Ecology Exam 3

The story of the prickly pear cactus in Australia provides evidence that

herbivores can control the populations of other species

A parasitoid is a type of

predator

Which scenario is an example of an invasive species?

zebra mussels released into the waters of the Great Lakes and spreading throughout much of the US leading to the decline of other native shellfish

Why might an herbivore that consumes many different species of plant be less successful at regulating the abundance of a well-defended plant species that an herbivore that specializes in eating a single species of plant?

a flexible herbivore will avoid the well0defended species in preference for easier food

A mesopredator is

a predator that is relatively small and consumes herbivores

When spruce budworm populations explosde in northern spruce forests, often the density of bay-breasted warblers increase in response, from the densities of breeding pairs per square km to upwards of 300 breeding pairs per square km.

a numerical response

A search image refers to

a learned mental image that assists the predator in locating and capturing a prey item

Which functional response curve shows the slowest increase in the rate of predator consumption when prey are at low densities?

type III functional response

When the number of prey consumed by the predator increases in a linear fashion as prey density increases until the predator is satiated, this is called a

type 1 functional response

When one looks at the relationship between the density of meadow voles in a field and their rate of consumption by red-tailed hawks (which feed on meadow voles) one is looking at the red-tailed hawk’s

functional response

In the Lotka-Volterra population model, the Joint Equilibrium Point is the point where

neither prey nor predator populations oscillate

In the Lotka-Volterra population model, the Equilibrium Isocline is

the population size of the prey or predator that causes the population of the predator or prey, respectively, to be stable (i.e. growth = 0)

In the Lotka-Volterra population modeling formulas, when dN/dt=0 or dP/dt=0, what has happened?

Either the prey’s (N) ot the predator’s (P) population is not growing

In the Lotka‐Volterra population modeling formulas how does the term "rN" in the prey equation compare to the term "acNP" in the predator equation?

Both terms are an attempt to quantify births

The variable “c” in both the Lotka-Volterra prey and predator equations is an attempt to quantify

the predator’s ability to capture prey

The Lotka‐Volterra population modeling formulas for change in predator and prey population size over time requires that one know the

initial population sizes of both the predator and prey

Data for lynx and snowshoe hare populations in Canada have shown that the two species have an approximately 10-year cycle in population size.

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The data collected from the mid 1800s to the mid 1900s was obtained by

looking at trapping records

Studies of predation in the boreal and tundra regions of Canada suggest that, if a predator has a population cycle of a certain length, the prey that it consumes likely has a population cycle length that is

the same length

How might a type 2 functional response prevent a predator from controlling a large prey population?

the handling time will decrease the number of prey the predator can catch

A predator’s numerical response depends on

the migration of predators

A type III functional response in predators is a result of which factors?

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1. prey refuges
2. search images
3. prey switching

1,2, and 3

According to the Lotka‐Volterra model of predator‐prey interactions, what follows a period of low prey population and low predator population?

increased predators and increased prey

According to the Lotka‐Volterra model of change in the prey and predator population sizes, what is NOT a determinant of predator growth?

growth rate of prey

Which factors determine the equilibrium population size of predators during predator–prey population cycles?

the mortality rate of the predator and the prey capture rate

In the classic experiments of C. F. Huffaker using mites and oranges, what mechanisms allowed the predator and prey populations to persist?

increased dispersal of prey

From the perspective of natural selection, alarm calls as a behavioral defense should be selected for if the recipients of the warning call

are related to the maker (initiator) of the call

Which is an example of coevolution?

when a predator and prey species both evolve crypsis

Which answer best defines what the Lotka-Volterra predator-prey model mathematically describes?

the simultaneous effect of a predator population on a prey population and a prey population on a predator population over time

Which of the following scenarios would likely cause a predator population to decline?

a declining prey population and a very large predator population

What does an equilibrium isocline describe in the Lotka-Volterra predator-prey model?

the population size of one species that causes the population of another species to be stable

Studies dealing with white-nose syndrome in bats in New York State, and elsewhere in the northeastern United States, seem to indicate that the disease is caused by a _____ that may be native to _____.

fungus: Europe

White-nose syndrome in bats in North America is known as an emerging ingectious disease for what reason?

the disease was first identified in North America in the 1970s

Wheat crops, corn crops, the American chestnut tree, the American elm, among others, have all been impacted negatively by which type of parasite?

fungal

Which type of organism is more likely to be removed from one species by another species?

ectoparasite

An advantage that endoparasites have when compared to ectoparasites is that endoparasites have

a low exposure to the varying external environmental conditions

Which organism is NOT an endoparasite?

