State and explain any three factors affe | Class 12 Biology Chapter Evolution, Evolution NCERT Solutions

Three factors that affects allele frequency in the population are following:

1. Genetic drift: Random genetic drift occurs as the result of non- directional fluctuations in the transfer of alleles from one generation to the next in the small population purely by the chance irrespective of selective advantage or disadvantage of the gene. Genetic drift results in the increased variation within a population and an increase in the divergence between populations.   
2. Gene migration or gene flow: It is the movement of alleles from one gene pool to another. There are some different models for the gene flow like Continent-island model (it is one way migration to a separated population), Stepping-stone model (it is a migration where migrants come only from neighbouring populations) and Isolation-by-distance model (it is a gene flow from local neighbourhoods in a continuously distributed populations).
3. Mutation: Mutation is the source of all genetic variations and is considered as random phenomenon; and occurs in all directions. This randomness of mutation was first demonstrated by Luria and Delbruck in 1943.