Campbell’s Biology, 9e (Reece et al.)
Chapter 32 An Overview of Animal Diversity
About 40% of the questions in this chapter are either scenario questions or art questions, which typically
involve higher-order thinking. Among these are two new sets of scenario questions, each devoted to a
single-species animal phylum. The first pertains to the (possibly) basal animal known as Trichoplax, and
the second to the bizarre phylum found only on lobster lips, the Cycliophora.
Multiple-Choice Questions
1) Both animals and fungi are heterotrophic. What distinguishes animal heterotrophy from fungal
heterotrophy is that only animals derive their nutrition by
A) preying on animals.
B) ingesting it.
C) consuming living, rather than dead, prey.
D) using enzymes to digest their food.
2) 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 most directly favors the evolution of the latter, more radical, kind of metamorphosis?
A) natural selection of sexually immature forms of insects
B) changes in the homeobox genes governing early development
C) the evolution of meiosis
D) the development of an oxidizing atmosphere on Earth
E) the origin of a brain
3) Which of the following is (are) unique to animals?
A) cells that have mitochondria
B) the structural carbohydrate, chitin
C) nervous conduction and muscular movement
D) heterotrophy
E) Two of these responses are correct.
4) What do animals as diverse as corals and monkeys have in common?
A) body cavity between body wall and digestive system
B) number of embryonic tissue layers
C) type of body symmetry
D) presence of Hox genes
E) degree of cephalization
5) The Hox genes came to regulate each of the following in what sequence, from earliest to most recent?
1. identity and position of paired appendages in protostome embryos
2. anterior-posterior orientation of segments in protostome embryos
3. positioning of tentacles in cnidarians
4. anterior-posterior orientation in vertebrate embryos
A) 4 → 1 → 3 → 2
B) 4 → 2 → 3 → 1
C) 4 → 2 → 1 → 3
D) 3 → 2 → 1 → 4
E) 3 → 4 → 1 → 2
6) 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 descendents of these adults do not include a larval stage.
D) metamorphosis can no longer occur among the descendents of such adults.
E) Two of these responses are correct.
7) The last common ancestor of all animals was probably a
A) unicellular chytrid.
B) unicellular yeast.
C) multicellular algae.
D) multicellular fungus.
E) flagellated protist.
8) 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) cephalization
E) embryos
9) Which statement is most consistent with the hypothesis that the Cambrian explosion was caused by
the rise of predator-prey relationships?
A) increased incidence of worm burrows in the fossil record
B) increased incidence of larger animals in the fossil record
C) increased incidence of organic material in the fossil record
D) increased incidence of fern galls in the fossil record
E) increased incidence of hard parts in the fossil record
10) Which of the following genetic processes may be most helpful in accounting for the Cambrian
explosion?
A) binary fission
B) mitosis
C) random segregation
D) gene duplication
E) chromosomal condensation
11) Whatever its ultimate cause(s), the Cambrian explosion is a prime example of
A) mass extinction.
B) evolutionary stasis.
C) adaptive radiation.
D) All three of the responses are correct.
E) Only two of the responses are correct.
12) Fossil evidence indicates that the following events occurred in what sequence, from earliest to most
recent?
1. Protostomes invade terrestrial environments.
2. Cambrian explosion occurs.
3. Deuterostomes invade terrestrial environments.
4. Vertebrates become top predators in the seas.
A) 2 → 4 → 3 → 1
B) 2 → 1 → 4 → 3
C) 2 → 4 → 1 → 3
D) 2 → 3 → 1 → 4
E) 2 → 1 → 3 → 4
13) What is the probable sequence in which the following clades of animals originated, from earliest to
most recent?
1. tetrapods
2. vertebrates
3. deuterostomes
4. amniotes
5. bilaterians
A) 5 → 3 → 2 → 4 → 1
B) 5 → 3 → 2 → 1 → 4
C) 5 → 3 → 4 → 2 → 1
D) 3 → 5 → 4 → 2 → 1
E) 3 → 5 → 2 → 1 → 4
14) Arthropods invaded land about 100 million years before vertebrates did so. This 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) ancestral arthropods must have been poorly adapted to aquatic life, and thus experienced a selective
pressure to invade land.
