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unit 3 - Flashcards

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Class:Bisc 322 - General Ecology
Subject:Biology
University:University of Mississippi Main Campus
Term:Fall 2011
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Competition-

  an interaction between 2 species in which each is harmed when they both use a resource that limits their ability to grow and reproduce.

Intraspecific competition

competition between individuals of a single species. The resources available to members of a high-density population can be reduced to such an extent that growth, survival, or fertility decreases or migration increases. This can cause density dependent reductions in population size

Interspecific competition-

 competiotion between members of different species.

Resources

- features of the environment that are required for growth, reproduction and survival, and which can be consumed or otherwise used to the point of depletion

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Physical factors

- features of the environment that affect population growth rates but are not consumed or depleted

Exploitation competition-

 occurs in which species compete indirectly through their mutual effects on that availability of a shared resource

Allelopathy-

 interference competition may take this form, in which individuals of one species release toxins that harm individuals of other species

Zero population growth isoclines

- the population does not increase or decrease in size for any combination of N1 and N2 that lies in these lines

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Fugitive species

- species that must disperse from one place to another as environmental changes occur

Character displacement-

 occurs when competition causes the forms of competing species to evolve to become more different over time

Exploitation-

 a relationship in which one organism benefits by feeding on, and thus directly harming, another

Herbivore

- eats the tissue or internal fluids of living plants or algae

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Predator-

 kills and eats other organisms

Parasite

- typically lives in or on another organism feeding on parts of the host such as its tissues or body fluids. They usually harm but do not kill the organism they feed on

Parasitoids

- insects that typically lay one or few eggs on or in another insect. After they hatch they remain as parasitoid larvae and eat and usually kill the host

Sit-and-wait predators-

sit in one place and attack prey that move within striking distance

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Warning coloration-

(aposematic) species that contain toxins are usually brightly colored

Mimicry-

 resemble less palatable organisms or physical features of the environment

Crypsis-

 a type of mimicry that provides camouflage from a certain shape or coloration

Compensation-

occurs when removal of plant tissue stimulates the plant to produce new tissue, allowing for relatively rapid replacement of the material eaten by the herbivores

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Secondary compounds

- plants produce a wide variety of chemicals that function to reduce herbivory

Induced defense-

when secondary compounds are stimulated by herbivore attack

Symbionts-

 live in or on other organisms

Parasite

- consumes the tissue or body fluid of host. Some that cause disease are called pathogens

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Macroparasites-

 large parasites

Microparasites-

small parasites

Ectoparasite-

 lives on the outer body surface of its host

Hemiparasites-

 extract water and mineral nutrients from host

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Endoparasites-

 live inside host and include species that inhabit the alimentary canal as well as species that live within host cells or tissues

Coevolution-

occurs when populations of two interacting species evolve together, each in response to selection imposed by the other

Gene-for-gene interactions

- plant defense systems include a specific response that makes particular pant genotypes resistant to particular parasite genotypes

Latent period

- when an individual is infected but cannot spread the disease

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Vertical transmission

-the spread of the disease from mother to new born

Positive interactions-

those in which both species benefit 

Mutualism

- is a mutally beneficial interaction between individuals of 2 species

Commensalism-

is an interaction between two species of one specie benefits and the other is not harmed or gains anything

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Symbiosis

- a relationship in which 2 species live in close physiological contact with each other

Mycorrhizae

- symbiotic associations between plant roots and various types of fungi that are usually mutualistic

Tomycorrhizae

- a type of mycorrhizae in which fungus typically grows between root cells and forms a mantle around the exterior of the root

Arbuscular mycorrhizae

- those in which the fungus grows into the soil, extending some distance away from the root, and also grows between some root cells while penetrating others

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Nurse plants-

a plant that nurses the seedling with shade

Trophic mutualisms

- in which a mutualist receives its energy or nutrients from its partner

Habitat mutualism-

 one partner provides the other with shelter or favorable hanitat

Service mutualism-

 includes interactions in which one partner performs an ecological service for the other

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Cheaters-

 individuals that increase their production of  offspring by overexploiting their mutualistic partner

