Over time, a variety of views have been formed on the structure of ecological communities. A. Clements held that ecological communities were like organisms that compete with each other for dominance in a particular climatic region. B. Clements saw the community as a collection of thoroughly interdependent species progressing toward a single climax community. C. Gleason held that within a single climatic region, differing local factors would cause ecological communities to develop in different ways. D. Gleason believed that sharp divisions would exist between species in different habitats. E. Today's ecologists recognize that ecological communities must be precisely and permanently balanced. F. The current thinking is that communities are individualistic and largely accidental collections of species with similar needs and tolerances.