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The Power of Cladistics

Originally appears in the Spring 2012 issue

Cladistics is an exciting and powerful tool that challenges students to classify living organisms into groups based on shared characteristics, all of which have a common ancestor.  The process generates a “family tree” diagram that helps interpret evolutionary relationships. Teachers can use the basic principles and methods of cladistics to teach students about taxonomy and evolutionary relationships among living organisms.

The general idea behind cladistics is that members of a group, called a clade, share a common evolutionary history and are more closely related to members in their own group than to other organisms. For example, coyotes and foxes are members of the Canidae Family, which are distinctly different from tigers and lions in the Felidae Family. Felines have retractable claws, shorter digestive systems that are better adapted to a diet of pure meat, and shortened faces with a reduced number of teeth compared to canines. Sometime in the past, the two families diverged from a common ancestor. To visualize the evolutionary relationship between the Felidae and Canidae Families a diagram, called a cladogram, can be developed using information about the two groups of organisms. (See below.) Cladistics is a visually appealing way for students to learn how common characteristics connect groups of organisms and what their ancestral descendents may have looked like.

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Matthew R. Opdyke is an ecology and environmental science professor at Point Park University in Pittsburgh, Pennsylvania. He also organizes community projects that include watershed studies and wetland rehabilitation.