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.

Hypothesis: ______

______

1.  Prepare a sheet of graph paper as follows. Label the horizontal axis “Years Sampled”

2.  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 / Number of Mice per 1000 Square Meters / Year / Number of Mice per 1000 Square Meters / Year / Number of Mice per 1000 Square Meters / Year / Number of Mice per 1000 Square Meters
1977 / 89 / 1981 / 78 / 1985 / 47 / 1989 / 26
1978 / 85 / 1982 / 51 / 1986 / 45 / 1990 / 17
1979 / 82 / 1983 / 48 / 1987 / 36 / 1991 / 14
1980 / 79 / 1984 / 42 / 1988 / 29 / 1992 / 7

5.  Plot the data on the chart and draw a best fit line with a ruler. 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.  What limiting factors are affecting the population size of the dusky field mouse?

2.  With what other living thing do you think these mice are competing?

3.  What might be happening to the birthrate of mice?

4.  Suppose in 1984, 17 mice emigrated. What do you think would happen to the mouse population?

5.  Predict what will happen to the number of mice in 1994.

6.  List two factors that can increase the mouse population.

7.  What effect would immigration have on the mouse population?

8.  Check your hypothesis. Was your hypothesis supported by the data? Why or why not?

9.  What happens when two animal species compete?