by
James A. Hewlett
Science and Technology Department
Finger Lakes Community College
This case study is designed for a freshman introductory biology course or a course on evolution. It is part of a series of cases that carry a similar theme, each with a slightly different story line. This series of cases is part of a contest called "Biolink," which is offered to all General Biology II students at Finger Lakes Community College in Canandaigua, NY. This contest is an annual event that gives students an opportunity to use the principles of evolution learned in class in an open-ended application of their knowledge. Department faculty judge the contest entries, and the winning submission is sent to be professionally produced as a poster, which is displayed in the hallway of the Science and Technology Department.
There are very few restrictions placed on the format of the submissions, which has led to some very creative contest entries. One student produced what looked like an issue of Time magazine, and her story was one of the lead stories (along with a cover shot of the animals). Another student created a laboratory notebook (complete with coffee stains) that documented the findings and field notes as if he were a biologist studying the animals. And another student produced an interactive web site complete with maps and graphs.
By working through this case, the student will:
The case that was developed for the first trial of the Biolink contest was distributed to the students with a restriction that they produce individual responses (the case involved a population of frogs in Costa Rica). In recent contests, however, including the 1999 contest in which this case was used, students were encouraged to work in groups. Groups were not allowed to exceed four in size. The ideal group size for the project is three students. This is the typical lab group size for the biology courses at Finger Lakes Community College. Since the students are already familiar with each other at the time the case is presented in class, we have the lab groups work on the case. Instructors use a variety of methods for establishing lab groups, and, therefore, the selection of the student groups for working with this case also varies.
After choosing the principles that they will use and selecting a story line, some groups may decide to produce a story that involves distinct tasks that can be assigned to individual members of the group. A recent example was a submission by a group that included an art major who developed some very creative props to go along with the case submission.
It is a good idea to distribute the case prior to the point in the course where the principles of evolution will be covered. This schedule can enhance student involvement in the classroom discussion of the subject since they will be motivated to ask questions to ensure that they are prepared for the case assignment. If students can see ahead of time that they will need to be able to apply these concepts to the case, they are more likely to be engaged in the classroom and will want to join in the discussion on speciation.
Students have two weeks to produce their responses after the principles of evolution have been presented in class. Evolution as a topic is covered in approximately four to five weeks in the General Biology II class at Finger Lakes Community College, and, therefore, the students have the case for approximately six weeks before their responses are due. In the last week of the evolution unit, some time is allocated in class for groups to meet to brainstorm some story ideas. This meeting gives the instructor a chance to interact with the groups and determine the types of stories that are being considered. It will also give the instructor a chance to correct any misconceptions that might have developed concerning some of the principles discussed in class. Over the next couple of weeks, students are encouraged to meet outside of class to discuss their case responses and work on the materials they will submit.
Before students can be expected to produce an original and creative evolutionary story in response to this case, they will need to have extensive preparation in three main areas:
To start, the principles on the concept list should be covered in class. When presenting these concepts, it is a good idea to provide several examples to go along with the basics of each concept. The examples help students think about evolution as a story. Some faculty distribute scientific papers and articles for students to read as a supplement to the classroom activities. If students are exposed to various evolutionary stories before working on the case, they will be better prepared to produce a well-constructed response. The instructor's examples should focus on the evolutionary explanation of very specific traits and behaviors for various organisms. In addition, the examples should present a mix of micro- and macro-evolutionary principles. Most general biology textbooks offer excellent examples for discussion.
Students will also need to review a wide variety of evidence in support of evolution. When students produce their evolutionary stories, they have to support their stories with valid evidence. To ensure their success in this endeavor, students must be familiar with the following areas tied to evolution:
Finally, students will need to have an understanding of the concept of species. I employ Ernst Mayr's 1942 biological species concept for discussion. According to the case, repeated attempts at mating individuals from the two populations is not successful. This often leads students to the idea that the two populations represent two different but closely related species in the same genus. Students are not forced to draw this conclusion. In fact, one student included an artificial means of fertilization in his story, which led to the production of viable offspring. He went on to explain their physical differences, but also included some strong arguments for the possibility that these are not two separate species.
I have included here two typical student papers:
These two responses are the products of individual students who were not working in groups. The students were enrolled in a General Biology course that was offered online through the State University of New York (SUNY) Learning Network. Case studies can be effective teaching and learning tools in this emerging course delivery mechanism. The logistics of establishing working groups online, however, is difficult. For this reason, my online students work on their responses individually, but they do have opportunities to discuss the details of the case in a discussion forum that is provided via the course web site.
The first paper was written by John Newhouse. John is an adult student who is taking courses part-time as part of a degree program in conservation. John's case response takes the form of a press release. It is important to stress to students that there are very few restrictions on how the story can be told. With this in mind, John suggested that the animal in the case was misidentified as a type of squirrel. He begins his press release with an identification of the animal, which he claims is a new species of marmot. Since the focus of the case is on the mechanism of speciation, this small change in taxonomy was not an issue. In his response, John focuses on several reproductive isolation concepts (behavioral, gametic, geographic) and then turns his attention to directional selection as his explanation for the morphological and physiological variations found between the two species.
The second paper was written by Omara Afzal. Omara is a 17-year-old high school senior from Plattsburgh, New York, who had never taken a college course and was enrolled in the online course as her first college experience. Omara's response takes the form of journal entries that track her research activities over the course of several months of field work. Her primary focus is on the concept of geographic isolation and the enhanced effects of genetic drift on small populations. Her assertion is that the environments on the two islands are so similar it is unlikely that differential selection pressures exist, which could account for a speciation event.
Audesirk, T. and A. Audesirk. Biology: Life on Earth, 5th ed. Upper Saddle River, NJ: Prentice Hall, 1999.
Campbell, N.A., J.B. Reece, and L.G. Mitchell. Biology, 5th ed. Menlo Park, Calif.: Benjamin Cummings, 1999.
Raven, P.H and G.B. Johnson. Biology, 5th ed. McGraw Hill, 1999.
Welcome to the Evolution Revolution: Your Complete Guide to Evolution
http://library.thinkquest.org/19926/
This site is an excellent reference site for information on evolutionary principles and includes an extensive reference list
Evolution and the Nature of Science Institutes Web
http://www.indiana.edu/~ensiweb/
ENSIWEB is a collection of classroom lessons housed at Indiana University that are designed to help biology teachers more effectively teach basic concepts in the areas of evolution and the nature of science. There are many excellent ideas on this site for teaching the principles of evolution.
National Association of Biology Teachers Evolutionary Science Page
http://www.nabt.org/sub/evolution/default.asp
This page from the National Association of Biology Teachers (NABT) lists many different resources on the principles of evolution and provides several excellent links to sites that are useful in teaching evolutionary principles in the classroom.
Acknowledgements: Publication of this case study on the National Center for Case Study Teaching in Science web site has been made possible with support from The Pew Charitable Trusts.