Deck 23: Ecological Communities

Question 1

Human cells contain mitochondria,which are responsible for processing the energy needed by our cells.Remember that the ancestors of mitochondria may once have been free-living prokaryotes.If mitochondria were still considered separate organisms within human cells,which of the following would best describe the relationship with them?

A) parasitic
B) mutualistic
C) competitive
D) pathogenic

Answer 1

B

Question 2

As the following figure illustrates,communities vary tremendously in size from as large as an entire forest to the digestive system of a single deer. How do biologists recognize communities?

A) Large communities are often defined by the distribution of their members, but small communities are often simply defined according to what is convenient at a given point in time.
B) Communities can be nested within a larger one; for example, the deer is part of the woodland, which is part of the forest.
C) Communities are recognized by the minimal species composition criterion: all communities must have eight or more species.
D) Communities have dynamic characteristics similar to those of populations; they consist of the habitat and species critical to the community growth rate.

Answer 2

A

Question 3

Which of the following best illustrates behavioral mutualism?

A) Fruit seeds pass through a consumer's digestive system and are moved to a location distant from the parent plant.
B) Pollen from one plant is carried to another.
C) Small fish called cleaner wrasse remove parasites from the mouth and gills of predatory fish.
D) Infected individuals experience diarrhea that releases infectious organisms into the environment.

Answer 3

C

Question 4

If researchers were to document that the diversity of anemones lacking resident clownfish was approximately equal to those with clownfish,it would suggest that the interaction between these two species was

A) behavioral mutualism.
B) symbiotic.
C) commensalistic.
D) exploitative.

Question 5

Which of the following combinations of symbols represents an interaction in which one species benefits and the other is exploited?

A) +/-
B) +/+
C) o/+
D) -/-

Question 6

Do humans exhibit any mutualistic relationships?

A) No; humans can only develop parasitic relationships with other organisms.
B) Yes; humans host disease pathogens that limit population growth and overcrowding.
C) Yes; in the absence of technology, humans quickly become prey for other predators.
D) Yes; humans host beneficial bacteria within our digestive systems.

Question 7

Clownfish have evolved to live safely between the stinging tentacles of certain sea anemones.The fish receives protection from predators,whereas the anemone receives some food from the fish.This relationship is an example of

A) nutritional mutualism.
B) consumer interaction.
C) competitive limitation.
D) behavioral mutualism.

Question 8

Every healthy human digestive system is home to countless microorganisms.In a normal digestive system,what type of relationship would you say this is?

A) parasitic
B) mutualistic
C) competitive
D) pathological

Question 9

Antibiotic therapy sometimes reduces the population of gut-inhabiting microorganisms.Bloating and diarrhea often follow until the populations reestablish themselves.This observation suggests that these microorganisms participate in a(n)________ relationship with humans.

A) competitive
B) exploitative
C) mutualistic
D) pathogenic

Question 10

In seed-dispersal mutualism,plants produce ________ to entice consumers to disperse the plant's seeds.

A) attractive aromas
B) fleshy fruits
C) edible pollen
D) nectar

Question 11

An animal eats fruit from a plant and later deposits seed in its feces far from the plant.This is an example of a

A) pollinator mutualism.
B) gut inhabitant mutualism.
C) behavioral mutualism.
D) seed dispersal mutualism.

Question 12

Some algae and fungi live in associations known as lichens,which allow both to survive in a harsher environment than either could normally live in alone.This association is an example of

A) parasitism.
B) mutualism.
C) consumerism.
D) competition.

Question 13

In comparing Communities A and B below,the major difference between them is that they differ in

A) species richness.
B) relative species abundance.
C) that Community A has more primary producers than does Community B.
D) that Community B has more primary producers than does Community A.

Question 14

Which of the following animals would be most likely to simultaneously participate in seed dispersal and a gut inhabitant mutualism?

A) wolves
B) rattlesnakes
C) scorpions
D) deer

Question 15

Can a human being be considered an ecological community?

