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PopulusExercise1

# PopulusExercise1 - EEMB 120: INTRODUCTION TO POPULUS...

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Unformatted text preview: EEMB 120: INTRODUCTION TO POPULUS Download POPULUS and install it (links are on gauchospace). The aim of this exercise is to introduce you to working with simple population models. It will acquaint you with features of POPULUS, our primary modeling software for the class. You will also learn how to copy POPULUS output to WORD files for future reports. 1) Density independent growth of a closed population: continuous time formulation You will use the following density independent model to simulate population densities over time: Equation 1 N t = N 0e rt € where : N t is the population size at time t, N 0 is the initial population size, e ≈ 2.718, and r is the instantaneous per capita rate of growth. • Run the model twice in continuous mode for 20 generations. In your first run, use a positive value r, for the second choose a negative value (r<0). Copy the plot fo N vs. t to the clipboard (for windows by pressing Alt PrintScreen keys or on OS X press the control ­command ­shift ­4 simultaneously, click the spacebar and then click the window), then paste the plot into a WORD file). How does the value of r affect the form of your graph? Now plot ln(N) vs t for both values of r, and paste the plot into the WORD file. Estimate the slope of your graph (for the case of positive r) – just using change in y ­ value divided by change in x ­value. Comment on the result Density independent growth of a closed population: discrete time formulation Equation 2 N t = λt N 0 € • • • • 2) where : N t is the population size at time t, N 0 is the initial population size, and λ is the per capita rate of growth per unit time t . € Using the positive r ­value from above, calculate the value for λ . (Hint: λ = e r ) € • • • • 3) Run the model twice in discrete mode for 20 generations. In your first run, use a the value you calculated for λ , for the second choose a value less than 1 (0< λ <1) € Copy the plot for N vs. t to the clipboard as above. € How does the value of λ affect the form of your graph? Now plot ln(N) vs t for both values of λ , and paste the plot into the WORD file. € € Reporting € Post your word file to gauchospace € ...
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