Download Section 27–1 Flatworms

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Chapter 27 Worms and Mollusks
Section 27–1 Flatworms
(pages 683–688)
TEKS FOCUS: 10A Functions of organ systems; 12B Parasitism;
TEKS SUPPORT: 8A Classify organisms
This section describes the defining features of flatworms. It also describes the
characteristics of the three groups of flatworms.
What Is a Flatworm?
(page 683)
Platyhelminthes
1. Flatworms make up the phylum
.
2. What are the defining features of flatworms? Flatworms are soft, flattened worms that have
tissues and internal organ systems. They are the simplest animals to have three embryonic germ
layers, bilateral symmetry, and cephalization.
3. A fluid-filled body cavity that is lined with tissue derived from mesoderm is called
a(an)
coelom
.
4. Why are flatworms known as acoelomates? No coelom forms between the tissues of
flatworms.
5. Is the following sentence true or false? Flatworms are the simplest animals to have
three germ layers.
true
Form and Function in Flatworms
(pages 684–686)
6. Circle the letter of each sentence that is true about flatworms.
a. Parasitic species are typically simpler in structure than freeliving species.
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b. Free-living flatworms have organ systems for digestion,
excretion, response, and reproduction.
c. Free-living species probably evolved from parasitic ancestors.
d. All flatworms rely on diffusion for some essential functions.
7. What do free-living flatworms feed on? They can be carnivores that feed on tiny aquatic
animals or scavengers that feed on recently dead animals.
8. A muscular tube near the mouth at the end of the gastrovascular cavity is called
a(an)
pharynx
.
9. What is the function of the pharynx? Flatworms use a pharynx to suck food into the
gastrovascular cavity.
10. What are flame cells, and what is their function? Flame cells are specialized cells that
remove excess water from the body. They may also filter and remove metabolic wastes such
as ammonia and urea.
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11. What are ganglia, and what do they do in flatworms? Ganglia are groups of nerve cells,
and they control the nervous system in flatworms.
12. A group of cells that can detect changes in the amount of light in a flatworm’s
eyespot
environment is called a(an)
.
13. How do cilia help flatworms move, and what do muscle cells allow them to do?
Cilia help flatworms glide through the water over the bottom of a stream or pond.
Muscle cells allow them to twist and turn in reaction to environmental stimuli.
14. What is a hermaphrodite? A hermaphrodite is an individual that has both male and female
reproductive organs.
15. What occurs during fission? An organism splits in two, and each half grows new parts to
become a complete organism.
16. Is the following sentence true or false? Free-living flatworms often have complex life
cycles that involve both sexual and asexual reproduction.
Groups of Flatworms
false
(pages 686–688)
17. Complete the table about the main groups of flatworms.
GROUPS OF FLATWORMS
Class
Description
Turbellarians
Turbellaria
Free-living bottom dwellers
Flukes
Trematoda
Parasitic flatworms that infect hosts’ internal organs or outside parts
Tapeworms
Cestoda
Long, flat, parasitic worms that live in hosts’ intestines
18. Circle the letter of each sentence that is true of turbellarians.
a. Most live in marine or fresh water.
b. Most are the same color, form, and size.
c. Most are bottom dwellers.
d. The most familiar are the planarians.
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Common Name
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19. How does the blood fluke Schistosoma mansoni infect humans? It burrows through
exposed skin.
20. In which host do blood flukes reproduce sexually, and in which do they reproduce
asexually? Blood flukes reproduce sexually in the primary host and asexually in the intermediate
host.
21. On the illustration of the blood fluke’s life cycle, label the primary host and the
intermediate host.
Primary host
Intermediate host
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22. In what areas is schistosomiasis particularly widespread? It is widespread in
tropical areas that lack proper sewage systems, where human wastes are tossed into streams
or used as fertilizer.
23. The head of an adult tapeworm is called a(an)
scolex
.
24. What does a tapeworm use its scolex for? A tapeworm uses its scolex to attach to the
intestinal wall of its host, where it absorbs nutrients.
