This document discusses the different types of organisms found in lakes, including zooplankton, insects, fish, amphibians, birds, and mammals. It notes that fish eat zooplankton and smaller fish, while planktivorous fish and some birds feed on plankton. Various bird species find food in different areas of the lake, such as the shore, water surface, or lake bottom vegetation. Mammals like muskrats and beavers feed on plants and small fish or muskrats. Pictures are also included of some common lake species like beavers and gulls.