Natural variation, including the continual selective pressures that lead to speciation, is one of the more dynamic aspects of biology. However, traditional instruction on the topic is often passive in nature, leaving little opportunity for scientific inquiry. In this laboratory exercise, we use a statistics-based, guided-inquiry approach to engage students in natural variation. Students are introduced to speciation and classification by using a dichotomous key to identify various common local trees on the basis of leaf characteristics. Once the students have learned characteristics useful for identification, they are given two leaf samples, a sugar maple and an “unknown.” They are asked to choose characteristics and collect quantitative data in order to determine whether the unknown is a sugar maple. Before data collection, students form hypotheses related to the identity of their unknown, followed by statistical comparison of means to support or refute their original hypotheses. In this way, students gain an appreciation for the activities undertaken by taxonomists that are related to natural variation and classification.