1. Natural Selection and the Peppered Moth
Name
Date
Science
Class
Natural Selection and the Peppered Moth
Charles Darwin created a theory of evolution by natural selection.
Yet he was not able to demonstrate his theory in “real time” with the information he had. Unknown to Darwin, a rather quick evolution change was happening in his native England, during his lifetime, with the Peppered Moth. Here is the story….

2. Natural Selection and the Peppered Moth
Once upon a time… the forests surrounding London had trees covered in lichen. Lichen is a slow-growing plant that can cling to the bark of trees. Rainwater contains just enough nutrients to keep lichen alive. In this time, the White Peppered Moth rested on these tree trunks to hide from predatory birds. This moth was white with black speckles across its wings, so it was well camouflaged. There is a naturally occurring genetic mutation of this species which causes some peppered moths to have almost black wings, yet Black Peppered Moths were rarely sighted.

3. Then one day… the Industrial Revolution started (late 1700s)
Then one day… the Industrial Revolution started (late 1700s). New factories burned coal either directly in steam engines and furnaces, or by making electricity with coal-powered generators.

4. Over a period of years, soot produced by burning coal darkened the skies and blackened the trees nearby. Air pollutants dissolved in rainwater damaged the lichen and prevented them from growing on trees. By 1895, 98% of peppered moths in Manchester were black (Darwin died in 1882).

5. After many years… laws were put into place to control air pollution
After many years… laws were put into place to control air pollution. Tree trunks became cleaner and lichen growth increased. Once again, the white form of the Peppered Moths began to be sighted much more frequently than the black form.
Scientist Bernard Kettlewell has studied these changes in the Peppered Moth. He says that the moth, like every member of every species, is under constant selective pressure. If this pressure is high enough, within 50 generations one characteristic can substitute for another. It is due to such changes, he said, that new species are gradually evolving.

6. You will participate in a natural selection simulation.
Go on line to
Choose either a light forest or a dark forest.
A population of moths will be released that is 50% white and 50% black.
You play a hungry bird that eats peppered moths.
Click on every moth you see to “eat” it.
Your bird will make a crunching sound with each successful hunt, and a chirping sound with each failure.
Eat as many moths as you can in the minute you have.
Chart the percent of light and dark moths in your forest.
Then choose the other kind of forest. The game is the same.
Add your results to the class database.
Calculate averages.
Graph your results.
% light moths
% dark moths
Light forest
Dark forest

7. Sources http://peppermoths.weebly.com/ BEAST636. “Evolution of the
Peppered Moth.” YouTube, YouTube, 8 Feb. 2009,
“Rooftops And Smokestacks Of Factories | Industrial Revolution.” PBS
LearningMedia, ny.pbslearningmedia.org/resource/
industrial-revolution/rooftops-and-smokestacks-of-factories-
industrial-revolution/#.WueWAojwaUk.
“GCSE Bitesize: Indicator Species.” BBC, BBC,
“Teaching History.org, Home of the National History Education
Clearinghouse.” Coal and the Industrial
Revolution | Teachinghistory.org, teachinghistory.org/history-
content/beyond-the-textbook/23923.
“Peppered Moth and Natural Selection.” Home - Moths Count, 31 July
2009,
Natural Selection - What We Know, peer.tamu.edu/curriculum_modules/Ecosystems/module_1/whatweknow6 . htm.