Interest Grabber

1
Interest Grabber
Section 27-1

• Tapeworm Tales
• Have you ever heard someone say, That person
  eats so much and stays so thin, youd think he
  has a tapeworm!

1. In the United States, the chance of having a
tapeworm in your body is very rare. From clues in
the above statement, how might a tapeworm affect
an individual? Where would you most likely find a
tapeworm in the body? 2. On what do you think
these tapeworms feed?
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Section Outline
Section 27-1

• 271 Flatworms
• A. What Is a Flatworm?
• B. Form and Function in Flatworms
• 1. Feeding
• 2. Respiration, Circulation, and Excretion
• 3. Response
• 4. Movement
• 5. Reproduction
• C. Groups of Flatworms
• 1. Turbellarians
• 2. Flukes
• 3. Tapeworms

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Life Cycle of Schistosoma Mansoni
Section 27-1
Flukes mature and reproduce sexually in the blood
vessels of human intestines. Embryos are released
and passed out with feces.
Adult fluke
Human intestine
Embryo
Ciliated larva
Tailed larva
After asexualreproduction, newlarvae are
releasedfrom the snail into the water. They then
infect humans, the primary host, by burrowing
through the skin.
If they get into the water, embryos develop into
swimming larvae that infect an intermediate host
(snail).
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Figure 273 The Anatomy of a Flatworm
Section 27-1
Eyespot
Freshwater flatworms have simple ganglia and
nerve cords that run the length of the body. The
excretory system consists of a network of tubules
connected to flame cells that remove excess water
and cell wastes.
Ganglia
Head
Nervecords
Gastrovascularcavity
Flatworms use a pharynx to suck food into the
gastrovascular cavity. Digested food diffuses
from the cavity into other cells of the body.
Eyespots in somespecies detect light.
Excretorysystem
Ovary
Testes
Mouth
Pharynx
Most flatworms are hermaphrodites, having male
reproductive organs (testes) and female
reproductive organs (ovaries) in the same
organism.
Flame cell
Excretorytubule
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Interest Grabber
Section 27-2

• Too Small to Measure Up?
• When digging in the soil, you can see many
  animals, such as insects, earthworms, and
  spiders. But there are many animals that you
  cannot see. Roundworms, for example, are so small
  that a shovelful of fertile soil may contain
  millions of these free-living worms.

1. To see how long roundworms are, draw a line
on a sheet of paper. The width of the line that
you drew is the length of the shortest
roundworms. Measure and record the width of the
line. 2. The width of the tip of your pinky
finger is the length of the longest roundworms.
Measure and record the width of your pinky. 3.
Based on this information, what is the range of
length in roundworms?
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Section Outline
Section 27-2

• 272 Roundworms
• A. What Is a Roundworm?
• B. Form and Function in Roundworms
• 1. Feeding
• 2. Respiration, Circulation, and Excretion
• 3. Response
• 4. Movement
• 5. Reproduction
• C. Roundworms and Human Disease
• 1. Trichinosis-Causing Worms
• 2. Filarial Worms
• 3. Ascarid Worms
• 4. Hookworms
• D. Research on C. elegans

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Diseases Caused by Roundworms
Section 27-2
ORGANISM Trichinella Filiarial
worms Ascaris Hookworms
DISEASE Trichinosis Elephantiasis Ascaris
infection/infestation Hookworm
infection/infestation
ROUTE OF INFECTION Eating undercooked meat
containing larval cysts Bite of insect carrying
filarial worms Eating unwashedfood
contaminatedwith Ascaris Bare skin in contact
with contaminated soil
DESCRIPTION Larvae burrow into tissues of host,
causing pain Worms block passage of fluids
within lymph vessels, causing tissues to
swell Worms in intestine block normal passage of
food and absorption of nutrients Worms attach to
intestinal wall and suck blood, causing weakness
and poor growth
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Interest Grabber
Section 27-3

• Just Slinking or Wriggling in the Rain
• Have you ever noticed that after a spring rain,
  earthworms come out of the soil and appear on
  driveways, in puddles, and on sidewalks? Why does
  this happen?

1. An earthworm breathes through its skin. If
its skin dries out, it cannot breathe. Why would
an earthworm be more likely to surface during
the rain than at other times? 2. What types of
weather conditions might be fatal for an
earthworm?
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Section Outline
Section 27-3

• 273 Annelids
• A. What Is an Annelid?
• B. Form and Function in Annelids
• 1. Feeding and Digestion
• 2. Circulation
• 3. Respiration
• 4. Excretion
• 5. Response
• 6. Movement
• 7. Reproduction
• C. Groups of Annelids
• 1. Oligochaetes
• 2. Leeches
• 3. Polychaetes
• D. Ecology of Annelids

