In smaller populations why does the effect of genetic drift

In smaller populations, why does the effect of genetic drift increase and the effect of natural selection decrease?

Solution

Genetic drift refers to the change in gene frequency in successive generation of a small population due to chance alone. The effect of genetic drift on a smaller population is large as compared to that on the larger population. This is due to the fact that the larger population produces large number of gamete and therefore, has greater probability to accurately represent the allelic frequency of parental population. On the other hand, the smaller population exhibit lesser diversity of allelic frequencies and therefore, would exhibit the fluctuation in the alleleic frequencies caused by genetic drift from one generation to the next. On the other hand, the natural selection favrors the beneficial alleles over others in the gene pool and hence, its effect is reduced in the smaller populations due to lesser allelic diversity.