Chapter 17 Species Interactions and Community Structure

Question 1

In food webs, a feeding relationship is represented as a(n) ______ connecting two ______.

Answer 1

line; organisms

Question 2

In representing the communities in Caño Volcán, one approach used by Winemiller was to _______ the most rare species.

Answer 2

exclude

Question 3

In defining “strong interactions” in food webs, Paine felt that the most important factor in defining community structure was the ______, but not the ______ of interactions.

Answer 3

degree of influence; energy flow

Question 4

Species that have a substantial influence on community structure due to their high biomass are referred to as ______ species

Answer 4

foundation

Question 5

True or false: Blue Tits feed on larvae of the moth, A. geminipuncta.

Answer 5

False

They feed on the galls formed by G. inclusa thus forming a species interaction.

Question 6

Food webs are ______.

Answer 6

used to represent feeding relations within a community

Question 7

Which of the following interactions are considered to be strong interactions in Tscharntke’s food web of a Phragmites community?

Answer 7

Phragmites–A. geminipuncta

Phragmites–G. inclusa

T. arundinis–C. caerulus

Question 8

In representing the communities in Caño Volcán, one approach used by Winemiller was to _______ the weakest trophic links.

Answer 8

exclude

Question 9

Indirect interactions between two species require ______ species.

Answer 9

an intermediate

Question 10

The most influential trophic relationships in a food web are known as ______ interactions.

Answer 10

strong

Question 11

In a commensal relationship between two species, one species is ______ while there is neither harm nor benefit to the other.

Answer 11

benefited

Question 12

In the Martinsen et al. study, the sprouts growing from trees felled by beaver have leaves that are ______ nutritious for the beetles than those growing on mature trees.

Answer 12

more

Question 13

Which of the following trophic interactions were observed in the Phragmites community studied by Tscharntke? Arrows indicate the direction of energy flow, for example, A → B, indicates that A is eaten by B.

Answer 13

fly (G. inclusa) —> Blue tits

Phragmites —> moth (A. geminipuncta)

Phragmites —> fly (G. inclusa)

Question 14

Stem-boring by larvae of ______ are responsible for inducing Phragmites to produce side branches.

Answer 14

A. geminipuncta

Question 15

In the following, simplified food chain, which pairs of species have indirect interactions? Sp. A —–> Sp. B —–> Sp. C —–> Sp. D

Answer 15

Sp. A and Sp. C

Sp. B and Sp. D

Question 16

Apparent competition is a type of ______ interaction.

Answer 16

indirect

Question 17

Which of the following represents the indirect commensalism observed by Martinsen et al.?

Answer 17

Beaver — cottonwood — beetle

Question 18

The purpose of the control treatment, in the experiment by Orrock et al., was to ______.

Answer 18

account for disturbance effects

Question 19

Consistent with their hypothesis about apparent competition between mustard and bunch grass, Orrock et al. found ______ did better when ______ were excluded.

Answer 19

bunch grass; rodents

Question 20

Predators that keep prey populations below their carrying capacity and prevent competitive exclusion by one of these species are known as ______.

Answer 20

keystone species

Question 21

Indirect interactions between two species require ______ species.

Answer 21

an intermediate

Question 22

In the intertidal food web of Mukkaw Bay, a ______ is considered to be the top predator.

Answer 22

seastar

Question 23

If two species are joined through apparent competition, that means that they have a common ______.

Answer 23

predator

Question 24

In the intertidal food web of the Gulf of California there are a total of ______ predators in the system.

Answer 24

11

Question 25

The purpose of the experiment by Orrock et al. was to test for apparent competition between ______ and ______.

Answer 25

mustard; bunch grass

Question 26

As a result of their experiments, Orrock et al. proposed that the rodents use ______ for protective cover, feeding on the ______.

Answer 26

mustard; bunch grass

Question 27

A keystone species would be considered to be a type of ______.

Answer 27

foundation species

Question 28

Paine concluded that greater numbers of predators in an intertidal community produces increased ______, leading to an increase in ______ the community.

Answer 28

predation pressure; diversity of

Question 29

In the intertidal food web of Mukkaw Bay, the number of prey species eaten by the seastar Pisaster is ______ the number of prey species eaten by the snail Thais.