e. All of the above can be resources. Which of the following cannot be a resource for an organism?  a. Carbon dioxide  b. Physical space  c. Light  d. Another organism  e. All of the above can be resources.
c. 80 Two species of flour beetles, Tribolium castaneum and Tribolium confuum, are competing according to the Lotka–Volterra equations. If the α of T. confuum on T. castaneum is 0.4, one can assume that the addition of 200 T. confuumi individuals would depress the population growth of T. castaneum by the same amount as the addition of _______ T. castaneum individuals would.  a. 0  b. 40  c. 80  d. 200  e. 400
b. Only species C and species D There are two pairs of competing species of ferns. Species A and species B have carrying capacities of 10,000 and 6,000, respectively. The competition coefficient of species A on species B is 0.25 and the competition coefficient of species B on species A is 2.5. Species C and species D have carrying capacities of 8,000 and 14,000, respectively. The competition coefficient of species C on species D is 0.1 and the competition coefficient of species D on species C is 0.2. Based on the Lotka–Volterra equation, which of these pairs of species can coexist?  a. Only species A and species B  b. Only species C and species D  c. Both pairs of species can coexist.  d. Neither pair of species can coexist.  e. Insufficient information has been given to answer this question.
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e. Periodic disturbances Which of the following would most likely contribute to the long-term persistence of a fugitive species?  a. Character displacement  b. Apparent competition  c. Allelopathy  d. Competitive exclusion  e. Periodic disturbances
a. Competition for light is an important factor in their competition with noncarnivorous neighbors.
Which of the following conclusions can be drawn from Brewer’s experiments on pitcher plants?  a. Competition for light is an important factor in their competition with noncarnivorous neighbors.  b. Competition for nitrogen is an important factor in their competition with noncarnivorous neighbors.  c. The plants were at a particular disadvantage when noncarnivorous neighbors were left intact and the pitchers were starved.  d. Both a and c  e. Both b and c
c. Character displacement
Two species of Drosophila have been competing in the lab for a long time. A researcher notes that over the course of time, the competition coefficients of these species have become smaller. What is the most likely explanation of this change?  a. Periodic disturbances  b. Allelopathy  c. Character displacement  d. Competitive exclusion  e. None of the above
b. 2/3 A population of Teleopsis (a stalk-eyed fly) with 20,000 individuals and a carrying capacity of 40,000 follows the logistic growth equation. Its growth rate under ideal low-density conditions is 0.2 per day. The addition of 30,000 houseflies is enough to bring the population growth of Teleopsis to zero. What is the competition coefficient of the effect of the housefly on Teleopsis?  a. 1/3  b. 2/3  c. 1  d. 3/2  e. 2
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a. Interference Two species of birds actively fight over berries. Injuries have been observed, and the presence of one species limits the survival and reproduction of the other. What type of competition is this?  a. Interference  b. Exploitative  c. Allelopathy  d. Logistic  e. None of the above; this is not an example of competition.
b. 25 A population of white oak trees with 500 individuals and a carrying capacity of 1,500 follows logistic growth. Under ideal low-density conditions, its growth rate is 0.15 per year, but it faces competition from a population of 1,000 Chapmann oaks with an α of 0.5. What is the expected growth of the population of white oaks in the next year?  a. 0  b. 25  c. 50  d. 75  e. 100
a. there is substantial overlap in the seeds eaten by ants and rodents.
Brown and Davidson’s study of a desert community showed that  a. there is substantial overlap in the seeds eaten by ants and rodents.  b. exclusion of rodents leads to a decrease of ant colonies.  c. exclusion of both ants and rodents has little effect on the availability of seeds.  d. All of the above  e. None of the above
d. Both competition and physical factors can limit the local distribution of species. The results of Connell’s experiments with intertidal barnacles support which of the following principles of competition?  a. Evolution by natural selection can alter the outcome of competition.  b. Periodic disturbances that remove a superior competitor can allow inferior competitors to persist.  c. Exploitative competition is the most common form of competition in nature.  d. Both competition and physical factors can limit the local distribution of species.  e. None of the above
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e. Within species, individuals that resemble their competitors the most have a selective disadvantage. Which of the following observations would be the strongest evidence that character displacement is occurring?  a. The intensity of competition increases as resources become more scarce.  b. Competing species are more morphologically similar when apart than they are when they are together.  c. The outcome of competition reverses after a period of time.  d. Within species, individuals that resemble their competitors the most have a selective advantage.  e. Within species, individuals that resemble their competitors the most have a selective disadvantage.
c. 1 The competition coefficient of one species on itself is, by definition,  a. zero.  b. 1/2.  c. 1  d. –1.  e. variable.
d. Both a and b Which of the following statements about allelopathy is true?  a. It is a form of interference competition.  b. It occurs when individuals of one species release chemicals that harm individuals of another species.  c. It is a form of character displacement.  d. Both a and b  e. None of the above
b. The complexity of the habitat In Huffaker’s studies of an herbivorous mite and its mite predator, which of the following variables was critical in determining whether the populations of predator and prey would go extinct quickly or persist?  a. Whether natural selection was operating to influence the population cycles  b. The complexity of the habitat  c. The nature of the prey’s stress response  d. Whether the prey had aposematic coloration  e. Whether the predators were “sit-and-wait” or active
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d. decrease; have no effect on n a predator–prey system functioning according to Lotka–Volterra dynamics, an increase in the efficiency (b) by which prey biomass is converted into predator biomass should _______ the long-term average number of prey, and _______ the long-term average number of predators.  a. increase; increase  b. increase; decrease  c. have no effect on; increase  d. decrease; have no effect on  e. decrease; increase
b. algae evolve in response to predation. Hairston and colleagues found that the best explanation for the observed patterns of population dynamics of rotifers and their algal prey was that  a. the accumulation of toxins alters algal physiology.  b. algae evolve in response to predation.  c. rotifer egg viability increases with prey density.  d. high levels of nitrogen increase algal nutritional quality.  e. None of the above
e. Both b and c Which of the following factors most likely explains the synchrony of the hare population cycles in geographically distant areas?  a. Movement of hares  b. Movement of lynx  c. Similarity of climate in these geographically distant areas  d. Both a and b  e. Both b and c
a. above 125. Suppose that a lizard species eats only one type of insect and the populations follow Lotka–Volterra dynamics. The intrinsic growth rate of insects in the absence of predators is 0.2 per week, and the mortality rate of the lizards in the absence of insects is 0.05 per week. The capture efficiency rate is 0.002, and the efficiency at which insect biomass is converted into predator biomass is 0.2. The lizard population will increase only if the number of insects is  a. above 125.  b. above 500.  c. above 625.  d. below 125.  e. below 625.
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d. Both a and b The population cycles of collard lemmings are driven by  a. predators of lemmings.  b. food organisms of lemmings.  c. decomposers.  d. Both a and b  e. None of the above
c. a decrease; a decrease In the Lotka–Volterra predator–prey model, an increase in the capture efficiency (a) should lead to _______ in the long-term average number of predators and _______ in the long-term average number of prey.  a. an increase; a decrease  b. an increase; no change  c. a decrease; a decrease  d. no change; no change  e. a decrease; an increase
d. Lizards introduced > lizards natural > lizards absent Based on Schoener and Spiller’s studies of spider densities in the Bahamas, what is the correct ranking (from highest to lowest) of the probability of spiders going extinct according to three different conditions: islands on which lizards are absent from the islands, islands on which lizards have been introduced to the islands, and islands on which lizards are present naturally?  a. Lizards absent > lizards introduced > lizards natural  b. Lizards absent > lizards natural > lizards introduced  c. Lizards introduced > lizards absent > lizards natural  d. Lizards introduced > lizards natural > lizards absent  e. Lizards natural > lizards introduced > lizards absent
