Deck 56: Communities

Question 1

Wetland A has four species of frogs, present in the following numbers of individuals: 10, 10, 10, and 2.Wetland B has five species of frogs, present in the following numbers: 10, 10, 10, 10, and 10.What can be said about frog species richness and species evenness in the two wetlands?

A) Species richness and species evenness are the same in the two wetlands.
B) Species richness and species evenness are both higher in wetland A.
C) Species richness and species evenness are both higher in wetland B.
D) Species richness is higher in wetland A; species evenness is higher in wetland B.
E) Species richness is higher in wetland B; species evenness is higher in wetland A.

Answer 1

C

Question 2

What is the major distinction, if any, between a food web and an interaction web?

A) There is no distinction; they are the same thing.
B) A food web shows only trophic interactions; an interaction web shows both trophic and nontrophic interactions.
C) A food web shows only trophic interactions; an interaction web shows only nontrophic interactions.
D) A food web simply illustrates energy interactions; an interaction web also gives quantitative measurements of these interactions.
E) It is relatively easy to map all interactions in a food web; it is almost impossible to map all interactions in an interaction web.

Answer 2

B

Question 3

A community ecologist defined a rotting log in a forest as a community, and she set up a series of observations and experiments to study it.When defining this community, the researcher most likely considered all of the following aspects except that the log had a

A) relatively distinct boundary.
B) specific number of species known in advance.
C) relatively distinct set of interacting species.
D) relatively self-contained food web.
E) size and location that could be easily studied.

Answer 3

B

Question 4

Which of these organisms is a primary producer?

A) Oak tree
B) Earthworm
C) Spider
D) Human
E) Fungus

Question 5

Ecologists sometimes have difficulty defining and separating communities in nature because most communities have

A) similar sizes and shapes.
B) the same types of interactions.
C) very large geographic areas.
D) uncertain boundaries.
E) approximately the same number of species.

Question 6

If secondary consumers are the highest trophic level in a specific community, how many trophic levels are in this community (not counting decomposers or omnivores)?

A) Two
B) Three
C) Four
D) That cannot be determined from this information
E) Three in terrestrial communities, four in aquatic communities

Question 7

As a community develops, more species enter the community and become established.How will this affect the Shannon index (H) of the community?

A) It will have little or no effect.
B) The value of H will increase.
C) The value of H will decrease.
D) The value of H will increase only if the entering species are rare.
E) The value of H will increase only if the entering species are common.

Question 8

Lawn A was planted with a single species of grass, which covers 90 percent of the lawn.The other plant species there include five species of weeds, each covering 2 percent of the lawn.Lawn B has the same six species, but with percentages of 75 percent grass and 5 percent for each of the five weeds.How do species richness and species evenness of the two lawns compare?

A) The two lawns have equal species richness and species evenness.
B) The lawns have equal species richness, but lawn A has greater species evenness.
C) The lawns have equal species richness, but lawn B has greater species evenness.
D) The lawns have equal species evenness, but lawn A has greater species richness.
E) The lawns have equal species evenness, but lawn B has greater species richness.

Question 9

A community ecologist is studying all the pollinators in a prairie community.This researcher has chosen to subdivide the community on the basis of

A) guilds.
B) taxonomic groups.
C) functional groups.
D) keystone species.
E) foundation species.

Question 10

The turkey vulture, which feeds on relatively large dead animals, is considered a scavenger rather than a detritivore.What is the distinction?

A) Detritivores feed on living, rather than dead, material.
B) Detritivores feed on the waste products and dead bodies of small organisms rather than larger dead organisms.
C) Detritivores feed only on plant material, scavengers only on animal material.
D) Detritivores break down material in aquatic ecosystems, scavengers in terrestrial ecosystems.
E) Detritivores do not return nutrients to the ecosystem; scavengers do return nutrients.

Question 11

Robins eat earthworms, but they also eat a variety of insects and berries.In a food web, the robin would be considered a(n)

A) producer.
B) herbivore.
C) carnivore.
D) omnivore.
E) detritivore.

