Ch 32: An Overview of Animal Diversity

Question 1

1) A researcher is trying to construct a molecular-based phylogeny of the entire animal kingdom.
Assuming that none of the following genes are absolutely conserved, which of the following
would be the best choice on which to base the phylogeny?

A) genes involved in chitin synthesis
B) collagen genes
C) genes involved in directing segmentation development
D) genes involved in eye-lens synthesis

Answer 1

B

Question 2

2) Which of the following is (are) unique to animals?

A) the structural carbohydrate, chitin
B) nervous system signal conduction and muscular movement
C) heterotrophy
D) flagellated gametes

Answer 2

B

Question 3

3) The larvae of some insects are merely small versions of the adult, whereas the larvae of other
insects look completely different from adults, eat different foods, and may live in different
habitats. Which of the following is most directly involved in the evolution of these variations in
metamorphosis?

A) artificial selection of sexually immature forms of insects
B) changes in the homeobox genes controlling early development
C) the evolution of meiosis
D) the origin of a brain

Answer 3

B

Question 4

7) Both animals and fungi are heterotrophic. What distinguishes animal heterotrophy from fungal
heterotrophy is that most animals derive their nutrition by ________.

A) preying on animals
B) ingesting materials
C) consuming living, rather than dead, prey
D) using enzymes to digest their food

Answer 4

B

Question 5

8) Use the information to answer the question.
Trichoplax adhaerens is the only living species in the phylum Placozoa. Individuals are about 1
mm wide and only 27 μm high, are irregularly shaped, and consist of a total of about 2,000 cells,
which are diploid (2n = 12). There are four types of cells, none of which are nerve or muscle
cells, and none of which have cell walls. Individual animals move using cilia, and any “edge” can
lead. T. adhaerens feeds on marine microbes, mostly unicellular green algae, by crawling atop
the algae and trapping it between its ventral surface and the substrate. Enzymes are then secreted
onto the algae, and the resulting nutrients are absorbed. T. adhaerens sperm cells have never
been observed, nor have embryos past the 64-cell (blastula) stage.

Which of the following T. adhaerens traits is different from all other known animals?

A) T. adhaerens is multicellular.
B) T. adhaerens lacks muscle and nerve cells.
C) T. adhaerens has cilia.
D) T. adhaerens lacks cell walls.

Answer 5

B

Question 6

9) What do animals ranging from corals to monkeys have in common?

A) a mouth and an anus
B) number of embryonic tissue layers
C) some type of body symmetry
D) presence of Hox genes

Answer 6

D

Question 7

10) In individual insects of some species, whole chromosomes that carry larval genes are
eliminated from the genomes of somatic cells at the time of metamorphosis. A consequence of
this occurrence is that ________.

A) we could not clone a larva from the somatic cells of such an adult insect
B) such species must reproduce only asexually
C) the descendants of these adults do not include a larval stage
D) metamorphosis can no longer occur among the descendants of such adults

Answer 7

A

Question 8

11) The fact that choanoflagellates and collar cells of sponges resemble each other supports the
inference that ________.

A) choanoflagellates are animals
B) choanoflagellates are more closely related to sponges than they are to protists
C) choanoflagellates and sponges are sister groups
D) choanoflagellates and sponges evolved similar cell structures through convergent evolution

Answer 8

C

Question 9

12) Which of the following would you classify as something other than an animal?

A) sponge
B) coral
C) jellyfish
D) choanoflagellate

Answer 9

D

Question 10

13) The evolution of animal species has been prolific (current estimates of species numbers reach
into the tens of millions). Much of this diversity is a result of the evolution of novel ways to
________.

A) reproduce
B) arrange cells into tissues
C) sense, feed, and move
D) form an embryo and establish a basic body plan

Answer 10

C

Question 11

14) The last common ancestor of all animals was probably a ________.

A) unicellular chytrid
B) multicellular algae
C) multicellular fungus
D) flagellated protist

Answer 11

D

Question 12

15) Evidence of which structure or characteristic would be most surprising to find among fossils
of the Ediacaran fauna?

