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Answers to Text Questions
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Inquiry Questions

None for this chapter.

Self Test

1). Which feature is not characteristic of the animals?
    a). multicellular heterotrophs
    b). sexual reproduction
    c). embryonic development
    d). cell walls
Answer: d

2). Most of the phyla of the animal kingdom are found
    a). on land.
    b). in the ocean.
    c). burrowing underground.
    d). in freshwater habitats.
Answer: b

3). The subkingdom of animals that lack symmetry and have no true tissues or organs is the
    a). Eumetazoa.
    b). Radiata.
    c). Parazoa.
    d). Bilateria.
Answer: c

4). Except for the Radiata, the eumetazoans
    a). lack true tissues and organs.
    b). are monoblastic.
    c). are diploblastic.
    d). are triploblastic.
Answer: d

5). Cnidarians and ctenophorans differ from other eumetazoans by having
    a). radial symmetry.
    b). bilateral symmetry.
    c). major organ systems.
    d). three tissue layers.
Answer: a

6). The advantage of bilateral symmetry is that it allowed for the evolution of
    a). appendages.
    b). cephalization.
    c). reproductive structures.
    d). parasites.
Answer: b

7). Members of which group are not deuterostomes?
    a). chordates
    b). echinoderms
    c). arthropods
    d). none of these, all are deuterostomes
Answer: c

8). The evolution of an internal body cavity offered an advantage in animal body design in all areas except
    a). circulation.
    b). digestion.
    c). freedom of movement.
    d). gamete storage.
Answer: a

9). The segments of annelids are
    a). apparent in the embryo but not in the adult.
    b). specialized for different functions.
    c). most obvious in the mesoderm (muscles) but not in the ectoderm.
    d). repetitive-each able to develop a complete set of adult organs.
Answer: d

10). Which of the following hypotheses about the origin of metazoans is supported by ribosomal RNA analysis?
    a). the multinucleate hypothesis
    b). the colonial flagellate hypothesis
    c). the polyphyletic origin hypothesis
    d). None of these; rRNA analysis doesn't support any specific hypothesis.
Answer: b

Test Your Visual Understanding

1). Which of these drawings (a or b) depicts a radially symmetrical animal? Which depicts a bilaterally symmetrical animal? Although a radially symmetrical animal can be bisected into equal halves in any two-dimensional plane, can you describe a plane of orientation of a radially symmetrical animal that produces dissimilar halves (Refer to the planes of bisection in b.)?
Answer: The radially symmetrical is the sea anemone in a and the bilaterally symmetrical animal is the squirrel in b. A radially symmetrical animal can be bisected into equal halves in any two-dimensional plane in the vertical direction but not necessarily through a horizontal plane, like the frontal plane in b. Many radially symmetrical animals, like jellyfish or hydra, have a dorsal and ventral part of the body, such that a plane that bisects through the dorsal/ventral axis of the body would produce dissimilar halves.

Apply Your Knowledge

1). In what ways is an earthworm more complex than a flatworm?
Answer: An earthworm, in the Annelida phylum, is a coelomate and a flatworm; in the Platyhelminthes phylum, is an acoelomate. The presence of a body cavity in the earthworm allows for specialization of the internal organs, compared to the flatworm. The coelom also leads to the evolution of a circulatory system in the earthworm that is not present in the flatworm. The reproductive organs and gametes in the earthworm are also larger and more diverse, which expands the reproductive strategies used by earthworms compared to flatworms.

2). Why is it believed that echinoderms and chordates, which are so dissimilar, are members of the same evolutionary line?
Answer: Chordates and echinoderms shared a very key characterization of animal taxonomy—that of embryo growth pattern. These two groups comprise the deuterostomes whose embryological development differs greatly from the protostomes (mollusks, annelids, and arthropods). These embryological developmental patterns are guided by genetic differences in the expression of Hox genes, which suggests that echinoderms and chordates share a key characteristic very distinct from other animal groups. And, although the adult echinoderms look very different from the chordates, an earlier stage in their development looks more closely related to the chordates.

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