25. What are proglottids? They are the segments that make up most of a tapeworm’s body.
26. Sperm are produced by male reproductive organs, called
testes
.
27. Is the following sentence true or false? Sperm produced by a tapeworm’s testes can
fertilize the eggs of the same individual.
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true
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Section 27–2 Roundworms
(pages 689–693)
Date ______________
TEKS FOCUS: 3D Careers; 5B Cell differentiation; 10A Systems in organisms; 12B Parasitism;
TEKS SUPPORT: 8A Classify organisms
This section describes the defining features of roundworms. It also identifies
which roundworms are important in human disease.
What Is a Roundworm?
(page 689)
1. Circle the letter of each sentence that is true about roundworms.
a. Parasitic roundworms live in plants and in animals.
b. All roundworms are parasitic.
c. Some roundworms are a meter in length.
d. All roundworms develop from three germ layers.
2. A body cavity that is lined only partially with tissue derived from the mesoderm is
called a(an)
pseudocoelom
.
3. How is a roundworm’s digestive tract like a tube-within-a-tube? The inner tube is the
digestive tract, and the outer tube is the body wall.
4. The posterior opening of the digestive tract is called the
anus
.
5. Circle the letter of each feature that a roundworm has.
a. pseudocoelom
b. mouth
c. anus
Form and Function in Roundworms
d. coelom
(page 690)
6. Which have more complex body systems, free-living or parasitic roundworms?
Free-living roundworms have more complex body systems.
7. Is the following sentence true or false? Many free-living roundworms are predators.
true
body walls
.
9. What can roundworms’ sense organs detect? They detect chemicals given off by prey or hosts.
10. Do roundworms reproduce sexually or asexually? Sexually
Roundworms and Human Disease
(pages 690–692)
11. How do Trichinella roundworms cause pain in their hosts? They travel through the
bloodstream and burrow into organs and tissues.
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8. Roundworms exchange gases and excrete metabolic wastes through their
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12. Complete the table about roundworms and human disease.
DISEASE-CAUSING ROUNDWORMS
Roundworm
Disease or Condition Caused
How Disease Is Spread
Trichinella
Trichinosis
By eating muscle tissue of infected animal
Filarial worms
Elephantiasis
Through biting insects, especially mosquitoes
Ascarid worms
Malnutrition
In the feces of the host
Hookworms
Weakness and poor growth
Burrowing through an unprotected foot
13. What is elephantiasis? It is a condition in which a part of the body swells enormously. The
swelling is caused by large numbers of filarial worms blocking the passage of fluids within the
lymph vessels.
14. Circle the letter of each sentence that is true about the life cycle of Ascaris.
a. Larvae in the lungs are coughed up and swallowed.
b. The eggs develop into larvae in the lungs.
c. Fertilized eggs leave the host’s body in feces.
d. The host ingests Ascaris eggs in contaminated food or water.
15. How are ascarid worms commonly spread? They are spread by eating vegetables or other
foods that are not washed properly.
16. Where do hookworm eggs hatch and develop? They hatch outside the body of a host and
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develop in the soil.
Research on C. elegans
(page 693)
17. Circle the letter of each sentence that is true about C. elegans.
a. It is a free-living roundworm.
b. Its DNA was the first of any multicellular animal’s to be
sequenced completely.
c. It feeds on rotting vegetation.
d. Its DNA has 30 times the number of base pairs that human
DNA has.
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Section 27–3 Annelids
Class __________________
Date ______________
(pages 694–699)
TEKS FOCUS: 3C Impact of research on scientific thought; 10A Systems in organisms;
12B Parasitism; TEKS SUPPORT: 8A Classify organisms
This section describes the defining features of annelids. It also describes the
characteristics of the three classes of annelids.
Introduction
(page 694)
1. What phylum are earthworms a member of?
Annelida
2. What evidence is there that annelids are more closely related to clams and snails than
to flatworms or roundworms? Annelids, clams, and snails all share a similar larval stage.
