Answer Key
BIO 340 General Ecology
Take Home Exercise 1: Population Ecology
Due: In class on 30 Oct 2006
Worth 10 exam points
Please show all work when answering the following questions on your attached answer sheet(s).
1) As an ecologist, you collected data on the size of a population of sharp-tailed grouse
(Tympanuchus phasianellus) in the eastern Upper Peninsula of Michigan. Data were counts
taken on 1 April each year.
Year
1999
2000
N
340
282
a) What is the annual finite rate of change for this population over the period from 1999
to 2000? (2 points)
λ = N1/N0 = 282/340 = 0.829 = 0.83
b) Given all the available information, how many grouse will there be in 2007? (2 points)
t = 2007 = 8
λ = 0.83
Nt = N0 λt
N8 = 340 (0.83)8 = 76 grouse
2) Given the following life and fecundity table for gray squirrels (Sciurus carolinensis):
Age Class,
years (x)
0.5
1.5
2.5
3.5
4.5
5.5
6.5
7.5
Number
Alive
530
134
56
39
23
12
5
0
Number that
Died
396
78
17
16
11
7
5
0
Survivorship
(lx)
1.0
0.253
0.106
0.074
0.043
0.023
0.009
0
Fertility
(mx)
0.05
1.28
2.28
2.28
2.28
2.28
2.28
0
lxmx
x lxmx
0.05
0.324
0.241
0.168
0.099
0.052
0.022
0
0.025
0.485
0.602
0.587
0.445
0.284
0.140
0
a) Complete the Survivorship column and the lxmx and x lxmx columns (2 points).
b) What is the net reproductive rate? Remember to use units. (2 points)
R0 = Σlxmx = 0.954 = 0.95 squirrels per female
c) What is the generation time? Remember to use units. (2 points)
T = Σx(lxmx) / R0 = 2.57/0.95 = 2.7 years