lice

Parasite load refers to

the number of parasites of a given species that a host can harbor

The ability of the host to minimize the harm when a parasitic infection has occurred is called

infection tolerance

H5N1 is an example of

an emerging infectious disease

What practice increased the spread of mad cow disease?

adding dead cows to cow feed

What allowed H1N1 to jump to a new species of host?

direct transmission between members of the new host species

Parasites outside their native range are often

more deadly

Which is an advantage of an ectoparasite?

limited exposure to the host‘s immune system

When the H5N1 virus (bird flu) strikes an area, often one of the immediate responses of public health officials is to kill domestic flocks of birds, in an attempt to halt the transmission of the virus by way of

horizontal transmission

Vertical transmission of parasites is a transmission

between a parent and its offspring

The S-I-R model does not necessarily follow the traditional Lotka‐Volterra Model for predator and prey because

some pathogens do not attack a single host species

In the S-I-R model for infectious disease transmission, when Ro>1, what is likely to occur?

The disease will continue to spread through the population

What is true about the S-I-R model for infectious disease transmission?

all individuals begin as sesceptible to the pathogen under study

To determine whether an infection will spread through a population using the S-I-R Model, we need to know everything EXCEPT

the reproductive rate of the population

The Lotka‐Volterra (L‐V) population models used for predator and prey population size may be used for modeling parasite and host population sizes, provided that there is an understanding that

parasites may not remove their host from the population like predators do to their prey

Canadian researchers working with forest tent caterpillars have shown that

when caterpillars populations are high, endovirus populations are high as well

According to the S-I-R model, what happens when new susceptible individuals are born on regular intervals?

the state of infected individuals is cyclical and steady

According to the basic S-I-R model, the

number of infected individuals decreases over time

How does coevolution affect the relationship between hosts and parasites?

parasites become less deadly over time

When using a t-test, what is an important assumption regarding the distribution of the data?

the data has a normal distribution

Under which circumstance will a disease not spread beyond a few individuals in a population?

If the rate of infection is lower than the rate of recovery, the reproductive ratio of the infection will be less than 1

How does the rate of infection differ from the rate of contact?

The rate of contact is the probability of a susceptible individual coming into contact with an infected individual, and the rate of infection is the number of susceptible individuals that the primary case infects within a given amount of time.

In a typical S-I-R model, why does the number of susceptible people decrease over time?

because the number of infected people increases

Why are American elm trees less likely to die of Dutch elm disease now than when the disease was first brought to North America from Asia?

The most susceptible trees died in the initial outbreak and the more resistant survivors have passed their genes for resistance to their offspring.

What is the most effective way to prevent the spread of mad cow disease?

avoid feeding other cows the ground-up bodies of infected cows

Identify scenarios that describes an emerging infectious disease

* Malaria cases have increased exponentially due to malaria’s resistance to drugs and mosquitoes’ resistance to pesticides
* An infectious fungus observed in the black poplar tree recently appeared in the Eastern cottonwood tree
* Reported cases of Lyme disease in humans have increased steadily since its relatively recent recognition in 1976

Classify each statement as describing an endoparasite or an ectoparasite

Endoparasite

* protected from most competitors and predators
* easily acquires host’s nutrients for feeding
* includes viruses and other intracellular parasites

Ectoparasite

* inaccessible to its host’s immune system
* easily moves to and from its host
* vulnerable to variable external environments

Would it be effective to control a parasite by vaccinating individuals in a reservoir species infected by the parasite?

No, because the immune systems of the infected individuals are already resistant to the parasite

Classify each statement as applying to horizontal or vertical transmission of a parasite

Horizontal transmission

* transmission occurs between organisms of different species
* a vector, such as a mosquito, transmits the parasite

Vertical transmission

* transmission occurs from a parent to its offspring
* death of the host does not occur until the host has reproduced

According to the S-I-R model of parasite and host dynamics, how does the number of infections change over time if new susceptible individuals are born into the population at regular intervals?

the number of infected individuals fluctuates in a cyclical pattern

Why are parasites often more lethal outside of their native range?

the host population in the new region lacks defensive adaptations against foreign parasites

What is one reason that using a parasite in an attempt to control an invasive host species might be problematic?

over time, the parasite may become less deadly to the invasive species

The concept that two species cannot coexist indefinitely when they are both limited by the same resource is called

the principle of competitve exclusion

When the two diatom species Synedra and Asterionella were both grown together, eventually Synedra population numbers reached carrying capacity while Asterionella was driven to extinction.

