Simple InvertebratesSection 3 CH27: Sec3 Phylum Platyhelminthes Flatworms

Simple InvertebratesSection 3 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

Simple InvertebratesSection 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

Simple InvertebratesSection 3 Characteristics of Flatworms

Simple InvertebratesSection 3 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, parasitic flukes, ex. Fasciola Species range in size from less than 1mm to many meters in length.

Simple InvertebratesSection 3 Class Turbellaria Planarians and marine flatworms

Simple InvertebratesSection 3 Class Trematoda Flukes Involve several host Schistosomiasis disease from contact with contaminated water

Simple InvertebratesSection 3 Class Cestoda Tapeworms Largest group of endoparasites Tegument on tissue Hooks to attach to host Proglottids to reproduce