This is one of 14 Virtual Labs from McDougal Littell. In this interactive simulation, students work to answer the guiding question, “Why might Elodea plants be important in maintaining a healthy ecosystem?”, as they set up an aquarium system containing aquatic snails and an Elodea plant. Students are guided to review the problem, explore background information and laboratory equipment, develop a hypothesis, and then to plan and carry out an investigation to evaluate the hypothesis. Although the experimental design is highly guided, students do have to determine what their variables are and how to set up control and experimental conditions in various test tubes. Students may add Elodea and/or snails to the tubes, and they may incubate them under light or dark conditions. Students may also run multiple experiments. After conducting the experiment, students are prompted to collect, analyze, and draw conclusions from the data. Students record their work in a virtual lab notebook, which can be printed. Students tie these conclusions back to the original problem of setting up the aquarium. This resource could be valuable as part of a larger unit focused on the flow of energy and cycling matter in the processes of photosynthesis and cellular respiration.