Question 12

Which concept would a community ecologist be most likely to study?

A) Energy flow through an ecosystem
B) Population growth of a single species
C) Interactions among individuals of the same species living together in an area
D) Interactions among individuals of different species living together in an area
E) The cycling of matter through biotic and abiotic components of an area

Question 13

Refer to the diagram. In this simplified food web, the gray wolf is classified under "secondary and tertiary consumers." The wolf is a secondary consumer because it feeds on _______ and a tertiary consumer because it feeds on _______.

A) bison; coyote
B) bison; elk
C) coyote; bison
D) coyote; elk
E) elk; grizzly bear

Question 14

Refer to the table. A community contains four species of birds in the following numbers of individuals: 30, 10, 5, 5.The table gives most of the information required to determine the Shannon index of diversity.Complete the table by choosing the correct values: The proportion for species B is _______; the total value for p_i ln(p_i)is _______.

A) 0.60; -0.23
B) 0.10; -0.46
C) 0.20; -0.78
D) 0.20; -1.09
E) 0.30; -1.09

Question 15

The Shannon index of species diversity is calculated using this equation: The data for a community of four species is given in the table.Use the table and the equation to determine the diversity value (H) for this community.

A) H = 4
B) H = 50
C) H = 1.00
D) H = -1.09
E) H = 1.09

Question 16

Refer to the figure, showing the soil food web. Based on this food web, which organisms are members of the detritivore/decomposer level of the web?

A) Bacteria only
B) Bacteria and protozoa only
C) Bacteria and fungi only
D) Bacteria, fungi, and nematodes
E) Bacteria, protozoa, and nematodes

Question 17

When Mount St.Helens erupted, three relatively distinct zones of destruction resulted: the Pumice Plain, which was essentially sterilized and had no remaining life; the Blowdown Zone on the mountain slopes, where downed trees and vegetation were covered with mud and ash; and farther down, forests that remained standing but were also covered with mud and ash.Based on these levels of destruction, what would the likely rate of recovery be for these zones?

A) All would recover quickly, at relatively equal rates.
B) None would recover; the heat, mud, and ash would prevent regrowth.
C) The Pumice Plain would recover fastest, followed by the Blowdown Zone and then the lower forests.
D) The lower forests would recover fastest, followed by the Blowdown Zone and then the Pumice Plain.
E) The Blowdown Zone and lower forests would recover relatively quickly; the Pumice Plain would never recover.

Question 18

Which phrase best describes an ecological community, based on the theoretical definition?

A) All field mice in a local grassland
B) All animals in a local grassland
C) All living organisms in a local grassland
D) All living organisms in all grasslands
E) All living organisms and all abiotic factors in a local grassland

Question 19

In the ocean, phytoplankton are tiny floating algae and similar organisms, comprising many species, that carry out photosynthesis.Based on these characteristics, a community ecologist would most likely place all ocean phytoplankton into which subset of a community?

A) Population
B) Taxonomic group
C) Food (trophic) web
D) Functional group
E) Interaction web

Question 20

An ecologist might subdivide a community on the basis of any of the following factors except

A) its guilds.
B) its number of species.
C) trophic levels in its food web.
D) its taxonomic groups.
E) its functional groups.

Question 21

Which of these is not an environmental factor that might prevent a species of mollusk from becoming established in a shallow-water marine community?

A) The water temperature is above the range generally tolerated by the species.
B) The location is far from a freshwater outlet, and the species prefers low salinity.
C) Several other mollusk species live in the same community and are strong competitors.
D) Ocean pH has been gradually increasing, and the species is very sensitive to pH.
E) The waves are very choppy, and the species reproduces better in calm conditions.

Question 22

A farmer decides to let a field that has been under cultivation revert back to natural prairie.The field is surrounded by other agricultural crop fields.The developing prairie may receive input of species from all of the following sources except

A) seeds carried in on animal fur.
B) seeds brought in by birds from the area.
C) seeds brought in by wind and rain.
D) species living outside the regional species pool.
E) small mammals moving in from nearby fields or edges.

