Deck 18: Community Structure

Question 1

Use Figure 18.10a for MC questions 20 - 22.

Which curve suggests that species richness is controlled by bottom-up factors?

A) U-shaped
B) negative
C) none
D) positive
E) hump-shaped

Answer 1

D

Question 2

How does an ecologist determine the presence of an ecotone?

A) measure the abundance of plant species over space and abrupt changes in species composition
B) perform controlled crosses among all plant species within a community to determine the extent to which the species are reproductively isolated
C) measure microclimate and soil variables for abrupt changes
D) measure elevation, since many environmental and ecological variables change with elevation

Answer 2

A

Question 3

Use Figure 18.10a for MC questions 20 - 22.

What would be the most likely species richness-productivity relationship for a community in which the species were not resource limited?

A) U-shaped
B) negative
C) none
D) positive
E) hump-shaped

Answer 3

C

Question 4

Use the figure to answer questions 4 to 7.

Which species is restricted to serpentine soils?

A) black oak b hawkweed
C) ragwort
D) fireweed

Question 5

Which concept suggests that a community is much more than the sum of its individual parts?

A) holistic concept
B) individualistic concept
C) concept of independence
D) ecotone concept

Question 6

The graph suggests that

A) plant survival rate is not affected by elevation.
B) plant survival rate is not affected by the presence or absence of a neighbouring species.
C) plant survival is dependent on the presence of a neighbouring species.
D) plant survival is independent of the presence of a neighbouring species.

Question 7

What community measure does Shannon's index quantify?

A) the number of species
B) relative abundance of species
C) species richness
D) species diversity

Question 8

How would adding resources such as fertilizer to an area affect the species in a community?

A) It would reduce richness.
B) It would increase richness.
C) It would increase the abundance of all species.
D) It would reduce the abundance of all species.

Question 9

Which concept suggests that a community is a collection of species whose adaptations and requirements enable them to live together under the physical and biological conditions of a particular place?

A) holistic concept
B) individualistic concept
C) concept of independence
D) ecotone concept

Question 10

Use the figure to answer questions 4 to 7.

Which species is restricted to the ecotone between serpentine and nonserpentine soils?

A) black oak
B) hawkweed
C) ragwort
D) fireweed

Question 11

Based on examples from the chapter, do most communities consist of species with independent or interdependent distributions? What particular types of environmental conditions favour one or the other type of distribution?

Question 12

Based on the data that follow, which of the following statements is FALSE?

A) The seagrass habitat has the lowest species richness.
B) The African plains and Australian grasslands have identical species richness.
C) The diversity (D) of African plains and Australian grasslands is the same.
D) The Australian grasslands have lower species evenness than the African plains.
E) The seagrass habitat has the highest species evenness.

Question 13

Use the figure to answer questions 4 to 7.

Which species is restricted to nonserpentine soils?

A) black oak
B) hawkweed
C) ragwort
D) fireweed

Question 14

Use the figure to answer questions 4 to 7.

Which species would you characterize as seemingly unresponsive to changes in soil conditions across the transect?

A) black oak
B) hawkweed
C) ragwort
D) fireweed

Question 15

How can predation increase prey species richness and evenness in a community?

Question 16

How would sampling the same community in the plot with much less effort affect the shape of the plot?

Question 17

Briefly describe an experiment to test whether species are independent or rely on each other for existence.

Question 18

What, in addition to tolerance to soil characteristics, might account for the distribution of plant species over different soil types?

Question 19

Communities with ____________ species are ____________ stable.

A) few; more
B) few; consistently
C) many; more
D) many; consistently

Question 20

What species richness-productivity relationship has the Park Grass experiment in England demonstrated over the past 150 years?

A) U-shaped
B) negative
C) none
D) positive
E) hump-shaped

Question 21

Which of the following is NOT an example of a trait-mediated indirect effect?

A) The presence of raptors causes squirrels to forage at night instead of during the day.
B) Greater numbers of aspen trees grow in areas where predation risk from wolves prevents elk from browsing.
C) Grasses increase because the presence of spiders has reduced grasshopper foraging.
D) Zooplankton abundance in a pond increases because piscivorous largemouth bass cause small fish (zooplanktivores) to take refuge in pond margins away from zooplankton.

Question 22

Why are keystone species important in food webs?

Question 23

A researcher removed predatory starfish from sections of intertidal rock and found that the number of prey species decreased by 50 percent relative to control plots within a short time. This indicates: that

A) predators compete with prey for space.
B) predator species are competing for prey.
C) starfish predation increases prey diversity.
D) starfish predation reduces prey diversity.

Question 24

Use the following figure for questions 24 and 25.

According to the experimental results shown in the figure, what factor best explains the reduction in plant species richness with addition of fertilizer?

A) inhibition of photosynthesis
B) intolerance to fertilizer
C) competitive exclusion
D) interaction of fertilizer and light

Question 25

Which is an example of an ecosystem engineer?

A) beavers, which build dams on streams
B) termites, which build very large hives and eat the wood in buildings
C) bees, which pollinate many types of flowers and crops
D) zebra mussels, which clog water intake structures

Question 26

Which is an example of a trait-mediated indirect effect?

A) A predator causes a consumer to change its foraging pattern, affecting the amount of food consumed.
B) Predators consume most of their main prey, then switch to omnivory.
C) Herbivores migrate in and out of communities depending on perceived predation risk.
D) Herbivores consume vegetation, which reduces hiding places for predators stalking their prey.

Question 27

When Hairston, Smith, and Slobodkin suggested that Earth is green because carnivores depress the populations of herbivores that would otherwise consume most vegetation, they were focusing on __________ control of community structure.

