I he concept of community encompasses only living organisms and ignores the physical and chemical environment in which those organisms live. If we include these features, including the underlying rock and soil, the water moving through the habitat, and the atmosphere permeating the soil and surrounding the vegetation, then we have an even more complex, interactive system that is called the ecosystem. Whereas the idea of community concentrates on the different species found in association with one another, the concept of the ecosystem is largely concerned with the processes that link different organisms to one another.Two fundamental ideas underlie the ecosystem concepti these are energy flow and nutrient cycling. Energy, initially fixed from solar radiation into a chemical form by green plants, moves into herbivores as a
result of their feeding on plants, and then moves on into carnivores as the
-herbivores are themselves consumed. Since herbivores rarely consume all
the available plant material, and since carnivores do not eat every individ-
ual of their prey organisms, some living tissues are allowed to die naturally,