The Stream Ecology Unit (YES-Net) enlists students as scientists as they collect data on the numbers and kinds of aquatic insects found in local streams. This unit is unique in that it focuses on collecting long term data about the changes in the populations of macroinvertebrates. Students gain skills in field work and identification of these critters and have the opportunity to explore and interpret trends in their data as well as data collected by others. In addition, the field trip is surrounded by classroom lessons that teach key concepts such as the effect of abiotic and biotic factors on stream ecosystems, food webs, and data analysis and exploration.