Competition Lab
Purpose/Objective:
To determine what happens when two animal
species compete
Materials:
Graph Paper
Ruler
Procedure:
In 1973, there were no houses in a large, old
field. By 1988, there were 250 houses. A
biologist found a population of dusky field mice living in the field. The biologist
sampled this population from 1977 to 1992. Write a hypothesis about what you think
happened to the mouse population between 1977 and 1992.
1. Prepare a sheet of graph paper as follows. Mark the horizontal axis with the years
1977 to 1994. Label the horizontal axis “Years Sampled”
2. Mark the vertical axis from 0 to 90. Label the vertical axis “Size of Mouse
Population per 1000 Square Meters.”
3. Study the information in the table below
4. Plot the data for the field mouse population on the graph.
Year
1977
1978
1979
1980
Number of Mice
per 1000
Square Meters
89
85
82
79
Year
1981
1982
1983
1984
Number of Mice
per 1000 Square
Meters
78
51
48
42
Year
1985
1986
1987
1988
Number of Mice
per 1000 Square
Meters
47
45
36
29
Year
1989
1990
1991
1992
Number of Mice
per 1000 Square
Meters
26
17
14
7
5. Connect the data points with a ruler to make a line graph. Continue the line to
the right so you can estimate the size of the mouse population in 1994.
Data and Observations
1. Did the number of mice increase or decrease between 1977 and 1988?
2. Between which two years was the greatest change in population seen?
Analyze and Apply
1.
2.
3.
4.
5.
6.
7.
8.
9.
What limiting factors are affecting the population size of the dusky field mouse?
With what other living thing do you think these mice are competing?
What might be happening to the birthrate of mice?
Suppose in 1984, 17 mice emigrated. What do you think would happen to the mouse
population?
Predict what will happen to the number of mice in 1994.
List two factors that can increase the mouse population.
What effect would immigration have on the mouse population?
Check your hypothesis. Was your hypothesis supported by the data? Why or why not?
What happens when two animal species compete?
Extension
Design an experiment that would show how a limiting factor, such as the size of the
habitat, affects a plant population.