e. All of the above are true; none is false. Which of the following statements about the effects of herbivory on tobacco is false?  a. Tobacco produces secondary compounds that directly deter herbivores.  b. Tobacco produces secondary compounds that deter herbivores indirectly by attracting predators of the herbivores.  c. At least some of the secondary compounds produced by tobacco are induced defenses.  d. Silencing of a single gene in tobacco reduces plant defenses and thus increases herbivory.  e. All of the above are true; none is false.
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b. Most parasites and parasitoids spend their entire lives consuming a single individual, whereas herbivores and predators usually eat at least several different individuals. How do predation and herbivory differ from parasitism and parasitoidism?  a. Parasitism and parasitoidism are not exploitative relationships.  b. Most parasites and parasitoids spend their entire lives consuming a single individual, whereas herbivores and predators usually eat at least several different individuals.  c. Unlike parasitoids and parasites, predators and herbivores usually do not exert strong selective pressures on their food organisms.  d. Both a and b  e. Both b and c
e. below 100. Suppose that a lizard species eats only one type of insect and the populations follow Lotka–Volterra dynamics. The intrinsic growth rate of insects in the absence of predators is 0.2 per week, and the mortality rate of the lizards in the absence of insects is 0.05 per week. The capture efficiency rate is 0.002, and the efficiency at which insect biomass is converted into predator biomass is 0.2. The insect population size will increase only if the number of lizards is  a. above 50.  b. above 100.  c. above 200  d. below 50.  e. below 100.
d. the efficiency at which prey biomass is converted into predator offspring. In the Lotka–Volterra predator–prey model, b represents  a. the birth rate of prey.  b. the population growth rate of prey in the absence of predators.  c. the death rate of predators.  d. the efficiency at which prey biomass is converted into predator offspring.  e. the capture efficiency of prey by predators.
a. A broad diet is more typical of a predator than of an herbivore. Which of the following statements about predators and herbivores is true?  a. A broad diet is more typical of a predator than of an herbivore.  b. Only herbivores eat seeds more than any other plant part.  c. There are few herbivorous insects.  d. All of the above  e. None of the above
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b. Some garter snakes are resistant to TTX due to TTX-resistant sodium channels in their neurons. Which of the following statements about garter snakes and TTX is true?  a. Some garter snakes produce TTX.  b. Some garter snakes are resistant to TTX due to TTX-resistant sodium channels in their neurons.  c. Snakes that are resistant to TTX move more quickly than other snakes.  d. Both a and b  e. Both b and c
a. The trematode preferentially infects snails with rare genotypes. Which of the following statements about the studies by Dybdahl and Lively on snails and their parasites is false?  a. The trematode preferentially infects snails with rare genotypes.  b. Parasites evolve more quickly in response to snails than snails evolve to parasites.  c. The trematode worm castrates males and sterilizes females.  d. The snail genotype that was most abundant at one point often changed from year to year.  e. All of the above are true; none is false.
d. 2 The transmission coefficient of the hypothetical disease Dumas fever is 0.2. If the combined death and recovery rate is 0.4, what is the threshold density for Dumas fever?  a. 0.08  b. 0.5  c. 0.8  d. 2  e. 20
e. Both b and c How do malarial parasites change the red blood cells of their hosts in order to obtain nutrients and avoid destruction?  a. They inject viruses into red blood cells, which makes the cells “invisible” to the host immune system.  b. They cause the red blood cells to stick to other human cells, thus preventing the red blood cells from traveling in the blood stream.  c. They cause transport proteins to be placed on the surface of the red blood cells, enabling more nutrients to be imported into the host cell.  d. Both a and b  e. Both b and c
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e. lower; lower Suppose that a time machine allows you to go back in time (and to travel to Australia!), and you have collected rabbits and Myxoma from the years 1955 and 1980. Once you are back in the twenty-first century, you infect both sets of rabbits with both sets of myxoma viruses. The most likely result will be (1) that the rabbits from 1955 injected with the 1955 virus will have a _______ survival rate than those same rabbits injected with the 1980 virus; and (2) that the rabbits from 1955 injected with the 1980 virus will have a _______ survival rate than rabbits from 1980 injected with the 1980 virus.  a. higher; higher  b. higher; lower  c. similar; higher  d. lower; higher  e. lower; lower
e. resistance genes Some plants protect themselves against specific parasites by means of _______. This defense system works much like the memory cells of the vertebrate immune system.  a. lignins  b. scolexes  c. immunity genes  d. merozoites  e. resistance genes
e. Both b and c Eberhard’s study of spiders and their parasitoid wasps showed that  a. the wasps most likely change the web-building behavior of the spider by the injection of a fast-acting chemical.  b. the type of web built is an all-or-nothing phenomenon; it is either a normal web or a cocoon web.  c. the behaviors in spiders that build cocoon webs contain some of the same elements as those that build normal webs.  d. Both a and b  e. Both b and c
b. parasites can drive host populations to extinction. The interactions between the American chestnut and the parasitic fungus Cryphonectria parasitica best exemplify the principle that  a. there are costs to both host defenses and parasite counterdefenses.  b. parasites can drive host populations to extinction.  c. parasites can influence host population cycles.  d. selection can favor a diversity of host and parasite genotypes.  e. vaccination can reduce the incidence of disease.
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c. 50 According to the basic host–pathogen model of disease, if susceptible and infected individuals are the only types of individuals in a population, then disease transmission is greatest when susceptible individuals are _______ percent of the population. [Hint: If the density remains the same, when is SI maximized?]  a. 10  b. 25  c. 50  d. 90  e. 99
c. an increase; parasite Evolution in a parasite from ectoparasitism to endoparasitism would most likely be caused by _______ in the number or intensity of natural enemies of the _______.  a. an increase; host  b. a decrease; host  c. an increase; parasite  d. a decrease; parasite  e. None of the above should cause any change.
b. Size Which of the following characteristics best distinguishes microparasites from macroparasites?  a. Whether they live inside the host or on the host  b. Size  c. Whether they cause disease in humans  d. Whether they infect animals or plants  e. The number of different hosts in their life cycle
c. mI In the simple host–pathogen model, which of the following terms describes the rate at which infected individuals either die or recover from the disease?  a. S  b. SI  c. mI  d. βSI  e. βmI
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c. Toxoplasma gondii Which of the following parasites alters the behavior of rats, such that they will seek out cats (which likely will capture and kill them)?  a. Plasmodium  b. Hairworm  c. Toxoplasma gondii  d. Hymenoepimecius argyraphaga  e. Myxoma
a. They can more easily disperse to other hosts. Which of the following characteristics is an advantage that ectoparasites have over endoparasites?  a. They can more easily disperse to other hosts.  b. They are less exposed to predators.  c. They are less exposed to changes in the external environment.  d. All of the above  e. None of the above
e. All of the above are true; none is false. Which of the following statements about mistletoe is false?  a. It is a hemiparasite.  b. It is an ectoparasite.  c. It relies on its host for water and mineral nutrients.  d. It can photosynthesize, and thus can generate its own carbohydrates.  e. All of the above are true; none is false.
b. commensalism. A bear accidentally carries the seeds of a weedy plant in its fur. Transporting the seeds neither helps nor harms the bear, but it is beneficial to the plant. This is an example of a(n)  a. mutualism.  b. commensalism.  c. parasitism.  d. symbiosis.  e. amensalism.
