Morphological species concept- organisms can be classified is on the basis of morphology, or physical features. Issue with using this concept - example: mouse lemurs look very similar to each other but are actually at least 18 distinct species.

Domestic dogs, for example, can look very different but are actually all one species capable of interbreeding

If lions and tigers are brought together in captivity they can occasionally produce a hybrid called a liger or tigon, but these hybrids are not themselves able to reproduce

Biological species concept- a species is a group of organisms with a shared, closed gene pool. For example, lions produce offspring with other lions.

Ursus americanus is the genus species name for the American black bear. The first part of the name is the genus, a group of related species (in this case bears); the second part of the name is the species within the genus. In some cases, a subspecies can also be designated to further distinguish groups within a species, indicated by the addition of a third name. Ursus americanus has several subspecies, for example, Ursus americanus californiensis and Ursus americanus altifrontalis; these subspecies names refer to the geographical locations in which they’re found.

This is a difficult group and variation in genitalia within species may indicate the presence of species complexes. Molecular data should be included in future revisions of this genus as an independent test of species concepts.