Biology 30 Populations Practice Test 2026 - Free Biology Practice Questions and Study Guide

Natural selection explains why mutations that boost survival or reproduction become more common. When a mutation gives an individual a fitness advantage, that individual tends to survive longer and produce more offspring, passing the beneficial allele to the next generation. Over many generations, these advantageous mutations increase in frequency as they are preferentially inherited. This is different from genetic drift, which changes frequencies by random chance; mutation rate, which describes how often new mutations appear; and gene flow, which involves the movement of genes between populations. Therefore, natural selection is the mechanism driving the rise in frequency of beneficial mutations.