Question

State the Mutation theory of evolution along with it's main postulates!

Answer 1

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Mutation theory for the origin of new species was proposed by Hugo DeVries (1901). According to the mutation theory, new species arise from the pre-existing ones in a single generation by the sudden appearance of distinct and discontinuous heritable changes. DeVries called such sudden distinct heritable changes as mutations (L. mutare = to change). Darwin called them ports and Bateson named them saltations or saltatory (discontinuous) variations.

Main Postulates of the Theory:-

• Mutations are sudden, large and distinct, discontinuous heritable changes.

• All organisms have an inherent tendency to change or mutate.

• Mutations always appear full-fledged. So, there are no incipient stages in the development of a character or organ.

• Different mutations may appear in different members of the same population or same species.

• Mutations are large and distinct. They are different from minor, fluctuating directional variations, which according to Darwin produce new species.

• Mutations are indeterminate, i.e., they appear in all directions and may be useful or harmful

• Mutations are subjected to natural selection. Beneficial mutations are selected and favoured by nature and harmful or lethal mutations are eliminated by the death of mutants

• Mutations may appear (i.e., may occur) again and again generation after generation. Thus, they provide more and more chances of selection by nature.

• Evolution by mutations is discontinuous and a jérky process.

• Mutation theory can explain the occurrence of vestigial and even overspecialised organs.

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