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Difficulty: MediumLamarck's Theory of Evolution

Ancestral reptiles are believed to have possessed fully developed limbs. According to Jean-Baptiste Lamarck's evolutionary principles, which process accounts for the complete loss of functional limbs in modern snakes?

  1. Continuous disuse of limbs during crawling in narrow spaces, followed by the inheritance of this acquired trait by offspringAnswer
  2. B
    Natural selection favoring individuals with shorter limbs that provided higher survival rates in subterranean habitats
  3. C
    Random gene mutations causing limb reduction that accumulated progressively across generations
  4. D
    Direct mutation of germ cells caused by the physical pressure of subterranean environments

Answer

Continuous disuse of limbs during crawling in narrow spaces, followed by the inheritance of this acquired trait by offspring.
Lamarck postulated that when an organism disuses a structure due to changing environmental habits (such as snakes crawling through tight crevices), that organ gradually atrophies and deteriorates. He maintained that such acquired somatic traits are directly inherited by offspring.

Step-by-Step Solution

1
Identify Lamarck's two core evolutionary postulates
Lamarck's theory relies on the Law of Use and Disuse and the Law of Inheritance of Acquired Characteristics.
Frequent use strengthens an organ while continuous disuse causes atrophy, and changes acquired during an organism's life are transmitted to offspring.
2
Apply these postulates to the evolution of limblessness in snakes
Crawling through narrow spaces led to the disuse and eventual reduction of limbs, and this limbless condition was inherited across generations.
Lamarck specifically cited snakes losing legs through disuse as a primary example of his evolutionary theory.

Key Concept

Lamarck's Theory of Use and Disuse and Inheritance of Acquired Characteristics
Estimated Time:1m 0s
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Topics

Lamarck's Theory of Evolution

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