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Classroom Resource
Color Variation Over Time in Rock Pocket Mouse Populations


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.

Curriculum Connections:

NGSS (April 2013)
MS-LS2-1, MS-LS2-2, MS-LS4-4, MS-LS4-6, MS-ESS2-2, MS- LS2.C, MS- LS4.B, MS- LS4.C, HS-LS2-2, HS-LS2-6, HS-LS3-3, HS-LS4-2, HS-LS4-4, HS-LS4-5, HS.LS2.C, HS.LS4.B, HS.LS4.C

Common Core (2010)
CCSS.ELA-Literacy.RST.9-10.3, CCSS.ELA-Literacy.RST.9-10.4, CCSS.ELA-Literacy.RST.9-10.7, CCSS.Math.Practice.MP.2, CCSS.Math.Practice.MP.3, CCSS.Math.Practice.MP.5, CCSS.WHST.9-12.1

AP Biology (2012–13)
1.A.1, 1.A.2, 1.A.4, 1.C.3, 4.B.3, 4.C.3

IB Biology (2009)
5.4, D.2, G.1

Supporting Materials (7)

Short Film
The rock pocket mouse is a living example of Darwin’s process of natural selection.
Interactive Video
Embedded quiz modules test students’ understanding as they watch the short film on the rock pocket mouse—a living example of Darwin’s process of natural selection.
Classroom Resource
An activity in which students analyze amino acid data and draw conclusions about the evolution of coat color phenotypes in different rock pocket mouse populations.
Classroom Resource
An advanced lesson that requires students to analyze partial DNA sequences of the Mc1r gene and identify the effects of mutations on the MC1R protein pathway.
Classroom Resource
A lesson that uses real rock pocket mouse data collected by Dr. Michael Nachman and his colleagues to illustrate the Hardy-Weinberg principle.
Classroom Resource
A lesson that requires students to transcribe and translate portions of the wild-type and mutant rock pocket mouse Mc1r genes and compare sequences to identify the locations and types of mutations responsible for the coat color variation described in the film.
Film Guides
The following classroom-ready resources complement The Making of the Fittest: Natural Selection and Adaptation, which describes the physical and genetic evolutionary changes in rock pocket mouse populations.

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