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Disappearing Marine Iguanas

A Case of Population Collapse


Author(s)

Conrad Toepfer
Division of Mathematics & Natural Sciences
Brescia University
bioprof44@gmail.com

Abstract

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.


Objectives

  • Refine hypotheses to single, preferably testable, statements.
  • Suggest possible experiments.
  • Develop sensitivity to issues of data interpretation such as the need to consider variation and the influence of how data are presented.
  • Appreciate inductive reasoning by seeing that the solution requires consideration and integration of multiple studies.
  • Illustrate the tentative nature of our conclusions by pointing out potential gaps in information or problematic experimental methods.

Keywords

Population biology; Galapagos Islands; El Nino / Southern Oscillation; ENSO; global warming; data interpretation; inductive reasoning; deductive reasoning; marine iguana; Amblyrhynchus cristatus

Topical Areas

Scientific method

Educational Level

High school, Undergraduate lower division, Undergraduate upper division

Format

PDF, PowerPoint

Type / Methods

Interrupted

Language

English

Subject Headings

Biology (General)  |   Ecology  |   Environmental Science  |   Earth Science  |  


Date Posted

10/22/2007

Teaching Notes

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Teaching notes are intended to help teachers select and adopt a case. They typically include a summary of the case, teaching objectives, information about the intended audience, details about how the case may be taught, and a list of references and resources.

Supplemental Materials

A complete set of figures used in the case is also available in two PowerPoint files according to figure orientation: iguanas1.ppt for the landscape figures (Figures 1, 2, 3, 4, 8, and 9) and iguanas2.ppt for the portrait figures (Figures 5, 6, and 7 and Table 1):


  iguanas1.ppt

  2-iguanas2.ppt

Answer Key

Answer keys for the cases in our collection are password-protected and access to them is limited to paid subscribed instructors. To become a paid subscriber, begin the process by registering.

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