What is the term for the area in which a group of populations live?

The term that describes the area in which a group of populations live is "community." In ecological terms, a community refers to all the various populations of different species that cohabit and interact in a particular environment. This includes not only the populations of animals but also plants, fungi, and microorganisms that occupy the same space and may interact with one another through various relationships such as predation, competition, and symbiosis.

In contrast, a "region" typically refers to a broader geographical area that might encompass multiple communities or ecosystems. The term "biome" describes a large-scale ecosystem characterized by specific climate conditions and types of vegetation (like deserts or forests), which is wider in scope than just the communities it contains. An "ecosystem" refers to a biological community along with its physical environment, emphasizing the interactions between living organisms and their non-living surroundings. While related terms, they do not capture the specific focus of species interactions within a defined area as succinctly as "community" does.