Ecology is the scientific study of interactions of organisms with one another and with the physical and chemical environment. "Ecology" comes from the Greek words oikos, meaning "house," and logos, meaning "logic" or "knowledge." The term was coined by German zoologist Ernst Haeckel in 1870. Although 'ecology' includes the study of environmental problems such as pollution, the science of ecology mainly involves research on the natural world from many viewpoints, using many techniques. Modern ecology relies heavily on experiments, both in laboratory and in field settings. These techniques have proved useful in testing ecological theories, and in arriving at practical decisions concerning the management of natural resources.

An understanding of ecology is essential for the survival of the human species. Our populations are increasing rapidly, all around the world, and we are in grave danger of outstripping the earth’s ability to supply the resources that we need for our long-term survival. Furthermore, social, economic and political factors often influence the short-term distribution of resources needed by a specific human population. An understanding of ecological principles can help us understand the global and regional consequences of competition among humans for the scarce natural resources that support us. Ecology is a science that contributes considerably to our understanding of evolution, including our own evolution as a species. All evolutionary change takes place in response to ecological interactions that operate on the population, community, ecosystem, biome and biosphere levels. Studies conducted within the scientific discipline of ecology may therefore focus on one or more different levels: on populations of a single species, on an interacting community involving populations of many species, on the movement of matter and energy through a community within and ecosystem, on large scale processes within a biome, or on global patterns within the biosphere.