2. There are roughly this many described species in the phylum Mollusca. A) 1,000 B) 10,000 C) 100,000 D) 1 million E) 10 million

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1 Chapter Molluscs are A) deuterostomes. B) ecdysozoaons. C) lophotrochozoans. D) chordates. E) hemichordates. 2. There are roughly this many described species in the phylum Mollusca. A) 1,000 B) 10,000 C) 100,000 D) 1 million E) 10 million 3. The study of similarities and differences in early development of animals is called A) comparative embrology. B) descriptive embryology. C) descriptive anatomy. D) protostomology. E) comparative analogy. 4. The enterocoel hypothesis suggests the coelom may have arisen A) due to determinate cleavage. B) due to a splitting of mesoderm. C) in a spiral manner. D) in a radial manner. E) as outpocketings of the primitive gut. 5. The body of molluscs is divided into two main regions called the A) head-foot and visceral mass. B) mantle and foot. C) head-foot and enterocoel. D) visceral mass and mantle. E) head and foot. 6. The shell of a mollusc is secreted by the A) radula. B) mantle. C) periostracum. D) foot. E) visceral mass. Page 1

2 7. The inner layer of the mollusc shell is the layer. A) radular B) prismatic C) nacreous D) helix E) periostracum 8. The space between the mantle and foot in a mollusc is called the A) hemocoel. B) coelom. C) enterocoel. D) mantle cavity. E) radular cavity. 9. The rasping structure occurring in the mouth of most molluscs is the A) tongue. B) nacre. C) odontophore. D) operculum. E) radula. 10. Snails, slugs, and limpets belong to the molluscan class A) Gastropoda. B) Pelecypoda. C) Polyplacophora. D) Aplacophora. E) Cephalopoda. 11. The 180, counterclockwise twisting of the visceral mass, mantle, and mantle cavity of gastropods is called A) contortion. B) torsion. C) helixing. D) coiling. E) operculating. 12. In gastropods, food is trapped in mucus and incorporated into a rotating mucoid mass called the, which extends to the stomach. A) stylet B) siphonoglyph C) protostyle D) odontophore E) osphradium Page 2

3 13. The class of molluscs that contains the most species is the class A) Aplacophora B) Cephalopoda C) Gastropoda D) Polyplacophora E) Pelecypoda 14. The circulatory system of most molluscs is A) hydraulic. B) incurrent. C) closed. D) excurrent. E) open. 15. Among molluscs, extension of body structures such as tentacles is accomplished by A) a hydraulic skeleton. B) special extensor muscles. C) tendons and ligaments. D) a system of levers. E) muscles and levers. 16. In some gastropods, a(n) is found on the dorsal, posterior margin of the foot and when the foot is drawn into the shell, seals the opening. A) radula B) operculum C) tentacles D) siphons E) osphradium 17. The primary excretory product of aquatic gastropods is A) urine. B) urea. C) ammonia. D) uric acid. E) guanine. 18. The gastropod larval stage in which torsion occurs is called the A) dipleurula. B) pilidium. C) Muller's larva. D) veliger. E) trochophore. Page 3

4 19. Which of the following is not a member of the class Bivalvia? A) clams B) mussels C) oysters D) chitons E) scallops 20. The oldest part of the bivalve shell is the A) umbo. B) periostracum. C) hinge ligament. D) left valve. E) right valve. 21. Muscles responsible for closing the bivalve shell are A) longitudinal. B) adductors. C) retractors. D) circular. E) protractors. 22. The adaptation of bivalves to sedentary, filter feeding life-styles involved loss of the and the radula. A) mantle B) foot C) head D) visceral mass E) siphons 23. In the bivalves, gas exchange takes place through the A) mantle cavity. B) siphons. C) visceral mass. D) gills. E) foot. 24. In the bivalves, final digestion occurs A) in the adductor muscles. B) in the coelom. C) in the labial palps. D) in the crystaline style. E) in the digestive gland. Page 4

5 25. The modified veliger of some freshwater bivalves is called the A) glochidium. B) trochophore. C) pilidium. D) dipleura. E) cercoid. 26. Squids, octopuses, cuttlefishes, and nautili belong to the molluscan class A) Gastropoda. B) Cephalopoda. C) Polyplacophora. D) Bivalvia. E) Pelecypoda. 27. The most complex molluscs belong to the class A) Gastropoda. B) Bivalvia. C) Cephalopoda. D) Polyplacophora. E) Scaphopoda. 28. The only living cephalopods that possess an external shell are the A) scallops. B) cuttlefishes. C) toothshells. D) nautiloids E) squids. 29. Unlike other molluscs, the have a closed circulatory system. A) univalves B) gastropods C) chitons D) bivalves E) cephalopods 30. Cephalopods typically locate prey by A) sight. B) tactile senses. C) olfaction. D) gustation. E) echolocation. Page 5

6 31. The similarity of design between the eyes of vertebrates and the eyes of many cephalopods provides an excellent example of A) divergent evolution. B) convergent evolution. C) perpendicular phylogeny. D) adaptive radiation. E) cladistic phylogeny. 32. Pigment cells of cephalopods are called A) pinacocytes. B) odontophores. C) chromatophores. D) erythrocytes. E) nautilophores. 33. Sperm packets of cephalopods are called A) cecae. B) stylets. C) cocoons. D) spermatophores. E) gonophores. 34. Tooth shells belong to the molluscan class A) Bivalvia. B) Cephalopoda. C) Polyplacophora. D) Gastropoda. E) Scaphopoda. 35. Neopilina represents the molluscan class, that was known only from fossils until A) Monoplacophora B) Aplacophora C) Polyplacophora D) Bivalvia E) Gastropoda 36. Solenogasters are cylindrical molluscs that lack a shell; they belong to the class A) Gastropoda. B) Aplacophora. C) Cephalopoda. D) Scaphopoda. E) Polyplacophora. Page 6

7 37. Chitons belong to the molluscan class A) Monoplacophora. B) Scaphopoda. C) Polyplacophora. D) Cephalopoda. E) Bivalvia. 38. The lack of a in the molluscan class Aplacophora is thought to be a primitive characteristic. A) head B) foot C) visceral mass D) shell E) radula 39. The segmental arrangement of gills, excretory structures, and nervous elements in the, make them seem like a missing link between molluscs and the annelidarthropod line. A) cephalopods B) octopods C) gastropods D) solenogasters E) monoplacophorans 40. The diversity of body forms and life-styles in the phylum Mollusca is an excellent example of A) adaptive radiation. B) convergent evolution. C) emergent evolution. D) parallel evolution. E) homologous evolution. 41. The shell-secreting organ of bivalve mollusks is the A) umbo. B) visceral mass. C) foot. D) mantle. E) crystalline style. 42. The tentacle of male cephalopods that is modified for spermatophore transfer is the A) hectocotylus. B) umbo. C) pneumostome. D) operculum. E) odontophore. Page 7

8 43. Molluscs possess this type of skeleton. A) endoskeleton B) exoskeleton C) pneumo D) hydraulic E) hepatic Page 8