Answer 29

greater than

Question 30

In the intertidal food web of the Gulf of California, a ______ is considered to be the top level predator.

Answer 30

seastar

Question 31

In his first research in Mukkaw Bay on the role of predators in community diversity, Paine ______ predators for the experimental treatment in his study areas.

Answer 31

removed

Question 32

In the months immediately following the removal of starfish, the percent of space occupied by the barnacle Balanus ______.

Answer 32

increased

Question 33

Paine found that as the number of species in an intertidal food web increased, there was a(n) ______ in the number of predators in the community.

Answer 33

increase

Question 34

Which three of the following factors did Lubchenco propose to be necessary in order to resolve the conflicting results of herbivore–diversity experiments?

Answer 34

local competitive relationships herbivore food preference location-based changes in competition and food preferences

Question 35

Lubchenco conducted the feeding preference experiments with snails (Littorina) in a laboratory and found that perennial species of alga were eaten by the snails ______.

Answer 35

only when it was the only choice of food

Question 36

In his first research in Mukkaw Bay on the role of predators in community diversity, the experimental sites in the experiment received ______ predators.

Answer 36

no

Question 37

In studying the relationship between snail density and algal abundance, Lubchenco found that area's with ______ densities of snails had low densities of the alga Enteromorpha, a ______ food.

Answer 37

high; favorite

Question 38

Over the 2 years of Paine's experiments in Mukkaw Bay, the diversity of the predator-free experimental plots ______ while the control plots ______.

Answer 38

decreased; remained constant

Question 39

As in the Mukkay Bay experiment, Paine found that the removal of a sea star in the New Zealand intertidal experiment resulted in an increase in the area occupied by ______ species.

Answer 39

a prey

Question 40

True or false: Lubchenco's research on the relationship between herbivores and community diversity was motivated by conflicting results in previous experiments.

Answer 40

true

Question 41

Lubchenco conducted snail removal experiments in tidal pools and found that the algae species the snails liked to eat ______ when the snails were removed.

Answer 41

increased in abundance

Question 42

In feeding preference experiments with snails, Lubchenco found that ______ algae were generally preferred over those that are ______.

Answer 42

small tender; tough and perennial

Question 43

After a local population explosion of seagulls, you would expect to find ______ in the abundance of the alga Enteromorpha in the tide pools.

Answer 43

a decrease The seagulls would eat more crabs, and so there would be fewer crabs to eat snails. The increased number of snails would decrease the population of the algae (Enteromorpha) they like to eat.

Question 44

Lubchenco studied the relationship between algal abundance and snail densities in ______.

Answer 44

tide pools

Question 45

In the months immediately following the removal of starfish, the percent of space occupied by the barnacle Balanus ______.

Answer 45

increased

Question 46

In Lubchenco's study of tide pools, the snail Littorina performed a similar function to the ______ in Paine's Mukkaw Bay experiments—controlling the populations of the dominant space competitor.

Answer 46

Pisaster

Question 47

In both the Mukkaw Bay and New Zealand intertidal community experiments, Paine found that removal of a top predator led to ______ in the population of a space competitor.

Answer 47

an increase

Question 48

Algal species richness was greatest at which snail density?

Answer 48

middle

Question 49

In the tide pools in which Lubchenco removed snails, the abundance of the algae ______ increased, while the algae ______ decreased relative to the control treatment.

Answer 49

Enteromorpha (a favored-food choice); Chondrus

Question 50

Littorina's preference for feeding on ______ could produce the pattern of algal richness seen by Lubchenco.

Answer 50

the competitively dominant alga

Question 51

Which one of the following would best represent food web control on the population of the snail Littorina?

Answer 51

snail ---> crab ----> seagull

Question 52

In environments where Littorina's feeding preference is the competitively inferior alga taxa, algal richness will be lowest at which snail density?

Answer 52

high snail density

Question 53

Lubchenco's research ______ that of Paine, showing that a single species could control the diversity of a community.

Answer 53

supported

Question 54

Which of the following best represents the food web of the Eel River? (Note: the arrow ----> represents as feeding relationship, e.g., A-->B is A eaten by B.)