A) true tissues
B) hard parts
C) bilateral symmetry
D) embryos

Answer 12

B

Question 13

16) One hypothesis suggests that the Cambrian explosion was caused by the rise of predator-prey
relationships. This hypothesis is best supported by an increased incidence of which of the
following fossil traces?

A) worm burrows
B) larger animals
C) organic material
D) hard parts

Answer 13

D

Question 14

17) Which of the following genetic processes may be most helpful in accounting for the
Cambrian explosion?

A) binary fission
B) random segregation
C) gene duplication
D) chromosomal condensation

Answer 14

C

Question 15

18) Whatever its ultimate cause(s), the Cambrian explosion is a prime example of ________.

A) mass extinction
B) evolutionary stasis
C) adaptive radiation
D) a large meteor impact

Answer 15

C

Question 16

19) Arthropods invaded land about 100 million years before vertebrates. This fact most clearly
implies that ________.

A) arthropods evolved before vertebrates did
B) extant terrestrial arthropods are better adapted to terrestrial life than are extant terrestrial
vertebrates
C) vertebrates evolved from arthropods
D) arthropods have had more time to coevolve with land plants than have vertebrates

Answer 16

D

Question 17

20) Cadherin proteins help animal cells stick (adhere) to each other. Choose which statement
about cadherin in cancer cells that are metastasizing (spreading) throughout a patient’s body is
most likely correct.

A) Cadherin proteins in metastasizing cancer cells are likely to have mutations that make them
less “sticky.”
B) Cadherin proteins in metastasizing cancer cells are likely to have mutations that make them
more “sticky.”
C) Mutations in cadherin proteins are unlikely to affect the metastasizing of cancer cells.
D) Mutations in cadherin proteins accumulate at a constant rate that can be measured by a
molecular clock.

Answer 17

A

Question 18

21) Which of the following factors most likely contributed to the extinction of many Ediacaran
life forms?

A) predation by new species, poisoning from high carbon dioxide levels, and loss of
developmental flexibility
B) predation by new species, poisoning from high oxygen levels, and loss of habitat due to
increased temperatures
C) predation by new species, faster movement by new species, and increased developmental
flexibility by new species
D) loss of habitat due to increased temperatures, poisoning from high oxygen levels, and loss of
developmental flexibility

Answer 18

C

Question 19

22) Which tissue type or organ is not correctly matched with its germ layer tissue?

A) nervous—mesoderm
B) muscular—mesoderm
C) stomach—endoderm
D) skin—ectoderm

Answer 19

A

Question 20

23) While looking at some seawater through your microscope, you spot the egg of an unknown
animal. Which of the following tests could you use to determine whether the developing
organism is a protostome or a deuterostome? See whether the embryo ________.

A) develops germ layers
B) exhibits spiral cleavage or radial cleavage
C) develops a blastopore
D) develops an archenteron

Answer 20

B

Question 21

24) In examining an unknown animal species during its embryonic development, how can you be
sure what you are looking at is a protostome and not a deuterostome?

A) There is evidence of cephalization.
B) The animal is triploblastic.
C) The animal is clearly bilaterally symmetrical.
D) You see a mouth, but not an anus.

Answer 21

D

Question 22

25) Which of the following is a feature of the “tube-within-a-tube” body plan in most animal
phyla?
A) The outer tube consists of a hard exoskeleton.
B) The outer tube consists of digestive organs.
C) The mouth and anus form the ends of the inner tube.
D) The two “tubes” are separated by tissue that comes from embryonic endoderm

Answer 22

C

Question 23

26) If you think of the earthworm body plan as a drinking straw within a pipe, where would you
expect to find most of the tissues that developed from endoderm?

A) lining the straw
B) lining the space between the pipe and the straw
C) forming the outside of the pipe
D) forming the outside of the straw

Answer 23

A

Question 24

27) Among protostomes, which morphological trait has shown the most variation?

A) type of symmetry (bilateral versus radial versus none)
B) type of body cavity (coelom versus pseudocoelom versus no coelom)
C) number of embryonic tissue types (diploblasty versus triploblasty)
D) type of development (protostome versus deuterostome)

Answer 24

B

Question 25

28) What do all deuterostomes have in common?