What Is an Annelid?
(page 694)
3. What is a septum? A septum is an internal wall between two segments of an annelid’s body.
4. Attached to each annelid segment are bristles called
5. Annelids are among the simplest animals to have a true
Form and Function in Annelids
setae
.
coelom
.
(pages 695–696)
6. How is the pharynx used differently in carnivorous species than in annelids that
feed on decaying vegetation? In carnivores, the pharynx usually holds two or more sharp
jaws that are used to attack prey. In worms that eat vegetation, the worm collects food by
extending a pharynx covered with sticky mucus and pressing it against the surrounding sediments.
7. What is a closed circulatory system? It is a system in which blood is contained within a
network of blood vessels.
8. What is a gill? A gill is an organ specialized for the exchange of gases underwater.
Aquatic annelids often breathe through gills, while land-dwelling annelids respire through their
moist skin.
10. How do annelids keep their skins moist? They secrete a thin protective coating called a
cuticle.
11. What are the two major groups of body muscles in annelids called?
a. Longitudinal muscles
b. Circular muscles
12. Marine annelids have paddlelike appendages called
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parapodia
.
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9. How do aquatic annelids respire differently than land-dwelling annelids?
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13. What is a clitellum, and what is its function? A clitellum is a band of thickened, specialized
segments that secrete a mucous ring into which eggs and sperm are released.
14. Write labels on the illustration of the annelid for each of the features pointed to.
Setae
Body segments
Clitellum
Groups of Annelids
(pages 697–698)
15. Complete the table about common types of oligochaetes.
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OLIGOCHAETES
Type of Oligochaete
Description
Habitat
Earthworms
Long, pinkish-brown worms with few setae
Woods, fields, and gardens
Tubifex worms
Red, threadlike worms with few setae
Aquatic environments
16. Circle the letter of each sentence that is true about leeches.
a. They suck blood and body fluids from their hosts.
b. Most live in moist, tropical habitats.
c. They are typically external parasites.
d. All are carnivores that feed on snails.
17. Circle the letter of each sentence that is true about polychaetes.
a. They typically have only a few setae.
b. They have paired, paddlelike appendages tipped with setae.
c. They suck the blood of their host.
d. They are marine annelids.
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18. What annelids do polychaetes include? They include sandworms, bloodworms, and their
relatives.
Ecology of Annelids
(page 699)
19. How do the tunnels of earthworms affect other organisms? Earthworm tunnels provide
passageways for plant roots and water and allow the growth of beneficial, oxygen-requiring soil
bacteria.
20. Circle the letter of each sentence that is true about annelids.
a. Earthworms are important to the diet of birds.
b. Annelids bring minerals from deep soil layers to the surface.
c. Marine annelids spend their lives burrowing through soil.
d. Annelid larvae form part of the animal plankton.
Reading Skill Practice
A flowchart can help you remember the order in which a process or series of events
occurs. On a separate sheet of paper, make a flowchart for the process in
earthworms of feeding and digestion, described on page 695. For more information
about flowcharts, see Organizing Information in Appendix A of your textbook.
Students should describe food pumped into the esophagus by the pharynx and then moving through
the crop, gizzard, and intestine.
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Section 27–4 Mollusks
Class __________________
Date ______________
(pages 701–708)
TEKS FOCUS: 10A Body systems; TEKS SUPPORT: 8A Classification; 10B Interrelationships
of organ systems
This section describes the defining features of mollusks. It also describes the basic
mollusk body plan and the characteristics of the three main classes of mollusks.
What Is a Mollusk?
(page 701)
1. Mollusks are members of the phylum
Mollusca
.
2. Circle the letter of each sentence that is true about mollusks.
a. They share similar developmental stages.
b. They usually have an internal or external shell.
c. They are the ancestors of annelids.
d. They are soft-bodied animals.
