Wright Effect Genetic drift is a mechanism of evolution in which allele frequencies of a population change over generation due to chance (sampling error). Genetic drift occurs in all population sizes, but its effects are strong in a small population (Fig. . ).
It may result in a loss of some alleles (including beneficial ones) and fixation of other alleles. Genetic drift can have major effects, when the population is reduced in size by natural disaster due to bottle neck effect or when a small group of population splits from the main population to form a new colony due to founder’s effect. 'XHWRFKDQFH HYHQWVRQO\ WKHVHEHHWOHV JLYHVULVHWR RIIVSULQJV )UHTXHQF\RI$ )UHTXHQF\RID )UHTXHQF\RI$ )UHTXHQF\RID 1H[WJHQHUDWLRQ $$ $D $D $D $D DD DD DD DD DD Fig . Genetic drift or more different species.
It is also called adaptive radiation. E.g. Darwin's finches- beak size in relation to seed size inhabiting Galapagos islands. Group selection and sexual selection are other types of selection.
The two major group selections are Altrusim and Kin selection.