The most common definition of species is a biological definition based on the biological species concept and describes a species as a set of populations that can, under natural conditions, mate with one another to produce living, fertile offspring. This is fine for distantly related organisms like a dog and a dolphin, but what about a dog and a wolf? A domestic dog (Canis familiaris) and a wolf (Canis lupus) can mate and will do so if the conditions arise.
THE QUESTION ....
Define each of the two approaches to classifying and interpreting lifeforms: evolutionary systematics and cladistics.