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Organic Evolution

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Estimated time: 3 minutes
Maharashtra State Board: Class 12

Key Points: Organic Evolution

  • Organic Evolution - Slow, gradual, continuous and irreversible changes through which present-day complex life forms developed from simple pre-existing ones.
  • Darwin's Theory - Charles Darwin defined evolution as "descent with modification" — descendants become different from their ancestors over time.
  • Lamarck's Theory - Traits are acquired due to internal force, changes in environment, new needs, and use and disuse of organs; after several generations, new species arise.
  • Weismann's Disproof - August Weismann cut tails of rats for 21 generations but found no change in tail size, disproving Lamarckism.
  • Theory of Continuity of Germplasm - Weismann concluded that variations in somatic cells (somatoplasm) are NOT inherited, while variations in germ cells (germplasm) ARE inherited to the next generation.

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