Kettlewell's experiment

In Great Britain during the late 1840s through the 1850s, it was noticed that there was a reduced number of light colored European peppered moths (Biston betularia) (light color was the dominant trait) and an increased number of the darker colored moths in the industrial areas. This led British ecologist Bernard Kettlewell to search for an explanation.

The experiment

During the late 1850s, Kettlewell began raising populations of light and dark peppered moths in his laboratory so he could perform his experiment. He marked all the moths with a drop of paint on the wings, so they could be recognized later. Next he released the light and dark moths in two separate wooded areas of England. One of the wooded areas was Birmingham wood near the highly industrial city of Birmingham, which was heavily polluted. The other wooded area was Dorset wood, which was in a rural area that was not polluted. At the end of this, Kettlewell set traps around the woods to catch the moths and see which populations survived in the two different areas. The moths that matched the color of the tree trunks survived. This showed that in the polluted areas where the trees were darker the dark peppered moths survived, and in the Dorset wood where the trees were lighter, the light peppered moths survived.

Conclusion

Kettlewell concluded that the pollution from the factories in Birmingham caused industrial melanism, which darkened the color of the woods. This in turn caused the moths with the recessive traits to have a better chance of survival because of the camouflage. So Kettlewell concluded that natural selection from industrial melanism caused the moths to adapt to their changing environment.

References

Johnson and Raven, George B. and Peter H. "Biology Pinciples and Exploration", Austin: Holt, RineHart and Winston, 1997, 290-291.