Ecology is the scientific study of the way that living organisms interact with their environment. "Ecology" comes from the Greek words oikos, meaning "house," and logos, meaning "logic" or "knowledge." The term was coined by German zoologist (scientist who studies animals) Ernst Haeckel in 1870.
While many people confuse the work of an "ecologist" with that of an "environmentalist," there are significant differences between the two occupations. Environmentalists seek to preserve natural systems. Ecologists, while they may share the ideals of environmentalists, are mainly involved with gathering information about the communities of animals and plants, as well as the physical elements (such as rocks and soil) present in a given geographical area.
Sources: Barnes-Svarney, Patricia. The New York Public Library Science Desk Reference, p. 458; Cunningham, William P., et al. Environmental Encyclopedia, pp. 248-50.