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Example of Natural Selection

Example of Natural Selection - clean areas the trees were...

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Example of Natural Selection: The Peppered Moth There are two forms of the peppered moth ( Biston betularia) in England- a dark- colored form (carbonaria) and a light form (typica). In the early 1800's, most moths were the light form. The first dark form was reported in 1848. The dark form increased in frequency during the last half of the 1800s. By 1895, 98% of the Moths in Manchester were the dark form. The increase in the dark (carbonaria) form of the moth occurred at a time of rapid industrialization in England- the industrial revolution. During this time, an increase in the amount of coal-burning factories caused widespread pollution. The pollution killed light-colored lichens , causing the trees to be darker. The trees in polluted areas were also covered with dark soot. In 1896, J. W. Tutt proposed that bird predation was responsible for the increase in abundance of the dark form of the moth. He reasoned that birds had difficulty seeing the dark form on the dark trees; the moths were camouflaged and survived better. In
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Unformatted text preview: clean areas, the trees were covered with lichens, making the pale form more difficult for birds to see. In the early 1800s, the trees were light and the light form were more difficult to see. To test the bird predation hypothesis, H.B.D. Kettlewell released moths of each type and then measured the number that were later recaptured. The experiment was performed in a polluted area in Birmingham, England and in a clean area in Dorset. The moths were marked with a dot of paint so that he could identify them after they were released and then recaptured. In the unpolluted area, he recaptured 13.7% light, 4.7% dark indicating that the light form survived better. In the polluted area, he recaptured 13% light and 27.5% dark suggesting that the dark form survived better. These results support the hypothesis that color change was due to bird predation. Birds ate moths that were easiest to find....
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