Mate selectivity, movement of individuals between populations, small populations, mutations and natural selection can all disrupt genetic equilibrium. In the absence of these factors, the frequencies of genetic traits in a population remain about the same over time, and the species do not evolve.Continue Reading
Mate selectivity means that, in a given population, individuals with certain genetic traits are favored by mates over those without those traits. Whether or not such a trait helps an animal survive, if it is able to breed more, its particular genetic traits become more prevalent in the population. Natural selection affects populations in the same way, but instead of occurring because of mate preferences, it affects which organisms survive long enough to breed.
When individuals of a species move from one population to another, this decreases the genetic variability within the population that they left, and increases the variability of the population to which they move. Mutations also introduce new genetic traits to existing populations. A large population tends to be more stable than a small one, since the large numbers of individuals dampen any chance that variation can occur. In a small population, chance can easily make it so that a particular genetic trait becomes more prominent in a generation and those that come after, whether or not it has any evolutionary advantage.Learn more about Molecular Biology & DNA