The chemical elements on which life is based move through grand global cycles involving the atmosphere, the oceans, and the land, taking millions of years for completion and the start of a new cycle. Living things keep the cycles moving, with energy from the sun as a driving force for plants and other primary producers.

When you enter this program, you will view scenes from a variety of biomes. In each scene, you can select a cycle, and then click on something in the scene to learn how it participates in the cycle you have selected. Explore each scene as extensively as you like. After a few scenes, you will begin to get review questions to help you check on what you have learned.

Click on the Next button to start the program.