Some organisms' cells vary greatly in appearance and perform very different roles in the organism. Students explore both terrestrial and aquatic environments. In the activities, students determine the environmental preferences, optimal conditions, and tolerances of several organisms, by examining the specific needs of that organism. At the conclusion of each set of investigations, students communicate their findings in the form of recommendations for optimal environmental conditions for each organism. Insects and various other organisms depend on dead plant and animal material for food.
Organisms interact with one another in various ways besides providing food.
Many plants depend on animals for carrying their pollen to other plants or for dispersing their seeds. Changes in an organism's habitat are sometimes beneficial to it and sometimes harmful. Most microorganisms do not cause disease, and many are beneficial. Over the whole earth, organisms are growing, dying, and decaying, and new organisms are being produced by the old ones. Fossils can be compared to one another and to living organisms according to their similarities and differences.