Encyclopedia of Earth
Encyclopedia of Earth: Biogeochemistry: Phosphorus Cycle
Article explaining what the phosphorus cycle is, where it occurs, its place in the biotic world, and the environmental impact of human activities on the phosphorus cycle. (Published: October 8, 2009)
Other
Marietta College: Ecosystems
Complete illustrated discussion of energy flow within ecosystems, including discussions of trophic levels, ecological pyramids, food chains and webs, biological magnification, and cycles.
Ohio State University
Ohio State University: Concepts of Plant Ecology
An advanced discussion of plant interactions and relationships. Energy flow, nutrient cycling and succession are discussed. Try the quiz to check your understanding.