Biology 9
Evolution – Predatory and Prey Simulation Lab
Objectives:
• To demonstrate the Darwinian principles of natural selection
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To understand the interplay between natural selection and sexual selection
Part 1: Evolution: Predator and Prey Simulation
Background:
The process of natural selection occurs because organisms vary in their genetically determined
characteristics or traits. The different genetic traits enable some variants to survive and reproduce better
than others. As a result, the genetic structure of a population changes over time. Although evolution
involves the genetic change in a population over time, natural selection is the pressure or driving force
behind evolution and occurs through the interaction of the environment and the whole organism. Natural
selection does not cause genetic mutations, it only “selects” or pushes for the survival of individuals with
certain genotypes.
Darwinian Principles:
1.
2.
3.
4.
Variation exists in populations.
More offspring are born than survive AND reproduce.
Variation is inherited.
The interaction between a population and the environment in which it lives leads to selective
pressures for certain variations.
In this exercise we will simulate how natural selection works. Natural selection and evolution take a long
time to occur in natural populations, so we will use artificial organisms or populations. For Part I, the
variation is the coloration of the beads, and the environment or habitat is colored cloth. For Part II, the
variation is the type of utensil used by the predator and the environment is represented by the container of
pasta or beans. As you execute the laboratory, think about the interaction between the variations in the
population, the environment, and their differential survival.
Materials:
Fabric (habitat)
4 different colored beads in Ziploc baggies
paper bowl
Procedure:
1. Spread the fabric habitat on the table-top.
2. Count out 20 of each color bead for a total of 80 “organisms” to start with.
3. Appoint one individual as the organism “distributor”. That individual will place the organisms
randomly over the entire habitat, making sure that they are not too close together. The other members
of the group should turn their backs (i.e. not watch) while this is happening.
4. The rest of the group members are “predators”. They should take turns picking up the organisms one
by one until 20 remain (each predator gets 15 turns). COUNT CAREFULLY and BE ACCURATE and
THOROUGH. Predators are to take the first organism they see and keep their eyes on that one
organism until it is removed from the habitat. Avoid wandering eyes! For example if you were a bird
of prey, you would only be able to see the actual prey you are consuming until you are ready to search
for more.
5. Record the number of survivors of each color/type in the table on the next page.
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6. Assume each survivor produces three offspring. Using the reserve beads, the “distributor” is to add the
offspring to the survivors. The total number of organisms should equal 80 when you are done.
7. Repeat Steps 4-6 two additional times, simulating three total generations. Record your data in the table
below and answer the questions that follow.
PREDATOR & PREY SIMULATION
Colors/Types of Beads
# at start
20
20
20
# after 1st
predation
# after 1st
reproduction
# after 2nd
predation
# after 2nd
reproduction
# after 3rd
predation
20
Total
80
20
80
20
80
20
1. Study your survivor populations
a. Was one color represented more than others in the first generation of survivors?
b. Were shades of color that were similar also present?
c. What, if any, changes occurred between the 1st and 2nd, and again between the 2nd and 3rd
generation of survivors?
2. Is there any color from the original population that is NOT represented in the survivor population? If
not, what term would most appropriately describe this species absence?
3. How do you think the colors of the survivors are related to their habitat? Would the results change if
you had the same organisms on a different piece of cloth? Explain.
4. What aspect of the simulation represented principle #1: “Variation exists in populations”?
5. What aspect of the simulation represented principle #2: “More offspring are born than survive AND
reproduce”?
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6. What aspect of the simulation represented principle #3: “Variation is inherited”?
7. What is/are the driving force(s) behind “natural selection” in this simulation? In other words, what
aspect(s) of the environment selects for certain variation and against other variations?
Part 2: Eating Utensils and Survival of Predators
Materials:
Sunglasses
Chopsticks (one set)
Spoon
Fork
Container with an assortment of beans or pasta to serve as prey
Bowl
Procedure:
1. Select three people to serve as predators and have each person select one of the available predator
modifications (wearing sunglasses, using chopsticks, using a fork, or using a spoon). The other group
members will act as timers and/or prey counters.