A) Adults are bilaterally symmetrical.
B) Embryos have pharyngeal pouches that may or may not form gill slits.
C) All have a spinal column.
D) The pore (blastopore) formed during gastrulation becomes the anus.

Answer 25

D

Question 26

29) Soon after the coelom begins to form, a researcher injects a dye into the coelom of a
deuterostome embryo. Initially, the dye should be able to flow directly into the ________.

A) blastopore
B) blastocoel
C) archenteron
D) pseudocoelom

Answer 26

C

Question 27

30) You have before you a living organism, which you examine carefully. Which of the
following should convince you that the organism is acoelomate?

A) It is triploblastic.
B) It has bilateral symmetry.
C) It possesses sensory structures at its anterior end.
D) Muscular activity of its digestive system distorts the body wall.

Answer 27

D

Question 28

31) Use the information to answer the question.
One small animal phylum (Placozoa) contains only two species, Trichoplax adhaerens (T.
adhaerens) and T. reptans. T. adhaerens is the only species seen in over a century. Individuals
are about 1 mm wide and only 27 μm high, are irregularly shaped, and consist of a total of about
2,000 cells, which are diploid (2n = 12). There are four types of cells, none of which are nerve or
muscle cells, and none of which have cell walls. Individual animals move using cilia, and any
“edge” can lead. T. adhaerens feeds on marine microbes, mostly unicellular green algae, by
crawling atop the algae and trapping it between its ventral surface and the substrate. Enzymes are
then secreted onto the algae, and the resulting nutrients are absorbed. T. adhaerens sperm cells
have never been observed. Embryos up to, but not past, the 64-cell (blastula) stage have been
observed.

On the basis of information in the paragraph, which of these should be able to be observed in T.
adhaerens?

A) a coelom
B) the process of gastrulation
C) eggs
D) a radially symmetric larval form

Answer 28

C

Question 29

32) A student encounters an animal embryo at the eight-cell stage. The four smaller cells that
comprise 1 hemisphere of the embryo seem to be rotated 45° and to lie in the grooves between
larger, underlying cells. This embryo may potentially develop into a(n) ________.

A) turtle
B) earthworm
C) sea star
D) sea urchin

Answer 29

B

Question 30

33) A student encounters an animal embryo at the eight-cell stage. The four smaller cells that
comprise 1 hemisphere of the embryo seem to be rotated 45° and to lie in the grooves between
larger, underlying cells. If we were to separate these eight cells and attempt to culture them
individually, then what is most likely to happen?

A) All eight cells will die immediately.
B) Each cell may continue development, but only into a nonviable embryo that lacks many parts.
C) Each cell may develop into a full-sized, normal embryo.
D) Each cell may develop into a smaller-than-average, but otherwise normal, embryo.

Answer 30

B

Question 31

34) What was an early selective advantage of a coelom in animals? A coelom ________.

A) contributed to a hydrostatic skeleton, allowing greater range of motion
B) was a more efficient digestive system
C) allowed cephalization and the formation of a cerebral ganglion
D) allowed asexual and sexual reproduction

Answer 31

A

Question 32

35) The protostome developmental sequence arose just once in evolutionary history, resulting in
two main subgroups—Lophotrochozoa and Ecdysozoa. What does this finding suggest?

A) These two subgroups have a common ancestor that was a deuterostome.
B) The protostomes are a polyphyletic group.
C) Division of these two groups occurred after the protostome developmental sequence
appeared.
D) The lophotrochozoans are monophyletic

Answer 32

C

Question 33

36) Which of these statements, if accurate, would support the claim that the ancestral cnidarians
had bilateral symmetry?

A) Cnidarian larvae possess anterior-posterior, left-right, and dorsal-ventral aspects.
B) Cnidarians have fewer Hox genes than bilaterians.
C) All cnidarians are acoelomate.
D) The presence of collar cells

Answer 33

A

Question 34

37) An organism that exhibits a head with sensory equipment and a brain probably also
________.

