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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 views: 6 posted: 10/18/2012 language: Latin pages: 3