Deck 17: Species Interactions and Community Structure

Question 1

It had been thought that Brassica nigra competitively displaced the native grass Nassella pulchra, but Orrock et al. showed that it was likely apparent competition when

A) B. nigra shaded out N. pulchra.
B) N. pulchra did not germinate near B. nigra.
C) B. nigra sheltered mammal herbivores which consumed N. pulchra.
D) B. nigra had higher survival after fire than N. pulchra.
E) All of the choices are correct.

Answer 1

C

Question 2

In Robert Paine's studies of the Washington intertidal community, which organism proved to be a keystone species?

A) The whelk Thais
B) Acorn barnacles
C) Chitons
D) The starfish Pisaster
E) Limpets

Answer 2

D

Question 3

The use of predaceous weaver ants to control pest insects in citrus orchards was first recorded in

A) California in the 1950s.
B) Florida in the 1920s.
C) Mexico in Mayan times.
D) China in the 17th century.
E) China in the 4th century.

Answer 3

E

Question 4

Cleaner wrasse are mutualists of other coral reef fishes. What benefit do they provide to those other fish?

A) They suppress diseases because they consume carcasses of dead fish.
B) They keep water oxygenated because they consume organic debris before it can rot.
C) They keep fish relatively free of externally feeding parasites.
D) They maintain fish habitat by keeping corals free of encrusting algae.
E) They reduce fish mortality by repelling large vertebrate predators.

Question 5

Which statement best sums up the relationship between density of the herbivorous snail Littorina and the diversity of algae in its habitat?

A) Highest diversity when Littorina are abundant, in all habitats
B) Highest diversity when Littorina are rare, in all habitats
C) Highest diversity when Littorina densities are intermediate, in all habitats
D) Highest diversity in tidepools when Littorina are rare, but in emergent habitats when Littorina densities are intermediate
E) Highest diversity in tidepools when Littorina densities are intermediate, but in tidepools when Littorina are rare

Question 6

Teja Tscharntke's studies of the food web associated with Phragmites reeds revealed that

A) only a single parasitoid species can persist exploiting a single species of herbivore.
B) only a single herbivore species can persist attacking a single species of plant.
C) predation by birds actually protects herbivores, because the birds feed on parasitoid-infested herbivore galls but not uninfested galls.
D) within local food webs, all interactions tend to be of roughly the same strength.
E) recognizing variation in interaction strength can greatly simplify the depiction of a food web.

Question 7

Which is the correct order of prey consumption in the Antarctic pelagic food web?

A) Krill→Diatoms→Ross seal→Crabeater seal→Killer Whale
B) Diatoms→Krill→Ross seal→Crabeater seal→Killer Whale
C) Diatoms→Squid→Emperor penguin→Leopard seal→Killer whale
D) Krill→Squid→Weddell seal→Leopard Seal→Killer whale
E) Diatoms→Squid→Krill→Emperor penguin→Leopard seal

Question 8

Kirk Winemiller, who described the feeding relations among freshwater fish in Venezuela and Costa Rica, simplified the food webs from his study sites by presenting common-fish webs. Common-fish webs

A) exclude rare species.
B) both exclude rare species and include the fish species whose aggregate abundance comprise 95% of the individuals collected.
C) exclude species that do not comprise at least 30% of the community.
D) include the fish species whose aggregate abundance comprise 95% of the individuals collected.
E) exclude species that do not comprise at least 40% of the community.

Question 9

Invasive Argentine ants have an important effect on community structure of the South African fynbos because

A) they do not disperse seeds, while native ants do.
B) they disperse seeds more effectively than do native ants.
C) they disperse seeds in different spatial patterns than do native ants.
D) as keystone species, they greatly increase the local diversity of native ants.
E) Argentine ants have invaded many communities, but not the South African fynbos.

Question 10

Martinsen, Driebe, and Whitham provided evidence for ________ with beaver consumption of cottonwoods resulting in higher densities of herbivorous beetles.

A) indirect keystone predation
B) indirect commensalism
C) apparent competition
D) keystone predation
E) indirect competition

Question 11

A predator and its prey interact ________, but if the predator affects another species through this interaction, ecologists describe it as a(n) ________ interaction.

A) strongly; inefficient
B) directly; variable
C) weakly; diffuse
D) indirectly; keystone
E) directly; indirect

Question 12

Based on studies by Jane Lubchenco, what influence does the population density of the herbivorous intertidal snail, Littorina littorea, have on the number of algal species?

A) As snail density increases from low to medium, the number of algal species increases.
B) As snail density increases from medium to high, the number of algal species increases.
C) As snail density increases from low to medium, the number of algal species decreases.
D) As snail density increases from medium to high, the number of algal species decreases.
E) Both as snail density increases from low to medium, the number of algal species increases and as snail density increases from medium to high, the number of algal species decreases.

