what is genetic dirft??

Genetic drift is the process of change in the gene frequencies of a population due to chance events. It refers to the random fluctuations in the frequency of the appearance of a gene in a small isolated population, presumably owing to chance rather than natural selection.

 

Genetic drift is a random statistical effect and can occur only in small, isolated populations in which the gene pool is small enough that chance events can change its makeup substantially.

The individual changes are most often small or gradual and genetic drift is most often slow. But in the long run it can constitute a large part of the changes in a gene pool. Genetic drift also often cause alleles to disappear completely. The changes due to genetic drift are not driven by environmental or adaptive pressures, and may be beneficial, neutral, or detrimental to reproductive success.