Ecology - Exam 2 Practice Exam

Front 1

1. Which of the following can be said of the Lotka-Volterra competition model?


A) The point where the two isoclines cross is where there is no competitive interaction occurring.

B) There are no conditions in the model that allow for two competing species to coexist.

C) At the point where the two isoclines cross, dN1/dt = dN2/dt = 0.

D) The model assumes each population is growing geometrically.

E) The model predicts coexistence when K1 = K2.

Back 1

C) At the point where the two isoclines cross, dN1/dt = dN2/dt = 0.

Front 2

The lynx-snowshoe hare interaction was discussed in lecture. This interaction illustrates_______.


A) the numerical response of a predator

B) the predator satiation hypothesis

C) how removing a predator from areas can greatly increase the density of a prey species

D) periodic oscillations in the densities of a predator and it’s prey

E) both A) and D)

Back 2

E) both A) and D)

Front 3

3. Psuedomyrmex ants live exclusively in the swollen thorns of acacia trees in Central America. In return
for food and shelter provided by the trees, the ants aggressively defend the tree from leaf-eating
insects. This interaction between ants and acacias represents an example of ____________.


A) facultative mutualism

B) obligate mutualism

C) carnivory

D) dispersive mutualism

E) herbivory

Back 3

B) obligate mutualism

* Spoke about in lecture how when ants were removed from acacia, the acacia were out-competed by local plants, and taken over by herbivorous insects.

* Also called Defensive Mutualism

Front 4

4. The concept that random variation in population birth and death rates can lead to the extinction of small
populations is called “________________,”


A) environmental stochasticity

B) the declining population paradigm

C) the under-compensation hypothesis

D) the functional response

E) demographic stochasticity

Back 4

E) demographic stochasticity

Front 5

5. Which of the following best describes α and β in the Lotka-Volterra model?


A) they represent the carrying capacities of competing populations

B) they represent the equilibrium densities of competing populations

C) they represent the intrinsic rate of population growth for populations that are competing

D) they measure the competitive effect that each population has on the other

E) they represent the minimum viable population size for competing populations

Back 5

D) they measure the competitive effect that each population has on the other

pg. 166 (Krebs)

Front 6

6. Aphytis metinus is a species of wasp that lays its eggs on red-scale insects. When the eggs hatch, the
wasp larvae then use the scale insects as food. This type of interaction is most appropriately called:


A) Cannibalism

B) Coexistence

C) Parasitoidism

D) Parasitism

E) Mutualism

Back 6

C) Parasitoidism

Front 7

7. If a fruit pigeon eats the fruits of a tropical tree and the seeds pass through its digestive tract and are
still viable (can germinate and grow), this is an example of


A) Frugivory

B) Dispersive mutualism

C) Trophic mutualism

D) All of the above

E) A and B

Back 7

E) A and B

Front 8

8. ______________________ is the single most important cause of deterministic extinction.


A) Overkill

B) Global warming

C) Water pollution

D) Habitat destruction

E) Introduction of exotic species

Back 8

D) Habitat destruction

Front 9

10. There are limits to the ability of predators to respond to increasing prey density. It has been suggested
that prey may be able to reduce their individual probability of being eaten through a strategy called
“__________________.”


A) over-compensation

B) predator satiation

C) defensive mutualism

D) character displacement

E) population cycles

Back 9

B) predator satiation

Front 10

11. It is currently believed that secondary plant substances have primarily evolved _________________.


A) to facilitate mutualistic interactions between plants and their pollinators

B) to provide chemical protection against herbivores

C) as a means of excreting metabolic waste products

D) as “weapons” that plants can use to poison competitors

E) there is no consensus about why these compounds have evolved

Back 10

B) to provide chemical protection against herbivores

* pg 212 (Krebs)

Front 11

13. Character displacement …


A) intensifies competition.

B) is a change in morphology as a result of competition.

C) only occurs within a species.

D) generally occurs over ecological time.