A) is bilaterally symmetrical
B) has a coelom
C) is segmented
D) is diploblastic

Answer 34

A

Question 35

38) Suppose a researcher for a pest-control company developed a chemical that inhibited the
development of an embryonic mosquito’s endodermal cells. Which of the following would be a
likely mechanism by which this pesticide works?

A) The mosquito would develop a weakened exoskeleton that would make it vulnerable to
trauma.
B) The mosquito would have trouble digesting food, due to impaired gut function.
C) The mosquito would have trouble with respiration and circulation, due to impaired muscle
function.
D) The mosquito wouldn’t be affected at all.

Answer 35

B

Question 36

39) Use the information to answer the question.
Trichoplax adhaerens is the only living species in the phylum Placozoa. Individuals are about 1
mm wide and only 27 μm high, are irregularly shaped, and consist of a total of about 2,000 cells,
which are diploid (2n = 12). There are four types of cells, none of which are nerve or muscle
cells, and none of which have cell walls. Individual animals move using cilia, and any “edge” can
lead. T. adhaerens feeds on marine microbes, mostly unicellular green algae, by crawling atop
the algae and trapping it between its ventral surface and the substrate. Enzymes are then secreted
onto the algae, and the resulting nutrients are absorbed. T. adhaerens sperm cells have never
been observed, nor have embryos past the 64-cell (blastula) stage.

T. adhaerens’ body symmetry seems to be most like that of ________.

A) most sponges
B) cnidarians
C) worms
D) tetrapods

Answer 36

A

Question 37

40) Use the 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.
If nudibranch rhinophores are located at the anterior ends of these sea slugs, then they contribute
to the sea slugs’ ________.

A) segmentation
B) lack of torsion
C) development of a head
D) identity as lophotrochozoans

Answer 37

C

Question 38

41) What is the probable sequence in which the following animal clades originated, from earliest
to most recent?

A) bilaterians, deuterostomes, vertebrates, tetrapods, amniotes
B) bilaterians, deuterostomes, amniotes, vertebrates, tetrapods
C) deuterostomes, bilaterians, amniotes, vertebrates, tetrapods
D) deuterostomes, bilaterians, vertebrates, tetrapods, amniotes

Answer 38

A

Question 39

42) The most ancient branch point in animal phylogeny is the characteristic of having ________.

A) radial or bilateral symmetry
B) diploblastic or triploblastic embryos
C) true tissues or no tissues
D) a body cavity or no body cavity

Answer 39

C

Question 40

43) When a scientist describes the “body plan” of a phylum, he or she is implying that ________.

A) organisms direct their own evolution in order to maximize their success
B) animals evolve according to a pre-ordained plan
C) the body shapes we see now have been more successful than others in the past
D) mutations have arisen that allow only some shapes to be produced

Answer 40

C

Question 41

44) Which of the following statements comparing symmetry in sessile and swimming animals is
most probable?

A) Radial symmetry is more advantageous for active swimming than is bilateral symmetry.
B) Radial symmetry occurs most frequently in animals that catch their prey by rapid swimming.
C) Bilateral symmetry allowed animals to evolve nerves.
D) Bilaterally symmetric animals can be streamlined for swimming, but radially symmetric
animals cannot.

Answer 41

D

Question 42

45) The primary difference between a coelom and a pseudocoelom is ________.

A) their developmental origin
B) the manner in which they cushion the internal organs
C) a coelom arises in the ectoderm, and a pseudocoelom arises in the endoderm
D) a coelom occurs in triploblastic animals, and a pseudocoelom occurs in diploblastic animals

Answer 42

A

Question 43

46) Nine-banded armadillos give birth to four offspring at a time. An amazing fact about these
offspring is that they are genetically identical to each other. This fact suggests ________.

A) the young undergo metamorphosis
B) the embryo undergoes radial and indeterminate cleavage
C) the first cell division of the fertilized egg is perpendicular to the vertical axis of the egg
D) the species is pseudocoelomate

Answer 43

B

Question 44

47) You find a new species of worm and want to classify it. Which of the following lines of
evidence would allow you to classify the worm as a nematode and not an annelid?

A) It is segmented.
B) It is triploblastic.
C) It has a coelom.
D) It sheds its external skeleton to grow

Answer 44

D

Question 45

48) The common ancestor of the protostomes had a coelom. What does this suggest?

