1. Non random mating
In genetic equilibrium individuals must mate at random. However, in many species, individuals select mates based on heritable traits, such as size, strength, or coloration, a practice known as sexual selection.
2. Small population size
Genetic drift does not have major effects on large populations but can affect small populations. Thus evolutionary change due to genetic drift happens more easily in small populations.
3. Immigration or Emigration
Individuals who join a populations may introduce new alleles into the gene pool. Likewise individuals who leave may remove alleles from the gene pool. Any movement of individuals into (immigration) or out of (emigration) a population can disrupt genetic equilibrium, a process know as gene flow.
4. Mutations
Individuals who join a populations may introduce new alleles into the gene pool. Likewise individuals who leave may remove alleles from the gene pool. Any movement of individuals into (immigration) or out of (emigration) a population can disrupt genetic equilibrium, a process know as gene flow.
5. Natural Selection
if different genotypes have different fitness, genetic equilibrium will be disrupted, and evolution will occur.
