Who this is for: Cambridge IGCSE Biology (0610) students who want sexual reproduction — gametes, fertilisation and genetic variation — to become reliable marks instead of a vague contrast with asexual reproduction.
What query it owns: how to understand and revise sexual reproduction in Cambridge IGCSE Biology.
Why this is safe: this page owns the sexual reproduction revision-guide angle, while Tutopiya’s Sexual Reproduction subtopic page owns the learning resource and the free Sexual Reproduction quiz owns the practice.

Sexual reproduction involves the fusion of male and female gametes (fertilisation) to form a zygote that develops into a new organism. Cambridge IGCSE Biology (0610) tests whether you can define gametes and fertilisation, explain why sexual reproduction produces variation, and compare it with asexual reproduction. This guide covers the syllabus definitions, the advantages examiners reward, and the question types that appear every year.

Key takeaways

• Gametes are sex cells (sperm and egg in animals; pollen and egg in plants) that are haploid — they contain half the chromosome number of body cells.
• Fertilisation is the fusion of male and female gamete nuclei to form a diploid zygote.
• Sexual reproduction produces genetic variation because offspring inherit a mix of alleles from two parents.
• Advantages: variation helps populations adapt to changing environments and reduces the impact of disease on all individuals.
• Disadvantages: slower than asexual reproduction; requires finding a mate; fewer offspring per parent.

What is sexual reproduction in Cambridge IGCSE Biology?

Sexual reproduction is the process by which two gametes fuse at fertilisation to produce a zygote that grows into a new individual. Because gametes are produced by meiosis (halving the chromosome number), and each parent contributes different alleles, offspring are genetically different from their parents and from each other. This contrasts with asexual reproduction, where one parent produces genetically identical offspring.

You can read the full explanation, worked examples and notes on Tutopiya’s Sexual Reproduction subtopic page before you attempt questions.

The core ideas you must master

Idea	What it means	How the exam uses it
Gamete	Haploid sex cell	”Define gamete.”
Fertilisation	Fusion of gamete nuclei	”Describe fertilisation.”
Zygote	Diploid cell formed at fertilisation	”State what is formed at fertilisation.”
Variation	Genetic differences between offspring	”Explain an advantage of sexual reproduction.”
Haploid vs diploid	Half vs full chromosome set	”State the chromosome number of gametes.”

Sexual vs asexual reproduction

Feature	Sexual reproduction	Asexual reproduction
Parents	Two (usually)	One
Gametes	Yes — fusion required	No gametes
Genetic variation	Yes — offspring differ	No — offspring are clones
Speed	Slower	Faster
Examples	Humans, flowering plants, fish	Bacteria, hydra, strawberry runners
Advantage	Variation for adaptation	Rapid population increase

Sexual reproduction in past-paper wording: command words that matter

Command word / phrase	What the question wants	Typical sexual reproduction stem
Define	Precise syllabus definition	”Define the term fertilisation.”
State	Short factual answer	”State the function of gametes.”
Explain	Cause and effect	”Explain why sexual reproduction produces variation.”
Compare	Similarities and differences	”Compare sexual and asexual reproduction.”
Suggest	Apply to new context	”Suggest why variation is important in a changing environment.”

Worked exam-style stems (how to answer the wording)

1. “Define the term fertilisation.” Fertilisation is the fusion of the nuclei of a male gamete and a female gamete. Mark-scheme reward: fusion + nuclei + male and female gamete.
2. “Explain one advantage of sexual reproduction.” Sexual reproduction produces genetic variation in offspring, so some individuals may survive if conditions change or a disease affects the population. Reward: variation linked to survival or adaptation.
3. “Compare sexual and asexual reproduction.” Sexual: two parents, gametes fuse, variation in offspring, slower. Asexual: one parent, no gametes, genetically identical offspring, faster. Reward: at least one similarity and two differences.

When you can recognise the wording instantly, work the full set on Tutopiya’s Sexual Reproduction quiz and drill Sexual Reproduction in Plants and Sexual Reproduction in Humans for organism-specific detail.

How sexual reproduction connects to the rest of the syllabus

Sexual reproduction links to Asexual Reproduction (compare tables), Meiosis (gamete formation) and Inheritance (how variation is inherited). The Cambridge IGCSE Biology resource hub links every Reproduction subtopic.

Common mistakes students make

• Defining fertilisation as “sperm meets egg” without mentioning nuclei fusion.
• Saying sexual reproduction produces identical offspring (that is asexual).
• Listing advantages of sexual reproduction without linking to variation or adaptation.
• Confusing gametes (haploid) with body cells (diploid).
• Omitting that gametes are produced by meiosis, not mitosis.

When you need more support

If sexual reproduction questions keep costing marks — especially compare stems with asexual reproduction — work through the Sexual Reproduction quiz and Asexual Reproduction notes, then get focused help from a Cambridge IGCSE Biology tutor.

Frequently asked questions

Is sexual reproduction hard in Cambridge IGCSE Biology? The concepts are straightforward, but marks are lost on incomplete fertilisation definitions and weak compare answers with asexual reproduction.

What is the difference between a gamete and a zygote? A gamete is a haploid sex cell; a zygote is the diploid cell formed when two gamete nuclei fuse at fertilisation.

Why does sexual reproduction produce variation? Each parent contributes different alleles through their gametes, so offspring inherit unique combinations of genes.

How do I revise sexual reproduction effectively? Read the subtopic notes, build the sexual vs asexual compare table from memory, then take the Sexual Reproduction quiz.

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