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
Lenntech: The Phosphorus Cycle
A concise explanation of the phosphorus cycle. Also contains a flow diagram which illustrates the flow of phosphate through the cycle.
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.
University of Illinois
University of Illinois Extension: Energy and Ecosystems Use Some Lose Some
Life on Earth is possible because energy flows one way through ecosystems, while matter cycles endlessly. Water and elements, such as carbon, nitrogen, phosphorous, and sulfur are examples of matter that cycles through ecosystems.