Modern Synthetic Theory Short Note | Evolution Class 12 Notes

In this article we will discuss about Modern Synthetic Theory of evolution:- Genetic Variation, Natural Selection and  Isolation

  • Modern theory of evolution combining Theory of natural selection and Theory of mutation
  • This modern concept of evolution is synthesis of Darwin’s and Hugo de Vries’ theories
  • This is also called Synthetic Theory of Evolution
  • Synthetic theory of evolution is the result of the work of a number of scientists namely T. Dobzhansky, R.A. Fisher, J.B.S. Haldane, Swell Wright, Ernst Mayr and G.L. Stebbins.

Concept of Modern Synthetic Theory

  1. Genetic Variation
  2. Natural Selection
  3. Isolation


i) Mutations

  • Mutations are sudden heritable changes
  • Mutations are of two types
    • Chromosomal Mutations: due to changes in chromosome number and changes in structure
    • Gene Mutations: Sudden change in a gene is called gene mutation or point mutation

ii) Hybridization

  • Mating of unrelated individuals
  • Offspring’s are called hybrids

iii) Recombination

  • New combinations of genes which are usually caused by the crossing over during gametogenesis
  • It is continuous and common source of variation in a sexually reproducing population

iv) Genetic drift

  • Elimination of gene or alleles from population


  • Organisms with favorable variation succeed in the struggle for existence
  • They are fittest for survival and other animals unfit to survival
  • Fitness and unfitness is decided by environment
  • Process of selection of organisms with favorable variation is called natural selection


  • Isolation is a segregation of populations by some barriers which prevent interbreeding
  • The reproductive isolation between the population due to certain barriers leads to the formation of new species

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