[tallhappy]

When did you take intro bio?

[realpatriot71]

I had my first undergrad bio class 5 years ago

[Nebullis]

Realpatriot71 is using the definition for the biological species concept. This is the definition most often in use, today. There is a typological way of looking at species, by degree of difference between two populations, but it does not make a determination about mating success.