Name: ___________________________________________ Date: __________________ Period: _________
Natural Selection of Bean Hunters!
In On the Origin of the Species by Means of Natural Selection, Charles Darwin put forth his
idea that evolution proceeded by means of natural selection. This idea can be distilled
down into 4 main tenets:
1. Overproduction: Organism have the capacity to produce large numbers of
offspring.
2. Variation: These offspring exhibit variable heritable traits
3. Competition: These offspring must compete for limited resources in the
environment
4. Differential reproduction: Those offspring whose physical traits enable them
to best exploit resources in the environment will leave more offspring than those
less well adapted.
a. Exploit: To use for ones
The results of natural selection are everywhere around you. The warning coloration
of a stinging bee, a woodpecker’s bill, perfectly shaped to extract insects from rotting wood,
the camouflaging color of a lizard against tree bark all have resulted from natural selection.
The raw material of these changes, of course, is non-lethal genetic mutations. The
ancestors organism alive today had mutations that might have made them slightly better
“prepared” for survival in a changing environment than other members of their species.
Whoever had the most babies won the evolutionary contest!
In real life, natural selection isn’t much fun if you’re the loser. But today’s
demonstration should be fun, even though some of use will go “extinct.” Today, we will
become predators with a variety of different mouthparts and our prey will be a species of
bean that comes in three different colors. Natural selection, sometimes a double-edged
sword, will work on both predator and prey. Let’s see how it works.
Bean Camouflage vs. Predator Mouthparts
Many predators rely on visual cues to detect prey. Tasty prey items that are less
conspicuous than equally tasty members of their population may have a selective
advantage over their counterparts. We will scatter a population of 600 Beanus
gooberensis, consisting of equal numbers of four color morphs of B. gooberensis: 200
white, 200 red, 200 split peas. Which color of bean is best at hiding from predators?
That’s what we’re going to find out. We predators will play predators having one of the five
different kinds of specialized feeding structures: knives, forks, spoons, tape and hand.
Which type of predator is best able to find and handle bean prey? Stay tuned!
Materials:
 30 Cups
 1 Bag of split
peas


1 Bag of red
beans
1 Bag of white
beans
Adapted by: Whitney McCormick from University of Miami 2014



6 knives
6 forks
6 spoons

6 large pieces of
masking tape

Data sheet
Procedure:
1. Break into 5 groups
a. Team Spoons
b. Team Forks
c. Team Knives (pick wisely)
d. Team popsicles sticks
e. Team Tape
2. Class goes outside to a grassy spot (or put several runners of fabric covering the
classroom floor) where beans of each type are dispersed
3. Predators arm yourselves!
4. At signal, predators will have 30 seconds to capture as many beans as possible
and place them in their mouths (cups)
5. At the end of 30 seconds, predators in each group will band together and count
how many of each color bean they have captured.
6. The group leader will call out the results from each group and EVERYONE should
write the results in Table 1.
7. The two groups with the least amount of beans become extinct (they can become
counters, weather during the next round, or they can return to their seats).
8. For each color, the number of beans that remain in the grass will be doubled and
added by dispersal in the area. Example: 50 green beans collected from 200,
leaves 150 beans. Therefore add 150 green beans bringing the total population to
300. Do the same for the other colors.
9. Repeat two more times (2 more generations) so only one group is left.
10. Fill out all data tables and compile onto a graph.
Predator Rules:
 Predators must pick up prey with their feeding apparatus only. No helping with
fingers or other objects, including the cups!
 Predators may not remove prey from a fellow predator’s cup (gross!), but they may
feel free to dash in and fight for any prey being pursued by another predator. It’s a
jungle out there. Hungry predators are not kind to strangers
Hypothesis:
Write a hypothesis for your prey species and your predator species. Do not say “I believe”
or “I think.” Make a claim.
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_________________________________________________________________________________________________________
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Data Analysis:
Adapted by: Whitney McCormick from University of Miami 2014
Fill out Data sheet attached then…
Insert final graph here comparing the predator/prey populations. What does the graph tell
you about the predators and prey and their relative fitness compared to their counterparts
(other predators)?
Discussion:
Answer the following questions in complete sentences.
1. Which color prey seem to be the best adapted to this environment and its
predators? Which is the least adapted? Explain.
2. Which predators seem to be best adapted to exploit this bean-rich environment?
Which is the least adapted? Explain.
3. Can you think of any factors besides bean color, which could have affected the
bean survival? Do you think that only one phenotypic character is responsible
for survival in a complex environment? Why or why not?
4. Can you think of any factors besides types of feeding apparatus, which might
contribute to an individual’s predators success (i.e. were any of the predators
more aggressive than others? Did any have better or poorer eyesight than the
others?
5. Did any predator or prey type become extinct? Why or why not? If none went
extinct, would you predict that any might go extinct over more generations?
Which ones and why?
Conclusion:
1. What did you learn from this experiment?
2. Did the experimental results support or refute your hypothesis?
3. What further tests might you perform on these populations?
4. How might the population change over time given the data you collected? Will
any species go extinct? Thrive?
Adapted by: Whitney McCormick from University of Miami 2014
Data Collection Sheet
Generation 1:
Predator
Spoon
Fork
Knife
High 5
Tape
Starting
#Beans
Bean Kills
Bean Survivors
Generation 2:
Predator
Spoon
Fork
Knife
High 5
Tape
Starting
#Beans
Bean Kills
Bean Survivors
Generation 3:
Predator
Spoon
Fork
Knife
High 5
Tape
Starting
#Beans
Bean Kills
Bean Survivors
Red
White
Green
Total
200
200
200
600
Red
White
Green
Total
Red
White
Green
Total
Adapted by: Whitney McCormick from University of Miami 2014
Adapted by: Whitney McCormick from University of Miami 2014