Deck 18: Factors Influencing the Structure of Communities

Question 1

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

Answer 1

moisture

Question 2

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

Answer 2

decrease

Question 3

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 3

D

Question 4

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

Question 5

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

Question 6

________ describes the number of trophic links in a food web.

Question 7

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.

Question 8

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

Question 9

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

Question 10

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.

Question 11

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.

Question 12

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.

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.

Question 14

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

Question 15

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.

Question 16

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.

Question 17

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.

Question 18

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

Question 19

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

Question 20

________ 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.

Question 21

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

Question 22

Competitive interactions are often diffuse,whereas mutualisms are not.

Question 23

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

Question 24

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

Question 25

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

Question 26

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

Question 27

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.

Question 28

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

Question 29

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

Question 30

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

Question 31

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.

Question 32

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

Question 33

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

Question 34

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

Question 35

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

Question 36

Environmental heterogeneity tends to be positively correlated with species diversity.

Question 37

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.

Question 38

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

Question 39

Species interactions within a community rarely involve only two species.

Question 40

Competition among plant species rarely involves only a single resource.