Organisms interacting in an area at a particular time.

The populations of plants, animals, and microorganisms living and interacting in a certain area at a given time.

all the populations of different species occupying a single ecosystem

An assemblage of organisms that are associated in a common environment and interact with each other in a self-sustaining and self-regulating relationship.

All the organisms (e.g., plants, animals, bacteria) that live in an area and interact with each other. See Ecosystem.