Chapter 32 Practice

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

B

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

B

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 governing early development
C) the evolution of meiosis
D) the origin of a brain

B

As you are on the way to Tahiti for a vacation, your plane crash-lands on a previously undiscovered island. You soon find that the island is teeming with unfamiliar organisms, and you, as a student of biology, decide to survey them (with the aid of the Insta-Lab Portable Laboratory you brought along in your suitcase). You select three organisms and observe them in detail, making the notations found in the figure above. Which organism would you classify as an animal?
A) organism A
B) organism B
C) organism C

C

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 it
C) consuming living, rather than dead, prey
D) using enzymes to digest their food

B

Which of the following Tp traits is different from all other known animals?
A) Tp is multicellular.
B) Tp lacks muscle and nerve cells.
C) Tp has cilia.
D) Tp lacks cell walls.

B

What do animals ranging from corals to monkeys have in common?
A) a mouth and an anus
B) number of embryonic tissue layers
C) type of body symmetry
D) presence of Hox genes

D

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 descendents of such adults

A

Which of the following would you classify as something other than an animal?
A) sponges
B) coral
C) jellyfish
D) choanoflagellates

D

The evolution of animal species has been prolific (the estimates go into the millions and 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

C

The last common ancestor of all animals was probably a _____.
A) unicellular chytrid
B) multicellular algae
C) multicellular fungus
D) flagellated protist

D

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

B

Which statement is most consistent with the hypothesis that the Cambrian explosion was caused by the rise of predator-prey relationships? The fossil record reveals an increased incidence of _____.
A) worm burrows
B) larger animals
C) organic material
D) hard parts

D

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

C

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

C

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) vertebrates evolved from arthropods
D) arthropods have had more time to coevolve with land plants than have vertebrates

D

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

A

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

B

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.

D

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.

C

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

A

Among protostomes, which morphological trait has shown the most variation?
A) type of symmetry (bilateral vs. radial vs. none)
B) type of body cavity (coelom vs. pseudocoelom vs. no coelom)
C) number of embryonic tissue types (diploblasty vs. triploblasty)
D) type of development (protostome vs. deuterostome)

B

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.

D

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

C

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.

D

Trichoplax adhaerens (Tp) 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 2000 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. They move using cilia, and any "edge" can lead. Tp 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. Tp sperm cells have never been observed, nor have embryos past the 64-cell (blastula) stage.
26)

On the basis of information in the paragraph above, which of these should be able to be observed in Tp?
A) the act of fertilization
B) the process of gastrulation
C) eggs
D) All three of the listed responses are correct.

C

A student encounters an animal embryo at the eight-cell stage. The four smaller cells that comprise one hemisphere of the embryo seem to be rotated 45 degrees 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

B

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.

B

The most recently discovered phylum in the animal kingdom (1995) is the phylum Cycliophora. It includes three species of 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 sac-like 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)

A

We should expect the inner wall of the swim bladder to be lined with tissue that is derived from _____.
A) ectoderm
B) endoderm
C) mesoderm
D) mesoglea

B

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

A

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.

C

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 and 4
B) 2 and 3
C) 2 and 4
D) 4 and 5

A

An organism that exhibits cephalization probably also _____.
A) is bilaterally symmetrical
B) has a coelom
C) is segmented
D) is diploblastic

A

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.

B

Trichoplax adhaerens (Tp) 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 2000 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. They move using cilia, and any "edge" can lead. Tp 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. Tp sperm cells have never been observed, nor have embryos past the 64-cell (blastula) stage.

Tp’s body symmetry seems to be most like that of _____.
A) most sponges
B) cnidarians
C) worms
D) tetrapods

A

The most recently discovered phylum in the animal kingdom (1995) is the phylum Cycliophora. It includes three species of 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 sac-like 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.

Cycliophorans have two types of larvae. One type of larva is produced when the digestive system of a female is impregnated by a male. The digestive system then collapses and develops into a larva, which swims away in search of a new host after the surrounding female dies. Which is the embryonic tissue that is apparently most important in forming this type of larva?
A) mesohyl
B) mesoderm
C) ectoderm
D) endoderm

D

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 plummules, 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) cephalization
D) identity as lophotrochozoans

C

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 → 1 → 4 → 3
B) 2 → 4 → 1 → 3
C) 2 → 3 → 1 → 4
D) 2 → 1 → 3 → 4

B

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 → 1 → 4
B) 5 → 3 → 4 → 2 → 1
C) 3 → 5 → 4 → 2 → 1
D) 3 → 5 → 2 → 1 → 4

A

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

C

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.