A) All lophotrochozoans have a coelom.
B) There are no pseudocoelomates within the protostomes.
C) There are no acoelomates within the protostomes.
D) The body cavity evolved before the lophophore.

Answer 45

D

Question 46

49) Use the figure to answer the question.

In the traditional phylogeny (A), the phylum Platyhelminthes is depicted as a sister taxon to the
rest of the protostome phyla and as having diverged earlier from the lineage that led to the rest of
the protostomes. In the molecular phylogeny (B), Platyhelminthes is depicted as a
Lophotrochozoan phylum. What probably led to this change?

A) Platyhelminthes ceased to be recognized as true protostomes.
B) The removal of the acoel flatworms (Acoela) from the Platyhelminthes allowed the remaining
flatworms to be a monophyletic clade clearly tied to the Lophotrochozoa.
C) All Platyhelminthes must have a well-developed lophophore as their feeding apparatus.
D) Platyhelminthes’ close genetic ties to the arthropods became clear as their Hox gene
sequences were studied.

Answer 46

B

Question 47

50) The last common ancestor of all bilaterians is thought to have had four Hox genes. Most
extant cnidarians have two Hox genes, though some have three Hox genes. On the basis of these
observations, some have proposed that the ancestral cnidarian’s were originally bilateral and, in
stages, lost Hox genes from their genomes. If true, this would mean that ________.

A) all radially symmetric animals should be grouped together in one clade
B) the radial symmetry of extant cnidarians is secondarily derived, rather than being an ancestral
trait
C) Hox genes play little actual role in coding for an animal’s “body plan”
D) cnidaria may someday replace porifera as the basal bilaterians

Answer 47

B

Question 48

51) Some researchers claim that sponge genomes have homeotic genes, but no Hox genes. If
true, this finding would ________.

A) mean that sponges must no longer be classified as animals
B) confirm the identity of sponges as “basal animals”
C) mean that extinct sponges must have been the last common ancestor of animals and fungi
D) require sponges to be reclassified as choanoflagellates

Answer 48

B

Question 49

52) Use the figure to answer the question.

Which morphological trait evolved more than once in animals, according to the phylogeny based
on DNA sequence data found in the figure?

A) coelom
B) bilateral symmetry
C) segmentation
D) protostome development

Answer 49

C

Question 50

53) Use the figure to answer the question.

Which of the following statements is supported by the phylogeny in the figure?

A) Deuterostoma are more evolutionarily advanced than Porifera.
B) Traits, once they evolve, are retained in later-evolving taxonomic groups.
C) Animals show no evidence of convergent evolution in their traits.
D) Animals with extremely different adult forms can be relatively closely related.

Answer 50

D

Question 51

54) Use the figure to answer the question.

Which of the following pairs of animals show that animals with widely different adult features
can be each other’s closest relatives?

A) Annelida and Nematoda
B) Chordata and Echinodermata
C) Cnidemia and Ctenophoa
D) Annelida and Rotifera

Answer 51

B

Question 52

55) Why might researchers choose to use molecular data (such as ribosomal RNA sequences)
rather than morphological data to study the evolutionary history of animals?

A) Molecular data can be gathered in the lab, while morphological data must be gathered in the
field.
B) Molecular data can be used to give an estimate of the time since two groups split.
C) Morphological changes usually do not result from molecular changes.
D) Some phyla vary too widely in morphological characteristics to be classified accurately.

Answer 52

B

Question 53

56) If in the future the current molecular evidence regarding animal origins is further
substantiated, which of the following statements would be correct with reference to fossil
evidence that contradicts molecular evidence?

A) The contrary fossil evidence will be seen as a hoax.
B) The fossil evidence will be understood to have been interpreted incorrectly because it is
incomplete.
C) The fossil record will, henceforth, be ignored.
D) Phylogenies involving even the smallest bit of fossil evidence will need to be discarded.

Answer 53

B

Question 54

57) Use the table to answer the question.

What conclusion can best be drawn from the data in the table?

