17.3.1—Evolution through gene pool change

Evolution is change in the genetic composition of populations over generations. A gene pool contains all alleles in an interbreeding population; when allele frequencies change, the population evolves.

1. Mutation creates new alleles and meiosis/sexual reproduction create new combinations.
2. Natural selection and genetic drift change allele frequencies from generation to generation.
3. Populations can accumulate different genetic and phenotypic changes, especially when gene flow between them is reduced.
4. If divergence produces reproductive isolation, the populations no longer interbreed successfully and a new species has formed from a pre-existing species.

Individuals can acclimatise during life, but that is not evolution unless inherited allele frequencies change across generations. Evolution has no predetermined goal; species formation is a possible long-term outcome of diverging gene pools, not an immediate result of every frequency change.