This lesson from HHMI BioInteractive is based on the classic study of the evolution of fur color in rock pocket mouse populations. It supports the short film, “The Making of the Fittest: Natural Selection and Adaptation.” The creator uses the evolution of the fur color of the rock pocket mouse as the phenomenon for this activity and uses it to address three of the four mechanisms that contribute to population adaptation through natural selection. Students summarize the evidence for evolution by natural selection presented in the film and in figures from a scientific paper. The goal is to understand how to collect and analyze evidence that supports each of the major conditions for evolution by natural selection in order to develop a full explanation for how populations change over time. This activity includes: educator materials, student handout, additional evidence and an explanation table.