Deck 16: Community Structure

Question 1

When an indirect interaction is beneficial to two interacting species, the indirect interaction is termed indirect ________.

Answer 1

mutualism

Question 2

________ index (D)represents the probability that two individuals randomly selected from a sample will belong to the same species.

Answer 2

Simpson's

Question 3

If one community has a more equitable distribution of individuals among species than another community, it is said to have a high level of species ________.

Answer 3

evenness

Question 4

The percentage of individuals in a community that belong to one species is called the relative ________ of that species.

Question 5

The simplest measure of community structure is a count of the number of species present, and is referred to as species ________.

Question 6

A species that has a disproportionate impact on a community, relative to its abundance, is called a(n)________ species.

Question 7

A set of interconnected food chains with linkages representing a wide variety of species interactions is referred to as a food ________.

Question 8

A(n)________ model of community structure assumes that interactions among species have no impact on community structure.

Question 9

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

Question 10

Within a community, a group of species that carry out similar functions or exploit the same resource is called a(n)________.

Question 11

Why is it important to know the species composition along with species richness, when comparing communities?

Question 12

Food webs are useful for depicting ________ interactions among species in which the interaction between two species is mediated by an intermediate species.

Question 13

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 is called ________ predation.

Question 14

The group of species that occupies a given area is called a(n)________.

Question 15

Food ________ are diagrams of communities that depict the trophic relationships among species.

Question 16

When a single or few species are most prevalent in a community, the species are called ________.

Question 17

In a food web diagram, top ________ are species that prey on intermediate and basal species but are not fed upon themselves.

Question 18

In a food web diagram, groups of species that derive food energy from a similar source are called ________ levels.

Question 19

A(n)________ model of community structure assumes that interactions among species have no impact on community structure.

Question 20

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

Question 21

In a forest community, the upper layer is called the ________.

Question 22

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

Question 23

The view developed by H. A. Gleason that communities result from similarities in species' requirements and tolerances for environmental factors is referred to as the ________ concept of communities.

Question 24

In a well-stratified lake during summer, the upper layer of freely circulating water is called the ________.

Question 25

A null model of community structure assumes that the presence and abundance of species within a community is

A)determined mostly by direct species interactions.
B)determined mostly by indirect species interactions.
C)not affected by species interactions.
D)both A and B.

Question 26

Ecologists usually define the species diversity of a community as

A)the number of species in a community.
B)the evenness of relative abundances of the species in a community.
C)a combination of A and B.
D)none of the above.

Question 27

The total number of species present within a community is called

A)species evenness.
B)species diversity.
C)species richness.
D)relative abundance.

Question 28

Interspecific interactions often

A)involve multiple species.
B)involve only two species.
C)have no effect on either species.
D)have no effect on the rest of the community.

Question 29

Variation in environmental conditions within a community, or environmental ________, can have a strong influence on the diversity of a community.

Question 30

In aquatic habitats, the upper zone of water where the availability of light supports photosynthesis by phytoplankton is called the ________ zone.

Question 31

The group of species that occupy a given area, interacting either directly or indirectly, is called a(n)

A)ecosystem.
B)community.
C)population.
D)biome.

Question 32

In a forest community, the site where decomposition occurs and decaying organic matter releases nutrients for reuse by plants is called the forest ________.

Question 33

In aquatic habitats, the bottom zone where decomposition is most active is referred to as the ________ zone.

Question 34

The structure of plant communities along environmental gradients can sometimes be explained by a trade-off between stress tolerance and ________ ability among the plant species.

Question 35

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

Question 36

In a forest community, the layer containing tall shrubs, small trees, and young trees is called the ________.

Question 37

Changes in the physical and biological structure of communities as you move across the landscape are referred to as ________.

Question 38

Which description is true for most communities?

A)All species have approximately equal abundances.
B)All species are rare.
C)All species are common.
D)A few species are common and the remainder are rare.

Question 39

Food webs are useful for depicting ________ interactions among species in which the interaction between two species is mediated by an intermediate species.

Question 40

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

Question 41

Indirect interactions occur when

A)one species is influenced by interactions with many species.
B)one species does not interact with a second species but influences a third species, which interacts directly with the second.
C)a prey species is controlled by a predator species.
D)a predator species is controlled by a prey species.

Question 42

Changes in the physical and biological structure of a community across the landscape are called

A)succession.
B)stratification.
C)zonation.
D)ecotones.

