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EXPLORING LIFE
EXERCISE 9:
THE ANNELIDS AND
THE MOLLUSKS
Exercise 9: The Annelids and the Mollusks
Workbook Contents
Corresponding Section on CD
Vocabulary
Key Concepts
Introduction
1. Introduction
The Animal Kingdom
Characteristics of Animals
Animal Cells
Early Evolution of the Animals
Protostomes and Deuterostomes
2. The Animal Kingdom
2A. Overview
2B. Animal Cells
2C. Early Evolution of the Animals
2D. Protostomes and Deuterostomes
The Annelids
Anatomy of the Earthworm
The Class Polychaeta
The Class Oligochaeta
The Class Hirudinea
3. The Annelids
3A. Anatomy of the Earthworm
3B. The Polychaetes
3C. The Oligochaetes
3D. The Hirudinea
The Mollusks
The Origin and Evolution of the Mollusca and the
Basic Body Parts Common Among Mollusks
The Classes of the Mollusca
4. The Mollusks
4A. Origin and Evolution of Mollusks
4B. The Basic Body Plan
4C. Classes of the Mollusca
Summary & Review
Vocabulary
Archenteron - The cavity in the gastrula which forms the embryonic gut
Blastopore - The opening from the outside into the archenteron of the gastrula
Blastula - The hollow ball of cells formed early in embryonic development
Clitellum - The swollen, paler section of skin that produces mucus and is important in reproduction in many
annelids
Coelom - The cavity within the body formed by splitting of the mesoderm in protostomes and by outpocketing
in the deuterostomes
Determinate/indeterminate cleavage - In determinate development or cleavage, the fates of cells in terms of
function and location in the adult organism are determined early in the process of development
of the embryo. In indeterminate development or cleavage, cells in the early stages of embryonic
development are totipotent; they can take on many different functions and locations in the adult
organism.
Detritus - Remaining fragments of dead organisms; dead organic matter
Deuterostome - An animal whose development produces the mouth as a second opening following gastrulation;
the echinoderms and chordates develop in this way
Dioecious - Having separate sexes, with male and female functions occurring in separate individuals
9-1
Ectoderm - The outer layer of tissue in multicellular animals
Endoderm - The inner layer of tissue in multicellular animals, forming, for example, the inner epithelium of
digestive and respiratory tracts
Epitoky - The occurrence of a special reproductive stage in the life cycle of some annelids
Gastrula - The stage of embryonic development at which invagination of the blastula has formed a "cup-like"
stage
Hermaphroditic - A reproductive strategy in which both male and female reproductive structures and functions
are combined in a single individual
Hirudin - A substance in the saliva of leeches that prevents coagulation of blood at the site of attack in its host
Integument - A covering or coating layer in an animal
Lumen - The cavity of an organ
Mesenchyme - The mass of tissue between the ectoderm and endoderm of a gastrula
Mesoderm - The embryonic tissue layer lying between the ectoderm and endoderm; from it such things as
muscles develop
Metamerism - A body plan in which the body is constructed of a number of more or less similar segments
Mosaic development - A pattern of development in which the fates and functions of cells in the adult organism
are determined early in embryonic development
Nephridia - A general term for the excretory organs of invertebrates
Osphradium - A sense organ sensitive to chemicals in the environment; this form of chemosensory structure is
associated with the gills of mollusks
Parapodia - The paired, lateral appendages of each segment of the Polychaete body; their functions may include
locomotion and gas exchange
Pelagic - Inhabiting open water, usually the ocean, but the meaning has been broadened to include fresh water
Periphyton - The plants and animals living on the surfaces of rooted aquatic plants
Peritoneum - The membrane lining the surfaces of the body cavity, i.e., covering both internal organs and
abdominal walls
Pharynx - The tube forming the anterior part of the digestive tract; in some species it may be everted to capture
prey
Pheromone - A hormone-like chemical which affects other individuals rather than organs and tissues within the
individual producing it
Protandry - A reproductive strategy in which the male parts of a hermaphrodite mature and function before the
female parts
Protostome - an animal in which the first opening (or blastopore) of the gastrula becomes the mouth of the adult
