Evolution of Camouflage
(Video)
Floral Arrangements
(Video)
Sex and the Single Guppy
(Interactive)
Tale of the Peacock
(Video)
In this lesson, students learn about natural selection, the mechanism that drives evolution. They begin by viewing short videos about the evolution of physical and behavioral adaptations in various organisms. This is followed by a discussion of the natural selection mechanism, which has, over many generations, given rise to these and other extraordinary traits. Students then watch a video about peacocks that explores the interplay between two evolutionary imperatives: the need to survive and the need to reproduce. Lastly, students pair up to perform experiments with simulated populations of guppies, another species whose evolution is driven by the interplay between the forces of predation and sexual selection.
Read the background essay that accompanies each resource to gain information that will help you facilitate class discussion.
1. Show the Hummingbird Species in the Transitional Zones video and discuss the following:
2. Show the Evolution of Camouflage video and discuss the following:
3. Show the Floral Arrangements video and discuss the following:
4. Show the Tale of the Peacock video and discuss the following:
5. Lead students through the introductory screen and the section titled "Read about Endler's discovery" of the Sex and the Single Guppy Web activity. During this time, remind students that scientific research begins with systematic observations, followed by the formulation of a hypothesis that explains the observations, and then experimental testing of the hypothesis. Explain to students that they are going to follow these same steps in search of a scientific explanation for the differences in coloration among different guppy populations.
6. After reading and discussing the two introductory sections listed above, ask students to work in pairs and begin their investigation of guppies and their habitat. One student should use the computer while the other takes notes on what they both observe. Recommend that students spend time clicking on the pools on the "Endler's discovery" screen to learn more about the conditions in each. Students can also spend time in the Guppy Gallery to learn more about the guppies, their predators, and real-life stream habitats. At the end of the observation period, students should consider the given hypotheses -- and any they may have come up with on their own -- and choose the one they think best explains the differences in guppy coloration. Ask students to record their chosen hypothesis.
7. When students are finished with their preliminary observations, tell them to trade places. Ask students to set up their first experimental simulation by selecting the distribution of each guppy color type as well as the number and type of predators that their experimental pool will have. Recommend that students run the simulation for 10 to 15 guppy generations to yield observable results. Then ask students to run three or four more simulations and experiment with different sets of variables to test their hypothesis. Students should record and/or print out their results.
8. Following the experiments, have students consider the following questions and present their answers to the class.
Have students discuss the following: