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CIV220H1 20209 621603392210CIV220 Midterm Exam 2020 final.pd...
CIV220H1_20209_621603392210CIV220_Midterm_Exam_2020_final.pdf
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CIV220H1 20209 621603392210CIV220 Midterm Exam 202...
CIV220H1_20209_621603392210CIV220_Midterm_Exam_2020_final.pdf-NAME: ID: Page 1 of 7
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CIV220H1_20209_621603392210CIV220_Midterm_Exam_2020_final.pdf-NAME: ID: Page 1 of 7
Page 4
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ID:
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Question 3
A small ecosystem is represented by the food chain with energy symbols shown below.
All units are in kJ/m
2
.
(a)
If this ecosystem contains plants, deer, bears, and vultures, propose which organism is most
likely represented by which label in the above diagram.
[2]
A _______________
B ________________
C _________________
D _________________
(b) What is the Lindeman’s efficiency of
the B organisms, given by I
T
/I
T-1
, where I is the energy
input and T is the trophic level?
[4]
(c) Suppose this ecosystem is on the west coast where fires are raging, and they have an impact
such that A now absorbs 15
% less energy from the sun. What percentage of B’s energy must C
consume to keep C’s energy input equal to what it was befor
e the fires?
[4]
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Page 5 of 7
Question 4
(a) The presence of a band of coyotes has become a concern for residents of a local neighborhood.
Authorities decide to try to relocate some of them to a different location with what they think is an
appropriate ecosystem.
They manage to relocate 6 coyotes to a region with an expected carrying
capacity of 25 coyotes. Their normal birth rate is 3 coyotes/year and their average death rate is 1.5
coyotes/year.
How many coyotes are expected to be in the new area after 10 years?
[4]
(b) Assume that the food chain linking krill to whales is as follows:
Food Chain
Organism Mass
Organism Consumes
Krill
Minnow
5 g
62.5 g krill
Tuna
2000 g
150 kg minnows
Whales
2000 kg
2000 kg tuna
Assume that the minnows in this food chain are contaminated with mercury (Hg) at a
concentration of 0.050 mg of Hg/kg of minnow. Estimate the concentration of mercury in the
whales, assuming that no mercury is excreted by the minnows or tuna.
[3]
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Page 6 of 7
Question 5
(c) As shown in class, the Canada Lynx (L, a species of cat) thrives in remote areas of Canada and
preys on smaller mammals including Hare (H, a species of rabbit).
In a given 50 km
2
lynx habitat,
the following information may be used to model the populations of these predators and their prey:
Lynx growth rate on Hare:
f
H
.
a’
H
.
L
.
H
Lynx death rate:
q·L
Lynx migration rate into the area:
0
Lynx migration rate out of the area:
a
.
L
.
[b/(b+H)]
Hare growth rate:
r
.
H
Hare death rate:
a’
H
.
L
.
H
where:
L = Lynx population, H = hare population
f
H
,
a’
H
, q, r, K
H
, a and b are constants.
We have values for the following constants:
r = 2 hare·hare
-1
·yr
-1
,
a’
H
= 0.02 lynx
-1
·yr
-1
, f
H
= 0.005, q = 0.3 and K
H
= 5,000 hare
i.
Write out the organism balances (differential equations) for both lynx and hare.
[2]
ii.
Determine the lynx and hare populations at steady-state if the ecosystem becomes
isolated by increased human construction activity and migration becomes impossible.
[3]
iii. Is a true steady-state (constant populations of both species) strictly achievable in
predator-prey relationships? Explain briefly why this may or may not be possible, and
feel free to use a simple diagram to help illustrate if appropriate.
[2]
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