Question 23

The ability of species to disperse to a community is determined by which of the "filters" that help determine community membership?

A) The biotic filter, or species interactions
B) The abiotic filter, or environmental conditions
C) The species supply filter
D) Both the biotic and abiotic filters
E) Both the biotic filter and the species supply filter

Question 24

Two communities are analyzed using the Shannon index of species diversity.Community A has an H value of 1.5.Community B has an H value of 3.0.What is the strongest conclusion that can be drawn about the species diversity of these two communities?

A) The two communities have very similar species diversities.
B) Community A has a lower species diversity than community B.
C) Community A has a higher species diversity than community B.
D) Community A has both higher species richness and higher species evenness than community B.
E) Community A has higher species richness, and community B has higher species evenness.

Question 25

The European green crab has become invasive in many places, including the Pacific Northwest.It is both carried in ships' ballast water and sold as fish bait.It becomes established during warm-water conditions like those that occur during El Niño years.The crab preys on many types of nearshore organisms, and its voracious appetite negatively affects the commercial shellfish industry.This information suggests that which factors enable the European green crab to become established?

A) Favorable environmental conditions and efficient predation
B) Favorable environmental conditions and efficient dispersal
C) Efficient predation and efficient dispersal
D) Efficient dispersal and lack of contact with native species
E) Bypassing of usual abiotic filters and lack of contact with native species

Question 26

Managers sow seeds for a new non-native grass species in a field and allow the grass to become established.Later, they introduce cattle to graze there.The new grass becomes the cattle's favorite food, and the new species is grazed to extinction.This might be considered an example of which process at work?

A) Biotic resistance
B) Abiotic resistance
C) Species supply filter
D) Omnivory
E) Trophic cascade

Question 27

A scientist analyzes genetic differences in all the frog species in a pond.She also determines the total number of frog species in the community and calculates the Shannon diversity index.She is measuring which aspect(s) of biodiversity?

A) Genetic diversity only
B) Species diversity only
C) Genetic and species diversity only
D) Species and community diversity only
E) Genetic, species, and community diversity

Question 28

Kudzu originated in Asia and was introduced to the southern United States for uses including cattle fodder and erosion control.Kudzu grows extremely rapidly, obtains resources very quickly, and absorbs nitrogen from the air.Its rapid growth smothers plants, including whole trees, and covers buildings and other structures.These characteristics suggest that kudzu would have what effect on community structure?

A) It would probably have no noticeable effect.
B) It would increase community stability by increasing diversity.
C) It would increase community stability by increasing productivity.
D) It would decrease community stability by decreasing or eliminating native species.
E) It would decrease community stability by increasing diversity and productivity.

Question 29

Several members of a mouse species living in a weedy edge environment migrate into a nearby crop field.They find plenty of fallen seeds to eat, so they dig tunnels and begin to colonize.The soil often receives inputs of concentrated chemicals, including pesticides.The mice begin to die, and after a few generations the survivors move back into the edge environment.The mice have failed to colonize the new community because of

A) a biotic filter.
B) an abiotic filter.
C) inability to disperse.
D) lack of a suitable species pool.
E) lack of suitable nesting areas.

Question 30

A researcher wants to understand the fitness of a population of butterflies, in order to better understand its place in the community.The researcher would most likely carry out a study of the

A) butterfly's place in the food web.
B) species diversity of the community.
C) species diversity of surrounding communities.
D) genetic diversity of all members of the community.
E) genetic diversity of the butterfly population.

Question 31

A new community is forming in a region devastated by a years-long drought.Rain has recently returned to the area; in some cases, the rain has been severe enough to cause flooding and rapid runoff.Seeds from a number of plant species enter from the surrounding region and begin to grow.However, periodic storms erode the soil, and many species have difficulty becoming established.This series of events suggests that which factor is most important in determining membership in the new community?

