Ch 33: An Introduction to Invertebrates

Question 1

1) Use the following information to answer the question.
The phylum Cycliophora was discovered in 1995. They are tiny organisms that live in large
numbers on the outsides of the mouthparts and appendages of lobsters. The feeding stage
permanently attaches to the lobster via an adhesive disk and collects scraps of food from its
host’s feeding by capturing the scraps in a current created by a ring of cilia. The body is saclike
and has a U-shaped intestine that brings the anus close to the mouth. Cycliophorans are
coelomates, do not molt (though their host does), and their embryos undergo spiral cleavage.

Which of these features is least useful in assigning the phylum Cycliophora to a clade of
animals?

A) having a true coelom as a body cavity

B) having a body symmetry that permits a U-shaped intestine

C) having embryos with spiral cleavage

D) lacking ecdysis (molting)

Answer 1

A

Section: 33.0

Question 2

2) Use the following information to answer the question.
The phylum Cycliophora was discovered in 1995. They are tiny organisms that live in large
numbers on the outsides of the mouthparts and appendages of lobsters. The feeding stage
permanently attaches to the lobster via an adhesive disk and collects scraps of food from its
host’s feeding by capturing the scraps in a current created by a ring of cilia. The body is saclike
and has a U-shaped intestine that brings the anus close to the mouth. Cycliophorans are
coelomates, do not molt (though their host does), and their embryos undergo spiral cleavage.

Which of these, if discovered among cycliophorans, would cause the most confusion concerning
our current understanding of cycliophoran taxonomy?

A) if the ciliated feeding ring is a lophophore
B) if embryos are diploblastic
C) if the body cavity is actually a pseudocoelom
D) if the organisms show little apparent cephalization

Answer 2

B

Section: 33.0

Question 3

3) Use the following information to answer the question.
The phylum Cycliophora was discovered in 1995. They are tiny organisms that live in large
numbers on the outsides of the mouthparts and appendages of lobsters. The feeding stage
permanently attaches to the lobster via an adhesive disk and collects scraps of food from its
host’s feeding by capturing the scraps in a current created by a ring of cilia. The body is saclike
and has a U-shaped intestine that brings the anus close to the mouth. Cycliophorans are
coelomates, do not molt (though their host does), and their embryos undergo spiral cleavage.

The feeding stage of cycliophorans ________.

A) is autotrophic and captures food in a manner similar to gastropods

B) is sessile and captures food in a manner similar to that of animals with lophophores

C) is sessile and radially symmetric

D) is autotrophic and sessile

Answer 3

B

Section: 33.0

Question 4

4) Use the following information to answer the question.
The phylum Cycliophora was discovered in 1995. They are tiny organisms that live in large
numbers on the outsides of the mouthparts and appendages of lobsters. The feeding stage
permanently attaches to the lobster via an adhesive disk and collects scraps of food from its
host’s feeding by capturing the scraps in a current created by a ring of cilia. The body is saclike
and has a U-shaped intestine that brings the anus close to the mouth. Cycliophorans are
coelomates, do not molt (though their host does), and their embryos undergo spiral cleavage.

Basing your inferences on information in the paragraph, to which clades should cycliophorans
belong?

A) Eumetazoa and Bilateria

B) Eumetazoa and Lophotrochozoa

C) Deuterostomia and Ecdysozoa

D) Deuterostomia and Lophotrochozoa

Answer 4

B

Section: 33.0

Question 5

5) One should expect to find cilia associated with the feeding apparatus of ________.

A) annelids

B) coral animals

C) tapeworms

D) sponges

Section: 33.1

Answer 5

D

Question 6

6) Sponges ________.

A) have larvae that are motile and move via the motion of cilia

B) are the simplest diploblastic animals

C) have a nerve net but not a central nervous system

D) have feeding cells called dinoflagellates

Section: 33.1

Answer 6

A

Question 7

7) Which of the following is most likely to be aquatic?

A) filter feeder

B) mass feeder

C) deposit feeder

D) fluid feeder

Section: 33.1

Answer 7

A

Question 8

8) Which of the following can be found in the mesohyl of a sponge?

A) amoebocytes and choanocytes

B) spicules and choanocytes

C) amoebocytes and spicules

D) amoebocytes and polyps

Section: 33.1

Answer 8

C

Question 9

9) Use the graph to answer the following question.

Which of the following factors, when used to label the horizontal axis of the graph, would
account most directly for the shape of the plot?

A) rate of cribrostatin synthesis (molecules/unit time)

B) number of pores per sponge

C) number of spicules per sponge

D) number of choanocytes per sponge

Section: 33.1

Answer 9

D

Question 10

10) Healthy corals are brightly colored because they ________.

