Bio 103 - Introduction to Biology
                                Chapter 13: How Populations Evolve
                     ...
4. If you were the predator, switch roles and let your partner be the anteater and you can be the timekeeper.
   Record th...
Analysis and Conclusions:

1.   If you were a predator selecting from a field of an equal number of light and dark prey, y...
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C13 Peppered Moth

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C13 Peppered Moth

  1. 1. Bio 103 - Introduction to Biology Chapter 13: How Populations Evolve Peppered Moth Survey and Directional Selection Background Information: Natural selection, the reproductive success of organisms best suited to their environment, is a driving force in evolution. Natural selection occurs within populations, which are interbreeding groups of individuals of the same species. Genetic variation, the alternative types of genes for inherited traits, is one factor in the reproductive success of certain members of a population. The result of natural selection is adaptation, the changing of a population so that it is better suited to its environment. Industrial melanism is the term used to describe the adaptation of a population by the darkening of its individuals in response to industrial pollution. One example of rapid industrial melanism occurred in populations of peppered moths, Biston betularia, in the area of Manchester, England, from 1845 to 1890. Before the Industrial Revolution, the trunks of trees in the forest around Manchester were light grayish green due to the presence of lichens. Most of the peppered moths in the area were light colored with dark spots. As the Industrial Revolution progressed, the tree trunks became covered with soot and turned dark. Over a period of 45 years, a dark variety of the peppered moth became more common. In this lab, you will simulate how successfully predators locate prey in different environments. Then you will analyze actual data and relate changes in a population of peppered moths with two color variations to changes in the environment. Materials Needed (you’ll need a friend to complete this lab): 1. sheet of newspaper 2. newspaper disks (10) a hole punch makes very nice disks 3. pink paper disks (10) again, a hole punch makes very nice disks 4. pencil with an eraser 5. wet paper towel in a small dish (saucer would work just fine) 6. colored pencils (2) Procedure: Part 1: Simulating Predator-Prey Relationships 1. Work with a partner, and decide which of you will be the “predator” and which will be the timekeeper. 2. Place a sheet of newspaper on your lab table. If you are the timekeeper, scatter 10 pink paper disks and 10 newspaper disks on the newspaper while your partner looks away. The disks represent an anteater’s prey. If you are the predator, use the eraser end of a pencil to pick up as many disks as possible in 10 seconds while your lab partner watches the time. The eraser end of the pencil is to simulate the tongue of an anteater. It will be necessary to moisten the end of the eraser to more easily pick up the paper disks and place them in a small dish. 3. Count the number of each type of disk picked up in 10 seconds. Record these numbers in the data table below. Data Table Total Number of Ants Total Number of Ants Scattered on the Paper Consumed by Predation Pink Ants Newspaper Ants Trial Environment Pink Ants Newspaper Ants Consumed Consumed 1 Newspaper 10 10 2 Newspaper 10 10 Averages 1 success = preparation + execution
  2. 2. 4. If you were the predator, switch roles and let your partner be the anteater and you can be the timekeeper. Record the numbers in the data table for trial 2 and find the averages for both trials. Based on your averages, which ants were being selected against (eaten)? ____________________________ Would the future populations tend to be pink or newspaper in coloration? ___________________________ Part 2: Analyzing Predator-Prey Relationships - Directional Selection of Moth Colors due to Predation Number of Light Number of Dark Year Moths Captured Moths Captured 1 648 83 2 537 112 Examine the table at right, which 3 484 198 represents data from a 10 year study of a 4 392 210 population of peppered moths. The numbers represent moths captured in 5 246 281 traps that were located in the same area 6 225 357 each year. 7 193 412 8 232 382 9 312 249 10 503 109 Using the grid below and the data in the table above, construct a graph comparing the number of each color of peppered moth captured. Plot the years of the study on the x-axis (horizontal axis) and the number of moths captured on the y-axis (vertical axis). Use a different color of pencil or some other means to differentiate the color variations of the moths. Be sure to label each axis and to make a key for the graph. 700 600 500 400 300 200 100 0 1 2 3 4 5 6 7 8 9 10 2 success = preparation + execution
  3. 3. Analysis and Conclusions: 1. If you were a predator selecting from a field of an equal number of light and dark prey, you would expect to capture an approximately equal number of each color of prey. What did the experiment you conducted in Part 1 indicate? 2. Using the graph you made for step 8, describe what happened in the population of peppered moths between year 7 and 8. 3. How might the gene for dark coloration in the peppered moth have originated? 4. Is coloration an important factor in successful predation? Why? 5. What is the relationship between the environment and the color of the peppered moth? 6. Explain why an increase in the number of dark-colored peppered moths occurred during the Industrial Revolution. 7. What affect do you think using cleaner burning fuels had on the environment and the peppered moths near Manchester, England? 8. Draw a bell curve and label the basic parts. Which type of natural selection is being presented in this lab? (stabilizing, directional, disruptive, or sexual) 3 success = preparation + execution

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