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A-Level Biology OCR A

Dark Pale Moths Industrial Natural Selection Frequency Peppered

In industrial areas, dark peppered moths were favored due to camouflage on soot-darkened trees, increasing the frequency of the 'dark' allele; previously, pale moths were more common. After pollution control, pale moths became prevalent again.

In industrial areas, dark peppered moths were favored due to camouflage on soot-darkened trees, increasing the frequency of the 'dark' allele; previously, pale moths were more common. After pollution control, pale moths became prevalent again.

Front Explain how natural selection has resulted in the change in frequency of dark and pale moths in populations of the peppered moth near industrial towns and cities over time.
Back Peppered moths:
  • Before industrial revolution, most were pale - camo against tree bark, dark ones were easily spotted and eaten
  • During industrial revolution, trees became darker bc covered in soot and loss of lichen cover - dark moths were better adapted bc more highly camouflaged
  • More and more of them survived and reproduced, increasing frequency of 'dark' allele 
  • Over time their number became much higher than pale due to natural selection where dark color was the advantageous characteristic
  • After clean air act, trees became paler and number of pale moths increased again

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