What basis do biologists use to separate species?

Biologists commonly use interbreeding capabilities as a key criterion to separate species, primarily because the biological species concept defines a species as a group of organisms that can potentially interbreed and produce viable, fertile offspring. When two populations can interbreed and produce offspring that are also capable of reproducing, they are considered the same species.

This focus on interbreeding capabilities is significant as it addresses the real-world processes that contribute to the formation and maintenance of species. If two groups cannot interbreed due to various reproductive barriers (such as geographical isolation, temporal differences in mating, or behavioral differences), they are classified as separate species, even if they may appear similar in terms of physical characteristics or exhibit similar genetic profiles.

While genetic differences, mating behaviors, and physical characteristics are important aspects of understanding biodiversity and can aid in distinguishing closely related species, the fundamental reproductive isolation element provided by interbreeding capabilities solidifies the definition of species in a biological context. Hence, this criterion often provides a more definitive and practical method for distinguishing between species in the field of biology.