In this section we take a look at the "big picture" of how the different living organisms we have looked at in other
sections (plants, animals, fungi), interact with their natural environment (geological features, climate, and so forth). This is the primary focus of ecology. A major topic of
discussion of this section, and a major concept of ecology, are ecosystems. Ecosystems are the
sum total of interacting living organisms and their non-living environment in an area is termed an ecosystem.
A diatom found in Crater
Lake, Stephanodiscus hantzschii; photo courtesy of Stan