AEC360 Exam 2 Key
(Questions are identical in Code 16, but in a different order)

Multiple Choice Questions (2 pts each)
1. How do Monarch butterflies find their way from Canada to Central Mexico each fall?
A. Time-compensated sun compass
B. Memory, returning to where they were born
C. Magnetic compass orientation
D. All of the above

2. Since 1995, monarch population sizes have:
A. declined by more than 75%
B. declined by less than 25%
C. not changed in size
D. increased by less than 25%
E. increased by more than 75%

3. For which of the following organisms does capsaicin, the active ingredient in hot chilies, have NO effect in reducing consumption?
A. Fusarium, a fungal pathogen
B. Packrat
C. Cactus mouse
D. Curve-billed Thrasher

4. In Bolivia, the same species of chili can vary from intensely hot to not hot at all (high to low capsaicin). The pattern of higher “heat” in chilies was directly related to the abundance of what species?
A. Curve-billed Thrasher
B. Packrat
C. Cactus mouse
D. Acroleucus coxalis, a seed bug

5. In population ecology, scientists track the rate of change in populations by measuring additions to the population such as ________ and subtractions from the population such as _____________.
A. immigration, birth
B. emigration, death
C. death, birth
D. immigration, death
E. emigration, immigration

6. Last summer, Dr. Haddad caught and marked 40 St. Francis’ satyr butterflies. The next day, he captured 40 more butterflies, of which 20 were marked. The size of this butterfly population was:
A. 40
B. 60
C. 80
D. 100

7. Which of the following equations is used to project population size through time, under conditions of unlimited, geometric (or discrete) population growth?
A. N(t) = N(0)e^rt      
B. N(t) = N(0)*lambda^t
C. dN/dt = rN
D. lambda = e^r
E. r = b - d

8. If you measure the size of a chickadee population in three consecutive years, and its population size in year 1 is 1214, in year 2 is 1214, and year 3 is 1214, what is its geometric rate of increase?
A. 0
B. 0.15
C. 1.0
D. 1.50
E. 150

9. Although exponential population growth cannot occur indefinitely, it can be observed for short periods of time in populations:
A. that are newly introduced invasive species expanding beyond their native range
B. that are very small and are released from the limits (hunting, habitat loss) that have reduced their population size
C. of humans following 1700, due to large changes in technologies and behaviors
D. All of the above

10. In a life table, the first value in the survivorship column (labeled lx) is 1.000 because:
A. all newborn individuals are, by definition, alive at age 0.
B. all individuals are, by definition, alive at age 1.
C. the individuals tracked by a life table are, by definition, immortal.
D. this is the point in the life table where fecundity is greatest.

11. Life tables revealed that conservation was important for which stage of the life history of loggerhead sea turtles?
A. Eggs
B. Hatchlings on their way from nests to the sea
C. Subadults

12. Human demography is best represented by which type of Survivorship Curve?
A. Type I
B. Type II
C. Type III
D. Type IIII
E. All of the above

13. A life table:
A. Summaries demography by age
B. Summarizes demography by size
C. Provides information that can be used to calculate population growth
D. Permits study of how stage at one age, stage, or size affects population growth
E. Any of the above

14. For a bird that can live for eight years, in what year will a change in survivorship have the greatest impact on per capita growth rate? Consider the amount of change to be 15% at any year.
A. first
B. third
C. fifth
D. eighth
E. cannot be determined

15. How many stages are there in the human demographic transition?
A. one
B. two
C. three
D. four
E. ten

16. In which stage of the human demographic transition is the population size growing?
A. one
B. two and three
C. four

17. The current human population size on Earth is closest to which number?
A. 2 billion people
B. 4 billion people
C. 7 billion people
D. 11 billion people
E. 111 billion people

18. The human fertility rate is reduced when
A. wealth increases
B. education increases
C. contraceptive use increases
D. rates of disease decrease
E. All of the above

19. When a population grows according to the density-dependent (logistic) model, what is the value of r0 when the population is stable?
A.  K
B.  0
C.  N

20. Which of the lines in the graph to the right is characteristic of exponential (that is, density-independent) population growth?
Answer is B

21. The influence on individuals within a population that is not related to the degree of crowding defines:
A. fluctuation population regulation
B. density independent population regulation
C. density dependent population regulation
D. population regulation with set limits (carrying capacity)

22. When there are options for habitat conservation that would each occupy the same amount of habitat, which strategy would not be recommended:
A. conserve several small areas that are spread out across the landscape
B. conserve one large area that forms a bigger habitat for plants and animals
C. conserve several small areas that are clustered closer together
D. connect habitats with corridors

23. For both shrews and butterflies that were discussed in class and in your book, population size (measured as whether patches are occupied) was higher if:
A. Fragments were larger
B. Fragments were smaller
C. Fragments were more isolated
D. Fragments were less isolated
E. Fragments are larger and less isolated

24. In conservation of a metapopulation, which is critical to maintain a population?
A. Occupied fragments only
B. Unoccupied fragments only
C. Both occupied and unoccupied fragments
D. Neither occupied nor unoccupied fragments

