natural_selection_bean_lab

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					Natural Selection and Allelic Frequency Lab                                Name___________________
                                                                                      Period_______
Problem
        How does natural selection affect allelic frequency?
Objectives
     Simulate natural selection by using beans of two different colors
     Calculate allelic frequencies over 5 generations
     Demonstrate how natural selection affects allelic frequencies over time
Safety Precautions
        Clean up spilled beans immediately to prevent anyone from slipping.
Hypothesis
        How will and allelic frequency of a population change for rabbits that are either Brown (BB or
        Bb) or white (bb) if their predators are better able to see the white rabbits?

        My hypothesis is ______________________________________________________________
        ____________________________________________________________________________
        ________ ______________________________________________________________.

Procedure
       1. Record all data in the table provided below.
       2. Place 50 brown beans and 50 white beans into a paper bag
       3. Shake the bag. Remove 2 beans. These represent one rabbit’s genotype (Brown bean =B
          and white bean = b). Set aside the pair, and continue to remove the 49 other pairs. Line
          them up in order.
       4. Arrange the beans on a flat surface in two columns representing the two types of
          phenotypes, brown (BB or Bb) and white (bb).
       5. Examine your columns. Remove the first 25% of the brown rabbits and the first 75% of the
          top white rabbits. These numbers represent a random selection pressure on your rabbit
          population. If the number you calculate is a fraction, remove a whole rabbit to make whole
          numbers.

            Example: If you have 30 brown rabbits (either BB or Bb) then
               30 (number of rabbits) X 25% (% you are removing) = 7.5 rabbits to
               be removed. Since you can’t remove ½ a rabbit, you should remove 8.

        6. Count the number of brown and white beans remaining. Record this on your data table
            under the heading “number” and lining up with “generation 1”.
        7. Calculate the allelic frequency by dividing the total number of each bean color by the total
            number of beans remaining. Record this number on the table under “frequency.”
        8. Multiply the frequency by 100 to get your percent.
        9. Begin the next generation by placing 100 beans into the bag, BUT this time the proportion of
            beans should be the same as the percent you calculated in step 8.
              Example: If I had 60% brown and 40% white, then I should put 60 brown and 40 white
              beans back into the bag.
        10. Repeat steps 3-9 for five more generations
      11. Graph the frequencies of each allele over five generations. Plot the frequency each allele
          the vertical axis and the number of the generation on the horizontal axis. Use a different
          colored pencil to do each allelic frequency line.
      12. Return all materials to their proper places

                        Allele G (Brown)                                Allele g (white)
 Generation      Number    Percentage Frequency            Number       Percentage       Frequency
   Start           50         50.00      0.50                50              50             0.50
     1
     2
     3
     4
     5

Conclusion:
   1. Did either allele disappear? Why or Why not?
       ______________________________________________________________________________
       ______________________________________________________________________________
       ______________________________________________________________________________

   2. What does your graph show about allelic frequencies and natural selection?
      ______________________________________________________________________________
      ______________________________________________________________________________
      ______________________________________________________________________________
      ______________________________________________________________________________

   3. What would happen to the allelic frequency if eagles declined?
      ______________________________________________________________________________
      ______________________________________________________________________________
      ______________________________________________________________________________
      ______________________________________________________________________________.

   4. Compare your results to others in the class that have done the same lab. Does their data match
      yours identically? Why or why not? What advantage is there to having a large amount of data?
      ______________________________________________________________________________
      ______________________________________________________________________________
      ______________________________________________________________________________
      ______________________________________________________________________________
      ______________________________________________________________________________
      ______________________________________________________________________________.

				
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