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Compare/Contrast Table
Section 27-3
Comparing Flatworms, Roundworms, and Annelids
CHARACTERISTIC Shape Segmentation Body
cavity Digestion and excretion Respiration
FLATWORMS Flattened No Acoelomate Gastrovascular
cavity with one opening only flame cells remove
metabolic wastes Through skin no respiratory
organs
ROUNDWORMS Cylindrical with tapering
ends No Pseudocoelomate Tube-within-a-tube
digestive tract opening at each end metabolic
wastes excreted through body wall Through skin
no respiratory organs
ANNELIDS Cylindrical with tapering
ends Yes Coelomate Tube-within-a-tube digestive
tract opening at each end nephridia remove
metabolic wastes Through skin aquatic annelids
breathe through gills
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Compare/Contrast Table continued
Section 27-3
Comparing Flatworms, Roundworms, and Annelids
CHARACTERISTIC Circulation Response
Movement Reproduction
FLATWORMS No heart, blood vessels,or
blood Simple brain nerve cords run length of
body eyespot and other specialized cells that
detect stimuli Gliding, twisting,and
turning Sexual (hermaphrodites) asexual (fission)
ROUNDWORMS No heart, blood vessels,or
blood Several ganglia in head region nerve
cords run length of body several types of sense
organs Thrashing Sexual (primary males and
females)
ANNELIDS Blood circulated through blood vessels
in closed circulatory system Well-developed
nervous system with brain and several nerve
cords many sense organs Forward peristaltic
movement Sexual (some are hermaphrodites some
have separate sexes)
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Figure 2716 The Anatomy of an Earthworm
Section 27-3
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Interest Grabber
Section 27-4

• The Same Yet Different
• Have you ever eaten clams? Gone clamming? Seen
  clams in the supermarket? How about octopi? Have
  you ever seen an octopus in a movie or in an
  aquarium?

1. Clams and octopi are members of the phylum
Mollusca. Although they have similarities, they
have some differences, too. What is one
characteristic they share? 2. What is one way
that these animals differ from one another?
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Section Outline
Section 27-4

• 274 Mollusks
• A. What Is a Mollusk?
• B. Form and Function in Mollusks
• 1. Body Plan
• 2. Feeding
• 3. Respiration
• 4. Circulation
• 5. Excretion
• 6. Response
• 7. Movement
• 8. Reproduction
• C. Groups of Mollusks
• 1. Gastropods
• 2. Bivalves
• 3. Cephalopods
• D. Ecology of Mollusks

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Compare/Contrast Table
Section 27-4
Comparing the Three Major Groups of Mollusks
MOLLUSK GROUP Gastropods Bivalves Cephalop
ods
SHELL Shell-less orsingle-shelled Two shells
held together by oneor two muscles Internal
shell orno shell
FOOT Muscular foot located on ventral side and
used for movement Burrowing species have muscular
foot. Surface-dwelling species have either no
foot or a reduced foot. Head is attached to a
single foot. The foot is divided into tentacles
or arms.
EXAMPLES Snail, slug, sea hare, nudibranch
Clam, oyster, mussel, scallop Octopus,
squid, cuttlefish, nautilus
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Figure 2721 The Mollusk Body Plan
Section 27-4
Squid
Snail
Shell Mantle cavity Foot Gills Digestive tract
Clam
Earlymollusk
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Figure 2723 The Anatomy of a Clam
Section 27-4
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Video
Video
Earthworm Anatomy

• Click the image to play the video segment.

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Internet
Go Online

• Career links on meat inspectors
• Links from the authors on zebra mussels
• Share snail lab data
• Interactive test
• For links on flukes, go to www.SciLinks.org and
  enter the Web Code as follows cbn-8271.

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Section 1 Answers
Interest Grabber Answers
1. In the United States, the chance of having a
tapeworm in your body is very rare. From clues in
the above statement, how might a tapeworm affect
an individual? Where would you most likely find a
tapeworm in the body? The tapeworm might cause
the person to lose weight or might result in an
intestinal blockage. The tapeworm lives in the
intestines of its host. 2. On what do you think
these tapeworms feed? Food digested by its host
21
Section 2 Answers
Interest Grabber Answers
1. To see how long roundworms are, draw a line
on a sheet of paper. The width of the line that
you drew is the length of the shortest
roundworms. Measure and record the width of the
line. About 0.2 millimeters 2. The width of the
tip of your pinky finger is the length of the
longest roundworms. Measure and record the width
of your pinky. About 6 millimeters 3. Based on
this information, what is the range of length in
roundworms? From 0.2 to 6 millimeters
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Section 3 Answers
Interest Grabber Answers
1. An earthworm breathes through its skin. If
its skin dries out, it cannot breathe. Why would
an earthworm be more likely to surface during
the rain than at other times? The rain keeps
the skin of the earthworm moist. At other times,
the earthworm is likely to dry out and
suffocate. 2. What types of weather conditions
might be fatal for an earthworm? Hot and dry
weather is fatal for an earthworm because its
skin dries out quickly.
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Section 4 Answers
Interest Grabber Answers
1. Clams and octopi are members of the phylum
Mollusca. Although they have similarities, they
have some differences, too. What is one
characteristic they share? Both the clam and
the octopus have soft bodies and live in
water. 2. What is one way that these animals
differ from one another? The clam has a shell,
whereas the octopus does not. The octopus has
tentacles, whereas the clam does not.
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End of Custom Shows

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