The Peppered Moth
1. Investigate the process of Natural Selection using the Peppered Moth as the example
1. Analyze population trends
1. Understand the effect of human impacts on the living world.
NGSS: 3-LS4-2. Use evidence to construct an explanation for how the variations in characteristics among individuals of the same species may provide advantages in surviving, finding mates, and reproducing
Between 1831 and 1836 Charles Darwin, a naturalist, sailed around the world as a member of a British scientific expedition. During the trip he made observations about the natural world and collected numerous species of plants and animals. These observations led to a book called The Origin of the Species, where he proposed The Theory of Natural Section. Darwin suggests that “those individuals who possess superior physical, behavioral, or other attributes are more likely to survive than those which are not so well endowed” (a.k.a. survival of the fittest).
One example of an advantage that leads to survival of the fittest is camouflage. The term camouflage means to conceal by disguise. There are many examples in nature of animals that hide from predators. Chameleons are known for their ability to alter their skin color to blend in with the leaves and plants they are hiding in. This enables them to “sneak attack” their prey. Insects often use camouflage to hide from birds or other predators.
The case of the peppered moth in Manchester, England is a well documented scientific study of the value of camouflage in Natural Selection. This case involves two forms of a moth, an insect which relies on camouflage to survive. One form of the moth was white colored and the other form a black color. During the end of the 19th century, with the beginning of the Industrial Revolution, smoke particles from the factories gradually blackened the trees on which the moths rested. What was the result of this change in the environment? How were the moth populations affected? How did the moth populations change?
Instructions (ask your instructor which site should be used)
Click on: A bird’s eye view of natural selection (far right circle with bird)
Read: The Instructions
Play: 5 minutes in the Lichen Forest ; hit pause and write down your
percentages in the table below. Stop and goto the Sooty Forest.
Play: 5 minutes in the Sooty Forest ; hit pause and write down your
percentages in the table below. Stop and answer the questions.
Peppered Moth Analysis
Percent Dark Moths
Percent Light Moths
1. Explain how the color of moths increases or decreases their chances of survival depending on the environment.
2. Application: 500 light colored moths and 500 dark colored moths are released into a polluted forest. After 2 days the moths were recaptured, make a prediction about the number of each type of moth that would be captured.
3. How has the striking change in coloration come about? (Include an explanation of how the dark moth appeared and how the proportion of dark moths changed from 0.0005% to more than 90% in polluted forests.)
4. Using the four words we discussed in Lecture, explain how the Peppered Moth population is an example of Natural Selection.
5. Is Evolution a directed or purposeful event? Is it random? Or is a population evolving “toward something”? Explain your answer.