Chapter 15

Question 1

If you were searching for a predator ideally suited to controlling a particular insect species that
damages crops (such as cyclamen mites on strawberries), which of the following predator
attributes would you seek? (Assume that the predator does, in fact, eat the insect species in
question.)
A) high reproductive capacity compared to that of the prey
B) strong dispersal powers
C) ability to switch to alternative food resources when the primary prey are unavailable
D) all of the above

Answer 1

D) all of the above

Question 2

When the predator of the cyclamen mite was controlled through application of the insecticide
parathion to strawberry plants in the greenhouse, what happened to the population of the
cyclamen mite?
A) The population of the cyclamen mite grew rapidly to a damaging level.
B) The population of the cyclamen mite declined rapidly to a low level.
C) The population of the cyclamen mite remained unaffected.
D) The population of the cyclamen mite went locally extinct.

Answer 2

A) The population of the cyclamen mite grew rapidly to a damaging level.

Question 3

The effort to control the Klamath weed by introduced beetles in the genus Chrysolina illustrates
which of the following?
A) Herbivores can have substantial effects on the performance of plant populations.
B) Herbivores have only limited effects on the performance of plant populations.

Answer 3

A) Herbivores can have substantial effects on the performance of plant populations

Question 4

In Canada, most large herbivorous prey (snowshoe hares, muskrat, ruffed grouse, and
ptarmigan) have population cycles with periods of:
A) 9‐10 years B) 4 years C) 1 year D) Large herbivorous prey are noncyclic.

Answer 4

A) 9‐10 years

Question 5

In which of the following habitats in Canada are predator‐prey population cycles observed to
have longer periods?
A) tundra
B) forest
C) Both tundra and forest have population cycles of similar period.

Answer 5

B) forest

Question 6

In Canada, most predators have population cycles that:
A) have shorter periodicity than those of their prey species.
B) have the same periodicity as those of their prey species.
C) have longer periodicity than those of their prey species.

Answer 6

B) have the same periodicity as those of their prey species.

Question 7

In general, population models predict that the period of a population cycle will be about how
many times as long as the lag in response to a change in the environment?
A) 1‐2 B) 4‐5 C) 9‐10 D) none of the above

Answer 7

B) 4‐5

Question 8

Pathogens infect individuals more readily in crowded than in sparse populations because the
chances of contacting a new host are greater in a crowded population.
A) True B) False

Answer 8

A) True

Question 9

Nuclear polyhedrosis virus, which causes high mortality in the forest tent caterpillar, was found
to exert less influence on caterpillars in fragmented forests because:
A) caterpillars suffer more mortality from other causes.
B) caterpillars are infected by a less virulent virus that confers cross‐immunity.
C) more intense sunlight inactivates the virus.
D) lower relative humidity inactivates the virus.

Answer 9

C) more intense sunlight inactivates the virus.

Question 10

When G. F. Gause placed Paramecium, a prey species, and Didinium, a predator species,
together in plain test tubes with a nutritive medium:
A) the prey were driven to extinction by the predator, which then starved.
B) the predator went extinct after consuming some prey, leaving the remaining prey to
flourish.
C) both species coexisted with stable populations.
D) both species coexisted with populations exhibiting cyclic fluctuations.

Answer 10

A) the prey were driven to extinction by the predator, which then starved.

Question 11

When G. F. Gause placed Paramecium, a prey species, and Didinium, a predator species,
together in test tubes with a nutritive medium and a glass wool refugium for the prey:
A) the prey were driven to extinction by the predator, which then starved.
B) the predator went extinct after consuming some prey, leaving the remaining prey to
flourish.
C) both species coexisted with stable populations.
D) both species coexisted with populations exhibiting cyclic fluctuations.

Answer 11

B) the predator went extinct after consuming some prey, leaving the remaining prey to
flourish.

Question 12

G. F. Gause was able to maintain oscillating populations of Paramecium, a prey species, and
Didinium, a predator species, together in test tubes by:
A) creating a complex physical system in the test tubes.
B) adding low levels of a vitamin mix.
C) supplementing food as needed.
D) periodically adding small numbers of predators.

Answer 12

D) periodically adding small numbers of predators.

Question 13

One of the most elaborate laboratory experiments devoted to coexistence of predator and prey
was conducted by C. B. Huffaker. His experiments focused on __________.
A) snowshoe hares and lynx
B) lemmings and snowy owls
C) cyclamen mites and their predator, Typhlodromus
D) six‐spotted mites and their predator, Typhlodromus

Answer 13

D) six‐spotted mites and their predator, Typhlodromus

Question 14

What was a key finding emerging from the laboratory studies conducted by C. B. Huffaker?
A) Predator and prey cannot coexist under any conditions.
B) Predator and prey coexist under essentially all laboratory conditions.
C) Predator and prey coexist only when each is subject to parasitism.
D) Predator and prey coexist only within a spatial mosaic of suitable habitats.