A) secrete colorful
pigments to attract mates

B) host symbionts with colorful photosynthetic pigments

C) build their skeletons from colorful minerals

D) secrete colorful pigments to protect themselves from ultraviolet light

Section: 33.2

Answer 10

B

Question 11

11) In terms of food capture, which sponge cell is most similar to the cnidocyte of a cnidarian?

A) amoebocyte

B) choanocyte

C) epidermal cell

D) pore cell

Section: 33.2

Answer 11

B

Question 12

13) Use the following information to answer the question.

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 parrot
fish and a clown fish. She arranged for daily feedings of copepods and feeder fish.

One day, Tommy, a student in an undersupervised class of 40 fifth graders, got the urge to pet
Nemo (the clown fish), 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

Section: 33.2

Answer 12

D

Question 13

13) Use the following information to answer the question.

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 parrot
fish and a clown fish. She arranged for daily feedings of copepods and feeder fish.

One day, Tommy, a student in an undersupervised class of 40 fifth graders, got the urge to pet
Nemo (the clown fish), 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

Section: 33.2

Answer 13

D

Question 14

14) Use the following information to answer the question.
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 parrot
fish and a clown fish. She arranged for daily feedings of copepods and feeder fish.

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 one of the students 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) a medusa stage

Section: 33.2

Answer 14

D

Question 15

15) 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-ofthorns
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

Section: 33.2

Answer 15

A

Question 16

16) Use the following information to answer the question.
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 parrot
fish and a clown fish. She arranged for daily feedings of copepods and feeder fish.
Normally, the clown fish readily swims among the tentacles of the sea anemones; the parrot fish
avoids them. One hypothesis for the clown fish’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 clown fish prevents the nematocysts from being triggered. Which of the following
graphs supports the second, but not the first, of these hypotheses?

A) Number of non-discharged Nematocysts per unit surface area of tentacle after contact
< Parrot Fish = tall bar>

B) Number of non-discharged Nematocysts per unit surface area of tentacle after contact
< Parrot Fish = tall bar>

C) Number of non-discharged Nematocysts per unit surface area of tentacle after contact
< Parrot Fish = small bar>

D) Number of non-discharged Nematocysts per unit surface area of tentacle after contact
< Parrot Fish = small bar>

Section 33.2

Answer 16

C

Question 17

17) Use the following information to answer the question.
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 parrot
fish and a clown fish. She arranged for daily feedings of copepods and feeder fish.
Normally, the clown fish readily swims among the tentacles of the sea anemones; the parrot fish
avoids them. One hypothesis for the clown fish’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 clown fish prevents the nematocysts from being triggered. Which of the following
graphs supports the first, but not the second, of these hypotheses?

A) Number of non-discharged Nematocysts per unit surface area of tentacle after contact
< Parrot Fish = tall bar>

B) Number of non-discharged Nematocysts per unit surface area of tentacle after contact
< Parrot Fish = tall bar>

C) Number of non-discharged Nematocysts per unit surface area of tentacle after contact
< Parrot Fish = small bar>

D) Number of non-discharged Nematocysts per unit surface area of tentacle after contact
< Parrot Fish = small bar>

Section 33.2

Answer 17

B

Question 18

18) The presence of a lophophore in a newly discovered species would suggest that the species
________.

A) has an exoskeleton

B) grows by shedding its external covering

C) is motile

D) is a filter feeder

Section: 33.3

Answer 18

D

Question 19

19) You find what you believe is a new species of animal. Which of the following characteristics
would enable you to argue that it is more closely related to a flatworm than it is to a roundworm?

A) It is a suspension feeder.

B) It has no coelom.

C) It is shaped like a worm.

D) It has a mouth and an anus.

Section: 33.3

Answer 19

B

Question 20

20) What would be the best anatomical feature to look for to distinguish a gastropod from a
chiton?

A) presence of a muscular foot

B) presence of a rasp-like feeding structure

C) production of eggs

D) dorsal plates

Section: 33.3

Answer 20

D

Question 21

21) Which of the following organisms would you expect to have the largest surface-area-tovolume
ratio? Assume that all of the following are the same total length.

A) a mollusc

B) an annelid

C) an arthropod

D) a platyhelminth

Section: 33.3

Answer 21

D

Question 22

22) Against which hard structure do the circular and longitudinal muscles of annelids work?

A) cuticle

B) shell

C) endoskeleton

D) hydrostatic skeleton

Section: 33.3

Answer 22

D

Question 23

23) While sampling marine plankton in a lab, a student encounters large numbers of fertilized
eggs. The student rears some of the eggs in the laboratory for further study and finds that the
blastopore becomes the mouth. The embryo develops into a trochophore larva and eventually has
a true coelom. These eggs probably belonged to a(n) ________.

