Platyhelminthes

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Platyhelminthes
Phylum

• The Flatworms

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Flatworm
Classification
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Flatworms
Kingdom
Animalia
Phylum
Platyhelminthes
Class
Planarians -
Turbellaria
Flukes -
Trematoda
Tapeworms -
Cestoda
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ectoderm
endoderm
mesoderm
blastula
gastrula
gastrula
(2 germ layers)
(1 germ layer)
(3 germ layers)
Adult flatworms develop from the gastrula with an
ectoderm, endoderm, and mesoderm.
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Symmetry bilateral
anterior end
They have no bones they are invertebrates.
posterior end
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Flatworm Habitat
Whether a fluke, planarian, or tapeworm,
flatworms must live in a moist environment.
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Free-living flatworms (planarians) feed on dead
or very small live organisms.
Parasitic flatworms (flukes and tapeworms) live
inside other organisms.
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Free-living forms have a well-developed digestive
system.
pharynx
This planarian is eating an insect larva.
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Parasitic Flatworms
Parasitic forms lack a digestive system
nutrients diffuse from the host into the worm.
fluke
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All flatworms use diffusion to get O2 and get rid
of CO2 they lack respiratory and circulatory
structures.
O2
CO2
CO2
O2
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Class Turbellaria free-living planarians
nerve cord
pharynx
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Flatworm Nervous System
ganglia
eyespots
nerve cords
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eyespots
eyespots
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Class Trematoda parasitic flukes
Digenea in kidney
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An eye with Digenea
retina
Digenea
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Adult Liver Fluke
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Schistosoma
suckers
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Class Cestoda parasitic tapeworms
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scolex (head)- with hooks
hooks
suckers
suckers
scolex- no hooks
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proglottids
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scolex
proglottids
eggs
Small Tapeworm
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Proglottids showing reproductive structures
testes
ovaries
testes
ovaries