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The intromittent organ of male cephalopods is the


A) pedipalp, a modified labial palp.
B) hectocotylus, a modified arm.
C) aedeagus, a modified beak.
D) penis, the first structure homologous to the mammalian reproductive structure.
E) baculum, a modified piece of internal shell.

F) B) and D)
G) None of the above

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Some prosobranchs have only one _____________ in their mantle cavity.


A) Shell
B) Foot
C) Gill
D) Radula
E) Tentacle

F) A) and B)
G) B) and E)

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A Nautilus differs from a snail because


A) the snail body occupies the whole shell and the Nautilus mainly lives in the last chamber.
B) the Nautilus is the last representative of a once flourishing group while snails belong to a most abundant modern group.
C) the Nautilus generates gas in the chambers for buoyancy during swimming and a snail does not.
D) All of the choices are differences
E) None of the choices are correct

F) B) and C)
G) A) and C)

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Which of the following statements is NOT TRUE of cephalopods?


A) Most have color vision
B) Visual acuity underwater surpasses that of humans
C) Can be taught to discriminate between shapes
D) Sensory systems are more elaborate than in other molluscs
E) Brain is the largest of any invertebrate

F) A) and D)
G) B) and C)

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Molluscs with a tubular shell that open at both ends are in the class _____________________.

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Because shells require it,land snails are limited to soils that contain some level of


A) aluminum.
B) silica.
C) calcium.
D) sodium.
E) carbon.

F) C) and D)
G) A) and B)

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The _________ is the oldest part of the shell and growth occurs in concentric rings around it.

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The ______________ is the layer on the outside of the clam or mussel shell that provides protection from acidic water and may be colored to hide the clam in the mud.

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The newest clam shell is built


A) on the outside so the periostracum is the newest material.
B) on the inside so the inside nacreous layer is the newest.
C) both directions outward from the central prismatic layer.
D) all at once; all layers of shell are the same age.
E) None of the choices are correct

F) B) and E)
G) A) and B)

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Although snails and some other molluscs are hermaphroditic,most molluscs are either male or female,a condition called


A) asexual.
B) sexual.
C) monoecious.
D) dioecious.
E) parthenogenetic.

F) A) and B)
G) D) and E)

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The shell of Polyplacophora is divided into _______ _______ valves.

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The cephalopod nervous system is best described as


A) absent.
B) primitive and very little advanced from that of a cnidarian.
C) the most advanced among molluscs.
D) more complex than ours.
E) None of the choices are correct

F) B) and D)
G) A) and D)

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The Scaphopoda


A) lack a shell.
B) lack a mantle.
C) live in fresh water.
D) pursue prey in a manner similar to squid.
E) lack gills.

F) D) and E)
G) None of the above

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Torsion


A) involves movement of the shell independent of visceral movements.
B) rotates the shell between 90 and 180 degrees.
C) begins with the contraction of an asymmetrical foot retractor muscle.
D) shifts the anus from posterior to the right side of the body.
E) All of the choices are correct

F) A) and C)
G) B) and E)

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The caudofoveates


A) are mostly worm-like, burrowing, marine organisms.
B) possess an oral shield associated with food selection and intake.
C) possess a radula (reduced in some species) .
D) may have more features in common with the common ancestor of all molluscs than any other living group.
E) All of the choices are correct

F) A) and E)
G) All of the above

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The circulatory system of cephalopods is more efficient than other molluscs because it has accessory or ________ _______ at the base of each gill.

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The Polyplacophora


A) have a coiled shell.
B) live in the ocean, especially in intertidal areas.
C) lack gills.
D) lack a radula.
E) All of the choices are correct

F) D) and E)
G) A) and E)

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When cephalopods hatch from their eggs,they are


A) trochophore larvae.
B) glochidial parasites.
C) helpless, sessile larvae that must metamorphose into adult forms.
D) juveniles that resemble small adults.
E) There is much variation and all of the above occur among the various cephalopods

F) A) and E)
G) C) and D)

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The solenogastres


A) live free on the sea bottom and feed on cnidarians.
B) have a shell of eight articulating plates.
C) resemble the squids.
D) are called chitons.
E) have the primitive radula and gill mollusc plan.

F) A) and B)
G) A) and E)

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How does torsion differ from coiling? Fully explain your answer.

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Answered by ExamLex AI

Answered by ExamLex AI

Torsion and coiling are both methods of ...

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