A) echinoderm

B) mollusc

C) nematode

D) arthropod

Section: 33.3

Answer 23

B

Question 24

24) Use the information to answer the following question.
The nontaxonomic term sea slug encompasses a wide variety of marine gastropods. One feature
they share as adults is the lack of a shell. One might think, therefore, that they represent
defenseless morsels for predators. In fact, sea slugs have multiple defenses. Some sea slugs prey
on sponges and concentrate sponge toxins in their tissues. Others feed on cnidarians, digesting
everything except the nematocysts, which they then transfer to their own skins. Whereas the
most brightly colored sea slugs are often highly toxic, others are nontoxic and mimic the
coloration of the toxic species. Their colors are mostly derived from pigments in their prey.
There are also sea slugs that use their coloration to blend into their environments.

This nudibranch, a type of sea slug, has many reddish cerata on its dorsal surface, as well as two
white-tipped rhinophores located on the head.

Which structure do sea slugs use to feed on their prey?

A) nematocysts

B) an incurrent siphon

C) a radula

D) a mantle cavity

Section: 33.3

Answer 24

C

Question 25

25) Use the information to answer the following question.
The nontaxonomic term sea slug encompasses a wide variety of marine gastropods. One feature
they share as adults is the lack of a shell. One might think, therefore, that they represent
defenseless morsels for predators. In fact, sea slugs have multiple defenses. Some sea slugs prey
on sponges and concentrate sponge toxins in their tissues. Others feed on cnidarians, digesting
everything except the nematocysts, which they then transfer to their own skins. Whereas the
most brightly colored sea slugs are often highly toxic, others are nontoxic and mimic the
coloration of the toxic species. Their colors are mostly derived from pigments in their prey.
There are also sea slugs that use their coloration to blend into their environments.

This nudibranch, a type of sea slug, has many reddish cerata on its dorsal surface, as well as two
white-tipped rhinophores located on the head.

The nematocysts most likely reach the skin of sea slugs through branches of the ________.

A) intestine

B) excurrent siphon

C) nephridium

D) pseudocoelom

Section: 33.3

Answer 25

A

Question 26

26) Use the information to answer the following question.
The nontaxonomic term sea slug encompasses a wide variety of marine gastropods. One feature
they share as adults is the lack of a shell. One might think, therefore, that they represent
defenseless morsels for predators. In fact, sea slugs have multiple defenses. Some sea slugs prey
on sponges and concentrate sponge toxins in their tissues. Others feed on cnidarians, digesting
everything except the nematocysts, which they then transfer to their own skins. Whereas the
most brightly colored sea slugs are often highly toxic, others are nontoxic and mimic the
coloration of the toxic species. Their colors are mostly derived from pigments in their prey.
There are also sea slugs that use their coloration to blend into their environments.

This nudibranch, a type of sea slug, has many reddish cerata on its dorsal surface, as well as two
white-tipped rhinophores located on the head.

The nematocysts of sea slugs should be most effective at protecting individual sea slugs from
predation if the predators ________.

A) remove small bites of flesh from sea slugs and have long-term memory

B) remove small bites of flesh from sea slugs and have no long-term memory

C) consume entire sea slugs in one gulp and have no long-term memory

D) consume entire sea slugs in one gulp and have long-term memory

Section: 33.3

Answer 26

A

Question 27

27) Use the information and figure to answer the following question.

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 ×
105 cells/mg of sea slug protein) can promote sea slug survival.

Percent of sea slug respiratory carbon demand provided by indwelling dinoflagellates.

If the dinoflagellate-containing sea slug P. ianthina preys on coral animals, then it would be most
surprising to find that ________.

A) P. ianthina can tolerate 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

Section: 33.3

Answer 27

D

Question 28

28) Use the information and figure to answer the following question.

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 ×
105 cells/mg of sea slug protein) can promote sea slug survival.
Percent of sea slug respiratory carbon demand provided by indwelling dinoflagellates.

In the graph, the percent of the oxygen demand contributed by the dinoflagellates is greater than
100% during much of the year. What is the fate of this “excess” energy?

A) It is dispersed as “entropy” (disorder in the system).

B) It is saved for producing offspring by the sea slug.

C) It is used to move around the sea bottom.

D) It is used in evaporative cooling by the sea slug.

Section: 33.3

Answer 28

B

Question 29

29) 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?

A) provide Elysia with fixed nitrogen

B) provide Elysia with fixed carbon dioxide

C) provide Elysia with fixed oxygen

D) provide Elysia with a bright color that warns away potential predators

Section: 33.3

Answer 29

B

Question 30

30) Use the following information to answer the question.
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 parrot
fish and a clown fish. She arranged for daily feedings of copepods and feeder fish.
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) gastropod

D) ectoproct

Section: 33.3

Answer 30

D

Question 31

31) What would be the most effective method of reducing the incidence of blood flukes in a
human population?

