Evolution of Camouflage
(Video)
Evolution of the Eye
(Video)
Finch Beak Data Sheet
(Document)
Life's Grand Design
(Document)
The Mating Game
(Interactive)
Microbe Clock
(Interactive)
A Mutation Story
(Video)
The Red Queen
(Video)
Sex and the Single Guppy
(Interactive)
Tale of the Peacock
(Video)
In this three-part lesson, students learn about natural selection, the mechanism that drives evolution. They begin by discussing the evolution of the eye and how even a complex organ can evolve through natural selection. Then they divide into groups to learn about genetic variation, adaptation, and sexual selection and report their findings back to the class. Finally, students analyze data to determine how the beak length of Galápagos finches evolves according to environmental factors.
1. Show the Evolution of the Eye video and have students read the corresponding backgrounder.
2. Share with your class the following quote from Darwin's On the Origin of Species.
Organs of Extreme Perfection and Complication
To suppose that the eye with all its inimitable contrivances for
adjusting the focus to different distances, for admitting different
amounts of light, and for the correction of spherical and chromatic
aberration, could have been formed by natural selection, seems,
I freely confess, absurd in the highest degree. When it was
first said that the Sun stood still and the world turned round,
the common sense of mankind declared the doctrine false; but the
old saying of Vox populi, vox Dei, as every philosopher
knows, cannot be trusted in science. Reason tells me, that if
numerous gradations from a simple and imperfect eye to one
complex and perfect can be shown to exist, each grade being useful
to its possessor, as is certainly the case; if further, the eye
ever varies and the variations be inherited, as is likewise
certainly the case; and if such variations should be useful to
any animal under changing conditions of life, then the difficulty
of believing that a perfect and complex eye could be formed by
natural selection, though insuperable by our imagination,
should not be considered as subversive of the theory.
From Charles Darwin, On the The Origin of Species
(New York: The Modern Library, 1993), 227-228.
3. Discuss with your class the following topics:
4. If time allows, have students visit the Life's Grand Design Web feature. This illustrated essay by Ken Miller discusses how a complex organism such as the eye could evolve through natural selection and refutes the "intelligent design" concept. This detailed essay provides a good follow-up assignment after the in-class discussion.
5. Divide the class into three groups. Assign each group a different component of natural selection: genetic variation, adaptation, and sexual selection. (If you have only one computer in your classroom, keep the class as one group and choose one video from each topic to show and discuss.)
6. Copy the Finch Beak Data Sheet for your class. Read the backgrounder in class and talk about the importance of the Grants' work. Ask students to identify specific data (from the data sheet) that supports each of the following claims:
7. Discuss the following questions as a class:
8. If time allows, expand your discussion on finches to include the topic of adaptive radiation. Print out the Adaptive Radiation: Darwin's Finches graphic. Talk about how environmental influences on the Galápagos Islands led to the evolution of thirteen distinct species of finches.
9. Have students visit the Sex and the Single Guppy Web feature and ask them the following questions: