March/April 2017 – Vol. 29 No. 6

The Tree Room: A New Online Resource for Teaching Evolutionary Relationships

Posted: Thursday, November 12th, 2015

by Anna Thanukos, Teresa MacDonald, David Heiser, and Robert Ross

Understanding evolutionary trees is important for students because trees visually represent the idea that all life is genealogically linked. This powerful idea, tied to Next Generation Science Standards MS-LS4-2 and HS-LS4-1, is one of those most fundamental concepts that biological evolution offers to explain the biological world. The implication is that any set of species, no matter how distantly related, share common ancestors at some point in evolutionary history. Evolutionary trees are an efficient way to communicate that idea. It turns out, however, that evolutionary trees are not quite as straightforward to interpret as they may at first appear — so where can a teacher turn for a user-friendly introduction to their use in the classroom?

The Tree Room is a new component of UC Berkeley’s renowned Understanding Evolution website. It contains resources both for teachers in K-16 education and for exhibition designers at informal science education venues such as museums, nature centers, zoos, and aquariums. The Tree Room provides user-friendly, accessible information on how to interpret trees, how they are built, and how they are relevant to society. The website starts with a Primer on trees that can help one learn the basics of evolutionary trees.

Lisa White (Assistant Director for Education and Public Programs at the University of California Museum of Paleontology) teaches about reading evolutionary trees.

Lisa White (Assistant Director for Education and Public Programs at the University of California Museum of Paleontology) teaches about reading evolutionary trees.

The origins of the new website emerged from research within the past decade that documents how evolutionary trees are often misunderstood by the public, including our students. For example, commonly students pay most attention to the ordering of taxa along the tips of a tree, without looking carefully at the branching pattern. Students might assume, therefore, that taxa next to each other are necessarily the most closely related. Students might also assume that one side of a tree, often the right side on a tree positioned “upward,” includes taxa that are more “advanced.” Branching patterns of evolutionary trees, however, can be shown in any order and communicate relative recency of splitting of lineages; in fact, branches can be flipped (rotated) and still communicate the same information. The section of the website “Tree misinterpretations” provides many more examples.

The tree on the left may be misinterpreted as showing evolutionary “progress” toward the top of the tree.

The tree on the left may be misinterpreted as showing evolutionary “progress” toward the top of the tree.

A wide variety of evolutionary tree forms are encountered through textbooks, popular media, and elsewhere, increasing the challenge of interpreting them. These designs range from sets of branching lines to graphics that look like actual trees or branching blobs. The Tree Room’s Field Guide explains how to interpret these various tree forms and their features, and ways in which some designs are more accessible than others. Research has shown, for example, that trees with squared corners (picture a tuning fork) are easier to interpret than the diagonal and circular trees that are common in scientific literature. Blobby trees look friendly but tend to be inherently ambiguous, because it’s unclear how exactly the lineages are related to each other.

The “squarish-corner” form of branching tree is easiest to interpret for students among the common forms of evolutionary tree graphics.

The “squarish-corner” form of branching tree is easiest to interpret for students among the common forms of evolutionary tree graphics.

The Field Guide to Trees home screen shows eight categories of evolutionary tree graphics, The “blobby” (lower left) and “tree-like” (left of the circular tree) designs are considered problematic particularly because of the difficulty in identifying branching points. 

The Field Guide to Trees home screen shows eight categories of evolutionary tree graphics, The “blobby” (lower left) and “tree-like” (left of the circular tree) designs are considered problematic particularly because of the difficulty in identifying branching points.

In the “For teachers” part of the site are ideas for incorporating tree-thinking exercises into curricula and a searchable database of dozens of vetted lessons and tools for teaching about trees. These lessons and resources, for grades 6 to 16, can be searched by grade level, keyword, and type (for example, lab activity, article, tutorial, and so on). Under the link “For museums and zoos” are resources written with museum exhibition designers in mind. However, some of these resources, in particular the section called Tips for tree design, may be useful for teachers who want to create new evolutionary tree graphics or modify existing ones for their teaching.

What did T. rex taste like? This web based module explores common ancestry and evolutionary relationships and is one example of lessons that can be found in the searchable database.

What did T. rex taste like? This web based module explores common ancestry and evolutionary relationships and is one example of lessons that can be found in the searchable database.

There’s another reason for students to understand evolutionary trees beyond the fundamental idea of common ancestry. Evolutionary trees are increasingly used to inform new biological research relevant to students’ lives, such as determining the origin and spread of infectious diseases, making crop choices in changing environments, choosing taxa to investigate for new medicines, and understanding the spread of invasive species. Our students may or may not be doing this research for their careers, but it will surely influence their lives and communities.

The Tree Room website was officially launched in May 2015. It was developed through a partnership among the University of California Museum of Paleontology, the University of Kansas Natural History Museum, the Yale Peabody Museum, and the Paleontological Research Institution, with input from a wide variety of evolutionary biologists and science educators. The project was supported with funds from the Institute of Museum and Library Services (grant number LG-26-12-0578-12).

Anna Thanukos develops and writes science education content for the University of California Museum of Paleontology in Berkeley (thanukos@berkeley.edu). Teresa MacDonald runs the education program at the University of Kansas Natural History Museum in Lawrence, Kansas (tmacd@ku.edu), David Heiser runs the education program at the Peabody Museum of Natural History at Yale University in New Haven, CT (david.heiser@yale.edu), and Rob Ross runs the education program at the Paleontological Research Institution in Ithaca, NY (rmr16@cornell.edu).

All images are from the Understanding Evolution website and are used by permission of the University of California at Berkeley.

Written by Guest Contributor

From time to time CSTA receives contributions from guest contributors. The opinions and views expressed by these contributors are not necessarily those of CSTA. By publishing these articles CSTA does not make any endorsements or statements of support of the author or their contribution, either explicit or implicit. All links to outside sources are subject to CSTA’s Disclaimer Policy: http://www.classroomscience.org/disclaimer.

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