A level Biology B · Edexcel 9BI0 · Topic 3B
Natural selection and adaptation
Key points
- Individuals in a population show variation, partly caused by different alleles produced by mutation.
- Populations produce more offspring than can survive, so there is competition and selection pressure (e.g. predators, disease, climate).
- Individuals with advantageous alleles are more likely to survive and reproduce, passing those alleles on.
- Over many generations the allele frequency of advantageous alleles increases: this is natural selection.
- Adaptations may be anatomical (body structure, e.g. thick fur), physiological (body processes, e.g. hibernation) or behavioural (e.g. migration).
- Examples include antibiotic resistance in bacteria and insecticide resistance in insects.
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Natural selection is the process that changes the genetic make-up of populations and produces adaptations. Given enough time and isolation, the same process can split one species into two.
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