Circulation or exchange of elements such as nitrogen and carbon between nonliving and living portions of the environment. Found on http://www.encyclo.co.uk/local/21804
All the processes by which nutrients are transferred from one organism to another. For instance, the carbon cycle includes uptake of carbon dioxide by plants, ingestion by animals, and respiration and decay of the animal. Found on http://www.ucmp.berkeley.edu/glossary/gloss5ecol.html