In order for two groups to be considered separate species, they should not ____.

A) reproduce
B) interact
C) interbreed and produce fertile offspring
D) be colocated
E) have the same ecological requirements

The biological species concept defines a species as a group of interbreeding populations that are reproductively isolated from other such groups. For two groups to be considered separate species, they should not interbreed and produce fertile offspring. This is the defining characteristic of a species. The other options may be important for ecological or geographic separation, but they do not necessarily determine species status.