This resource describes the phylogenetic tree and how it represents interrelatedness of species descended from a common ancestor. The narrated animation defines the basic vocabulary and illustrates the concepts with simple diagram and animation and explains how to read or interpret a phylogenetic tree.
Type of Material:
Animation with narration.
Homework, lecture and lab supplement.
Web browser with Adobe Flash.
Identify Major Learning Goals:
None specifically stated, but this resource is part of the materials for Chapter 21 of the Raven Biology text, which has learning goals. Several of the goals apply to the animation. Users will learn:
How to read or interpret a phylogenetic tree
Definitions of terms associated with reading and constructing cladograms and phylogenetic trees
Target Student Population:
High school or lower division biology students.
Prerequisite Knowledge or Skills:
There are no prerequisites for this site although some knowledge of basic biology will help in understanding what is presented.
Evaluation and Observation
All information is accurate
The level is very basic and so this would be useful to students with no background in biology or evolution
The sequence of topic presentation is logical and well-organized • The narration is clearly enunciated
some good examples given
The description of what a tree is, is very rudimentary and could be expanded for students who have no idea how to interpret trees
No explanation of how trees are created is given
No indication that multiple trees are possible is given, when the animation discusses how to determine the likelihood that a tree is accurate
Potential Effectiveness as a Teaching Tool
This animation could serve as an introduction to a more detailed explanation of evolutionary trees
The blend of text, audio, and images makes the material interesting
The material is visual and so is effective and engaging
Ease of Use for Both Students and Faculty
The controls are easy to use and work on both Mac and PC
Information is well organized and easy to understand
There is way to toggle text and audio so users can either one or both
The pause button and slider make it easy to navigate
There is no full screen function. Having this feature would make the animation more useful for instructors to use in class
Other Issues and Comments:
This animation is a very basic introduction to phylogenetic trees. As such, it leaves out most of the details and nuances of interpreting trees. However, students have a typical series of misunderstandings about how to interpret these visual representations of evolution. The animation could address a few of these rather easily. For example a time axis on the first tree would be helpful, as would a slightly more detailed explanation of what "the branches connect the common ancestors" means. Trees are never described as hypotheses of relationships, to be tested by the evidence, but rather as constructs based on identifying synapomorphies accurately, (which is the reverse of how trees are constucted). The discussion at the end of eukaryote relationships and the demise of protista is confusing.