D) vertebrates evolved from arthropods.
E) arthropods have had more time to coevolve with land plants than have vertebrates.
15) An adult animal that possesses bilateral symmetry is most certainly also
A) triploblastic.
B) a deuterostome.
C) eucoelomate.
D) highly cephalized.
16) 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.
17) A researcher is trying to construct a molecular-based phylogeny of the entire animal kingdom.
Assuming that none of the following genes is 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) β-catenin genes
D) genes involved in eye-lens synthesis
E) genes that cause radial body symmetry
18) At which developmental stage should one be able to first distinguish a diploblastic embryo from a
triploblastic embryo?
A) fertilization
B) cleavage
C) gastrulation
D) coelom formation
E) metamorphosis
19) At which developmental stage should one be able to first distinguish a protostome embryo from a
deuterostome embryo?
A) fertilization
B) cleavage
C) gastrulation
D) coelom formation
E) metamorphosis
20) What distinguishes a coelomate animal from a pseudocoelomate animal is that coelomates
A) have a body cavity, whereas pseudocoelomates have a solid body.
B) contain tissues derived from mesoderm, whereas pseudocoelomates have no such tissue.
C) have a body cavity completely lined by mesodermal tissue, whereas pseudocoelomates do not.
D) have a complete digestive system with mouth and anus, whereas pseudocoelomates have a digestive
tract with only one opening.
E) have a gut that lacks suspension within the body cavity, whereas pseudocoelomates have mesenteries
that hold the digestive system in place.
21) 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.
22) The blastopore is a structure that first becomes evident during
A) fertilization.
B) gastrulation.
C) the eight-cell stage of the embryo.
D) coelom formation.
E) cleavage.
23) The blastopore denotes the presence of an endoderm-lined cavity in the developing embryo, a cavity
that is known as the
A) archenteron.
B) blastula.
C) coelom.
D) germ layer.
E) blastocoel.
24) Which of the following is descriptive of protostomes?
A) spiral and indeterminate cleavage, blastopore becomes mouth
B) spiral and determinate cleavage, blastopore becomes mouth
C) spiral and determinate cleavage, blastopore becomes anus
D) radial and determinate cleavage, blastopore becomes anus
E) radial and determinate cleavage, blastopore becomes mouth
25) Which of the following characteristics generally applies to protostome development?
A) radial cleavage
B) determinate cleavage
C) diploblastic embryo
D) blastopore becomes the anus
E) archenteron absent
26) Protostome characteristics generally include which of the following?
A) a mouth that develops secondarily, and far away from the blastopore
B) radial body symmetry
C) radial cleavage
D) determinate cleavage
E) absence of a body cavity
27) The most ancient branch point in animal phylogeny is that between having
A) radial or bilateral symmetry.
B) a well-defined head or no head.
C) diploblastic or triploblastic embryos.
D) true tissues or no tissues.
E) a body cavity or no body cavity.
28) With the current molecular-based phylogeny in mind, rank the following from most inclusive to
least inclusive.
1. ecdysozoan
2. protostome
3. eumetazoan
4. triploblastic
A) 4, 2, 3, 1
B) 4, 3, 1, 2
C) 3, 4, 1, 2
D) 3, 4, 2, 1
E) 4, 3, 2, 1
29) What does recent evidence from molecular systematics reveal about the relationship between grades
and clades?
A) There is no relationship.
B) Some, but not all, grades reflect evolutionary relatedness.
C) Grades have their basis in, and flow from, clades.
D) Each branch point on a phylogenetic tree is associated with the evolution of a new grade.
30) Phylogenetic trees are best described as
A) true and inerrant statements about evolutionary relationships.
B) hypothetical portrayals of evolutionary relationships.
C) the most accurate representations possible of genetic relationships among taxa.
