Natural selection and evolution — OCR GCSE Biology
Test yourself on Natural selection and evolution with OCR GCSE practice questions.
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Natural selection and evolution explained
Except for clones and identical twins, biological populations show wide genetic diversity.
Read the full explanation
This wide variation arises fundamentally through spontaneous mutations in DNA, creating new alleles that are continually shuffled through sexual reproduction during meiosis and random fertilisation. High genetic diversity is crucial for population resilience; it ensures that if an environmental disturbance occurs, such as a novel infectious disease or climate shift, some individuals will possess alleles conferring survival advantages.
Your focus
- State that natural populations of a species display extensive genetic variation.
- Explain how spontaneous DNA mutations and sexual reproduction generate population-wide diversity.
- Describe the importance of genetic variation for species survival in fluctuating environments.
Natural selection and evolution exam tips
Marking Points
- State that populations of a species naturally exhibit extensive genetic variation.
- Identify spontaneous gene mutations as the primary origin of all new genetic variants.
- Explain that sexual reproduction reshuffles alleles to create novel combinations within a population.
Examiner Tips
- 💡Always state that variation arises through random mutations before selection pressures occur.
- 💡Link high genetic variation directly to the long-term survival capacity of a population facing disease.
Common Mistakes
- Believing that organisms in a wild population are genetically identical if they look physically similar.
- Assuming that genetic diversity is created in response to environmental demands rather than existing beforehand.