Jennifer A. Collins: PaleoBio

Anolis Lizards of the Greater Antilles: Using phylogeny to test hypotheses
Written by Jennifer A. Collins
Jen's Other Lessons ~ Education Home

Lesson Overview: Students "take a trip" to the Greater Antilles to figure out how the Anolis lizards on the islands might have evolved. They begin by observing the body structures and habitat of different species, then plot this data on a map of the islands to look for patterns in their distribution. From the patterns they observe, students develop alternative hypotheses about how these lizards colonized the islands and evolved. To test their hypotheses, they are given a phylogeny which they color code according to their previous data. By combining both types of data, students make a final hypothesis about how they think the lizards colonized the islands.

The objectives of this lesson are to teach students how to:

Identify patterns in biological data, such as morphological characters (physical features), habitat, and geographical distribution.

Form multiple evolutionary hypotheses to explain the patterns they observe.

Test their hypotheses using a provided phylogenetic tree/cladogram.

Terms: distribution, speciation, phylogenetic tree, evolution

Prerequisites: Before beginning this lesson, students should:

understand that phylogenetic trees (cladograms) are hypotheses of how a set of organisms are related,

be able to read a phylogenetic tree (cladogram),

understand that evolution is change through time. Changes occur through the inheritance of features over many generations.

Time: 70-90 minutes

Grouping: groups of 2-4 students

Background information: Under development

Materials:
All of the following are in PDF format.

Student Directions

Student Questions | Question Answer Key

Student Map of the Greater Antilles | Map Key

Anoli Lizard Icons | Anolis Lizard Data Table

Anolis Lizard Phylogenetic Tree | Anolis Lizard Phylogenetic Tree Key

Possible Phylogenetic Tree Hypotheses

Colored pencils or pens

Glue or tape

Scissors

Various images and background information about Anolis lizards.

Optional: "Darwins Lizards" by Jonathan B. Losos and Kevin de Queiroz in the Natural History Magazine 12/97-1/98.

Procedure:
1.Pass out all materials EXCEPT the Anolis Lizard Phylogenetic Tree. Pass out any additional background information about Anolis lizards.

2.Read the introduction and Part I of the Student Directions outloud. Show students pictures of the lizards and a map of the islands from a globe or atlas. Discuss where the islands are located. Have students find their map. Explain that the large trees that they see represent the habitats that the lizards live in and it is where they will eventually plot their data. When coloring the islands, students should select a different color for each island. Students should answer questions 1 and 2 before beginning part II.

3.Read Part II of the Student Directions. Have students look closely at the data table and the lizard images. They should be able to identify and understand the different body shapes, habitats, and islands so that they can answer questions 3-4. Before students color their lizards be sure they understand that they must select a different color to represent each body type. When they cut out each lizard, they must place it on the correct island, AND at the right location on the tree. They should complete questions 5-9. Encourage students to develop multiple hypotheses for the patterns they see. Students may need additional help to complete this. It would probably be very helpful to have students share their responses to these questions before moving to Part III.

4.Read Part III of the Student Directions with the students. Before beginning this section it might be valuable to have a class discussion about what some possible phylogenetic trees would look like that would support different hypotheses (see Possible Phylogenetic Tree Hypotheses). You could begin by discussing the kind of phylogenetic pattern you would see that would support the hypothesis that all lizards on the same island are most closely related versus the hypothesis that all the lizards with the same morphology are most closely related. Once students are ready, pass out the Anolis Lizard Phylogenetic Tree. Students should color code the phylogenetic tree according to the directions, then look very carefully at the patterns that appear. Students should answer remaining questions then share their findings with the class.