7.1 Introduction to Natural Selection (U1) |
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Viewing Guide & Questions:
Learn about natural selection and what the process of evolution tells us about the diversity and unity of life.
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🐹Rock Pocket Mice: A Case Study in Natural Selection🏜️
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Rock pocket mice (Chaetodipus intermedius) provide an intriguing example of natural selection as a major mechanism of evolution. These small rodents live in the southwestern United States, occupying habitats that include light-colored sandy deserts and dark rock formations created by ancient lava flows. Their fur color, which ranges from light tan to black, plays a key role in their survival. Rock pocket mice are preyed upon by a variety of visual predators including; owls, hawks, coyotes, and snakes.
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Fig 1. Rock pocket mouse. |
Fig 2. Basalt is a dark colored igneous rock. |
Darwin’s theory of natural selection states that organisms compete for limited resources, and those with favorable phenotypes (traits) are more likely to survive and reproduce. Rock pocket mice face strong predation pressure from visual hunters, including snakes, coyotes, and raptors. In areas with light-colored sand, mice with light fur blend into their surroundings, making them less visible to predators. Conversely, in areas with dark volcanic rock, mice with darker fur are better camouflaged.
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Conclusion:
Rock pocket mice demonstrate the concept of evolutionary fitness, which is measured by reproductive success. As natural selection acts on the population, mice with better camouflage are more likely to avoid predation, survive, and reproduce. Over generations, the genes responsible for camouflage (crypsis) increase in frequency within the population, illustrating how natural selection shapes evolutionary change over time. |
Fig 3. Fur color variation in rock pocket mice. |
🐕Retrieval Practice📝 - Answer these questions to the best of your ability without using help.
7.1 Intro to Natural Selection Quiz
Question 1 of 8
🎧💻Click, Watch, Listen, and Learn!
Dive deeper with simulations, cool lab videos, and chill science podcasts—because biology is more than just notes😀
Dive deeper with simulations, cool lab videos, and chill science podcasts—because biology is more than just notes😀
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Explore: The Mouse Hunter simulation explores how camouflage helps animals such as rock pocket mice avoid predation. Compare the average survival times of light colored mice when hunted by a owl on different colored ground.
An online version of Mouse Hunter is also available which allows users to play the role of a predator trying to catch their prey as quickly as they possibly can. Handouts for the classroom manipulative model and online simulation are available in the instructor materials for this unit is available in the Unit 1 calendar document posted on the Unit 1 landing page. |
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Mouse Hunter was originally created by Evo-Ed of Michigan State University.
© 2025 Copyright EvoEd. All rights reserved.
© 2025 Copyright EvoEd. All rights reserved.
Short Wave: Rafting Iguanas
Check out this podcast episode that has an amazing connection to Unit 1: Survivor-American Southwest!
Check out this podcast episode that has an amazing connection to Unit 1: Survivor-American Southwest!
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🎧Short Wave | 04/01/25
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Where did the Fijian iguanas come from ... and how? For decades, it's been a scientific mystery. Most iguanas are indigenous to the Americas; however, native Fijian iguanas, call an island nearly 5000 miles away from their closest relatives in the South Pacific home. Thanks to genome mapping, researchers think they've found out how...
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