Question 43

A group of species in a community that all exploit the same common resource is called a

A)niche.
B)guild.
C)trophic level.
D)food chain.

Question 44

A diagram that illustrates the flow of energy, linking several species as prey and predators, is referred to as a

A)food web.
B)food chain.
C)trophic level.
D)gene pool.

Question 45

The identification of all the species present within a community is a measure of species

A)composition.
B)diversity.
C)richness.
D)resilience.

Question 46

Which statement best describes a keystone species?

A)a species that takes up a great deal of space in a community
B)an abundant species that may or may not affect other species
C)a rare species that has a strong effect on its community
D)a common species that has a strong effect on its community

Question 47

A diagram that describes the interactions between species within a community, focusing on which species eat which other species, is called a

A)food web.
B)food chain.
C)trophic level.
D)guild.

Question 48

In general, the degree of environmental heterogeneity of a community has a ________ effect on the species diversity of that community.

A)positive
B)negative
C)neutral
D)complicated

Question 49

Defining boundaries between communities is generally

A)not attempted by ecologists.
B)difficult.
C)not difficult due to the variety of methods that have been developed.
D)attempted only as a last resort.

Question 50

The layer of a forest that contains tall shrubs, small trees, and young trees is called the

A)canopy.
B)understory.
C)herb layer.
D)forest floor.

Question 51

Food webs can be arranged into ________ levels based on whether organisms obtain their nutrition from photosynthesis, from eating plants, or from eating animals.

A)niche
B)guild
C)trophic
D)predation

Question 52

(A)________ occurs when predation has a ripple effect on a food web, ultimately affecting primary producers.

A)Connectance
B)trophic cascade
C)trophic collapse
D)Niche packing

Question 53

When populations at a given trophic level are controlled by populations in the trophic level above them, they are said to be under

A)top-down control.
B)indirect control.
C)bottom-up control.
D)functional control.

Question 54

In a well-stratified lake in summer, the second layer of water, characterized by a steep and rapid decline in temperature with depth, is called the

A)epilimnion.
B)metalimnion.
C)hypolimnion.
D)benthic zone.

Question 55

In a forest community, the layer in which most photosynthesis occurs is the

A)canopy.
B)midstory.
C)understory.
D)forest floor.

Question 56

Hubbell's unified neutral theory proposes that ________ drives community diversity.

A)population dynamics
B)stochastic forces
C)ecological drift
D)niche packing

Question 57

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 58

In a well-stratified lake in summer, the bottom zone, in which decomposition is most active, is called the ________ zone.

A)photic
B)benthic
C)aphotic
D)hypolimnion

Question 59

To which category or trophic level does a typical plant belong?

A)basal species
B)intermediate species
C)decomposer
D)top predator

Question 60

The two major determinants of regional and global patterns of vegetation distribution include

A)soil and temperature.
B)soil and moisture.
C)temperature and moisture.
D)temperature and animal communities.

Question 61

Most communities have a few common species and many rare species.

Question 62

All the hummingbirds and other nectar-feeding birds in a community could be considered a guild.

Question 63

Basal species in a food web do not feed on other species.

Question 64

Dominance is the converse or opposite of diversity.

Question 65

A community refers to the group of species that occupy a given area, interacting either directly or indirectly.

Question 66

The species diversity of a community is defined by both the number of species and the evenness of the species' relative abundances.

Question 67

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

Question 68

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

Question 69

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

Question 70

The physical structure of terrestrial communities is usually defined more by the plants than the animals present.

Question 71

Species interactions within a community rarely involve only two species.

Question 72

Competitive interactions are often diffuse while mutualisms are not.

Question 73

The ________ concept suggests that, if a cluster of species repeatedly co-exist, they function as an integrated unit within the community.

A)unified
B)organismal
C)individualistic, or continuum
D)successional

Question 74

A species that has a disproportionate effect on other species in its community relative to its abundance is referred to as a keystone species.

Question 75

Keystone predators have strong indirect effects on inferior competitors.

Question 76

A null model for the impact of species interactions on communities assumes that species interactions have strong influences on community structure.

Question 77

In a food web, the average number of feeding links per species, or linkage ________, provides one measure of community complexity.

A)richness
B)diversity
C)density
D)number

Question 78

In its simplest form, apparent competition involves two predators and one prey species.

Question 79

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

Question 80

The "world is green" hypothesis of Hairston et al. suggests that predators keep herbivore populations in check.