The ecosystem may be defined as a functional unit of the biosphere, comprising the communities and non-living environment in a given area where there is physiological inter relationship and interaction between the communities themselves and also between communities and the non-living environment.
The term ecosystem used first time by British ecologist A.G. Tansley. According to Odum, “Ecosystem is defined as any unit that includes all of the organisms in a given area interacting with the physical environment, so that a flow of energy leads to clearly defined tropic structure, biotic diversity and material cycles within the system.”
The ecosystem concept, variously described, appeared under different names like microcosm, biocoenosis, holocoen, biosystem and geobiocoenosis etc. However, the term ecosystem is most preferred, where eco=environment body and system=an interacting and interdependent complex.
The concept can be applied at any scale. An ecosystem may thus be as small as a pond, a cropland, or as large as an ocean. The earth may be viewed as an ecosystem. However, these unit ecosystems are simply separated from each other with space and time, but functionally they all are indeed linked with each other, forming an integrated whole. c