factors that can affect the evolution of species

stabilising selection

• average individuals favoured

• the mean

directional selection

• the individuals favoured in one direction

• e.g longer/shorter fur than usual

genetic drift

• random fluctuations of allele frequencies due to chance events rather than natural selection

generic bottleneck

• large number of population dies so reduced poulation

• alleles are lost

• genetic diversity is reduced as reduced alleles

founder effect

• a small proportion of an original population migrate and reproduce

• new populations alleles consist of founder populations alleles

hardy weinberg principle

• proportion of dominant and recessive alleles.

• calculates allele frequencies

(number of times allele occurs)