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Bio 3SS3
Version Q
1. A scientist introduces a few thousand unknown bacteria into a large container whose
nutrients and conditions may or may not be suitable for growth. She does not expect
density dependence to be a factor over the course of the experiment. She should expect
the population to show:
A. Linear increase
B. Either linear increase or decrease
C. Exponential increase
D. Either exponential increase or decrease
E. Linear or exponential increase or decrease
2. What is 103 m ?
A. 1000 m
B. 1000 m3
C. Complete nonsense
D. The answer depends on context
Use this information for the next two questions. Some bacteria in a flask have run out
of food and gone into a slower state. They are not reproducing, and are dying at a per
capita rate of 0.02/ day.
3. What is the basic reproductive number R for this population under these conditions?
A. -0.02/day
B. -0.02
C. 0
D. 0.02
E. 0.02/day
4. If the bacteria start with a density of 1000/ml, what is their density after 50 days?
A. 0
B. 368/ml
C. 500/ml
D. 693/ml
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Bio 3SS3
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5. A scientist wants to model a population of small perennial plants (ie., plants that
reproduce more than once) with a simple population model (ie., without population
structure). He should:
150
100
50
Total number
200
A. Use a conceptual model with a census before reproduction
B. Use a conceptual model with a census after reproduction
C. Use a conceptual model with one census before reproduction and one census
after reproduction
D. Not even try to do this
0
Fecundity
Mortality
0
20
40
60
80
100
Population size
The figure above shows the assumptions made for a discrete-time birth-death model.
Use it for the next 3 questions.
6. The figure shows:
A. Density dependence in mortality only
B. Density dependence in both mortality and fecundity
C. An Allee effect in mortality only
D. An Allee effect in both mortality and fecundity
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7. Which of the four pictures below was generated by the same model as the picture
above?
1.5
1.0
Per capita number
1.0
0.0
0.5
40
60
80
100
0
20
40
60
Population size
C
D
2.0
Population size
100
1.0
1.5
Fecundity
Mortality
0.0
0.0
0.5
1.0
Per capita number
1.5
Fecundity
Mortality
80
0.5
20
2.0
0
Per capita number
Fecundity
Mortality
0.5
1.5
Fecundity
Mortality
0.0
Per capita number
2.0
B
2.0
A
0
20
40
60
Population size
80
100
0
20
40
60
80
100
Population size
8. A population following this model will:
A. Increase exponentially without limit
B. Decrease exponentially to zero
C. Approach an intermediate equilibrium
D. Decrease to zero if started near zero, and increase to an intermediate equilibrium
otherwise
9. My favorite lake has no trout, but nearby lakes with similar conditions and similar
weather do. I introduce a pair of adult trout to my lake in a year when the trout in
the nearby lakes are doing well, but my trout fail to establish a population (they go
locally extinct in my lake). This is likely due to:
A. Allee effects
B. Either Allee effects or environmental stochasticity
C. Either Allee effects or demographic stochasticity
D. Either environmental stochasticity or demographic stochasticity
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10. When an adult tree dies and falls in a certain pine forest, the seedlings that were
already present and struggling for light in the area beneath it compete to grow tallest
and take over the space. Eventually one of the seedlings wins and takes over the spot.
This is an example of:
0.5
A. Contest competition that is a likely explanation for population cycles
B. Contest competition that is not a likely explanation for population cycles
C. Scramble competition that is a likely explanation for population cycles
D. Scramble competition that is not a likely explanation for population cycles
●
●
0.4
●
●
0.3
●
●
0.2
●
●
0.0
0.1
Annual survival
●
●
2
4
6
8
10
Age
Use the picture above for the following 2 questions.
11. What does this picture of survivorship in an idealized age-structured population
indicate about mortality in this population?
A. Mortality is constant
B. Mortality is elevated in older individuals
C. Mortality is elevated in younger individuals
D. Mortality is elevated in both older and younger individuals
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12. The pictures below show cumulative survival. Which one corresponds to the picture
shown above?
4
6
8
10
2
4
6
Age
C
D
10
8
10
1e−03
1e−05
Cumulative survival
8
1e−01
Age
1e−04 1e−03 1e−02 1e−01 1e+00
2
Cumulative survival
1e−02
1e−04
0.010
0.050
Cumulative survival
0.500
1e+00
B
0.002
Cumulative survival
A
2
4
6
8
Age
10
2
4
6
Age
13. A population of pine trees is declining exponentially with reproductive number
R = 0.5. The trees live about 100 years on average. If we calculate the finite rate of
increase λ using a time step of ∆t = 1 year, we expect that
A. λ is 0.5
B. λ is close to 0.5
C. λ is close to 1
D. λ is 1
Use the following information for the next three questions. An ecologist censuses a
gopher population before reproduction, and finds the following. Females observed in
their first year produce an average of 1 female that will be observed next year, and have
a 40% chance of surviving until their second year. Females observed in their second
year produce an average of 2 females that will be observed the next year. No femailes
survive from their second year to reproduce again.
