The Hardy-Weinberg principle and associated calculations are often challenging for students to learn for three reasons. First, several assumptions need to be understood to correctly apply the principle. Second, a series of calculations are required for proper application. Third, the principle, assumptions, and calculations are often taught separately from students observing population changes over time. We describe a classroom activity in which students investigate how the allele frequencies of soft-shell clam (Mya arenaria) populations change over time as a result of environmental disturbances by simulating the effects on population data. These classroom population changes are then compared to authentic research data collected on populations of M. arenaria. This activity was implemented at three institutions in introductory- and senior-level biology courses. Students reported that the activity helped them better understand and apply both the principle and its calculations.