A

Ecology

Ecology is the study of how plants, animals, and other organisms interact with each other and with their environment, or "home." The word "ecology" comes from the Greek word oikos, which means "home." Ecology is also the study of the abundance and distribution of organisms. An ecologist, for example, might try to find out why a species of frog that used to be common is now rare, or why fir trees are rare in a dry pine forest but common in a moister habitat.

Ecologists study living organisms in different ways. One might study a population, a group of individuals that can interbreed with each other; a community, the many species that inhabit an area; or an ecosystem, a community of organisms along with the nonliving parts of their environment. The nonliving parts, which ecologists refer to as "abiotic" components, include air, water, soil, and weather.

Population ecologists study what makes populations go extinct, what regulates populations at intermediate densities, and what makes populations increase in size. A major cause of extinction is loss of habitat or the break up of habitat into patches. Community ecologists study the relationships among different species; for instance, how groups of predators and prey affect one another.

The study of ecosystems means examining how all the parts fit together. An example of this is carbon in the atmosphere, which is taken up by plants during photosynthesis. Animals eat the plants, or eat the animals that ate the plants, and then exhale the carbon as carbon dioxide. The carbon cycles through networks of organisms, the atmosphere, and the Earth itself. Another example are shellfish, which make their shells from carbon. These shells drop to the bottom of the ocean to form thick sediments. Millions of years later, geological processes lift them up as mountains. The study of ecosystems is truly the study of life on the Earth.

SEE ALSO COMMUNITY; ECOLOGY, HISTORY OF; ECOLOGICAL RESEARCH, LONG-TERM; ECOSYSTEM; PLANKTON; POPULATION DYNAMICS; THEORETICAL ECOLOGY

Jennie Dusheck

Bibliography

Ecological Society of America. <http://esa.sdsc.edu/>.

Molles, Manuel C. Ecology, Concepts and Applications. 3rd ed. Boston: McGraw-Hill, 1999.

---

Founded in 1915, the Ecological Society of America is a non-profit organization of scientists that aims to promote ecological science, increase the resources available for the conduct of ecological science, and ensure the proper use of ecological science in environmental decisionmaking by improving communication between the ecological community and policy-makers.

---