A) Yes; for example, a community of microorganisms lives within the human digestive system.
B) Yes; human beings live with other humans, own pets, and grow domesticated crops.
C) No; a community is formed from many populations, and it takes more than one individual to make up a population.
D) No; human populations are artificial rather than natural and are considered to fall outside of ecology.

Question 16

In the pollinator mutualism between the yucca plant and the yucca moth,the yucca plant is able to abort the seeds in any given flower if the moth lays too many eggs in that flower.What is the advantage the yucca plant gains by aborting these seeds?

A) The yucca plant is responsible for keeping the yucca moth population at a reasonable size.
B) Seeds are energetically expensive to produce, and if the moth larvae are going to eat most of the seeds in one fruit, the plant is able to save energy by aborting those seeds.
C) The carrying capacity of the yucca moth is increased every time it lays an egg in a yucca plant's flower, so the fewer seeds that are produced by the plant, the higher the carrying capacity of the moth can be.
D) The carrying capacity of the yucca moth is reduced every time it lays an egg in a yucca plant's flower, so the fewer seeds that are produced by the plant, the higher the carrying capacity of the moth can be.

Question 17

Relationships between different species often involve energy or lifestyle compromises.What best describes the compromises,if any,seen in mutualism?

A) no compromises to either organism
B) fatal to at least one of the organisms
C) a compromise (for example, dietary restriction) to one organism but not the other
D) slight compromises (for example, habitat restriction) to both organisms

Question 18

Which of the following patterns represents the outcomes of a mutualistic relationship?

A) +/-
B) +/+
C) o/+
D) -/-

Question 19

The relationship between house pets and people would be best described as

A) parasitic.
B) mutualistic.
C) predatorial.
D) competitive.

Question 20

Which of the following statements about communities is true?

A) They usually have few species of organisms.
B) There can be complex interactions between the organisms that make up a community.
C) They are more abundant in temperate areas.
D) They are made up of mammal species only.

Question 21

Cowbirds lay their eggs in the nests of smaller birds.The fast-developing cowbird chicks hatch first,and push the other baby chicks out of the nest as they hatch.Which interaction best describes cowbird behavior?

A) mutualism
B) parasitism
C) predation
D) exploitative competition

Question 22

Which of the following is most likely to be an example of an induced response?

A) bright colors on the wings of a toxic butterfly
B) spines on a cactus habitually exposed to grazing
C) brightly colored flowers on a rosebush
D) color patterns on a poisonous snake

Question 23

Flies belonging to the family Phoridae inject their eggs into fire ants.The larva that subsequently hatches feeds on the ant until it pupates.The larva would be best described as a

A) parasite.
B) gut mutualist.
C) predator.
D) pathogen.

Question 24

Which of the following patterns represents the outcomes of a commensalistic relationship?

A) +/-
B) +/+
C) o/+
D) -/-

Question 25

Which of the following patterns represents a competitive interaction?

A) +/-
B) +/+
C) o/+
D) -/-

Question 26

The release of a parasitic wasp in California helped control the infestation of scale insects on citrus trees.However,it also caused the near extinction of a different species of parasitic wasp.Should we consider this experiment an unqualified success?

A) Yes; the scale insects are controlled, and the extinct wasp was not ecologically important.
B) Yes; as long as we get a result that helps humans, it does not matter what the effect is on other species.
C) No; the effect of the loss of the original species of wasp cannot be predicted and may be more significant than the benefits to the citrus tree crop.
D) No; the citrus tree population in California will now be able to rise to unmanageable numbers.

Question 27

In the centers of their ranges,two species of hummingbirds have very similar tongue lengths,but where the ranges overlap,one species has a shorter tongue and the other a longer tongue.This would most likely be an example of

A) seed-dispersal mutualism.
B) parasitism.
C) character displacement.
D) a predator-prey interaction.

Question 28

Which of the following patterns represents the outcome of a parasitic relationship?

