Darwin's contribution, modern synthetic theory of evolution

  • ⇒ Darwin's contribution / modern synthetic theory of Evolution.
  • Salient features of Darwin's theory of natural selection is given below
    (i) ⇒ Over production [Some organisms produce more offspring and others produce fever offspring called differential reproduction]
    (ii) ⇒ Limited food and space
    (iii) Struggle for existence - (i) intraspecific (ii) interspecific (iii) Environmental struggle
    (iv) Variation : Variations are continuous and would pass onto next generation if its useful for adaptation.
    (v) Natural selection: Initially, it was termed as the survival of the fittest by Herbert Spencer.
  • The present ideal of evolution is a modified from a Darwin's theory of natural selection and is called as Neo - Darwinism, which states that only genetic variations are inherited.
  • Modern concept of evolution is also known as synthetic theory of evolution as it is the synthesis of Darwin's and Hugo De vrie's theory.
  • Scientists involved in synthetic theory : T. Dobzansky, R.A. Fisher, Haldane, Swell wright, Ernst mayr, stebbins [process of organic evolution]
  • Factors involved in synthetic theory are given below.
  • Genetic variation in population [It is the population that evolves, where as every single organism contributes to the evolution by inducing variation by themselves.
  • Genetic variation is induces by following factors such as mutation [Bateson saltation; Darwin - sports] [Types → chromosomal; gene]; Gene recombination; Gene flow /Gene migration ; Genetic drift (or) Sewall - wright effect [a) Founder effect; due to the movement of small group of individual from a large population, called as founders; b) bottle neck effect : (stebbins) severe reduction in population due to natural calamity]; Hybridization; Non random - mating.
  • Isolation is the prevention of mating amongst interbreeding groups [between population of 2 different species]

    • Isolation
      (Premating) (Post - mating)
      mechanical incompatibility
      psychological Hybrid inviability
      Seasonal Hybrid sterility
      Gametic Hybrid breakdown
  • Other factors that modern theory focusses are Heredity, Natural solution, specification.

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