3. What is a trochophore? It is a larval stage of a mollusk.
Form and Function in Mollusks
(pages 702–704)
4. What are the four parts of the body plan of most mollusks?
a. Foot
b. Mantle
c. Shell
d. Visceral mass
5. What forms do the muscular mollusk foot take? Flat structures for crawling, spade-shaped
structures for burrowing, and tentacles for capturing prey
6. The thin layer of tissue that covers most of the mollusk’s body is called the
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mantle
.
7. How is the mollusk shell made? It is made by glands in the mantle that secrete calcium
carbonate.
8. Snails and slugs feed using a tongue-shaped structure known as a(an)
radula
.
9. What is a siphon? A siphon is a tubelike structure through which water enters and leaves the body.
10. Why do land snails and slugs typically live only in moist places? They respire using a
mantle cavity that has a large surface area lined with blood vessels, and the lining must be kept
moist so that oxygen can diffuse across its surface.
11. How does an open circulatory system carry blood to all parts of a mollusk’s body?
Blood is pumped through vessels by a simple heart. Blood eventually leaves
the vessels and works its way through different sinuses.
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sinus
12. A large saclike space in the body is called a(an)
Date ______________
.
13. Ammonia is removed from the blood and released out of the body by tube-shaped
nephridia
.
14. Circle the letter of each sentence that is true about mollusk response.
a. Clams have a simple nervous system.
b. Octopi and their relatives have the most highly-developed
nervous system of all invertebrates.
c. Clams have well-developed brains.
d. Vertebrates are more intelligent than octopi.
15. Where does fertilization take place in tentacled mollusks and certain snails?
It takes place inside the body of the female.
Groups of Mollusks
(pages 705–707)
16. Complete the table about groups of mollusks.
GROUPS OF MOLLUSKS
Common Name
Description of Shell
Examples
Gastropoda
Gastropods
Shell-less or
single-shelled
Pond snails, land slugs,
sea butterflies, sea hares,
nudibranches
Bivalvia
Bivalves
Two shells that are
held together by one
or two powerful muscles
Clams, oysters,
mussels, scallops
Cephalopoda
Cephalopods
Only small internal
shells or no shells
Octopi, squids,
cuttlefishes, nautiluses
17. Circle the letter of each sentence that is true about bivalves.
a. Mussels use sticky threads to attach themselves to rocks.
b. Some bivalves feed on material deposited in sand or mud.
c. Clams move by flapping their shells rapidly when threatened.
d. Scallops sting predators with recycled cnidarian nematocysts.
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Class
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18. How do gastropods move? They move by using a muscular foot located on the ventral side.
19. The cephalopod head is attached to a single
20. What is a cephalopod’s foot divided into?
foot
.
Tentacles, or arms
21. What allows squids to locate a wide variety of prey? They have large, complex eyes that
can distinguish objects as small as 0.5 centimeters from a meter away.
22. The only present-day cephalopods with external shells are
Ecology of Mollusks
nautiluses
.
(page 708)
23. What allows mollusks to inhabit the extreme environment around deep-sea volcanic
vents? Within the bivalves around these vents are symbiotic bacteria that extract chemical
energy from compounds in the water. From that energy, the bacteria produce food molecules that
the mollusks can use.
24. Why can careful checks of bivalves warn public health officials of possible health
problems to come? Filter-feeding bivalves concentrate dangerous pollutants
and microorganisms in their tissues. Therefore if certain bivalves contain high levels of pollutants,
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people are warned not to eat them.
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WordWise
The block of letters below contains eight vocabulary terms from Chapter 27.
Use the clues to identify the words you need to find. Then, find the words
across, down, or on the diagonal. Circle each word in the hidden-word puzzle.
Clues
Vocabulary Terms
scolex
The head of an adult tapeworm
crop
Where food is stored in an earthworm
A fluid-filled body cavity that is lined with tissue derived
from mesoderm
coelom
A group of nerve cells
ganglion
seta
A bristle attached to an annelid segment
A filamentous organ specialized for the exchange of gases underwater
gill
pharynx
A muscular tube near the mouth
fission
Asexual reproduction in which an animal splits in two
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