The members of a single type of living organism in an ecosystem are called a population.
In ecology, a population is a group of organisms belonging to the same species that live in a particular area and interact with one another. For example, all the gray wolves living in a defined region can be studied as one wolf population, while all the oak trees in a forest may form another population.
The term is more specific than “community.” A community includes populations of different species living and interacting in the same place, such as trees, birds, insects, fungi and mammals in a forest. An ecosystem goes one step further by including both the living community and nonliving factors such as soil, water, sunlight and temperature.
Scientists study populations by examining births, deaths, immigration and emigration. These processes affect population size and density. A population is also not necessarily every member of a species on Earth; it usually refers to members occupying a defined geographic area. The word “species” names the biological type itself, while “population” describes a local group of that species.