A) +/-
B) +/+
C) o/+
D) -/-

Question 29

What statement summarizes the outcomes of a parasitic relationship?

A) Both the parasite and the host benefit.
B) Only the parasite benefits; the host is harmed.
C) Only the host benefits; the parasite is harmed.
D) Both the parasite and the host are harmed.

Question 30

By growing on the trunk or branch of a tree,a lichen gains height and exposure to sunlight for photosynthesis.The tree is not harmed by the lichen but does not benefit either.The relationship between the lichen and the tree is

A) commensalism.
B) mutualism.
C) parasitism.
D) interference competition.

Question 31

Which of the following statements is FALSE?

A) The level of predation can be so intense that the prey can be driven to extinction.
B) Predation can stimulate the reproductive capacity of a prey species and can cause the abundance of that prey to increase.
C) The selective pressure caused by predation can alter the behavior of its prey.
D) The distribution of a predatory species can restrict the distribution of its prey.

Question 32

Some species of warblers partition their niche by foraging in different parts of the same tree,although all birds eat the same species of insects and spiders.What mechanism has natural selection used to produce this interaction?

A) character displacement
B) behavioral modification
C) directional selection
D) competitive exclusion

Question 33

When two similar species inhabit the same area,they may evolve over time to become more different and

A) drive the other species to extinction.
B) reduce direct competition.
C) use up the other species' resources.
D) reduce their genetic variation.

Question 34

Parasites,and the disease they cause,represent a distinctive type of exploitation because

A) of the high mortality rates associated with infection.
B) parasites affect only specific portions of the host.
C) of the chronic and progressive debilitation of the host.
D) parasites represent the only species interaction where the symbiont lives on or in the host organism.

Question 35

A praying mantis captures and devours many insects during its lifetime; the relationship between a mantis and the exploited species (for example,a grasshopper)is one of

A) parasite/host.
B) pathogen/prey.
C) parasite/prey.
D) predator/prey.

Question 36

Female ducks frequently deposit fertile eggs in the nests of unattended neighboring ducks.These eggs hatch and are then reared by the foster parent.What term best describes this behavior?

A) parasitism
B) behavioral mutualism
C) exploitative competition
D) nest mutualism

Question 37

In ________ competition,species compete indirectly for a shared resource,each reducing the amount available to the other competitor.

A) exploitative
B) restrictive
C) interference
D) advantageous

Question 38

Herbivores interact exploitatively with the plants they consume; do they simultaneously participate in any other relationships within their communities?

A) Yes: an herbivore will have mutualistic relationships with intestinal bacteria and an exploitative relationship with its predators.
B) No: community relationships always have costs, so reducing them increases an organism's fitness.
C) No: only a single type of interaction can occur at a time, although herbivores can participate in several exploitative relationships at once.
D) Yes: each of the plant species eaten needs to be considered a separate interaction.

Question 39

Which of the following statements about competition is FALSE?

A) It can limit the distribution of a species.
B) It can limit the abundance of a species.
C) It can increase the differences between species.
D) It can make two species become more alike.

Question 40

Examine the following graph; what best describes the cycling that each population experiences?

A) Lynx populations decrease in size when hare populations increase in size; hares are the superior competitors.
B) Lynx populations increase in size when hare populations decrease in size; lynx are the superior competitors.
C) Lynx populations decrease in size when hare populations decrease in size; lynx are exploiting the hare population.
D) The increase and decrease of each species is driven by oscillating density-independent factors, but since they share the same habitat, the cycles coincide.

Question 41

Once a mature community develops,is it likely to remain that way indefinitely?

A) No; over long-term time scales, climate change will probably occur, causing the community to eventually change.
B) No; once a climax community develops, the lack of biotic variability eventually degrades the habitat.
C) Yes; once a climax community develops, it will always remain undisturbed.
D) Yes; climax communities become so stable that they prevent disturbances from occurring.

