Chapter 20

Question 1

There are 22 species of snakes in Canada and 126 species in the United States. Approximately
how many do you think there are in Mexico?
A) 0 B) 3 C) 30 D) 300

Answer 1

D) 300

Question 2

In the early part of the twentieth century, which of the following two views about the
determination of diversity was more popular?
A) Diversity increases without limit over time.
B) Diversity reaches an equilibrium level, with factors adding species balanced by factors
removing species.

Answer 2

A) Diversity increases without limit over time.

Question 3

The biological diversity encountered increases as one moves from the poles to the tropics.
Within a particular latitude, diversity also varies:
A) between different continents
B) between different habitats
C) as a function of temperature and precipitation
D) as a function of topographic complexity
E) all of the above

Answer 3

E) all of the above

Question 4

When one tallies the species in a community by numbers of individuals, one typically finds that:
A) all species have about the same number of individuals.
B) most species are dominant, whereas a few others are represented by relatively few
individuals.
C) a few species are dominant, whereas most others are represented by relatively few
individuals.
D) there is no general pattern in the relative abundances of species.

Answer 4

C) a few species are dominant, whereas most others are represented by relatively few
individuals.

Question 5

What do Margalef’s and Menhinick’s indices have in common?
A) Both indices are measures of heterogeneity.
B) Both indices normalize species richness in relation to the size of the sample.
C) Both indices normalize species richness in relation to latitude.
Chapter 20: Biodiversity
2
D) Both indices quantify the compositional similarity of two samples.
E) Both indices were used by Darwin, Bates, and Wallace to quantify tropical diversity.

Answer 5

B) Both indices normalize species richness in relation to the size of the sample.

Question 6

Heterogeneity measures, like Simpson’s index, take into account:
A) number of species (richness).
B) relative abundance of species (evenness).
C) both A and B.

Answer 6

C) both A and B.

Question 7

Who first proposed a species‐area relationship of the form S = cAz?
A) Arrhenius
B) Bates
C) Darwin
D) Müller
E) Wallace

Answer 7

A) Arrhenius

Question 8

Analyses of species‐area relationships for many groups of organisms have revealed that values
of z in the equation S = cAz tend to be close to __________.
A) 0.03 B) 0.3 C) 3 D) 30

Answer 8

B) 0.3

Question 9

Which of the following explanations of the species‐area relationship would be anticipated at
the smallest, local scales?
A) The number of species increases with area because larger areas contain a greater number
of individuals.
B) The number of species increases with area because larger areas have more habitats.
C) The number of species increases with area because larger areas support distinct
evolutionary lineages.

Answer 9

A) The number of species increases with area because larger areas contain a greater number
of individuals.

Question 10

Which of the following explanations of the species‐area relationship would be anticipated at
the largest, global scales?
A) The number of species increases with area because larger areas contain a greater number
of individuals.
B) The number of species increases with area because larger areas have more habitats.
C) The number of species increases with area because larger areas support distinct
evolutionary lineages.

Answer 10

C) The number of species increases with area because larger areas support distinct
evolutionary lineages.

Question 11

You construct two species‐area relationships for terrestrial plants, modeling both with the
relationship log S = log c + z log A. One relationship is for data collected from islands of different
sizes. The other is for data collected from continental areas over a similar size range. Which of
these relationships is likely to have the greater slope, z?
A) the one for islands
B) the one for continental areas
C) neither A nor B

Answer 11

A) the one for islands

Question 12

The number of species belonging to a particular group of animals (such as birds, bats, or lizards)
may increase with greater island size because larger islands have greater habitat diversity.
A) True B) False

Answer 12

B) False

Question 13

An apparent departure from the rule that species diversity increases toward lower latitudes is
the decrease in species of mammals as one moves southward on the peninsula of Baja
California. What factor might account for this southward decline?
A) increased intensity of competition
B) increased intensity of predation
C) increased dispersal distance from the continental source of species

Answer 13

C) increased dispersal distance from the continental source of species

Question 14

When Robert and John MacArthur investigated the determinants of species diversity for birds,
they developed an index of foliage height diversity as a predictive variable. In so doing, which of
the following determinants of diversity did they identify as important?
A) productivity
B) structural complexity
C) climate
D) latitude

Answer 14

B) structural complexity

Question 15

When Hawkins and others surveyed the literature for evidence that solar energy input and/or
precipitation input predict species diversity, they found that energy input was correlated with
species diversity in only one of the following regions. Which was it?
A) north‐temperate region
B) the tropics
C) south‐temperate region
D) all of the above

