Thursday April 17

1. 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

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

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

4. The black moths were easy to see against the lichen, but the light moths blended in and were hard to see. 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… If you were a hungry bird, which of these peppered moths would you grab for lunch?

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

7. What do you think happened to the moths?

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

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

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

11. 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.

12. 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 anunpolluted area that had lichen-covered oak trees; the other was awooded 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?

13. You’re right! In the unpolluted area (light-colored tree trunks), morelight-colored mothssurvived. In the polluted area (dark-colored tree trunks),moredark-colored mothssurvived. How does this experiment show the process ofnatural selection?

14. Note that this example illustrates Darwin's four points: • moth eggs are over-produced; many moths will not survive to reproduce. • there is variation among individuals -- some are black in color, others are light gray • the variation is genetic –black moths have different alleles for color than do gray moths • 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.