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d. Both a and c Which of the following statements about the effects of leaf-cutter ants on ecosystems is true?  a. Soils beneath ant colonies are much richer in calcium and potassium than soils distant from ant colonies.  b. Soils beneath ant colonies are much poorer in calcium and potassium than soils distant from ant colonies.  c. The net effect of ant colonies on NPP is difficult to estimate; at this time, it is not conclusively known to be positive or negative.  d. Both a and c  e. Both b and c
b. never; little to no A commensalism is _______ obligatory for the species that does not receive any benefits; _______ coevolution occurs in commensalisms.  a. never; significant  b. never; little to no  c. sometimes; significant  d. sometimes; little to no  e. always; significant
c. Yucca plants of the yucca–yucca moth system
Which of the following species has been documented as imposing penalties on individuals of its mutualistic partner that are engaged in overexploitation?  a. Figs of the fig–fig wasp system  b. Fig wasps of the fig–fig wasp system  c. Yucca plants of the yucca–yucca moth system  d. Yucca moths of the yucca–yucca moth system  e. None of the above
d. Both a and b
In its mutualistic interactions with leaf-cutter ants, a bacterium produces fungicides against a fungal pathogen and receives, as a benefit,  a. a place to live.  b. food from glandular secretions.  c. defense against phages.  d. Both a and b  e. Both b and c
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b. increase at first and then level off as the number of fungal species was increased. In the study by van der Heijden and colleagues of mycorrhizal fungi, the root biomass of the target plants was found to  a. increase steadily as the number of fungal species was increased.  b. increase at first and then level off as the number of fungal species was increased.  c. be highest when the fungal species were at an intermediate level.  d. be high when there were only a few fungal species present and then to decrease as more were added.  e. be largely constant, regardless of the number of fungal species present.
e. Both a and c A wasp pollinating a plant in exchange for food is an example of a _______ mutualism.  a. service  b. habitat  c. trophic  d. Both a and b  e. Both a and c
a. For an ecological interaction to be a mutualism, the net benefits must exceed the net costs for one partner but not the other. Which of the following statements about mutualisms is false?  a. For an ecological interaction to be a mutualism, the net benefits must exceed the net costs for one partner but not the other.  b. Species do not engage in mutualisms for altruistic reasons.  c. In some mutualisms, one or the other partner, under certain environmental conditions, will withdraw the reward it usually provides.  d. There is an inherent conflict of interest between the partners in a mutualism.  e. All of the above are true; none is false.
e. a decrease; a decrease In Grutter’s studies in the Great Barrier Reef of Australia, removal of the cleaner fish led to _______ in the number of fish species and _______ in the number of individual fish.  a. an increase; an increase  b. an increase; a decrease  c. little change; a decrease  d. a decrease; little change  e. a decrease; a decrease
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e. It is a mutualism. From the act of pollinating flowers, a wasp population gains the benefit of a 0.08 growth rate increase per month. However, the costs imposed by the flower (wasps getting stuck, time spent pollinating the flower instead of pollinating other species, etc.) is a 0.03 reduction in growth rate per month. The flower gains benefits from the pollination that enhance its population growth rate by 0.09 per month, but it incurs costs (feeding the wasps, damage done by the bees) that reduce its growth rate by 0.06 per month. Which of the following statements best describes the relationship between the bees and the flowers?  a. It is a host–parasite relationship in which the bees are the hosts and the flowers are the parasites.  b. It is a host–parasite relationship in which the flowers are the hosts and the bees are the parasites.  c. It is an amensalism.  d. It is a commensalism.  e. It is a mutualism.
d. hurt; helped An international group of scientists found that neighboring plant species generally _______ the target species at low-elevation sites and _______ the target species at high-elevation sites.  a. helped; helped  b. helped; hurt  c. had no detectable effect on; hurt  d. hurt; helped  e. hurt; hurt
d. Both a and b In Janzen’s study in which ants were removed from acacia plants, plants with ant colonies were found to _______ than plants without ants.  a. weigh more  b. survive more successfully  c. be attacked more severely by insect herbivores  d. Both a and b  e. Both a and c
zero population growth isoclines
Lines derived from the Lotka–Volterra competition model marking the conditions under which a population does not increase or decrease in size.
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resource
A feature of the environment that is required for growth, survival, or reproduction and which can be consumed or otherwise used to the point of depletion
resource partitioning
The use of limiting resources by different species in a community in different ways.
physical factor
A feature of the environment that affects organism function and population growth rates but is not consumed or depleted
Lotka–Volterra competition model
A modified form of the logistic equation used to model competition.
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interference competition
An interaction in which species compete directly by performing antagonistic actions that interfere with the ability of their competitors to use a resource that both require, such as food or space
exploitation competition
An interaction in which species compete indirectly through their mutual effects on the availability of a shared resource.
competitive exclusion principle
The principle that two species that use a limiting resource in the same way cannot coexist indefinitely.
competition
An interaction between individuals of two species in which each is harmed by their shared use of a resource that limits their ability to grow, survive, or reproduce (a –/– relationship).
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competition coefficient
A constant used in the Lotka–Volterra competition model to describe the extent to which an individual of one competing species decreases the per capita growth rate of the other species.
character displacement
A process in which competition causes the phenotypes of competing species to evolve to become more different over time, thereby causing the species to become more different where they live together than where they live apart.
compensation
An adaptive growth response of plants to herbivory in which removal of plant tissues stimulates the plant to produce new tissues.
crypsis
A defense against predators in which prey species have a shape or coloration that provides camouflage and allows them to avoid detection.
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exploitation
A relationship in which one organism benefits by feeding on, and thus directly harming, another.
induced defense
In plant–herbivore interactions, a defense against herbivory, such as production of a secondary compound, that is stimulated by herbivore attack.
mimicry
A defense against predators in which prey species resemble less palatable organisms or physical features of their environment, causing potential predators to mistake them for something less desirable to eat.
parasitoid
An insect that lays one or a few eggs on or in a host organism (itself usually an insect), which the resulting larvae remain with, eat, and almost always kill.
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secondary compound
A chemical compound in plants not used directly in growth, and often used in such functions as defense against herbivores or protection from harmful radiation.
coevolution
The evolution of two interacting species, each in response to selection pressure imposed by the other.
gene-for-gene interaction
A specific defensive response that makes particular plant genotypes resistant to particular parasite genotypes.
threshold density
The minimum number of individuals susceptible to a disease that must be present in a population for the disease to become established and spread.
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arbuscular mycorrhizae
Mycorrhizae in which the fungal partner grows into the soil, extending some distance away from the plant root, and also grows between some root cells while penetrating others.
ectomycorrhizae
Mycorrhizae in which the fungal partner typically grows between plant root cells and forms a mantle around the exterior of the root
commensalisms
An interaction between two species in which individuals of one species benefit while individuals of the other species do not benefit and are not harmed.
mycorrhizae
Symbiotic associations between plant roots and various types of fungi that are usually mutualistic.
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positive interactions
Interactions between species in which one or both species benefit and neither is harmed.
trophic mutualism
A mutualism in which one or both of the mutualists receives energy or nutrients from its partner.
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 Competition-

