Evolution is a change in allele frequency in a population over a period of time.
A population is a group of individuals of the same species in a given area whose members can interbreed and hence share a common group of genes known as a gene pool.
Each gene pool comprises all alleles for all characteristics of all individuals.
The allele frequency is the number of alleles of a given type as a proportion of the total number of alleles for that trait.
In 1908, Hardy and Weinberg constructed a model of a population that was not evolving, and laid out the conditions in which such a population would exist: a large population size with no migration, no mutation, no natural selection, and random mating.
If we track allele frequencies in a population over a succession of generations and find that the frequencies of alleles deviate from the values expected from the Hardy-Weinberg equilibrium, then the population is evolving.
Determine the allele frequency:
Hardy Weinberg Equation (p + q = 1) concerns estimating the frequency of alleles in a population. Each gene usually has two alleles (diploid organism), one from each parent.
These alleles are denoted as the dominant (A) and recessive (a) forms. These are represented as ‘p‘ and ‘q‘ in the equation. In a population, the combined frequency of both the alleles must equal 1 (100%). So, if the frequency of one allele is known, it is possible to calculate the frequency of the other allele simply by rearranging the equation.