AEC360 Exam 3 Key
(Questions are identical in Code 16, but in a different order)

Multiple Choice Questions (2 pts each)

1. Which species had the largest population size before going extinct?
A. Giant Moa
B. Passenger Pigeon
C. Monarch
D. Carolina Parakeet
E. Dodo

2. In models of disease dynamics, all individuals begin as:
A. Recovered
B. Susceptible
C. Infected
D. All of the above
E. None of the above

3. What value of R0 (the basic reproductive ratio) will result in a disease epidemic after a small number of infectious individuals are introduced into the population?
A. R0 = 0
B. R0 > 1
C. R0 = 1
D. R0 < 1

4. The rate of evolution of HIV is controlled by:
A. its slow rate of mutation
B. its genetic structure, which is stable over time
C. the selective force imposed by drugs
D. its slow population growth rate
E. None of the above

5. The moth Cactoblastis cactorum was introduced to Australia to control which of the following pests?
A. Prickly pear
B. Klamath weed
C. A tropical legume
D. Pests of cotton plants

6. Based on the results of Problem Set 3, which should act to increase the time to extinction for killer whales?
A.  Higher population size
B.  Lower standard deviation of population growth rate
C.  Both of the above
D.  None of the above

7. Gause, and then Luckinbill conducted experiments on the dynamics of predator and prey populations with which organisms?
A. plants
B. lynx and hare
C. insects
D. flour beetles
E. protozoans

8. Predators do not drive their prey to extinction because:
A. it takes time for predators to respond to prey abundances
B. prey population growth is very rapid as they have abundant resources
C. the predator and prey are confined to small spaces
D. None of the above

9. The mathematical models for predators and prey begin from which of the following models that we learned previously?
A. energy balance equation
B. exponential population growth equation
C. logistic population growth equation
D. life table equation

10.  In the Lotka-Volterra predator-prey model, which term refers to the capture efficiency of prey by predators?
A. a
B. b
C. c
D. d
E. r

11. In a similar area, some species live where there is high stress (for example, Poli’s Stellate Barnacle) whereas others are better competitors (Rock Barnacle). This is an example of:
A. intraspecific competition
B. exploitation competition
C. asymmetric competition
D. apparent competition
E. none of the above

12. When diatoms in the genera Cyclotella and Asterionella at Si/P ratios between 6 and 90, the two species coexisted. Why?
A. Both species were phosphorus-limited.
B. Both species were silicon-limited.
C. One species was limited by phosphorus, and the other was limited by silicon.
D. Neither species was limited by phosphorus or silicon.
E. The cultures were continuously supplemented with individuals of the two species.

13. Apparent competition refers to the case when:
A. interference competition is direct and easily observed
B. the effects of exploitative competition strongly limit population sizes
C. predators are present and cause one prey species (which may not be the best competitor) to be dominant
D. intraspecific competition is stronger than interspecific competition

14. The mathematical models for competition between species begin from which of the following models that we learned previously?
A. energy balance equation
B. exponential population growth equation
C. logistic population growth equation
D. life table equation

15. In the competition equations developed by Lotka and others, what does the term βN1 represent?
A. instantaneous rate of population increase of species 1
B. carrying capacity of the environment for species 1
C. reduction of species 1's carrying capacity by individuals of species 1
D. reduction of species 2's carrying capacity by individuals of species 1

16. In two-species competition, what is true when stable coexistence is achieved under the Lotka-Volterra competition model?
A. Species 1 limits Species 2 more than it limits itself
B. Species 2 limits Species 1 more than it limits itself
C. Species 1 and Species 2 both limit each other more than they limit themselves
D. Species 1 and Species 2 both limit themselves more than they limit each other
E. None of the above

17. Three new islands have emerged from the sea as a result of volcanic eruptions: one Hawaiian, one Canary, and another off the coast of Yemen. As newly emerged islands, all are identical to each other. Which of the following observations of island colonization would support Gleason’s individualistic concept of communities?
A. Each island is initially colonized by the wolf spider, Pardosa.
B. Each island is initially colonized by a different spider, Pardosa, Phidippus, and Rejunellus.
C. The short-lived plant species, Schedonnardus, facilitates the growth of the perennial, Guitierriza.
D. None of the above
E. B and C

18. Ecologists can study community composition by measuring:
A. abundance
B. species richness
C. constancy
D. All of the above
E. A and B only

19. In 1926, gray wolves became locally extinct in Yellowstone National Park as a result of unregulated hunting. In the following years, researchers observed significantly high mortality in aspen and cottonwood trees caused by overgrazing elk. This is an example of:
A. predator switching
B. bottom-up control
C. a trophic cascade
D. None of the above
E. B and C

20. A keystone species refers to a species that:
A. easily out-competes other species
B. is important to community structure given its low biomass
C. has a high abundance relative to other species in the community
D. has a high interaction rate with other species

