1. Which of the following did NOT occur during the Cambrian Explosion?
Animals acquired specialized cells, tissues, and organs.
There was an extraordinary growth in animal diversity.
Animals evolved simpler body plans.
Animal appendages became specialized for a variety of functions. 1 2 3 4 5

2. was flat and plate-shaped. had a hard shell.
Paleontologists discover the fossil of an animal that lived 570 million years ago. This animal probably
was flat and plate-shaped.
had a hard shell.
was organized into a front and a back end.
lived on land. 1 2 3 4 5

3. One characteristic that made early animals different from all animals of today was their
habitat.
body segmentation.
body plan.
bilateral symmetry. 1 2 3 4 5

4. The diversity of invertebrate phyla underwent its greatest increase
before the Cambrian Period.
during the Cambrian Period.
after the Cambrian Period.
both before and after the Cambrian Period. 1 2 3 4 5

5. Animals of the Cambrian Period typically had all of the following EXCEPT
body symmetry.
segmentation.
some type of skeleton.
a backbone. 1 2 3 4 5

6. an armored worm a jellyfish a snail a clam
Biologists trace the evolution of invertebrate groups by studying their appearance in the fossil record. For which invertebrate would this type of study be most difficult?
an armored worm
a jellyfish
a snail
a clam 1 2 3 4 5

7. Which of the following group of invertebrates are deuterostomes?
worms
arthropods
mollusks
echinoderms 1 2 3 4 5

8. The classification of an animal as a deuterostome or a protostome is based on
its body symmetry.
whether or not it has a coelom.
what happens to the blastopore.
the number of germ layers it has. 1 2 3 4 5

9. In a protostome, the blastopore becomes a(an)
mouth.
anus.
zygote.
blastula. 1 2 3 4 5

10. A body cavity that forms between the germ layers is called a(an)
coelom.
blastopore.
mesoderm.
ectoderm. 1 2 3 4 5

11. An acoelomate is an animal that has
a body cavity lined with endoderm and ectoderm.
a body cavity partially lined with mesoderm.
a body cavity completely lined with mesoderm.
no body cavity between the germ layers. 1 2 3 4 5

12. Some type of body symmetry is found in all invertebrates EXCEPT
cnidarians.
mollusks.
sponges.
flatworms. 1 2 3 4 5

13. Which invertebrates exhibit radial symmetry?
cnidarians and echinoderms
sponges and flatworms
roundworms and annelids
mollusks and arthropods 1 2 3 4 5

14. Cephalization refers to the
division of the body into upper and lower sides.
concentration of sense organs and nerve cells in the front of the body.
joining together of specialized cells to form tissues.
formation of a body cavity between the germ layers. 1 2 3 4 5

15. Animal X has no coelom and no cephalization. Animal X is either a
mollusk or an arthropod.
flatworm or a roundworm.
mollusk or an echinoderm.
sponge or a cnidarian. 1 2 3 4 5

16. Animal Y has three germ layers, bilateral symmetry, and no coelom
Animal Y has three germ layers, bilateral symmetry, and no coelom. Animal Y is a(an)
sponge.
arthropod.
flatworm.
mollusk. 1 2 3 4 5

17. In Figure 29–1, the space labeled X is called a
protostome.
deuterostome.
coelom.
pseudocoelom. 1 2 3 4 5

18. One animal that has a body construction like that shown in Figure 29–1 is a
flatworm.
roundworm.
sponge.
jellyfish. 1 2 3 4 5

19. Which of the following characteristics is NOT found in any radially symmetrical invertebrate?
cephalization
specialized cells
specialized organs
a coelom 1 2 3 4 5

20. One way to distinguish a roundworm from an annelid is to
count their germ layers.
examine their body symmetry.
compare the structure of their body cavities.
determine whether they have cephalization. 1 2 3 4 5

