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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 12
Chapter 22, Problem 12

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

Verified step by step guidance
1
Understand the concept of evolutionary adaptation: It refers to a heritable trait that increases the fitness of an organism, meaning it enhances the organism's ability to survive and reproduce in its environment.
Consider the context of the problem: The beach-dwelling mice have developed white fur, which is a heritable trait. This trait likely provides a survival advantage by helping them blend into their sandy environment, thus avoiding predators.
Evaluate each option: a) A trait that improves the fitness of its bearer, compared with individuals without the trait, aligns with the definition of an evolutionary adaptation. b) A trait that changes in response to environmental influences within the individual's lifetime is more akin to acclimatization, not adaptation. c) The ability of an individual to adjust to its environment describes phenotypic plasticity, not a genetic adaptation. d) A trait that an individual wants so that it can survive is not a scientific explanation for adaptation.
Identify the correct option: Based on the definition and context, option a) is the correct description of an evolutionary adaptation.
Conclude with the understanding that evolutionary adaptations are traits that have been naturally selected because they confer a survival or reproductive advantage in a specific environment.

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Key Concepts

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

Evolutionary Adaptation

An evolutionary adaptation is a heritable trait that enhances the fitness of an organism, allowing it to survive and reproduce more effectively in its environment. This trait is developed over generations through natural selection, where advantageous traits become more common in a population. In the context of the mice, the white fur is an adaptation that helps them blend into the sandy environment, reducing predation.
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Adaptive Radiation

Natural Selection

Natural selection is the process by which organisms with traits better suited to their environment tend to survive and reproduce at higher rates than others. This mechanism drives the evolution of species, as advantageous traits become more prevalent over generations. In the case of the Florida mice, natural selection favors those with fur color that provides camouflage, enhancing their survival against predators.
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Natural Selection

Genetic Heritability

Genetic heritability refers to the proportion of variation in a trait that can be attributed to genetic differences among individuals in a population. Traits like fur color in mice are passed down from parents to offspring through genes, such as MC1R, which influence pigmentation. Heritability ensures that beneficial adaptations, like the white fur of beach-dwelling mice, are transmitted across generations.
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Genetic Drift Example 2
Related Practice
Textbook Question

Coral reefs are biodiverse ecosystems that provide food, income, coastal protection, and many other services to millions of people. Yet coral reefs are under threat from human impacts such as climate change—many corals cannot tolerate the warming ocean water and have suffered massive 'bleaching' events, which can be fatal. Researchers have discovered that some corals have the capacity to acclimatize to warmer water, while other corals do not. The researchers fear that because corals are long-lived colonial animals and thus evolve slowly, they may not be able to adapt to global warming fast enough to avoid extinction. Explain how the difference between acclimatize and adapt is important to the fate of corals.

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Textbook Question

The geneticist James Crow wrote that successful scientific theories have the following characteristics: (1) They explain otherwise puzzling observations; (2) they provide connections between otherwise disparate observations; (3) they make predictions that can be tested; and (4) they are heuristic, meaning that they open up new avenues of theory and experimentation. Crow added two other elements of scientific theories that he considered important on a personal, emotional level: (5) They should be elegant, in the sense of being simple and powerful; and (6) they should have an element of surprise. How well does the theory of evolution by natural selection fulfill these six criteria?

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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.Compare how evolution by inheritance of acquired characters and the theory of evolution by natural selection would explain the observation of white mice living primarily on light soil and brown mice living primarily on dark soil.
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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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Textbook Question
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?

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