tip. Memorise: fertilisation happens in the OVIDUCT, not the uterus.
Sperm meets egg in oviduct. Zygote travels to uterus, implants, develops.
The journey:
Pregnancy facts.
Worked qualitative. Why does it take days from fertilisation to implantation?
Cambridge tip. When tracing the path, name EACH structure: vagina → cervix → uterus → oviduct (sperm); ovary → oviduct (egg); fertilisation; back down to uterus; implantation.
Placenta swaps stuff. Amnion cushions. Bloods stay separate.
The placenta.
What it does.
To fetus:
From fetus:
Crucially: the placenta provides EVERYTHING the fetus needs (mother's blood does the work).
Why bloods kept separate.
Bad things that DO cross.
Amniotic fluid.
Worked qualitative. Why are pregnant women advised to take FOLIC ACID supplements?
Cambridge tip. Always state 'bloods DO NOT MIX'. Cambridge specifically tests this misconception.
Verbatim phrases and definitions Cambridge mark schemes credit.
Human reproduction appears every Paper 4 (8-12 marks: label diagrams, fertilisation, placenta function). Examiner reports flag students saying bloods mix in placenta, fertilisation in uterus, and confusing semen with sperm.
Sources: Cambridge IGCSE Biology 0610 syllabus 2026-2028 (16.4); 0610/42 May/Jun 2024 — Q17 (human reproduction); 0610 Examiner Reports 2022-2024. Last reviewed 2026-05-07.
Step-by-step solutions to past-paper-style questions on sexual reproduction in humans, written exactly the way a tutor would explain them at the board.
Question
Name the parts of the male reproductive system and give the function of each.
Step-by-step solution
Step 1
Testes: produce sperm and the hormone testosterone.
Step 2
Sperm ducts: carry sperm from the testes towards the urethra.
Step 3
Glands (e.g. prostate): add fluid to the sperm to make semen.
Step 4
Urethra (in the penis): carries semen out of the body; the penis delivers the sperm into the vagina.
Answer
Testes (make sperm + testosterone), sperm ducts (carry sperm), glands (add fluid → semen), urethra and penis (deliver semen).
Question
Name the parts of the female reproductive system and give the function of each.
Step-by-step solution
Step 1
Ovaries: produce eggs and the hormones oestrogen and progesterone.
Step 2
Oviducts: carry the egg to the uterus; the site of fertilisation.
Step 3
Uterus: where the embryo develops; its lining thickens to receive the embryo.
Step 4
Cervix and vagina: the cervix is the ring of muscle at the base of the uterus; the vagina receives the penis and is the birth canal.
Answer
Ovaries (make eggs + hormones), oviducts (carry egg / site of fertilisation), uterus (embryo develops), cervix and vagina.
Question
Describe the route taken by the sperm and the egg that leads to fertilisation.
Step-by-step solution
Step 1
Sperm are released into the vagina and swim up through the cervix and uterus into the oviducts.
Step 2
An egg released from an ovary (ovulation) travels into the oviduct.
Step 3
If a sperm meets the egg in the oviduct, the nuclei of the sperm and egg fuse — this is fertilisation — forming a zygote.
Step 4
The zygote divides as it moves to the uterus and implants in the thickened lining, developing into an embryo.
Answer
Sperm swim from the vagina up to the oviduct, where an egg from the ovary has travelled. They fuse there (fertilisation) to form a zygote, which then implants in the uterus.
Examiner tip
Fertilisation happens in the OVIDUCT, not the uterus. The zygote implants in the uterus afterwards.
Question
Explain the function of the placenta during pregnancy.
Step-by-step solution
Step 1
The placenta is an organ that allows exchange of substances between the mother's blood and the fetus's blood, which do not mix.
Step 2
To the fetus: oxygen, glucose and other nutrients pass from the mother's blood.
Step 3
From the fetus: carbon dioxide and urea pass to the mother's blood to be removed.
Step 4
These substances pass between the two blood supplies, which are very close together in the placenta, by diffusion.
Answer
The placenta lets substances be exchanged between the mother's and fetus's blood (without mixing): oxygen and nutrients pass to the fetus, and carbon dioxide and urea pass from it.
Examiner tip
Cambridge marks 'the two bloods do not mix' explicitly. Substances cross by diffusion.
Question
Explain how the sperm cell and the egg cell are each adapted to their functions.
Step-by-step solution
Step 1
The sperm has a tail (flagellum) so it can swim to the egg, and many mitochondria to release the energy for swimming.
Step 2
The tip of the sperm head (the acrosome) contains enzymes that digest the egg's outer layers so the sperm can enter.
Step 3
The egg is large and contains a store of food (in its cytoplasm) to nourish the embryo after fertilisation.
Step 4
After one sperm enters, the egg's membrane changes to stop any other sperm getting in, ensuring the correct chromosome number.
Answer
Sperm: tail to swim, many mitochondria for energy, acrosome enzymes to penetrate the egg. Egg: large with a food store for the embryo, and a membrane that admits only one sperm.
Examiner tip
Each adaptation must be linked to its function. Both gametes are haploid so the zygote has the full chromosome number.
Question
Explain why a pregnant woman who smokes or drinks alcohol can harm her developing baby, even though their bloods do not mix.
Step-by-step solution
Step 1
Although the mother's and fetus's bloods do not mix, small molecules can pass across the placenta between them by diffusion.
