Creating Cladograms

Groups: You can choose a partner for this activity

Goals:

• • To practice reading cladograms

  • To learn the concept of parsimony by using it to create a cladogram

  • To learn the concepts of apomorphies, plesiomorphies, and synapomorphies by applying them to a scenario

Procedure:

• 1. Choose a partner. You do not need to be in your number or color group.

  2. Choose one partner to be the recorder for the first part of the activity. That person should write your full names on a piece of paper.

  3. You are chief science office on the spaceship Venture. You have discovered a planet on which there is a group of animals you call Fuzzballs, because they are mostly small and hairy (unlike other animals, represented by the outgroup in the figure, which are mostly leather-skinned and large). Your job is to classify the species pictured into the most parsimonious possible cladogram. Draw the cladogram on the sheet of paper (you can just use the letters, you don't need to draw the animals).

  4. Once you have drawn your cladogram, switch recorders (the other partner should write for a while), and answer the following questions:

     1. 1. In what order did the major physical traits of Fuzzballs evolve (that is, which evolved first, second, etc.)?

        2. Which animals form clades in your cladogram? Circle all of the different clades (or write the letters here).

        3. What are the most primitive traits (pleisiomorphies) among the Fuzzballs?

        4. Name three shared, derived traits (synapomorphies) among the Fuzzballs.

  5. Be prepared to participate in group discussion about your findings.

Take-Home Message:

• 1. Simple cladograms are created by assuming the most parsimonious explanation for the evolution of physical traits.

  2. The members of a clade, and what counts as a pleisiomorphy or an apomorphy, depends on the scale of analysis.

  3. Cladograms are an important tool for representing evolutionary relationships between living organisms.

  4. Cladograms also illustrate the course of evolution within a taxonomic group.

Reflection:

You may reflect on any aspect of this activity. If you are not sure where to start, try answering these questions: Did applying the concepts help you to understand the differences between pleisiomorphies, synapomorphies, and apomorphies? Why or why not? What questions do you still have about these concepts that you would like clarified?