BIO360 Exam 2 Key
(Questions are identical in Code 16, but in a different order)

Multiple Choice Questions (2 pts each)

1. Which social behavior is unknown in natural populations?
A. Cooperation
B. Selfishness
C. Altruism
D. Spitefulness
E. None of the above

2. There are benefits and costs to living in groups. In larger groups, European goldfinches spent less time husking seeds. This represents a:
A. Cost
B. Benefit
C. Both Cost and Benefit
D. Neither Cost nor Benefit

3. In South Pacific reefs, the number of parasites of five fish species living at lower densities because of higher fishing was:
A. Lower
B. the Same
C. Higher
D. None of the Above

4. In Eusocial Insects such as bees, the coefficient of relationship is highest between:
A. Brothers
B. Mother-son
C. Mother-daughter
D. Sisters

5. 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

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

7. 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

8. How are population sizes estimated?
A. Census
B. Projecting local densities to larger areas
C. Mark-recapture studies
D. All of the above

9. 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

10. Which of the following equations is used to project population size through time, under conditions of exponential growth?
A.  N(t) = N(0)ert      
B.  N(t) = N(0)(lambda)*t
C.  dN/dt = rN
D.  lambda = er
E.  r = b - d

11. If you measure the size of a chickadee population in three consecutive years, and its population size in year 1 is 122, in year 2 is 122, and year 3 is 122, what is its geometric rate of increase?
A. 0
B. 0.15
C. 1.0
D. 1.50
E. 150

12. 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 that have expanded beyond their native range
B. that are very small and are released from the limits that have reduced their population size
C. of humans following 1700, due to large changes in technologies and behaviors
D. All of the above

13. 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

14. An oak tree’s demography would be represented by which class of Survivorship Curve?
A. Type I
B. Type II
C. Type III
D. Type IIII
E. All of the above

15. 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

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

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

18. 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

19. When a population grows according to the logistic model, what is the value of r when the population is stable?
A.  r = r0
B.  r = 0
C.  r = K
D.  r = N

20. Which of the lines in the graph to the right is characteristic of exponential (that is, density-independent) population growth?
The flat line with no slope (r does not change with population density)

21. When a population grows according to a logistic model, what happens if the population exceeds carrying capacity?
A.  The population resumes exponential growth.
B.  The size of the population begins to decline.
C.  The size of the population remains constant.
D.  The population goes extinct.

22. Why do lemmings commit mass suicide by jumping into the ocean?
A.  Their population densities become too high
B.  It is a response to disease epidemics
C.  This represents a mistaken attempt at dispersal
D.  They don’t do this

23. Which of the following fisheries for whales had collapsed by the time of the 1986 whaling moratorium?
A. Blue whales
B. Fin whales
C. Sperm whales
D. Sei whales
E. All of the above

24. In the past four decades, the proportion of fisheries that has collapsed in different regions of the world has
A. Decreased
B. Remained stable
C. Increased
D. Increased and Decreased

25. In the past three decades, the average trophic position (highest = top predators, lowest = primary producers) has:
A. decreased
B. remained constant
C. increased

26. The time to extinction will be longer if:
A. The starting population size is smaller
B. The starting population size is larger
C. Variation in the population size over time is larger
D. Variation in the population size over time is smaller
E. B & D

27. 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 the same at any year.
A. first
B. third
C. fifth
D. eighth
E. cannot be determined

28. 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. when they are separated, cluster different areas of habitat closer together
D. connect habitats with corridors

29. 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

30. 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

Short Answer or Short Essay Questions

31.  (2 pts) What is Indirect Fitness?  (2 pts) What social behavior does it help to explain?
When an individual helps a relative improve its fitness, that individual is indirectly passing on more copies of its own genes.  Indirect fitness helps to explain altruism among close relatives.

32.  (3 pts) Calculate 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 butterflies
Carrying capacity = 200 butterflies
Birth rate = 0.10 individuals/individual/year
Death rate = 0.14 individuals/individual/year

r = b-d = 0.10 - 0.14 = -0.04 individuals/individual/year

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


Number dying during age interval

Number surviving at beginning of age interval





0 years







1 years







2 years







3 years








a. (4 pts) Complete the columns for “Number surviving”, lx, and bx.

b. (3 pts) Compute R0.
Sum of lxbx = 7 (see above)

c. (3 pts) Calculate the mean generation time (T).  Leave your answer as a fraction.
Sum of xlxbx / sum of lxbx = 17/7 (see above)

d. (4 pts) Is this population growing or shrinking?  How do you know?
Growing.  The population is growing when R0 > 1, this is, when the average female more than replaces herself.

34. (2 pts) What causes population size to oscillate over time? (2 pts) Provide a brief, general explanation and a specific example.
Time delays (or time lags) in the ability of a population to respond to change in its environment.  Many examples, including red grouse and roundworms, lynx and hare, and others were possible.

35a. (3 pts) In Dr. Haddad’s study, name three different groups of species whose dispersal was increased by corridors:

1. Butterflies (insects)

2. Plants (dispersed by birds)

3. Pollen (or 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. (4 pts) What is the meaning of Maximum Sustainable Yield in fisheries?  And, as a first approximation, what population size gives this yield?
Maximum Sustainable Yield is the maximum number of fish that can be harvested in perpetuity.  As a first approximation, MSY is highest at 1/2 carrying capacity (K).

38. (2 pts) Briefly, provide one example illustrating density-dependent growth of a plant or animal population?
Many examples possible, one is needed:
-Fruitfly survivorship and fecundity decline with density
-Terns disperse to new islands as they reach K
-Deer increase fecundity at higher density
-flax plants decrease size at higher density