E) All of the above

Back 11

B) is a change in morphology as a result of competition.

pg. 182

Front 12

14. In years where it rains a lot in the Serengeti a lot of grass grows and more zebras are born. Lions
respond by eating more zebras. This is an example of:


A) herbivore populations self-regulating

B) predators reducing herbivore numbers

C) the overcompensation hypothesis

D) plant defenses against herbivores

E) mutualism

Back 12

B) predators reducing herbivore numbers

Front 13

15. Existing data from field studies support the notion there are optimal levels of grazing that can actually
increase both plant productivity and individual fitness. TRUE or FALSE?


A) True

B) False

Back 13

B) False

Front 14

16. The great auk, the North American bison, and the white rhinoceros have what in common?


A) They are all extinct species.

B) They are species whose numbers have been greatly reduced through habitat destruction.

C) They are species that have been shown to display intrinsic regulation of their density.

D) They are species that have experienced population overkill.

E) They are species whose distributions are being affected by global warming.

Back 14

D) They are species that have experienced population overkill.

Front 15

18. In his laboratory studies on predator-prey interactions, Gause was able produce oscillations in predator
(Didinium) and prey (Paramecium) densities by_________________________.


A) periodically adding more predators and prey to the system (“immigration”)

B) providing oat sediment as a refuge for the prey

C) simply putting them together in mixed culture

D) turning off the laboratory lights

E) None of the above

Back 15

A) periodically adding more predators and prey to the system (“immigration”)

Front 16

20. Which of the following are causes of deterministic extinctions?


A) habitat loss and fragmentation

B) genetic stochasticity

C) environmental variation in survival rates

D) A and C

E) All of the above

Back 16

A) habitat loss and fragmentation

Front 17

21. Conservation ecology is based on 2 major paradigms. Name them.

Back 17

1) Small Population Paradigm

2) Declining Population Paradigm

Front 18

22. List 3 main causes of deterministic species extinction.

Back 18

1) Overkill

2) Habitat destruction and fragmentation

3) Introductions of exotics

Front 19

23 A) The hypothesis that grazing by each species of Serengeti herbivore improves the food supply
available for the next herbivore species.

Back 19

Grazing facilitation

Front 20

23 B) Provide an example of a “trophic mutualism.”

Back 20

EXA 1: Lichen (alga + fungus)

EXA 2: Mycorrhizae (plant roots + fungus)

Front 21

23 C) Mechanism by which 7 species of Anolis lizards are able to coexist in the same tropical forest
habitat in the Dominican Republic.

Back 21

Resource Partitioning

Front 22

23 D) The competitive exclusion principle was first demonstrated using laboratory populations of 2
species of Paramecium by what biologist?

Back 22

Gause

Front 23

23 E) The population size that will ensure that a population will persist for a specific length of time at
some acceptable level of risk.

Back 23

Minimum viable population

Front 24

23 F) Predators may respond to increasing prey densities by increasing their own densities via
immigration. What is this response called?

Back 24

The "Dinner Bell" response.

a.k.a. "Aggregative Response"

Front 25

23 G) Seed-producing trees periodically produce large numbers of seeds synchronously over large
geographic areas in an effort to satiate seed predators and decrease seed mortality. What is this
phenomenon called?

Back 25

Masting

Front 26

H) Interspecific competition frequently involves closely related species. However, competition can
also occur between such distantly related taxa as mammals and insects. TRUE or FALSE?

Back 26

True

Front 27

23 I) Plants frequently use animals as vectors for transporting pollen or seeds. In return, the plants
provide the vector with nectar or some other form of food. What is the specific name for this
type of mutualistic interaction?

Back 27

Dispersive Mutualism

Front 28

24. Populations of Species 1 and Species 2 are put together in a common habitat. Species 1 is the
superior competitor and always drives Species 2 to extinction. Draw the Lotka-Volterra isocline
graph for this system. Make sure 1) that the x and y axes of your graph are labeled and 2) that the
values of the 4 isocline intercepts are given.

