Understanding Cladistics

Activity for Grades 5–8

Introduction

At the American Museum of Natural History, scientists use a method called cladistics to group animals. They look for unique features, such as a hole in the hip socket, that the animals share. Animals with like features are grouped together. A chart, called a cladogram, shows these relationships. Using cladistics, scientists can reconstruct genealogical relationships and can show how animals are linked to one another through a long and complex history of evolutionary changes.

Objective

In this activity, students will explore cladistics and create a cladogram of their own.

Materials

• A penny, nickel, dime, and quarter for each pair of students
• 6-8 dinosaurs pictures duplicated for each group, downloadable from amnh.org/resources/rfl/pdf/dino_16_illustrations.pdf
• Procedure

1. Write lion, elephant, zebra, kangaroo, koala, buffalo, raccoon, and alligator. Ask students how the animals are related and what might be a good way of grouping them into sets and subsets. Discuss students responses.

2. Explain to students that scientists use a method called cladistics to determine evolutionary relationships among animals. They look for features that animals share, such as four limbs, hooves, or a hole in the hip socket. Animals with like features are grouped together. Scientists make a chart called a cladogram to show these relationships.

3. Tell students that they will examine the features of various coins to determine how they are related. Remind students that cladistics is used to determine relationships among organisms, and not necessarily objects. The exercise they are about to do will introduce them to how cladistics works. Have students work in pairs. Distribute Understanding Cladistics to students. Have them complete the activity and compare their cladograms. Discuss how they arrived at their conclusions and any differences among the cladograms.

4. Duplicate and distribute illustrations of six to eight dinosaurs. Ask students to work in groups to classify the dinosaurs according to features they identify. Have groups share their findings.