14. What is the value of `1 in this population?
A. 0.2
B. 0.4
C. 0.8
D. 1
E. 1.2
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15. What is the value of f2 in this population?
A. 0.4
B. 0.8
C. 1
D. 1.2
E. 2
16. Which of the following is a true statement about this population?
A. λ = 1.4
B. R = 1.4
C. λ = 1.8
D. R = 1.8
17. It is hard to estimate the importance of old individuals to population growth in
many populations because, in these populations:
A. They have high values of both p and f
B. They have low values of p and high values of f
C. They have high values of both ` and f
D. They have low values of ` and high values of f
18. Which of the following is not an example of a tradoff?
A. Birds with heavier beaks have higher mortality before reaching maturity
B. Bushes which survive better in dry conditions grow more slowly in wet conditions
C. Trees grown in full sunlight grow faster and have more resistance to diseases
D. Rabbits which need less food to survive produce fewer offspring when food is
plentiful
19. We expect dominance to occur when
A. Each species does better in an environment dominated by conspecifics than it
does in an environment dominated by the other species
B. Each species does better in an environment dominated by the other species than
it does in an environment dominated by conspecifics
C. One species does relatively better in an environment dominated by conspecifics,
while the other does relatively better in an environment dominated by the other species
D. One species does better than the other in an environment dominated by either
species
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20. Cole’s paradox suggests that, from a population biology point of view, it is a
mystery why some plants:
A. Reproduce only once
B. Reproduce many times
C. Produce a large number of small seeds
D. Produce a small number of large seeds
21. Which of the following is not a possible advantage of producing fewer offspring
with the same amount of energy?
A. Greater ability to help offspring survive
B. Greater ability to help offspring disperse
C. Greater ability to produce high-quality offspring
D. More energy left over to produce offspring in future years
22. Which of the following traits is not typically associated with r strategies?
A. Fast life cycle
B. Efficient resource use
C. Relatively small investment per offspring
D. Relatively large investment in dispersal
23. Which of the following arguments for the importance of “bet-hedging” strategies
is correct?
A. Averaging within generations is better than averaging between generations,
because the geometric mean is larger than the arithmetic mean
B. Averaging within generations is better than averaging between generations, because the arithmetic mean is larger than the geometric mean
C. Averaging between generations is better than averaging within generations, because the geometric mean is larger than the arithmetic mean
D. Averaging between generations is better than averaging within generations,
because the arithmetic mean is larger than the geometric mean
24. A population meets the assumptions of the balance argument for sexual allocation.
If the population has more females than males at birth, this means:
A. Total investment of resources in producing females is higher than total investment of resources in producing males
B. Total investment of resources in producing males is higher than total investment
of resources in producing females
C. Per-offspring investment of resources in producing females is higher than peroffspring investment of resources in producing males
D. Per-offspring investment of resources in producing males is higher than peroffspring investment of resources in producing females
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Bio 3SS3
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25. In a certain environment, algal species compete primarily for light in small pools,
which may be disturbed. If the disturbance rate is very low, which species would we
expect to dominate?
A. The species with the highest growth rate at high light (rmax )
B. The species with the lowest rmax
C. The species with the highest light level at which it reaches equilibrium
D. The species with the lowest light level at which it reaches equilibrium
1
26. The growth rate of species 1 in the presence of species 2 is given by dN
= r(N1 +
dt
α21 N2 )N1 . If species 1 is counted in units of indiv1 , species 2 in units of indiv2 , and
time is counted in units of years, then the value of the function r(N1 + α21 N2 ):
A. Has units of 1/ year
B. Has units of 1/ indiv2
C. Has units of indiv1 / indiv2
D. Has units of indiv1 / year
27. The range where red squirrels live has shrunk dramatically in recent decades. If it
is true that this is due only to competition from grey squirrels, we can conclude that
due to the introduction of grey squirrels:
A. The realized and fundamental niches of red squirrels are smaller than before
B. The realized niche of red squirrels is smaller than before, but the fundamental
niche is unchanged
C. The fundamental niche of red squirrels is smaller than before, but the realized
niche is unchanged
D. The realized and fundamental niches of red squirrels are unchanged
28. “Neutral” biodiversity may arise because
A. The competitive exclusion principle does not apply to similar species
B. Species may not exclude each other because of allocation tradeoffs
C. Species may not exclude each other because of resource tradeoffs
D. The process of neutral extinction may be slow enough to be balanced by the
process of speciation
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50
100
150
●
●
●
●
●
0
Species 2 density (indiv/m sq)
200
Bio 3SS3
0
20
40
60
80
Species 1 density (indiv/m sq)
Use the picture above for the next 3 questions. These are plots from a simple model
of two competing species.
