Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 12
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Mechanism of Organic Evolution

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notes

Mechanism of Organic Evolution:

  • This theory was proposed by Hugo de Vries based on his work on evening primrose (Oenothera Lamarckian).  
  • Large differences arising suddenly in a population are called mutations.
  • Actually, mutations are sudden changes of genetic material (DNA) and hence all are inheritable.  
  • In addition to recombination, the mutation is another phenomenon that leads to variation in DNA.  
  • The mutation is a discontinuous source of variations and provides raw material for evolution.  
  • According to Hugo de Vries it is a mutation that causes evolution and not the minor variations (heritable) that Darwin talked about. 
  • Mutations are random and directionless while Darwinian variations are small and directional.  
  • Evolution for Darwin was gradual while de Vries believed mutation caused speciation and hence called it saltation (single step large mutation). 

Criticism of Mutation Theory:

  1. Natural mutations are not very common as Hugo de Vries thought.
  2. Mutations are normally recessive and harmful, while the characters taking part in evolution are usually dominant.
Darwinian Evolution Hugo de Vrie
Minor variations (heritable) cause evolution Mutation causes evolution
Variations are small and directional Mutations are random and directionless
Evolution was gradual Mutation caused speciation and hence, called saltation (single-step large mutation).
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