Download Predator vs. Prey Lab

Name________________________________________________________________________________________Period________
Predator vs. Prey Lab
Introduction:
Predation is an example of a biotic factor that influences the size of a population and also demonstrates one of the types of relationships
found within a community. Predation is an interaction between species in which one species (the predator) uses another species as food
(the prey). Predation often leads to an increase in the population size of the predator and a decrease in the population size of the prey.
However, if the size of a prey population gets too small, many of the predators may not have enough food to eat and will die. As a result,
the predator population size and the population size of its prey are linked. The sizes of a predator population and a prey population often
cycle over several generations (see the figure below, “A stable predator-prey population size relationship”), and this cyclic pattern is
often described as a predator-prey population size relationship. A predator-prey population size relationship that results in both
populations surviving over time, despite fluctuations in the size of each one over several generations, is described as stable. In this lab
you will simulate the population dynamics of rabbits and foxes in an ecosystem.Your data will be organized and graphed from the
simulation, predicting the future population over several generations.
Prelab Questions:
1. What is carrying capacity? What do you think will determine the rabbits carrying capacity?
2. Define oscillating growth:
3. What type of factors could alter the foxes population size in this lab or in real life?
Objective: What is the objective of this lab?
Procedure:
Generation 1
1. Populate the “meadow” with three rabbits; spread them out all over your desktop.
2. Toss the fox into the area trying to capture (i.e. land on any portion of) as many rabbits as possible,
The fox must capture at least three rabbits when tossed in order to survive and reproduce (With the rabbit population at
this stage fox survival is virtually impossible. Remove any rabbit captured and enter the tallies for the first generation).
3. Enter the data
a) Enter the number of rabbits captured and remove them from desktop
b) Enter the number of rabbits surviving.
c) Enter the number of rabbits offspring: double (2x) the number of rabbits surviving.
d) If the fox caught all three rabbits, put 0 for foxes starved…If the fox caught 2 or less rabbits, put 1.
e) If the fox caught all three rabbits, put 1 for foxes surviving…If the fox caught 2 or less rabbits, put 0.
f) Enter number fox offspring: one offspring for every three rabbits captured.
Generation 2
1. Repopulate the table with rabbits according to the number of rabbit offspring from the last generation. If less than 3
rabbits at the start of a generation, add rabbit(s)to give a total count of 3 (they “immigrate”).
2. Use the population of foxes the survived the last generation plus their offspring for this generation. If no foxes
survived the previous generation another one “immigrates” to the area.
3. Toss a fox and remove it along with the rabbits it “captures”. Repeat with all foxes, record data.
Generation 3 - 20
After completing the data for generation 2 continue with repopulations and tosses, carefully recording data each
generation.
Note: The carrying capacity of our experimental meadow is 100 rabbits
Important notes
➢ By generation 5 the fox should be able to capture three rabbits when tossed. If successful, the fox survives until the
next generation and also produces offspring, one per each three rabbits captured. Toss the fox square once for each
fox.
➢ As the population builds, it is important to separately tally each fox’s kills, removing captured rabbits after each fox
is tossed. Determine fox survival and reproduction using individual fox capture numbers. Remember, fox produce
one offspring for each three rabbits captured. If a fox captures seven rabbits, three foxes enter the next generationthe original fox and two offspring. Individual fox capture numbers should be tallied on a separate sheet of paper and
only the totals entered in the table.
➢ REMEMBER! If the populations crash back to or near zero, start subsequent generations with at least three rabbits
and one fox.
Data:
Name________________________________________________________________________________________Period________
# of rabbits
# of foxes
3
1
Generations
1
Rabbits
captured
Rabbits
surviving
Rabbit
offspring
Rabbits
Starved
Foxes
starved
Foxes
surviving
Fox
Offspring
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Graph: Using the following graph paper; prepare a line graph of the rabbit and fox populations over the 20
generations.
Name________________________________________________________________________________________Period________
Analysis: Answer in complete sentences
1. Describe what happens to the rabbit population over time.
2. Describe what happens to the fox population over time.
3. How did both of these populations influence each other?
4. What would have happened if a whole new family of foxes immigrated into the ecosystem at generation 2?
Name________________________________________________________________________________________Period________
5. Make a prediction about what would happen to both your predator and prey populations if a new predator is
added to the system? Explain any new types of relationships established.
6. Explain how this simulation models a real ecosystem. Also explain how you could change the lab procedure
to make it more realistic.