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: Jul 24, 2009
Skills and concepts that students must have mastered
How the activity is situated in the course
Content/concepts goals for this activity
I would like them to appreciate that there are different ways of coding characters, and that these ways have effects on phylogenetic analysis.
I would like students to be able to visualize coding strategies – i.e., schools of thought on how morphology should be coded.
Higher order thinking skills goals for this activity
I would like students to develop the identify the assumptions implicit in phylogenetic analysis.
Other skills goals for this activity
Description of the activity/assignment
This activity focuses on character coding, specifically about how different coding strategies can affect analysis. In this exercise we will try to look at different coding strategies by considering the simple shapes below.
(1) What is a character, and what qualities do characters have?
(2) Given the 'morphology' depicted above, what features vary?
(3) Given the variation you identified, come up with as many character codings as you can; i.e., different ways that this variation can be coded into characters.
(4) For each of the coding strategies you come up with in question 3, identify its assumptions, limitations, and strengths.
(5) Identify your preferred coding strategy and defend your choice.
Students asked to define what a character is and to discuss what they 'require', and then to come up with an exhaustive list of coding strategies for the sample morphology. They are then asked to list assumptions/limitations of each strategy.
Determining whether students have met the goals
Download teaching materials and tips
- Activity Description/Assignment:
- Instructors Notes: The shapes are adapted from Pleijel, F. 1995. 'On character coding for phylogeny reconstruction'. Cladistics 11:309-315. Pleijel includes a good discussion of character coding strategy.
- Solution Set:Character coding (Acrobat (PDF) 17kB Jul24 09)