Describe the process of natural selection and explain how it may lead to the formation of a new species over many generations.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Variation exists within a population; individuals have different phenotypes and mutations cause random changes in DNA, increasing variation.
Individuals with advantageous characteristics or alleles are better suited to the environment and are more likely to survive and reproduce.
These advantageous alleles are passed down to offspring, so allele frequency increases over many generations.
Over many generations the accumulated changes in inherited characteristics may result in the formation of a new species; the population becomes so different from the original that it can no longer interbreed with it.
Individuals with advantageous characteristics or alleles are better suited to the environment and are more likely to survive and reproduce.
These advantageous alleles are passed down to offspring, so allele frequency increases over many generations.
Over many generations the accumulated changes in inherited characteristics may result in the formation of a new species; the population becomes so different from the original that it can no longer interbreed with it.
Examiner tips
- Use the word ‘variation’ early to show you understand the starting point. Show the cause–effect chain: variation → differential survival → allele frequency change. Mention ‘accumulation over many generations’ to link to speciation. Use the term ‘new species’ or ‘speciation’ when describing the end result.
Common mistakes
- Forgetting to mention that mutations are random and increase variation. Using vague terms like ‘change’ instead of ‘allele frequency’. Failing to state that the new species cannot interbreed with the original population.
Mark scheme (4 marks)
- Variation exists within a population / individuals have different phenotypes / mutations cause random changes in DNA increasing variation
- Individuals with advantageous characteristics / alleles are better suited to the environment and are more likely to survive and reproduce
- Advantageous alleles are passed down to offspring / allele frequency increases over many generations
- Over many generations the accumulated changes in inherited characteristics may result in the formation of a new species / the population becomes so different from the original that it can no longer interbreed with it
Key terms in this question
Related
- All Eduqas GCSE Biology revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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