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.
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.
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 two 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
visible than equally tasty members of their population may have a selective advantage over
their counterparts. We will scatter a population of 80 Beanus gooberensis, consisting of
equal numbers of two color variations of B. gooberensis: 40 yellow and 40 black. 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 two different kinds of specialized feeding
structures: knives and spoons. Which type of predator is best able to find and handle
bean prey? Stay tuned!
Materials:
 Several Cups
 1 Bag of white
beans


1 Bag of black
beans
17 knives


17 spoons
Data sheet
Procedure:
1. Break into 2 groups
a. Team Spoons
b. Team Knives
2. Put several runners of fabric where 40 beans of each type are dispersed
3. Predators arm yourselves!
Adapted by: Whitney McCormick from University of Miami 2014
4. At signal, predators will have 20 seconds to capture as many beans as possible
and place them in their mouths (cups) [Important- you can only carry one bean
at a time]
5. At the end of 20 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 for Generation 1.
7. For each color, the number of beans that remain in the fabric will be doubled and
added by dispersal in the area. Example: 10 yellow beans collected from 40,
leaves 30 yellow beans. Therefore add 30 yellow beans bringing the total
population to 60 yellow beans. Do the same for the black beans. [This will be the
starting number for Gen. 2]
8. Repeat two more times (2 more generations) and fill out the data tables as you
go. [There will be periodic breaks in between so you can do this]
Hypothesis: (0.5 points)- State your hypothesis in complete sentences
Write a hypothesis for your prey species and your predator species. Which kind of
predators (spoon or knife) do you think will be more successful and why? Which kind of
beans (black or yellow) do you think will be more successful and why?
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Use the following vocabulary words in your data analysis, discussion, and conclusion
sections (Underline these words in these sections)
population
characteristic
WORD BANK
adaptation
survive
fitness
reproduce
Data Analysis: (2 points)- Answer using complete sentences
-Fill out Data sheet attached then graph your data using your graph paper. -What do your bar graphs tell you about the predators and prey and their relative fitness?
First, use your data in order to explain who was more successful: the spoon predators or
the knife predators ---> COMPARE THESE SETS OF DATA. CITE SPECIFIC NUMBERS IN
ORDER TO SUPPORT YOUR CLAIM. Second, use your data in order to explain who was
more successful: the yellow beans or the black beans  COMPARE THESE SETS OF DATA.
CITE SPECIFIC NUMBERS IN ORDER TO SUPPORT YOUR CLAIM.
Discussion: (2 points)
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 why this was the case. Does
Adapted by: Whitney McCormick from University of Miami 2014
2.
3.
4.
5.
6.
7.
your data support your explanation? How so? CITE SPECIFIC NUMBERS IN
ORDER TO SUPPORT YOUR EXPLANATION.
Which predators seem to be best adapted to exploit this bean-rich environment?
Which is the least adapted? Explain why this was the case. Does your data
support your explanation? How so? CITE SPECIFIC NUMBERS IN ORDER TO
SUPPORT YOUR EXPLANATION.
Can you think of any factors besides bean color, which could have affected the
bean survival? Do you think that only one feature or characteristic is primarily
responsible for survival in a complex environment? Why or why not?
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?
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?
If we had more trials and we looked at more generations, what do you think will
happen? Which color will become more common over time? Which color will
become less common in this environment? Which predator will become more
common over time? Less common? Does your data support these predictions?
Looking at your data, how is the second generation different than the first
generation for both bean colors? CITE SPECIFIC NUMBERS. Is this second
generation (look at both bean colors and both kinds of predators) better suited
for survival in this kind of environment then the first generation was? Explain.
Conclusion: (0.5 points)
Answer the following questions in complete sentences.
1. What did you learn from this experiment? What do we mean by ‘success?’
2. Did the experimental results support or refute your hypothesis? Explain
3. How might these results look different if a yellow fabric was used instead of the
black fabric that was used in this experiment? Explain
Data Collection Sheet
Generation 1:
Predator
Black
Yellow
Total
Spoon40
40
80
Starting
#Beans
Spoon- Bean
Kills
Spoon- Bean
Survivors
Knife- Starting
40
40
80
#Beans
Knife- Bean
Kills
Knife- Bean
Survivors
Adapted by: Whitney McCormick from University of Miami 2014
Generation 2:
Predator
SpoonStarting
#Beans
Spoon- Bean
Kills
Spoon- Bean
Survivors
Knife- Starting
#Beans
Knife- Bean
Kills
Knife- Bean
Survivors
Generation 3:
Predator
SpoonStarting
#Beans
Spoon- Bean
Kills
Spoon- Bean
Survivors
Knife- Starting
#Beans
Knife- Bean
Kills
Knife- Bean
Survivors
Black
Yellow
Total
Black
Yellow
Total
Adapted by: Whitney McCormick from University of Miami 2014