A) top-down
B) bottom-up

Question 28

Keystone species that are predators in a food web can increase species diversity by

A) increasing the biomass of primary producers.
B) removing competitive dominants.
C) creating an intermediate disturbance.
D) increasing production efficiency.

Question 29

What is a major distinction between direct and indirect effects in a community?

A) Indirect effects always include a resource such as water or light; direct effects do not.
B) Direct effects result in competitive exclusion; indirect effects do not.
C) Direct effects occur between species in different trophic levels; indirect effects include species from the same trophic level.
D) Indirect effects always include more than two species; direct effects do not.

Question 30

The presence of fish has a positive effect on shoreline flowering plants. Which lines in the diagram reflect a negative direct effect?

A) fish → adult dragonfly
B) fish → pollinator
C) fish → larval dragonfly
D) adult dragonfly → plants

Question 31

A trophic cascade is an example of _____ effect.

A) direct
B) indirect

Question 32

Explain whether species would be limited more by resources or interspecific interactions in tropical rainforests (low latitude) or taiga (high latitude).

Question 33

What population trait allows a species to have high resilience to disturbance?

Question 34

Carbon dioxide with radioactive carbon was bubbled into an illuminated aquarium containing unfiltered pond water. In what order will radioactivity appear in various organisms in the aquarium?

A) herbivores, carnivores, producers
B) producers, herbivores, carnivores
C) producers, carnivores, herbivores
D) herbivores, producers, carnivores
E) All organisms will take up radioactive carbon simultaneously.

Question 35

You have been keeping a list of the bird species that frequent your property. At the end of the year you have tallied eight seed eaters, one nectar sipper, three woodpeckers, six insectivores, two frugivores, four predators, and one carrion feeder. You have organized your tally according to

A) habitat.
B) community.
C) population.
D) guild.

Question 36

Consider invertebrates such as starfish and mussels on a rocky intertidal habitat where tidal cycles cause the animals to move between exposure and submersion. Are these changing conditions considered a disturbance?

Question 37

Explain what the intermediate disturbance hypothesis predicts for the comparison of species richness in forests where fires have been suppressed versus those with unsuppressed natural fire.

Question 38

Keystone species

A) have the most biomass in a community.
B) are usually top predators.
C) can affect community structure despite low abundance.
D) are invasive predator species that eat native herbivores.

Question 39

Use the following figure for questions 24 and 25.

What is the relation between habitat diversity and species diversity?

A) decrease with altitude
B) hump shape
C) positive
D) negative if many invasive species are present

Question 40

Use the following figure for questions 24 and 25.

What is a reasonable explanation of the results in the figure?

A) The plants are light limited.
B) Plants that competed more successfully for fertilizer shaded out other plants.
C) Plant growth is best supported by addition of fertilizer and light.
D) Addition of fertilizer reduces plants' ability to use light efficiently for photosynthesis.

Question 41

Which statement best reflects the relationship between a disturbance and an alternative stable state?

A) Many communities alter between stable states on a seasonal basis, which is not a true disturbance.
B) A community will achieve an alternative stable state only after a major disturbance.
C) An alternative stable state will not happen in aquatic communities, where there is no fire and water is not limiting.
D) Communities can alternate among stable states in the absence of disturbance.

Question 42

The dams that have been built on many rivers stabilize river flow by increasing flows below the dam during droughts and decreasing the amount of flooding during periods of high rainfall. Explain how these stabilized flows can be considered as a disturbance.

Question 43

What is the suggested mechanism by which the presence of insecticide influences phytoplankton abundance?

A) Periphyton abundance is reduced by insecticide.
B) Tadpoles consume phytoplankton when periphyton is reduced in abundance.
C) The reduction of zooplankton by insecticide reduces herbivory on phytoplankton, which increases abundance.
D) Inert chemicals in the insecticide include nitrogen, which promotes phytoplankton growth.

Question 44

Which of the following statements would NOT be true about the species relationship in the figure?

A) Zooplankton consume phytoplankton.
B) Zooplankton consume periphyton.
C) Tadpoles consume periphyton.
D) Tadpole abundance is related to the abundance of its food resource.

Question 45

What do the data in the graphs suggest about the resistance of the community to disturbance?

A) Communities with any amount of plants are very resistant to disturbance.
B) Community resistance depends on whether herbivores, predators, and parasites are present.
C) Herbivore species richness and abundance both increase with small changes in plant species richness.
D) The stability of herbivore species richness and abundance respond independently of plant species richness.

Question 46

What organisms in the figure appear NOT to be indirectly affected by insecticide?

A) zooplankton
B) tadpoles
C) phytoplankton
D) periphyton

Question 47

Which response variable (on the y axis) did not increase with plant species richness?

A) stability of herbivore species richness
B) stability of herbivore abundance
C) stability of predator and parasite species richness
D) stability of predator and parasite abundance

Question 48

Explain how the second law of thermodynamics limits the number of trophic levels in a food web.

Question 49

Explain the relationships that appear to reduce tadpole abundance when insecticide is present, even though insecticide does not directly affect tadpoles.

Question 50

What can we learn about the roles of species in a community from food web structure alone?

Question 51

What most accurately describes a trophic cascade?

A) bottom-up effects
B) top-down effects
C) found in waterfall habitats
D) is based on two trophic levels

Question 52

Which would likely have very high resilience to disturbance?

A) soil microbes
B) redwood forest
C) desert vegetation
D) grassland

Question 53

How would a relatively high proportion of omnivore species in a food web affect the connectedness of the food web?

Question 54

What is the difference between a food chain and food web?

Question 55

Hairston, Smith, and Slobodkin suggested that Earth is green because carnivores depress the populations of herbivores that would otherwise consume most vegetation. Is this the only possible explanation for the greenness of Earth?

Question 56

Which relationships in the figure indicate top-down control? Which relationships indicate bottom-up control?