21. Which sequence correctly expresses the order in which major invertebrate features evolved?
three germ layers ® tissues ® multicellularity ® coelom
coelom ® tissues ® three germ layers ® multicellularity
multicellularity ® tissues ® three germ layers ® coelom
multicellularity ® three germ layers ® coelom ® tissues 1 2 3 4 5

22. Which of the following invertebrates has a closed circulatory system, nephridia, and a hydrostatic skeleton?
an echinoderm
an annelid
a flatworm
a sponge 1 2 3 4 5

23. If an animal has a digestive tract, an open circulatory system, and an exoskeleton, it could be a(an)
arthropod.
echinoderm.
cnidarian.
roundworm. 1 2 3 4 5

24. Invertebrates that break down their food through intracellular digestion include
annelids.
mollusks.
arthropods.
sponges. 1 2 3 4 5

25. Which invertebrate has a gastrovascular cavity?
arthropod
mollusk
cnidarian
roundworm 1 2 3 4 5

26. A true digestive tract is found in
annelids.
sponges.
cnidarians.
flatworms. 1 2 3 4 5

27. One difference between a gastrovascular cavity and a digestive tract is that
a gastrovascular cavity has specialized regions, but a digestive tract does not.
a gastrovascular cavity has one opening, and a digestive tract has two.
digestion is extracellular in a gastrovascular cavity and intracellular in a digestive tract.
food can be processed more efficiently in a gastrovascular cavity than in a digestive tract. 1 2 3 4 5

28. Gases diffuse most efficiently across a respiratory membrane if the membrane is
thick and dry.
thin and dry.
thick and moist.
thin and moist. 1 2 3 4 5

29. Which of these invertebrates exchange gases through gills?
insects
spiders
clams
land snails 1 2 3 4 5

30. In insects, gas exchange takes place through a network of
tracheal tubes.
mantle cavities.
book lungs.
blood vessels. 1 2 3 4 5

31. Most flatworms are small and very thin
Most flatworms are small and very thin. Therefore, they can supply their cells with oxygen and remove metabolic wastes by means of
simple diffusion between body surface and the environment.
an open circulatory system without a heart.
an open circulatory system with one heart.
a closed circulatory system with one heart. 1 2 3 4 5

32. The distinguishing feature of a closed circulatory system is that
it does not include a heart.
blood is contained within vessels that extend throughout the body.
blood is kept at low pressure.
blood is circulated less efficiently than in an open circulatory system. 1 2 3 4 5

33. In an open circulatory system, blood
never leaves the heart.
does not come in direct contact with the tissues.
is always contained within a system of blood vessels.
is pumped through a system of sinuses. 1 2 3 4 5

34. An example of an animal with an open circulatory system is a(an)
sponge.
cnidarian.
arthropod.
annelid. 1 2 3 4 5

35. The giant squid is a large, very active invertebrate
The giant squid is a large, very active invertebrate. What type of circulatory system do you think it has?
open circulatory system
closed circulatory system
water vascular system
no circulatory system 1 2 3 4 5

36. Which of the following is a function of an excretory system?
eliminating nitrogenous wastes from the body
exchanging oxygen and carbon dioxide with the environment
gathering and processing information from the environment
obtaining and digesting food 1 2 3 4 5

37. Which structures are NOT part of an excretory system?
flame cells
spiracles
Malpighian tubules
nephridia 1 2 3 4 5

38. What would happen to a flatworm if its flame cells stopped functioning?
It would be unable to pump blood.
It would accumulate urea.
It would swell.
It would dry up. 1 2 3 4 5

39. Which of the following best describes uric acid?
more toxic than ammonia, leaves the body through excretory pores
more toxic than ammonia, leaves the body through the rectum
less toxic than ammonia, leaves the body through excretory pores
less toxic than ammonia, leaves the body through the rectum 1 2 3 4 5

40. process food more efficiently. reduce water loss.
Expelling uric acid from the body and having a respiratory surface that is covered with mucus are two ways that some invertebrates can
process food more efficiently.
reduce water loss.
respond to their environment.
supply oxygen to their cells. 1 2 3 4 5

