54) Aside from the density of dinoflagellates in P. ianthina skin, how many of the following factors can
affect whether or not the endosymbiotic dinoflagellates promote the sea slug’s survival (assuming
latitudes above or below Earth’s equator)?
1. day length
2. height of sun above the horizon
3. cloud cover
4. depth at which P. ianthina lives
5. water clarity
A) two of these
B) three of these
C) four of these
D) five of these
55) If the dinoflagellate-containing sea slug, P. ianthina, otherwise preys on coral animals, then it would
be least surprising to find that
A) P. ianthina has no tolerance to the toxin in the nematocysts of its prey.
B) P. ianthina can locate its coral prey by chemicals released into the water by corals.
C) The coral prey harbor dinoflagellates in their tissues.
D) The coral prey transform themselves into medusas to flee from approaching P. ianthina.
56) The sea slug, Elysia chorotica, has no nematocysts or dinoflagellates but, rather, has “naked”
chloroplasts in its skin. The chloroplasts are all that remain of the seaweed (Vaucheria sp.) that Elysia
feeds upon. The chloroplasts are transferred to the skin; consequently, this slug is green. It spends most
of its time basking in shallow water on the surface of seaweeds. How should we expect its chloroplasts
to benefit the Elysia sea slug?
1. provide Elysia with fixed CO2
2. provide Elysia with fixed N2
3. provide Elysia with protective coloration
A) 1 only
B) 2 only
C) 3 only
D) 1 and 3
E) 1, 2, and 3
Scenario Questions
The sea slug, Pteraeolidia ianthina, can harbor living dinoflagellates (photosynthetic protists) in its skin.
These endosymbiotic dinoflagellates reproduce quickly enough to maintain their populations. Low
populations do not affect the sea slugs very much, but high populations (> 5 x 105 cells/mg of sea slug
protein) can promote sea slug survival.
57) If 100,000 sea slug cells together contain 1.0 mg of protein, then what is the minimum number of
dinoflagellates per sea slug cell that constitutes a “high,” and therefore beneficial, population?
A) 1 cell
B) 5 cells
C) 10 cells
D) 50 cells
E) 100 cells
Nudibranchs, a type of predatory sea slug, can have various protuberances (i.e., extensions) on their
dorsal surfaces. Rhinophores are paired structures, located close to the head, which bear many
chemoreceptors. Dorsal plummules, usually located posteriorly, perform respiratory gas exchange.
Cerata usually cover much of the dorsal surface and contain nematocysts at their tips.
58) The claws on the foremost trunk segment of centipedes have a function most similar to that of
A) rhinophores.
B) dorsal plummules.
C) cerata.
D) more than one of these.
59) The feet of certain insects, notably of female butterflies, have a function most similar to that of
A) rhinophores.
B) dorsal plummules.
C) cerata.
D) more than one of these.
60) The stingers of honeybees have a function most similar to that of
A) rhinophores.
B) dorsal plummules.
C) cerata.
D) more than one of these.
61) The spiracles and tracheae of insects have a function most similar to that of
A) rhinophores.
B) dorsal plummules.
C) cerata.
D) more than one of these.
62) The antennae of insects have a function most similar to that of
A) rhinophores.
B) dorsal plummules.
C) cerata.
D) more than one of these.
63) The lateral flaps of planaria heads have a function most similar to that of
A) rhinophores.
B) dorsal plummules.
C) cerata.
D) more than one of these.
64) The parapodia of polychaetes have a function most similar to that of
A) rhinophores.
B) dorsal plummules.
C) cerata.
D) more than one of these.
65) The spines of sea stars have a function most similar to that of
A) rhinophores.
B) dorsal plummules.
C) cerata.
D) more than one of these.
66) The small, thin extensions of the skin on the aboral surfaces of sea stars have a function most similar
to that of
A) rhinophores.
B) dorsal plummules.
C) cerata.
D) more than one of these.
67) If nudibranch rhinophores are located at the anteriors of these sea slugs, then they contribute to the
sea slugs’
A) segmentation.
B) lack of torsion.
C) cephalization.
D) identity as lophotrochozoans.
E) ability to successfully carry out a sessile lifestyle.
68) Nudibranchs usually have two rhinophores. However, if they had a single rhinophore, it could still
carry out the function of two rhinophores, and with similar effectiveness, if this single rhinophore
A) had two branches, one directed to the left, the other to the right.
B) had two branches, one directed toward the head, the other directed toward the tail.
C) was as long as two rhinophores placed end to end.
D) had cilia whose power strokes directed water away from the surface of the slug.
E) was located within the mantle cavity.
69) The crown-of-thorns sea star, Acanthaster planci, preys on the flesh of live coral. At times, these sea
stars undergo poorly understood population explosions. What impact should such explosions have on
those sea slugs that bear cerata (cerata contain nematocysts)? Population explosions of this sea star
should
A) benefit sea slugs by distracting their prey.
