Explain why a species with a high level of genetic diversity is more likely to survive if a new disease enters its habitat than a species with low genetic diversity.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
1. Genetic diversity means there is variation in alleles within the population.
2. Some individuals may have alleles that make them resistant to the disease.
3. Those resistant individuals survive and reproduce.
4. The surviving resistant genes are passed on, so the population continues.
5. A species with low genetic diversity has little variation, so all individuals are likely equally susceptible and the whole population could die.
2. Some individuals may have alleles that make them resistant to the disease.
3. Those resistant individuals survive and reproduce.
4. The surviving resistant genes are passed on, so the population continues.
5. A species with low genetic diversity has little variation, so all individuals are likely equally susceptible and the whole population could die.
Examiner tips
- Use the exact wording from the mark scheme (e.g., ‘variation in alleles’, ‘resistant to the disease’).
- Show the causal chain: diversity → resistance → survival → reproduction → population persists.
- Keep each point concise and separate with numbers or bullets.
Common mistakes
- Using vague terms like ‘different genes’ instead of ‘variation in alleles’.
- Failing to explain the link between resistance and survival/reproduction.
- Over‑expanding the answer with irrelevant details.
Mark scheme (5 marks)
- Genetic diversity means there is variation in alleles within the population
- Some individuals may have alleles that make them resistant to the disease
- Those resistant individuals survive and reproduce
- So the population continues / the species is not wiped out
- A species with low genetic diversity has little variation in alleles, so all individuals are likely to be equally susceptible and the whole population could die
Key terms in this question
Related
- All AQA A-Level Biology (7402) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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