Answer 15

A) north‐temperate region

Question 16

Potential evapotranspiration (PET) for a particular location is:
A) total annual precipitation
B) total annual precipitation minus actual evapotranspiration
C) total amount of water that could be evaporated from the soil and transpired by plants
D) total amount of water that is actually evaporated from the soil and transpired by plants

Answer 16

C) total amount of water that could be evaporated from the soil and transpired by plants

Question 17

Which of the following has been proposed as an explanation for the relationship between
energy input and diversity (the energy‐diversity hypothesis)?
A) A larger amount of energy in an ecosystem can be shared by a larger number of species.
B) Greater energy input and the resulting higher biological productivity might also support
larger population sizes.
C) High energy input might accelerate rates of evolutionary change and thus increase the rate
of species formation.
D) all of the above

Answer 17

D) all of the above

Question 18

From the perspective of diversity, within a region, distributions of species should reflect:
A) distribution of suitable habitats.
B) ability to disperse to a particular locality.
C) both A and B
D) neither A nor B

Answer 18

A) distribution of suitable habitats.

Question 19

As beta diversity increases, one should generally expect to find the species composition of
different habitats:
A) becoming more similar. B) becoming more different. C) staying about the same.

Answer 19

B) becoming more different.

Question 20

Beta diversity, or turnover, would be at its minimum if all species occurred in all habitats within
a region. Beta diversity would be at its maximum if each habitat had a unique biota, and
regional diversity would equal:
A) the mean of the local diversities of all the habitats within the region.
B) the sum of the local diversities of all the habitats within the region.
C) the largest among the local diversities of all the habitats within the region.
D) the smallest among the local diversities of all the habitats within the region.

Answer 20

B) the sum of the local diversities of all the habitats within the region.

Question 21

In North America, how does beta diversity of plants (from east to west) change as one moves
from south to north?
A) It increases.
B) It remains constant.
C) It decreases.
D) It exhibits no consistent pattern.

Answer 21

C) It decreases.

Question 22

Primarily because of its greater topographic complexity, eastern Asia exhibits a __________
turnover in compositional similarity of floras with distance, relative to North America.
A) greater
B) similar
C) lower

Answer 22

A) greater

Question 23

In Patagonia, researchers found that the middle part of the intertidal zone was comprised of
__________, in both exposed and protected sites.
A) bare rock
B) mussels
C) coralline algae
D) a 50:50 mix of mussels and coralline algae

Answer 23

B) mussels

Question 24

Species present in the regional species pool are sorted into local communities based on their
adaptations (to conditions of the environment and to finding suitable resources) and
interactions with other species. The result is often that the __________ niche represents a
restricted subset of ranges and conditions represented in the __________ niche.
A) fundamental, realized
B) realized, fundamental

Answer 24

B) realized, fundamental

Question 25

How could the number of coexisting species within a community be increased?
A) increased total niche space (variety of resources)
B) increased niche overlap
C) increased specialization
D) A, B, C, or any combination of these

Answer 25

D) A, B, C, or any combination of these

Question 26

Increased species diversity among many species groups in the tropics (as compared to higher
latitude regions) appears to be the result of a greater variety of ecological resources.
A) True B) False

Answer 26

A) True

Question 27

Morphological analyses of species in various communities have revealed that the average size
of species’ niches is independent of community diversity.
A) True B) False

Answer 27

A) True

Question 28

Bats in Cameroon, tropical West Africa, play a greater diversity of ecological roles than do bats
in Ontario, Canada. Fish in the mouth of a Mexican river system play a greater diversity of
ecological roles than do fish in the headwaters of the same river system. Both of these
observations are supportive of which of the following hypotheses?
A) Species diversity is positively correlated with niche diversity.
B) Species diversity is negatively correlated with niche diversity.
C) Species diversity shows no direct relationship with niche diversity.

Answer 28

A) Species diversity is positively correlated with niche diversity.

Question 29

Equilibrium theories of species diversity have been applied to islands and to larger, continental
regions. Which of the following processes is likely to play a greater role in the determination of
equilibrium diversity in a continental region?
A) extinction of species C) formation of new species
B) immigration of species from elsewhere

Answer 29

C) formation of new species

Question 30

In the equilibrium theory of island biogeography, variation in numbers of species on islands of
different sizes is seen as a function of differences in:
A) immigration rates. B) extinction rates. C) neither of the above.

Answer 30

B) extinction rates.

