Isolation from other populations. There is no migration of individuals into or out of the population. No net mutations 4. Random mating 5. No natural selection.
All genotypes are equal in survival and reproductive success.
Differential reproductive success can alter gene frequencies. In real populations, several factors can upset Hardy-Weinberg equilibrium and cause microevolulionary change. Small scale evolutionary change represented by a generational shift in a population's relative allelic frequencies. Of these five possible agents for microevolution, only natural selection generally leads to an accumulation of favorable adaptations in a population. The other four are nonadaptive and are usually called non-Darwinian changes.