Exploring Population Dynamics: Predator-Prey Simulation
Student Report Form
In your study of yeast, a the biological model of population dynamics, you discovered that
yeast populations grow at an exponential rate until they either run out food or produce
sufficient waste to poison all of the yeast. But, when yeast is added to a sour dough starter
mix can live through many years, and probably billions of generations. It lives sustainably.
We learned that only a small number of strains of yeast can tolerate the acidic conditions
created by symbiotic bacteria in the yeast can survive and even their numbers are controlled
by the interactions between the bacteria, their metabolic products and the yeast. Extremely
complex systems with intertwined needs and roles together form another sort of biological
system, an ecosystem.
Essential Question: How can the interaction between predators and prey help to sustain a
system?
Tool: Rabbits and Wolves interactive model
(http://www.shodor.org/interactivate/activities/RabbitsAndWolves/)
1. Begin by going to the link above and then click on the “Activity” tab near the top of
the image. Describe the image that you see.
2. Select the “View Simulation Key” button at the bottom right of the images. What
information about the simulation does the pop-up window provide?
3. Select the “View/Modify Parameters” button near the bottom left of the image. Then
select “View/Modify Start-up Parameters”. List the start up parameters and
conditions in a table. To find out what each of these parameters means in the model
click on the “Learner” tab at the top of the image.
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4. Return to the “Activity” tab and then click on “Start Simulation”. Describe what is
being simulated, that is what is it meant to represent from the real world.
5. With the simulation still running click on “View Population Graph” near the bottom
of the screen. In this graph the x-axis shows the number of iterations, or the
number of cycles of time the simulation has completed. The y-axis shows food
capacity as a percent. When food capacity is zero, there are no more members of
that group present.
6. Click on “Reset the Simulation” and with the Graph open observe the behavior of the
model for 150 iterations. Experiment with the settings in the Rabbits and Wolves
Activity to build evidence for the answers to questions 7 through 9.
7. What would happen if there were lots more bunnies than there are were wolves?
Would the bunnies take over and live forever?
8. What would happen if there were lots more wolves than there are bunnies? Would
the wolves live forever?
9. How do the rabbits and wolves live in balance in this game?
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10. Experiment with the adjustable parameters (keep Forest Size and Forest Borders
constant) until you can keep some wolves, rabbits and grass alive for at least 200
iterations. Write down each change of each parameter that you make before you
adjust the model. Only change one parameter for each run of the simulation. You
may not be able to reach that balance. Nature has had a lot more time than you do
to find the right balance.
Parameter altered
Alteration
Impact
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