Question 31

In the equilibrium theory of island biogeography, variation in numbers of species on islands of
different distances from the mainland is seen as a function of differences in:
A) immigration rates. B) extinction rates. C) neither of the above.

Answer 31

A) immigration rates

Question 32

Simberloff and Wilson conducted a well‐known experiment in which they fumigated small
mangrove islands and observed the recovery through time of arthropod communities on these
islands. They found that mangrove islands tended to recover to about the same number of
species present pre‐fumigation. Which proposition of the equilibrium theory of island
biogeography did this observation support?
A) Islands distant from the mainland have fewer species than islands close to the mainland.
B) Small islands have fewer species than large islands.
C) Each island has an equilibrium number of species.

Answer 32

C) Each island has an equilibrium number of species

Question 33

Consider the model for the equilibrium number of species in a mainland (continental) region, as
illustrated in Figure 20.23. What does this model say about the rate of speciation?
A) The rate of speciation decreases as a linear function of the number of species.
B) The rate of speciation increases as a linear function of the number of species.
C) The rate of speciation increases as a function of the number of species, but the rate of
increase decelerates as the number of species becomes large.

Answer 33

C) The rate of speciation increases as a function of the number of species, but the rate of
increase decelerates as the number of species becomes large.

Question 34

Which of the following alternatives would lead to an interpretation of the relationship of
speciation to number of species present different from the one depicted in Figure 20.23?
A) Opportunities for further diversification are restricted by increasing diversity.
B) Opportunities for further diversification are enhanced by increasing diversity.

Answer 34

B) Opportunities for further diversification are enhanced by increasing diversity.

Question 35

Consider the model for equilibrium number of species in a mainland (continental) region, as
illustrated in Figure 20.23. What does this model say about the rate of extinction?
A) The rate of extinction decreases as a linear function of the number of species.
B) The rate of extinction increases as a linear function of the number of species.
C) The rate of extinction increases as a function of the number of species, but the rate of
increase accelerates as the number of species becomes large.

Answer 35

C) The rate of extinction increases as a function of the number of species, but the rate of
increase accelerates as the number of species becomes large.

Question 36

Which of the following alternatives would lead to an interpretation of the relationship of
extinction to number of species present different from the one depicted in Figure 20.23?
A) The probability of extinction per species increases with increasing diversity as competitive
exclusion becomes more likely.
B) The probability of extinction per species decreases with increasing diversity as mutualistic
relationships buffer processes that lead to extinction.

Answer 36

B) The probability of extinction per species decreases with increasing diversity as mutualistic
relationships buffer processes that lead to extinction.

Question 37

Among explanations for tropical diversity, why does the discussion focus heavily on factors that
might be responsible for diversity in tropical plant communities?
A) Most tropical biologists study plants, not animals.
B) Animals play insignificant roles in tropical ecosystems.
C) The diversity of animals is linked closely to the diversity of plants, so an understanding of
plant diversity helps us to understand the diversity of animals as well.
D) Flowering plants dominate most tropical ecosystems, and flowering plants have been on
earth much longer than animals.

Answer 37

C) The diversity of animals is linked closely to the diversity of plants, so an understanding of
plant diversity helps us to understand the diversity of animals as well.

Question 38

Some ecologists have proposed that environmental heterogeneity in the tropics leads to
greater diversity of trees. Which of the following assumptions underlying this concept seem(s)
unlikely?
A) Tropical plants recognize much finer habitat differences in the tropics than they do in
temperate regions.
B) There is more environmental heterogeneity in the tropics than in temperate regions.
C) Both of the above.

Answer 38

C) Both of the above.

Question 39

Some ecologists have proposed that gaps created by disturbances lead to habitat
heterogeneity, which, in turn, leads to the coexistence of greater numbers of tree species in
tropical habitats, as compared to temperate habitats. Which of the following hypotheses is
most closely associated with this proposal?
A) Red Queen hypothesis D) intermediate disturbance hypothesis
B) character displacement hypothesis E) energy‐diversity hypothesis
C) Hamilton‐Zuk hypothesis

Answer 39

D) intermediate disturbance hypothesis

Question 40

Careful, long‐term studies conducted by Steve Hubbell and colleagues __________ for the
proposal that spatial and temporal variation in gap formation caused by disturbance explains
high diversity of tropical trees.
A) provide support B) fail to provide support

Answer 40

B) fail to provide support

Question 41

Steve Hubbell’s work at Barro Colorado Island, Panama, points to which of the following as an
impediment to the colonization of gaps by tree species?
A) lack of species capable of surviving in gaps
B) competitive displacement
C) dispersal limitation
D) predation

