In this activity, students construct qualitative models of an ecosystem and use the models to gain a better understanding of direct and indirect ecological interactions. Qualitative modeling is described for use in two procedures, each with different educational goals and student backgrounds in mind. Part 1 is designed with the non-major or beginning ecology student in mind, and is intended both to improve student understanding of the ecosystem of interest and to provide a framework for the instructor to assess student learning. Part 2 is designed for more advanced students of ecology and involves the use of modeling software (POWERPLAY) to design researchable hypotheses to analyze the dynamics of ecosystem responses to simulated disturbances. Approximately two lab periods are required for either activity. In both cases, students will generate qualitative ecosystem models, undertake some degree of analysis, and provide responses to essay questions. Students will learn new tools and improve their skills at "qualitative reasoning" to understand the dynamics of complex systems, gain insights into their own understanding of the ecosystem they are studying, and use their models to predict possible experimental outcomes or patterns in the ecosystems they are studying. Students will become more cognizant of indirect effects and complexity through analysis of their models.