Case Teaching Notes for
“The Coelacanth: An Odd Fish”

Introduction / Background

This is a redesign of a case by Robert H. Grant entitled “A Strange Fish Indeed: The Discovery of a Living Fossil,” originally published in 2005 by the National Center for Case Study Teaching in Science as part of its online case collection (see http://www.sciencecases.org/strange_fish/strange_fish.asp). It has been reformatted to use clickers and PowerPoint, and to further emphasize the role of Marjorie Courtenay-Latimer. I (Eric Ribbens) use the singular pronoun below, but it cannot be emphasized enough that the original case was written and designed by Robert Grant, and that he has graciously permitted me to “morph” his case into the format you see it here.

The case is designed for large introductory biology classes that use clickers (personal response systems) to manage and collect student input. Therefore, the case has clicker questions (marked, for example, CQ#1, CQ#2, etc.) with the correct answers given in the Answer Key that accompanies the case. Before the PowerPoint presentation is used for teaching the case, it is expected that the professor will format the clicker questions for use with the specific hardware/software system that is being used in the course.

While it is beyond the scope of this case to explain how to teach using clickers, this case was written as part of an NSF grant designed to show the advantages of using clickers to teach cases. Teaching cases with clickers to larger classes is different from teaching cases to smaller classes. To successfully teach this or other clicker cases, the professor will need to manage time, teach students how to respond with clickers, and consider whether he or she wants to have follow-up assignments, pre-case handouts, or other materials. As written and designed, this case is intended to be taught in a single 50-minute block of time; optional follow-up assignments are described below.

Students should have some background in evolution and the fossil record before engaging this case.

Objectives

• Explore the excitement of discovering a new species.
• Present the concept of “living fossils.”
• Encourage students to think about what should be done next.

The last objective is a deliberately vague yet important goal. Most young scientists have difficulty thinking comprehensively about an interesting issue and selecting avenues of investigation that are most likely to be feasible and fruitful. This objective can be met by exploring coelacanth conservation, by researching coelacanth ecology, or probing more deeply into the evolutionary relationships of coelacanths and other fishes.

Misconceptions

• Scientific discoveries are made by men, not women.
• A living fossil means that the species was extinct and has come back to life or evolved again.
• Everything that was once alive is represented in the fossil record.
• Primitive or ancestral means inferior, while advanced or derived means superior.
• Evolution and the fossil record are rife with misconceptions, including:
  • The fossil record is not only incomplete but biased.
  • Phylogenetic similarity should correspond with the evolutionary time scale (transformist viewpoint).
  • “Missing links” must be exactly intermediate.
• Since the coelacanth is phylogenetically between tetrapods and many fishes, it is the ancestor of tetrapods.

Classroom Management

This version of Robert Grant’s original case is set up for large lecture sections and uses clickers (personal response systems) to collect and manage student responses. It is expected that students are already familiar with the concept of clickers to enter responses. When I teach large lecture sections, I usually use informal small groups, i.e., we often break into small group work, in which I expect students to combine into groups of two to four students to discuss and solve a problem together. Students are often resistant to this small group concept at first, feeling that it lets the struggling students cheat and doesn’t help the smarter students (which, of course, is what every student believes they are). Thus, when I teach students how to use clickers and why cases are important, I have them practice forming small groups; my teaching assistant and I patrol the entire classroom and insist that everyone get involved in a small group. This takes some assertiveness, but getting everyone involved pays off in the end. It helps me to tell the students that the more struggling students learn by discussing a problem, and better students learn too when they explain the answer to their friends. We use this case near the beginning of the semester, but not as our first case.

It is also worth noting that this case is an excellent introduction to many different aspects of evolutionary theory. As it is written, it is designed for an introductory course fairly early in the semester, but it could easily be modified or extended to explore a variety of related evolutionary topics. Here are some potential questions you could explore:

• The concept of fitness: If this fish has been around for a long time, why isn’t it abundant?
• The concept of missing links: What is a missing link? Shouldn’t missing links be exactly intermediate? Why are missing links interesting?
• The concept that ancestral traits are inferior and derived traits are superior: You could point out that lungs are ancestral and swim bladders are derived. Does that make mammals inferior to the fishes? In fact, the whole concept of inferiority as most students define it has nothing to do with evolution.
• The concept that the fossil record is incomplete and biased: Why isn’t it complete? Why don’t all taxa get equally well represented? On the other hand, even though it’s incomplete we can learn a great deal from it.

This case could also be expanded for a more ichthyological course. For example, osmoregulation in coelacanths resembles the pattern seen in cartilaginous fishes, with circulation of urea. Also, coelacanths are viviparous.

Teaching the Case

I display the PowerPoint presentation and ask various students to read Slide 1, Slide 2, Slide 3, and Slide 4. We then shift to the first discussion question (Slide 5), which asks students what is different about the fish that Marjorie Courtenay-Latimer noticed on the deck of a fishing boat in late December 1938. We look at the illustration of a coelacanth on that slide and I ask the class to tell me what they see. Usually students come up with a list including odd fins, a funny-shaped tail, and a head with some sort of a constriction behind it. We then return to Marjorie’s story (Slide 6) and the second discussion question (Slide 7), which I ask students to discuss in informal small groups.

