The<unk>  was defined by Ernst Mayr in 1963 to be the<unk>  of establishing a new population by a small number of individuals, carrying only a small fraction of the original population's genetic variation.  As a result, the new population may be distinctively different, both genetically and phenotypically, from the parent population from which it is derived. In extreme cases, the<unk>  is thought to lead to the speciation and subsequent evolution of new species. The<unk>  is a feature that can also occur in memetic evolution.
In the figure shown, the original population has nearly equal numbers of blue and red individuals.  The three smaller<unk>  populations show that one or the other color may predominate<unk> , due to random sampling of the original population.  A population bottleneck may also cause a<unk>  even though it is not strictly a new population.
In addition to<unk> s, the new population is often a very small population and so shows increased sensitivity to genetic drift, an increase in inbreeding, and relatively low genetic variation.  This can be observed in the limited gene pool of Easter Islanders and those native to Pitcairn Island.
Founder effect
Carrier generation and recombination
Defence mechanism
Homology 
Mutualism
Mixture
Conformational isomerism
Penetrance