Biological evolutionary models have become popular tools for inquiry. Models can help expose complex systems and guide experimentation. Not all research questions require modelling. However, evolutionary models are helpful at quantitative predictions like determining the mathematical relationships among genotypes and phenotypes. The activities presented in this article allowed students to conceptually explore and apply mathematical models of fitness through a hypothetical activity where black-footed ferrets eat prairie dogs over several generations. In addition, students examined models of butterflies being eaten by a bird, showing directional, stabilizing, and disruptive selection. Finally, students applied a mathematical model created in Excel by entering relative fitness values and interpreting the resulting graphs.