The first clicker question (Slide 8) asks what Marjorie should do, and the next slide (Slide 9) describes what she actually did: She stuffed the fish in a taxicab and took it to back to the museum where she worked. Clicker question #2 (Slide 10) asks students what they think the museum director’s response was to Marjorie’s find, with Slide 11 recording her dismay at his telling her that it was just a rock cod. At this point, I put up a picture of a rock cod (Slide 12), which makes my students indignant: her fish looked quite different! After we have briefly discussed the differences and looked at various pictures of the two kinds of fish (Slide 13, Slide 14, and Slide 15), we return to the story, introducing fish expert Dr. J.L.B. Smith (Slide 16, Slide 17, Slide 18, Slide 19, and Slide 20).

Clicker question #3 (Slide 21) explores a difficult topic for my students: Why hadn’t this fish been found before? I have found that many of my students think it must have gone extinct and then reappeared, or that it should have always been in the fossil record all along and that someone screwed up. Then we shift to the concept of a “missing link” (Slide 22 and Slide 23). Is the coelacanth a missing link? I show the slide with an evolutionary tree that shows the lobe-finned fishes between the ray-finned fishes and the lungfishes (Slide 24). I then ask clicker question #4 (Slide 25), after which we return to the diagram of the evolutionary tree, which shows that the coelacanth is more closely related to mammals and other more derived vertebrates than the ray-finned fishes are (Slide 26).

Clicker question #5 (Slide 27) explores another common mistake: that the more evolutionarily advanced an organism is, the more abundant it will be. My students commonly conflate derived traits with successful traits.

The discussion question in Slide 29 asks students what should Marjorie Courtenay-Latimer and J.L.B. Smith do next? In my opinion, this is an important question, one worth spending some time exploring. I ask students to identify three things they think should be done, and then to pick one and write a paragraph explaining what they think should happen and why. Then I pick several groups and as a class we listen to their proposals and discuss the merits or obstacles of each.

After this we read the fun facts (Slide 31 and Slide 33), and then I ask them the discussion question about discovery (Slide 35): If native people knew about coelacanths but the western world did not, did Marjorie Courtney-Latimer discover it? Did J.B.L. Smith? This is a good question to explore the concept of western thought and its accompanying arrogance. It is also worth mentioning the concept of serendipity: that many important discoveries are made even though people were not searching for that result. We end with what is known today (Slide 36).

Assessment

As mentioned above, this case was developed as part of an NSF-sponsored grant (# DUE 0618570) to determine whether clicker cases such as this one produced greater learning than the traditional lecture approach. As part of that project, the clicker cases had questions that were asked of students both before and after the class in which the material was presented. A transfer question was also developed for the case. This is a question designed to test whether a student could apply the knowledge that was given by the instructor in class to a new situation—a test of higher level thinking, according to Benjamin Bloom’s taxonomy of cognitive domain. These questions and their answers are presented in the Answer Key (see below).

Answer Key

Answers to the questions posed in the case study are provided in a separate answer key to the case. Those answers are password-protected. To access the answers for this case, go to the key. You will be prompted for a username and password. If you have not yet registered with us, you can see whether you are eligible for an account by reviewing our password policy and then apply online or write to answerkey@sciencecases.org.

References and Sources

The Fish Out of Time

http://www.dinofish.com/ Last accessed: July 22, 2009

All about coelacanths, with pictures, videos, and descriptions. Links to Recent History, a Coelacanth webcam, Biology and Behavior, and Conservation are particularly helpful. Biology and Behavior includes animations of fin movements and other useful biological information.

Natural History Highlight: The Coelacanth: More Living than Fossil (May 2003)

http://www.mnh.si.edu/highlight/coelacanth/ Last accessed: July 22, 2009

The Smithsonian National Museum of Natural History coelacanth website. A very good summary of coelacanth biology, anatomy, and evolutionary relationships. A good list of references is attached. This is a great website to begin with.

The Coelacanth

http://www.unmuseum.org/coelacan.htm Last accessed: July 22, 2009

The Museum of UnNatural Mystery’s coelacanth website. Retells the story of Marjorie Courtenay-Latimer, with additional information about J.B.L. Smith and other discoveries.

Animal Species: Coelacanth, Latimeria chalumnae Smith, 1939

http://www.amonline.net.au/fishes/fishfacts/fish/coela.htm Last accessed: July 22, 2009

From the Australian Museum Fish website. A slightly different description of the find of the coelacanth. Good information about the discovery of another species, and a useful list of additional references if you want to dig more deeply into this fascinating group. Some good (and different) pictures.

“On the Trail of the Coelacanth, a Living Fossil” by Susan L. Jewett for the The Washington Post, November 11, 1998

http://www.washingtonpost.com/wp-srv/national/horizon/nov98/fishstory.htm Last accessed: July 22, 2009

Washington Post special news story about the find of a coelacanth in an Indonesian fish market.

Ancient Creature of the Deep

http://www.pbs.org/wgbh/nova/fish/ Last accessed: July 22, 2009

NOVA website covering coelacanth anatomy, Marjorie’s discovery, a coelacanth quiz, and information about other unusual animals in the ocean.

Diving for Coelacanths

http://www.coelacanth-diver.co.za/ Last accessed: July 22, 2009

The goal of this website is to keep track of information about diving to observe coelacanths in their habitat.

Slide Credits

Acknowledgements: This material is based upon work supported by the NSF under Grant No. DUE-0618570. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF. We gratefully thank an anonymous reviewer for extensive helpful remarks.

Date Posted: November 16, 2009.

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