  an interaction between 2 species in which each is harmed when they both use a resource that limits their ability to grow and reproduce.

 Intraspecific competition

competition between individuals of a single species. The resources available to members of a high-density population can be reduced to such an extent that growth, survival, or fertility decreases or migration increases. This can cause density dependent reductions in population size

 Interspecific competition-

 competiotion between members of different species.

 Resources

- features of the environment that are required for growth, reproduction and survival, and which can be consumed or otherwise used to the point of depletion

 Physical factors

- features of the environment that affect population growth rates but are not consumed or depleted

 Exploitation competition-

 occurs in which species compete indirectly through their mutual effects on that availability of a shared resource

 Allelopathy-

 interference competition may take this form, in which individuals of one species release toxins that harm individuals of other species

 Zero population growth isoclines

- the population does not increase or decrease in size for any combination of N1 and N2 that lies in these lines

 Fugitive species

- species that must disperse from one place to another as environmental changes occur

 Character displacement-

 occurs when competition causes the forms of competing species to evolve to become more different over time

 Exploitation-

 a relationship in which one organism benefits by feeding on, and thus directly harming, another

 Herbivore

- eats the tissue or internal fluids of living plants or algae

 Predator-

 kills and eats other organisms

 Parasite

- typically lives in or on another organism feeding on parts of the host such as its tissues or body fluids. They usually harm but do not kill the organism they feed on

 Parasitoids

- insects that typically lay one or few eggs on or in another insect. After they hatch they remain as parasitoid larvae and eat and usually kill the host

 Sit-and-wait predators-

sit in one place and attack prey that move within striking distance

 Warning coloration-

(aposematic) species that contain toxins are usually brightly colored

 Mimicry-

 resemble less palatable organisms or physical features of the environment

 Crypsis-

 a type of mimicry that provides camouflage from a certain shape or coloration

 Compensation-

occurs when removal of plant tissue stimulates the plant to produce new tissue, allowing for relatively rapid replacement of the material eaten by the herbivores

 Secondary compounds

- plants produce a wide variety of chemicals that function to reduce herbivory

 Induced defense-

when secondary compounds are stimulated by herbivore attack

 Symbionts-

 live in or on other organisms

 Parasite

- consumes the tissue or body fluid of host. Some that cause disease are called pathogens

 Macroparasites-

 large parasites

 Microparasites-

small parasites

 Ectoparasite-

 lives on the outer body surface of its host

 Hemiparasites-

 extract water and mineral nutrients from host

 Endoparasites-

 live inside host and include species that inhabit the alimentary canal as well as species that live within host cells or tissues

 Coevolution-

occurs when populations of two interacting species evolve together, each in response to selection imposed by the other

 Gene-for-gene interactions

- plant defense systems include a specific response that makes particular pant genotypes resistant to particular parasite genotypes

 Latent period

- when an individual is infected but cannot spread the disease

 Vertical transmission

-the spread of the disease from mother to new born

 Positive interactions-

those in which both species benefit 

 Mutualism

- is a mutally beneficial interaction between individuals of 2 species

 Commensalism-

is an interaction between two species of one specie benefits and the other is not harmed or gains anything

 Symbiosis

- a relationship in which 2 species live in close physiological contact with each other

 Mycorrhizae

- symbiotic associations between plant roots and various types of fungi that are usually mutualistic

 Tomycorrhizae

- a type of mycorrhizae in which fungus typically grows between root cells and forms a mantle around the exterior of the root

 Arbuscular mycorrhizae

- those in which the fungus grows into the soil, extending some distance away from the root, and also grows between some root cells while penetrating others

 Nurse plants-

a plant that nurses the seedling with shade

 Trophic mutualisms

- in which a mutualist receives its energy or nutrients from its partner

 Habitat mutualism-

 one partner provides the other with shelter or favorable hanitat

 Service mutualism-

 includes interactions in which one partner performs an ecological service for the other

 Cheaters-

 individuals that increase their production of  offspring by overexploiting their mutualistic partner

