Deck 16: Molluscs

Question 1

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

Answer 1

B

Question 2

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.

Answer 2

A

Question 3

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

Answer 3

E

Question 4

Snails were discovered in the Negev desert at night,harvesting the lichens that grew in the moist pores of the limestone and wearing down the desert more than abrasion from wind.Scientists studying these snails added mild acid to the snail feces and it foamed; this was an important test to detect that

A) the snails digested and derived nutrition from breakdown of the limestone rock.
B) the snail was excreting uric acid.
C) some limestone was actually scraped off and ingested with the lichen.
D) the lichen had some food value.
E) not all food was digested.

Question 5

In some molluscs,the free-swimming larva is a trochophore while in others,it is a veliger with the beginnings of a foot,shell and mantle.What is the relationship of these molluscan juvenile stages?

A) A veliger is found strictly in terrestrial molluscs
B) The trochophore is considered ancestral and the veliger is a derived larval stage
C) The two larval forms represent two early and distinct branches of molluscs
D) The veliger is ancestral and the trochophore is a derived larval stage
E) Only the cephalopods have the veliger stage; all other molluscs have a trochophore stage

Question 6

The genus _____________ contains some members that have a toxin strong enough to kill humans.

A) Tegelu
B) Cyphom
C) Halioti
D) Conus
E) Neopilina

Question 7

To prevent taking back in the wastes it has just expelled,a standard sediment-inhabiting bivalve mollusk should position itself

A) with the incurrent siphon upstream.
B) with the excurrent siphon upstream.
C) in any direction, since it can control which way the water flows in either siphon.
D) either with the incurrent siphon upstream or with the excurrent siphon upstream, but not in any direction, since it can control which way the water flows in either siphon.
E) None of the choices are correct

Question 8

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

Question 9

The radula

A) not only rasps off fine food particles but also serves as a conveyor belt to carry food toward the digestive tract.
B) replaces worn teeth by secreting new teeth at the posterior end.
C) varies in number, pattern, and form of teeth, allowing species to be classified by this trait.
D) may be modified to bore through hard materials.
E) All of the choices are correct

Question 10

Early gastropods had a coiled shell that did not twist to the right or left; this bilaterally symmetrical shell is called

A) sinistral.
B) planospiral.
C) conispiral.
D) dextral.
E) scaphopodal.

Question 11

The central axis around which the shell of a snail coils is called the

A) aperture.
B) columella.
C) sinistral.
D) dextral.
E) torsion.

Question 12

The nudibranchs belong to the

A) scaphopoda.
B) pelecypoda.
C) prosobranchia.
D) opisthobranchia.
E) pulmonata.

Question 13

Clams burrow by using

A) adductor muscles.
B) cilia action.
C) gills for jet propulsion.
D) a modified radula.
E) a foot.

Question 14

Some prosobranchs have only one _____________ in their mantle cavity.

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

Question 15

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

Question 16

The Monoplacophora

A) lack a shell.
B) live in fresh water.
C) lack a foot.
D) have several internal organs that are serially repeated.
E) All of the choices are correct

Question 17

Where would you locate the coelomic cavity when dissecting a mollusk such as a clam?

A) The coelom is between the mantle and the shell
B) The coelom is all of the area enclosed by the two shells and exposed when you open the shell
C) The cavity around the heart, the kidneys, and the lumen of the gonads forms the limited coelom
D) The cavities inside the siphon are the coelom
E) The coelom is the space inside small tubules that form the gills

Question 18

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.

Question 19

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.

Question 20

Which correctly describes the evolutionary origin and adaptive radiation of molluscs?

A) Molluscs originated in freshwater and invaded both terrestrial and marine environments
B) Molluscs originated on land, all classes then invaded both freshwater and marine environments
C) Molluscs originated on land, all classes then invaded freshwater and the bivalves and gastropods invaded marine environments
D) Molluscs originated in the sea, both bivalves and gastropods invaded marine environments and the land
E) Molluscs originated in the sea, bivalves and gastropods invaded brackish and freshwater environments, and just gastropods invaded the land

Question 21

Cephalopods feed on

A) microscopic organisms.
B) fish, molluscs, crustaceans, and worms.
C) seaweed.
D) whales and porpoises.
E) None of the choices are correct

Question 22

Snails that lack gills are called "pulmonate" and their mantle cavity functions

A) for propulsion.
B) to produce pearls.
C) as a lung.
D) to store wastes.
E) All of the choices are correct functions

Question 23

The membranes that hold the internal organs in place in coelomates are called ______________.