A) reduce the mosquito population

B) reduce the population of the intermediate snail host

C) avoid contact with rodent droppings

D) carefully wash all raw fruits and vegetables

Section: 33.3

Answer 31

B

Question 32

32) Use the information and figure to answer the following question.
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 ×
105 cells/mg of sea slug protein) can promote sea slug survival.
Percent of sea slug respiratory carbon demand provided by indwelling dinoflagellates.
According to the graph, during which season(s) of the year is the relationship between the sea
slug and its dinoflagellates closest to being commensal?

A) winter

B) spring

C) summer

D) spring and summer

Section: 33.3

Answer 32

A

Question 33

33) Planarians lack dedicated respiratory and circulatory systems. This deficiency does not cause
a problem because ________.

A) none of their cells are far removed from the gastrovascular cavity or from the external
environment

B) they lack mesoderm as embryos and, therefore, lack the adult tissues derived from mesoderm

C) their flame bulbs can carry out respiratory and circulatory functions

D) their body cavity, a pseudocoelom, carries out these functions

Section: 33.3

Answer 33

A

Question 34

34) Which one of these mollusc groups can be classified as suspension feeders?

A) bivalves

B) gastropods

C) chitons

D) cephalopods

Section: 33.3

Answer 34

A

Question 35

35) Which characteristic is shared by cnidarians and flatworms?

A) dorsoventrally flattened bodies

B) radial symmetry

C) a digestive system with a single opening

D) a distinct head

Section: 33.3

Answer 35

C

Question 36

36) If a lung were to be found in a mollusc, where would it be located?

A) mantle cavity

B) incurrent siphon

C) visceral mass

D) excurrent siphon

Section: 33.3

Answer 36

A

Question 37

37) Parasitism is one of the most widespread lifestyles ever to evolve. Which of the following is
consistent with this finding?

A) Parasites almost always predigest their hosts’ tissues and, therefore, spend less energy and
require fewer structural adaptations.

B) Parasites, unlike predators, feed on almost all the tissues of their host.

C) Parasites do not generally kill their hosts; thus they can feed on the same host throughout the
host’s normal life span and do not have competition from decomposers.

D) Parasites generally kill their host and can feed for a very long time because they are much
smaller than their host.

Section: 33.3

Answer 37

C

Question 38

38) Molecular studies have changed many of the phylogenetic relationships previously identified
by morphological studies. An example of such a change is ________.

A) Lochotrophozora

B) Placozoa

C) Brachiopoda

D) Bivalvia

Section: 33.3

Answer 38

A

Question 39

39) Molecular studies have changed many of the phylogenetic relationships previously identified
by morphological studies. These changes indicate that ________.

A) molecular and morphological studies rarely agree

B) molecular studies add additional information to morphological studies and improve our
understanding of evolutionary history

C) molecular studies are less reliable than morphological studies

D) molecular studies are extremely time consuming and expensive and really don’t add
additional information to our understanding of evolutionary history

Section: 33.3

Answer 39

B

Question 40

40) Large animals need specialized organs for gas exchange because ________.

A) they require more oxygen per unit of volume

B) surface area increases more rapidly than volume as size increases

C) volume increases more rapidly than surface area as size increases

D) they collect more energy and therefore have more energy to allocate to specialized tissues

Section: 33.3

Answer 40

C

Question 41

41) Toilets are a modern convenience that people often take for granted. In fact, they are helpful
in preventing spread of disease because ________.

A) disease-causing insects die quickly in fecal-contaminated water

B) toilets disinfect human feces

C) many diseases are transmitted by flying insects

D) many parasites release fertilized eggs in the feces of humans and other animals

Section: 33.3

Answer 41

D

Question 42

42) Imagine that you are a graduate student seeking an idea for a research project that will help
us understand the evolution of a parasitic lifestyle from a free-living lifestyle. Which of the
following outcomes would you expect if you compare the genes of parasitic species to relatives
that are free living?

A) The parasitic species will have fewer functioning genes than the free-living species because
loss of many genes will not be harmful.

B) The free-living species will have more functioning genes because they evolved new traits.

C) The genes will have changed in base sequence, but the number of functioning genes in
parasitic and free-living species will be the same.

D) More genes for sensing the environment will have evolved in the parasitic species as
compared to the free-living species.

Section: 33.3

Answer 42

A

Question 43

43) Imagine that you are a research chemist who wishes to develop a chemical adhesive that will
work under water. Which of the following organisms might give you a clue about where to start?

A) sea wasps

B) trematodes

C) lobsters

D) mussels

Section: 33.3

Answer 43

D

Question 44

44) Which of the following changes would lead to an increase in surface-area-to-volume ratios?

