In this article we will discuss about Examples of natural selection:- 1. Industrial melanism, 2. DDT-resistant mosquitoes and 3. Sickle cell anemia
1. INDUSTRIAL MELANISM
- This phenomenon was studied by Bernard Kettlewell in England
- Peppered moth exist in two forms black and grey
Early 1800s
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- Preindustrial England
- Low pollution
- Plenty of Lichen grow on tree
- Grey color moth population is increased
- Black color moth is very few
Late 1800s
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- Industries developed and that area was polluted
- All lichens are disappear
- Grey color moth population reduced
- Black color moth is increased
Mid 1900s
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- 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
2. DDT-RESISTANT MOSQUITOES
- 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
3. SICKLE CELL ANEMIA
- 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