 e. All of the above can be resources.Which of the following cannot be a resource for an organism?  a. Carbon dioxide  b. Physical space  c. Light  d. Another organism  e. All of the above can be resources.
 c. 80Two species of flour beetles, Tribolium castaneum and Tribolium confuum, are competing according to the Lotka–Volterra equations. If the α of T. confuum on T. castaneum is 0.4, one can assume that the addition of 200 T. confuumi individuals would depress the population growth of T. castaneum by the same amount as the addition of _______ T. castaneum individuals would.  a. 0  b. 40  c. 80  d. 200  e. 400
 b. Only species C and species DThere are two pairs of competing species of ferns. Species A and species B have carrying capacities of 10,000 and 6,000, respectively. The competition coefficient of species A on species B is 0.25 and the competition coefficient of species B on species A is 2.5. Species C and species D have carrying capacities of 8,000 and 14,000, respectively. The competition coefficient of species C on species D is 0.1 and the competition coefficient of species D on species C is 0.2. Based on the Lotka–Volterra equation, which of these pairs of species can coexist?  a. Only species A and species B  b. Only species C and species D  c. Both pairs of species can coexist.  d. Neither pair of species can coexist.  e. Insufficient information has been given to answer this question.
 e. Periodic disturbancesWhich of the following would most likely contribute to the long-term persistence of a fugitive species?  a. Character displacement  b. Apparent competition  c. Allelopathy  d. Competitive exclusion  e. Periodic disturbances
 a. Competition for light is an important factor in their competition with noncarnivorous neighbors.
Which of the following conclusions can be drawn from Brewer’s experiments on pitcher plants?  a. Competition for light is an important factor in their competition with noncarnivorous neighbors.  b. Competition for nitrogen is an important factor in their competition with noncarnivorous neighbors.  c. The plants were at a particular disadvantage when noncarnivorous neighbors were left intact and the pitchers were starved.  d. Both a and c  e. Both b and c
 c. Character displacement
Two species of Drosophila have been competing in the lab for a long time. A researcher notes that over the course of time, the competition coefficients of these species have become smaller. What is the most likely explanation of this change?  a. Periodic disturbances  b. Allelopathy  c. Character displacement  d. Competitive exclusion  e. None of the above
 b. 2/3A population of Teleopsis (a stalk-eyed fly) with 20,000 individuals and a carrying capacity of 40,000 follows the logistic growth equation. Its growth rate under ideal low-density conditions is 0.2 per day. The addition of 30,000 houseflies is enough to bring the population growth of Teleopsis to zero. What is the competition coefficient of the effect of the housefly on Teleopsis?  a. 1/3  b. 2/3  c. 1  d. 3/2  e. 2
 a. InterferenceTwo species of birds actively fight over berries. Injuries have been observed, and the presence of one species limits the survival and reproduction of the other. What type of competition is this?  a. Interference  b. Exploitative  c. Allelopathy  d. Logistic  e. None of the above; this is not an example of competition.
 b. 25A population of white oak trees with 500 individuals and a carrying capacity of 1,500 follows logistic growth. Under ideal low-density conditions, its growth rate is 0.15 per year, but it faces competition from a population of 1,000 Chapmann oaks with an α of 0.5. What is the expected growth of the population of white oaks in the next year?  a. 0  b. 25  c. 50  d. 75  e. 100
 a. there is substantial overlap in the seeds eaten by ants and rodents.
Brown and Davidson’s study of a desert community showed that  a. there is substantial overlap in the seeds eaten by ants and rodents.  b. exclusion of rodents leads to a decrease of ant colonies.  c. exclusion of both ants and rodents has little effect on the availability of seeds.  d. All of the above  e. None of the above
 d. Both competition and physical factors can limit the local distribution of species.The results of Connell’s experiments with intertidal barnacles support which of the following principles of competition?  a. Evolution by natural selection can alter the outcome of competition.  b. Periodic disturbances that remove a superior competitor can allow inferior competitors to persist.  c. Exploitative competition is the most common form of competition in nature.  d. Both competition and physical factors can limit the local distribution of species.  e. None of the above
 e. Within species, individuals that resemble their competitors the most have a selective disadvantage.Which of the following observations would be the strongest evidence that character displacement is occurring?  a. The intensity of competition increases as resources become more scarce.  b. Competing species are more morphologically similar when apart than they are when they are together.  c. The outcome of competition reverses after a period of time.  d. Within species, individuals that resemble their competitors the most have a selective advantage.  e. Within species, individuals that resemble their competitors the most have a selective disadvantage.
 c. 1The competition coefficient of one species on itself is, by definition,  a. zero.  b. 1/2.  c. 1  d. –1.  e. variable.
 d. Both a and bWhich of the following statements about allelopathy is true?  a. It is a form of interference competition.  b. It occurs when individuals of one species release chemicals that harm individuals of another species.  c. It is a form of character displacement.  d. Both a and b  e. None of the above
 b. The complexity of the habitatIn Huffaker’s studies of an herbivorous mite and its mite predator, which of the following variables was critical in determining whether the populations of predator and prey would go extinct quickly or persist?  a. Whether natural selection was operating to influence the population cycles  b. The complexity of the habitat  c. The nature of the prey’s stress response  d. Whether the prey had aposematic coloration  e. Whether the predators were “sit-and-wait” or active
 d. decrease; have no effect onn a predator–prey system functioning according to Lotka–Volterra dynamics, an increase in the efficiency (b) by which prey biomass is converted into predator biomass should _______ the long-term average number of prey, and _______ the long-term average number of predators.  a. increase; increase  b. increase; decrease  c. have no effect on; increase  d. decrease; have no effect on  e. decrease; increase
 b. algae evolve in response to predation.Hairston and colleagues found that the best explanation for the observed patterns of population dynamics of rotifers and their algal prey was that  a. the accumulation of toxins alters algal physiology.  b. algae evolve in response to predation.  c. rotifer egg viability increases with prey density.  d. high levels of nitrogen increase algal nutritional quality.  e. None of the above
 e. Both b and cWhich of the following factors most likely explains the synchrony of the hare population cycles in geographically distant areas?  a. Movement of hares  b. Movement of lynx  c. Similarity of climate in these geographically distant areas  d. Both a and b  e. Both b and c
 a. above 125.Suppose that a lizard species eats only one type of insect and the populations follow Lotka–Volterra dynamics. The intrinsic growth rate of insects in the absence of predators is 0.2 per week, and the mortality rate of the lizards in the absence of insects is 0.05 per week. The capture efficiency rate is 0.002, and the efficiency at which insect biomass is converted into predator biomass is 0.2. The lizard population will increase only if the number of insects is  a. above 125.  b. above 500.  c. above 625.  d. below 125.  e. below 625.
 d. Both a and bThe population cycles of collard lemmings are driven by  a. predators of lemmings.  b. food organisms of lemmings.  c. decomposers.  d. Both a and b  e. None of the above
 c. a decrease; a decreaseIn the Lotka–Volterra predator–prey model, an increase in the capture efficiency (a) should lead to _______ in the long-term average number of predators and _______ in the long-term average number of prey.  a. an increase; a decrease  b. an increase; no change  c. a decrease; a decrease  d. no change; no change  e. a decrease; an increase
 d. Lizards introduced > lizards natural > lizards absentBased on Schoener and Spiller’s studies of spider densities in the Bahamas, what is the correct ranking (from highest to lowest) of the probability of spiders going extinct according to three different conditions: islands on which lizards are absent from the islands, islands on which lizards have been introduced to the islands, and islands on which lizards are present naturally?  a. Lizards absent > lizards introduced > lizards natural  b. Lizards absent > lizards natural > lizards introduced  c. Lizards introduced > lizards absent > lizards natural  d. Lizards introduced > lizards natural > lizards absent  e. Lizards natural > lizards introduced > lizards absent
