Activities in this packet were developed in reference to research conducted at the U.S. Environmental Protection Agency's Mid-Continent Ecology Division in Duluth, Minnesota (MED-D). The research helps us better understand the effects of pollutants on freshwater systems such as lakes, rivers, and streams and determines how we can best keep these systems healthy. These activities are designed primarily for students in grades 4-6. They address a spectrum of freshwater research efforts ranging from the methods used in collecting samples to ecosystem-level studies. An important aspect of these activities is the involvement of students and the ease of use by teachers. Each activity can be used as a stand-alone activity or presented as part of a sequence. It is hoped that these activities will give students a greater understanding and appreciation of freshwater systems as plant and animal habitats. The package includes 16 activities organized under four topics: (1) Water Facts and Usage; (2) Ecosystems; (3) Water Pollution; and (4) Collecting, Sampling, and Keeping Aquatic Organisms. (Author/SOE)