A) Species supply
B) Environmental conditions
C) Interactions with resident species
D) Invasions by outside species
E) Lack of sufficient nutrients

Question 32

The establishment of a non-native species in a new community would most likely be considered unsuccessful if

A) no evidence of its invasion can be found.
B) it hybridizes with a native species, changing the gene pool.
C) it also invades adjacent areas.
D) it outcompetes and displaces native organisms.
E) it assimilates with no other visible change to the community

Question 33

The initial cause that is triggering the loss of polar bears, and the resulting change in Arctic communities, is

A) rising Arctic temperatures.
B) melting sea ice.
C) polar bear starvation.
D) loss of the polar bears' food source.
E) lack of adaptation by polar bears.

Question 34

If someone attempted to introduce a tropical species, such as an orangutan, into a polar region such as northern Alaska, it would probably not survive.What factor would likely be most effective in preventing its survival?

A) Lack of familiar species
B) An extremely good dispersal ability
C) An environment to which it was not adapted
D) Presence of too many similar species
E) Presence of too many predators

Question 35

Beginning about 500 million years ago, plants began to colonize land.One factor that made this colonization possible was the presence of an atmosphere with high concentrations of carbon dioxide, which was necessary for photosynthesis.This suggests that before colonization, the green aquatic algae that eventually evolved into plants were prevented from forming land communities by

A) competition from other plants.
B) competition from other aquatic algae.
C) lack of root systems.
D) lack of a strong species pool.
E) abiotic factors such as environmental gases.

Question 36

As global temperatures rise, warm seasons lengthen.Flowering dates for some flowers are now about 10 days earlier than in the recent past.For pollination to occur, pollinators depend on flowers to bloom at specific times.Pollinators also alter their seasons-for example, insects emerge earlier.But these alterations do not necessarily coincide with changes in flowering.What is the most likely near-term consequence of these mismatches in flowering and pollinator readiness?

A) Pollination will become unnecessary.
B) Animals other than insects will take over pollination.
C) Pollination will be less effective for some species.
D) Plants requiring pollination will go extinct.
E) Insects needed for pollination will go extinct.

Question 37

A community that has only one species would have a Shannon diversity index (H) of

A) 0.
B) 0.1.
C) 0.01.
D) 1.00.
E) -1.00.

Question 38

Biotic resistance will be effective as a control on invasive species in cases where the native species

A) are weak predators or competitors.
B) are strong predators or competitors.
C) can evade the invading species.
D) can commandeer all available resources.
E) are in different taxonomic groups than the invaders.

Question 39

A plant species is part of the regional species pool but fails to become established in a newly forming community.This failure to become established most likely occurs because

A) it is treated as an invasive species in the new community.
B) its seeds do not disperse well and never reach the new community.
C) it fixes nitrogen, which is not needed in the new community.
D) it carries out competitive coexistence in the new community.
E) it outcompetes most plants in the new community.

Question 40

The golden toad of Central America is thought to be extinct in the wild.The mountaintop cloud forests in which it lived no longer exist, because of drought and other changes associated with climate change.In this case, it appears that changing environmental conditions affected the habitat of the golden toad by

A) causing an extinction, but otherwise having minor effects.
B) causing minor changes as organisms moved from place to place.
C) improving the community by making its climate more tolerable.
D) causing a drought, to which most organisms should be able to adapt.
E) destroying the entire cloud forest community.

Question 41

Two fish species live and compete on a coral reef.Fish A is dominant and maintains a larger population than fish B.During a very hot summer, a temperature spike occurs on the reef, killing off most of fish A's population.The fish B population then begins to increase.This scenario describes the process of

A) resource-mediated coexistence.
B) trophic cascade.
C) indirect interaction.
D) competitive exclusion.
E) ecosystem engineering.

Question 42

Scientists reported that the reintroduction of wolves into Yellowstone National Park initiated a trophic cascade.Which factual statement best supports this conclusion?

A) Wolves prey on a number of species, but they prefer elk.
B) Mountain lions and coyotes, as well as wolves, prey on elk.
C) After wolves were reintroduced, the numbers of mountain lions remained constant.
D) After wolves were reintroduced, the numbers of aspen trees increased.
E) After wolves were reintroduced, the numbers of elk declined.

