Name: 
 

Ch 27 - Worms and Mollusks



Modified True/False (Value 10)
Indicate whether the statement is true or false.  If false, change the identified word or phrase to make the statement true.
 

 1. 

Turbellaria is a class of parasitic flatworms. _________________________

 

 2. 

The type of body cavity shared by all mollusks is a pseudocoelom. _________________________

 

 3. 

Polychaetes are annelids that help aerate and mix layers of soil, improving the soil’s quality. _________________________

 

 4. 

Undigested material leaves a roundworm’s body through the anus. _________________________

 

 5. 

A flatworm’s eyespots can detect chemicals. _________________________

 

 6. 

Mollusks are soft-bodied animals that usually have an internal or external shell. _________________________

 

 7. 

In clams and oysters, two shells are held together by powerful muscles—a trait common to all cephalopods. ____________________

 

 8. 

An unidentified worm specimen that has a one-way digestive tract suspended in a pseudocoelom is likely to be a(an) annelid. _________________________

 

 9. 

Unlike most parasitic worms, polychaetes typically attach to their host externally. _________________________

 

 10. 

Annelids and mollusks, both of which possess a coelom, may be more closely related to each other than either is to flatworms or roundworms. _________________________

 

Completion (Value 5)
Complete each statement.
 

 11. 

Many free-living roundworms are ____________________, which are animals that eat other animals.
 

 

 12. 

Sandworms and bloodworms are members of the class of marine annelids called ____________________.
 

 

 13. 

The primary host of Schistosoma mansoni is a(an) _________________________.
 

 

 14. 

The type of embryonic tissue that lines a true coelom is called ____________________.
 

 

 15. 

The simplest animals to have three embryonic germ layers, bilateral symmetry, and cephalization are the ____________________.
 

 

Short Answer (Answer any 2 of 5) (Value 4)
 

 16. 

What role does diffusion play in the lives of roundworms and flatworms?
 

 17. 

What has happened to the internal shell of squids over evolutionary time?
 

 18. 

What are the four parts of the body plan of most mollusks?
 

 19. 

In what ways do earthworms improve soil quality?
 

 20. 

What is the meaning of the Latin word molluscus? Why is this meaning appropriate for mollusks?
 

Multiple Choice Answer 15 of the following 20 questions (Value 15)
Identify the choice that best completes the statement or answers the question.
 

 21. 

An adult tapeworm uses its scolex to
a.
store sperm.
b.
digest food.
c.
attach itself to the intestinal wall of its host.
d.
store fertilized eggs.
 

 22. 

Which of these animals has a true coelom?
a.
planarian
c.
leech
b.
tapeworm
d.
filarial worm
 

 23. 

The spade-shaped burrowing structure of one group of mollusks and the tentacles of another group are both modifications of the
a.
shell.
c.
foot.
b.
visceral mass.
d.
mantle.
 

 24. 

The larvae of many marine annelids are ecologically important because they
a.
poison coral reefs.
b.
feed on earthworms.
c.
are eaten by fishes and other marine animals.
d.
aerate the mud on the seafloor.
 

 25. 

Some mollusks are detritivores.  Their main source of food comes from
a.
bacteria in the muddy bottom.
c.
living animals.
b.
living plants.
d.
decaying plant and animal remains.
 

 26. 

Roundworms have a digestive system
a.
with one opening.
c.
within a true coelom.
b.
with two openings.
d.
that branches into multiple passages.
 

 27. 

What causes the disease called elephantiasis?
a.
ascarid worms
c.
filarial worms
b.
flukes
d.
hookworms
 

 28. 

In an earthworm, the dorsal blood vessel functions like a heart because it
a.
connects to sinuses.
c.
receives blood from gills.
b.
contracts and helps pump blood.
d.
connects to ring vessels.
 

 29. 

The most active mollusks are the
a.
gastropods.
c.
cephalopods.
b.
bivalves.
d.
nudibranchs.
 

 30. 

In a pseudocoelom, mesoderm partially lines the
a.
body cavity.
c.
germ layer.
b.
blood vessels.
d.
pharynx.
 

 31. 

In earthworms, food is ground into small pieces in the
a.
gizzard.
c.
crop.
b.
pharynx.
d.
esophagus.
 

 32. 

Mollusks have
a.
a true coelom.
b.
a body cavity between the ectoderm and mesoderm.
c.
no body cavity.
d.
a pseudocoelom.
 

 33. 

Why is an open circulatory system adequate for a bivalve, such as a clam, but not for a cephalopod, such as a squid?
a.
Cephalopods have relatively low oxygen demands.
b.
Bivalves are largely sedentary, while squids move quickly.
c.
Bivalves have relatively high oxygen demands.
d.
Bivalves are filter-feeders, and cephalopods are plant eaters.
 

 34. 

Bivalve communities that live near undersea volcanic vents obtain their food mostly from
a.
symbiotic bacteria.
c.
filter-feeding.
b.
detritus.
d.
symbiotic algae.
 

 35. 

Free-living flatworms, most of which live in marine environments or fresh water, are
a.
roundworms.
c.
turbellarians.
b.
tapeworms.
d.
flukes.
 

 36. 

The tubelike structure through which water enters and leaves a mollusk’s body is the
a.
siphon.
c.
sinus.
b.
mantle cavity.
d.
coelom.
 

 37. 

In the tapeworm, both male and female reproductive organs are contained in each mature
a.
proglottid.
c.
egg.
b.
cyst.
d.
scolex.
 

 38. 

What conditions could be expected in an area where large numbers of mud-dwelling, filter-feeding, marine annelids are found?
a.
abundance of roundworms
c.
low bacteria population
b.
abundance of algae
d.
compacted muddy bottom
 

 39. 

Most free-living flatworms are
a.
parasites.
c.
hermaphrodites.
b.
flukes.
d.
members of the class Cestoda.
 

 40. 

All roundworms
a.
are unsegmented.
c.
are parasites.
b.
cause human disease.
d.
reproduce asexually.
 



 
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