Answer 54

algae --> midges --> predatory insects --> small fish --> trout

Question 55

Organize the snail density conditions in order of increasing algal species richness in tide pools starting at the bottom. In other words, which snail densities produced lowest (at the bottom), middle and highest algal richness (at the top).

Answer 55

1. middle snail density 2. low snail density 3. high snail density

Question 56

At high densities, Littorina needed to switch to feeding on ______ in order to meet their energy needs.

Answer 56

less preferred alga species

Question 57

The purpose of the exclosure cages in Power's experiments was to exclude ______ from the study plots.

Answer 57

adults of the top predators

Question 58

Experimental enclosures receiving added numbers of trout would have a(n) ______ abundance of algae as compared to enclosures with fewer trout.

Answer 58

decreased

Question 59

In environments where Littorina's feeding preference is the competitively inferior alga taxa, rank the density conditions in order of decreasing algal species richness with the lowest at the bottom.

Answer 59

1. low snail density 2. middle snail density 3. high snail density

Question 60

In Power's study of stream communities, ______ performed a similar function as a keystone species to the snails in Lubchenco's experiments in tide pools.

Answer 60

trout

Question 61

In addition to feeding on invertebrates, the roach (fish) will also eat ______.

Answer 61

algae

Question 62

Cleaner fish remove and eat ______ from other fish in coral reef communities.

Answer 62

parasites

Question 63

Bshary observed the ______ reef patches and the presence or absence of cleaner wrasses.

Answer 63

number of fish species on

Question 64

In Power's experiments, she was trying to determine whether ______ and ______ were acting as keystone species.

Answer 64

steelhead; roach

Question 65

A disease wipes out most of the trout in the Eel River. Which of the following populations would you expect to increase, at least in the short term, as a result of this?

Answer 65

predatory insects roach fry Cladophora (diatoms)

Question 66

The results from Power's study of stream communities ______ those of Paine and Lubchenco showing that a single species could control the diversity of a community.

Answer 66

supported

Question 67

Experimental removal of cleaner wrasses from reef patches by Bshary resulted in ______ in the number of fish species on the patch.

Answer 67

a decrease

Question 68

The activities of cleaner fish are considered to be an example of ______.

Answer 68

mutualism

Question 69

By burying seeds of fynbos plants, ants help plants avoid losing those seeds to which of the following?

Answer 69

fires rodents

Question 70

True or false: Bhsary only observed naturally occurring densities of cleaner wrasses on reef patches.

Answer 70

false

Question 71

Redford considers species that have had their densities reduced to the point that they can no longer function as keystone species as ______.

Answer 71

ecologically extinct

Question 72

In looking at the communities on islands created by a dam impoundment that excluded large predators, Terbough observed changes to community structure that were so large that he described them as ______.

Answer 72

an ecological meltdown

Question 73

The ability of the predaceous fire ant to act as a keystone species in arthropod communities is ______ for corn and squash farmers.

Answer 73

a benefit

Question 74

Bshary found that reef patches with cleaner wrasses had a ______ number of fish species compared to patches where the wrasses were not present.

Answer 74

greater

Question 75

The weaver ants have a mutualistic relationship with mealy bugs - the ants receive __________ while the mealy bugs benefit from _______________.

Answer 75

fluids and carbohydrates; protection from predators

Question 76

Plants with large seeds produced ______ seedlings compared to plants that had small seeds that could be buried by ants.

Answer 76

fewer

Question 77

Yang found that the weaver ants did not attack _________ of the mealy bugs.

Answer 77

parasites

Question 78

Redford has proposed that human hunting has ______ the role of keystone species in maintaining diversity in rain forest communities.

Answer 78

undermined

Question 79

In looking at the role of large predators, Terbough found that medium-sized mammals ______ when the predators are absent.

Answer 79

are more abundant

Question 80

Removal of predatory fire ants from corn and squash fields would likely lead to ______ in crop damage from insect pests.

Answer 80

an increase

Question 81

Weaver ants obtain liquids and carbohydrates from ______.

Answer 81

mealy bugs

Question 82

Yang found that the weaver ants function as a keystone species in orange trees by feeding on ______.

Answer 82

larger insects