16.4

Sexual reproduction in humans

Cambridge IGCSE Biology (0610)  · Unit 16: Reproduction  · 12 flashcards

Sexual reproduction in humans is topic 16.4 in the Cambridge IGCSE Biology (0610) syllabus , positioned in Unit 16 — Reproduction , alongside Asexual reproduction, Sexual reproduction and Sexual reproduction in plants.  In one line: Fertilization is the fusion of a sperm nucleus (male gamete) with an egg cell nucleus (female gamete). This fusion creates a zygote, the first cell of the new organism containing a full set of chromosomes.

This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical). Past papers from 2022 to 2025 show this topic across 16 questions worth 185 marks (around 2.7% of all Biology marks in those years).

The deck below contains 12 flashcards — 1 definition, 5 key concepts, 1 process card and 5 identification cards — covering the precise wording mark schemes reward.  Use the definition card to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.

Key definition

Describe fertilization in humans

Fertilization is the fusion of a sperm nucleus (male gamete) with an egg cell nucleus (female gamete). This fusion creates a zygote, the first cell of the new organism containing a full set of chromosomes.

What the Cambridge 0610 syllabus says

Official 2026-2028 spec

These are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.

  1. Identify Identify on diagrams and state the functions of the following parts of the male reproductive system: testes, scrotum, sperm ducts, prostate gland, urethra and penis
  2. Identify Identify on diagrams and state the functions of the following parts of the female reproductive system: ovaries, oviducts, uterus, cervix and vagina
  3. Describe Describe fertilisation as the fusion of the nuclei from a male gamete (sperm) and a female gamete (egg cell)
  4. Explain Explain the adaptive features of sperm, limited to: flagellum, mitochondria and enzymes in the acrosome
  5. Explain Explain the adaptive features of egg cells, limited to: energy stores and the jelly coat that changes at fertilisation
  6. Compare Compare male and female gametes in terms of: size, structure, motility and numbers
  7. State State that in early development, the zygote forms an embryo which is a ball of cells that implants into the lining of the uterus
  8. Identify Identify on diagrams and state the functions of the following in the development of the fetus: umbilical cord, placenta, amniotic sac and amniotic fluid
  9. Describe Describe the function of the placenta and umbilical cord in relation to the exchange of dissolved nutrients, gases and excretory products between the blood of the mother and the blood of the fetus Supplement
  10. State State that some pathogens and toxins can pass across the placenta and affect the fetus Supplement
Key Concept Flip

What are the main parts of the male reproductive system and their functions?

Answer Flip

The male reproductive system includes: Testes (produce sperm and testosterone), Scrotum (holds testes at optimal temperature), Sperm ducts (transport sperm), Prostate gland (secretes fluid for semen), Urethra (carries semen and urine), and Penis (delivers sperm).

Key Concept Flip

What are the main parts of the female reproductive system and their functions?

Answer Flip

The female reproductive system includes: Ovaries (produce egg cells and estrogen/progesterone), Oviducts (transport egg cells to uterus, site of fertilization), Uterus (where the embryo implants and develops), Cervix (lower part of uterus, opens to vagina), and Vagina (receives sperm).

Definition Flip

Describe fertilization in humans.

Answer Flip

Fertilization is the fusion of a sperm nucleus (male gamete) with an egg cell nucleus (female gamete). This fusion creates a zygote, the first cell of the new organism containing a full set of chromosomes.

Key Concept Flip

What are the adaptive features of a sperm cell?

Answer Flip

Sperm cells have: a Flagellum (tail) for motility, numerous Mitochondria to provide energy for swimming, and Enzymes in the acrosome to break down the egg's outer layers, allowing penetration for fertilization.

Key Concept Flip

What are the adaptive features of an egg cell?

Answer Flip

Egg cells contain Energy stores (nutrients) to nourish the developing embryo after fertilization, and a Jelly coat which changes its structure after fertilization to prevent more than one sperm from entering.

Key Concept Flip

Compare the sizes of male and female gametes.

Answer Flip

Egg cells are significantly larger than sperm cells. The large size of the egg cell is due to its large cytoplasm that contains energy stores for the developing embryo, whereas sperm cells are small and streamlined for motility.

Key Concept Flip

How does a zygote develop after fertilization?

Answer Flip

After fertilization, the zygote undergoes rapid cell division to form an embryo, a ball of cells. The embryo implants into the lining of the uterus where it continues to develop.

Key Concept Flip

What are the functions of the umbilical cord?

Answer Flip

The umbilical cord connects the fetus to the placenta. It contains blood vessels that transport oxygen, nutrients, and antibodies from the mother's blood to the fetus, and removes carbon dioxide and other waste products from the fetus's blood.

Key Concept Flip

What are the functions of the placenta?

Answer Flip

The placenta facilitates the exchange of dissolved nutrients, gases (oxygen and carbon dioxide), and excretory products between the mother's blood and the fetus's blood. It also produces hormones to maintain the pregnancy.

Key Concept Flip

What are the functions of amniotic sac and amniotic fluid?

Answer Flip

The amniotic sac is a membrane filled with amniotic fluid that surrounds and protects the fetus. The amniotic fluid cushions the fetus against impacts and allows it to move freely, aiding muscle and bone development.

Key Concept Flip

Can pathogens or toxins cross the placenta?

Answer Flip

Yes, some pathogens (

Example: viruses causing rubella or HIV) and toxins (. alcohol, nicotine) can cross the placenta from the mother's blood to the fetus's blood. This can cause serious birth defects or developmental problems.
Key Concept Flip

Compare motility of male and female gametes.

Answer Flip

Sperm cells are motile, meaning they can move independently using their flagella. Egg cells are non-motile; they do not have the ability to move themselves and rely on the oviduct to transport them.

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16.3 Sexual reproduction in plants 16.5 Sex hormones in humans

Key Questions: Sexual reproduction in humans

Describe fertilization in humans.

Fertilization is the fusion of a sperm nucleus (male gamete) with an egg cell nucleus (female gamete). This fusion creates a zygote, the first cell of the new organism containing a full set of chromosomes.

Tips to avoid common mistakes in Sexual reproduction in humans

More topics in Unit 16 — Reproduction

Sexual reproduction in humans sits alongside these Biology decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.

Cambridge syllabus keywords to use in your answers

These are the official Cambridge 0610 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.

testis ovary sperm egg ovum penis vagina uterus oviduct fallopian tube menstrual cycle menstruation ovulation fertilisation implantation embryo fetus placenta umbilical cord amniotic fluid gestation birth puberty secondary sexual characteristics contraception

Key terms covered in this Sexual reproduction in humans deck

Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.

Describe fertilization in humans

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