Using Pipe Cleaners to Bring the Tree of Life to LifeAuthor(s): Kristy L. HalversonSource: The American Biology Teacher, Vol. 72, No. 4 (April 2010), pp. 223-224Published by: University of California Press on behalf of the National Association of Biology TeachersStable URL: http://www.jstor.org/stable/10.1525/abt.2010.72.4.4 .Accessed: 29/03/2011 16:42

Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unlessyou have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and youmay use content in the JSTOR archive only for your personal, non-commercial use.

Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at .http://www.jstor.org/action/showPublisher?publisherCode=ucal. .

Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printedpage of such transmission.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact support@jstor.org.

University of California Press and National Association of Biology Teachers are collaborating with JSTOR todigitize, preserve and extend access to The American Biology Teacher.

http://www.jstor.org

Image: © Js10053 | Dreamstime.com

The american biology Teacher Using PiPe cleaners To bring The Tree of life To life 223

q u i c k f i x Using Pipe Cleaners to Bring the Tree of Life to Life

K r i s t y L . H a Lv e r s o n

AbstrAct

Phylogenetic trees, such as the “Tree of Life,” are commonly found in biology textbooks and are often used in teaching. Because students often struggle to understand these dia-grams, I developed a simple, inexpensive classroom model. Made of pipe cleaners, it is easily manipulated to rotate branches, compare topologies, map complete lineages, identify informative phylogenetic features, and examine the effects of superficial struc-tural changes.

Key Words: Biology; cladogram; evolution; phylogenetics; tree thinking.

Many students, teachers, and even some sci-entists struggle to make sense of phylogenetic trees (Baum et al., 2005), which are commonly used in both textbooks and classroom instruc-tion. 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 phyloge-netic trees and think more deeply about evolu-tionary relationships. This simple, inexpensive pipe-cleaner model gives students a 3D experi-ence 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. (2) Twist them together at one end, using about 2 inches of the bundle. (3) Take the other end of the pink pipe cleaner and wrap it around the others once. Then twist the remaining pipe

cleaners together for another 1.5 to 2 inches. Repeat this step with the remaining pipe cleaners until they have all been isolated in the following order: pink, purple, green, blue, orange. (4) Bend the pipe cleaners 90° at each point of intersection and another 90° at each halfway point (see Figure 1).

This model works well in addressing the challenge of tree thinking because (1) it uses color to help identify complete lineages; (2) it is bendable, so that it can be transformed into multiple styles of trees; (3) to alter relationships, students must deconstruct and rebuild the model – much like a real tree; (4) students can use addi-

tional pipe cleaners to incorporate additional species and information; and (5) the model can be modified easily by using a hole punch to add taxa to the tips to provide a more con-crete learning tool. This model has been used at high school and postsecondary levels to help students read trees, build them, and under-stand what they represent.

I created a manipulative

model that pushes

students to…think more

deeply about evolutionary

relationships.

The American Biology Teacher, Vol. 72, no. 4, pages 223–224. issn 0002-7685, electronic issn 1938–4211. ©2010 by national association of biology Teachers. all rights reserved. request permission to photocopy or reproduce article content at the University of california Press’s rights and Permissions Web site at www.ucpressjournals.com/reprintinfo.asp. Doi: 10.1525/abt.2010.72.4.4

Figure 1. Sample pipe-cleaner phylogenetic tree with the “green” lineage identified.

224 The american biology Teacher VolUme 72, no. 4, aPril 2010

Referencesbaum, D.a., smith, s.D. & Donovan, s.s.s. (2005). The tree-thinking challenge.

Science, 310, 979–980.

KrisTy l. halVerson is assistant Professor of biological sciences at the University of southern mississippi, 118 college Dr. #5018, hattiesburg, ms 39406; e-mail: kristy.halverson@usm.edu.