Living things, whether plants or animals, continually interact with their surroundings in many ways. All of the organisms in a given area, plus the nonliving things in that area like water, soil, and air, comprise an ecosystem. The word ecosystem is a combination of the phrase "ecological system," and was coined in 1935 by A.G. Tansley, a British plant ecologist.

There are three major parts of an ecosystem: (1)the soil, rock, or bottom sediment on which the living matter rests or is attached, (2) the water and air above the bottom layer that provides the ecosystem's climate, and (3) the plants, animals, and microorganisms that live within the habitat. An ecosystem can be any size--from the Amazon basin of South America to a backyard pond where frogs and other creatures live. Some may contain thousands of species of plants and animals and may have very complex interactions. It may be...