29. The picture shows:
A. Dominance by species 1
B. Dominance by species 2
C. Mutual exclusion
D. Coexistence
200
100
30. Which of the time plots below matches the middle path from the phase plot above?
Species 1
Species 2
150
100
Population density (indiv/m sq)
50
60
40
0
0
20
Population density (indiv/m sq)
80
Species 1
Species 2
0
10
20
30
40
0
10
30
40
30
40
Species 1
Species 2
60
40
0
20
20
40
60
80
Population density (indiv/m sq)
80
100
Species 1
Species 2
0
Population density (indiv/m sq)
20
Time (years)
100
120
Time (years)
0
20
40
Time (years)
60
80
0
10
20
Time (years)
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Bio 3SS3
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31. If E12 is the competitive effect of species 1 on species 2 (and vice verse), what can
you say about the values of E in this system?
A. Both E12 and E21 are > 1.
B. Both E12 and E21 are < 1.
C. E12 but not E21 is > 1.
D. E21 but not E12 is > 1.
E. There is not enough information to choose one of these answers.
32. Predator satiation refers to the phenomenon that:
A. The per capita rate at which prey get eaten goes down as the number of predators
goes up
B. The per capita rate at which predators eat goes down as the number of predators
goes up
C. The per capita rate at which prey get eaten goes down as the number of prey
goes up
D. The per capita rate at which predators eat goes down as the number of prey
goes up
33. A population of grouse and a population of foxes are at equilibrium under reciprocal
control – ie., the grouse population is primarily controlled by fox predation, and the
fox population is primarily controlled by the food supply of grouse. Fox hunting is
now introduced to the area, with the idea that this will increase the number of grouse.
Based on reciprocal control alone, what effect would you expect to see in long term
equilibrium populations?
2.0
2.5
A. The equilibrium number of grouse will increase, but the equilibrium number of
foxes will stay about the same
B. The equilibrium number of foxes will decrease, but the equilibrium number of
grouse will stay about the same
C. The equilibrium number of foxes will decrease, and the equilibrium number of
grouse will increase
D. The equilibrium number of foxes and grouse will both decrease
1.0
Exploiter
1.5
●
0.0
0.5
●
0
2
4
6
8
Resource
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Bio 3SS3
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Use the picture above for the next 3 questions. This is a phase plot showing several
orbits from a predator-prey system.
34. The figure above shows:
A. Unstable oscillations
B. Neutral oscillations
C. Persistent oscillations
D. Damped oscillations
35. This figure is consistent with a simple model that has reciprocal control and:
A. No prey density dependence and no predator satiation
B. Prey density dependence and no predator satiation
C. Predator satiation and no prey density dependence
D. Both prey density dependence and predator satiation
36. If we were to add predator density dependence to this model, the qualitative behaviour (type of cycles) would:
A. Stay the same
B. Change to unstable oscillations
C. Change to neutral oscillations
D. Change to persistent oscillations
E. Change to damped oscillations
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37. Resource-exploiter systems have an intrinsic tendency to oscillate because:
A. Each species has a direct, positive effect on its own growth rate
B. Each species has an indirect, positive effect on its own growth rate
C. Each species has a direct, negative effect on its own growth rate
D. Each species has an indirect, negative effect on its own growth rate
20
Per capita rate (1/t)
15
birth rate
death rate
10
5
0
0
25
50
75
100
Population size (number)
Use the figure above for the next three questions. In the questions, N means the
population size.
38. What are all the equilibria of this system?
A. A stable equilibrium at N = 0
B. An unstable equilibrium at N = 0 and a stable equilibrium at N ≈ 50
C. A stable equilibrium at N = 0 and an unstable equilibrium at N ≈ 50
D. The system does not have an equilibrium
E. An unstable equilibrium at N = 0
39. Given that this is a deterministic, discrete-time system, the population will
A. Decrease exponentially
B. Increase exponentially
C. Eventually reach a population size of N ≈ 50, unless it starts at N = 0
D. Eventually reach a population size of N ≈ 50, regardless of where it starts
E. Increase in size, regardless of where it starts
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Bio 3SS3
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40. The absolute death rate of this population
A. Is constant
B. Increases linearly with population size
C. Increases exponentially with population size
D. Decreases exponentially with population size
E. Not enough information to say
c
2010–2015
by Jonathan Dushoff and the 3SS teaching team. May be reproduced and distributed, with this notice, for non-commercial purposes only.
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