Potential Population Growth




BIO326 : Population : Population Dynamics : Potential Population Growth

Exercise: Potential Population Growth

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DUE: 18-Feb-2000. Work sent after this date will receive a grade of zero.

Be sure to work through the Lesson for this week before doing this exercise. The Lesson contains examples of these calculations.

1. In the life table activity for last week, the final value of lambda for the hypothetical population was 1.29 individuals/individual/time interval.

a) What is the equivalent value of r, the intrinsic rate of increase?

Suggestion: You will need to use natural logarithms and exponentials (i.e., raising e to a power) in this exercise. An easy way to calculate values for natural logarithms and exponentials is to use a spreadsheet on your computer, e.g., Excel, QuattroPro, etc.

For instance, in Excel open the spreadsheet and select (click on) a cell. On the tool bar, click on the function icon (f_x). Find the function, LN, and double click on it. A function wizard appears. Type the value 2, then type the Enter key. If you get 0.693147, you've used the function correctly.

Word to the wise: always check your work, like taking the natural log of 2 for which you know the answer, to be sure you're calculating answers the right way. Never put complete faith in technology.

Now you can repeat the process, entering 1.29 this time.

If you don't have access to a computer with a spreadsheet, use a calculator (or the calculator in your computer's Accessories) to calculate natural logarithms and exponentials.

b) On what page in the book is the formula for this conversion found?

c) How many time intervals will it take for this population to double?

2. Populations models are routinely used to predict changes in the human population.

a) What are the values of r and lambda for the county, state, and the United States between 1990 and 1998 from the Age Structure exercise from last week?

b) What formula of the exponential growth model did you use to calculate these growth rates?

3. Table 15.9 gives doubling times for several populations. What are the doubling times in years for the population densities of the county, state, and the United States based on population sizes in 1990 and 1998 from the Age Structure exercise last week?

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E-mail Professor Gaud at William.Gaud@nau.edu
or call (520) 523-7516