D

The most recently discovered phylum in the animal kingdom (1995) is the phylum Cycliophora. It includes three species of 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 sac-like 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.

Using similarities in embryonic development, body symmetry, and other anatomical features to assign an organism to a clade involves _____.
1. cladistics based on body plan
2. molecular-based phylogeny
3. morphology-based phylogeny
A) 1 only
B) 2 only
C) 3 only
D) 1 and 3

D

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.

D

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.

B

The Hox genes came to regulate each of the following. From earliest to most recent, in what sequence did these events evolve?
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 → 1 → 3
C) 3 → 2 → 1 → 4
D) 3 → 4 → 1 → 2

C

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) the 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) the Cnidaria may someday replace porifera as the basal bilaterians

B

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

B

The most recently discovered phylum in the animal kingdom (1995) is the phylum Cycliophora. It includes three species of 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 sac-like 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

B

The feeding stage of cycliophorans _____.
1. is autotrophic
2. is sessile
3. captures food in a manner similar to that of animals with lophophores
4. shows radial symmetry
A) 1 and 2
B) 1 and 3
C) 2 and 4
D) 1, 2, and 3

D

Which morphological trait evolved more than once in animals, according to the phylogeny based on DNA sequence data found in the figure above?
A) coelom
B) bilateral symmetry
C) segmentation
D) protostome development

C

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) Sequence data can be gathered faster than morphological data, and morphological data provides a different perspective.
C) Morphological changes usually do not result from molecular changes.
D) Some phyla vary too widely in morphological characteristics to be classified accurately.

B

If in the future the current molecular evidence regarding animal origins is further substantiated, 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 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.

B

The most recently discovered phylum in the animal kingdom (1995) is the phylum Cycliophora. It includes three species of 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 sac-like 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 above, to which clade(s) should cycliophorans belong?
1. Eumetazoa
2. Deuterostomia
3. Bilateria
4. Ecdysozoa
5. Lophotrochozoa
A) 1 and 3
B) 1, 3, and 5
C) 2, 3, and 4
D) 2, 3, and 5

B

What conclusion is apparent from the data in the table above?
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.

C

All things being equal, which of these is the most parsimonious explanation for the change in the number of Hox genes from the last common ancestor of insects and vertebrates to ancestral vertebrates, as shown in the table above?
A) The occurrence of seven independent duplications of individual Hox genes.
B) The occurrence of two distinct duplications of the entire seven-gene cluster, followed by the loss of one cluster.
C) The occurrence of a single duplication of the entire seven-gene cluster.

C

Two competing hypotheses to account for the increase in the number of Hox genes from the last common ancestor of bilaterians to the last common ancestor of insects and vertebrates are: (1) a single duplication of the entire four-gene cluster, followed by the loss of one gene, and (2) three independent duplications of individual Hox genes. To prefer the first hypothesis on the basis of parsimony requires the assumption that _____.
A) the duplication of a cluster of four Hox genes is equally likely as the duplication of a single Hox gene
B) there is an actual process by which individual genes can be duplicated
C) genes can exist is spatial groupings called clusters
D) clusters of genes can undergo disruption, with individual genes moving to different chromosomes during evolution

A

In the experiment outlined in the figure above, what would you expect to happen if researchers supplied an enzyme that blocked the expression of the Dll gene?
A) The embryo would have appendages in abnormal locations.
B) The origins of the embryo’s appendages would fluoresce.
C) The developing embryo would have no appendages. D) The embryo’s appendages would be shorter than usual.

C

Dll is a gene known to direct limb development in the fruit fly. Researchers studying this gene have found that it is also expressed in developing appendages in animals from many other phyla, supporting the hypothesis that all animal appendages may be homologous. However, suppose researchers looking at Dll activity had instead found the results shown in the figure above. These results suggest instead that _____.
A) Dll is not actually involved in appendage development
B) appendages evolved separately in protostomes and deuterostomes
C) appendages coevolved with segmentation
D) all animal appendages are homologous

B

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. Animals only reproduce sexually.
5. Animals are thought to have evolved from flagellated protists similar to modern
choanoflagellates.
A) 1 and 2
B) 3 and 5
C) 3, 4, and 5
D) 2 and 4

B