Britannica Educational Publishing 
Ecology [PDF ebook] 

Life on Earth can be viewed as a complex network of interactions between living organisms and their respective environments. By parsing the natural world into various ecosystems and biomes, the extent and significance of such interaction among species and between organisms and their natural habitats becomes abundantly clear. The study of ecology forms the heart of this engaging volume, which explores the formation of ecological communities and examines the biological diversity that forms the backbone of life on the planet.