D) theories of evolution.
E) the closest things to absolute certainty that modern systematics can produce.
31) According to the evidence collected so far, the animal kingdom is
A) monophyletic.
B) paraphyletic.
C) polyphyletic.
D) euphyletic.
E) multiphyletic.
32) If a multicellular animal lacks true tissues, then it can properly be included among the
A) eumetazoans.
B) metazoans.
C) choanoflagellates.
D) lophotrochozoans.
E) bilateria.
33) Which of the following statements concerning animal taxonomy is (are) true?
1. Animals are more closely related to plants than to fungi.
2. All animal clades based on body plan have been found to be incorrect.
3. Kingdom Animalia is monophyletic.
4. Only animals reproduce by sexual means.
5. Animals are thought to have evolved from flagellated protists similar to modern choanoflagellates.
A) 5 only
B) 1 and 3
C) 3 and 5
D) 3, 4, and 5
34) If the current molecular evidence regarding animal origins is well-substantiated in the future, then
what will be true of any contrary evidence regarding the origin of animals derived from the fossil
record?
A) The contrary fossil evidence will be seen as a hoax.
B) The fossil evidence will be understood to have been incorrect 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.
E) Only phylogenies based solely on fossil evidence will need to be discarded.
35) What is true of the clade Ecdysozoa?
A) It includes all animals that molt at some time during their lives.
B) It includes all animals that undergo metamorphosis at some time during their lives.
C) It includes all animals that have body cavities known as pseudocoeloms.
D) It includes all animals with genetic similarities that are shared with no other animals.
E) It includes all animals in the former clade Protostomia that truly do have protostome development.
36) Which distinction is given more emphasis by the morphological phylogeny than by the molecular
phylogeny?
A) metazoan and eumetazoan
B) radial and bilateral
C) true coelom and pseudocoelom
D) protostome and deuterostome
E) molting and lack of molting
37) The last common ancestor of all bilaterians is thought to have had four Hox genes. Most extant
cnidarians have two Hox genes, except Nematostella (of β-catenin fame), which has three Hox genes. On
the basis of these observations, some have proposed that the ancestral cnidarians were originally
bilateral and, in stages, lost Hox genes from their genomes. If true, this would mean that
A) Radiata should be a true 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 Acoela as the basal bilaterians.
E) Two of the responses above are correct.
38) Which of these, if true, would support the claim that the ancestral cnidarians had bilateral
symmetry?
1. Cnidarian larvae possess anterior-posterior, left-right, and dorsal-ventral aspects.
2. Cnidarians have fewer Hox genes than bilaterians.
3. All extant cnidarians, including Nematostella, are diploblastic.
4. β-catenin turns out to be essential for gastrulation in all animals in which it occurs.
5. All cnidarians are acoelomate.
A) 1 only
B) 1 and 4
C) 2 and 3
D) 2 and 4
E) 4 and 5
39) Some researchers claim that sponge genomes have homeotic genes, but no Hox genes. If true, this
finding would
A) strengthen sponges’ evolutionary ties to the Eumetazoa.
B) mean that sponges must no longer be classified as animals.
C) confirm the identity of sponges as “basal animals.”
D) mean that extinct sponges must have been the last common ancestor of animals and fungi.
E) require sponges to be reclassified as choanoflagellates.
Art Questions
The previous figure shows a chart of the animal kingdom set up as a modified phylogenetic tree. Use the
diagram to answer the following questions.
40) Which group contains diploblastic organisms?
A) I
B) II
C) III
D) IV
E) V
41) Which two groups are most clearly represented in the Ediacaran fauna?
A) I and II
B) I and III
C) II and IV
D) II and V
E) IV and V
42) Which of these is the basal group of the Eumetazoa?
A) I
B) II
C) III
D) IV
E) V
43) Which two groups have members that undergo ecdysis?
A) I and II
B) II and III
C) III and IV
D) III and V
E) IV and V
13
A: Morphological phylogeny.
B: Molecular phylogeny.