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Eva S. Horna-Lowell
Graduate Student
Biological Sciences
University of Denver
Selection on a Case by Case Basis 

This "clicker case" gives students an opportunity to apply their understanding of three different types of selection (directional, stabilizing, and disruptive) to a variety of model systems. The case describes each type of selection in detail, presents a paradigm case of each, and then uses clicker questions to test whether students can identify the mode of selection in other systems (answers included in the teaching notes).  Nine different studies are presented so that students gain a broad understanding of selection and how environmental factors can impact species differently. The case concludes with an optional discussion activity (also discussed in the teaching notes) to deepen understanding. Although designed for a high school classroom, it could easily be used in a lower-level college course as an engaging introduction or review of concepts. The case could be used at the beginning of an evolution unit, but it would be helpful if the students were familiar with natural selection before completing the activity.