Question 42

The removal of a keystone species from a community usually results in

A) the death of all other community members.
B) the disappearance of that community.
C) substantial changes in the abundance of many species.
D) minor changes, if any.

Question 43

The process that establishes new communities and restores disturbed communities is termed

A) secondary growth.
B) eutrophication.
C) diversification.
D) succession.

Question 44

As shown in the following graph,selected intertidal communities along the Washington coast changed when the sea star Pisaster ochraceus was removed.After 10 years,how did those communities compare to control communities?

A) The communities were statistically indistinguishable from one another.
B) Without sea stars, the total number of species declined.
C) Other predatory sea stars replaced Pisaster.
D) Some populations declined, but species diversity was unaffected.

Question 45

During ________,a newly created habitat is inhabited.

A) primary succession
B) climax community formation
C) disturbance colonization
D) keystone recovery

Question 46

Cattle grazing has a surprisingly harmful affect on dry grassland of the southwestern United States.What aspect of grazing is most likely responsible?

A) Cattle are seed-dispersal mutualists; they gather shrub seeds while grazing and then deposit them in a concentrated area when they defecate.
B) Cattle compress the soil; the small amount of rainfall runs off the surface rather than penetrating, and the deep-rooted grasses are replaced by shallow-rooted shrubs.
C) Cattle droppings are toxic to the grasses that cattle prefer; eventually, the buildup of toxins permits only toxin-resistant shrubs to grow.
D) Grazing exposes the native plants to sunlight, which initially stunts and eventually inhibits their growth.

Question 47

The living corals in tropical reefs have a profound affect on the hundreds of species that live in association with the reef and one another,yet corals are not considered keystone species because

A) they are too abundant; keystone species always have a numerically low abundance.
B) they consume more energy as plankton than their photosynthetic components produce.
C) their affects are not dependent on the presence of living individuals; the reefs they build persist long after their death.
D) their total benefit is solely related to providing protection from predators for the small species that live there.

Question 48

Communities change with respect to several timescales; an example of long-term change would be the

A) annual variability in population size.
B) presence or absence of a migrant species.
C) species composition of the community.
D) decline in prey abundance during a harsh winter.

Question 49

The following figure illustrates how,although pines first established themselves as the dominant tree in the Lake Michigan sand dune community,black oaks ultimately became the dominant species. What best explains the gradual reduction of the pine?

A) Oaks trap sand, causing the dune to level out; pines can only survive in the low, protected areas between the dunes.
B) Pine needles and the shade from existing pines improve the soil composition and moisture, allowing oaks to become established and preventing new pines from surviving.
C) Pines replace the grasses, but this destabilizes the dune and increases the amount of moving sand; the loss of pines is not related to the presence of the oaks.
D) Actually, oak seeds were always present in the sand; they simply require more time to germinate.

Question 50

In which of the following situations would secondary rather than primary succession be most likely to occur?

A) on an island that has just risen out of the ocean
B) on bare ground exposed by the retreat of a glacier
C) on the surface of recently cooled lava
D) in a forest that had burned to bare ground

Question 51

Coevolution often occurs when natural selection produces evolutionary change in predator and prey populations; a good example is

A) the mottled and spotted coloration of newborn fawns.
B) the speed capacities of the cheetah and Thompson's gazelle.
C) the migration of the monarch butterfly to Mexico during the winter.
D) the colonization of the snout of the gray whale by several species of barnacles.

Question 52

Pisaster ochraceus,the common Pacific Northwest sea star,is contending with an apparently new disease termed sea star wasting syndrome,which threatens this species with possible extinction.What community changes can be expected if the sea star population is reduced to low levels or disappears entirely?

A) The various sea star predators, such as the California mussel, will experience population declines proportional to the loss of prey; eventually, the diversity of the community will decline.
B) Other mussel predators, currently suppressed by exploitation competition, will increase; the diversity of the community will remain about the same.
C) Algae and other photosynthesizers will use the vacant space left by the sea stars and increase the food resources; the diversity of the community will increase.
D) Mussels will increase and compete with other community members for space; eventually, the diversity of the community will decline.

