← Evolutionary processes leading to speciation

3 Variation & the gene pool

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Sources of genetic variation

• Mutation, the ultimate source of all new alleles.
• Sexual reproduction, crossing over, independent assortment, and random fertilisation shuffle alleles into new combinations.
• Gene flow, new alleles arriving via migration/interbreeding.

A gene pool is all the alleles in a population. Evolution is a change in allele frequencies in the gene pool over generations. Variation is essential, without it, natural selection has nothing to act on.

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