Cladogram Lab Activity

treeoflife

Photo source: Colin Purrington

While it isn’t possible for the average high school biology student to examine real fossils, with a little imagination you can design a really fun “fossil” cladogram activity for your students. Gather some simple household items – kitchen utensils work really well – or instruct your students to bring an item in from home. Break the class into groups of 3 or 4 students and give each group some of the items to examine.

*Note that the more items you give each group, the more difficult the activity becomes. Advanced students can work with between 7-10 items, while less advanced students should be given fewer.

Tell the students to pretend that the items are fossils and that their assignment is to make observations of each “fossil” and use their data to construct a cladogram. Instruct students to look for homologous structures that the fossils share. The structures could be the presence or absence of “teeth”, “appendages”, symmetry, etc.

For example, a salt shaker may have been a filter-feeder with radial symmetry.

saltshaker

Photo source: L. Marie

You can watch this video of some of my students performing this activity to get a better idea of how it can be performed.

Once the students have collected all of their data, they should create a cladogram. Students may feel frustrated initially because it will be difficult to place all of the organisms on the cladogram. Emphasize to students that for this exercise there may not be an exact answer and there are a lot of possible placements for the organisms on the cladogram.

You will want to grade the students on the logic behind their reasoning for placing the fossils on the cladagram in the order in which they did. Have the students present their findings to the class and explain their logic behind how they constructed it. If each group examined the same set of items, there is bound to be some differences in how they decided to construct their cladograms. But, this is exciting! Now, the students can debate their conclusions exactly like real scientists do at academic conferences. Again, grade the students on the clarity in which they present their findings and the logic behind their conclusions.

Check out this blog post a different group of my students wrote about this activity.  The post includes one of the cladograms a student group created and their explanation for how they constructed it.  In the post comments you will find more student discussion.

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