Ecology
Ecology the science which studies the distribution and abundance of living organisms, interactions between them, and the interactions between organisms and their environment.
Scope
Ecology is a multi-scale science; ecologists have been hard-pressed to come up with a single definition which encompasses the entire field of ecology.[1] Given this difficulty, it may be more useful to consider the subdisciplines which make up ecology. Major subdisciples are based on varying levels of complexity. Ecophysiology and behavior ecology study interactions between 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
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.[1]
Populations
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 work 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.
Communities
Community ecology studies the interactions between populations of different species which 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 from the work of Charles Elton who came to the idea from work on population cycles and food webs.
Ecosystems
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[2] defined the field that would become ecosystem ecology. Ecosystem ecology is closely linked with biogeochemistry.