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Ch. 22 - Evolution by Natural Selection
Freeman - Biological Science 7th Edition
Freeman7th EditionBiological ScienceISBN: 9783584863285Not the one you use?Change textbook
All textbooksFreeman 7th EditionCh. 22 - Evolution by Natural SelectionProblem 15
Chapter 22, Problem 15

The researchers placed white and brown mouse models both in abandoned fields on the mainland (dark soil) and on sand dunes on the islands (light soil) and then measured the percentage of models that were attacked by predators. What is the take-home message of the data? Do the data support or reject the hypothesis that mouse color is adaptive? Bar graph showing predator attacks on white and brown mouse models in different environments.

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1
Observe the graph and note the two different environments: Mainland (dark soil) and Sand dunes (light soil).
Identify the two types of mouse models used in the experiment: white and brown.
Compare the proportion of attacks on white and brown mouse models in the Mainland environment. Note that the white models have a higher proportion of attacks compared to the brown models.
Compare the proportion of attacks on white and brown mouse models in the Sand dunes environment. Note that the brown models have a higher proportion of attacks compared to the white models.
Conclude that the data supports the hypothesis that mouse color is adaptive, as the color that blends in with the environment (brown on dark soil and white on light soil) experiences fewer attacks by predators.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Natural Selection

Natural selection is a fundamental mechanism of evolution where organisms better adapted to their environment tend to survive and produce more offspring. In this context, the color of the mouse models may influence their visibility to predators, affecting their survival rates. The data can help determine if certain traits, like color, provide a survival advantage in specific environments.
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Natural Selection

Camouflage

Camouflage is a survival strategy that allows an organism to avoid detection by predators. In this experiment, the white and brown mouse models represent different camouflage strategies against the dark soil of the mainland and the light sand dunes. The effectiveness of their coloration in these environments can indicate whether their coloration is adaptive.
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Introduction to Evolution and Natual Selection Example 1

Hypothesis Testing

Hypothesis testing is a scientific method used to determine the validity of a proposed explanation for a phenomenon. In this case, the hypothesis suggests that mouse color is adaptive. By analyzing the data on predator attacks, researchers can support or reject this hypothesis based on the observed outcomes in different environments.
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Related Practice
Textbook Question

What is an evolutionary adaptation?

a. A trait that improves the fitness of its bearer, compared with individuals without the trait

b. A trait that changes in response to environmental influences within the individual's lifetime

c. The ability of an individual to adjust to its environment

d. A trait that an individual wants so that it can survive

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Textbook Question

Most mice living on the mainland of Florida are brown, but the mice that live on the sand dunes of the barrier islands have white fur. The differences in color are heritable, determined by genes such as MC1R. It is intuitive that the light color of beach-dwelling mice is an adaptation for blending into their environment—and thus evading predators. Apply Darwin's four postulates to a population of mice living on sand dunes in coastal Florida.

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Textbook Question
A team led by evolutionary biologist Hopi Hoekstra set out to test the hypothesis that predators are an agent of natural selection on mouse color. They made 250 plasticine models of mice that were alike in every way except that half were painted white and half were painted brown. Suggest one advantage and one disadvantage of using model mice instead of real mice in this experiment.
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