Download Nt = Noλt Nt = Noert dN/dt = roN(1-N/K) dp/dt = cp(1

Ecology 203, Exam II. 3-17-03. Print name:_____________________________________
Rules: Read carefully, work accurately and efficiently. If you are concerned please leave marginal comments for me.
The test is worth 103 points.
Nt = Noλt
dN/dt = roN(1-N/K)
Nt = Noert
Ncaptured and marked initially = Nmarked at recapture
Ntotal
Ntotal recaptured
dp/dt = cp(1-p) – ep which suggests the equilibrium p = 1 – e/c
Nt+1 = Nt + roNt(1-Nt/K)
Multiple choice. (3 pts each; 45 pts total)
1. What is the doubling time of a population that grows from a starting population of 100 to 105 in just one
year?
a. 5.2 years
b. 10.7 years
c. 14.2 years
d. 16.6 years
e. 20 years
2. Which of the following is an assumption of the logistic growth model?
a. Populations are not limited by resources.
b. Populations are not limited by predators.
c. Population doubling time is independent of density.
d. Per capita population growth rate is linearly related to density.
e. All of the above are assumptions for logistic growth.
3. If you have collected data enabling you to build a life table for a species you can model the population using
a. only exponential growth.
b. only geometric growth.
c. only the Leslie matrix approach.
d. any one of the above modeling approaches – they’re all now available to you.
e. none of the above. You’ve only determine probabilities of extinction.
4. In the data from the Great
Barrier Reef in Australia shown
in the graph suggests
a. populations are regulated at
the scale of the “sector.”
b. populations change most at
the scale of the reef.
c. the abundance of corals is
highest at the small and
large scales.
d. all of the above.
e. none of the above.
5. Which of the below is not a
factor in regulating populations:
a. intrinsic abiotic.
b. extrinsic abiotic.
c. intrinsic biotic.
d. extrinsic biotic.
e. none of the above since all are not simultaneously possible.
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6. If a population’s birth rate (bo) is independent of density and death rate (do) is positively related to density
the population must be
a. growing.
b. decreasing.
c. in a stable equilibrium.
d. experiencing chaotic fluctuations.
e. we don’t know enough to determine this.
7. When “self-thinning” in plants takes place the population density [L; TB: 288-9]
a. goes down while average plant size increases.
b. goes down while average plant size decreases.
c. goes up while average plant size increases.
d. goes up while average plant size decreases.
e. all of the above can result from self-thinning.
8. Assume that a bird species around Geneseo functions as a metapopulation over this region and there are 200
habitats that could be occupied by this species. If the extinction rate from patches is 0.3 and the colonization
rate is 0.4 you should expect the equilibrium number of occupied patches to be [L; TB: 303]
a. 25.
b. 50.
c. 75.
d. 100.
e. 200.
9. The graph to the right suggests (L; TB 307]
a. populations increase over time.
b. populations decrease over time.
c. the probability of extinction increases with time.
d. the probability of extinction increases with N.
e. these populations are decreasing logistically.
10. The field guide suggests that birds flock for which of the
following reasons? [FG: 294-6]
a. Young birds can learn where food is from the older birds.
b. The food birds eat is usually concentrated so the birds are themselves concentrated in flocks.
c. It reduces predation rates because of increased vigilance by group members.
d. all of the above.
e. none of the above.
11. Your field guide discusses how bird populations occasionally reach very high levels, referred to as
“irruptions,” because [FG: 445-7]
a. food resources fluctuate.
b. birds have difficulty finding mates but sometimes have great success.
c. birds move about randomly and occasionally, due to chance, they will congregate.
d. all of the above.
e. none of the above.
12. The “ideal free distribution” was observed in the example of stickleback fish where feeding rates differed on
each side of the aquaria. The fish [L; TB: pg 261-2]
a. all ate food at a similar rate.
b. ate only the food items on their side of the aquaria.
c. shared the food cooperatively.
d. all of the above.
e. none of the above.
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13.
14.
15.
If a species occupies 20 patches and each patch has a likelihood of going extinct equal to 0.9 (90%
chance of each patch becoming empty in a single time step) the probability that the population will
persist one time step is
a.
0.02
b.
0.18
c.
0.22
d.
0.58
e.
0.88
Population ecology is best described as the study of
a.
groups of individuals.
b.
the dynamics of populations.
c.
how individuals change over time.
d.
how populations change over time and through space.
e.
how species change over time.
Andrewartha and Birch collected data on thrips populations and analyzed them using multiple
regression. Their results suggest that
a.
populations are not regulated.
b.
populations are regulated primarily by density-independent factors.
c.
populations are regulated primarily by density-dependent factors.
d.
all of the above.
e.
none of the above.
Short, precise answers. Choose 4 of 6. Use only the space provided. (10 pts each; 40 pts total)
1.
Analyze the graph on the left and provide a new graph of N vs. time on the right. Be sure to
fully explore all population sizes in the graph on the right (e.g., small and large values for N).
LABEL THE AXES.
dN/dt
O
N
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2.
You want to predict how two populations change over time. Species A grows with λ = 1.6
while species B grows with r = 0.6. If both start off with 100 individuals what will their
populations be over the next 5 years (note that we start at No and that you need to iterate these
up to N5)? Fill in the table. Please provide just one graph that shows both species on it. Be
accurate - use your calculator and clearly labeling your axes.
Year
0
1
2
3
4
5
3.
Species A
100
Species B
100
Provide a graph that you think best represents the Allee effect. Analyze the graph. [L; TB: 290]
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4.
Provide two graphs. First, provide a graph of the relationship of dN/Ndt to N for one
population. Second, provide a graph of the relationship of dN/Ndt as a function of body size for
organisms in general.
5.
Draw a map in the box below of the dispersion pattern for a single population that is random,
uniform, and clumped at different scales. Please provide dots that indicate the location of each
individual. Indicate where the three patterns exist in your single map.
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6.
You wish to estimate the population of eastern cottontails in the Arboretum. You decide to use
the Lincoln-Peterson mark-recapture method you learned in Ecology 203. You set up bunny
traps in open patches, catch 50, mark them with yellow paint, and release them. One week later
you trap bunnies in a similar way and catch 70, 25 of which are marked.
a.
What is your estimate of the bunny population in the Arboretum?
6b.
On the day of your second sampling it turns out there is very popular bunny conference
on predator avoidance, held in the Arboretum. Bunnies still randomly get trapped such
that the number of marked bunnies is half of what it would have been had the
conference not been held. Numerically, how does this affect your estimate of the
population?
Mandatory question. Use only the space provided. (15 pts)
These questions are based on the following diagram: (15 pts total)
1.
Provide the Leslie matrix for the figure (5 pts):
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2.
Using your Leslie matrix from above, calculate the population at time step 2 (t2) if at time step
0 (t0) there are 100 babies, 50 juveniles, and 25 adults. Show your work. (3 pts)
3.
How should you determine λ for the above population? (3 pts)
4.
Using the population growth in question #2 above: (2 pts)
λ = ________ (show your work).
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5.
Assuming from #4 above that you have your λ (use 1.5 if you haven’t been able to deterimne λ)
and your initial population is defined as in #2 above, determine what the population would be
in time step 2 assuming the population grows according to geometric growth. (show your work)
(3 pts)
6.
Discuss the relationship between your estimates of the population at time step 2 using both the
Leslie matrix and the geometric growth models. (2 pts)
EXTRA CREDIT
1.
What are the four, easily observed characteristics of natural selection? (4 pts)
a.
b.
c.
d.
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