Chapter 15
1. A mutualistic relationship in which either species can survive without its partner is
called a ______________ mutualism.
Answer: facultative
2. Which of the following organisms are dependent on mutualisms for their persistence?
a) reef-building corals
b) bioluminescent fishes
c) bumblebees and hummingbirds
d) horses, elephants, and camels
e) all of the above
Answer: E
3. The two most common types of mycorrhizal fungi are ___________ and
____________.
Answer: arbuscular mycorrhizal fungi and ectomycorrhizae
4. Mycorrhizal fungi (directly) help their plant partners acquire
a) sugars.
b) sunlight.
c) seed dispersal.
d) soil nutrients.
e) pollination.
Answer: D
5. Mycorrhizal fungi acquire _________ from their plant partners.
a) sugars
b) soil nutrients
c) proteins and lipids
d) growth hormones
e) protection from consumers
Answer: A
6. Soil fertilization should favor mycorrhizal fungi that are
a) less aggressive at obtaining sugars from their plant hosts
b) more aggressive at obtaining sugars from their plant hosts
c) more efficient at extracting inorganic nutrients from soils
d) more efficient at extracting sugars from soils
e) more efficient at extracting inorganic nutrients from plant root exudates
Answer: B
7. In experiments with the prairie grass Andropogon, root:shoot ratios proved to be
a) higher in plants grown in poor soils.
b) lower in plants grown in poor soils.
c) equal in plants grown in poor and rich soils.
d) higher in plants grown with mycorrhizae.
e) equal in plants grown with and without mycorrhizae.
Answer: A
8. Modified leaflet tips of bullshorn acacia that provide a food source for ants are called
___________.
Answer: Beltian bodies
9. Ant-acacia trees provide several services to their mutualistic ant partners. These
include
a) enlarged thorns to host ant colonies.
b) nectar from foliar nectaries.
c) nectar from floral nectaries.
d) all of the above
e) Both enlarged thorns to host ant colonies and nectar from foliar nectaries.
Answer: D
10. The presence of ant mutualists on bullshorn acacia reduces herbivore attack and
increases acacia growth rate, but has little effect on acacia mortality rate
Answer: F
11. Ants on the aspen sunflower, Helianthella quinquenervis, obtain sugars and amino
acids by
a) collecting nectar from the sunflower’s flowers.
b) collecting nectar from extrafloral nectaries.
c) tending aphids that extract plant sap.
d) extracting plant sap directly by piercing the sunflower stem.
e) all of the above
Answer: B
12. The major benefit obtained by aspen sunflower, Helianthella quinquenervis, from its
ant mutualists is
a) improved attraction of pollinators.
b) reduced loss of leaf tissue to herbivorous insects.
c) more efficient extraction of soil nutrients.
d) more rapid growth early in the growing season.
e) reduced losses of seed to seed predators.
Answer: E
13. The photosynthetic zooxanthellae associated with reef-building corals are members of
the Phylum ___________.
Answer: Dinoflagellata
14. Which aspects of the biology of zooxanthellae are controlled by their coral hosts?
a) their cell wall chemistry
b) their population growth rate when free-living
c) the release of photosynthetic products from their cells
d) the rate at which they absorb sugars from their hosts
e) their mortality rate
Answer: C
15. The major benefit obtained by zooxanthellae algal cells from their coral host is
a) protection from herbivores.
b) sugars.
c) phosphorus from coral wastes.
d) nitrogen from coral wastes.
e) temperature regulation.
Answer: D
16. Crabs and shrimp associated with corals protect their hosts from
a) being dislodged from the substrate by currents.
b) predation by sea-stars.
c) predation by fishes.
d) attack by parasitic nematodes.
e) infection by pathogenic bacteria.
Answer: B
17. A calculated range of values that we estimate contains the true mean of a population
with a known degree of certainty is called a
a) standard error.
b) standard deviation.
c) median.
d) Students t-value.
e) confidence interval.
Answer: E
18. The “unsuccessful mutualists” in Kathleen Keeler’s cost-benefit model of mutualism
are those that
a) give benefits to their partner, but fail to receive benefits in return.
b) receive benefits from their partner, but fail to provide benefits in return.
c) neither give benefits to their partner, nor receive them in return.
d) fail to locate individuals of their mutualistic partner effectively.
e) locate mutualistic partners, but fail to overcome their defenses against colonization.
Answer: A
19. In Kathleen Keeler’s cost-benefit model of mutualism, the condition for persistence
of mutualists is pwmw + qwmu > wnm. The parameters p and q represent the
a) cost and benefit of the mutualism.
b) fitness of successful and unsuccessful mutualists.
c) proportion of successful and unsuccessful mutualists in the population.
d) frequency of “mutualist” and “nonmutualist” alleles in the population.
e) amount of herbivore protection provided by ant and non-ant defenses.
Answer: C
20. A cost-benefit model predicts that aspen sunflowers (Helianthella quinquenervis) in
shady habitats should be less likely to attract ants than those living in sunny habitats.
Answer: T
21. The interaction between honeyguide birds and the Boran people of Kenya
a) is an obligate mutualism.
b) is a facultative mutualism.
c) is exploitative, with humans benefiting but honeyguides exploited.
d) represents the only way a honeyguide can gain access to a beehive.
e) depends only on humans following birds, not on active communication by the birds.
Answer: B