Build a Phylogenetic Tree

In this activity, students learn how to construct a cladogram, a diagram that shows evolutionary relationships based on shared derived characteristics. Using a set of organisms and their traits, students identify synapomorphies (shared derived traits) and automorphies (unique traits), then use this information to build and interpret a cladogram.

• See links for suggested methods and activities.

Cladistics Part 1: Constructing Cladograms - Professor Dave Explains:

AP Biology - Cladogram Practice with Minions - MrGrodskiChemistry:

📄 Constructing a Cladogram - Science Corner: http://biologycorner.com/worksheets/cladogram_construction.html

* Use fossil ages to constrain branching order, showing how time influences cladogram construction.

• Incorporate molecular data (DNA sequences) alongside morphological data for comparison.
• Provide a mixed set of traits with some convergent or lost features to challenge students to think critically.
• Ask students to create their own imaginary organisms with defined traits, then trade and construct cladograms with classmates’ sets.

• If building physical trees with pins, scissors, or wire, supervise tool use and keep work surfaces clear.

• What features are shared derived traits (synapomorphies), and how do they define clades?
• Which traits are unique (automorphies), and how do they help identify individual species but not broader groups?
• How does including an outgroup help identify ancestral versus derived traits?
• Could different interpretations of the data lead to different cladograms? How might scientists resolve disagreements?
• How does constructing cladograms help us understand evolutionary relationships and common ancestry?