Question 1

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

Accepted Answer

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

Question 2

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 ________.

Accepted Answer

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

Question 3

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?

Accepted Answer

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

Question 4

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

Accepted Answer

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

Question 5

Which of the following is a feature of the "tube-within-a-tube" body plan in most animal phyla?

Accepted Answer

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.

Question 6

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

Accepted Answer

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

Question 7

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.

Accepted Answer

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.

Question 8

Which of the following statements concerning animal taxonomy is accurate?

Accepted Answer

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.

Question 9

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?

Accepted Answer

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.

Question 10

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

Accepted Answer

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

Question 11

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?

Accepted Answer

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

Question 12

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

Accepted Answer

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.

Question 13

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

Accepted Answer

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

Question 14

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?

Accepted Answer

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.

Question 15

What do all deuterostomes have in common?

Accepted Answer

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.

Question 16

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 ________.

Accepted Answer

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

Question 17

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

Accepted Answer

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

Question 18

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 ________.

Accepted Answer

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

Question 19

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?

Accepted Answer

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.

Question 20

Use the table to answer the following question.

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 four organisms and observe them in detail, making the notations found in the figure.
Which organism would you classify as an animal?

Accepted Answer

A)  organism A 
B)  organism B 
C)  organism C 
D)  organism D

Exam 32: An Overview of Animal Diversity

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