Question 43

In the northern Pacific Ocean, sea otters feed on sea urchins and sea stars.Sea urchins feed on kelp, and sea stars feed on mussels.Beginning in the 1700s, sea otters were hunted for their fur and driven nearly to extinction in some areas, resulting in trophic cascades in their communities.When the fur trade ended, sea otter numbers increased and their communities began to recover.One would expect this recovery to lead to increased numbers of _______ and decreased numbers of _______.

A) kelp and mussels; sea urchins and sea stars
B) sea urchins and kelp; sea stars and mussels
C) sea urchins and sea stars; kelp and mussels
D) sea stars and mussels; sea urchins and kelp
E) sea urchins and mussels; sea stars and kelp

Question 44

Two species eat the same prey, which is a limiting resource, and both their populations remain stable.Species A is removed, and the population of species B begins to increase rapidly.This suggests that the two species are _______ and the interaction is _______.

A) predator and prey; positive
B) predator and prey; negative
C) competitors; positive
D) competitors; negative
E) competitors; neutral

Question 45

Gopher tortoises are native to the southeastern United States.Which characteristic of gopher tortoises would best support the claim that they act as both keystone and ecosystem engineering species in their communities?

A) They are adapted to a variety of dry habitats.
B) They dig deep burrows that provide homes for nearly 400 animal species.
C) They eat many kinds of plants, but rarely drink water.
D) Their population is currently in steep decline.
E) They have a long history of successful adaptation.

Question 46

An ecologist studying interaction strength in a pond set up laboratory experiments using aquaria.He set up food webs in two aquaria that included these interactions: After populations in the aquaria stabilized, the ecologist removed the small fish from one aquarium.The population of Daphnia there immediately increased rapidly.This indicates that the interactor species (fish) had what effect on the target species (Daphnia)?

A) No interaction
B) Strong positive interaction
C) Strong negative interaction
D) Weak positive interaction
E) Weak negative interaction

Question 47

Which trophic interaction in a community is an indirect interaction?

A) Pocket gophers eat berries.
B) Coyotes eat pocket gophers, causing an increase in berry-producing plants.
C) Coyotes and short-tailed weasels both eat pocket gophers.
D) Coyotes and ravens eat carrion from dead elk.
E) Beavers eat the bark and leaves of aspen and the leaves and twigs of willow.

Question 48

Plant species A has only one pollinator; if the pollinator disappears, the plant is not pollinated and its numbers decline.Plant species B has multiple pollinators; if a single pollinator disappears, the remaining pollinators ensure that species B is still pollinated and its numbers remain stable.Which species shows the greatest interaction strength with its pollinators?

A) Species A, because its numbers decline if its pollinator disappears
B) Species A, because its only pollinator is less efficient than species B's pollinators
C) Species B, because it has multiple pollinators
D) Species B, because it only loses one pollinator
E) Species B, because its numbers remain stable when it loses a pollinator

Question 49

Refer to the graph, showing the interaction between the elk population and the presence or absence of wolves in Yellowstone National Park. Elk culling (hunting by humans) occurred until 1968.Based on this information, what factor had the most influence on the population of elk between 1926 and 1968?

A) Wolf predation
B) Culling by humans
C) Predation by both wolves and humans
D) Lack of predation
E) A factor other than predation

Question 50

Beavers modify their habitat by building dams, which create wetlands, meadows, and ponds for themselves and other species.Humans also alter habitats, clearing forests and grasslands for agriculture and urban development.Beavers and humans can be considered both

A) ecosystem engineers and keystone species.
B) predator species and ecosystem engineers.
C) primary producers and foundation species.
D) decomposers and ecosystem engineers.
E) keystone species and primary producers.

Question 51

In the Eel River of Northern California, the food web includes the following set of interactions: Assuming this set of interactions is controlled by a trophic cascade, what changes would be expected if the predatory fish were removed?

