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Meaning of Evolution

Evolution

  • The term "Evolution" was given by Herbert Spencer.


  • Evolution is defined as a process of slow and gradual change seen in an orderly fashion. In other words, evolution is the gradual change in heritable traits of living organism over a number of generation.
  • It means to unroll or to unfold or to reveal the hidden potential.
  • Darwin defined evolution as "Descent with modification".
  • Every kind of change is not evolution. Evolution is change between successive generation.
  • "LIFE IS NOT ORIGINATING NOW, IT IS EVOLVING NOW."
  • Life has stopped originating now because the environment now is not like that of primitive earth . It has changed from reducing to oxidizing environment. 
  • Evolution is often defined as formation of complex forms from simple form but Complexity is never the aim of evolution.
  • Aim of evolution is fitness of an organism with surrounding.
  • Had complexity been the aim of evolution the parasites would have vanished.
  • Parasite show simplification in structure in course of evolution.
  • Evolution means successful feeding and breeding.
  • Gene pool changes over a number of generation.


Unit of evolution

Population
Driving force for evolutionNatural selection
Unit of natural selectionIndividual
Raw material for evolutionVariation
Ultimate source for variation

Mutation


"Individual get selected and population get evolved".

  • Evolution is a continuous process. It never stops because environment is never constant.
  • There is no climax of evolution.
  • Evolution is not goal oriented.
  • It is not a direct process in terms of determinism.
  • It is a stochastic process (a process about which we cannot say with 100% accuracy and surety)

Doll's law / law of Evolutionary Irreversibility :

Evolution is irreversible . Evolution is progressive.