Change in the genetic makeup of a population from generation to generation. Refers to adaptations that are confined to a single gene pool.
Evolutionary change above the species level, such as the appearance of feathers and other such novelties, used to define higher taxa.
Biological Species Concept
Defines a species as a population or group of populations, whose members have the potential to interbreed in nature and produce viable, fertile offspring but are unable to produce viable, fertile offspring with members of other populations.
Two populations of organisms are isolated if their members are unable to interbreed and produce fertile offspring. Various structural, behavioral, and biochemical features can prevent interbreeding and thus reproductively isolate populations as distinct species.
A reproductive barrier that impedes mating between species or hinders fertilization of ova if interspecific mating is attempted.