1. Short Term Evolution in the Peppered Moth

2. The Textbook Example
Before 1850, the predominant color phase of the peppered moth was the light form.
Trees were covered in lichens that made the bark light in color.
Biston Betularia
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3. Can’t see the light one? Neither can the birds that want to eat them.
The lighter color variant is favored before the industrial revolution.
Natural selection selects against the dark form. (They no longer blend in and do not survive to reproduce and pass on their genes.)
Biston betularia
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4. Manchester, England 1890: Emerging as an industrial town.
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5. “Industrial Melanism”
Soot darkened the trees.
A rare dark (melanic) form become predominant.
Biston Betularia
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6. Can’t see the dark one?
Neither could the birds that wanted to eat them.
Natural selection favored the dark form which was better camouflaged.
The dark moths survived to reproduce and pass on the gene for dark color to their offspring.
Biston betularia
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7. Manchester, England – more recently
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