A coral reef contains coral organisms that can reproduce both sexually and asexually. During a period of stable, warm conditions, the coral reproduces mainly by asexual reproduction. When environmental conditions change dramatically, the coral population that reproduces sexually is more likely to survive. Explain why sexual reproduction increases the chance of survival of the coral population when environmental conditions change dramatically.

Edexcel GCSE Biology (1BI0) — 3.1 Sexual and asexual reproduction · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Coral organisms are capable of both sexual and asexual reproduction. Scientists have observed that coral populations which reproduce sexually tend to survive environmental changes more successfully than those reproducing only asexually.

Model answer (4 marks)

Sexual reproduction involves the fusion of gametes from two parents, producing fertilised eggs that develop into offspring.

Because the gametes come from different individuals, the resulting offspring are genetically varied – they possess a mixture of alleles from both parents.

This genetic variation means that some offspring will carry combinations of genes that are better suited to the new environmental conditions.

Those better‑adapted individuals are more likely to survive and reproduce, allowing the population to persist and reducing the risk of extinction.

Examiner tips

  • Use the word "fusion of gametes" to show understanding of fertilisation.
  • Mention "genetic variation" and "different from parents" to hit the key points.
  • Explain how variation leads to better‑adapted individuals and survival.
  • Keep answer concise – 4‑point answer is enough for full marks.

Common mistakes

  • Confusing asexual reproduction with sexual reproduction – forgetting to mention gamete fusion.
  • Failing to state that offspring are genetically different from parents.
  • Not linking genetic variation to survival in new conditions.

Mark scheme (4 marks)

  1. Sexual reproduction involves the fusion of gametes / fertilisation from two parents
  2. This produces offspring with genetic variation / offspring are genetically different from each other and the parents
  3. Some offspring may have alleles / genotypes that are better suited to the new environmental conditions
  4. These better-adapted individuals survive and reproduce, so the population survives / the species is less likely to become extinct

Key terms in this question

sexual reproduction

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