Explain why variation within a species is beneficial to the survival of that species.

Cambridge International IGCSE Biology (0610) — 18.1 Variation · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

Variation provides the raw material for natural selection, so that individuals with advantageous traits are more likely to survive and reproduce, passing favourable alleles to their offspring. Over many generations the frequency of these beneficial traits rises, making the population better adapted to its environment. A diverse gene pool also reduces the risk of extinction, because a disease or environmental change is less likely to affect all individuals equally.

Examiner tips

Use the word ‘variation’ and link it directly to natural selection; mention survival and reproduction; note the long‑term increase in advantageous traits; include the extinction risk point.
Keep each point short but complete; use exam‑style terminology such as ‘alleles’, ‘frequency’, ‘adapted’.
Show the causal chain: variation → selection → adaptation → reduced extinction risk.

Common mistakes

Failing to mention that variation is the source of natural selection; treating the points as separate rather than a linked argument; using vague terms like ‘differences’ instead of ‘variation’.

Mark scheme (4 marks)

Variation allows natural selection to occur
Individuals with advantageous traits are more likely to survive and reproduce, passing on favourable alleles to offspring
Over many generations the frequency of advantageous traits increases in the population / population becomes better adapted
Variation reduces the risk of extinction from disease / a new disease or environmental change is less likely to kill all individuals

Key terms in this question

variation