A) thickening of the body of earthworms

B) increasing the number of layers in the chloroplasts of plants

C) decreasing the projections of the choanocytes of sponges on the outer surface of the body

D) reducing the branching of the mesoderm tissues of sponges

Section: 33.3

Answer 44

B

Question 45

45) Without genetic variation, evolution cannot occur. Sexual reproduction leads to increased
genetic variation, but male bdelloid rotifers have never been observed. Which of the following
are correct statements with regard to evolution in bdelloid rotifers?

A) As we learn more about bdelloid rotifers, we find males in more and more species.

B) Bdelloid rotifers gain genetic variation by absorbing DNA from the external environment.

C) Protists infect bdelloids and bring DNA from other rotifers with them.

D) Bdelloid rotifers have lost the ability to reproduce sexually only recently.

Section: 33.3

Answer 45

B

Question 46

46) Which of the following statements about bryozoans (ectoprocts) is correct?

A) Bryozoans are colonial, build reefs, and are related to corals.

B) Bryozoans are colonial and live amongst mosses.

C) Adult bryozoans are sessile, but their larvae make up much of marine plankton.

D) Bryozoans build reefs and have lophophores that extend through a hard exoskeleton.

Section: 33.3

Answer 46

D

Question 47

47) Nematodes and arthropods both ________.

A) develop an anus from the blastopore (pore) formed in the gastrula stage

B) are parasites

C) grow in conjunction with shedding of their exoskeleton

D) have ciliated larvae

Section: 33.4

Answer 47

C

Question 48

48) Arthropod exoskeletons and mollusc shells both ________.

A) completely replace the hydrostatic skeleton

B) are secreted by the mantle

C) help retain moisture in terrestrial habitats

D) are comprised of the polysaccharide chitin

Section: 33.4

Answer 48

C

Question 49

49) You find a multi-legged animal in your garden and want to determine if it is a centipede or a
millipede. You take the animal to a university where a myriapodologist quickly tells you that you
have found a centipede. Which of the following traits may have allowed her to make this
distinction?

A) presence of body segments

B) poisonous claws

C) egg-laying

D) molting

Section: 33.4

Answer 49

B

Question 50

50) Whiteflies are common pest insects found on cotton, tomato, poinsettia, and many other
plants. Nymphs are translucent and mostly sessile, feeding on their host plant’s phloem (sap)
from the undersides of leaves. They undergo incomplete metamorphosis into winged adults.
Because whitefly nymphs cannot escape predation by moving, you hypothesize that their
translucent bodies make them hard to spot by predators. How could you directly test this
hypothesis?

A) Compare rates of predation on whitefly nymphs on plant leaves of different colors (for
example, red versus green poinsettia leaves).

B) Compare rates of predation on whitefly nymphs coated with a nontoxic dye versus undyed whitefly nymphs.

C) Compare rates of predation on whitefly nymphs versus whitefly adults.

D) Compare rates of predation on whitefly nymphs by predators that are translucent versus
predators that are not translucent.

Section: 33.4

Answer 50

B

Question 51

51) All insects ________.

A) undergo complete metamorphosis and have segmented bodies

B) have jointed appendages and a radula

C) undergo complete metamorphosis and have an exoskeleton or cuticle

D) have jointed appendages and spicules

Section: 33.4

Answer 51

C

Question 52

52) Use the following information and figures to answer the question.

Many terrestrial arthropods exchange gases with their environments by using tracheae, tubes that
lead from openings (called spiracles) in the animal’s exoskeleton or cuticle directly to the
animal’s tissues. Some arthropods can control whether their spiracles are opened or closed;
opening the spiracles allows the carbon dioxide produced in the tissues to travel down the
tracheae and be released outside the animal. Klok et al. measured the carbon dioxide emitted
over time (represented by VCO2) by several species of centipedes. The figures present graphs of
their results for two species, Cormocephalus morsitans and Scutigerina weberi. (C. J. Klok, R.
D. Mercer, and S. L. Chown. 2002. Discontinuous gas-exchange in centipedes and its convergent
evolution in tracheated arthropods. Journal of Experimental Biology 205:1019-29.) Copyright
2002 The Company of Biologists and the Journal of Experimental Biology.

Look at the graph for Cormocephalus morsitans in the figure. What is the best interpretation of
these results?

A) The centipede had its spiracles open the entire time.

B) The centipede had its spiracles closed the entire time.

C) The centipede had its spiracles open when carbon dioxide (CO2) emission peaked and closed
when CO2 emission was low.

D) The centipede had its spiracles closed when carbon dioxide (CO2) emission peaked and open
when CO2 emission was low.

Section: 33.4

Answer 52

C

Question 53

53) Use the following information and figures to answer the question.