A) Increases in all other levels
B) Decreases in all other levels
C) Increases in fish larvae, predatory insects, and midge larvae; decrease in algae
D) Increases in fish larvae and predatory insects; decrease in midge larvae; increase in algae
E) Decreases in fish larvae and predatory insects; increase in midge larvae; decrease in algae

Question 52

In a salt marsh habitat, snails feed on marsh grasses, and blue crabs feed on snails.A high population of snails can graze the marsh so intensely that it becomes a mudflat.When blue crabs are present, the levels of all three species remain balanced and the marsh is healthy.What change in the salt marsh would be expected if blue crabs were removed?

A) No change, except the marsh would have one less predator
B) A trophic cascade leading to the marsh becoming a mudflat
C) A corresponding decrease in snails and marsh grasses
D) Immigration of another predator to replace blue crabs
E) An increase in marsh grasses and a decrease in snails

Question 53

A trophic cascade includes which kind(s) of interactions?

A) Direct interactions only
B) Indirect interactions only
C) Both direct and indirect interactions
D) Abiotic interactions only
E) Both biotic and abiotic interactions

Question 54

Corals affect their communities by producing elaborate limestone skeletons (coral reefs) that provide habitat for thousands of species and by helping to concentrate resources on the reef.Sea otters affect their communities by acting as top predators that generate trophic cascades, helping to maintain species richness, abundance, and composition.Are these animals considered keystone species or foundation species?

A) Both are keystone species.
B) Both are foundation species.
C) Corals are a keystone species; sea otters are a foundation species.
D) Corals are a foundation species; sea otters are a keystone species.
E) Both may fit either category, depending on the specific community.

Question 55

Several woodpecker families inhabited dead trees, or snags, in a large backyard.They fed on many kinds of insects in the homeowner's garden.In an effort to "clean up" the backyard, the owner removed the snags.Having lost their nesting sites, the woodpecker families moved to a nearby woodland community, where they both nested and fed.There was a sudden, large boom in insect populations feeding on the garden plants.Based on this information, what is the best description of the interaction, and its strength, between the interactor species (woodpeckers) and the target species (insects)?

A) Strong positive interaction
B) Strong negative interaction
C) Weak positive interaction
D) Weak negative interaction
E) No interaction

Question 56

The reintroduction of wolves into Yellowstone Park in 1995 had a(n) _______ effect on aspen and _______ effect on elk.

A) direct; a direct
B) direct; an indirect
C) direct; no
D) indirect; a direct
E) indirect; an indirect

Question 57

Which statement describes an important difference between a keystone species and a foundation species?

A) Keystone species tend to be larger and more abundant than foundation species.
B) Foundation species tend to be larger and more abundant than keystone species.
C) Keystone species have large effects on communities; foundation species have smaller effects.
D) Keystone species have small effects on communities; foundation species have larger effects.
E) Keystone species have strong interactions with other community members; foundation species do not.

Question 58

The intermediate disturbance hypothesis states that a community experiencing an intermediate level of disturbance will have higher species diversity than it would with low or high disturbance.What is a major justification for this hypothesis?

A) Low disturbance would lead to more extinctions, high disturbance to competitive exclusion.
B) Low disturbance would lead to competitive exclusion, high disturbance to more extinctions.
C) Low disturbance would lead to reduced influence by the dominant species, high disturbance to more extinctions.
D) Low disturbance would lead to reduced influence by the dominant species, high disturbance to competitive exclusion.
E) Low disturbance would lead to higher mortality rates, high disturbance to reduced influence by the dominant species.

Question 59

Charles Darwin observed the following interactions among plants and animals in his region of England: Bees pollinate flowers and make seed production possible.Field mice prey on bee combs and nests.Cats eat field mice.From these observations, he concluded that cats could control the populations of certain flowers.On what did he base this conclusion?

A) A direct and obvious interaction of cats and flowers
B) A direct and invisible interaction of cats and flowers
C) An indirect action leading from cats through mice back to bees and then flowers
D) An indirect and obvious action leading from cats to bees to flowers
E) An indirect and invisible action leading from cats to bees to flowers

Question 60

Many species are introduced outside their normal ranges deliberately, for specific purposes.Some of these (such as the honey bee) integrate into natural communities; others (such as the gypsy moth) reproduce out of control, become pests, and are defined as "invasive." Which of the following could be a difference in the way these two categories of introduced species changed a community's structure?

