Genetic drift is an important mechanism of evolution, yet undergraduates often fail to understand how it leads to evolutionary change due in part to its random nature. This lesson plan describes a simulation-based activity that allows students to demonstrate the process of genetic drift across generations. Using a simulated population of tuco-tucos - a small rodent native to South America - students can explore how allele frequencies can change over time due to chance. Students will also demonstrate random changes in allele frequency (genetic drift) using two different population sizes (with an extended option for a third population size) so they may better conceptualize the impact of population size on genetic drift as an evolutionary force. Using inexpensive materials (beans and paper cups), instructors can actively engage students in the process of evolution. The simulations are followed by a brief discussion of two real-world examples of bottleneck and founder effects, two events when the impact of genetic drift can become more pronounced. The lesson then ends with a series of thought questions to reinforce student understanding of how genetic drift leads to evolution. This activity is appropriate for small or large class sizes and advanced high school and college biology courses. It can also be adapted for non-major college biology courses.