Many terrestrial arthropods exchange gases with their environments by using tracheae, tubes that
lead from openings (called spiracles) in the animal’s exoskeleton or cuticle directly to the
animal’s tissues. Some arthropods can control whether their spiracles are opened or closed;
opening the spiracles allows the carbon dioxide produced in the tissues to travel down the
tracheae and be released outside the animal. Klok et al. measured the carbon dioxide emitted
over time (represented by VCO2) by several species of centipedes. The figures present graphs of
their results for two species, Cormocephalus morsitans and Scutigerina weberi. (C. J. Klok, R.
D. Mercer, and S. L. Chown. 2002. Discontinuous gas-exchange in centipedes and its convergent
evolution in tracheated arthropods. Journal of Experimental Biology 205:1019-29.) Copyright
2002 The Company of Biologists and the Journal of Experimental Biology.

Look at the graph for Scutigerina weberi (note the scale of the y-axis) in the figure. What is the
best interpretation of these results?

A) The centipede had its spiracles open the entire time.

B) The centipede had its spiracles closed the entire time.

C) The centipede had its spiracles open when carbon dioxide (CO2) emission peaked and closed
when CO2 emission was low.

D) The centipede had its spiracles closed when carbon dioxide (CO2) emission peaked and open
when CO2 emission was low.

Section: 33.4

Answer 53

A

Question 54

54) Use the following information and figures to answer the question.

Many terrestrial arthropods exchange gases with their environments by using tracheae, tubes that
lead from openings (called spiracles) in the animal’s exoskeleton or cuticle directly to the
animal’s tissues. Some arthropods can control whether their spiracles are opened or closed;
opening the spiracles allows the carbon dioxide produced in the tissues to travel down the
tracheae and be released outside the animal. Klok et al. measured the carbon dioxide emitted
over time (represented by VCO2) by several species of centipedes. The figures present graphs of
their results for two species, Cormocephalus morsitans and Scutigerina weberi. (C. J. Klok, R.
D. Mercer, and S. L. Chown. 2002. Discontinuous gas-exchange in centipedes and its convergent
evolution in tracheated arthropods. Journal of Experimental Biology 205:1019-29.) Copyright
2002 The Company of Biologists and the Journal of Experimental Biology.

How would a terrestrial centipede most likely benefit from the ability to close its spiracles?
Closing spiracles would ________.

A) allow the centipede to move more quickly

B) allow the centipede to retain more moisture in its tissues

C) allow the centipede to stay warmer

D) allow more oxygen from the environment to reach the centipede’s tissues

Section: 33.4

Answer 54

B

Question 55

55) Use the following information and figures to answer the question.

Many terrestrial arthropods exchange gases with their environments by using tracheae, tubes that
lead from openings (called spiracles) in the animal’s exoskeleton or cuticle directly to the
animal’s tissues. Some arthropods can control whether their spiracles are opened or closed;
opening the spiracles allows the carbon dioxide produced in the tissues to travel down the
tracheae and be released outside the animal. Klok et al. measured the carbon dioxide emitted
over time (represented by VCO2) by several species of centipedes. The figures present graphs of
their results for two species, Cormocephalus morsitans and Scutigerina weberi. (C. J. Klok, R.
D. Mercer, and S. L. Chown. 2002. Discontinuous gas-exchange in centipedes and its convergent
evolution in tracheated arthropods. Journal of Experimental Biology 205:1019-29.) Copyright
2002 The Company of Biologists and the Journal of Experimental Biology.

Compare the graphs in the figure of carbon dioxide (CO2) emission for Cormocephalus
morsitans and Scutigerina weberi. What hypothesis can you make about each centipede’s
habitat?

A) C. morsitans lives in a habitat that provides more carbon dioxide than does S. weberi.

B) C. morsitans lives in a habitat with more predators than does S. weberi.

C) C. morsitans lives in a colder habitat than does S. weberi.

D) C. morsitans lives in a drier habitat than does S. weberi.

Section: 33.4

Answer 55

D

Question 56

56) What would be the most direct effect of removing or damaging an insect’s antennae? The
insect would have trouble ________.

A) hearing

B) mating

C) seeing

D) smelling

Section: 33.4

Answer 56

D

Question 57

57) The heartworms that can accumulate within the hearts of dogs and other mammals have a pseudocoelom, an alimentary canal, and an outer covering that is occasionally shed. To which phylum does the heartworm belong?

A) Platyhelminthes

B) Arthropoda

C) Nematoda

D) Annelida

Section: 33.4

Answer 57

C

Question 58

58) A terrestrial animal species is discovered with the following larval characteristics:
exoskeleton, system of tubes for gas exchange, and modified segmentation. A knowledgeable
zoologist should predict that the adults of this species would also feature ________.

