Which of the following did NOT occur during the Cambrian Explosion?

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.

2. 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.

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

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.

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

6. 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

7. Which of the following group of invertebrates are deuterostomes? • worms • arthropods • mollusks • echinoderms

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.

9. In a protostome, the blastopore becomes a(an) • mouth. • anus. • zygote. • blastula.

10. A body cavity that forms between the germ layers is called a(an) • coelom. • blastopore. • mesoderm. • ectoderm.

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.

12. Some type of body symmetry is found in all invertebrates EXCEPT • cnidarians. • mollusks. • sponges. • flatworms.

13. Which invertebrates exhibit radial symmetry? • cnidarians and echinoderms • sponges and flatworms • roundworms and annelids • mollusks and arthropods

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.

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.

16. Animal Y has three germ layers, bilateral symmetry, and no coelom. Animal Y is a(an) • sponge. • arthropod. • flatworm. • mollusk.

17. In Figure 29–1, the space labeled X is called a • protostome. • deuterostome. • coelom. • pseudocoelom.

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

19. Which of the following characteristics is NOT found in any radially symmetrical invertebrate? • cephalization • specialized cells • specialized organs • a coelom

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.

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

22. Which of the following invertebrates has a closed circulatory system, nephridia, and a hydrostatic skeleton? • an echinoderm • an annelid • a flatworm • a sponge

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

24. Invertebrates that break down their food through intracellular digestion include • annelids. • mollusks. • arthropods. • sponges.

25. Which invertebrate has a gastrovascular cavity? • arthropod • mollusk • cnidarian • roundworm

26. A true digestive tract is found in • annelids. • sponges. • cnidarians. • flatworms.

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.

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.

29. Which of these invertebrates exchange gases through gills? • insects • spiders • clams • land snails

30. In insects, gas exchange takes place through a network of • tracheal tubes. • mantle cavities. • book lungs. • blood vessels.

31. 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.

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.

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.

34. An example of an animal with an open circulatory system is a(an) • sponge. • cnidarian. • arthropod. • annelid.

35. 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

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

37. Which structures are NOT part of an excretory system? • flame cells • spiracles • Malpighian tubules • nephridia

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.

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

40. 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.

41. The eyespots of flatworms can • detect the presence of light. • detect motion. • detect color. • form images.

42. An example of an invertebrate with a hydrostatic skeleton is a(an) • spider. • sponge. • sea star. • earthworm.

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.

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

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.

46. Animals with skeletons were more numerous in the Cambrian Period than in earlier periods. _________________________ • True • False

47. Mollusks are classified as pseudocoelomates. _________________________ • True • False

48. During early development, the zygote divides repeatedly to form a hollow ball of cells called a blastopore. _________________________ • True • False

49. In deuterostomes, the blastopore forms a(an) mouth. _________________________ • True • False

50. Arthropods have bilateral symmetry. _________________________ • True • False