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Question

A population in which the frequency of alleles remains the same over generations is said to be in genetic equilibrium. Describe carefully and completely one mechanism by which a populations' genetic equilibrium can be disrupted and result in the process of evolution.

Answer 1

Genetic Drift is what you are looking for:

http://en.wikipedia.org/wiki/Genetic_dri...

Basically evolution will mean that when small mutations occur if a mutation is favorable for an organisms existence/survival or gives it an competitive advantage, then it will be selected.  If a certain allele is favorable then it will dominate that population and its frequency within that population will increase.