Annelids and Mollusks Study Guide

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Multiple Choice
Identify the choice that best completes the statement or answers the question.

Which of the following is not a characteristic of at least some mollusks?

a.	a pseudocoelomate body plan
b.	bilateral symmetry
c.	a mantle
d.	an open circulatory system

Which of the following has a true coelom?

a.	flatworm	c.	rotifer
b.	roundworm	d.	mollusk

The evolution of a coelom was significant because

a.	more food could be stored within it.
b.	more wastes could be stored before excretion.
c.	it enabled development of more complex organ systems.
d.	it eliminated the need for a circulatory system.

mollusks : a mantle ::

a.	pseudocoelomate animals : true body cavities
b.	roundworms : single-opening digestive tract
c.	roundworms : coelom
d.	mollusks : a coelom

The cilia of a trochophore

a.	allow attachment to the ocean bottom.
b.	create currents for drawing in food.
c.	cover the entire larval body.
d.	are necessary for reproduction.

Trochophores

a.	occur in some mollusks’ life cycles.
b.	possess a belt of cilia around their bodies.
c.	occur in some annelids’ life cycles.
d.	All of the above

A characteristic structure found in many mollusks is the radula, which is involved in

a.	jet propulsion.	c.	eating.
b.	opening and closing of the shell.	d.	reproduction.

Which of the following is a correct pairing?

a.	phylum Platyhelminthes—hydra
b.	phylum Nematoda—planaria
c.	phylum Mollusca—octopus
d.	phylum Annelida—roundworm

All of the animal phyla that evolved after the mollusks

a.	are vertebrates.	c.	have a coelom.
b.	are prokaryotes.	d.	lack mesoderm.

All of the following are classes of the phylum Mollusca except

a.	bivalves.	c.	gastropods.
b.	cephalopods.	d.	pseudopods.

Which of the following mollusks have a closed circulatory system?

a.	snails	c.	slugs
b.	cephalopods	d.	gastropods

Refer to the illustration above. Which two organisms have mantles?

a.	1 and 3	c.	1 and 4
b.	2 and 3	d.	2 and 4

Jet propulsion is the usual means of locomotion in water for

a.	octopuses.	c.	squids.
b.	gastropods.	d.	bivalves.

Refer to the illustration above. This organism is a

a.	bivalve.	c.	trochophore.
b.	cephalopod.	d.	gastropod.

Refer to the illustration above. Movement of this organism is dependent upon structure

a.	1.	c.	3.
b.	2.	d.	None of the above

Shells of mollusks

a.	may consist of one or more pieces.
b.	provide protection.
c.	allow for the attachment of muscles.
d.	All of the above

Adductor muscles are responsible for

a.	moving the valves of bivalves.
b.	extending the feet of mollusks.
c.	pumping the hearts of mollusks.
d.	fanning the gills of aquatic mollusks.

In an open circulatory system,

a.	water is drawn into the mantle cavity to provide oxygen to body tissues.
b.	lungs branch into small tubules to provide oxygen to tissues.
c.	wastes are eliminated directly to the environment from the tissues.
d.	blood is released directly into spaces in the body tissues.

Twisting of the visceral mass of gastropods is called

a.	extension.	c.	torsion.
b.	inversion.	d.	conversion.

Among the various species of gastropods, respiration may take place

a.	with gills.
b.	through the skin.
c.	within the mantle cavity.
d.	All of the above

All of the cephalopods

a.	have eight tentacles.
b.	are predators.
c.	possess protective shells.
d.	are filter feeders.

Jet propulsion in a squid is the result of

a.	rapid closing of the organism’s shell.
b.	strong contractions of the tentacles.
c.	high-pressure discharge of fluid from the organism’s mouth.
d.	the pumping of water through the siphon.

The only cephalopod that has retained its external shell is the

a.	cuttlefish.	c.	octopus.
b.	chambered nautilus.	d.	squid.

Segmented worms are known as

a.	nematodes.	c.	planarians.
b.	annelids.	d.	arthropods.