A) Only invasive introduced species participated in the native food web.
B) Only noninvasive introduced species participated in the native food web.
C) Only invasive introduced species seriously harmed native species.
D) Only noninvasive introduced species seriously harmed native species.
E) Only noninvasive introduced species overpopulated or outcompeted native species.

Question 61

Primary succession is most likely to occur after a(n)

A) hurricane.
B) wildfire.
C) forest is clear-cut.
D) volcano erupts.
E) agricultural field is abandoned.

Question 62

In 1988, fires in Yellowstone National Park affected over 36 percent of its area.Where the fires burned hottest, most plants, including forest trees, were killed.Where the fires were less severe, forest trees survived and only smaller plants were killed.What is most likely to happen in terms of succession in situations like this?

A) Primary succession will occur in all burned areas.
B) No succession will occur where fires burned the hottest, and secondary succession will occur where fires were less severe.
C) Primary succession will occur where fires burned the hottest, and secondary succession will occur where fires were less severe.
D) Secondary succession will occur where fires burned the hottest, and primary succession will occur where fires were less severe.
E) Secondary succession will occur in all burned areas.

Question 63

Following a severe ice storm, the composition of the trees changed in a community as it recovered from the disturbance.This is an example of _______ succession.

A) inhibition
B) competitive
C) primary
D) secondary
E) keystone

Question 64

Lottery, or neutral, models are most appropriately used for which types of communities?

A) Somewhat diverse communities in remote areas where other species are unlikely to enter
B) Unstable communities with changing species compositions and frequent disturbances
C) Communities with very low diversities, such as deserts and polar regions
D) Communities with low and erratic levels of resources, such as areas subject to periodic droughts
E) Highly diverse communities, such as tropical rainforest trees, which have many species with similar resource requirements

Question 65

The ages of the moraines of Glacier Bay show the pattern of succession that has occurred there.On the oldest moraines, the communities are dominated by

A) bacteria, fungi, and photosynthetic microorganisms.
B) willows and cottonwood trees.
C) Sitka spruce trees.
D) shrubby willows and alder trees.
E) lichens, mosses, and shrubs such as Dryas.

Question 66

Which situation would likely be considered a stress, rather than a disturbance?

A) A tree falls in a forest
B) An entire forest is clear-cut
C) A forest is subjected to air pollution, inhibiting photosynthesis
D) A forest fire erupts and destroys a large segment of a forest
E) A construction crew builds a road through a forest

Question 67

Which of these is a biotic factor that can affect community structure?

A) A flood
B) A forest fire
C) Extreme temperatures
D) Elephants trampling a grassland
E) A hurricane felling trees

Question 68

What factor can best be used to distinguish a disturbance from a stress in a community?

A) The strength of the effect and the amount of area it covers
B) Whether it is biotic or abiotic
C) Whether it is naturally caused or caused by humans
D) Whether it acts by chemical or physical factors
E) Whether it physically injures or kills, or simply reduces growth and reproduction

Question 69

Keystone species and foundation species are sometimes also ecosystem engineers, which change the environment and provide habitat for a variety of species.In the process, they have a profound effect on community structure.Which of the following would be considered members of keystone or foundation species but not ecosystem engineers?

A) Beavers that cut down trees and dam streams, changing flowing water into ponds
B) Porcupines that, while digging for food, create soil pits that persist and create plant habitats
C) Termites that build mounds, increasing soil fertility and plant density in the area
D) Woodpeckers that excavate holes in dead trees, creating habitats for a variety of species
E) Sea otters that act as top predators and start trophic cascades in kelp ecosystems

Question 70

Would disturbance or stress be likely to have the most rapid effect on community structure?

A) Disturbance, because disturbance always has a larger overall effect
B) Disturbance, because it injures or kills immediately, making room for other organisms
C) Stress, because it involves changes in reproduction and/or growth
D) Stress, because stress always results in stronger long-term effects
E) Either, depending on the individual situation

Question 71

Human activities are causing many stresses in nearshore estuarine habitats, which are vital habitats for breeding and development of young marine fish and other animals.These stresses are occurring as a result of climate change, pollution, coastal construction, and a variety of other factors.Of the changes that occur in estuaries, which would not be considered a stress?

