A species is a difficult unit of life to describe
biologically, except for those organisms that engage in sex. In those
cases, their genetics, behavior, and geographic distribution defines
the population. Geographic separation and/or the constant pressure exerted
on it by mutations within that population leads to the eventual creation
of new species by the process of natural selection, whereby the mutant
best suited to its new environment stands the best chance of survival.
The species concept is the lynch pin upon which the science of biology