[Free Registration/Login may be required to access all resource tools.] A population is a group of organisms of the same species, all living in the same area and interacting with each other. Since they live together in one area, members of the same species reproduce together. Ecologists who study populations determine how healthy or stable the populations are. They also study how the individuals of a species interact with each other and how populations interact with the environment. Learn more about features of populations in this learning module produced by CK-12.