A data collection and analysis lesson that examines selection for coat color in pocket mouse populations on different color substrates over time.
Appropriate for: middle school life science, high school biology (all levels)
This activity serves as an extension to the HHMI short film The Making of the Fittest: Natural Selection and Adaptation and a means of reinforcing the concepts of variation and natural selection.
The tiny rock pocket mouse weighs just 15 grams, about as much as a handful of paperclips. A typical rock pocket mouse is just about 170 millimeters long from nose to rump, shorter than an average pencil. Their impact on science, however, has been enormous. What’s so special about these little mice?
Populations of rock pocket mice are found all over the Sonoran Desert in the southwestern United States. There are two common varieties—a light-colored variety and a dark-colored variety. Similarly, there are two major colors of substrate, or surface materials, that make up the desert floor. Most of the landscape consists of light-colored sand and rock. Here and there, however, separated by several kilometers of light-colored substrate, are patches of dark volcanic rocks that formed from cooling lava flows.