41. The eyespots of flatworms can
detect the presence of light.
detect motion.
detect color.
form images. 1 2 3 4 5

42. An example of an invertebrate with a hydrostatic skeleton is a(an)
spider.
sponge.
sea star.
earthworm. 1 2 3 4 5

43. An endoskeleton is a shell of a mollusk.
fluid-filled body cavity that supports the muscles.
structural support located inside the body.
hard body covering made of chitin. 1 2 3 4 5

44. Which of the following invertebrates would be most likely to reproduce by external fertilization?
an arachnid
an insect
a land snail
a cnidarian 1 2 3 4 5

45. Which statement refers to sexual reproduction?
All offspring are genetically identical to the parent.
Offspring are produced from the fusion of male and female gametes.
An organism breaks into pieces that grow into new individuals.
New individuals are produced from outgrowths of the parent’s body wall. 1 2 3 4 5

46. Animals with skeletons were more numerous in the Cambrian Period than in earlier periods. _________________________
True
False 1 2 3 4 5

47. Mollusks are classified as pseudocoelomates. _________________________
True
False 1 2 3 4 5

48. During early development, the zygote divides repeatedly to form a hollow ball of cells called a blastopore. _________________________
True
False 1 2 3 4 5

49. In deuterostomes, the blastopore forms a(an) mouth
True
False 1 2 3 4 5

50. Arthropods have bilateral symmetry. _________________________
True
False 1 2 3 4 5

51. The only deuterostomes with radial symmetry are cnidarians
True
False 1 2 3 4 5

52. The difference between a coelomate and a pseudocoelomate has to do with the lining of the body cavity. _________________________
True
False 1 2 3 4 5

53. An animal that feeds on other animals by swallowing them whole is most likely to use intracellular digestion. _________________________
True
False 1 2 3 4 5

54. Animal A has a respiratory surface area of 50 mm2, and animal B has a respiratory surface area of 25 mm2. If other features of their respiratory surfaces are the same, the rate of gas exchange will be greater in animal A. _________________________
True
False 1 2 3 4 5

55. Book lungs and tracheal tubes are used for breathing in terrestrial invertebrates. _________________________
True
False 1 2 3 4 5

56. If an animal’s blood never comes in direct contact with its tissues, the animal has an open circulatory system. _________________________
True
False 1 2 3 4 5

57. The excretory system of animal X functions to conserve body water while removing nitrogenous wastes. Animal X most likely lives on land. _________________________
True
False 1 2 3 4 5

58. Muscles work by becoming longer. _________________________
True
False 1 2 3 4 5

59. Arthropods have an endoskeleton. _________________________
True
False 1 2 3 4 5

60. The eruption of a volcano creates a new island in the ocean
The eruption of a volcano creates a new island in the ocean. Animals that settle on the island can increase in number most rapidly if they reproduce asexually. _________________________
True
False 1 2 3 4 5

61. Participant Scores Participant 1 Participant 2 Participant 3
Participant 1
Participant 2
Participant 3
Participant 4
Participant 5

62. ____________________ fossils are tracks and burrows made by soft-bodied animals whose bodies were not fossilized. 1 2 3 4 5
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63. Over the course of evolution, ____________________ allowed animals to increase in body size with a minimum of new genetic material. 1 2 3 4 5
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64. The only invertebrates that lack both cephalization and a coelom are cnidarians and ____________________. 1 2 3 4 5
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65. A body cavity lined partially with mesoderm is called a(an) _________________________.1 2 3 4 5
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66. The opening in the blastula is known as the ____________________.1 2 3 4 5
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67. Echinoderms differ from cnidarians in that echinoderms develop from three ____________________ layers. 1 2 3 4 5
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68. Most invertebrates that rely on rapid movement for survival have ____________________ symmetry.1 2 3 4 5
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69. A digestive tract is a _________________________ that is open at both ends.1 2 3 4 5
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70. If an invertebrate has gills, it most likely lives in a(an) ____________________ environment.1 2 3 4 5
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71. Figure 29–2