 e. All of the above are true; none is false.Which of the following statements about the effects of herbivory on tobacco is false?  a. Tobacco produces secondary compounds that directly deter herbivores.  b. Tobacco produces secondary compounds that deter herbivores indirectly by attracting predators of the herbivores.  c. At least some of the secondary compounds produced by tobacco are induced defenses.  d. Silencing of a single gene in tobacco reduces plant defenses and thus increases herbivory.  e. All of the above are true; none is false.
 b. Most parasites and parasitoids spend their entire lives consuming a single individual, whereas herbivores and predators usually eat at least several different individuals.How do predation and herbivory differ from parasitism and parasitoidism?  a. Parasitism and parasitoidism are not exploitative relationships.  b. Most parasites and parasitoids spend their entire lives consuming a single individual, whereas herbivores and predators usually eat at least several different individuals.  c. Unlike parasitoids and parasites, predators and herbivores usually do not exert strong selective pressures on their food organisms.  d. Both a and b  e. Both b and c
 e. below 100.Suppose that a lizard species eats only one type of insect and the populations follow Lotka–Volterra dynamics. The intrinsic growth rate of insects in the absence of predators is 0.2 per week, and the mortality rate of the lizards in the absence of insects is 0.05 per week. The capture efficiency rate is 0.002, and the efficiency at which insect biomass is converted into predator biomass is 0.2. The insect population size will increase only if the number of lizards is  a. above 50.  b. above 100.  c. above 200  d. below 50.  e. below 100.
 d. the efficiency at which prey biomass is converted into predator offspring.In the Lotka–Volterra predator–prey model, b represents  a. the birth rate of prey.  b. the population growth rate of prey in the absence of predators.  c. the death rate of predators.  d. the efficiency at which prey biomass is converted into predator offspring.  e. the capture efficiency of prey by predators.
 a. A broad diet is more typical of a predator than of an herbivore.Which of the following statements about predators and herbivores is true?  a. A broad diet is more typical of a predator than of an herbivore.  b. Only herbivores eat seeds more than any other plant part.  c. There are few herbivorous insects.  d. All of the above  e. None of the above
 b. Some garter snakes are resistant to TTX due to TTX-resistant sodium channels in their neurons.Which of the following statements about garter snakes and TTX is true?  a. Some garter snakes produce TTX.  b. Some garter snakes are resistant to TTX due to TTX-resistant sodium channels in their neurons.  c. Snakes that are resistant to TTX move more quickly than other snakes.  d. Both a and b  e. Both b and c
 a. The trematode preferentially infects snails with rare genotypes.Which of the following statements about the studies by Dybdahl and Lively on snails and their parasites is false?  a. The trematode preferentially infects snails with rare genotypes.  b. Parasites evolve more quickly in response to snails than snails evolve to parasites.  c. The trematode worm castrates males and sterilizes females.  d. The snail genotype that was most abundant at one point often changed from year to year.  e. All of the above are true; none is false.
 d. 2The transmission coefficient of the hypothetical disease Dumas fever is 0.2. If the combined death and recovery rate is 0.4, what is the threshold density for Dumas fever?  a. 0.08  b. 0.5  c. 0.8  d. 2  e. 20
 e. Both b and cHow do malarial parasites change the red blood cells of their hosts in order to obtain nutrients and avoid destruction?  a. They inject viruses into red blood cells, which makes the cells “invisible” to the host immune system.  b. They cause the red blood cells to stick to other human cells, thus preventing the red blood cells from traveling in the blood stream.  c. They cause transport proteins to be placed on the surface of the red blood cells, enabling more nutrients to be imported into the host cell.  d. Both a and b  e. Both b and c
 e. lower; lowerSuppose that a time machine allows you to go back in time (and to travel to Australia!), and you have collected rabbits and Myxoma from the years 1955 and 1980. Once you are back in the twenty-first century, you infect both sets of rabbits with both sets of myxoma viruses. The most likely result will be (1) that the rabbits from 1955 injected with the 1955 virus will have a _______ survival rate than those same rabbits injected with the 1980 virus; and (2) that the rabbits from 1955 injected with the 1980 virus will have a _______ survival rate than rabbits from 1980 injected with the 1980 virus.  a. higher; higher  b. higher; lower  c. similar; higher  d. lower; higher  e. lower; lower
 e. resistance genesSome plants protect themselves against specific parasites by means of _______. This defense system works much like the memory cells of the vertebrate immune system.  a. lignins  b. scolexes  c. immunity genes  d. merozoites  e. resistance genes
 e. Both b and cEberhard’s study of spiders and their parasitoid wasps showed that  a. the wasps most likely change the web-building behavior of the spider by the injection of a fast-acting chemical.  b. the type of web built is an all-or-nothing phenomenon; it is either a normal web or a cocoon web.  c. the behaviors in spiders that build cocoon webs contain some of the same elements as those that build normal webs.  d. Both a and b  e. Both b and c
 b. parasites can drive host populations to extinction.The interactions between the American chestnut and the parasitic fungus Cryphonectria parasitica best exemplify the principle that  a. there are costs to both host defenses and parasite counterdefenses.  b. parasites can drive host populations to extinction.  c. parasites can influence host population cycles.  d. selection can favor a diversity of host and parasite genotypes.  e. vaccination can reduce the incidence of disease.
 c. 50According to the basic host–pathogen model of disease, if susceptible and infected individuals are the only types of individuals in a population, then disease transmission is greatest when susceptible individuals are _______ percent of the population. [Hint: If the density remains the same, when is SI maximized?]  a. 10  b. 25  c. 50  d. 90  e. 99
 c. an increase; parasiteEvolution in a parasite from ectoparasitism to endoparasitism would most likely be caused by _______ in the number or intensity of natural enemies of the _______.  a. an increase; host  b. a decrease; host  c. an increase; parasite  d. a decrease; parasite  e. None of the above should cause any change.
 b. SizeWhich of the following characteristics best distinguishes microparasites from macroparasites?  a. Whether they live inside the host or on the host  b. Size  c. Whether they cause disease in humans  d. Whether they infect animals or plants  e. The number of different hosts in their life cycle
 c. mIIn the simple host–pathogen model, which of the following terms describes the rate at which infected individuals either die or recover from the disease?  a. S  b. SI  c. mI  d. βSI  e. βmI
 c. Toxoplasma gondiiWhich of the following parasites alters the behavior of rats, such that they will seek out cats (which likely will capture and kill them)?  a. Plasmodium  b. Hairworm  c. Toxoplasma gondii  d. Hymenoepimecius argyraphaga  e. Myxoma
 a. They can more easily disperse to other hosts.Which of the following characteristics is an advantage that ectoparasites have over endoparasites?  a. They can more easily disperse to other hosts.  b. They are less exposed to predators.  c. They are less exposed to changes in the external environment.  d. All of the above  e. None of the above
 e. All of the above are true; none is false.Which of the following statements about mistletoe is false?  a. It is a hemiparasite.  b. It is an ectoparasite.  c. It relies on its host for water and mineral nutrients.  d. It can photosynthesize, and thus can generate its own carbohydrates.  e. All of the above are true; none is false.
 b. commensalism.A bear accidentally carries the seeds of a weedy plant in its fur. Transporting the seeds neither helps nor harms the bear, but it is beneficial to the plant. This is an example of a(n)  a. mutualism.  b. commensalism.  c. parasitism.  d. symbiosis.  e. amensalism.
