Population

In biology, more particularly in population genetics, a population is the sum of all organisms of the same group or species living in the same geographical area, bearing capability of interbreeding. In a similar definition, a population is a group of individuals pertaining to the same species living in a defined geographical area and effectively or potentially interbreed. In sociology, population refers to a set of human beings. In statistics population refers to a finite or infinite collection of items under consideration.

Population dispersal
Populations or species can be classified according to the possibility of gene flow between them :


 * Allopatric populations: those that are physically separated, for example by geographic barriers.
 * Parapatric populations: those that largely are physically separate but has a small overlap zone where can occur the gene flow.
 * Sympatric populations: those who are not physically separated.