MCAT Biology Question 173: Answer and Explanation

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Question: 173

8. Which of the following statements is FALSE based on Darwin's theory of evolution?

  • A. Natural selection is the driving force for evolution.
  • B. Favorable genetic variations become more and more common in individuals throughout their lives.
  • C. Natural selection can drive organisms living in groups to ultimately become distinct species.
  • D. Fitness is measured by reproductive success.

Correct Answer: B

Explanation:

Darwin's theory of natural selection argues that chance variations between organisms can help certain organisms survive to reproductive age and produce many offspring, transmitting their variations to the next generation. Thus, natural selection would drive the process of evolution forward, enabling the survival of characteristics that impart an advantage in the environment, eliminating choice (A). In Darwin's theory, fitness is measured in terms of reproductive success, as choice (D) states. Through natural selection, organisms may be separated in groups depending on environmental pressures, and these groups can eventually separate to the point of becoming distinct species, eliminating choice (C). Choice (B) is the correct answer because the theory of natural selection applies to a population of organisms, not to a particular individual. As such, favorable genetic variations become more and more common from generation to generation, not during the lifetime of an individual.

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