It also explains the countless millions of now extinct species which existed in the past. There are two main approaches to the study of evolution. The study of the basic mechanism of evolution. The second of these two approaches involves, in part, the subject of population genetics. Evolution may be expressed as a change in gene frequency from one generation to the next in a population.
Gene frequency is the frequency of an allele at a given locus in a population.
Changes in gene frequency may be brought about by non-random mating, mutation, migration, selection chance. Population of individuals. Each individual has two copies of the A gene. The big A allele or the little a allele. An individual in a diploid population which reproduces sexually is the result of one male gamete plus one female gamete being combined to form a zygote.