BIOLOGICAL SPECIES CONCEPT
What does this concept mean?Edit
Under this concpet species are defines by the reproductive isolation of the species. If two individuals come together and cannot reproduce viable offspring, then they are to be considered separate species. Some scientists may argue that this concept cannot be universally accepted because not all species can come together in nature due geographical barriers. And that it cannot be proven that the species are indeed spearate.
There are many other concepts that scientists debate to classify species, like the Morphospecies Concept, the Phylogenetic Species Concept and many more. Since scientists cannot come together with a universal system of genetic lineages there continues to be variations of the definition of species.