Mayr's biological species concept states that all individuals of a species are able to breed together to produce fertile offspring and are reproductively isolated from other species.
To see if two or more individuals are of the same species they must mate together and give fertile offspring.
Limitations of this concept
- difficult to observe mating in the wild
- specimens collected may be dead or be from a single specimen
- fossil species can not breed
- some species reproduce asexually
