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This lesson covers natural selection and genetic drift — the two main mechanisms that change allele frequencies in populations — as required by the Edexcel A-Level Biology specification (9BI0, Topic 8).
The allele frequency is the proportion of a particular allele in a population's gene pool. For a gene with two alleles (A and a):
Changes in allele frequency over time are the basis of evolution.
Natural selection is the process by which organisms with heritable traits that give them a survival or reproductive advantage in a particular environment are more likely to pass those alleles to the next generation. Over time, this changes allele frequencies in the population.
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