A) Increased salinity when drought decreases freshwater inputs
B) Increased acidity (decreased pH) as atmospheric CO₂ rises
C) Excess sediment due to nearshore dredging activities
D) A ban on a fishery that has been depleting fish stocks
E) Introduction of a non-native fish species that competes with native species

Question 72

An ecological community has existed for a long time, operating in ways that conform with the lottery (neutral) model.Individuals of different species have obtained resources randomly, by being in the "right place at the right time." A new animal species immigrates into the community.This species is a predator and (compared with others in the community) is aggressive at seeking out prey.How is this new species likely to affect community function?

A) There will be little change; the new species will fit in but maintain its own characteristics.
B) There will be little change; the new species will adapt and obtain resources randomly.
C) The new species will outcompete other predators; the community will no longer operate as the neutral model does.
D) The new species will outcompete other predators, but the rest of the community will remain unaffected.
E) The new species will be unable to fit into the established community and will quickly die out.

Question 73

Rising ocean temperatures are affecting coral reefs around the world.When temperatures become too high, the corals undergo bleaching; that is, the algae living inside them leave.Corals depend on these algae for 90 percent of their energy.What will most likely happen if temperatures remain higher than the corals' preferred range for an extended time period?

A) The corals will die.
B) The corals will obtain energy from other sources.
C) The corals will quickly adapt to the higher temperatures.
D) New algae will move in and the corals will recover.
E) The corals will survive but will be less healthy.

Question 74

There are often low levels of herbicides in agricultural soils and on the leaves and flowers of orchard trees.They are meant to kill weeds rather than insects, and levels are very low, but they may cause physiological changes in insect pollinators, making them weaker, with lower reproductive rates, and less effective at pollinating.These effects suggest that pesticides in orchards act as a _______ to pollinators.

A) disturbance
B) stress
C) disease
D) competitor
E) stimulant

Question 75

After a major disturbance wipes out or seriously damages a community, the community's usual response is to undergo

A) extinction.
B) succession.
C) dormancy.
D) another disturbance.
E) immediate recovery.

Question 76

In 1963, an oceanic volcanic eruption off the southern coast of Iceland formed the island of Surtsey.Given the process of primary succession, which organisms were likely the first to establish populations on the new island?

A) Bacteria
B) Flies
C) Mosses
D) Flowering plants
E) Songbirds

Question 77

A hurricane devastates a region of the Gulf Coast.Its winds destroy many trees and damage other natural environments.This situation would be described ecologically as a(n)

A) stress.
B) obstruction.
C) catastrophe.
D) climax.
E) disturbance.

Question 78

Which is the correct chronological order (from earliest to latest) for the succession of plant species in Glacier Bay?

A) Alders $\rightarrow$ spruces $\rightarrow$ lichens
B) Spruces $\rightarrow$ alders $\rightarrow$ lichens
C) Spruces $\rightarrow$ lichens $\rightarrow$ alders
D) Lichens $\rightarrow$ spruces $\rightarrow$ alders
E) Lichens $\rightarrow$ alders $\rightarrow$ spruces

Question 79

Refer to the graph, showing the percentage of aspens added to the Yellowstone National Park forests each decade for a century, with and without the presence of wolves. When present, wolves in the park feed on elk and control the elk population.Elk graze on aspen trees.Based on the graph, one can conclude that when wolves are not present to control the size of the elk population, aspen forests are

A) not affected.
B) browsed heavily and disappear completely.
C) browsed heavily but rebound after wolves return.
D) browsed less and eventually recover.
E) browsed less but do not recover.

Question 80

Lottery models of natural communities are considered neutral because they assume that

A) communities having low diversity have an advantage.
B) communities having few resources have an advantage.
C) all species have equal opportunities to obtain resources.
D) all species must compete strongly to obtain resources.
E) there is always a dominant competitor in a community.