Biology 372, Fall 2014
General Ecology with Jesse Brunner
Name:________________________________
EXAM 4 Practice exam
Read questions carefully before answering. If you need clarification, just raise your hand.
For multiple choice and True/False questions, please circle the best answer.
For short answers, please write clearly and concisely. There is no need to repeat the
question in your answer, but please write in full sentences using proper grammar.
Limit your answers to the space available.
Where appropriate use diagrams to illustrate your answers.
Remember, you are taking an ecology test, so use the appropriate mechanisms, rules of
thumb, and always, always connect the logical dots for us.
Calculators are allowed. Smart phones or other “smart” devices are not allowed.
Potentially useful equations
(a)
€
N t = N 0λ
(b)
λ = N t+1 N t = exp(r )
(c)
dN
= rN
dt
€
€
t
(d)
(e)
€
⎛ N + α12 N 2 ⎞
dN1
= rN1⎜1 − 1
⎟,
(j) dt
K1
⎝
⎠
⎛ N + α 21N1 ⎞
dN 2
= rN 2 ⎜1 − 2
⎟
dt
K2
⎝
⎠
# N&
dN
= rN%1 − (
$ K'
dt
(k)
€
dP
= cP(1 − P) − eP
dt
(l)
R0 = SβL
(m)
pc > 1 −1/R0
(n)
NPP = GPP − Ra
NEP = GPP − Ra − Rh = GPP − Re
€
€ (f)
(g)
lx = n x /n 0
mx = bx /n x
€
R0 = ∑ lx mx
dN prey
= rN prey − aN prey N predators,
dt
dN predators
= abN prey N predators − mN predators
dt
€
€
€ (h)
(i)
€
T=
∑ xl m
x
x
R0
r = ln(R0 ) /T
€ (o)
€
€ (p)
€
€
CE = I NPP
AE = A I
PE = SP A
Residence time = Biomass/NPP
€
Page 1 of 6 NOTE: all True or False, or Multiple choice questions are worth 2pts
Q1: If you were to add nitrogen-rich fertilizer to a patch of Lupines on Mount Saint
Helens, which type of bacteria would be negatively affected?
a) N-fixing rhizobia
b) Nitrosomonas, Nitrobacter, and other nitrifying bacteria
c) Pseudomonas, Thiobacillus, and other denitrifying bacteria
Q2: Which of these abiotic factors has the largest (direct) role in determining where the
Nitrogen in nitrates (NO3-) in the soil ends up?
a) Temperature in the soil
b) Depth of leaf litter
c) Oxygen concentrations in the soil
Q3: Which of these biotic factors has the largest (direct) role in determining where
nitrates (NO3-) in the soil end up?
a) The successional stage of the community
b) The presence or absence of parasites or pests of the primary producers
c) The presence or absence of symbiotic bacteria such as rhizobia
Q4: True or False: Eltonian energy pyramids are never inverted
Q5: In addition to direct effects on reproduction of aquatic organisms (e.g., fish), acid
rain can lead to:
a) Large, anoxic dead zones
b) Aluminum toxicity (or toxicity from other metals)
c) Decreased assimilation efficiency
Q6a: You take two water samples from a nearby lake and place one in a clear bottle and
the other in a dark bottle. After 24 hours you measure the O2 in each bottle. The O2 in the
clear bottle has increased by 0.3 Mg/L while the dark bottle has decreased by 0.2 Mg/L.
In units of Mg O2 / L / Day, what are the following values? (2pts each)
GPP: 0.5 Mg/L/D
Re: 0.2 Mg/L/D
NEP: 0.3 Mg/L/D
Q6b: Is this a net autrotrophic or heterotrophic lake? (2pts) (Circle one)
Q6c: If this lake were subject to N & P inputs from runoff, would Re…
a) increase
b) decrease
c) stay the same
Page 2 of 6 ID#:___________________________________ Q7: Terrestrial primary producers (e.g., grasses & trees) require more structural elements
(e.g., cellulose & lignin) to hold themselves up than their aquatic counterparts (e.g.,
phytoplankton or kelp). They also tend to have more defensive compounds (e.g., tannins,
toxins) and structures (e.g., spikes). How would you expect these broad differences to
influence the following organismal, community, and ecosystem characteristics?
Draw the appropriate bar charts on the graphs on the left (2 pts each) AND to the right
provide a one-sentence explanation for each pattern you drew (3 pts each).
C:N in primary
producers
A. C:N in primary producers
Structural elements (lignin, cellulose, etc.) are high in C, so higher
C:N in trees than kelp
C:N in feces of
grazers
B. C:N in the feces of grazers
Grazers feeding on high C:N food will poop out excess/indigestible
C
% of NPP
bypassing
grazers
C. Percent of primary production bypassing grazer community
Inedible NPP (wood, branches, not to mention dropped leaves) go
straight to detrital pool.
