Practice Problems: Population Growth
Environmental Biology: Leege
1. The Resource Manager of Tybee Island calls you in to do an assessment of the deer population there. It turns out that the vegetation has been severely damaged by deer in recent years and she cannot support the decision to allow deer hunting unless she has proof that the deer populations are increasing. You collect the following information during a one year period (2005): of the 1,000 deer on the island, 120 deer die, 200 deer are born, 20 immigrate via the causeway connecting the island to Savannah, and 10 emigrate via the causeway.
____a. Calculate the population growth rate. Write it as a percent. Show your work.
____b. Calculate the doubling time for the deer population. Show your work.
____c. Based upon the data you have collected for 2005, you instruct the resource manager that :
A. She can open the island for a deer hunting season
B. Deer populations are decreasing on their own, therefore she cannot allow a hunt
C. Deer populations are not getting either larger or smaller, therefore she must assess the issue again next year
D. The data you have collected cannot help you to inform the resource manager
2. Georgia farmers have complained that armadillos are becoming more common in the area. You want to find out if there is some truth to this statement. You set armadillo traps all over Bulloch County and find that the population of armadillos is approximately 2,000 for the county. Over the course of the next year, you determine that 300 armadillos are born, 290 die, 100 immigrate from the south and 90 emigrate northwards.
____a. Is the farmers' statement true for Bulloch county? Explain.
____b. What is the doubling time for armadillos in Bulloch county? Show your work.
3. Examine the following scenarios. Label with the correct type of population regulation.
A. Density Dependent Factor
B. Density Independent Factor
_____ a. A tornado in Alabama wipes out a population of pine trees in a plantation. How is this population regulated?
_____ b. A pair of American kestrels (birds) is unable to lay eggs because all the nesting sites have already been occupied by other kestrels. How is this population regulated?
_____ c. A pack of lions take down five zebras from a large herd. How is the zebra population regulated?
ANSWERS
1a. r = (b-d+i-e)/N
r = (200-120+20-10)/1000
r = 90/1000
r = 0.09 = 9%
1b. td = 70/r
td= 70/9
td = 7.78 years
1c. A
2a. r = (b-d+i-e)/N
r = (300-290+100-90)/2000
r = 20/2000
r = 0.01 = 1%
yes, the population is increasing by 1% each year
2b. td = 70/r
td= 70/1
td = 70 years
3a. B
3b. A
3c. A