A) eight legs

B) two pairs of antennae

C) a sessile lifestyle

D) an open circulatory system

Section: 33.4

Answer 58

D

Question 59

59) In a tide pool, a student encounters an organism with a hard outer covering that contains
much calcium carbonate, an open circulatory system, and gills. The organism could potentially
be a crab, a shrimp, a barnacle, or a bivalve. The presence of which of the following structures
would allow for the most certain identification of the organism?

A) a mantle

B) a heart

C) a body cavity

D) a filter-feeding apparatus

Section: 33.3

Answer 59

A

Question 60

60) Use the following information to answer the question.

Nudibranchs, a type of predatory sea slug, can have various protuberances (that is, extensions)
on their dorsal surfaces. Rhinophores are paired structures, located close to the head, which bear
many chemoreceptors. Dorsal plumules, usually located posteriorly, perform respiratory gas
exchange. Cerata usually cover much of the dorsal surface and contain nematocysts at their tips.

The claws on the foremost trunk segment of centipedes have a function most similar to that of
________.

A) rhinophores

B) dorsal plumules

C) cerata

D) chemoreceptors

Section: 33.4

Answer 60

C

Question 61

61) Use the following information to answer the question.

Nudibranchs, a type of predatory sea slug, can have various protuberances (that is, extensions)
on their dorsal surfaces. Rhinophores are paired structures, located close to the head, which bear
many chemoreceptors. Dorsal plumules, usually located posteriorly, perform respiratory gas
exchange. Cerata usually cover much of the dorsal surface and contain nematocysts at their tips.

The stingers of honeybees have a function most similar to that of ________.

A) rhinophores

B) dorsal plumules

C) cerata

D) chemoreceptors

Section: 33.4

Answer 61

C

Question 62

62) Use the following information to answer the question.

Nudibranchs, a type of predatory sea slug, can have various protuberances (that is, extensions)
on their dorsal surfaces. Rhinophores are paired structures, located close to the head, which bear
many chemoreceptors. Dorsal plumules, usually located posteriorly, perform respiratory gas
exchange. Cerata usually cover much of the dorsal surface and contain nematocysts at their tips.

The spiracles and tracheae of insects have a function most similar to that of ________.

A) rhinophores

B) dorsal plumules

C) cerata

D) chemoreceptors

Section: 33.4

Answer 62

B

Question 63

63) Use the following information to answer the question.

Nudibranchs, a type of predatory sea slug, can have various protuberances (that is, extensions)
on their dorsal surfaces. Rhinophores are paired structures, located close to the head, which bear
many chemoreceptors. Dorsal plumules, usually located posteriorly, perform respiratory gas
exchange. Cerata usually cover much of the dorsal surface and contain nematocysts at their tips.

The antennae of insects have a function most similar to that of ________.

A) rhinophores

B) dorsal plumules

C) cerata

D) chemoreceptors

Section: 33.4

Answer 63

A

Question 64

64) Use the following information to answer the question.

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.

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) sex organs

Section: 33.4

Answer 64

D

Question 65

65) Use the following information to answer the question.

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.

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

Section: 33.4

Answer 65

A

Question 66

66) Use the following information and figure to answer the question.

Aphids are Hemiptera that suck phloem liquid from plants. Ants are often seen tapping the
posterior end of the aphid and collecting the liquid that is released from the aphid’s digestive
system. In an effort to understand this interaction, several researchers measure the survival rates
of aphid populations when ants were present and when they were excluded. Their results are
shown.

Which of the following conclusions is most likely correct?

A) Ants derive nourishment from the aphids.

B) Ants protect the aphids from predators.

C) Ants parasitize the aphids.

D) Ants feed the aphids.

Section: 33.4

Answer 66

B

Question 67

67) Use the following information and figure to answer the question.

Aphids are Hemiptera that suck phloem liquid from plants. Ants are often seen tapping the
posterior end of the aphid and collecting the liquid that is released from the aphid’s digestive
system. In an effort to understand this interaction, several researchers measure the survival rates
of aphid populations when ants were present and when they were excluded.
Their results are shown.

Imagine that you wished to discover if the ants protect the aphids from flying predators. You
would exclude ants from the plants and count aphid population size under two conditions. Which
of the following experiments would best help answer this question?

A) plants covered by netting versus not covered by netting

B) plants with stems coated at the base with a sticky substance versus not coated with a sticky
substance

C) plants with extra fertilizer and water versus no extra fertilizer and water

D) plants sprayed with insecticide versus not sprayed with insecticide

Section: 33.4

Answer 67

A

Question 68

68) Soft-shell crab is a prized dish in many ocean-side resorts. Why are the crabs’ shells soft?

A) The crab has just molted and the new exoskeleton has not yet hardened.

B) These species of crabs live under rocks and therefore have lost the hard exoskeleton over
evolutionary time.