Answer 14

D) Predator and prey coexist only within a spatial mosaic of suitable habitats.

Question 15

In Huffaker’s experiments with coexistence of predator and prey, a tenuous coexistence was
achieved only when the following condition was met:
A) time delay resulting from slow dispersal of predators
B) time delay resulting from slow predator response to increased prey abundance
C) presence of suitable refuges for prey
D) all of the above

Answer 15

D) all of the above

Question 16

In the Lotka‐Volterra population model for a prey population, dV/dt = rV ‐ cVP, which of the
terms on the right‐hand side of the equation incorporates dependence on predator
abundance?
A) rV B) cVP

Answer 16

B) cVP

Question 17

In the Lotka‐Volterra population model for a prey population, dV/dt = rV ‐ cVP, which of the
terms on the right‐hand side of the equation reflects exponential growth of the prey population
in the absence of predators?
A) rV B) cVP

Answer 17

A) rV

Question 18

In the Lotka‐Volterra population model for a prey population, which of the following processes
is affected by predators?
A) births B) deaths C) both births and deaths

Answer 18

B) deaths

Question 19

In the Lotka‐Volterra population model for a predator population, dP/dt = acVP ‐ dP, which of
the terms on the right‐hand side of the equation incorporates dependence on prey abundance?
A) acVP B) dP

Answer 19

A) acVP

Question 20

In the Lotka‐Volterra population model for a predator population, dP/dt = acVP ‐ dP, which of
the terms on the right‐hand side of the equation reflects the probability of predator death
regardless of the size of the prey population?
A) acVP B) dP

Answer 20

B) dP

Question 21

In the Lotka‐Volterra population model for a predator population, which of the following
processes is affected by prey?
A) births B) deaths C) both births and deaths

Answer 21

A) births

Question 22

How would you characterize the Lotka‐Volterra predator‐prey model of population dynamics?
A) discrete‐time B) continuous‐time C) a hybrid model

Answer 22

B) continuous‐time

Question 23

In the Lotka‐Volterra population model for predator and prey populations, what happens when
a system with populations at the joint equilibrium is moved away from this equilibrium?
A) Nothing happens.
B) The system returns to the joint equilibrium.
C) The system begins cyclic oscillations

Answer 23

C) The system begins cyclic oscillations

Question 24

Given the behavior addressed in the previous question, what property would you ascribe to the
Lotka‐Volterra model?
A) positive stability
B) neutral stability
C) negative stability

Answer 24

B) neutral stability

Question 25

Brendan Bohannon and Richard Lenski tested the predictions of the Lotka‐Volterra predatorprey
model in a simple microcosm experiment. What was their general conclusion?
A) The Lotka‐Volterra model fails to capture the essence of predator‐prey interactions.
B) The Lotka‐Volterra model captures the essence of predator‐prey interactions.
C) Their experimental system could not successfully test predictions of the Lotka‐Volterra
model.

Answer 25

B) The Lotka‐Volterra model captures the essence of predator‐prey interactions.

Question 26

In the Bohannon/Lenski microcosm experiment (previous question), the prey item was a
bacterium, Escherichia coli. What was the predator?
A) the hare, Lepus D) the bacteriophage, T4
B) the mite, Typhlodromus E) none of the above
C) the protozoan, Didinium

Answer 26

D) the bacteriophage, T4

Question 27

In the S‐I‐R model of disease transmission, what value of R0 will result in a disease epidemic
when a small number of infectious individuals are introduced into the population?
A) R0 = 0
B) R0 1

Answer 27

D) R0 > 1

Question 28

In the S‐I‐R model of disease transmission, what is the eventual outcome when an epidemic
spreads through a host population?
A) The host goes extinct.
B) The number of infected individuals eventually reaches a stable, nonzero value.
C) All host individuals become susceptible.
D) The epidemic runs its course.

Answer 28

D) The epidemic runs its course

Question 29

Recent experience with the chytrid fungus and global decline of amphibians is that a multi‐host
pathogen has the ability to persist and spread even after driving one of its hosts extinct.
A) True B) False

Answer 29

A) True

Question 30

The ultimate fate of predators and prey that conform to the Lotka‐Volterra model is that
random perturbations will eventually increase oscillations in population size to the point where
one or both of the populations will die out.
A) True B) False

Answer 30

A) True

Question 31

Individual Zyngis, insatiable predators, consume prey in direct proportion to their abundance or
density at rate c. What kind of functional response do Zyngis have (using the categories devised
by C. S. Holling)?
A) type I B) type II C) type III

Answer 31

A) type I

Question 32

Is the functional response of Zyngis (previous question) consistent with the basic model of
predator‐prey population dynamics developed by Lotka and Volterra?
A) Yes B) No

Answer 32

A) Yes

Question 33

Holling type II and type III functional responses differ little at high prey densities. Both exhibit:
A) a leveling‐off in consumption rates of individual predators at high prey densities.
B) a linear increase in consumption rates of individual predators at high prey densities.
C) a decline in consumption rates of individual predators at high prey densities.