2. Give each “predator” 15 seconds to remove as many food items (prey) as possible from the container
and place into the bowl. Food pieces must be removed ONE AT A TIME.
3. If the predator is able to get 10 pieces, it will survive. If the predator collects less than 10 pieces, it does
not survive. If a predator survives, it (he/she) gets to participate in the next round.
4. Repeat steps 2 3 until only one predator (with the corresponding modification) remains. This predator
is the “fittest” because it was able to survive long enough to reproduce.
5. Fill out the table below and answer the questions that follow on the next page.
EATING UTENSILS AND SURVIVAL OF PREDATORS
Predator Variation
Number of Prey in 15 seconds
Survived?
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1. What aspect of this simulation represented principle #1: “Variation exists in populations”?
2. What aspect of this simulation represented principle #2: “More offspring are born than survive AND
reproduce.”?
3. What aspect of this simulation represented principle #3: “Variation is inherited”? Hint: what type of
predators would be represented in the NEXT generation?
4. More and more, molecular similarities are providing evidence for evolutionary relatedness among
organisms. As evolution occurs and mutations happen, organisms that look different should still share
molecular similarities. Indeed, we have found that the DNA of every living thing (with very few
exceptions) has identical components in all creatures. Enzymes (protein which catalyze chemical
reactions) are very similar in different organisms when they perform the same function. All organisms
participate in cell division (mitosis). Studies using biotechnology and study of molecules have
supported many aspects of evolution. Think of the different specific molecules that you have studied
this semester and what they do (i.e. insulin). LIST 5 MOLECULES whose function must be common to
ALL life forms (insulin is not common to all life forms, but RNA is!).
Part 3: Sex and the Single Guppy: The Interplay Between Natural Selection and Sexual Selection
In the 1970s, an investigator named John Endler traveled to Trinidad in the 1970s to study wild guppies.
The guppies live in small streams that flow down the mountains from pool to pool. In this activity, you will
take part in an online simulation of Endler's work. You will collect data, formulate a hypothesis, and run a
series of experiments. You will find out about the interplay between natural selection and sexual selection
in this wild population of guppies.
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Launch the Sex and the Single Guppy Web activity at
http://www.pbs.org/wgbh/evolution/educators/lessons/lesson4/act2.html. The website can also be
accessed at the course website.
Select "I'm ready to find out."
Read the text, and click on the pools to investigate the guppy stream more closely.
Then click on "What causes guppy color variation?" Select one of the hypotheses or create your own,
and record it below.
Visit the Guppy Gallery. Read about the different types of guppies, their predators, and their habitats.
Click on "simulation." Proceed with the simulation by creating and carrying out a field experiment to
gather data to test your hypothesis. Record your data. (You may need to alter your hypothesis if the data
does not support it.)
Flashy Fish: Data
1. If being flashy attracts predators, why are male guppies so colorful?
2. What do you think is responsible for the variation in color from one generation to the next?
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3. Select a hypothesis from the Sex and the Single Guppy Web activity or come up with your
own and record it here.
4. Next you will set up your experiment as directed in the simulation. Record your initial
settings here.
Predator types and numbers:
Initial guppy population:
5. Run your initial experiment for at least five generations and record your results.
Number of guppies:
Number of generations:
Number of weeks:
Male color types:
Brightest male guppy ____%
Bright male guppy ____%
Drab male guppy ____%
Drabbest male guppy ____%
6. Was your hypothesis supported by your data? Why or why not?
7. Select a new hypothesis and record it here:
Record your new data.
Predator types and numbers:
Initial guppy population:
Run your experiment for at least 5 generations and record your results.
Number of guppies:
Number of generations:
Number of weeks:
Male color types:
Brightest male guppy ____%
Bright male guppy ____%
Drab male guppy ____%
Drabbest male guppy ____%
8. Was your new hypothesis supported by your data? Why or why not?
9. Summarize what you learned from your experiments regarding natural and sexual selection.
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