21. A category of mutualism is:
A. dispersive
B. defensive
C. trophic
D. all of the above
E. none of the above

22. When yucca moths lay more than seven eggs in a yucca flower, the moths:
A. increase number of caterpillars that then become adults
B. increase their population growth rate
C. cause more yucca flowers to be aborted
D. after laying eggs, decrease their pollination of flowers

23. Acacia plants
A. provide a place for ants to live within their thorns
B. provide food (nectar and proteins) for ants
C. are defended by ants from herbivores
D. all of the above
E. none of the above

24. To determine whether two individuals are of the same or different species, scientists use __________data.
A. genetic
B. morphological
C. behavioral (mating)
D. reproductive success (viable offspring)
E. all of the above

25. “The geographical separation of a population, typically by a physical barrier such as a mountain range or river, resulting in a pair of closely related species” defines:
A. founder effect
B. vicariance event
C. sympatry
D. convergent evolution
E. parsimony

26.  Which other species besides Homo sapiens have been found outside Africa?
A. Homo erectus
B. Homo neanderthalensis
C. Homo floresiensis
D.  All of the above

27. Evolution of hominins in the past four million years accelerated due to:
A. wetter environments
B. increased cover of trees and shrubs
C. increased abundance of bovids (cloven-hoved, ruminant mammals)
D. All of the above
E. None of the above

28.  The emergence of complex language is thought to have arisen in Homo sapiens approximately how many years ago?
A. 5,000
B. 50,000
C. 500,000
D. 5 million
E. 50 million

29. Homo sapiens are
A. direct descendants of Homo neanderthalensis
B. evolved completely separately from Homo neanderthalensis
C. equal parts Homo sapiens and Homo neanderthanensis
D. evolved separately from Homo neanderthalensis, but with some small amount of interbreeding

30. Diverse communities of potential competitors can exist together in small areas (for example, 100 plant species in 100m2 in the Green Swamp, NC). This may be possible because:
A. herbivores may reduce the abundance of good competitors
B. the concentration of limiting resources across the area is constant
C. the concentration of limiting resources over time is constant
D. the worst competitors may arrive at good sites last

Short Answer or Short Essay Questions

31. (3 pts) List three causes of extinction.  Each is a general category that can be stated in 1-2 words

1. Habitat Loss

2. Overhunting

3.Climate Change

 - Invasive Species
- Natural causes

32. Fill in the following table to indicate whether each species interaction results in a positive, negative, or neutral effect on the population growth rate of the two species involved. Use a “+” for a positive effect, a “-“ for a negative effect, and a “0” for no effect. If one line involves two different responses, you can write them in any order (7 points)

Predation +/-
Commensalism +/0
Herbivory +/-
Parasitism +/-
Mutualism +/+
Interspecific competition -/-
Disease +/-

33a.  (3 pts)  What are on the three corners of the “disease triangle”?
host, pathogen, environment

33b.  (3 pts)  Define “infectious disease”
Infectious disease is a condition that is harmful to the host, caused by a parasite or pathogen

34.  (5 pts) How does evolution of one species induced by the interactions with another species differ from evolution in response to physical environmental factors?

Biological factors stimulate mutual evolutionary responses in traits of interacting populations. Physical factors do not.  Biological factors promote a diversity of adaptations.

35.  Consider the graphic below, representing the competition between two species of oaks, red oaks and white oaks:

35a.  What does the α next to the y-axis refer to? (2 pts)
This converts the effect of white oaks on population of red oaks into terms of red oaks

35b.  What does the dashed line represent? (2 pts)
dN1/dt = 0

35c.  If the population sizes of the oaks start at values represented by the ‘X’, what will happen to the population sizes of each oak species over time? (2 pts)
They both increase

35d.  If the population sizes of the oaks start at values represented by the dot (where the lines cross), what will happen to the sizes of their populations over time? (2 pts)
They are at equilibrium (no change)

36. (6 pts) Give three different reasons that could explain why the number of species is higher in the tropics. Explain in no more than one sentence each.

1.Time -- tropical climates have existed on earth for longer periods, and current locations that are tropical have remained stable over millions of years.  Also, the rate of evolution may be faster in the tropics


2. Productivity -- higher in tropics because of higher temperatures plus precitation


3. Increased variability of resources

-tropical species may have smaller environmental tolerances

-area -- there is a greater area of tropics than of other biomes

-mid-domain hypothesis

37a. Define biocontrol (2 pts)

 Use of natural enemies to control pest population sizes


37b. List three key parts of a typical sequence of events leading from beginning to end in successful biological control (3 pts)

1. Pest species introduced and experiences exponential population growth

2. Biocontrol species introduced
3. Coexistence of biocontrol and pest species