University of Alaska Fairbanks
This activity has benefited from input from faculty educators beyond the author through a review and suggestion process.
This review took place as a part of a faculty professional development workshop where groups of faculty reviewed each others' activities and offered feedback and ideas for improvements. To learn more about the process On the Cutting Edge uses for activity review, see http://serc.carleton.edu/NAGTWorkshops/review.html.
This page first made public: May 21, 2009
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A cladogram exercise involving hardware instead of organisms. Many students are familiar with carabiners and find them more interesting than nails and screws (the example I based this on). Using these characters, you can also make a phenogram, which is different than the cladogram.
Undergraduate required course in invertebrate paleontology
Skills and concepts that students must have mastered
How to use the outgroup to recognize primitive features
Definition and significance of "synapomorphy" and "autapomorphy"
How the activity is situated in the course
This is the first of several homework assignments that require the students to construct a cladogram. Later cladograms involve organisms discussed in class.
Content/concepts goals for this activity
outgroups and primitive characters
synapomorphies vs. symplesiomorphies
Higher order thinking skills goals for this activity
using synapomorphies to determine which taxa are most closely related
designing a cladogram to display the relationships among taxa
Optional: Comparison of a cladogram and phenogram based on the same data
Other skills goals for this activity
Description of the activity/assignment
This is the first of several cladogram exercises which require students to determine the relationships among several taxa given a list of characters and an outgroup. Students must then display the results of their analysis on a cladogram. This exercises follows lectures and class discussions on evolutionary taxonomy, phenetics, and cladistics. It is followed by two or three similar assignments that use organisms familiar to the students from laboratory exercises. The exercise allows students to focus on features of a common tool before applying similar techniques to invertebrate organisms. Students have the opportunity to construct their own cladograms and receive feedback from their peers.
Determining whether students have met the goals
The students are required to construct the cladogram, place the taxa at the tips of the appropriate branches, and list the characters at the nodes. We discuss the exercise in class, and students have an opportunity to present competing cladograms and discuss whether or not different diagrams display the information correctly. I collect and review their cladograms and provide additional feedback.
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