The Hardy-Weinberg principle states that in absence of evolution, the allele frequencies of a population will stay the same over generations. This principle is used as a null model for population genetics and allows scientists understand evolutionary mechanisms.
Hardy-Weinberg equilibrium is calculated by multiplying the frequencies of each allele (p and q) for individual genotypes to calculate the genotype frequencies at equilibrium. p2 + 2pq + q2 = 1; p + q = 1
Infinite population size, random mating of individuals, no genetic mutations, no natural selection, and no gene flow.
Chance events that randomly remove individuals, resulting in new populations that have different allele frequencies from the original population.
If a population's size is reduced due to a major event it is called a bottleneck effect, whereas a founder effect occurs when a new colony is started by a few members of the original population.