Trophic transfer
efficiency
D. Trophic efficiency (PP  SP)
Since hardwood forests are less edible than kelp, less energy is
transferred to consumers (lower Consumption and Assimilation
efficiencies)
E. Food chain length
Kelp
forest
Hardwood
forest
Food chain
length
With less energy transferred/lower TE, less energy to support
higher trophic levels.
Page 3 of 6 Nitrate in stream
Primary
productivity
Q8a: Draw how NPP (top graph) in two wheat fields and nitrate concentrations in
streams draining those fields (bottom graph) changes with increasing concentrations of
fertilizer. Field A has just ammonia [solid line] as fertilizer while field B has Ammonia +
Phosphate [dashed line] for fertilizer. Assume a constant application of fertilizers (as
opposed to just dumping things on the field and walking away) (3pts each)
1)
2)
3)
4)
5)
6)
basic shape Dashed line plateaus higher than solid line Dashed line continues to increase after solid line has plateaud Should start flat since biotic demand is high Inflection points correspond to points where PP plateaus (above) Inflection point of dashed line further to the right of solid line Amount of fertilizer applied (kg/ha)
NH4+ (——) and NH4+ + H3PO4- (- - -)
Q8b: Briefly explain how and why the lines for the two types of fertilizers differ on these
graphs. Be sure to explain the ecological patterns or processes that lead to these
differences. (5pts)
Production increases with nutrient availability, but then levels off when the nutrient(s) in
question are no longer limiting (or available in excess). Productivity continues to increase
with the N&P fertilizer past where N-alone saturates because P was becoming limiting
when only N was added. Once the
Q8c: At what level of fertilization (low, medium, high) would you expect denitrifying
bacteria to thrive? (2pts) Why? (2pts)
At high levels. Because a) there is likely a great deal of excess nitrate (their “food”)
and/or b) because decomposition rates will tend to increase (or soil will become
impacted) making anoxic conditions in the soil, which is required for denitrification.
Page 4 of 6 ID#:___________________________________ Q9: From an ecosystem perspective, why are there so few large, toothy (i.e., top)
predators? (4pts)
Because of inefficient transfer of energy up the food chain (trophic transfer; 2pts) there is
simply not enough energy to support large populations of large predators at the top of the
food chain (2 pts)
Q10: If you were interested in feeding the human population in the most ecologically
efficient manner, what would you have us eat? (2pts) Why? (4pts) Where would you
grow it and why? (4pts)
Eating low on the food chain is generally best given inefficient trophic transfer
According to Dr. Oz, (www.doctoroz.com) “Mushrooms are nutritional powerhouses
packed with vitamins, minerals and disease-fighting antioxidants.” More importantly,
they are ~37% protein, which is pretty high for a non-animal. They are also ecologically
efficient to grow (i.e., they do not divert energy from other foods or farmland).
Growing seaweed is a good choice since it a) doesn’t have much in the way of structural
elements, so we can get more of its energy when we eat it. Growing it near the shore
makes the most sense since this is where nutrient upwellings occur (and b/c it is easier to
get to and harvest).
Q11a: In class we discussed how nutrient runoff from farms in the Midwest can lead to
dead zones in the Gulf of Mexico. Walk us through the logic of how nutrients cause dead
zones. (6 pts)
Nutrients  algal blooms / mass production  (optional: shade out plants below the
surface ) algae/plants die  decomposers flourish, but use up O2  anoxic conditions
are lethal
Q11b: Zooplankton (the primary grazer in the ocean) generally have a type II or III
functional response. If the zooplankton had a type I functional response instead, what
effect(s) would this have? (4pts)
If zooplankton’s predation rate kept pace with increasing production, very little of the
algae/plants would end up going directly to the decomposers, but would instead go up the
food chain, so no anoxic dead zone
Page 5 of 6 Q12a: Using the grid of dots above as a visual guide and the following quantities draw
the Sankey diagram (left to right) for the flow of energy through this headwater stream.
Assume that the stream is so nutrient poor that there is no photosynthesis. (Note: show
the numbers associated with each arrow/flow) (10pts)
o
Influx of leaf litter (allochthonous
o
energy in leaf litter flowing out of
inputs): 20
the stream: 10
o
Respiration of the shredders,
o
energy in the shredders’,
gatherers, and filterers: 1
gatherers’, and filterers’ poop: 6
Q12b: In this system, what are the values for:
(2pts each. Show your work)
Trophic transfer efficiency: 3/20 = 0.15
Detritivore production efficiency: 3/4 = 0.75
Consumption efficiency: 10/20 = 0.5
Bonus Q: What was your favorite part of this class and why? (2pts)
_________ / 100pts Page 6 of 6