You will be using an Excel spreadsheet to simulate a population that experiences a severe bottleneck due to a temporary drop in the carrying capacity. There are two independent variables that you will be using; the per cent decline in the carrying capacity (80% to 95%) and the variablility in the carrying capacity (standard deviations of 10 to 25).
Open the link to the program (listed under Ecology Resources). Most of the options on this spread sheet you will not change; they include:
- Initial Numbers at 20
- Rate of Increase at 0.3
- Average Carrying Capacity at 200
- Duration of bottleneck at 10 generations
- Start of bottleneck at generation 50
Run the program with the constant variables listed above and the Stnd Dev of the Carrying Capacity set at 10 and the % decline of the carrying capacity set at 80%.
HINT: On some computers the F9 key will automatically recalulate the spread sheet for you!
Run the program 10 times at this setting. Each time observe in Graph 1 if the population has gone extinct or not. Record the number of extinctions in the 10 trials at this setting.
Leaving Stnd Dev at 10, repeat this experiment for % declines in carrying capacity set at 85, 90, and 95. Run 10 trials for each % decline and record your data.
You should have run the program 40 times at this point.
Repeat this process with Stnd Dev of Carry Capacity set at 20 and 25 each at % declines of 80, 85, 90, and 95.
Construct a table of your results. This table should show the number of times out of 10 trials the population went extinct at each of the 12 different combinations of Stnd Dev and % decline you used.