Initially, however, both species coexisted. Why was coexistence of both species followed by extinction of one of the two species?

Initially, there was enough of the resource (silica) for both species, but eventually one species outcompeted the other for the limiting resource.

Dead leaves that fall from trees in the autumn and will not be regenerated until the following spring are an example of

a renewable resource

A forest herbaceous layer that has been invaded by garlic mustard is an example of

both interspecific and intraspecific competition

What is NOT true about garlic mustard?

garlic mustard is a highly effective competitor in wetlands

If two species require the same limiting resource, what would you predict about their ability to coexist?

they will be unable to coexist, whether the resource is renewable or nonrenewable

How is Leibig's law of the minimum related to a population's growth?

it states that a population increases until the most limiting resource prevents further increase

Which resource is a nonrenewable resource?

space

David Tilman's study of two diatom species, each with differing abilities to utilize different levels of multiple resources, showed that

coexistence is possible if each species is more efficient at using a different resource than the other species.

The Lotka‐Volterra competition equations have four possible outcomes.

Three of four possibilities have definite outcomes, while one outcome is contingent on

the initial population sizes of the two populations

In a forest, there is a population of gray squirrels and a population of chipmunks. The population of gray squirrels is 150 and the population of chipmunks is 100.

Based on your understanding of the Lotka‐Volterra competition model, if the carrying capacity of the forest for gray squirrels is 300, what will the population of gray squirrels be when carrying capacity is reached?

cannot be determined without knowing the competition coefficients

The competition coefficient value for a species would be higher if that species

were a better competitor for the resource in question

In the Lotka‐Volterra Competition model, what is true about the competition coefficient of species-2 relative to the number of species-1 when carrying capacity is reached for species-1?

The higher the competition coefficient of species-2, the lower the population size of species 1 is when carrying capacity is reached

In the Lotka-Volterra Competition model what is true about carrying capacity for species-1?

Carrying capacity for species-1 is determined by the number of individuals of species-1 and the number of individuals of species-2 (the competitor).

The logistic growth equation that forms the basis for the Lotka‐Volterra Competition equations can be calculated using all variables EXCEPT

the mortality rate of the population in question

Under what conditions can two species competing for two resources coexist?

when each species can persist at a lower level of one of the two different resources

Explain the concept of "competition coefficients" that are used in the Lotka–Volterra competition equations.

they convert the number of individuals between the two competing species into equivalents

Why do closely related species often experience more intense competition than distantly related species?

closely related species are more likely to rely on the same limiting resource

Why are population growth rates at zero when two species are at equilibrium?

at equilibrium, both species have reached carryng capacity for the particular resource

Cornell’s work with barnacles in the intertidal zone of Great Britain provided evidence that

abiotic factors have a role to play in determining the outcome of competition

The brain worm parasite is commonly found in white-tailed deer with little impact, but can be transmitted via intermediary hosts to moose with often fatal consequences.

This is an example of

apparent competition

The common crow (Corvus brachyrhynchos) and a turkey vulture (Cathartes aura) both vying for the same dead animal carcass on the road by chasing each other away would be an example of

interference competition

Apparent competition

occurs when two species have a negative effect on each other through an enemy

Why is allelopathy considered a form of interference competition?

it allows a species to prevent its competitors from competing effectively

Exploitative competition

causes the abundance of a resource to fall lower than other species can use

In the Lotka-Volterra competition model, under which circumstance can two species coexist?

when intraspecific competition is greater than interspecific competition

What are competition coefficients?

variables that mathematically describe the conversion of the number of individuals from one species to the number of individuals of the other species

What does the Lotka-Volterra competition model mathematically describe?

the competition for a limiting resource between two species

It is thought that the bird known as the greater honeyguide (Indicator indicator) is an example of _____ mutualism between itself and a species of _____.

facultative ; mammal

How are the nodules on the roots of pea plants an example of mutualism?

the nodule is formed by the plant to enclose nitrogen-fixing Rhizobium bacteria

Algae found inside developing eggs of the spotted salamander (Ambystoma maculata) obtain oxygen from the algae, allowing the eggs to develop more quickly and attain a larger size at hatching, while the salamander egg provides protection for the algae.

This would be considered what type of mutualism?

facultative

Lichens are an example of mutualism because

the fungus provides nutrients to the algae

If increased fitness of the individual is represented by (+), decreased fitness of the individual is (-), and no change in the fitness of the individual is (0), mutualism for individuals of species A and B (A,B) would be represented as

(+,+)