Question 53

Which example best illustrates interference competition?

A) Soil levels of potassium are gradually reduced by the hemlocks and cedars in a climax forest.
B) The growth of starling populations usually coincides with declines in songbirds because both use abandoned cavities for nesting.
C) When larger animals become scarce, wolves often prey on mice, reducing their availability to coyotes.
D) Rough-skinned newts contain enough toxin in their skin glands to kill almost any predator.

Question 54

Which of the following can occur when the climate of an area changes?

A) Natural selection usually causes the community to adapt and survive the change with little visible effect.
B) That area becomes uninhabitable to all species and is abandoned.
C) That community may relocate to an area with a climate similar to that of the original location.
D) Continental drift restores communities to climates similar to those from which the communities came.

Question 55

As the following figure illustrates,the distribution of numerous intertidal organisms is restricted to bands or zones.The upper limit to the zone is determined by tolerance to physical factors such as desiccation,whereas the lower boundary is determined by a biological interaction such as competition. What could account for the lower limit for Semibalanus?

A) competition from adult Chthamalus living in deeper water
B) the force of the waves on the lower portions of the rock
C) predation from less tolerant predators such as sea stars
D) overheating during low tide exposure

Question 56

Certain species of squirrels and acorn woodpeckers both eat acorns.In forests without squirrels,the density of acorn woodpeckers averages 100 per square kilometer,whereas in forests with squirrels,the density of acorn woodpeckers is roughly halved.This reduced density most probably results from

A) interference competition.
B) herbivory.
C) character displacement.
D) exploitative competition.

Question 57

These shorebirds illustrate niche partitioning; each species has a specialized bill that permits it to feed in ways that reduce competition with other shorebirds living in the community.How might a biologist explain niche partitioning?

A) Birds with compatible adaptations eventually find one another and establish mature communities.
B) By sharing a resource, each species is less abundant than if it were alone; natural selection will eventually produce a shorebird that can exploit the entire food resource.
C) These birds are coevolving; the adaptations each displays represent the response to directional selection pressure created by their competitors.
D) Highly diverse communities are more stable than those with low diversity; given enough time, the evolution of adaptations that reduce competition would be expected.

Question 58

Which of the following experiments would help to identify a keystone species?

A) introduce more of the suspected species into the area and observe the effects on other community members
B) remove the suspected species from the area and observe the effects on other community members
C) introduce an invasive species related to the suspected species into the area and observe the effects on the suspected species
D) introduce additional individuals of the suspected species' food source into the area and observe the effects on community members

Question 59

The activity of predators has caused their prey to evolve a variety of protective characteristics.How were the prey able to acquire these new features?

A) The prey selectively bred to increase the frequency of protective traits in their population.
B) The prey underwent a population explosion that allowed them to outnumber their predators and thus develop new protective features.
C) The prey organisms mated with other species to acquire new protective traits.
D) Natural selection acted on genetic variability already present in the prey population.

Question 60

Which of the following choices best explains,from an ecological perspective,why there are laws that require a wildlife survey before certain building or other land-use projects may proceed?

A) If a keystone species is found, it can be moved to another area where it will establish a new community of organisms.
B) If the only local habitat for a keystone species is disturbed, the entire community of populations will be affected.
C) If the species are surveyed before the land is used, they will all be more likely to survive the building project.
D) If the species are surveyed before the land is used, they will all be more easily distributed to other habitats.

Question 61

The observation that some organisms live in herds or flocks in order to protect themselves from predation illustrates that natural selection can produce adaptations that modify an organism's morphology,metabolism,or ________.

Question 62

Mistletoe is clearly a parasitic organism,living off the resources of the trees it infects.However,the leaves it drops contain nutrients that nourish the many insects on the forest floor.What interaction describes this later relationship?

