Ecology is the science that studies the distribution and abundance of living organisms, the interactions among them, and the interactions among organisms and their environments. It is distinct from, and should not be confused with either the environmental movement or environmental science.
Ecology has been called "the most comprehensive and diverse of the sciences". The breadth of its scope makes it difficult to compose a single definition which encompasses the entire field of ecology, even for ecologists. Given this difficulty, it may be more useful to consider the subdisciplines that make up ecology. Major subdisciples are based on varying levels of complexity. Ecophysiology and behavior ecology study interactions between individual organisms and their environment. Population ecology (or autecology) focuses on populations of individual species. Community ecology (or synecology) looks at the interactions between different species within a defined area (an ecological community). Ecosystem ecology studies the flow of matter and energy through defined areas known as ecosystems.
There are other important divisions within the field of ecology. One of the oldest splits is between plant ecology and animal ecology. Other important splits include questions of scale, or the dichotomy between holism and reductionism and the debate between "top down" and "bottom up" control in ecological communities.
Ecophysiology or physiological ecology studies the response of individuals to their environment. Responses to temperature, moisture, light and nutrients fall within the scope of this field. Plant ecophysiology addresses such things as the response of photosynthesis and growth to environmental factors, while animal ecophysiology relates things like thermoregulation and energy consumption to the environment.
In an ecological context, populations consist of individuals of a single species in a given area. Population ecology studies the dynamics of these populations in relation to their environment. The development of the field was substantially influenced by demography. Population ecology was the first area of ecology to incorporate mathematical tools and to develop a substantial body of theory, including the works of Pierre François Verhulst, Raymond Pearl and L. J. Reed (logistic growth) and Alfred J. Lotka and Vito Volterra (Lotka-Volterra equations). Population ecology has made important contributions to the development of conservation biology and metapopulation biology.
Community ecology studies the interactions between populations of different species that interact (or could potentially interact) within a defined ecological community. Plant community ecology developed out of the work of Frederic Clements on succession. Animal community ecology developed separately, primarily from the work of Charles Elton who came to the idea from work on population cycles and food webs.
Ecosystem ecology studies the flow of matter and energy through living systems. Originally the term ecosystem was used by Arthur Tansley as a term for an ecological community. Ecosystem ecology developed out of the work of Raymond Lindeman, whose classic 1942 paper, The trophic-dynamic aspect of ecology defined the field that would become ecosystem ecology. Ecosystem ecology is closely linked with biogeochemistry.
Landscape ecology, one of the youngest branches of ecology, evolved in Europe after World War II and expanded into America in the 1980s. The German biogeographer Carl Troll introduced the term "Landscape ecology" in the late 1930s as an integration of the functional ecological approach and the spatial geographical approach to science. Troll's merging of these two concepts reflects the general nature of landscape ecology, which still deals with the patterns of ecosystems in space.
Applied ecology and conservation
Applied ecology employs the science of ecology to problems related to the management of biological systems. Conservation biology, restoration ecology and wildlife management are all applied ecological questions. Aldo Leopold was an early advocate of the application of ecological principles to wildlife management in the 1930s. In the 1970s concerns about pollution and environmental degradation spurred increased interest in applied ecology, which helped the discipline grow beyond its perceived status as an "intellectual lightweight" into an academically respectable discipline.
Although ecology is one of the youngest sciences, even the earliest science addresses ecological observations. The term ecology (oekologie) was coined by German biologist Ernst Haeckel in 1866 from the Greek word for "house" and the suffix -logy ("study of") -- i.e., it is the study of how organisms relate to where they live, or their environment). But ecology only began to develop into an experimental science in the late nineteenth century with the work of Henry Chandler Cowles on ecological succession on the Lake Michigan sand dunes. Building upon his ideas, Frederic Clements developed the idea of the ecological community as a "superorganism" whose development (via succession) was analogous to that of an organism. In the 1920s, Charles Elton's work gave birth to the field of animal ecology. G. Evelyn Hutchinson and his students, especially the Odum brothers (E.P. and H.T. Odum) and Robert MacArthur, helped move ecology from a primarily descriptive science into a quantitative science. Robert May was instrumental in the development of the field of theoretical ecology.
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