animal; annelids, mollusks, and arthropods develop in this way
Pseudocoel - The space between the mesoderm of the body wall and the internal organs formed from the
blastocoel of the embryo; it is not formed within the mesoderm as are the true coeloms of
protostomes and deuterostomes
Pygidium - The anal segment of annelids; also the terminal segment of a number of arthropods, including
beetles, fleas and scale insects
Rynchocoel - The most primitive form of body cavity, found in the Nemertea (ribbon worms), it forms a cavity
around the proboscis
Septum - A barrier separating two segments, as in the bodies of annelids
Setae - The hairs or bristles extending from the lateral margins of annelid bodies, particularly important for
locomotion in oligochaetes; also the hairs or bristles formed as extensions of the exocuticles of
insects
Sodium pump - The energy-dependent, coupled molecular pump (a membrane protein) that exchanges sodium
and potassium across the cell membrane against their concentration gradients
Torsion - The twisting of the gastropod body by 180 degrees during development
Zygote - The diploid cell formed by the fusion of male and female gametes at fertilization
9-2
KEY CONCEPTS
This section of the workbook is set up to help you note important
information relating to the key concepts of this exercise and then organize
and summarize the information in order to develop a synthesis and prepare
for a review. As you complete this exercise, you will focus on the
structural and life cycle characteristics of the animals, particularly the
simple ones, so that you will be able to distinguish:
What is an animal?
1. What structural and life cycle characteristics distinguish animals from
all other organisms?
2. What are the evolutionary trends in development in the structural and
life cycle characteristics of the animals, particularly the simple ones?
How are the lower animals classified?
3. What structural and life cycle characteristics distinguish each group of
animals from every other group?
4. What structural and life cycle characteristics distinguish each class of
animals within a group from every other class within that group?
The first twelve pages are questions that can be answered by following the
progression of slides and paying careful attention to the information, both
visual and audio. These questions should be read in advance of each
section so that you can be better prepared to answer them by knowing
what you are looking for. The underlined subheadings correspond to the
sections of the exercise as outlined in the main menu. Italicized
subheadings denote a series of slides within a larger section.
The subsequent five pages are designed to help you summarize and
synthesize the pertinent information to answer the questions posed above.
9-3
THE ANIMAL KINGDOM
Introduction
1. Circle the characteristic in each group that is common to all members of the animal kingdom. You will
have to listen to the audio and read the screen to complete this question.
a. All animals are multicellular / unicellular.
b. All animals have a cell membrane and a cell wall / a cell membrane only.
c. All animals obtain nutrition by eating other organisms or their remains / photosynthesis; in
other words, all animals are autotrophic / heterotrophic and do / do not have chloroplasts.
2. Match each group of animals with its type of developmental pattern: (D) deuterstomes or (P) protostomes.
annelids
arthropods
chordates
echinoderms
mollusks
The Animal Kingdom
Characteristics of Animals
3. Label the phylogenetic tree with the following terms: ancestral protists, Parazoa, Eumetazoa, Porifera
(sponges), Radiata, Ctenophores, Cnidaria, Bilateria, Protostomes, Annelids, Mollusks, Arthropods,
Deuterostomes, Echinoderms, Chordates
4. List the common name(s) and one characteristic for each of the groups:
a. Porifera:
b. Ctenophores:
c. Cnidaria:
d. Annelids:
e. Mollusks:
f. Arthropods:
g. Echinoderms:
h. Chordates:
9-4
KEY CONCEPTS
5. What are the defining characteristics of each taxon that you must become familiar with? List them:
a.
b.
c.
d.
e.
f.
g.
Animal Cells
6. What are the implications of each of the differences between animal and plant cells? Describe them:
a. Animal cells lack chloroplasts, so animals must survive by
.
Some are mobile / stationary filter feeders while others are mobile / stationary and require
location. Energy consumption in animals is higher / lower than it is in plants, so animals require
less / more oxygen.
