Understanding evolutionary change requires an integrated understanding of genetics and evolution, as well as interrelating concepts from different levels of biological organization. However, students' knowledge about genetics and evolution often remains compartmentalized, and students struggle with thinking across levels. Thus, we present a classroom simulation of how selection affects both phenotypes and genotypes, which helps students distinguish between different levels of biological organization (i.e., phenotype and genotype) and track changes in phenotypes to changes in allele frequencies.