Examples of Natural Selection Short Note | Evolution Class 12 Notes

In this article we will discuss about Examples of natural selection:- 1. Industrial melanism, 2. DDT-resistant mosquitoes and 3. Sickle cell anemia


  • This phenomenon was studied by Bernard Kettlewell in England
  • Peppered moth exist in two forms black and grey

Early 1800s

    • Preindustrial England
    • Low pollution
    • Plenty of Lichen grow on tree
    • Grey color moth population is increased
    • Black color moth is very few

Late 1800s

    • Industries developed and that area was polluted
    • All lichens are disappear
    • Grey color moth population reduced
    • Black color moth is increased

Mid 1900s

    • In factories use electric current and pollution controls
    • Again lichens are grown on tree
    • Grey color moth population is increased
    • Black color moth is very few

Examples of Natural Selection


  • Mosquitoes are vectors of diseases like malaria and elephantiasis
  • Earlier the mosquito more DDT sensitive
  • DDT as an insecticide introduced in 1940s
  • Certain individuals are resistant to DDT
  • This resistant mosquito reproduce more and more offspring’s
  • The resistant population are evolved as a selective advantage against insecticides


  • Genetically transmitted disease of the blood
  • Caused by presence of abnormal hemoglobin S
    • Hb Hb – Normal
    • Hb Hs – Sickle cell trait
    • Hs Hs – Sickle cell anemia
  • Individuals with heterozygous condition have better chances of survival, hence are selected by nature

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