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Exponential and Logistic Growth
Excel file Population_Growth.xls ( Population Growth.xls
(55.0K)
) file models and graphs growth since 1950, based on actual data, exponential growth, and logistic growth. Review these growth patterns in your text, then experiment with growth rates as follows:
2. Click on the Census Data tab (bottom of sheet). What is the range of actual rates? How have they changed over time? 3. Now look at the logistic curve. The key difference here is that growth rate decreases as the population approaches K. Set r to 1.4. Set K to 100. Do the logistic and exponential curves differ much? Reduce K to 80, then to 60, 40, and 20. When does the logistic curve fall below the projected curve? As implemented here, is the carrying capacity an abrupt population ceiling, or is it a density-dependent growth control? 4. Enter what you think would be a reasonable carrying capacity. What number have you entered? What population does this produce in 2050? How much does your restricted population vary from the U.S. Census' projection? What does K mean for humans, as compared to other populations? |