Name: _____________________________________________
MOLLUSKS
Read the figure below, which covers topics from your textbook. Answer the questions that
follow.
Features of Three Classes of Mollusks
Class
Gastropoda
Bivalvia
Cephalopoda
External shell
one (some species)
two
none (most species)
Head
yes
no
yes
Radula
yes
no
yes
Locomotion
crawling (most)
sessile (most)
rapid swimming
Read each question and write your answer in the space provided.
SKILL: Organizing Information
1. Based on the entries in the column labeled “External shell,” how do bivalves differ from
gastropods and cephalopods?
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2. What are two features that bivalves lack but gastropods and cephalopods possess? ________
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Read the question and write your answer in the space provided.
SKILL: Vocabulary Development
2. What is the meaning of the term locomotion in the table?____________________________
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Circle the letter of the word that best completes the analogy.
4. Bivalvia is to sessile as Cephalopoda is to
a. crawling.
b. swimming.
c. jumping.
d. Both (a) and (b)
What is a coelomate?
Which bivalve has eyes
and can swim?
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Modern Biology
Mollusca
Explain the relationship between the terms in each of the following pairs of terms.
1. visceral mass, mantle _________________________________________________________
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2. hemolymph, hemocoel ________________________________________________________
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3. incurrent siphon, excurrent siphon _______________________________________________
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MULTIPLE CHOICE Write the correct letter in the blank.
____ 1. One advantage of a coelom over a pseudocoelom is that a coelom
a. contains fluid while a pseudocoelom does not.
b. is completely surrounded by endoderm.
c. eliminates the need for a circulatory system.
d. allows body wall muscles to contract without hindering digestion.
____ 2. One feature that is shared by many mollusks and annelids is the
a. radula. b. mantle cavity.
c. trochophore. d. pseudopodium.
____ 3. Mollusks in the class Gastropoda
a. lack a distinct head.
c. do not have a hemocoel.
b. have an open circulatory system. d.
are usually sessile.
____ 4. Bivalves have all of the following structures except
a. a radula. b. adductor muscles.c. siphons.
d. gills.
____ 5. An octopus generally moves by
a. pumping a jet of water through its incurrent siphon.
b. crawling along the bottom with its tentacles.
c. gliding on a layer of mucus with the help of cilia.
d. repeatedly opening its valves and snapping them shut.
Answer the questions in the space provided.
1. Identify the two main regions of a typical mollusk’s body. _____________________________
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Which region contains most of the internal organs? __________________________________
Which region is directly involved with locomotion? ___________________________________
2.What is the usual function of the mantle in a snail or clam? _____________________________
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3.Contrast the feeding methods of gastropods and bivalves. _____________________________
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5. A cephalopod called the paper nautilus makes a type of shell with its foot. This shell, which
consists largely of protein, is formed only by the female and is used to protect the eggs. List
four reasons why this shell is not a typical molluskan shell. ____________________________
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STRUCTURES AND FUNCTIONS Identify the structures labeled a–h in the diagram of the
basic body plan of a mollusk shown below.
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Modern Biology
Mollusca
1. True or False: Members of the Phylum Mollusca are among the structurally simplest
multicellular organisms.
2. Mollusks are
a. scavengers
b. carnivores
c. filter-feeders
d. all of the above
3. Which of the following is NOT a characteristic trait of mollusks?
a. a radula
b. a shell
c. a muscular foot
d. tentacles with cnidocytes
4. What is the highest level of organization in mollusks?
a. cellular
b. tissue
c. organ system
d. none of the above
5. True or False? The typical molluscan body plan is greatly modified in some of the molluscan
classes.
6. Mollusks have which type of symmetry?
a. bilateral
b. no symmetry
c. radial
d. pentamerous
Use the Double Bubble to compare and contrast gastropods and cephalopods: