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EVOLUTIONTree Thinking

Summer Institute 2014 UCR, Riverside

Sofia, Blaire, Jinghua, Kelsey, Lauren, Brad, Beth, Kris“Education Evolves”

Audience: Introductory Biology

• Prerequisite topics:– Scientific Method– Natural Selection – Descent with modification

Learning Goal

• Students Should be Able to Use Phylogenetic

Trees to Understand Evolution

• Today’s Teachable Tidbit: Tree Thinking

Learning OutcomesStudents should be able to:

• Apply the descriptive terminology associated with phylogenetic trees• Use shared derived characters to build phylogenetic trees • Understand difference between homology and convergence• Identify common ancestors• Interpret a given phylogenetic tree • Use the tree to make an evolutionary inference

Non-content learning outcomes:• Communicate science• Collaborate effectively• Think creatively

Previous lesson: Anatomy of a Tree 1. Think-Pair-Share or homework assignment:Add the following terms to the blank tree:– Branch (Label only)– Node (Label and count)– Tip (Label and count)– Clade (Label and count)

Character Mapping

Character Mapping

In pairs:1. On your handout, write down each

morphological character on the tree at least once.

Report Out

Evolution of Morphology

Evolution of MorphologyIn groups for your assigned clade:• Identify the location on the phylogeny of the

most recent common ancestor• Then, from your stack of characters…– Find those that define your clade

• Of the remaining characters…– Find those that are features of the common ancestor

Class Consensus: Complete Summary chart

Group Work Summary

• Shared Derived = characters that define your clade

• Shared Ancestral = other characters they share

photos

Put it all Together

• Convergence: a character that evolved independently multiple times in different branches

• Why do you think convergence is evidence for evolution by natural selection?

• Discussion and report back.

Final Reflection

• One minute writing assignment: Can you think of other groups not shown here that also evolved wings for flight? How do you know that this is due to convergent evolution?

• Write your name on it. • Turn it in on your way out.