Thursday April 17 Essential Question: What is a selective pressure? What are some examples? Today Peppered Moth Case Study. For Full points Answer Questions in complete sentences. Finish Study Guides

The Peppered Moth The "typica" form of the moth (light-colored) The "carbonaria" form (dark-colored) variationslight gray dark gray The Peppered Moth has 2 variations: light gray and dark gray.

The peppered moth lives in a forest in England. The trees in the forest are covered with lichen.

If you were a hungry bird, which of these peppered moths would you grab for lunch? black moths light moths The black moths were easy to see against the lichen, but the light moths blended in and were hard to see. dark moths Birds ate more of the dark moths, until there were a lot of light moths and very few dark ones. Ha ha! You can’t see me…

pollution One day factories moved into the area, and released pollution into the air. soot. The trees were blackened with soot.

What do you think happened to the moths?

You’re right! light moths dark moths The birds ate more of the light moths because they were now easier to see than the dark moths. dark moths light ones Eventually there were a lot of dark moths and very few light ones.

Peppered moths on a normal tree background Peppered moths on a tree darkened by soot

When the monster came, Lola, like the peppered moth and the arctic hare, remained motionless and undetected. Harold, of course, was immediately devoured.

Peppered moths have lived in the forests of England for thousands of years. They rest on the trunks of trees during the day, and are a source of food for many birds. Peppered moths vary in color, from light- colored to dark-colored. These color variations are genetic. Before the Industrial Revolution, the tree trunks were light-colored. The trunks and branches were also covered with silvery-white lichens. As industry grew, pollution killed the lichens and blackened the tree bark.

unpolluted area that had lichen-covered oak trees;wooded area that had experienced pollution for many years In the 1950s, Oxford University professor H.B.D. Kettlewell and his students performed an experiment. They released the same number of light and dark-colored moths in two areas. One was an unpolluted area that had lichen-covered oak trees; the other was a wooded area that had experienced pollution for many years. After a certain amount of time, they recaptured as many moths as they could, and counted them. What do you think the results of the experiment were?

You’re right! unpollutedlight-colored tree trunksmore light-colored moths survived In the unpolluted area (light-colored tree trunks), more light-colored moths survived. polluted area (dark-colored tree trunksmore dark-colored moths survived In the polluted area (dark-colored tree trunks), more dark-colored moths survived. natural selection How does this experiment show the process of natural selection?

Darwin's four points: Note that this example illustrates Darwin's four points: over-produced;  moth eggs are over-produced; many moths will not survive to reproduce. variation  there is variation among individuals -- some are black in color, others are light gray genetic  the variation is genetic –black moths have different alleles for color than do gray moths advantage  the different colors differ in advantage-- in industrial environments, black moths survive to reproduce better than gray moths do. In unpolluted environments, the opposite is true.