Chapter 18 - STRUCTURE OF COMMUNITIES

Question 1

The ________ is a group of plant and animal species that inhabits a given area.

Answer 1

community

Question 2

A(n) ________ model of community structure assumes that the presence and absence of individual species in a community result from independent responses to the physical environment, and interactions among species have no impact on community structure

Answer 2

null

Question 3

When interspecific interactions involve more than just two species, they are said to be ________.

Answer 3

diffuse

Question 4

________ predation is a type of indirect interaction in which a predator enhances the success of one or more inferior competitors by reducing the abundance of a superior competitor.

Answer 4

Keystone

Question 5

________ competition is a type of indirect interaction that occurs when a single species of predator feeds on two prey species

Answer 5

Apparent

Question 6

When an indirect interaction is beneficial to one of two interacting species and neutral to the other, the indirect interaction is termed indirect ________

Answer 6

commensalism

Question 7

________ or functional groups are groups of species in a community that are thought to have similar roles in the community

Answer 7

Guilds

Question 8

When prey populations are controlled by predators in a trophic level above them, they are saidto be under ________ control.

Answer 8

top-down

Question 9

Patterns of temperature and ________ resulting from regional variations in climate are the major determinant of regional and global patterns of vegetation distribution.

Answer 9

moisture

Question 10

Variation in environmental conditions within a community is referred to as environmental ________.

Answer 10

Heterogeneity

Question 11

In all experimental studies to date, the effect of increasing nutrient availability to plants has been to ________ plant diversity.

Answer 11

decrease

Question 12

________ describes the number of trophic links in a food we

Answer 12

connectance

Question 13

Considerable evidence indicates that the null model of community structure is incorrect because
A) each species responds independently of other species to the prevailing physical environment.
B) interactions among species have no significant influence on community structure.
C) when one species is removed, the populations of the other species are unaffected.
D) species interactions modify the fundamental niche of the species involved, influencing their relative abundance and, in some cases, their distribution.

Answer 13

D) species interactions modify the fundamental niche of the species involved, influencing their relative abundance and, in some cases, their distribution.

Question 14

Experiments on competition among species within a community reveal that
A) removing a single species or a group of species has relatively little effect on a community.
B) removing a single species has a stronger effect than removing a group of species from a community.
C) removing a group of species has a stronger effect than removing a single species from a community

Answer 14

C) removing a group of species has a stronger effect than removing a single species from a community

Question 14

Experiments on competition among species within a community reveal that
A) removing a single species or a group of species has relatively little effect on a community.
B) removing a single species has a stronger effect than removing a group of species from a community.
C) removing a group of species has a stronger effect than removing a single species from a community

Answer 14

C) removing a group of species has a stronger effect than removing a single species from a community

Question 15

3) When apparent competition occurs, the
A) populations of predator and prey species are smaller.
B) population of the predator species is larger and the populations of the prey species are smaller.
C) population of the predator species is smaller and the populations of the prey species are larger.
D) populations of predator and prey species are larger.

Answer 15

B) population of the predator species is larger and the populations of the prey species are smaller.

Question 16

Food webs are typically arranged into trophic levels with
A) primary producers at the bottom, herbivores in the middle, and carnivores at the top.
B) herbivores at the bottom, carnivores in the middle, and primary producers at the top.
C) carnivores at the bottom, herbivores in the middle, and primary producers at the top.
D) primary producers at the bottom, carnivores in the middle, and herbivores at the top

Answer 16

A) primary producers at the bottom, herbivores in the middle, and carnivores at the top.

Question 17

5) When top-down control occurs within an intertidal zone along the rocky coastline of the Pacific Ocean, which of the following species controls the abundance of other species?
A) kelp
B) mussels
C) barnacles
D) starfish

Answer 17

D) starfish

Question 18

6) Plant community structure along an environmental gradient can often be explained by
A) differences among species in their competitive abilities.
B) differences among species in their abilities to tolerate stress.
C) differences among species in their resistance to herbivores.
D) a trade-off among species with respect to competitive ability and stress tolerance.

Answer 18

D) a trade-off among species with respect to competitive ability and stress tolerance.

Question 19

In aquatic environments, the three major environmental gradients of water that directly influence the distribution and dynamics of communities include
A) temperature, depth, and oxygen content.
B) depth, flow rate, and salinity.
C) pressure, temperature, and depth.
D) flow rate, salinity, and oxygen content

Answer 19

B) depth, flow rate, and salinity.

Question 20

As the degree of environmental heterogeneity of a community increases, the number of plant and animal species tends to
A) decrease.
B) remain the same.
C) increase.
D) increase initially and then decrease

Answer 20

C) increase.

Question 21

9) As the fertility of soil on the forest floor increases, the
A) growth rate of plants increases.
B) size of plants decreases.
C) density of plants decreases.
D) number of species of plants increases

Answer 21

A) growth rate of plants increases.

Question 22

In a food web, community complexity may be measured by the average number of feeding links per species, also referred to as
A) trophic diversity.
B) food web diversity.
C) linkage density.
D) interconnectedness.

Answer 22

C) linkage density.

Question 23

1) Environmental conditions often vary spatially but do not tend to change over time in a given place

Answer 23

False

Question 24

There is considerable evidence that community structure is influenced by interactions between species.

Answer 24

True

Question 25

Species interactions within a community rarely involve only two species.

Answer 25

True

Question 26

Diffuse interactions often occur among competing species but never among predator-prey species

Answer 26

False

Question 27

Competitive interactions are often diffuse, whereas mutualisms are not.

Answer 27

false

Question 28

The populations of keystone predators are controlled by the populations of their prey species.

Answer 28

False

Question 29

Indirect interactions can be either positive or negative for the affected species

Answer 29

True

Question 30

The removal of a single species from a community can have unpredictable consequences.

Answer 30

True

Question 31

The control of an herbivore population by a parasitoid is an example of top-down control.

Answer 31

True

Question 32

The “world is green” hypothesis suggests that herbivore populations limit the number of predators, allowing plant biomass to accumulate.

Answer 32

False

Question 33

Within a community, most species have a similar range of environmental tolerances

Answer 33

False

Question 34

Competition among plant species rarely involves only a single resource.

Answer 34

True

Question 35

Environmental heterogeneity tends to be positively correlated with species diversity

Answer 35

True

Question 36

The diversity of an animal community is unrelated to the physical structure of a plant community.

Answer 36

False

Question 37

Competition for belowground resources is considered to be asymmetric because larger plantshave a disproportionate advantage in competition for those resources.

Answer 37

false

Question 38

In aquatic communities, an increase in nutrients usually causes the number of autotrophic species to increase

Answer 38

True

Question 39

Recent studies suggest that as species richness in a food web increases, the number of trophiclinks increases but the connectance decreases.

Answer 39

true

Question 40

The research of Sally Hacker has demonstrated that Juncus plants are strong antagonists, causing increases in conditions such as salinity that hinder the growth of other plants such as Iva.

Answer 40

False