Question 24

Gaseous exchange in gastropods may involve

A) gills.
B) lungs.
C) mantle.
D) body surface.
E) All of the choices are correct

Question 25

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.

Question 26

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

Question 27

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.

Question 28

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.

Question 29

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

Question 30

A pair of _______________ serve as sense organs for sampling water and are found in the mantle grooves near the anus of many chitons.

Question 31

The main structures that taste food and direct it into the mouth of a clam is/are

A) the gills.
B) labial palps.
C) the siphons.
D) the gastric mill.
E) adductor muscles.

Question 32

The circulatory system of cephalopods is more efficient than that of other molluscs because

A) it places the systemic circulation before the gills.
B) it is a closed network of vessels.
C) all blood is circulated through the gill filaments.
D) accessory or brachial hearts increase blood pressure before blood flows through the gills.
E) All of the choices are correct

Question 33

The water current in the body of a cephalopod mollusc provides

A) oxygen for respiration.
B) jet power for rapid locomotion.
C) a means of carrying wastes and gametes out of the body.
D) All of the choices are cephalopod uses for their body water currents
E) None of the choices are correct

Question 34

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

Question 35

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

Question 36

The tongue-like,rasping organ in the head of many molluscs is the _____________.

Question 37

The internal organs in coelomates are covered with a mesodermal epithelium called the _______________.

Question 38

Cultured pearls are made by

A) cutting spherical balls from the thick shell of oysters and polishing them into circular beads.
B) dropping a grain of sand into the incurrent siphon of a pearl oyster.
C) tying off the labial palps.
D) growing oysters in high-calcium waters where they produce the pearls as unfertilized eggs.
E) placing an irritating particle under the shell mantle.

Question 39

Most freshwater clams have a bivalve ___________ stage that attaches to the gills and lives as a parasite for a few weeks.

A) Veliger
B) Trochophore
C) Brachial
D) Miracidia
E) Glochidia

Question 40

Of all of the freshwater organisms,more freshwater clams are becoming endangered than other species.What is the likely reason?

A) They are a primitive animal and they are due for natural extinction
B) The shellfish industry has moved inland and we are overharvesting them for human food
C) Clams are more heavily parasitized than any other molluscan group
D) As filter-feeders, they concentrate pollutants and are more likely to be harmed by water pollution
E) All of the choices are correct

Question 41

Most cephalopods have an ink gland that secretes ______________,a dark fluid containing melanin,to confuse enemies.

Question 42

Among living molluscs,the ancestral condition is most nearly approached by the class _____________.

Question 43

What surface (e.g.,dorsal,ventral,anterior,posterior)of the squid faces forward as the animal moves by jet propulsion? What surface faces forward in a swimming cuttlefish? Explain your answers.

Question 44

Opisthobranchs and pulmonates are both gastropods.What are their main distinguishing features?

Question 45

You find an old living freshwater clam.The health department would like to check a small sample of the shell for pollutant levels when it was young.Where should they remove this oldest shell material?

Question 46

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

Question 47

Scaphopods have a captacula or head with long tentacles; how do they differ from the tentacles of cephalopods? Are these two types of tentacles homologous?

Question 48

Give the supporting evidence that shows that the molluscs share a common ancestor with the annelids.

Question 49

How has the problem of "fouling" been resolved by the various groups of molluscs?

Question 50

The ________ _________ projects into a bivalve stomach to keep the contents whirling while releasing digestive enzymes.

Question 51

How do you account for the enormous radiation of the molluscs? Give factual support for your answer.

Question 52

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

Question 53

Cephalopod eyes and vertebrate eyes are anatomically similar. Evaluate whether or not the similarity is a case of homology or analogy. State your reasoning.

Question 54

The scaphopods have a shell that resembles a straightened gastropod shell.Why are they not classified with the gastropods?

Question 55

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

Question 56

What are the morphological features that distinguish the ammonoids from the nautiloids?

Question 57

The shell of Polyplacophora is divided into _______ _______ valves.

Question 58

Describe five features,morphological or developmental,that would most likely be found in the earliest ancestral mollusc.

Question 59

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