Answer 33

A) a leveling‐off in consumption rates of individual predators at high prey densities.

Question 34

What separates the Holling type II and III functional responses?
A) In the type III response, the proportion of prey consumed per predator is decreased at
lower prey densities.
B) In the type III response, the proportion of prey consumed per predator is increased at lower
prey densities.
C) There is no meaningful difference between the type II and type III responses.

Answer 34

A) In the type III response, the proportion of prey consumed per predator is decreased at
lower prey densities.

Question 35

A Holling type III functional response might be the result of which of the following?
A) heterogeneous habitat
B) lack of reinforcement of learned searching behavior
C) ability of the predator to switch to alternative prey
D) all of the above

Answer 35

D) all of the above

Question 36

Many species of predator exhibit relatively slow population growth, yet in some cases their
numerical response to increased prey density can be relatively rapid. What process could
contribute to this rapid numerical response?
A) immigration of individuals from surrounding areas
B) temporary upward adjustment of rm of the predator
C) enhanced learning on the part of juveniles
D) increased “carelessness” on the part of the prey

Answer 36

A) immigration of individuals

Question 37

When predators and their prey exhibit cyclic population oscillations, the typical pattern is for:
A) numerical response of the predator to lag behind that of the prey.
B) numerical response of the predator to precede that of the prey.
C) numerical responses of both the predator and the prey to be nearly identical.

Answer 37

A) numerical response of the predator to lag behind that of the prey.

Question 38

Only one of the following factors tends to destabilize a predator‐prey relationship, leading to
greater amplitude of cyclic population fluctuations. Which is it?
A) density‐dependent limitation of either predator or prey by factors external to their
relationship
B) alternative food sources for the predator
C) safe refuges from predation at low prey densities
D) time delays in the responses of populations to changes in their food supplies

Answer 38

D) time delays in the responses of populations to changes in their food supplies

Question 39

Which of the following factors can balance destabilizing forces and constrain the amplitude of
predator‐prey cycles?
A) predator inefficiency
B) density‐dependent limitation of predator or prey by external factors
C) alternative food sources for the predator
D) safe refuges from predation at low prey densities
E) reduced time delays in predator responses to prey abundance
F) all of the above

Answer 39

F) all of the above

Question 40

The lesson for biological control of pest populations from modeling efforts is as follows: When a
prey species escapes from control by its predator, it can be readily brought back to a low
equilibrium density by renewed attention from its predator.
A) True B) False

Answer 40

B) False

Question 41

Among the best‐known examples of cyclic oscillations of predators and prey is one based on
records of the Hudson’s Bay Company, in which the numbers of pelts of __________ purchased
each year from trappers were tallied.

Answer 41

lynx and snowshoe hare

Question 42

Use of predators or parasitoids to control outbreaks of herbivorous agricultural pests is referred
to as __________ control.

Answer 42

biological

Question 43

__________ conducted one of the earliest laboratory experiments on predator‐prey systems,
growing ciliated protozoa in nutritive media contained in test tubes.

Answer 43

G. F. Gause

Question 44

In the Lotka‐Volterra predator‐prey model, no internal forces exist to return the system to its
joint equilibrium once perturbed. Instead, cyclic oscillations result, a situation referred to as a
__________ equilibrium.

Answer 44

neutral

Question 45

In the Lotka‐Volterra predator‐prey model, changes in predator and prey populations follow a
closed cycle called a __________.

Answer 45

population trajectory

Question 46

The S‐I‐R model simulates the interactions of __________ and their hosts.

Answer 46

pathogens

Question 47

C. S. Holling proposed a family of __________ that describe the relationship of prey consumed
by individual predators to prey density.

Answer 47

functional responses

Question 48

Continued predator response to high levels of prey requires that the number of predators
increases through immigration or recruitment of young in what is known as the __________.

Answer 48

numerical response

Question 49

Safe __________ from predation allow prey populations to maintain themselves at higher
levels in the face of intense predation, facilitating the recovery phase of the population cycle.
This is one factor that can stabilize predator‐prey systems.

Answer 49

refuges

Question 50

Use of an alternative food source by a predator is referred to as __________.

Answer 50

switching