72. In Figure 29–2, the structure labeled X is called a(an) ____________________.1 2 3 4 5
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73. The function of the structure labeled X in Figure 29–2 is to rid the body of excess ____________________. 1 2 3 4 5
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74. The simplest nervous systems are called ____________________.1 2 3 4 5
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75. If an animal moves by contracting muscles that surround a body cavity filled with fluid, the animal has a(an) ____________________ skeleton. 1 2 3 4 5
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76. In some invertebrates, eggs are fertilized outside the female’s body
In some invertebrates, eggs are fertilized outside the female’s body. This type of fertilization is known as _________________________ fertilization. 1 2 3 4 5
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77. An individual that can produce both male and female gametes is called a(an) ____________________.1 2 3 4 5
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78. Why are animal fossils more abundant from the Cambrian Period than from earlier periods?1 2 3 4 5
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79. Name three invertebrate phyla with bilateral symmetry.1 2 3 4 5
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80. Animal Z has three germ layers, a true coelom, and cephalization
Animal Z has three germ layers, a true coelom, and cephalization. Which invertebrate phyla could animal Z could be a member of? 1 2 3 4 5
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81. What is a blastopore? 1 2 3 4 5
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82. What characteristic related to development makes echinoderms different from all other invertebrates?1 2 3 4 5
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83. Explain the advantage of cephalization.1 2 3 4 5
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84. What is the definition of a coelomate?1 2 3 4 5
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85. What is intracellular digestion?1 2 3 4 5
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86. Why must the surfaces of respiratory systems be moist?1 2 3 4 5
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87. Figure 29–3

88. Identify each circulatory system shown in Figure 29–3 as open or closed.1 2 3 4 5
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89. What do the arrows represent in Figure 29–3?1 2 3 4 5
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90. Why must all animals eliminate ammonia from their bodies?1 2 3 4 5
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91. What can you infer about the habitat of an invertebrate that eliminates nitrogenous wastes in the form of uric acid? 1 2 3 4 5
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92. Which of the three main kinds of skeletal systems would be least likely to function properly in an animal that is severely dehydrated? 1 2 3 4 5
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93. Explain why budding does not maintain genetic diversity in a population.1 2 3 4 5
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94. The animals that existed before the Cambrian Period were probably very simple. Describe two ways in which these animals may have obtained nutrients. 1 2 3 4 5
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95. Explain how studying the development of invertebrates can provide information that is useful in classifying invertebrates. 1 2 3 4 5
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96. Describe the changes in internal specialization that occurred during the evolution of animals.1 2 3 4 5
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97. Compare and contrast cnidarians, mollusks, and echinoderms in terms of body symmetry, presence of a body cavity, and cephalization. 1 2 3 4 5
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98. Describe the structure of a book lung, and explain why this structure is well suited for gas exchange. 1 2 3 4 5
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99. In some animals, blood can be distinguished from extracellular fluid, which is the liquid solution that surrounds the cells of an animal’s body. Explain why such a distinction is possible for animals with a closed circulatory system but not for animals with an open circulatory system. 1 2 3 4 5
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100. To remove nitrogenous wastes, some terrestrial invertebrates convert ammonia to urea. Why is that advantageous for these invertebrates? 1 2 3 4 5
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101. Describe the organization of nervous systems in cnidarians, flatworms, and cephalopod mollusks.1 2 3 4 5
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102. Contrast hydrostatic skeletons, exoskeletons, and endoskeletons in terms of their structures.1 2 3 4 5
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103. When individuals in a population are few and widely scattered, hermaphrodites might have a better chance of reproducing sexually than animals that have separate sexes. Explain why. 1 2 3 4 5
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