Each segment of an annelid

a.	is capable of reproduction.
b.	has a well-developed brain that allows the annelid to learn simple tasks.
c.	has a pseudocoelom.
d.	may contain some organ systems that duplicate systems in other segments.

An example of segmentation in humans is the

a.	digestive system.	c.	vertebral column.
b.	skin.	d.	brain.

The most significant evolutionary advancement of annelids over mollusks is believed to be

a.	the ability to burrow.	c.	segmentation.
b.	the existence of a true coelom.	d.	cephalization.

Refer to the illustration above. Which two organisms have segmented body plans?

a.	3 and 4	c.	1 and 4
b.	2 and 4	d.	2 and 3

true coelom : mollusks and annelids ::

a.	tentacle : annelids	c.	valve : annelids
b.	siphon : annelids	d.	segmentation : annelids

Coordinated movements of an earthworm’s body segments are possible because of the

a.	development of an advanced brain.
b.	ventral nerve cord and ganglia that carry impulses to the muscles.
c.	presence of a true coelom in the earthworm’s body.
d.	existence of a complete digestive system.

earthworm movement : circular muscles and setae ::

a.	earthworm digestion : circular muscles and setae
b.	earthworm digestion : seminal receptacles
c.	earthworm reproduction : pharynx
d.	earthworm respiration : skin

Small tubules that collect wastes from the coelom of annelids and discharge the wastes from the body are called

a.	nephridia.	c.	bivalves.
b.	radulae.	d.	spicules.

The digestive tube of the earthworm is divided into three regions. Which of the following is not among these regions?

a.	crop	c.	radula
b.	intestine	d.	gizzard

Which of the following is (are) not part of an earthworm’s body?

a.	a heart	c.	nephridia
b.	gills	d.	a typhlosole

The clitellum of an earthworm

a.	contains the heart.
b.	is associated with reproduction.
c.	acts as a primitive respiratory system.
d.	is necessary for movement.

Earthworms are considered to be beneficial to the environment because

a.	they help release nutrients into the soil.
b.	they aerate the soil as they move through it.
c.	they break up the soil in which they live.
d.	All of the above

squid motion : siphon ::

a.	annelid motion : siphon
b.	annelid breathing : nephridia
c.	earthworm circulation : closed circulatory system
d.	annelid motion : tentacles

The body of the water leech

a.	has suckers on the front and back.	c.	is segmented.
b.	has no parapodia.	d.	All of the above

Leeches

a.	use suckers to aid in movement.	c.	are segmented.
b.	may be parasitic.	d.	All of the above

leeches : blood ::

a.	earthworms : small animals
b.	earthworms : blood
c.	marine polychaetes : small animals
d.	marine polychaetes : blood

Completion
Complete each statement.

The ____________________ larva is a characteristic of some mollusks and annelids.

Constant beating of ____________________ in the mantle cavity of a clam causes a continuous stream of water to pass over the gills.

A tonguelike scraping organ used by some mollusks in feeding is called the ____________________.

An organ known as the ____________________ is an abrasive, tonguelike structure found in some mollusks.

A snail can pull its head into its mantle cavity because the cavity has moved to the anterior of the animal during a twisting process called ____________________ that occurs during development.

Water is drawn into the body of a clam through tubes called ____________________.

A bivalve’s shells close when the pair of ____________________ contract.

Structures in earthworms that function as simple kidneys are called ____________________.

The only living cephalopod that has retained its external shell is the _________________________.

Snails and slugs belong to the class of mollusks called ____________________.

Earthworms belong to the phylum ____________________.

Refer to the illustration above. Structure X is the ventral ____________________ cord.

In anterior segments of annelids, several ganglia are fused to form the ____________________, which is the brain of these organisms.

An earthworm’s ____________________ produces a tube made of mucus and chitin that contains the eggs and sperm and allows development of an earthworm’s offspring.

Bristles that exist along the sides of an annelid are called ____________________.

Some leeches are ____________________; they feed on the blood of other animals.

The ____________________ are annelids that have many setae and parapodia, generally live in marine environments, and have antennae.