Flatworms and Roundworms
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Printed: September 4, 2015
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C HAPTER
Chapter 1. Flatworms and Roundworms
1
Flatworms and
Roundworms
Lesson 12.2: True or False
Name___________________ Class______________ Date________
Write true if the statement is true or false if the statement is false.
1.
2.
3.
4.
5.
6.
7.
________ All flatworms are several meters long.
________ Flatworms have a concentration of nerve tissue in the head end.
________ Flatworms may have several different larval stages.
________ A parasitic flatworm usually needs more than one type of host to complete its life cycle.
________ Phylum Nematoda has less than 800 known species.
________ The body of a roundworm has a tough covering of cuticle.
________ All parasitic roundworms have vertebrate hosts.
Lesson 12.2: Critical Reading
Name___________________ Class______________ Date________
Read this passage based on the text and answer the questions that follow.
Flatworms have a flat body because they lack a fluid-filled body cavity. They also have an incomplete digestive
system with a single opening. However, flatworms represent several evolutionary advances in invertebrates. They
have the following adaptations:
• Flatworms have three embryonic cell layers. They have a mesoderm layer in addition to ectoderm and
endoderm layers. The mesoderm layer allows flatworms to develop muscle tissues so they can move easily
over solid surfaces.
• Flatworms have a concentration of nerve tissue in the head end. This was a major step in the evolution of a
brain. It was also needed for bilateral symmetry to evolve.
• Flatworms have bilateral symmetry. This gives them a better sense of direction than radial symmetry would.
Flatworms reproduce sexually. In most species, the same individuals produce both eggs and sperm. After fertilization
occurs, the fertilized eggs pass out of the adult’s body and hatch into larvae. There may be several different larval
stages. The final larval stage develops into the adult form. Then the life cycle repeats.
Some flatworms are free-living organisms. They may live in water or moist soil where they eat invertebrates and
decaying organic matter. Other flatworms, such as tapeworms, are parasites that live inside vertebrate hosts. They
obtain nutrition directly from their hosts. Usually, more than one type of host is needed to complete the parasite’s
life cycle.
Questions
1. Identify three evolutionary advances that occurred in flatworms.
2. Explain how flatworms reproduce.
3. Outline two ways that flatworms obtain food.
1
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Lesson 12.2: Multiple Choice
Name___________________ Class______________ Date________
Circle the letter of the correct choice.
1. How many species belong to Phylum Platyhelminthes?
a.
b.
c.
d.
more than 25,000
fewer than 15,000
about 10,000
about 8,000
2. Flatworms are flat because they
a.
b.
c.
d.
have an incomplete digestive system
lack a pseudocoelom or coelom
have just two embryonic cell layers
lack a mesoderm cell layer
3. Flatworms reproduce by producing
a.
b.
c.
d.
buds
spores
gametes
none of the above
4. Both flatworms and roundworms may be found living in
a.
b.
c.
d.
water
moist soil
vertebrate hosts
any of the above
5. Which statement about roundworm reproduction is true?
a.
b.
c.
d.
Sperm and eggs are produced by the same adult
Fertilization occurs in the water outside the adult’s body
Eggs hatch into larvae, which develop into adults
Reproduction may occur sexually or asexually
6. Free-living roundworms may feed on
a.
b.
c.
d.
bacteria
fungi
protists
all of the above
7. How many eggs can a single roundworm lay in a day?
a.
b.
c.
d.
about 10
up to 100
around 1,000
as many as 100,000
Lesson 12.2: Matching
Name___________________ Class______________ Date________
2
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Chapter 1. Flatworms and Roundworms
Match each definition with the correct term.
Definitions
1.
2.
3.
4.
5.
6.
7.
________ name of the phylum to which roundworms belong
________ common name for the type of worm that has a pseudocoelom
________ parasitic roundworm with special structures for attaching to the host’s intestines
________ common name for the type of worm that lacks a pseudocoelom
________ example of a flatworm that is a human parasite
________ name of the phylum to which flatworms belong
________ largest and most common parasitic worm in humans
Terms
a.
b.
c.
d.
e.
f.
g.
hookworm
flatworm
Nematoda
roundworm
ascaris
Platyhelminthes
tapeworm
Lesson 12.2: Fill in the Blank
Name___________________ Class______________ Date________
Fill in the blank with the appropriate term.
1.
2.
3.
4.
5.
6.
7.
Invertebrates that belong to Phylum Platyhelminthes are commonly called _______________.
Flatworms have a(n) _______________ digestive system with a single opening.
Both flatworms and roundworms have _______________ symmetry.
Invertebrates that belong to Phylum Nematoda are commonly called _______________.
The worm named ascaris belongs to Phylum _______________.
Roundworms that break down organic matter play an important role in the _______________ cycle.
Hookworms enter their vertebrate host through the host’s _______________.
Lesson 12.2: Critical Writing
Name___________________ Class______________ Date________
Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences.
Compare and contrast the physical traits of flatworms and roundworms.
3