Assignment 12 – Natural selection in peppered mothsIn this activity, you will learn about the peppered moth of England, including how its natural history is a great example of natural selection and evolution at work.
Steps
Step 1: Read the following background information before going to the website
The following information is provided in addition to the introductory material on the website:
Charles Darwin’s theory of evolution includes natural selection as the mechanism for how evolution occurs. Natural selection is the process by which individuals with certain traits have greater survival and reproduction than individuals that lack these traits, resulting in an increase in the frequency of successful traits and a decrease in the frequency of unsuccessful ones. It is important to note that what is “successful” depends on the current environmental situation. As you will seen in the two simulations, a trait can be advantageous in one situation but detrimental in another.
The peppered moth of England comes in two different varieties: a light-colored variety and a dark-colored variety. Both of these varieties belong to the same species, Biston betularia. The dark-colored variety is actually the result of a DNA mutation that occurred in the evolutionary past of this species. It is referred to as carbonaria.
Prior to the industrial revolution, the landscape of England was somewhat light in color. Therefore, The light-colored variety was well camouflaged from predators because it was living on a light-colored landscape. The mutated dark variety could easily be seen by predatory birds and other animals, so it was much more likely to be eaten than the light variety. The dark variety did not have much of a chance to survive, reproduce, and pass on its dark trait to offspring. Thus, in the natural state of the environment the dark variety was uncommon.
With the industrial revolution came black soot from the burning of coal. This dark soot covered the landscape, causing a dramatic shift in the peppered moth species. It led to one of the best of examples of evolution by natural selection known.
At the end of the website introductory readings, you will run two different simulations. Both simulations will take place in England. One simulation will occur during the time period prior tothe industrial revolution. At this time the countryside had a light color, and thus your background will also be light in color. The other simulation will illustrate what occurred during the industrial revolution. Your background will change to a dark color.
It is important to note that during the course of the simulations, moths that have survived (avoided being eaten) are reproducing and passing on their alleles for their traits (their color) to their offspring. Thus, the simulations are occurring over successive generations.
You will play the part of a predatory bird that eats peppered moths.
Some things to take note of while you complete the two different simulations:
• Read the information contained in each of the links (the big circles), moving left to right. Be sure to read all of the pages by clicking on the triangles to the right. Did you notice that they used the word “theory” incorrectly? Where they say “theory” they mean to say “hypothesis!” A scientist does not initially test a theory by collecting evidence. As you know, a scientist tests ahypothesis by collecting evidence, and if the evidence reaches a point at which it becomes overwhelming, the hypothesis can then be raised to the level of theory.
• Notice that at the beginning of each simulation the proportion of dark moths to light moths is always 50% to 50%, or 50:50. In other words, there are equal amounts of each type of moth in the habitat.
• You will feed for 60 seconds and then the simulation will end. Be sure to keep eating during that time period. So that you get good results, be sure to eat as though the predator would. Eat the first thing that you see with each attack!
• Be sure to run both the “light forest” simulation and the “dark forest” simulation. Record your data for future reference, taking note of which data goes with the light background, and which data goes with the dark background. You will want to view your data while you answer the activity questions.
• Note that according to your data at the end of the simulation, the two colors of moths no longer appear in the habitat in equal numbers. One color will be found in a higher percentage (frequency) than the other. Thus, evolution has occurred! Any time that the frequency of a trait (e.g. color) in a population changes, evolution has been demonstrated. Thus, the peppered moth has evolved by the mechanism known as natural selection.
Step 2: Go to the website, read the introductory information, and complete the simulations on both the light and dark backgrounds
Go to the following link to visit the peppered moth interactive website. You may use either the Shockwave version or the Windows Projector version. Both work equally well and have the exact same content.
Note: The website uses flash technology. If you have trouble viewing the flash content, then please access the second link (just below the link to the peppered moth website) to view a transcript of all of the information contained on the peppered moth website, including a complete description of both simulations.
Go to the following link to visit the peppered moth Interactive website with flash content:
• Peppered moth interactive website
Or, go to the following link to view a transcript of the website content and simulations:
• Peppered moth interactive website transcript
End of the activity questions
Answer the following questions in a computer document. You will be submitting your completed document in the Assignment 12 dropbox.
• 1. The peppered moth comes in 2 varieties: dark-colored and light-colored. It is preyed upon by birds. Which would you expect to be most common if the environment is of a dark color: a population of light-colored moths or a population of dark-colored moths?
• 2. The peppered moth comes in 2 varieties: dark-colored and light-colored. It is preyed upon by birds. Which would you expect to be most common if the environment is of a light color: a population of light-colored moths or a population of dark-colored moths?
• 3. Did the events that occurred in England during and after the industrial revolution lead to natural selection and evolution in the peppered moth? Explain.
• 4. The peppered moth comes in 2 varieties: dark-colored and light-colored. It is preyed upon by birds. Suppose that prior to predation the population was 50% dark and 50% light, but after predation the population was 10% dark and 90% light. Did evolution occur?
• 5. The peppered moth comes in 2 varieties: dark-colored and light-colored. It is preyed upon by birds. Suppose that prior to predation the population was 50% dark and 50% light, but after predation the population was 10% dark and 90% light. Did natural selection occur?
• 6. The peppered moth comes in 2 varieties: dark-colored and light-colored. It is preyed upon by birds. Suppose that prior to predation the population was 50% dark and 50% light, but after predation the population was 10% dark and 90% light. What was the most likely color of the environment?
• 7. The peppered moth comes in 2 varieties: dark-colored and light-colored. It is preyed upon by birds. Suppose that prior to predation the population was 50% dark and 50% light, but after predation the population was 90% dark and 10% light. What was the most likely color of the environment?
• 8. Prior to the industrial revolution, were dark moths common or rare?
• 9. During the industrial revolution, were dark moths common or rare?
• 10. Once pollution was greatly reduced in England, what variety of moths was most common: light or dark?
Your evaluation of the activity
1. Did the activity help you to understand natural selection and evolution?
2. Are the directions for the activity clear?
3. What part of the activity was confusing?
4. Include any suggestions you have to improve this activity.
Thanks for your input.
In order to get credit, submit your document containing your answers to the end of the activity questions (#1-10) in the Assignment 12 dropbox .
Congratulations! You are now done with this activity!