The Next Generation Science Standards (NGSS Lead States, 2013) recommend that science courses engage communities of students in scientific practices that include building accurate conceptual models of phenomena central to the understanding of scientific disciplines. We offer a set of activities, implemented successfully at both the secondary and postsecondary levels, that involve students in guided inquiry toward creation and progressive revision of a robust model of selection that accounts for both natural and sexual selection and their complicated relationship to one another at the level of individuals and populations. Requiring students to progressively revise their models in light of data and previous understanding replicates scientific practice and allows for authentic assessment of students' growing content knowledge, understanding, and skills regarding scientific modeling and communication processes.