.
b. Animal cells lack rigid cells walls, so animal cells can
This permits animal bodies to be less / more flexible and makes locomotion impossible /
possible. What are some animal cells that move within their bodies? List at least two and explain why
their ability to move is important
The absence of cell walls means that animals need another mechanism to give their bodies some
. What are the three strategies that animals use for this purpose?
c. The plasma membrane is important in controlling
of the cell.
Animal cells control osmotic pressure by means of a potassium / sodium pump.
Early Evolution of the Animals
7. Describe how each animal group evolved from the ancestral protists and the characteristics of each group:
a. Porifera: Body plan is / is not symmetric, they do not have / have tissues and organs, and there
is great / little functional integration among cells. The sponges are the most advanced /
primitive of the animals.
b. Radiata: Animals in this group are bilaterally / not / radially symmetric and have one / two
/ three embryonic tissue layers.
9-5
THE ANIMAL KINGDOM
c. Bilateria: These animals all have one / two / three embryonic tissue layers and generally exhibit
bilateral
/ no / radial symmetry.
d. Rotifera: All are large / small, most are aquatic / terrestrial, and they draw food into their
mouths with cilia / flagella arranged in a structure called the
.
e. Nematoda: Many roundworms are free-living / parasitic in the soil while others are free-living /
parasitic on other organisms.
f. Nemertea: Ribbonworms are the most advanced / primitive phylum having a body cavity, called
the pseudocoelom / rhynchocoel in this group. It is / is not used for movement.
g. Platyhelminthes: Some flatworms are free-living / parasitic and have evolved / lost sensory
structures to aid in food finding. Others have adapted to a free-living / parasitic
lifestyle and have increased / reduced sensory structures. Since food is readily
available, these flatworms, which include tapeworms and flukes, have increased /
reduced guts, while most of the body volume is taken up with digestive /
Flatworms
Roundworms
9. Match each label with the correct structure on one or both diagrams of this flatworm:
ectoderm – epidermis
mesoderm – mesenchyme
endoderm
pharynx
gastroventricular
diverticulum
9-6
have intestinal tube
have digestive sac
hermaphroditic
sexes separate
no body cavity or
coelom
have body cavity called
pseudocoel
two tissue layers
three tissue layers
size and speed less
restricted
size and speed restricted
cells obtain oxygen and
remove wastes through
diffusion
organs for oxygen
transport and waste
excretion
Mark an "X"
under each
characteristic
that is found
in the
following
groups:
anus present
8.
mouth present
reproductive organs.
KEY CONCEPTS
10. Match each label with the correct structure on one or both diagrams of these roundworms.
Gender:
Gender:
dorsal nerve cord
pseudocoel
uterus
ovary
testis
intestine
longitudinal muscle layer
ventral nerve cord
Protostomes and Deuterostomes
11. Number each step in the developmental process, then match it with its description:
Step
Description
zygote begins dividing, forming a solid ball of cells
blastula forms, with fluid-filled cavity called blastocoel
gastrulation begins; true coelom is formed within
mesoderm and lined with the peritoneum
archenteron forms as gastrulation continues; blastopore
forms as opening to outside; three tissue layers apparent
12. Match each statement with the corresponding developmental pattern: (D) deuterostome or (P) protostome.
mesoderm forms around lip of the blastopore
cleavage is radial
mesoderm forms from the gut wall
cleavage is determinate
coelom arises by outgrowth from the gut
cleavage is indeterminate
coelom forms by splitting mesoderm
cells are initially totipotent
blastopore becomes the anus
mosaic development
blastopore becomes the mouth
regulative development
cleavage is spiral
have a true coelom
9-7
THE ANNELIDS AND MOLLUSKS
The Annelids
Anatomy of the Earthworm
13. The worms of the phylum Annelida are (circle one) flat / ribbon-like / rounded / segmented.
They are bilaterally / radially symmetric and do / do not have a true coelom.
