Evolution Example


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•  Development of melanistic insects in polluted areas

Peppered moths (Biston betularia) exist in two distinct polymorphic forms – a light colouration and a darker melanic variant

  • In an unpolluted environment, the trees are covered by a pale-coloured lichen, which provides camouflage for the lighter moth
  • In a polluted environment, sulphur dioxide kills the lichen while soot blackens the bark, providing camouflage for the dark moth

Peppered Moth Variants (Light vs Dark Colouration)

peppered moth

The frequency of the two different forms of peppered moth is dependent on the environment and evolves as conditions change

  • Before the industrial revolution, the environment was largely unpolluted and the lighter moth had a survival advantage
  • Following the industrial revolution, the environment became heavily polluted, conferring a survival advantage to the darker moth
  • Recent environmental policies in Europe are reducing pollution levels, altering the frequency of the two populations once again

Evolution of the Peppered Moth in a Polluted Environment

peppered moth graph

Graph represents the findings of a 1953 study by Bernard Kettlewell comparing peppered moth populations in polluted and non-polluted regions

Link:  Peppered Moth Simulation