EXPLORING LIFE

EXERCISE 9: THE ANNELIDS AND

THE MOLLUSKS

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Exercise 9: The Annelids and the Mollusks Workbook Contents Corresponding Section on CD Vocabulary Key Concepts Introduction 1. Introduction The Animal Kingdom 2. The Animal Kingdom Characteristics of Animals 2A. Overview Animal Cells 2B. Animal Cells Early Evolution of the Animals 2C. Early Evolution of the Animals Protostomes and Deuterostomes 2D. Protostomes and Deuterostomes The Annelids 3. The Annelids Anatomy of the Earthworm 3A. Anatomy of the Earthworm The Class Polychaeta 3B. The Polychaetes The Class Oligochaeta 3C. The Oligochaetes The Class Hirudinea 3D. The Hirudinea The Mollusks 4. The Mollusks The Origin and Evolution of the Mollusca and the 4A. Origin and Evolution of Mollusks Basic Body Parts Common Among Mollusks 4B. The Basic Body Plan The Classes of the Mollusca 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

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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

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KEY CONCEPTS

This section of the workbook is set up to help you note importantinformation relating to the key concepts of this exercise and then organizeand summarize the information in order to develop a synthesis and preparefor a review. As you complete this exercise, you will focus on thestructural and life cycle characteristics of the animals, particularly thesimple 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 ofanimals within a group from every other class within that group?

The first twelve pages are questions that can be answered by following theprogression of slides and paying careful attention to the information, bothvisual and audio. These questions should be read in advance of eachsection so that you can be better prepared to answer them by knowingwhat you are looking for. The underlined subheadings correspond to thesections of the exercise as outlined in the main menu. Italicizedsubheadings denote a series of slides within a larger section.

The subsequent five pages are designed to help you summarize andsynthesize the pertinent information to answer the questions posed above.

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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:

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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.

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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 /

reproductive organs.

9. Match each label with the correct structure on one or both diagrams of this flatworm:

ectoderm – epidermis

mesoderm – mesenchyme

endoderm

pharynx

gastroventricular diverticulum

8. Mark an "X"under each characteristic that is found in the following groups:

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s pre

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org

ans f

or o

xyge

n tra

nspo

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d w

aste

ex

cret

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n ox

ygen

and

re

mov

e w

aste

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ough

di

ffus

ion

size

and

spee

d re

stric

ted

size

and

spee

d le

ss

rest

ricte

d

thre

e tis

sue

laye

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two

tissu

e la

yers

hav

e bo

dy c

avity

cal

led

pseu

doco

el

no

body

cav

ity o

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elom

sexe

s sep

arat

e

herm

aphr

oditi

c

hav

e di

gest

ive

sac

hav

e in

test

inal

tube

FlatwormsRoundworms

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KEY CONCEPTS 10. Match each label with the correct structure on one or both diagrams of these roundworms.

Gender:

dorsal nerve cord

pseudocoel

uterus

ovary

testis

intestine

longitudinal muscle layer

ventral nerve cord

Gender:

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

mesoderm forms from the gut wall

coelom arises by outgrowth from the gut

coelom forms by splitting mesoderm

blastopore becomes the anus

blastopore becomes the mouth

cleavage is spiral

cleavage is radial

cleavage is determinate

cleavage is indeterminate

cells are initially totipotent

mosaic development

regulative development

have a true coelom

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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?

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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: and

Anatomy 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

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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

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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

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THE ANNELIDS AND MOLLUSKS 22. Number, from 1 to 11, the steps in mollusk eating and digestion.

cilia draw food-mucus strings into stomach

fecal pellets are expelled through anus

food becomes entangled in mucus from salivary glands

food-mucus passes as strings through esophagus to stomach

food scraped from surface by radula

larger particles formed into fecal pellets

larger particles pass into intestines

small particles digested intracellularly

small particles pass into digestive gland

stomach acids break down mucus

strings form protostyle in stomach

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

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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

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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

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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:

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SUMMARY & REVIEW 1. What are the three characteristics that unite all animals in terms of their:

a. structure: b. cell 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

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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?

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SUMMARY & REVIEW Mark an "X" next to each characteristic that is found in all or some of the members of each of these classes.

Pol

ycha

eta

Olig

ocha

eta

Hiru

dine

a

Pol

ycha

eta

Olig

ocha

eta

Hiru

dine

a

Habitats Anatomymostly marine External - sensorymostly freshwater eyesmostly terrestrial antennaHabits palpscrawl along bottom groups of cells - no organsfree-swimming External - movementburrowing parapodiaFeeding setae - manypredatory setae - fewfilter-feeding setae - nonesuspension-feeding "tentacles"deposit-feeding sucker(s)deitritus/scavenging External & internal - digestiveparasitic "jaws"plant-eating mouthLocomotion gizzardnone - sessile as adults crop"rowing" pharynxsegmental contraction proboscissucker attachment salivary glandsGas Exchange intestines"gills" nephridiamoist integument anushemoglobin Other external & internalReproduction septadioecious - sexes separate sphinctersepitoky epidermal poreshermaphroditic but not protandric cerebral gangliahermaphroditic and protandric segmental gangliaclitellum ventral nerve cordalbumin-filled cocoon formed closed circulatory systemexternal fertilization longitudinal musclesinternal fertilization circular muscles

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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

b. habitats: to

c. shell structure: to to

d. head: to

e. mantle: to

f. gills: to to

g. sensory structures: to to

h. “brain” : to 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”

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SUMMARY & REVIEW Mark an "X" next to each characteristic that is found in all or some of the members of each of these classes.

Apl

acop

hora

Mon

opla

coph

ora

Pol

ypla

coph

ora

Sca

phop

oda

Biv

alvi

a

Gas

tropo

da

Cep

halo

poda

Apl

acop

hora

Mon

opla

coph

ora

Pol

ypla

coph

ora

Sca

phop

oda

Biv

alvi

a

Gas

tropo

da

Cep

halo

poda

Taxonomy External Anatomy minor class; under 200 species distinct head major class; over 200 species no head, head indistinct or poorly developed Habitats tentacles marine only or primarily no tentacles marine and freshwater foot some terrestrial representatives no foot or compressed foot Feeding anus and gills to rear scrape algae off rocks with radula anus and gills to front (via torsion) filter feed Internal Anatomy - Viscera grasp food with tentacles radula herbivorous beak carnivorous mantle scavenge no mantle parasitic reiterated gills, muscles, excretory structures suspension feed gills, muscles, excretory structures not reiterated Locomotion gills replaced by lungs creep on foot Internal Anatomy - Nervous and Sensory burrow sensory organs limited "jet-propelled" sensory organs well developed sessile (do not move as adults) eyes Shell Structure no eyes no shell; may have imbedded spicules "brain" a ring of ganglia shell single cap from union of spicules well-developed brain segmented shell of 8 plates Reproduction shell is cylinder or cone, tusk-like hermaphroditic; may be protandric single valve shell dioecious double valve shell reduced internal shell

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