14. Match the labels with the diagrams of the earthworm:
epidermis
mouth
brain
coelom
pharynx
heart
crop
testis
ovary
septum
dorsal blood vessel
nephridium
intestine
ventral blood vessel
ventral nerve cord
segmented ganglia
longitudinal muscle layer
circular muscle layer
setae
15. Describe how an earthworm moves. Be sure to differentiate between the functions of the circular and
longitudinal muscles:
EC What is the importance of segmentation (metamerism) in the evolution of animals?
9-8
KEY CONCEPTS
The Class Polychaeta
16. Circle the term(s) or phrase(s) on each line that best describe the structural or lifestyle features of this class:
Habitats
a. mostly marine or marine and freshwater or some terrestrial
Habits
b. crawl along bottom or free-swimming or burrowing
Anatomy
c. external movement – parapodia or tentacles or suckers
d. setae – many or few or none
e. external sensory – eyes or antenna or palps or groups of cells (no organs)
Gas Exchange
f. “gills” or moist integument or hemoglobin
Locomotion
g. none (sessile as adults) or “rowing” or segmental contraction
Feeding
h. predatory or filter or suspension or deposit or scavenging or parasitic
Reproduction
i. dioecious or hermaphroditic
j. special reproductive form:
k. fertilization – internal or external
The Class Oligochaeta
17. Circle the term(s) or phrase(s) on each line that best describe the structural or lifestyle features of this class:
Habitats
a. mostly marine or mostly freshwater or some terrestrial
Habits
b. crawl along bottom or free-swimming or burrowing
Anatomy
c. external movement – parapodia or setae or tentacles or suckers
d. setae – many or few or none
Locomotion
e. none (sessile as adults) or “rowing” or segmental contraction
f. special muscles for locomotion:
Anatomy
and
g. internal – septa or sphincters or no separation of segments
h. external – epidermal pores or no pores
Gas Exchange
i. “gills” or moist integument or hemoglobin
Anatomy
j. circulatory system – open or closed
k. digestive system structures:
Feeding
l. predatory or filter or suspension or deposit or scavenging or parasitic
Anatomy
m. nervous system structures:
n. external sensory – eyes or antenna or palps or groups of cells (no organs)
Reproduction
o. dioecious or hermaphroditic
p. protandric or not protandric
q. special reproductive structures:
r. fertilization – internal or external
9-9
THE ANNELIDS AND MOLLUSKS
The Class Hirudinea
18. Circle the term(s) or phrase(s) on each line that best describe the structural or lifestyle features of this class:
Habitats
a. mostly marine or marine and freshwater or some terrestrial
Feeding
b. predatory or filter or suspension or plant-eating or scavenging or parasitic
Gas Exchange
f. “gills” or moist integument or hemoglobin
Anatomy
c. external movement – parapodia or tentacles or suckers
Reproduction
d. dioecious or hermaphroditic
e. special reproductive structures:
Anatomy
f. internal – septa or sphincters or no separation of segments or sinuses
g. setae – many or few or none
Locomotion
h. “rowing” or segmental contraction or sucker attachment
Habits
b. crawl along bottom or free-swimming or burrowing
Feeding
i. special structures:
Anatomy
j. nervous system structures:
Reproduction
k. protandric or not protandric
l. fertilization – internal or external
19. Reviewing each of the previous sections, list and describe at least two example organisms from each class:
a. Polychaeta:
b. Oligochaeta:
c. Hirudinea:
The Mollusks
The Origin and Evolution of the Mollusca & the Basic Body Parts Common Among Mollusks
20. Number, in order from 1 to 5, the possible evolutionary steps of the mollusks:
radula to scrape surfaces for food
rapid evolution of diversity in Cambrian period
spicules expanded into plates over dorsal surface
spicules of calcium carbonate in dorsal surface
worm-like, partially segmented ancestor
9-10
KEY CONCEPTS
21. Match each structure with its description and its location on each diagram by placing the corresponding
letter in the blanks provided:
A. shell
contains digestive, excretory and circulatory systems
B. mantle
contains most sensory organs and mouth
C. digestive system
digests food and absorbs nutrients
D. visceral mass
encases gills
E. head
helps circulate water around gills
F. gills
protects body
G. radula
responsible for locomotion; secretes mucous
H. mantle cavity
scrapes food off of surfaces
I. foot
secretes shell
9-11
THE ANNELIDS AND MOLLUSKS
22. Number, from 1 to 11, the steps in mollusk eating and digestion.
cilia draw food-mucus strings into stomach
larger particles formed into fecal pellets
fecal pellets are expelled through anus
larger particles pass into intestines
food becomes entangled in mucus from salivary
glands
small particles digested intracellularly
food-mucus passes as strings through esophagus to
stomach
small particles pass into digestive gland
stomach acids break down mucus
strings form protostyle in stomach
food scraped from surface by radula
EC Describe the structure and function of the nervous system. You may include labeled diagrams. Use an
additional sheet of paper if needed.
23. True or False: The mollusk shell expands by active secretion along its inside edge.
True or False: The shell increases in both size and thickness simultaneously.
The Classes of the Mollusca
24. Circle the term(s) or phrase(s) on each line that best describe the structure or lifestyle features of each class.
You may want to work on Question #25 at the same time.
Anaplacophora
Taxonomy
a. major class or minor class
Habitats
b. primarily marine or marine and freshwater or some terrestrial
Anatomy
c. head – distinct or indistinct, poorly developed or none
d. foot – none or compressed or present or modified into tentacles
e. mantle or no mantle
Shell Structure
f. none/embedded spicules or single valve or double valve or reduced internal
Anatomy
g. feeding – radula or beak
Feeding
h. scrape algae/herbivorous or carnivorous or scavenge or parasitic
Reproduction
i. hermaphroditic or dioecious
9-12
KEY CONCEPTS
Question #24 continued:
Monoplacophora
Taxonomy
a. major class or minor class
Shell Structure
b. none or single cap or 8 plates or tusk-like or single valve
Habitats
c. primarily marine or marine and freshwater or some terrestrial
Anatomy
d. gills – reiterated or not reiterated or replaced by lungs
Reproduction
e. hermaphroditic or dioecious
Locomotion
f. creep on foot or burrow or “jet-propelled” or sessile (none as adults)
g. foot – none or compressed or present or modified into tentacles
Anatomy
h. anus and gills – to rear or to front
Polyplacophora
Taxonomy
a. less than 200 species or more than 200 species
Shell Structure
b. none or 8 plates or single valve or double valve or reduced internal
Habitats
c. primarily marine or marine and freshwater or some terrestrial
Anatomy
d. feeding – radula or beak
Feeding
e. scrape algae/herbivorous or carnivorous or scavenge or parasitic
Locomotion
f. creep on foot or burrow or “jet-propelled” or sessile (none as adults)
Anatomy
g. foot – none or compressed or present or modified into tentacles
h. mantle or no mantle
i. head – distinct or indistinct, poorly developed or none
j. eyes or no eyes
Reproduction
k. hermaphroditic or dioecious
Anatomy
l. sensory organs - well developed or limited
Scaphopoda
Taxonomy
a. less than 200 species or more than 200 species
Shell Structure
b. none or tusk-like or single valve or double valve or reduced internal
Habitats
c. primarily marine or marine and freshwater or some terrestrial
Locomotion
d. creep on foot or burrow or “jet-propelled” or sessile (none as adults)
Feeding
e. scrape algae or grasp with tentacles or scavenge or parasitic
Anatomy
f. eyes or no eyes
Reproduction
g. hermaphroditic or dioecious
9-13
THE ANNELIDS AND MOLLUSKS
Question #24 continued:
Bivalvia
Shell Structure
a. none or single valve or double valve or reduced internal
Anatomy
b. foot – none or compressed or present or modified into tentacles
