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Conrad Toepfer
Associate Professor of Biology, Division Chair
Division of Mathematics & Natural Sciences
Brescia University
Disappearing Marine Iguanas: A Case of Population Collapse

In this interrupted case study, students apply the scientific method to probe possible reasons behind declining marine iguana populations in the Galapagos Islands. Initially students are given rudimentary information and encouraged to generate wide-ranging hypotheses. Students are then given further information to help them refine their initial hypotheses into single, testable statements. As the case progresses, students shift to an examination of experimental methods and data interpretation. Over the course of the case, they utilize both inductive and deductive reasoning in developing their conclusions about the factors influencing marine iguana populations.  The case is appropriate for an introductory course for majors or non-majors in general biology, ecology, or environmental science.

Do You See What Eye See?: Eye Evolution and Development

A common misconception is that Darwin suggested that something as complex as the eye could not have evolved through natural selection. While the misunderstanding often comes from an incomplete reading of his argument, we have long known that intermediate varieties of eyes (e.g., eyespots, cupped eyes, and complex camera-type eyes) exist in a variety of organisms. Eyes are so common that it was thought that they had evolved independently 40–60 times. More recent molecular work, however, has identified the role of Pax6 genes and their homologs in the formation of eyes during development. The basic information for eye formation appears to have been present in the common ancestor to all bilaterans, and perhaps may be more ancient than that. This interrupted case study examines the history of evidence for eye evolution from Darwin’s initial postulates, through evidence of multiple intermediate forms, concluding in an examination of Pax6 homologs. The case is primarily for an introductory biology class but an additional section would be appropriate for upper-level evolution or developmental biology courses.