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• The raw materials of an ecosystem

An ecosystem (or ecological system) is a collection of communities of organisms and the environment in which they live. Ecosystems can vary greatly in size. Some examples of small ecosystems are tidal pools, a home garden, or the stomach of an individual cow. Larger ecosystems might encompass lakes, agricultural fields, or stands of forests. Landscape-scale ecosystems encompass larger regions, and may include different terrestrial (land) and aquatic (water) communities. Ultimately, all of Earth's life and its physical environment could be considered to represent an entire ecosystem, known as the biosphere.

Ecologists often invent boundaries for ecosystems, depending on the particular needs of their work. (Ecologists are scientists who study the relationships of organisms with their living and nonliving environments.) For example, depending...