Question

What term defines chance changes in allele frequency that have a big effect in small populations?

Answer 1

The bottleneck effect which is extreme genetic drift defines the chance changes in allele frequency that have a big effect on a small population. In the bottleneck effect, there is a drastic decrease in the population of a species due to natural disasters like fire, flood, etc.

Due to this drastic decrease in the population, many beneficial alleles can be lost which causes a decrease in the gene pool. So bottleneck can lead to an increase in homozygosity due to inbreeding which can cause inbreeding depression.

So the bottleneck effect decreases the fitness of the species due to the chance changes in allele frequency that have a big effect in small populations.

Answer 2

Bottleneck is the term used to define chance changes in the frequency of alleles which have a significant effect on small populations. The effect is that the population is greatly reduced because of the change in the allele frequency. A genetic drift will follow which will expedite evolution.