Video and audio editing, Jennifer Hildebrandt

Narrator: Dan Smith.

Looks at the processes that are fundamental to all ecosystems. First the concepts of primary productivity, trophic levels, food chains, energy pyramids and the flow of energy through ecosystems are introduced. The program then explains how carbon, nitrogen, phosphorous and water cycle through ecosystems and how human activities can disrupt these cycles and throw them out of balance leading to accelerated eutrophication in lakes in the case of phosphorus imbalances and global warming in the case of carbon imbalances.