B) benefit sea slugs by helping subdue their prey.
C) harm sea slugs by competing with them for food.
D) harm sea slugs by consuming them as food.
E) harm sea slugs by fouling the water with their feces.
70) The sharp, inch-long thorns of the crown-of-thorns sea star are its spines. These spines, unlike those
of most other sea stars, contain a potent toxin. If it were discovered that crown-of-thorns sea stars do not
make this toxin themselves, then the most likely alternative would be that this toxin is
A) derived from the nematocysts of its prey.
B) absorbed from the surrounding seawater.
C) an endotoxin of cellulose-digesting bacteria that inhabit the sea star’s digestive glands.
D) injected into individual thorns by mutualistic corals which live on the aboral surfaces of these sea
stars.
71) The crown-of-thorns sea star, Acanthaster planci, preys on the flesh of live coral. If coral animals
are attacked by these sea stars, then what actually provides nutrition to the sea star, and which chemical
(besides the toxin within their nematocysts) do the corals rely on for protection?
A) medusas; silica
B) exoskeleton; silica
C) exoskeleton; calcium carbonate
D) polyps; calcium carbonate
E) polyps; silica
72) The reason their exoskeletons cannot protect the corals from sea stars is that the sea star
A) is immune to the toxin of the nematocysts.
B) thorns are sharp and toxic.
C) tubefeet act as tiny syringes that suck the corals out of their exoskeletons.
D) stomach can be everted, and can release digestive juices directly onto the corals.
73) A natural predator of the crown-of–thorns sea star is a mollusc called the Giant Triton, Charonia
tritonis. If the triton uses a radula to saw into the sea star, then to which clade should the triton belong?
A) chitons
B) bivalves
C) gastropods
D) cephalopods
74) Which human profession is most analogous to the lifestyle of the sea slugs described in this
scenario?
A) physician
B) pirate
C) pharmacist
D) plumber
E) painter
A farm pond, usually dry during winter, has plenty of water and aquatic pond life during the summer.
One summer, Sarah returns to the family farm from college. Observing the pond, she is fascinated by
some six-legged organisms that can crawl about on submerged surfaces or, when disturbed, seemingly
“jet” through the water. Watching further, she is able to conclude that the “mystery organisms” are
ambush predators, and their prey includes everything from insects to small fish and tadpoles.
75) From this description, one can conclude that the organisms that have caught Sarah’s attention are
A) insects.
B) crustaceans.
C) aquatic spiders.
D) myriapods.
E) eurypterids.
76) Sarah noticed the presence of many empty exoskeletons attached to emergent vegetation. These
exoskeletons looked exactly like those of the largest of the “mystery organisms” she had seen in the
pond. They also looked similar to the bodies of the dragonflies that patrolled the surface of the pond. If
Sarah had learned a lot from her college biology class, what should she have concluded about the
mysterious pond organisms?
A) They are larval dragonflies, destined to undergo incomplete metamorphosis.
B) They are larval dragonflies, destined to undergo complete metamorphosis.
C) They are adult dragonflies, so old that they can no longer fly, have fallen into the pond, but have not
yet drowned.
D) They are adult dragonflies that must, like many amphibian species, return to water in order to mate.
77) If the pond organisms are larvae, rather than adults, Sarah should expect them to have all of the
following structures, except
A) antennae.
B) an open circulatory system.
C) an exoskeleton of chitin.
D) complex eyes.
E) sex organs.
78) Sarah observed that the mystery pond organisms never come up to the pond’s surface. If she catches
one of these organisms and observes closely, perhaps dissecting the organism, she should find
A) gills.
B) spiracles.
C) tracheae.
D) book lungs.
79) Sarah had learned that ancestral (Carboniferous era) dragonfly species were much larger than extant
dragonfly species are, with wingspans of 70 cm. This struck her as odd, because she had also learned
that one of the things that keeps insects small is their relatively inefficient respiratory system. Which two
hypotheses might help account for the large size of ancestral dragonflies?
1. If the atmosphere during the Carboniferous era had featured a higher oxygen content than the modern
atmosphere, then the tracheae might have been a sufficient means for oxygen delivery to the interior
tissues.
2. If large size was a drawback, then the large dragonflies underwent extinction, which explains why all
extant dragonflies are smaller.
3. If the ancestral dragonflies had possessed muscles that permitted effective ventilation of the tracheae,
then the tracheae might have been a sufficient means for oxygen delivery to the interior tissues.
4. If ancestral dragonflies existed during greenhouse conditions, then they must have survived by
decreasing their activity levels, such as no longer capturing prey in flight. Thus, for them, an ineffective
respiratory system was sufficient.
A) 1 and 2
B) 1 and 3
C) 1 and 4
D) 2 and 3
E) 2 and 4
An elementary school science teacher decided to liven up the classroom with a saltwater aquarium.
