Names: ________________________________________________________ Pd. __________
Environmental Systems: 7A - Relate Carrying Capacity to Population Dynamics
Process TEKS: 2A, 2E, 2F, 2I
Predator Prey Lab
(Adapted from Lab Investigations for AP Environmental Science)
Purpose:
-
Simulate and analyze the interactions between a predator population of coyotes and a prey population of mice.
-
Organize and graph data from the simulation, predicting future populations over several generations
-
Compare simulation results to data taken from nature, and apply revised simulation techniques to new
population problems.
-
Define carrying capacity
Introduction:
Predator-prey interactions in a community are usually a feedback mechanism. The prey population has a positive effect
on predator numbers, but the predator population has a negative effect on prey populations. The predator prey
relationship can be represented as changing cyclically with a phase diagram, as shown in figure 1:
Figure 1:
1. Describe another relationship you have seen that would be a feedback mechanism like the predator prey model.
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
In the lower right quadrant, as the predator population rises, the prey population also rises. But as the predator
numbers reach a particular value, the prey population starts to decrease, followed by an eventual decrease in the
Names: ________________________________________________________ Pd. __________
predator population as well (upper left quadrant). In time, the predator population becomes small enough for the prey
numbers to rebound and the process continues into another cycle. In nature, the cycles are more complex than the
diagram above, as there are many other influences on populations in the wild.
2. Describe three other environmental pressures that might affect the relationship between mice and coyotes.
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
In this investigation, we will focus only on the predator-prey relationship.
Materials:
-
Masking Tape
-
Graph Paper
-
Model Coyotes and Mice
Procedure:
Your lab group will determine the prarameters of the simulation. You will need to determine the following before
beginning:
1. How large is your field? (HINT: Use tiles on the floor as a measurement tool)
___________________________________________________________________________________________
a. Mark the field with Masking Tape
2. How many mice are found in your sample ecosystem to begin with? ____________________________________
a. Place that many small squares in your field.
3. How many mice does 1 coyote need to consume in order to survive and reproduce (1 pup)? ________________
a. A coyote is the large square
4. How many mice above the minimum must a coyote consume to survive and reproduce (2 pups? 3?)?
___________________________________________________________________________________________
Once you have your parameters set, you will need to create a data table and a graph. You will complete your data as you
go in order to see the relationship you have created with your parameters.
1. Create your data table on a separate sheet of paper.
2. Create your graph (fully labeled) (HINT: You will probably need two Y-axis).
3. Based on your data table and your graph, what is the independent variable in this simulation?
___________________. The dependent variable? ____________________________________
Names: ________________________________________________________ Pd. __________
You are now ready to complete the simulation.
a. Drop your starting number of mice into your ecosystem, this should be done randomly
b. Drop a coyote into your ecosystem. He has arrived via immigration.
c. Count the number of mice directly under the coyote. This is the number of mice he consumed.
d. Fill in your data table for the coyote and determine if the coyote was able to reproduce.
e. For every mouse that was not consumed, one offspring was produced (example – 25 mice were left
after the first generation, there would be 50 in the next).
f.
Fill in your data table for mice
g. Complete your graph
h. Repeat steps b-f for at least 15 generations.
i. If your coyote is unable to reproduce, or if at any time you drop to zero coyotes, bring 1 in for
the next generation through immigration.
ii. If the mice population drops to zero, start again with your initial number of mice.
i.
After 15 generations, analyze your data. If you do not see a pattern, change your parameters from the
last 15 generations and make a note of them below. Continue the lab for 15 more generations. If you do
see a pattern emerging, explain what you are seeing and continue for another 15 generations.
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
Attach your completed data table (30 generations/years) and completed graph (labeled and plotted). Show this to Mrs.
Gahan to get the analysis questions.
Names: ________________________________________________________ Pd. __________
Predator Prey Lab Analysis:
1. What do you predict would happen to your results if your system was disturbed by some unforeseen, outside
forces? To answer a and b, first draw the last cycle of your experimental graph free-hand. Continue to sketch the
graph for three additional cycles to display your prediction.
a. Explain what would happen if some coyotes died of disease or were hit by cars.
Sketch Graph Here:
Explain Your Prediction:
b. Explain what would happen to the prey populations in the event of a fire or the introduction of a new
predator population (like a red-tail hawk).
Sketch Graph Here:
Explain Your Prediction:
c. Does it matter at what point in your cycle the disturbance occurs? Explain why or why not.
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
2. Compare your data and graph to the others in the class.
a. Which parameters made the largest difference to your data? (size, number of prey, number of prey
required to reproduce, etc.)
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
Names: ________________________________________________________ Pd. __________
b. Predict why those parameters were so important to the simulation.
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
c. What parameters could we add or change in order to better model a natural system?
________________________________________________________________________________________
________________________________________________________________________________________
_______________________________________________________________________________
3. Describe the peaks and valleys of your data.
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
a. The peaks of the graph are described as Carrying Capacity in ecology. Define Carrying Capacity in your
own words. Complete a Marzano Template.
My Understanding
Word: CARRYING CAPACITY
____________
Definition:
_______________________________________________________________________________________________
_______________________________________________________________________________________________
_______________________________________________________________________________________________
Picture:
Connected Words or Ideas (At least 5)