Locomotion
c. creep on foot or burrow or “jet-propelled” or sessile (none as adults)
Habitats
d. primarily marine or marine and freshwater or some terrestrial
Feeding
e. scrape algae or filter or grasp with tentacles or scavenge or parasitic
Anatomy
f. gills – reiterated or not reiterated or replaced by lungs
g. head – distinct or indistinct, poorly developed or none
h. sensory organs - well developed or limited
i. mantle or no mantle
j. tentacles or no tentacles
Reproduction
k. hermaphroditic or dioecious
l. protandric or not protandric
Gastropoda
Taxonomy
a. less than 200 species or more than 200 species
Habitats
b. primarily marine or marine and freshwater or some terrestrial
Anatomy
f. head – distinct or indistinct, poorly developed or none
h. anus and gills – to rear (posterior) or to front (anterior)
Shell Structure
e. none or single spiral valve or double valve or reduced internal
Locomotion
d. creep on foot or burrow or “jet-propelled” or sessile (none as adults)
g. foot – none or compressed or present or modified into tentacles
Anatomy
j. mantle or no mantle
k. gills – reiterated or not reiterated or replaced by lungs
l. sensory organs - well developed or limited
m. eyes or no eyes
Feeding
f. herbivorous or filter or suspension or carnivorous or scavenge or parasitic
Anatomy
i. feeding – radula or beak
Reproduction
o. hermaphroditic or dioecious
9-14
KEY CONCEPTS
Question #24 continued:
Cephalopoda
Anatomy
a. head – distinct or indistinct, poorly developed or none
Shell Structure
b. none or single valve or double valve or reduced internal
Anatomy
c. foot – none or compressed or present or modified into tentacles
Habitats
d. primarily marine or marine and freshwater or some terrestrial
Feeding
e. herbivorous or grasp with tentacles/carnivorous or scavenge or parasitic
Anatomy
f. feeding – radula or beak
Locomotion
g. creep on foot or burrow or “jet-propelled” or sessile (none as adults)
Anatomy
h. brain – ring of ganglia or well-developed and encased
i. sensory organs - well developed or limited
j. eyes or no eyes
25. Review the section on mollusk classes. List and describe at least one example organism from each of the
classes.
a. Aplacophora:
b. Monoplacophora:
c. Polyplacophora:
d. Scaphopoda:
e. Bivalvia:
f. Gastropoda:
g. Cephalopoda:
9-15
SUMMARY & REVIEW
1. What are the three characteristics that unite all animals in terms of their:
b. cell structure:
a. structure:
c. nutrition acquisition:
Evolutionary Trends
2. In each group, list the characteristics of the animals in order from most primitive to most derived. The
first one has been done for you as an example:
a. symmetry: asymmetrical to radial symmetry to bilateral symmetry
b. tissues and organs:
to
c. embryonic tissue layers:
to
d. habitats:
to
e. body cavity:
to
to
f. sensory structures:
to
to
3. Without looking at your Key Concepts, fill in the following phylogenetic tree:
5. Write the letter of the phylum next to the appropriate common name and organism:
A. Porifera
comb jelly
B. Cnidaria
flatworm
C. Ctenophora
jelly fish
D. Rotifera
ribbon worm
E. Nemertea
rotifer
F. Nematoda
roundworm
G. Platyhelminthes
sponge
9-16
THE ANIMAL KINGDOM; THE ANNELIDS AND MOLLUSKS
6. Complete each statement with the appropriate word or phrase for each developmental pattern:
Protostomes
Deuterostomes
a. mesoderm forms:
b. coelem forms:
c. blastopore becomes (mouth or anus):
d. cleavage is (spiral or radial):
e. cleavage is (determinate or indeterminate):
f. development is (mosaic or regulative):
7. What is metamerism? What is its significance? With what phylum/group does this characteristic first appear?
8. What characteristics are unique to each of the phyla of “worms”?
a. Nemertea:
b. Nematoda:
c. Platyhelminthes:
d. Annelida:
9. After you fill out the table on the next page, list the characteristics that are unique to each class of Annelida:
a. Polychaeta:
b. Oligochaeta:
c. Hirudinea:
10. What characteristic(s) do primitive mollusks share with annelids?
9-17
SUMMARY & REVIEW
Habitats
mostly marine
mostly freshwater
mostly terrestrial
Habits
crawl along bottom
free-swimming
burrowing
Feeding
predatory
filter-feeding
suspension-feeding
deposit-feeding
deitritus/scavenging
parasitic
plant-eating
Locomotion
none - sessile as adults
"rowing"
segmental contraction
sucker attachment
Gas Exchange
"gills"
moist integument
hemoglobin
Reproduction
dioecious - sexes separate
epitoky
hermaphroditic but not protandric
hermaphroditic and protandric
clitellum
albumin-filled cocoon formed
external fertilization
internal fertilization
Anatomy
External - sensory
eyes
antenna
palps
groups of cells - no organs
External - movement
parapodia
setae - many
setae - few
setae - none
"tentacles"
sucker(s)
External & internal - digestive
"jaws"
mouth
gizzard
crop
pharynx
proboscis
salivary glands
intestines
nephridia
anus
Other external & internal
septa
sphincters
epidermal pores
cerebral ganglia
segmental ganglia
ventral nerve cord
closed circulatory system
longitudinal muscles
circular muscles
9-18
Hirudinea
Oligochaeta
Polychaeta
Hirudinea
Oligochaeta
Polychaeta
Mark an "X" next to each characteristic that is found in all or some of the members of each of these classes.
THE ANIMAL KINGDOM; THE ANNELIDS AND MOLLUSKS
11. In each group, list the characteristics of the mollusks in order from most primitive to most derived. The
first one has been done for you as an example:
a. taxonomy: few species to many species
to
b. habitats:
c. shell structure:
to
d. head:
to
e. mantle:
to
to
f. gills:
to
g. sensory structures:
to
to
to
to
h. “brain” :
12. After you fill out the table on the next page, list the characteristics that are unique to each class of Mollusca:
a. Anaplacophora:
b. Monoplacophora:
c. Polyplacophora:
d. Scaphopoda:
e. Bivalvia:
f. Gastropoda:
g. Cephalopoda:
13. Write the letter of the phylum next to the appropriate common name and organism:
A. Polychaeta
“few seta”
B. Oligochaeta
“head foot”
C. Hirudinea
leeches
D. Anaplacophora
“many plates”; chitons
E. Monoplacophora
“many seta”
F. Polyplacophora
“no plates”
G. Scaphopoda
“one plate”
H. Bivalvia
“stomach foot”
I. Gastropoda
tooth or tusk shells
J. Cephalopoda
“two valves”
9-19
Taxonomy
minor class; under 200 species
major class; over 200 species
Habitats
marine only or primarily
marine and freshwater
some terrestrial representatives
Feeding
scrape algae off rocks with radula
filter feed
grasp food with tentacles
herbivorous
carnivorous
scavenge
parasitic
suspension feed
Locomotion
creep on foot
burrow
"jet-propelled"
sessile (do not move as adults)
Shell Structure
no shell; may have imbedded spicules
shell single cap from union of spicules
segmented shell of 8 plates
shell is cylinder or cone, tusk-like
single valve shell
double valve shell
reduced internal shell
External Anatomy
distinct head
no head, head indistinct or poorly developed
tentacles
no tentacles
foot
no foot or compressed foot
anus and gills to rear
anus and gills to front (via torsion)
Internal Anatomy - Viscera
radula
beak
mantle
no mantle
reiterated gills, muscles, excretory structures
gills, muscles, excretory structures not reiterated
gills replaced by lungs
Internal Anatomy - Nervous and Sensory
sensory organs limited
sensory organs well developed
eyes
no eyes
"brain" a ring of ganglia
well-developed brain
Reproduction
hermaphroditic; may be protandric
dioecious
9-20
Cephalopoda
Gastropoda
Bivalvia
Scaphopoda
Polyplacophora
Monoplacophora
Aplacophora
Cephalopoda
Gastropoda
Bivalvia
Scaphopoda
Polyplacophora
Monoplacophora
Mark an "X" next to each
characteristic that is found in all or
some of the members of each of
these classes.
Aplacophora
SUMMARY & REVIEW
9-21