25. In the absence of natural selection, genetic drift will cause alleles to become fixed or lost in the population (s) of which size?
A. 4
B. 40
C. 400
D. 4000
E. All of the above

26. Effective population size (Ne) is almost always lower than actual population size (N) because, for example:
A. sex ratios are equal
B. breeding systems are typically monogamous
C. family sizes vary, with some parents contributing more offspring
D. environmental conditions are constant

27. Why are cheetahs an example of how low genetic diversity does not necessarily mean the population is headed for extinction?
A. While the genetic diversity continues to decline, there is no evidence of inbreeding depression
B. The genetic diversity, while low, is not declining in part because females mate with many males
C. They evolved with low genetic diversity to begin with, so they have adapted to it.
D. None of the above   

28. What conservation approaches are used to counteract the effects of low genetic diversity?
A. discourage rapid growth after a population decline, to give more time for recovery
B. limit mixing of populations
C. maintain large population sizes
D. Both A and B
E. Both A and C

29. Maximum Sustainable Yield (MSY) based management works when fish populations:
A. grow exponentially and when harvesting reduces intraspecific competition
B. grow according to logistic growth, and when catch rate is less than population growth rate
C. reproduce excess offspring and, due to this, fishery populations are an unlimited resource
D. grow exponentially and when catch rate is less than fish population growth rate.

30. What is a potential consequence of following a MSY based fishery management strategy?
A. Reproductive strategy of species of interest does not follow assumptions of MSY
B. There are direct and indirect impacts on food web interactions
C. There is a time lag from the effect of harvesting and fishery becomes vulnerable to collapse
D. All of the above

Short Answer or Short Essay Questions

31.  (4 pts) What is the difference between per capita growth rate and net reproductive rate?
The per capita growth rate, r, is the number of offspring produced each year by every individual (on average). The Net Reproductive Rate is the average number of (female) offspring produced by each female over her lifetime.

32.  (3 pts) Calculate the per capita growth rate for a butterfly population with these characteristics, and assuming density-independent population growth:
You must show your work for full credit.
Population size (N) = 100
Carrying capacity = 2000
Birth rate = 0.18
Death rate = 0.06                r = b-d = 0.18-0.06 = 0.12

33. You are interested in determining the population growth rate for a population of brook trout that has different ages.  Brook trout live until they are 3 years old and start reproducing when they are 2 years old.  They have 20 offspring when they are 2 years old and 30 offspring when they are 3 years old.

Age (x)

Number dying during age interval

Number surviving at beginning of age interval





0 years







1 years







2 years







3 years








a. (3 pts) Complete the columns for “Number surviving”, lx, and bx.


b. (3 pts) Compute the net reproductive rate, R0.  sum of column lxbx = 7.0  


c. (2 pts) Calculate the mean generation time (T).  T = sum of column xlxbx/R0 = 17/7.0


d. (2 pts) Is this population growing or shrinking?  How do you know?

Growing.  When R0 > 1, each female is more than replacing herself

34. (2 pts) What causes population size to oscillate over time? (2 pts) Provide a brief and specific example of a population that has been observed to oscillate in size.
Time lags cause population sizes to oscillate when they overshoot and then undershoot carrying capacity.  I would also accept 1) species interactions (predator-prey) and 2) natural cycles in weather (for example El Nino). Many examples are possible, we discussed grouse but I am happy to be fairly open as long as they are on the right track.

35a. (3 pts) In Dr. Haddad’s study, name two different groups of species whose dispersal was increased by corridors:
1. Butterflies (insects)
2. Plants (dispersed by birds)
Pollen (pollinators)
Small mammals

35b. (3 pts) How did corridors, and the increased dispersal they cause, affect plant diversity?
Corridors increased plant diversity (or plant species richness)

36. (3 pts) What is the difference between dispersal and migration?
Dispersal refers to movement away from the place of birth.  Migration is the movement between one place and another, tracking resources.

37. (3 pts) Briefly, provide one example illustrating density-dependent growth of a plant or animal population?
There are many examples we discussed in class, related to fruit flies, deer, terns, protozoans, flax.  Let’s be lenient here, as long as the description is reasonable

38. (3 pts) Why are queen conch populations considered to exhibit inverse-density dependence?
Generally, populations show population growth rate to decrease as the population increases, likely due to competition of resources. However, queen conch populations' growth rate increases when their population increase.

39.  (4 pts) How can population bottlenecks reduce genetic diversity? Provide an example from class or your text.
A bottleneck can reduce genetic diversity when rapid decline of population size leads to random loss or fixation of alleles from populations, loss or fixation of alleles is random and not due to selection
Examples: greater prairie chicken, Florida panther, elephant seals, cheetahs (bottleneck during the Pleistocene or 10K years ago), Darin’s finches is NOT a bottleneck, it’s a founder event so it would not be a good example and therefore not full credit, MHC genes of native people in north and south America.