Academic journal article The American Biology Teacher

Using Pipe Cleaners to Bring the Tree of Life to Life

Academic journal article The American Biology Teacher

Using Pipe Cleaners to Bring the Tree of Life to Life

Article excerpt

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Many students, teachers, and even some scientists struggle to make sense of phylogenetic trees (Baum et al., 2005), which are commonly used in both textbooks and classroom instruction. Rather than ignore student struggles, it is time to address the challenge of "tree thinking" by developing ways to help students learn how to read these diagrams. I created a manipulative model that pushes students to explore phylogenetic trees and think more deeply about evolutionary relationships. This simple, inexpensive pipe-cleaner model gives students a 3D experience of what is typically represented in two dimensions. Students manipulate the tree to rotate branches, compare topologies, map complete lineages, identify informative phylogenetic features, and examine the effects of superficial structural changes. For example, when this model was used in a college biology course, one student said that "the pipe cleaners allow us to see how manipulating the tree by twisting and straightening does nothing to the tree's meaning, just its appearance." Another student had struggled with how two rotated trees could illustrate the same relationships. She stated, "I had trouble imagining the 'rotation' of the branches in my head, and this provided a physical rotation that I could see."

You will need five pipe cleaners of different colors for each tree. Here, I use pink, purple, green, blue, and orange to represent each element of a single tree or lineage. There are four steps to building the model. (1) Gather the five pipe cleaners together so that they are flush at each end. …

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