1. CH34: Phylum Platyhelminthes
Flatworms

2. Characteristics of Platyhelminthes
Thin, flat body (acoelomates)
Bilateral symmetry
3 tissue layers
Endoderm
Ectoderm
Mesoderm
organs and muscles, not present in Cnidarians or Porifera
Cephalization

3. Free-living flatworms are carnivores
Do not have respiratory or circulatory system
Diffusion of gasses
Branched cavity with extensions that run into all major tissues
Gastrovascular cavity
Flatworms reproduce sexually or asexually.
fragmentation

4. Characteristics of Flatworms

5. Groups of Flatworms Three major groups of modern flatworms include;
Class Turbellaria, most free-living and some marine,ex Dugesia
Class Cestoda, parasitic tapeworms, ex. Taenia
Class Trematoda, endoparasitic flukes, ex. Fasciola
Class Monogenea, mostly ectoparasites on aquatic animals
Species range in size from less than 1mm to many meters in length.

6. Class Turbellaria
Planarians and marine flatworms

7. Class Trematoda Flukes Involve several host
Schistosomiasis blood disease from contact with contaminated water

8. Class Monogenea
Fluke
Ectoparasite

9. Class Cestoda Tapeworms Largest group of endoparasites
Tegument on tissue
Hooks to attach to host (Scolex)
Proglottids to reproduce