Evolution and Natural Selection

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Evolution :- Biological evolution is the saga of inherited changes in populations over a period of time, leading to observable changes and modifications in living beings.
As Theodosus Dobzhansky put it “nothing in biology makes sense except in the light of evolution”.
  • What natural cause or mechanism is there which could explain why organisms change?
  • What hereditary mechanisms could enable organisms to change?
Natural Selection:-
  • More individuals of each species are born than can possibly survive, as a result of which there is a continuous “struggle for existence”.
  • Acquired adaptive and heritable changes increase the chance of survival in species.
Inference:-
  • Natural selection acts as a sieve or filter, through which only organisms with superior adaptive features survive, e.g., the giraffe with a long neck against a short one.
  • Organisms lacking these variations fail to survive.

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