Name: _________________________________________   Period: _____  Date: ________________




Background:  Populations do not grow indefinitely.  Limiting factors keep them at or below the carrying capacity of the environment.  The interaction between the predator and prey maintains a balance in population sizes keeping the populations at or below carrying capacity.  Populations of predators and prey experience changes in their numbers over a period of years.  This fluctuation is dependent upon the size of the population of hare and lynx.  The interaction between the lynx and hare in Canada has been studied extensively. 


Purpose:  To simulate and see the effect of predator-prey interactions on population growth in an ecosystem.


Materials: (for each side of the lab station) 

            - 8 ˝ x 11 piece of cardstock paper (habitat)

            - 50 one-inch paper squares (snowshoe hares)

            - 16 three-inch cardboard squares (the Canadian Lynx)

            - Graph paper

            - Population data table



1.  The cardstock paper represents the habitat for the lynx (yellow cards) and hares (pink squares).  The lynx is the predator and the hare is the prey.


2.  The rules of the game are as follows:

Ř  The hares are always dispersed as far apart in the habitat as possible.

Ř  To survive and reproduce, the lynx must capture (land on or touch) three hares when tossed. 

Ř  Each time a lynx lands on three hares, one lynx offspring is produced.

Ř  A hare that is caught (under the lynx or in any way touching the lynx) is “eaten” and must be removed from the habitat.

Ř  The hare population doubles each generation.  To obtain this value, multiply the number hares remaining after the lynx has been tossed by two and record the value in the “Number of Hares” column in the next generation.

Ř  If no lynx survive a generation, a new one migrates into the habitat.

Ř  When more than one lynx are present in the population, each gets tossed individually.  Total their number of kills before calculating the hare population size for the next generation.


3.  We will begin the simulation with three hares and one lynx.  Place three hares on the habitat.  Spread them out as far as possible.


4.  Toss the lynx.  Any hare touched by the lynx is considered eaten.  Remember, a lynx must touch three hares to survive.  It is physically impossible for the lynx to land on all three hares because the hares are too far apart.  Thus there are zero lynx survivors and zero lynx offspring.  Determine the number of hares eaten and the number of surviving hares.  Record these in the data table.  Calculate the number of hares for generation 2 by multiplying the surviving hares from the first generation by two.  Record this under the “# of hares” column in generation 2.


5.  For generation two, assume a new lynx migrates into the habitat.  Place the appropriate number of hares in the habitat as far apart as possible.  Toss the lynx and record your data.


6.  Continue the simulation until you have gone through two complete cycles of population growth and population crash for the hare and lynx.  Once you have more then one lynx in the habitat, remember that each lynx gets one toss.  It is important to separately tally each lynx’s kills, removing captured hares after each lynx is tossed.  Keep track of the data for all the individual lynx and hares and record the total numbers for each generation on the table.


7.  After the first population growth and crash cycle, there may not be any hares left (due to predation by the lynx.  Start the following generation with three new hares that migrate into the habitat just like at the beginning of the game.  Thus there will always be at least three hares and one lynx on the board. 


8.  Stop when you have completed two cycles of population growth and crash for both hares and lynx.  You may or may not use all of the generations provided in the data table. 



The data will be best analyzed graphically.  You will be making a multiple line graph that will show the change in lynx and hare populations on the same graph. 


Ř  Population size will go on the Y-axis.  (Your intervals will range from zero to the highest number the hare population ever reached.  See column two on your data table; number of hares.)

Ř  Number of Generations will go on the x-axis.  (Your intervals will range from 1-25.)

Ř  Plot the hare data first.  You will be plotting the numbers in column two (# of hares.)  Connect each point with a colored pencil and ruler.

Ř  Next plot the lynx data.  (The numbers will come from column three on the data table # of lynx.)  Connect each point with a different colored pencil than used for the hares.


 Be sure to include appropriate labels, a key, and a title on your graph. 



Once your graph is complete, answer the analysis questions on the following page. 






















Data Table


# of Hares

# of Lynx

Hares Eaten

Hares Remaining

Lynx Starved

Lynx Remaining

Lynx Offspring





























































































































































































































Name: __________________________________________    Period: _____  Date: _______________





1.      Which organism represents the predator in this lab?  Which represents the prey?




2.  Look at your graph.  What pattern do you see occurring in the lynx and hare populations?






3.  How is the predator/prey relationship between the lynx and hare contributing to this pattern?  (Describe what is occurring between the two populations to make them rise in size or decrease in size.)






4.  Between which generations on your graph did the hares exhibit exponential growth?  What impact did this have on the lynx population a couple of generations later?  Why?






5.  During which generations on your graph did the hare population crash?  How did this effect the lynx population a couple generations later?  Why? 






6.  Is predation a density-independent or density-dependent limiting factor?  Why?






7.  Describe two other limiting factors that are dependent on the size of the population (aside from predation) that serve to reduce hare numbers when the population overshoots the carrying capacity of the environment.





8.  How do predator/prey relationships maintain homeostasis in ecosystems?