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 Natural Selection and Allelic Frequency Evolution can be described as the change in allelic frequencies of a gene pool over time. Natural selection can place pressure on specific phenotypes and cause a change in the frequency of the alleles that produce the phenotypes. In this activity, you will simulate the effects of eagle predation on a population of rabbits, where GG represents the homozygous condition for gray fur, Gg is the heterozygous condition for gray fur, and gg represents the homozygous condition for white fur. Problem How does natural selection affect allelic frequency? Objectives In this BioLab, you will: Simulate natural selection by using beans of two different colors. Calculate allelic frequencies over five generations. Demonstrate how natural selection can affect allelic frequencies over time. Use the Internet to collect and compare data from other students. Materials Colored pencils (2) Paper bag Graph paper Pinto beans White navy beans Data Sources Skill Handbook Use the Skill Handbook if you need additional help with this lab.
 1. Print the data table shown below. 2. Place 50 pinto beans and 50 white navy beans into the paper bag. 3. Shake the bag. Remove two beans. These represent one rabbit's genotype. Set the pair aside, and continue to remove 49 more pair. 4. Arrange the beans on a flat surface in two columns representing the two possible rabbit phenotypes, gray (genotypes GG or Gg) and white (genotype gg). 5. Examine your colunmns. Remove 25 percent of the gray rabbits and 100 percent of the white rabbits. These numbers represent an arbitrary selection pressure on your rabbit population. If the number you calculate is a fraction, remove a whole rabbit to make whole numbers. 6. Count the number of pinto and navy beans remaining. Record this number in your data table. 7. Calculate the allelic frequencies by dividing the number of beans of one type by 100. Record these numbers in your data table. 8. Begin the next generation by placing 100 beans into the bag. The proportions of pinto and navy beans should be the same as the percentages you calculated in step 7. 9. Repeat steps 3 through 8, collecting data for five generations. 10. Post your data in the table below. 11. Graph the frequencies of each allele over five generations. Plot the frequency of the allele on the vertical axis and the number of the generation on the horizontal axis. Use a different colored pencil for each allele.

 Allele G Generation Number Percentage Frequency Start 1 2 3 4 5 Allele g Generation Number Percentage Frequency Start 1 2 3 4 5
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 1. Analyzing Data Did either allele disappear? Why or why not? 2. Thinking Critically What does your graph show about allelic frequencies and natural selection? 3. Making Inferences What would happen to the allelic frequencies if the number of eagles declined? 4. Using the Internet Explain any differences in allelic frequencies you observed between your data and the data from the Internet. What advantage is there to having a large amount of data? What problems might there be in using data from the Internet?