Knowing that saltwater aquaria can be quite a hassle, the teacher proceeded stepwise. First, the teacher
conditioned the water. Next, the teacher decided to stock the tank with various marine invertebrates,
including a polychaete, a siliceous sponge, several bivalves, a shrimp, several sea anemones of different
types, a colonial hydra, a few coral species, an ectoproct, a sea star, and several herbivorous gastropod
varieties. Lastly, she added some vertebrates–a parrotfish and a clownfish. She arranged for daily
feedings of copepods and feeder fish.
80) One day, little Tommy (a student in an undersupervised class of 40 fifth graders) got the urge to pet
Nemo (the clownfish), who was swimming among the waving petals of a pretty underwater “flower”
that had a big hole in the midst of the petals. Tommy giggled upon finding that these petals felt sticky. A
few hours later, Tommy was in the nurse’s office with nausea and cramps. Microscopic examination of
his fingers would probably have revealed the presence of
A) teeth marks.
B) spines.
C) spicules.
D) nematocysts.
E) a radula.
81) How many of the following organisms possess bilateral symmetry as adults?
1. sponges
2. molluscs
3. echinoderm
4. sea anemones
5. ectoprocts
A) one of these
B) two of these
C) three of these
D) four of these
E) five of these
82) If the teacher wanted to show the students what a lophophore is and how it works, the teacher would
point out a feeding
A) hydra.
B) sponge.
C) bivalve.
D) gastropod.
E) ectoproct.
83) The bivalves started to die one by one; only the undamaged shells remained. To keep the remaining
bivalves alive, the teacher would have to remove the
A) sea anemones.
B) sea star.
C) gastropods.
D) ectoprocts.
E) parrotfish.
84) If the teacher had used a dissecting microscope to examine the outer surfaces of the empty bivalve
shells, the teacher would probably have seen marks that had been left by
A) jaws.
B) nematocysts.
C) tubefeet.
D) a lophophore.
E) a madreporite.
85) The teacher was unaware of the difference between suspension feeding and predation. The teacher
thought that providing live copepods (2 mm long) and feeder fish (2 cm long) would satisfy the dietary
needs of all of the organisms. Consequently, which two organisms would have been among the first to
starve to death (assuming they lack photosynthetic endosymbionts)?
A) sponges and corals
B) sea stars and sponges
C) shrimp and bivalves
D) corals and bivalves
E) bivalves and sponges
86) If the teacher had wanted to demonstrate that some invertebrates possess a closed circulatory system,
the teacher should have removed and dissected a
A) mollusc.
B) sea star.
C) shrimp.
D) polychaete.
E) parrotfish.
87) Had the teacher wanted to point out organisms that belong to the most successful animal phylum, the
teacher should have chosen the
A) bivalves and gastropods.
B) sea anemones and hydra.
C) shrimp and copepods.
D) polychaete.
88) The clownfish readily swims among the tentacles of the sea anemones; the parrotfish avoids them.
One hypothesis for the clownfish’s apparent immunity is that they slowly build a tolerance to the sea
anemone’s toxin. A second hypothesis is that a chemical in the mucus that coats the clownfish prevents
the nematocysts from being triggered. Which of the following graphs supports the second, but not the
first, of these hypotheses?
A)
B)
C)
D)
89) The teacher and class were especially saddened when the colonial hydrozoan died. They had
watched it carefully, and the unfortunate creature never even got to produce offspring by budding. Yet,
everyone was elated when Tommy (now recovered) noticed a small colonial hydrozoan growing in a
part of the tank far from the location of the original colony. The teacher was apparently unaware that
these hydrozoans exhibit
A) spontaneous generation.
B) abiogenesis.
C) alternation of generations.
D) ecdysis.
E) a medusa stage.
End-of-Chapter Questions
The following questions are from the end-of–chapter “Test Your Understanding” section in Chapter 33
of the textbook.
90) A land snail, a clam, and an octopus all share
A) a mantle.
B) a radula.
C) gills.
D) embryonic torsion.
E) distinct cephalization.
91) Which phylum is characterized by animals that have a segmented body?
A) Cnidaria
B) Platyhelminthes
C) Porifera
D) Arthropoda
E) Mollusca
92) The water vascular system of echinoderms
A) functions as a circulatory system that distributes nutrients to body cells.
B) functions in locomotion and feeding.
C) is bilateral in organization, even though the adult animal is not bilaterally symmetrical.
D) moves water through the animal’s body during suspension feeding.
E) is analogous to the gastrovascular cavity of flatworms.
93) Which of the following combinations of phylum and description is incorrect?
A) Echinodermata–bilateral symmetry as a larva, coelom present
B) Nematoda–roundworms, pseudocoelomate
C) Cnidaria–radial symmetry, polyp and medusa body forms
D) Platyhelminthes–flatworms, gastrovascular cavity, acoelomate
E) Porifera–gastrovascular cavity, coelom present