What is the appropriate term for an interacting group of individuals of a single type occupying a defined area?

The group of interacting individuals which live in a particular area belonging to the same species is referred to as the population of that species. The members belonging to a population have the capability to interbreed. The interbreeding ability of the members of a population ensures that the species can increase their numbers in that particular area.

Hence, the answer is 'a population'.