Step 2
Harmful substances such as nicotine, carbon monoxide (from smoking) and alcohol are small enough to cross the placenta into the fetus's blood.
Step 3
Carbon monoxide reduces the oxygen the fetus receives, so it grows more slowly (lower birth mass); alcohol can damage the developing organs.
Step 4
So even without the bloods mixing, these substances reach the fetus and can harm its development.
Answer
Small molecules like nicotine, carbon monoxide and alcohol can diffuse across the placenta into the fetus's blood. Carbon monoxide reduces its oxygen supply and alcohol damages development — harming the baby.
Examiner tip
The point is that the placenta exchanges small molecules, so harmful ones (as well as useful ones) can cross.
High-scoring sample answers for sexual reproduction in humans on the Cambridge IGCSE 0610 paper, with examiner-style notes mapping each response to the mark scheme and assessment objectives.
Name the part of the female reproductive system where fertilisation takes place. (1 mark)
Model answer
The oviduct (Fallopian tube).
Why this scores
One mark for 'oviduct'.
State the function of (a) the testes and (b) the ovaries. (2 marks)
Model answer
(a) The testes produce sperm (and the hormone testosterone). (b) The ovaries produce eggs (and hormones such as oestrogen).
Why this scores
One mark each: testes produce sperm; ovaries produce eggs.
Describe how sperm reach the egg after they have been released into the vagina. (3 marks)
Model answer
The sperm swim up through the cervix into the uterus, and then continue swimming up into the oviducts. If an egg is present in an oviduct, the sperm reach it there, and one sperm can fuse with the egg.
Why this scores
Three marks: through the cervix; into the uterus; up into the oviduct (where the egg is).
Explain the functions of the placenta during pregnancy. (4 marks)
Model answer
The placenta allows the exchange of substances between the mother's blood and the fetus's blood, which do not mix. Oxygen and dissolved nutrients such as glucose pass from the mother's blood to the fetus, supplying it for respiration and growth. Waste products such as carbon dioxide and urea pass from the fetus to the mother's blood to be removed. These substances cross the placenta by diffusion between the two closely-placed blood supplies.
Why this scores
Four marks: exchange without the bloods mixing; oxygen/nutrients to the fetus; carbon dioxide/urea from the fetus; by diffusion.
Explain how the developing fetus is supplied with the substances it needs and protected inside the uterus. (5 marks)
Model answer
The fetus is connected to the placenta by the umbilical cord. The placenta allows the exchange of substances between the mother's and the fetus's blood (which do not mix): oxygen and nutrients pass to the fetus, and carbon dioxide and urea pass away from it. The umbilical cord carries the fetus's blood to and from the placenta. The fetus is also surrounded by a membrane containing amniotic fluid, which cushions and protects it from knocks and bumps and supports its weight. Together these allow the fetus to be supplied, to have its waste removed, and to be kept safe as it develops.
Why this scores
Five marks: placenta exchanges substances (O₂/nutrients in, CO₂/urea out, bloods do not mix); umbilical cord carries blood to/from placenta; amniotic fluid cushions and protects the fetus.
Describe what happens from the moment a sperm fuses with an egg to the implantation of the embryo. (6 marks)
Model answer
Fertilisation occurs in the oviduct when the nucleus of a sperm fuses with the nucleus of the egg. Because the sperm and egg are both haploid, the cell formed — the zygote — has the full diploid number of chromosomes. The zygote then divides repeatedly by mitosis to form a ball of cells (an embryo) as it is moved along the oviduct towards the uterus. When the embryo reaches the uterus, it sinks into the thickened lining of the uterus — this is called implantation. Once implanted, the embryo continues to develop, a placenta forms to exchange substances with the mother's blood, and the embryo grows into a fetus. So the sequence is: fertilisation in the oviduct → zygote → division to form an embryo → movement to the uterus → implantation in the uterus lining.
Why this scores
Up to 6 marks: sperm and egg nuclei fuse in the oviduct; haploid gametes → diploid zygote; zygote divides by mitosis to form an embryo; moves to the uterus; implants in the uterus lining; placenta forms / develops further.
Definitions to memorise and the exact keywords mark schemes credit for sexual reproduction in humans answers — sharpened from recent examiner reports for the 2026 0610 sitting.
Male reproductive organs that produce sperm and the hormone testosterone.
Female reproductive organs that produce eggs and the hormones oestrogen and progesterone.
The tube linking the ovary to the uterus. It is the site of fertilisation.
The muscular organ where the embryo and fetus develop. Its lining thickens to receive the embryo.
Organ in the uterus that allows the exchange of substances between the mother's and fetus's blood, without the two bloods mixing.
The cord connecting the fetus to the placenta, carrying the fetus's blood to and from the placenta.
Watery fluid in the membrane (amnion) around the fetus that cushions and protects it.
The traps other students keep falling into on sexual reproduction in humans questions — taken from recent Cambridge IGCSE 0610 examiner reports and mark schemes — and how to avoid them.
Why it happens
They share nutrients.
How to avoid it
The two bloods stay SEPARATE; substances diffuse across the placenta between them. If they mixed, the mother's immune system could attack the baby and disease could spread easily.
Why it happens
The embryo develops there.
How to avoid it
Fertilisation happens in the OVIDUCT. The zygote then travels to the uterus and implants.
Why it happens
Both are involved in male reproduction.
How to avoid it
Sperm are the male gametes (the cells). Semen is the sperm together with the fluid added by the glands.
The things students keep getting wrong in this sub-topic, answered.