Ecology is the scientific study of the interrelationships of plants, animals, and the environment. In recent years, the word has sometimes been misused as a synonym for environment. The principles of ecology are useful in many aspect of the related fields of conservation, wildlife management, forestry, agriculture, and pollution control.
The world ecology (Greek, oikos, "house," and logos, "study of") is generally believed to have been coined by Ernst Haeckel, who used and defined it in 1869. The historical roots of ecology lie not only in natural history, but in physiology, oceanography, and evolution as well. It has occasionally been called scientific natural history (a phrase originated by Charles Elton) because of its origin and its heavy reliance on measurement and mathematics. Ecology is variously divided into terrestrial ecology, fresh-water ecology (limnology), and marine ecology, or into population ecology, community ecology, and ecosystem ecology.

Ecological Classification of Organism
Ecologists commonly classify organisms according to their fucntion in the environment. Autotrophs ("self-nourishers," also called producers), which are mainly green plants, manufacture their own food from carbon dioxide, water, minerals, and sunlight, whereas heterotrophs - a wide assortment of organisms - lack the metabolic machinery to synthesize their own food and must obtain it from other sources.
Some heterotrophs - the herbivores - eat plants, and some - the carnivores, or predators - eat animals. Some, called omnivores, eat both plants and animals; others eat only dead plants and animals. Some, called scavengers, eat large dead organisms. Some smaller heterotrophs, such as bacteria and fungi, feed on dead organisms; they are called decomposers. Parasites eat living organisms, but, unlike predators, do not devour them at one time. Parasite include forms such as ticks and fleas, which live on their hosts, and others, such as tapeworms, roundworms, and bacteria, which live within their hosts.

Related Topic :
Endangered Species