Key terms cont.

* Genetic drift- a random change in allel frequency caused by a series of change occurrences that cause an allel to become more or less common.

* bottle neck effect- a change in allel frequency following a dramatic reduction in the size of population .

* founder effect- a change in allel frequencies as a result of the immigration of a small group of a population.

* genetic equilibrium - a situation in which the allel frequencies in a population remain the same.

* sexual selection- the process by which individuals select mates on the basis of heritable .

* species- a population whose members can breed and produce fertile offspring.