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Difficulty: MediumLamarck's Theory of Evolution

In an experiment designed to test a fundamental principle of evolution, a scientist cut off the tails of mice for twenty-two consecutive generations. Despite this continuous physical modification, all offspring in the twenty-third generation were born with tails of normal length. Which postulate of Lamarck's theory of evolution was directly disproved by the outcome of this experiment?

  1. Organisms inherit somatic modifications acquired by their parents during their lifetime.Answer
  2. B
    Frequent use of an organ causes it to enlarge, while disuse leads to its degeneration.
  3. C
    New structures arise in organisms in response to specific environmental needs.
  4. D
    Natural selection acts on pre-existing variations to eliminate unfavorable traits.

Answer

Organisms inherit somatic modifications acquired by their parents during their lifetime.
August Weismann's experiment directly refuted Jean-Baptiste Lamarck's concept of the inheritance of acquired characteristics. Because surgical removal of tails affects only somatic cells and not germ cells (sperm and egg), the genetic code governing tail development remained unaltered across generations.

Step-by-Step Solution

1
Analyze the experimental setup and results.
Removing tails surgically for multiple generations represents an acquired somatic change, but offspring continued to inherit normal tails.
Acquired physical changes affect body (somatic) cells rather than germ cells.
2
Relate the empirical evidence to Lamarckian postulates.
Lamarck asserted that traits acquired during an organism's lifetime could be inherited by subsequent generations.
August Weismann's tail-cutting experiment demonstrated that changes to somatic tissues are not inherited, thus disproving the inheritance of acquired characteristics.

Key Concept

Debunking the Inheritance of Acquired Characteristics (Weismann's Germ Plasm Theory)
Estimated Time:1m 0s
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Topics

Lamarck's Theory of Evolution

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