Gene flow and genetic drift

Gene flow

The introduction or removal of alleles from a population due to migration or interbreeding

Genetic drift

The change in a population’s allele frequencies due to sudden and random occurrences

Bottleneck effect

Occurs when a large portion of the population is wiped out by a random event or natural disaster, dramatically reducing population size and allele diversity

Founder effect

Occurs when a small, unrepresentative sample of individuals separates from a larger population to colonise a new region and start a new population. The founders population, therefore, has decreased genetic diversity

Negative effect of genetic drift

Interbreeding keeps harmful alleles in gene pool

Adaptive potential is lowered making the species more vulnerable to selection pressures and random occurrences, as the population size is smaller