A) Land animals have more Hox genes than do those that live in water.
B) All bilaterian phyla have had the same degree of expansion in their numbers of Hox genes.
C) The expansion in number of Hox genes throughout vertebrate evolution cannot be explained
merely by three duplications of the ancestral vertebrate Hox cluster.
D) Extant insects all have seven Hox genes.

Answer 54

C

Question 55

58) Which of the following statements concerning animal taxonomy is accurate?

A) Animals are thought to have evolved from flagellated protists similar to modern
choanoflagellates.
B) Kingdom Animalia is polyphyletic.
C) Animals are more closely related to plants than to fungi.
D) In the kingdom Animalia, most clades based on body plan or fossils have been found to be
incorrect.

Answer 55

A

Question 56

59) In the future, phylogenetic studies should be conducted to ________.

A) resolve the branching patterns (evolutionary history) of the Lophotrochozoa
B) discover the Hox genes in sponges
C) discover the relationships between nematodes and platyhelminthes
D) discover the larval stages of echinoderms

Answer 56

A

Question 57

60) At one time, sponges were lumped into one phylum. Then, they were separated into several
different phyla. Now, they are considered one phylum again. These changes indicate which of
the following?

A) Every phylogeny should be considered a hypothesis that must be revised in the light of new
data.
B) We need more fossil evidence of sponges.
C) Molecular and morphological data often conflict when we try to reconstruct evolutionary
history.
D) The goal of making all taxonomic groups monophyletic is unrealistic.

Answer 57

A

Question 58

61) Sponges and ctenophores have both been proposed as basal metazoans. Which of the
following types of data support the idea that sponges are the basal group?

A) sequences of cadherin genes, cleavage type, structure of collar cells, and bilateral symmetry
of adults
B) sequences of collagen genes, bilateral symmetry of adults, cleavage type, and fossil steroids
C) fossil steroids, molecular clock, lack of tissues in sponges, and structure of collar cells
D) structure of collar cells, bilateral symmetry of larvae, sequences of cadherin genes, and
molecular clock

Answer 58

C

Question 59

62) Sponges and ctenophores have both been proposed as basal metazoans. Imagine that you
wanted to provide additional evidence to help resolve this question. Which of the following
projects would be the best next step?

A) more extensive study of DNA sequences in the bilateria
B) ultrastructural (that is, electron microscope) comparisons of choanoflagellates and sperm cells
from arthropods
C) measurements of molecular clocks from the Lophotrochozoa
D) more extensive studies of DNA sequences in both groups

Answer 59

B

Question 60

63) Placing sponges as the basal metazoans on the basis of lack of tissues implies which of the
following?

A) Sponge ancestors never had tissues.
B) Modern-day sponges have lost the ability to form tissues.
C) Multicellular, modern-day choanoflagellates can form tissues.
D) Sponges do not have nerve cells.

Answer 60

A

Question 61

End-of-Chapter Question

1) One of the characteristics unique to animals is

A) gastrulation.
B) multicellularity.
C) sexual reproduction.
D) flagellated sperm.

Answer 61

A

Question 62

End-of-Chapter Question

2) The distinction between sponges and other animal phyla is based mainly on the absence
versus the presence of

A) a body cavity.
B) a complete digestive tract.
C) mesoderm.
D) tissues.

Answer 62

D

Question 63

End-of-Chapter Question

3) Which of the following was probably the least important factor in bringing about the
Cambrian explosion?

A) the emergence of predator-prey relationships
B) an increase in the concentration of atmospheric oxygen
C) the movement of animals
D) the origin of Hox genes

Answer 63

C

Question 64

End-of-Chapter Question

Based on the tree shown (Figure 32.11), which statement is FALSE?
A) The animal kingdom is monophyletic.
B) Acoelomate flatworms are more closely related to echinoderms than to annelids.
C) Sponges are basal animals.
D) Bilaterians form a clade.

Answer 64

B

Question 65

End-of-Chapter Question

Based on the tree shown (Figure 32.11), which statement is TRUE?
A) The animal kingdom is not monophyletic.
B) Acoela are more closely related to echinoderms than to annelids.
C) Sponges are basal animals.
D) Bilaterians do not form a clade.

Answer 65

C