Bunny Beans Activity Data Worksheet
Introduction
Recall that when two individuals reproduce, they each contribute one (1) haploid (n) gamete
(e.g. egg or sperm). When the egg is fertilized, mitosis occurs, forming a diploid (2n) zygote.
The alleles for fur color in this rabbit are G or g. Therefore, a gamete will contain either one G or
g allele. The possibilities for genotypes in the offspring zygote are GG, Gg, or gg. G is the
dominant genotype and the g is the recessive.
If a rabbit has either
GG or Gg, it is gray.
If a rabbit is gg, it is white
.
In this activity the pinto beans will represent the G (gray) allele and the white navy beans will
represent a gamete with the g (white) allele.
Problem
Natural selection affects allele frequency. If we find that a particular phenotype, such as rabbits
with white fur, is disappearing from a population, how can we, as wildlife biologists understand
how the mechanism of natural selection pressure may be affecting allele frequency? We would
like to do this in such a way as to not put the natural population in peril and without disrupting an
ecosystem. Imagine the addition of natural selection pressure…an increase in the fox
population.
Objectives
 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
Materials
 colored pencils (two colors per group)
 graph paper (one per person)
 white navy beans (50 beans per group)
 pinto beans (50 beans per group)
 opaque paper lunch bag (one per group)
 Calculator
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Safety


Clean up spills beans immediately to prevent slippage.
Do not put beans in your mouth.
Procedure
1) Place 50 pinto beans and 50 white navy beans into the paper bag.
2) Shake the bag. Remove two beans. These represent one rabbit’s genotype. Set
the pair aside, and continue to remove 49 more pairs. All group members should
pull beans to save time, carefully constructing the columns.
3) 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).
4) Examine your columns. Remove 25% of the gray rabbits and 100% of the white
rabbits. To ensure a random selection, simply remove the first rabbits from the
gray column. These numbers represent a random selection pressure on your
rabbit population. (The foxes!) If the number you calculate is a fraction, remove a
whole rabbit (round up) to make whole numbers. For example, if you result in 38
gray rabbits for the first generation (25% of 38 = 8.5), remove 9 of the gray
rabbits.
5) Count the number of pinto and navy beans remaining. Record this number in
your data table.
6) Calculate the allelic frequencies by dividing the number of beans of one type by
the total number of beans on display. Record data.
7) Begin the next generation by placing 100 beans into the bag. The proportions of
pinto and navy beans should be the same as the frequencies you calculated in
step 7. For example, if the outcome of generation 1 was 38 G (68%) and 18 g
(32%), then you will begin the next generation with 68 G and 32 g.
8) Repeat steps 3 through 8, collecting data for 5 generations.
9) Graph the frequencies of each allele over 5 generation. 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.
10) Return all materials to their proper places for reuse.
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Results
Generation
Number
Percentage
Frequency
Number
Percentage
Frequency
Start
50
50
0.50 (50%)
50
50
0.50 (50 %)
1
38
68
0.68
18
32
0.32
2
49
79
0.79
13
21
0.21
3
58
81
0.81
14
19
0.19
4
63
89
0 .89
8
11
0.11
66
89
0.89
8
11
0.11
Allele G- Gray Rabbit
Allele g- White Rabbie
(The numbers in red are a sampling result in a previous class.)
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Conclusions
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 frequencies is the number of eagles declined?
4) Explain any differences in allelic frequencies you observed between your data
and the data from the rest of the class. What advantage is there to having a large
amount of data? What problems might there be in using data from other
sources?
5) One year, there was an exceptionally high population of white bunnies. What are
some possible explanations for this population change?
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