Answer 41

C) dispersal limitation

Question 42

Daniel Janzen of the University of Pennsylvania has emphasized which of the following
processes in his explanation of high species richness in tropical systems?
A) herbivory B) mutualism C) allelopathy D) intraspecific competition

Answer 42

A) herbivory

Question 43

Is there any evidence to support the idea that differential pest pressure can account for
differences in diversity of tree species between tropical and temperate regions?
A) Yes B) No

Answer 43

B) No

Question 44

In a synthesis of several ideas, Steve Hubbell has proposed that reduced competitive exclusion
in tropical ecosystems can lead to the accumulation of large numbers of species in the tropics.
What other components are part of this synthesis?
A) operation of processes such as pest pressure and recruitment limitation
B) regional production of species
C) reduced susceptibility of species to extinction
D) all of the above

Answer 44

D) all of the above

Question 45

In his comprehensive theory, Steve Hubbell assumes that all species are competitively
equivalent and that they have identical fitnesses— their probabilities of death and reproduction
Chapter 20: Biodiversity
10
are the same. How do we characterize such species (and, indeed, Hubbell’s theory)?
A) polarized
B) neutral
C) niche‐differentiated
D) complementary

Answer 45

B) neutral

Question 46

In Hubbell’s comprehensive theory, species richness is a function of region size, the rate of
species formation, and the rate of migration. This theory successfully predicts:
A) species richness
B) species abundance distributions
C) species‐area relationships
D) beta diversity
E) all of the above

Answer 46

E) all of the above

Question 47

According to Dr. Ricklefs, a problem with Hubbell’s comprehensive model is that:
A) migration is unlikely.
B) speciation is unlikely.
C) extinction is unlikely.
D) random ecological drift is too slow a process.

Answer 47

D) random ecological drift is too slow a process

Question 48

Although we may not fully understand the causes of high species diversity in the tropics, several
lines of evidence support the idea that diversity is self‐accelerating, that is, that diversity begets
diversity.
A) True B) False

Answer 48

A) True

Question 49

The species that occur within a region are referred to as its __________.

Answer 49

species pool

Question 50

The __________ of a species takes into account the range of conditions and resources within
which individuals of the species can persist.

Answer 50

fundamental niche

Question 51

Other species may restrict the distribution of a given species to parts of its fundamental niche
where it is more successful; this subset of the fundamental niche is called the __________.

Answer 51

realized niche

Question 52

If the optimum conditions for a set of competing species are arranged uniformly along a niche
axis representing an essential resource, increasing the niche breadths of all species would lead
to increased niche __________.

Answer 52

overlap

Question 53

Reduced niche breadth is a manifestation of increased __________.

Answer 53

specialization

Question 54

In the equilibrium theory of island biogeography, as more species accumulate on an island, the
rate of extinction increases and the rate of __________ decreases.

Answer 54

immigration

Question 55

Rubber plantations have failed repeatedly in the Amazon basin, where the rubber tree is native,
but such plantations have been successful in Malaysia, where specialist herbivores are not
present. This observation has provided support for the __________ hypothesis for higher
diversity in the tropics.

Answer 55

pest pressure

Question 56

According to Robert Whittaker’s model, regional diversity equals local diversity times
__________.

Answer 56

beta diversity

Question 57

A __________ species is likely to use a substantial portion of resources available within a
community and to have substantial effects on other species because of its abundance.

Answer 57

dominant

Question 58

The botanist Olaf Arrhenius first formalized the __________ relationship, which links increasing
numbers of species encountered with increasing area inventoried.

Answer 58

species‐area

Question 59

Diversity indices that measure heterogeneity, such as Simpson’s index, weight the contribution
of each species by its __________ abundance.

Answer 59

relative

Question 60

In a comparison of islands and neighboring continental regions with similar climate and range
of habitats, one finds fewer species on islands. However, these island species often have
greater densities and expand into habitats that would be filled by other species on the
mainland, in an example of __________.

Answer 60

ecological release

Question 61

The formula C/[(S1 + S2)/2] is used to compute __________ similarity.

Answer 61

Sørensen

Question 62

The process whereby species from the regional species pool combine to form local
communities is referred to as __________.

Answer 62

species sorting

Question 63

With a moderate level of disturbance, more species can coexist because the community
becomes a mosaic of habitat patches at different stages of succession. The preceding is a
statement of the __________ disturbance hypothesis.

Answer 63

intermediate