Back 28

Yes

Front 29

** Practice Exam 1 (2008)

7. Which of the following is true with respect to geometric growth?

I. Populations in the real world never display geometric growth.
II. The geometric growth model can be used for populations with continuous reproduction.
III. No population can grow geometrically forever
IV. The geometric model incorporates the notion of "carrying capacity"
V. The geometric growth model can be used for populations with periodic reproduction

ANSWERS:
a. I only
b. II and III only
c. III only
d. II, III and V only
e. IV and V only

Back 29

d. II, III and V only

Front 30

** Practice Exam 1 (2008)

20. In the logistic population growth equation, the expression (K-N)/K is called the “_________.”


a. potential for geometric growth

b. rate of population increase

c. unutilized opportunity for population growth

d. intrinsic capacity for increase

e. carrying capacity

Back 30

c. unutilized opportunity for population growth

Front 31

** Practice Exam 1 (2008)

22. A group of 10 mice (5 males and 5 females) colonizes a large granary full of wheat and begins reproducing at a
rate of r = 0.5 mice/capita/per week. Given that there are virtually unlimited resources for the mice, assume
their population grows exponentially. How many mice will the granary contain after 6 weeks? (3,000 pts.)

Back 31

~201 mice

N_t = N_o*e^(rt)

N_t = 10*e^(.5*6)
N_t = 201

Front 32

** Practice Exam 1

3. Population A has a per capita rate of increase of r = -0.05. Population B has a per capita rate of increase of r = -0.13. Which of the following statements is true?


a. Population A is increasing faster than Population B.

b. Population B is increasing faster than Population A.

c. Both populations are declining.

d. Population A is growing exponentially, while Population B is exhibiting logistic growth.

e. Both c. and d. are true.

Back 32

c. Both populations are declining.

Front 33

** Practice Exam 1

4. In the logistic growth model, dN/dt is ______________.


a. called the “intrinsic logistic growth rate”

b. at its maximum at K/2

c. at its maximum at K

d. a constant that doesn’t change with population size

e. at its maximum at low densities when populations are growing geometrically

Back 33

b. at its maximum at K/2

Front 34

** Practice Exam I

9. Which part of the logistic growth equation, dN/dt = rN(K-N)/K, represents geometric growth?


a. (K-N)/K

b. rN

c. rN(K - N)

d. rN(K – N)/K

e. K

Back 34

b. rN

Front 35

** Practice Exam I

23. A human population has a net reproductive rate of 1.3 individuals/year and a mean generation time of 25 years. Assume geometric growth. Show your work for full credit and make sure all parameters have units.

A. What is the instantaneous rate of increase for the population? (2,000 pts.)

B. What is the finite rate of population increase? (2,000 pts.)

C. Assuming a population size in the year 2000 of 100 individuals, what would the predicted size of this
population be for the year 2010? (3,000 pts.)

Back 35

A)
0.010 individuals/capita/year

r = (ln Ro)/G
r = (ln 1.3)/25
r = 0.262/25 = 0.010 individuals/capita/year


B)
1.011 individuals/capita/year
λ= e^r
λ= e^0.010
λ= 1.011 individuals/capita/year


C)
110.5 individuals
N_t = N_o*e^(rt)
N_t = 100e^(0.010)(10)
N_t = 100e^(0.1)
N_t = (100)(1.105) = 110.5 individuals

Front 36

12. In the extinction vortex model, small populations will lose genetic variability due to _____


A) inbreeding

B) natural selection

C) genetic drift

D) answers A) and B)

E) answers A) and C)

Back 36

E) answers A) and C)

Front 37

17. Which of the following best describes α and β in the Lotka-Volterra model?


A) they represent the carrying capacities of competing populations

B) they represent the equilibrium densities of competing populations

C) they represent the intrinsic rate of population growth for populations that are competing

D) they measure the competitive effect that each population has on the other

E) they represent the minimum viable population size for competing populations

Back 37

D) they measure the competitive effect that each population has on the other