PCB 3043 Chapter 18 || 100% Actual Answers.
Why do some plant species that are independent at low altitudes become interdependent at high
altitudes?
-Plants are more likely to form communities in the harsh growing conditions of the high
mountains than at low altitudes.
-Species that occupied different habitats at low altitude may need to share one of the few
available habitats at high altitudes.
-Community composition is independent of abiotic factors at low altitudes but becomes
increasingly dependent on abiotic restrictions as altitude increases.
-The benefits the plants provide each other help them survive at high altitudes, although those
benefits are not crucial at low altitudes. correct answers -The benefits the plants provide each
other help them survive at high altitudes, although those benefits are not crucial at low altitudes.
Researchers counted the plant species living in habitats with serpentine and non-serpentine soils,
and in the ecotone between soil types. Their data is reported in the figure.
What are the researchers likely to find when they count the number of animal species found in
the ecotone and in the habitats on either side?
-The ecotone will have the same number of animal species as both of the other habitats.
-The ecotone will have more animal species than either of the other habitats.
-The ecotone will have fewer animal species than habitats with either serpentine or non-
serpentine soils.
-The ecotone will have fewer animal species than habitats with serpentine soils and more species
than habitats with non-serpentine soils. correct answers -The ecotone will have more animal
species than either of the other habitats.
Select the examples that describe community zonation.
-The composition of aquatic species in a lake changes as depth increases.
-Species richness of vertebrates in a stream increases in summer and decreases in winter.
-A mountain lake shore is a distinct boundary between terrestrial and aquatic environments.
-The abundance of a predator species increases during prey mating season.
-Desert vegetation transitions into alpine vegetation as elevation increases. correct answers -The
composition of aquatic species in a lake changes as depth increases.
-Desert vegetation transitions into alpine vegetation as elevation increases.
Why do ecologists consider both species richness and species evenness when they quantify
species diversity in a community?
-The genetic variability of a species and how evenly individuals are spread over the landscape
helps determine community resilience.
-Species richness and evenness help ecologists determine the structure and resilience of
biological communities.
, -As these two measures increase, there tends to be a decrease in the health of the community.
-Species diversity depends on both the number of keystone species and the number of individuals
In those species. correct answers -Species richness and evenness help ecologists determine the
structure and resilience of biological communities.
Identify statements as describing log-normal abundance distributions or rank-abundance curves:
The graphed data of many different communities often result in a bell-shaped curve. correct
answers Log-normal abundance distributions
Identify statements as describing log-normal abundance distributions or rank-abundance curves:
The variable, number of species, is plotted on a logarithmic scale of base two. correct answers
Log-normal abundance distributions
Identify statements as describing log-normal abundance distributions or rank-abundance curves:
This method illustrates that most species have intermediate abundance within a community.
correct answers Log-normal abundance distributions
Identify statements as describing log-normal abundance distributions or rank-abundance curves:
The species in the community are ordered from most abundant to least abundant. correct answers
Rank-abundance curves
Identify statements as describing log-normal abundance distributions or rank-abundance curves:
The plotted data show differences in species richness and evenness between communities.
correct answers Rank-abundance curves
Identify statements as describing log-normal abundance distributions or rank-abundance curves:
The slope of the line shows how relative abundance changes from the most abundant to the least
abundant species. correct answers Rank-abundance curves
Why might an increase in total resources or amount of added resources lead to a decline in
species diversity in a lake?
-The increase in resources, such as nitrogen, is toxic to many species in the lake.
-Primary consumers deplete the algae population and then are eaten by secondary and tertiary
consumers.
-Competitively superior species come to dominate the lake habitat, whereas competitively
inferior species die off.
-The keystone species grow, which changes the ecosystem structure so much that some species
disappear from the lake. correct answers -Competitively superior species come to dominate the
lake habitat, whereas competitively inferior species die off.
Why do some plant species that are independent at low altitudes become interdependent at high
altitudes?
-Plants are more likely to form communities in the harsh growing conditions of the high
mountains than at low altitudes.
-Species that occupied different habitats at low altitude may need to share one of the few
available habitats at high altitudes.
-Community composition is independent of abiotic factors at low altitudes but becomes
increasingly dependent on abiotic restrictions as altitude increases.
-The benefits the plants provide each other help them survive at high altitudes, although those
benefits are not crucial at low altitudes. correct answers -The benefits the plants provide each
other help them survive at high altitudes, although those benefits are not crucial at low altitudes.
Researchers counted the plant species living in habitats with serpentine and non-serpentine soils,
and in the ecotone between soil types. Their data is reported in the figure.
What are the researchers likely to find when they count the number of animal species found in
the ecotone and in the habitats on either side?
-The ecotone will have the same number of animal species as both of the other habitats.
-The ecotone will have more animal species than either of the other habitats.
-The ecotone will have fewer animal species than habitats with either serpentine or non-
serpentine soils.
-The ecotone will have fewer animal species than habitats with serpentine soils and more species
than habitats with non-serpentine soils. correct answers -The ecotone will have more animal
species than either of the other habitats.
Select the examples that describe community zonation.
-The composition of aquatic species in a lake changes as depth increases.
-Species richness of vertebrates in a stream increases in summer and decreases in winter.
-A mountain lake shore is a distinct boundary between terrestrial and aquatic environments.
-The abundance of a predator species increases during prey mating season.
-Desert vegetation transitions into alpine vegetation as elevation increases. correct answers -The
composition of aquatic species in a lake changes as depth increases.
-Desert vegetation transitions into alpine vegetation as elevation increases.
Why do ecologists consider both species richness and species evenness when they quantify
species diversity in a community?
-The genetic variability of a species and how evenly individuals are spread over the landscape
helps determine community resilience.
-Species richness and evenness help ecologists determine the structure and resilience of
biological communities.
, -As these two measures increase, there tends to be a decrease in the health of the community.
-Species diversity depends on both the number of keystone species and the number of individuals
In those species. correct answers -Species richness and evenness help ecologists determine the
structure and resilience of biological communities.
Identify statements as describing log-normal abundance distributions or rank-abundance curves:
The graphed data of many different communities often result in a bell-shaped curve. correct
answers Log-normal abundance distributions
Identify statements as describing log-normal abundance distributions or rank-abundance curves:
The variable, number of species, is plotted on a logarithmic scale of base two. correct answers
Log-normal abundance distributions
Identify statements as describing log-normal abundance distributions or rank-abundance curves:
This method illustrates that most species have intermediate abundance within a community.
correct answers Log-normal abundance distributions
Identify statements as describing log-normal abundance distributions or rank-abundance curves:
The species in the community are ordered from most abundant to least abundant. correct answers
Rank-abundance curves
Identify statements as describing log-normal abundance distributions or rank-abundance curves:
The plotted data show differences in species richness and evenness between communities.
correct answers Rank-abundance curves
Identify statements as describing log-normal abundance distributions or rank-abundance curves:
The slope of the line shows how relative abundance changes from the most abundant to the least
abundant species. correct answers Rank-abundance curves
Why might an increase in total resources or amount of added resources lead to a decline in
species diversity in a lake?
-The increase in resources, such as nitrogen, is toxic to many species in the lake.
-Primary consumers deplete the algae population and then are eaten by secondary and tertiary
consumers.
-Competitively superior species come to dominate the lake habitat, whereas competitively
inferior species die off.
-The keystone species grow, which changes the ecosystem structure so much that some species
disappear from the lake. correct answers -Competitively superior species come to dominate the
lake habitat, whereas competitively inferior species die off.