 d. Both a and cWhich of the following statements about the effects of leaf-cutter ants on ecosystems is true?  a. Soils beneath ant colonies are much richer in calcium and potassium than soils distant from ant colonies.  b. Soils beneath ant colonies are much poorer in calcium and potassium than soils distant from ant colonies.  c. The net effect of ant colonies on NPP is difficult to estimate; at this time, it is not conclusively known to be positive or negative.  d. Both a and c  e. Both b and c
 b. never; little to noA commensalism is _______ obligatory for the species that does not receive any benefits; _______ coevolution occurs in commensalisms.  a. never; significant  b. never; little to no  c. sometimes; significant  d. sometimes; little to no  e. always; significant
 c. Yucca plants of the yucca–yucca moth system
Which of the following species has been documented as imposing penalties on individuals of its mutualistic partner that are engaged in overexploitation?  a. Figs of the fig–fig wasp system  b. Fig wasps of the fig–fig wasp system  c. Yucca plants of the yucca–yucca moth system  d. Yucca moths of the yucca–yucca moth system  e. None of the above
 d. Both a and b
In its mutualistic interactions with leaf-cutter ants, a bacterium produces fungicides against a fungal pathogen and receives, as a benefit,  a. a place to live.  b. food from glandular secretions.  c. defense against phages.  d. Both a and b  e. Both b and c
 b. increase at first and then level off as the number of fungal species was increased.In the study by van der Heijden and colleagues of mycorrhizal fungi, the root biomass of the target plants was found to  a. increase steadily as the number of fungal species was increased.  b. increase at first and then level off as the number of fungal species was increased.  c. be highest when the fungal species were at an intermediate level.  d. be high when there were only a few fungal species present and then to decrease as more were added.  e. be largely constant, regardless of the number of fungal species present.
 e. Both a and cA wasp pollinating a plant in exchange for food is an example of a _______ mutualism.  a. service  b. habitat  c. trophic  d. Both a and b  e. Both a and c
 a. For an ecological interaction to be a mutualism, the net benefits must exceed the net costs for one partner but not the other.Which of the following statements about mutualisms is false?  a. For an ecological interaction to be a mutualism, the net benefits must exceed the net costs for one partner but not the other.  b. Species do not engage in mutualisms for altruistic reasons.  c. In some mutualisms, one or the other partner, under certain environmental conditions, will withdraw the reward it usually provides.  d. There is an inherent conflict of interest between the partners in a mutualism.  e. All of the above are true; none is false.
 e. a decrease; a decreaseIn Grutter’s studies in the Great Barrier Reef of Australia, removal of the cleaner fish led to _______ in the number of fish species and _______ in the number of individual fish.  a. an increase; an increase  b. an increase; a decrease  c. little change; a decrease  d. a decrease; little change  e. a decrease; a decrease
 e. It is a mutualism.From the act of pollinating flowers, a wasp population gains the benefit of a 0.08 growth rate increase per month. However, the costs imposed by the flower (wasps getting stuck, time spent pollinating the flower instead of pollinating other species, etc.) is a 0.03 reduction in growth rate per month. The flower gains benefits from the pollination that enhance its population growth rate by 0.09 per month, but it incurs costs (feeding the wasps, damage done by the bees) that reduce its growth rate by 0.06 per month. Which of the following statements best describes the relationship between the bees and the flowers?  a. It is a host–parasite relationship in which the bees are the hosts and the flowers are the parasites.  b. It is a host–parasite relationship in which the flowers are the hosts and the bees are the parasites.  c. It is an amensalism.  d. It is a commensalism.  e. It is a mutualism.
 d. hurt; helpedAn international group of scientists found that neighboring plant species generally _______ the target species at low-elevation sites and _______ the target species at high-elevation sites.  a. helped; helped  b. helped; hurt  c. had no detectable effect on; hurt  d. hurt; helped  e. hurt; hurt
 d. Both a and bIn Janzen’s study in which ants were removed from acacia plants, plants with ant colonies were found to _______ than plants without ants.  a. weigh more  b. survive more successfully  c. be attacked more severely by insect herbivores  d. Both a and b  e. Both a and c
 zero population growth isoclines
Lines derived from the Lotka–Volterra competition model marking the conditions under which a population does not increase or decrease in size.
 resource
A feature of the environment that is required for growth, survival, or reproduction and which can be consumed or otherwise used to the point of depletion
 resource partitioning
The use of limiting resources by different species in a community in different ways.
 physical factor
A feature of the environment that affects organism function and population growth rates but is not consumed or depleted
 Lotka–Volterra competition model
A modified form of the logistic equation used to model competition.
 interference competition
An interaction in which species compete directly by performing antagonistic actions that interfere with the ability of their competitors to use a resource that both require, such as food or space
 exploitation competition
An interaction in which species compete indirectly through their mutual effects on the availability of a shared resource.
 competitive exclusion principle
The principle that two species that use a limiting resource in the same way cannot coexist indefinitely.
 competition
An interaction between individuals of two species in which each is harmed by their shared use of a resource that limits their ability to grow, survive, or reproduce (a –/– relationship).
 competition coefficient
A constant used in the Lotka–Volterra competition model to describe the extent to which an individual of one competing species decreases the per capita growth rate of the other species.
 character displacement
A process in which competition causes the phenotypes of competing species to evolve to become more different over time, thereby causing the species to become more different where they live together than where they live apart.
 compensation
An adaptive growth response of plants to herbivory in which removal of plant tissues stimulates the plant to produce new tissues.
 crypsis
A defense against predators in which prey species have a shape or coloration that provides camouflage and allows them to avoid detection.
 exploitation
A relationship in which one organism benefits by feeding on, and thus directly harming, another.
 induced defense
In plant–herbivore interactions, a defense against herbivory, such as production of a secondary compound, that is stimulated by herbivore attack.
 mimicry
A defense against predators in which prey species resemble less palatable organisms or physical features of their environment, causing potential predators to mistake them for something less desirable to eat.
 parasitoid
An insect that lays one or a few eggs on or in a host organism (itself usually an insect), which the resulting larvae remain with, eat, and almost always kill.
 secondary compound
A chemical compound in plants not used directly in growth, and often used in such functions as defense against herbivores or protection from harmful radiation.
 coevolution
The evolution of two interacting species, each in response to selection pressure imposed by the other.
 gene-for-gene interaction
A specific defensive response that makes particular plant genotypes resistant to particular parasite genotypes.
 threshold density
The minimum number of individuals susceptible to a disease that must be present in a population for the disease to become established and spread.
 arbuscular mycorrhizae
Mycorrhizae in which the fungal partner grows into the soil, extending some distance away from the plant root, and also grows between some root cells while penetrating others.
 ectomycorrhizae
Mycorrhizae in which the fungal partner typically grows between plant root cells and forms a mantle around the exterior of the root
 commensalisms
An interaction between two species in which individuals of one species benefit while individuals of the other species do not benefit and are not harmed.
 mycorrhizae
Symbiotic associations between plant roots and various types of fungi that are usually mutualistic.
 positive interactions
Interactions between species in which one or both species benefit and neither is harmed.
 trophic mutualism
A mutualism in which one or both of the mutualists receives energy or nutrients from its partner.
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