The document discusses the phylum Platyhelminthes, commonly known as flatworms. Flatworms are triploblastic organisms with a dorsoventrally flat body and a linear nervous system including a ganglion. They have three cell layers consisting of ectoderm, mesoderm and endoderm. Their incomplete digestive system has a single opening and they also have an excretory system. There are four classes of flatworms, with the most important being Turbellaria (including planaria and ribbon worms), Cestoda (tapeworms), and Trematoda (flukes).

1. Phylum PlatyhelminthesPhylum Platyhelminthes
“Flat Worms”“Flat Worms”
ByBy
Mr. “Super Bowl Bound”Mr. “Super Bowl Bound”
ChapmanChapman

2. PlatyhelminthesPlatyhelminthes
Platy = flatPlaty = flat
Helminthes = wormHelminthes = worm
Flat WormsFlat Worms

4. CharacteristicsCharacteristics
 1. Triploblastic1. Triploblastic
 Three layers of cellsThree layers of cells

5. PlatyhelminthesPlatyhelminthes
Flatworms 3 cell layers:Flatworms 3 cell layers:
Ectoderm (epidermis)Ectoderm (epidermis)
MesodermMesoderm
EndodermEndoderm

6. CharacteristicsCharacteristics
 2. Linear nervous system with a ganglion (brain)2. Linear nervous system with a ganglion (brain)

7. CharacteristicsCharacteristics
 3. Dorsoventrally flat, bilaterally symmetrical body3. Dorsoventrally flat, bilaterally symmetrical body

8. CharacteristicsCharacteristics
 4.4. CephalizationCephalization – the development of an– the development of an
anterior end (head)anterior end (head)

9. CharacteristicsCharacteristics
 5. Incomplete digestive system (one opening)5. Incomplete digestive system (one opening)
 6. An excretory system for removing cellular6. An excretory system for removing cellular
wasteswastes

10. There are four classes of flatworms, three of which
are important to us…

11. PlatyhelminthesPlatyhelminthes
 Class: Turbellaria – planaria and ribbon worms.
 Class: Cestoda – tapeworms
 Class: Trematoda – flukes

12. The End