Active-learning approaches can improve understanding of core biological concepts. We describe a revised hands-on simulation for teaching evolution by natural selection, which focuses on prey–predator coevolution in escape/pursuit speed. It illustrates how selection pressure on individual speed increases average population speed through differential survival, while also reducing variation in speed among individuals. A simulated beneficial mutation helps differentiate the generation of individual traits from the process of natural selection and illustrates the effects of a beneficial mutation on immediate and subsequent generations. Overall, this exercise addresses several common misconceptions and allows students to collect and assess their own data, quantitatively. We report results from pre- and post-assessments in an introductory, undergraduate biology class, which indicate significantly improved understanding associated with the simulation.