20160403 - gene pool

Gene pool

A large gene pool indicates extensive genetic diversity, which is associated with robust populations that can survive bouts of intense selection. Meanwhile, low genetic diversity (see inbreeding and population bottlenecks) can cause reduced biological fitness and an increased chance of extinction, although as explained by genetic drift new genetic variants, that may cause an increase in the fitness of organisms, are more likely to fix in the population if it is rather small.
When all individuals in a population are identical with regard to a particular phenotypic trait, the population is said to be monomorphic. When the individuals show several variants of a particular trait they are said to be polymorphic.

 https://en.wikipedia.org/wiki/Gene_pool
 https://adapaproject.org/bbk_temp/tiki-index.php?page=Leaf%3A+How+can+the+gene+pool+of+a+population+decrease+or+change%3F