Question 13

In the Washington intertidal community studied by Robert Paine, the most important limiting resource is

A) space.
B) light.
C) plankton.
D) nitrogen.
E) water.

Question 14

A keystone species is one

A) that makes up a very large proportion of total community biomass.
B) that feeds on a very large fraction of all available prey species.
C) that is fed on by a very large fraction of all predators in its community.
D) whose feeding activities have a disproportionate effect on the structure of its community.
E) that occupies the lowest level (the base) of the food web.

Question 15

Keystone species

A) appear to be common in terrestrial systems, but not in aquatic ones.
B) appear to be common in both terrestrial and aquatic systems.
C) appear to be common in aquatic systems, but not in terrestrial ones.
D) by definition, cannot occur in aquatic systems.
E) by definition, cannot occur in terrestrial systems.

Question 16

Weaver ants provide effective protection of citrus trees because they

A) remove harmful soft-scale insects (mealybugs).
B) remove all plant-feeding insects.
C) cultivate soft-scale insects, but do not allow them to feed on the trees.
D) cultivate soft-scale insects, but still allow them to be attacked by parasitoids and predators.
E) None of the choices are correct.

Question 17

Human hunters in the Amazon rain forests kill

A) large numbers of almost every mammal and bird species, for food and for skins.
B) large numbers of the smallest mammal and bird species, which are easiest to catch.
C) large numbers primarily of the largest mammal and bird species.
D) large numbers of mammals and birds, but do not greatly affect population densities.
E) only a few mammals and birds, but because humans are keystone species, these few kills greatly reduce population densities.

Question 18

Teja Tscharntke simplified the food web associated with the wetland reed Phragmites australis by dividing the species into which of the following major trophic levels?

A) Plant, herbivore, piscivore, granivore
B) Herbivore, carnivore, detritivore, consumer
C) Herbivore, parasite, carnivore, detritivore
D) Plant, herbivore, parasite, carnivore
E) Plant, detritivore, parasite, herbivore

Question 19

In zooplankton and intertidal communities, as the overall diversity of the food web increases, the proportion of predators in the web

A) tends to decrease.
B) tends to increase.
C) first decreases, then increases again.
D) first increases, then decreases again.
E) stays about the same.

Question 20

In Jane Lubchenco's tidepool system, removal of the herbivorous snail Littorina led to

A) dominance of the tidepools by the unpalatable alga Chondrus.
B) replacement of Chondrus by the more palatable alga Enteromorpha.
C) replacement of Chondrus by other algae better adapted to herbivory.
D) replacement of Enteromorpha by other algae that are better competitors.
E) no marked change in the algal community.

Question 21

The impact of Argentine ants on species diversity in the South African fynbos is most dramatic following fires.

Question 22

The presence of cleaner wrasse enhances diversity of fishes on coral reefs.

Question 23

Ecologists summarize feeding interactions among species in a community when they compile a ________.

Question 24

Removal of Pisaster starfish in the Washington intertidal leads to a decline in diversity of other invertebrate species.

Question 25

What would be the most likely effect of removing the blue tit from the Phragmites australis ecosystem?

A) An increase in the populations of Aprostocetus gratus and Platygaster cf. quadrifarius and a decrease in the number of small Giraudiella inclusa gall clusters
B) An increase in the populations of Aprostocetus orithyia, Eudecatoma stagnalis, Eurytoma crassinervis, and Platygaster szelenyii and a decrease in the number of small and large Giraudiella inclusa gall clusters
C) A decrease in the populations of Aprostocetus calamarius and Torymus arundinis and a decrease in the number of large Giraudiella inclusa gall clusters
D) An increase in the populations of Aprostocetus calamarius and Torymus arundinis and an increase in the number of large Giraudiella inclusa gall clusters

Question 26

If Brassica nigra and Nassella pulchra were in direct competition, the density of N. pulchra would increase with distance from B. nigra patches, regardless of the abundance of herbivores.

Question 27

In a mangrove forest in Central America, mangrove trees were found to contain between 60-85% of the total above-ground biomass. How would you categorize mangrove trees in this ecosystem?

A) A foundation species
B) A keystone species
C) Both a foundation and a keystone species
D) Neither a foundation nor a keystone species

Question 28

Which research methods were used by both Redouan Bshary and Caroline Christian in their studies of mutualistic keystone species? (Select all that apply.)

A) Experimental removal and addition of organisms
B) Natural removal and addition of organisms
C) Counting and identification of organisms
D) Comparison of different spatial areas
E) Median change in species richness