C) These species have evolved a light and soft exoskeleton so that gases can diffuse directly
between body of the crab and the surrounding water.

D) These species have evolved a light and soft exoskeleton so that they can float in the water
column.

Section: 33.4

Answer 68

A

Question 69

69) Compared to insects with incomplete metamorphosis, insects with complete metamorphosis
________.

A) grow more slowly in size

B) use a greater variety of food resources

C) have slower population growth rates

D) have better abilities to escape from predators

Section: 33.4

Answer 69

B

Question 70

70) The increase in plant species diversity allowed which of the following events?

A) the evolution of complete metamorphosis in insects

B) the evolution of flight in insects

C) invasion of marine habitats by insects

D) a massive increase in species diversity of insects

Section: 33.4

Answer 70

D

Question 71

71) As you are walking along a beach, you find an animal and believe that it belongs to the class
Asteroidea. Which of the following characteristics would support your hypothesis that the animal
is a sea star and not another type of echinoderm?

A) It is pentaradially symmetric.

B) It feeds on other animals.

C) It has a hydrostatic skeleton, formed from its water vascular system.

D) Its central region is not well delineated from its appendages.

Section: 33.5

Answer 71

D

Question 72

72) 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) is analogous to the gastrovascular cavity of flatworms

Section: 33.5

Answer 72

B

Question 73

73) Which of the following combinations correctly matches a phylum to its description?

A) Echinodermata—bilateral symmetry as a larva, water vascular system

B) Nematoda—segmented worms, closed circulatory system

C) Cnidaria—flatworms, gastrovascular cavity, acoelomate

D) Platyhelminthes—radial symmetry, polyp and medusa body forms

Section: 33.5

Answer 73

A

Question 74

74) Which of the following animal groups is entirely aquatic?

A) Mollusca

B) Crustacea

C) Echinodermata

D) Nematoda

Section: 33.5

Answer 74

C

Question 75

75) Use the following information to answer the question.

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 parrot
fish and a clown fish. She arranged for daily feedings of copepods and feeder fish.

The bivalves started to die one by one; only the undamaged shells remained. To keep the
remaining bivalves alive, the teacher would most likely need to remove the ________.

A) sea anemones

B) sea star

C) gastropods

D) ectoprocts

Section: 33.5

Answer 75

B

Question 76

76) Which of the following statements is correct with respect to the evolutionary relationship
between chordates and invertebrates?

A) Chordates are most closely related to arthropods.

B) Chordates evolved from echinoderms.

C) Chordates are more closely related to echinoderms than to arthropods.

D) Chordates are most closely related to the tunicate-type of echinoderms.

Section: 33.5

Answer 76

C

Question 77

77) Echinoderms show enormous diversity in which of the following traits?

A) body shape and food habits

B) food habits and body symmetry

C) body symmetry and method of food digestion

D) method of food digestion and body shape

Section: 33.5

Answer 77

A

Question 78

33. 2 End-of-Chapter Questions
    1) A land snail, a clam, and an octopus all share

A) a mantle.

B) a radula.

C) gills.

D) distinct cephalization.

Answer 78

A

Question 79

33. 2 End-of-Chapter Questions
    2) Which phylum is characterized by animals that have a segmented body?

A) Cnidaria

B) Platyhelminthes

C) Arthropoda

D) Mollusca

Answer 79

C

Question 80

33. 2 End-of-Chapter Questions
    3) 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 filter feeding.

Answer 80

B

Question 81

33. 2 End-of-Chapter Questions
    4) Which of the following combinations of phylum and description is incorrect?

A) Echinodermata—bilateral symmetry as a larva, coelomate

B) Nematoda—roundworms, pseudocoelomate

C) Platyhelminthes—flatworms, gastrovascular cavity, acoelomate

D) Porifera—gastrovascular cavity, coelomate

Answer 81

D

Question 82

33.2 End-of-Chapter Questions

5)
In Figure 33.2 (p.686), which two main clades branch from the most recent common ancestor of the
eumetazoans?

A) Porifera and Cnidaria

B) Lophotrochozoa and Ecdysozoa

C) Cnidaria and Bilateria

D) Deuterostomia and Bilateria

Answer 82

C

Question 83

33.2 End-of-Chapter Questions

6)
In Figure 33.7 (p.693), assume that the two medusae shown at step 4 were produced by one polyp
colony. Review Concept 12.1 and Concept 13.3, and then use your understanding of mitosis and meiosis to evaluate whether the following sentence is true or false; if false, select the answer that provides the correct reason. Although the two medusae are genetically identical, a sperm
produced by one will differ genetically from an egg produced by the other.

A) False (both the medusae and the gametes are genetically identical)

B) False (neither the medusae nor the gametes are genetically identical)

C) False (the medusae are not identical but the gametes are)

D) True

Answer 83

D