genetic drift that occurs when a population is drastically reduced in size. Some alleles may be lost from the gene pool as a result of random events.
Changes in allelic frequencies that occur when a small group is separated from a large population and establishes a colony in a new location
the formation of new species as a result fo an ancestral population’s becoming isolated by a geographical barrier
;the collection of mechanisms, behaviors and physiological processes that prevent the members of two different species that cross or mate from producing offspring, or which ensure that any offspring that may be produced is not fertile.
The increased reproductive isolation between two closely related species when they live in the same geographic region