A) Commensalism: the insects are feeding on abandoned leaves; they benefit while the plant is unaffected.
B) Exploitation: like any other herbivore-plant interaction, the insects are consuming mistletoe tissue for their energy and nutrients.
C) Mutualism: mistletoe intentionally feeds the insects so that the tree is left for the mistletoe to exclusively exploit.
D) Competition: mistletoe engages in interference competition with the herbivorous insects that live in the forest.

Question 63

Due to competition,forms of competing species may evolve to become more different from each other over time.This change is known as character ________.

Question 64

Milkweed is a mildly toxic plant unless it has been grazed,in which case the toxin concentration greatly increases; this change,stimulated by an attack from herbivores,is an example of a(n)________ response.

Question 65

Islands such as the Hawaiian Islands are particularly vulnerable to introduced species because

A) the species on islands have not evolved with the invasive species and are easily outcompeted by them.
B) the species on islands have evolved defense mechanisms for invasive insects but not invasive plants.
C) predators native to the islands cannot digest invasive species.
D) selective breeding of the native plants and animals by humans has bred out all of their natural defenses.

Question 66

The original colonizing organisms in Hawaii came from other localities but currently show relatively little resemblance to these ancestors; why are the organisms that now live on Hawaii so different?

A) Hawaii is a relatively young landmass, so evolution continues there, although it has ceased in most other places on Earth.
B) The organisms that live on Hawaii do not have predators, which allows them to evolve into a greater variety of life forms.
C) Through time, random evolutionary change led to speciation and produced the unique Hawaiian organisms observed today.
D) Community interactions are the most influential force in the evolution of organisms; the communities on Hawaii were different from those of the initial colonists.

Question 67

Competition is an unavoidable consequence when two species whose ________ overlaps live in the same community.

Question 68

Human-caused changes in ecological communities can be considered unique because

A) humans have control over the actions that might cause the changes.
B) human-caused changes are always more severe than natural changes.
C) human-caused changes almost always benefit the existing community.
D) human-caused changes almost always modify the regional climate.

Question 69

Exploitation occurs in many forms; those interactions that result in the immediate death and consumption of the prey are classified as ________.

Question 70

A community often contains a species that never becomes dominant in terms of its density but,nevertheless,exerts a profound influence on the organization and dynamics of that community; these community members are known as ________ species.

Question 71

Follicle mites live in the hair follicles of human skin.They feed on single cells but do little if any harm to the human; the mite has a stable place to live and reproduce.This is an example of ________.

Question 72

The association of populations of different species that live in the same area is a(n)________ .

Question 73

An organism that transfers one plant's male reproductive cells to the female reproductive organs of another plant is a(n)________.

Question 74

When different species of birds compete to use an abandoned woodpecker cavity,the successful competitor directly prevents the use of that resource by all others.This is an example of ________ competition.

Question 75

The number of different species that live in the community and the relative abundances of those species are the two components that characterize the community's ________.

Question 76

If a bird eats a monarch butterfly,the bird will vomit.Monarchs are brightly colored.This example demonstrates ________ coloration.

Question 77

Which of the following statements about human-caused disturbances to communities is true?

A) Human-caused disturbances are not important because they do not cause any long-term permanent changes.
B) When a community recovers from a human-caused disturbance, it returns to its pre-disturbance condition.
C) Some communities can recover from human-caused disturbances over a period of time.
D) All communities are able to recover from human-caused disturbances.

Question 78

The interactions that occur between species can be categorized on the basis of the outcomes the interaction produces; when both species benefit,the interaction is ________.

Question 79

The bacteria in yogurt can colonize the human intestine and participate in a symbiotic relationship called ________.

Question 80

Anthropogenic,or human-caused,changes to ecological communities typically

A) improve those habitats for other organisms.
B) cause long-term damage and reduce the complexity of existing communities.
C) do not influence the natural interactions between organisms.
D) generally increase the diversity of life on Earth.