3 Worm Phyla (long, thin bodied animals) All eumatazoans (have true tissues) All have bilateral symmetry Develop a coelom → body cavity 1. Phylum Platyhelminthes (flatworms) 2. Phylum Nematoda (roundworms) 3. Phylum Annelida (segmented worms)

Platyhelminthes The flatworms

Platyhelminthes Platyhelminthes (flatworms) 20,000 species Live in marine, freshwater, & damp terrestrial habitats Bilaterally symmetrical Eumatazoans Triploblastic Acoelomates Thin, flattened soft bodies dorsoventrally Defined head Simple organs One opening to the body Many species are parasitic 4 Classes: 1. Turbellaria 2. Monogenea 3. Trematoda 4. Cestoda

Characteristics

The first hunters Scientists believe that flatworms are the first to have evolved the ability to move forward- and therefore can seek prey.

Turbellaria The Planarians Free-living Mostly marine with some freshwater and a few terrestrial Predators and scavengers Movement Ciliated body surface (glide along mucus) Undulating muscles

European Planarians

Reproduction Asexual- Planaria can regenerate missing body parts- up to a point. Sexual reproduction- make both eggs and sperm- exchange sperm

Monogenea The flukes Marine and freshwater Parasitic Typically of fish Simple life history Larva start infection on host Mouth at head region

Trematoda The flukes Parasitic Mainly vertebrates 2 suckers that attach to host Mouth at head region Most life cycles include intermediate hosts

Cestoda Parasitic Scolex attaches to host Life cycle with one or more intermediate hosts Proglottids produce eggs and break off after fertilization No head or digestive system