Math Assignment: Population Dynamics, Assignments of Mathematics

Instructions for a graded assignment in a math course (math 464) focused on population dynamics. Students are required to write difference equations for population growth, find equilibrium solutions, generate graphs of population size over time using given data, and analyze the economic implications of harvesting animals from the population. The assignment also includes a section where students are asked to determine which population growth model best fits real-world data.

Typology: Assignments

Pre 2010

Uploaded on 08/19/2009

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Math 464, Graded Assignment 2
Notes on Exposition:
1. Write clearly and organize your work cleanly.
2. All graphs must be on graph paper or computer generated. All axes must be properly labeled
with units and descriptive names or variables.
3. If you use Excel or other software to generate data, turn in all the data.
4. You might want to write up the entire assignment as an Excel workbook. If so, I encourage
you to submit it by email to [email protected]
Part I.
Suppose that in a population of Nanimals we have the
following conditions (as represented in the diagram at
right.)
Birth rate is b= 0.07 per day per animal.
Death rate is d=N
1000 per day per animal.
h= 1 animal per day is removed from the popula-
tion.
bN
d
h
1. (10 pts.) Write a difference equation for N.
2. (10 pts.) Find all equilibrium solutions.
3. (10 pts.)
(a) Go to my website. Download the file under the link Random Numbers. (If you can’t
open Excel files, there is a second link for Text Only. If this doesn’t work, email me.)
(b) Under your name you will find two columns of 500 random numbers. These are dis-
tributed normally, with mean and standard deviation 1.
(c) Assume that N(0) = 50. Use your two columns of random numbers to compute three
new columns of data: number of births on each day; numbers of deaths on each day; and
N(t) on each day. Use the first column of random numbers for births and the second for
deaths. For both, use the normal approximation to the binomial distribution.
1
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Math 464, Graded Assignment 2

Notes on Exposition:

  1. Write clearly and organize your work cleanly.
  2. All graphs must be on graph paper or computer generated. All axes must be properly labeled with units and descriptive names or variables.
  3. If you use Excel or other software to generate data, turn in all the data.
  4. You might want to write up the entire assignment as an Excel workbook. If so, I encourage you to submit it by email to [email protected]

Part I. Suppose that in a population of N animals we have the following conditions (as represented in the diagram at right.)

  • Birth rate is b = 0.07 per day per animal.
  • Death rate is d =

N

per day per animal.

  • h = 1 animal per day is removed from the popula- tion.

b N

d

h

  1. (10 pts.) Write a difference equation for N.
  2. (10 pts.) Find all equilibrium solutions.
  3. (10 pts.)

(a) Go to my website. Download the file under the link Random Numbers. (If you can’t open Excel files, there is a second link for Text Only. If this doesn’t work, email me.) (b) Under your name you will find two columns of 500 random numbers. These are dis- tributed normally, with mean and standard deviation 1. (c) Assume that N(0) = 50. Use your two columns of random numbers to compute three new columns of data: number of births on each day; numbers of deaths on each day; and N(t) on each day. Use the first column of random numbers for births and the second for deaths. For both, use the normal approximation to the binomial distribution.

  1. (10 pts.) Graph your results for N(t) from t = 0 up to and including t = 500 days.
  2. (10 pts.) Suppose that you earn $1 for each animal you harvest, but you pay a (one time) fine of $10,000 if the population ever drops below 10 animals in the 500 day period. According to your solution to Problem 3, how much money did you make or lose? (Note that if the population is 0, you can’t harvest any more.)

Part II.

  1. (10 pts.) Suppose you start over with N(0) = 50 and a new set of random numbers for 500 days. Given the same deal as in Part I, Problem 5, do you expect to make or lose money? Why? [I expect a brief essay answer to this problem. You don’t need to turn in a lot of data, but if you run some trials I need you to describe what you did and what you learned doing it.]
  2. (10 pts.) Suppose that you could alter the number of animals harvested. You could, for example, set h = 0.5 animals per day. However, you cannot alter the economic conditions of $1 per animal harvested and a $10,000 fine if population drops below 10. Describe a harvesting plan that you think will make money. Your description must be good enough to for me to implement the plan using my own random numbers. Your grade on this problem will depend, in part, on how much money I make using your plan.

Part III. Actual observations of a population are shown in Sample Data (on the website; send email if you can’t download it.) Of the following three population models, which is most likely the correct model for this actual population? Your grade will be based on your justification of your choice.

∆N = 0. 002 N − 0. 00000025 N^2

∆N = 0. 004 N − 0. 00000050 N^2 − 3. 5

∆N = 0. 024 N − 0. 00000200 N^2 − 70. 0