what is genetic drift? Explain how it provides diviersity in the population. ?

Explanation

The change in the frequency of a gene that occurs merely by chance and not by selection, in small proportion is called genetic drift.
Suppose, for a gene with two alleles, the frequency of a particular allele is 1% (e = 0.01) the probability of losing that allele by chance from small population is more. The end result is either fixation or loss of that allele.
Genetic drift tend to reduce the amount of genetic variation within the population mainly by removing the alleles with low frequencies. It can examplified by Founder and Bottleneck effect.
Founder effect: If a small group of individuals from a population starts a new colony in an isolated region, those individuals are called the founders of the new population. The allelic frequency of their descendants are similar those of the founders rather than to their ancestral parent population.
Eg : `O^(+ve)` blood group is present in nearly 100% of the red Indians. It means the forefathers of the Red Indians tribe were predominantly `O^(+ve)` and they isolated themselves reproductively from other population.