PCBs in the Last Frontier

A Case Study on the Scientific Method

Author:	Michael Tessmer Chemistry Department Southwestern College mtessmer@sckans.edu
Abstract:	This interrupted case study is based on current research involving the global transport of polychlorinated biphenyls (PCBs). Students are asked to propose several hypotheses and experiments in an attempt to determine how PCBs are transferred globally. As the case unfolds, it becomes clear that the transport mechanism is more complicated than scientists first thought. The case requires minimal background knowledge and is suitable for major and non-major courses in biology, chemistry, and environmental science.
Objectives:	Help students review the scientific method. Teach students how to better state hypotheses. Encourage students to design experiments that test a hypothesis. Introduce students to the scientific literature with a relatively easy-to-read article.
Keywords:	Experimental design; PCB; polychlorinated biphenyl; bioaccumulation; persistent pollutants; sockeye salmon; Alaska
Topical Area:	Scientific method
Educational Level:	High school, Undergraduate lower division
Formats:	PDF
Type/Method:	Interrupted; Journal Article
Language:	English
Subject Headings:	Biology (General) Chemistry (General) Analytical Chemistry Environmental Science Atmospheric Science Earth Science
Date Posted:	06/16/05
Date Modified:	N/A
Copyright:	Copyright held by the National Center for Case Study Teaching in Science, University at Buffalo, State University of New York. Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work.

Teaching Notes

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Answer Key

Answer keys provide answers to the questions posed in a case study. Since these questions are intended to be answered by students and are often graded, answer keys are password-protected and access to them is limited to registered instructors.

I found this case to be a very effective way to teach the Scientific Method to a group of non-major biology students. This is the first case I have taught since attending a Chautauqua Short Course this past summer with Kipp Herreid, and it worked extremely well. I asked the 23 students to self-select themselves into groups of 3 or 4 and then worked through the case with class discussion following each of Parts I–III. We did not have enough time to complete part IV in the 50 minute time frame.

I found that the case questions yielded some interesting and creative solutions. In many cases it offered up a springboard for discussion of local migration and PCB contamination issues. Students also asked about PCB contamination in Great Lakes Fish and other pertinent topics. This is one of the many topics that will be addressed throughout the semester. Rather than use the last few minutes of class on Part IV (though it seems a valuable thing to do), we discussed the advantages and shortfalls of the Scientific Method. Learning the Scientific Method through case participation will likely help the students complete future labs, for which they will need to construct hypotheses, design experiments, etc.

I found the referenced Nature (2003) article to be helpful and did not use any additional resources in class given the time constraint.

Margit Brazda Poirier
Department of Biology
Monroe Community College
Rochester, NY
mpoirier@monroecc.edu
9/22/2005

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