changes to allele frequency within gene pool

mutations

introduces new alleles into populations gene pool (can be advantageous/dis, or have no effect). Beneficial mutations become more common as they enhance survival, thus allele freq changes

random genetic drift

random non directional change in allele frequency between generations

founders effect (extreme example + type of genetic bottleneck)

occurs when small group moves away from its homeland to totally new area and establishes new breeding population which later expands.

bottleneck effect

sudden decrease in the size of a population resulting in reduction of genetic variation. this can be caused by random events (natural/human related disasters; war, habitat destruction)

random sampling/fertilisation

causes genetic variation within population by ensuring any possible combination of gametes have equal chance of occurring. this is completely random, thus frequencies of combinations in offspring can deviate over time → change in allele frequency

inbreeding

creates above average incidence of inherited illnesses