Flatworms or Who Got Run Over by the Mail Truck

I. General Traits or Characteristics A. Simplest animal that possesses bilateral symmetry

B. Bilateral symmetry 1. recall that organism has a dorsal and ventral surface 2. also has a left and right side

C. Cephalization 1. concentration of nerve tissue in the head of the animal 2. two ventral nerve cords running posteriorly 3. anterior sensory organs

D. Triploblastic E. No coelom

F. Possesses organ systems 1. digestive system – a. Single opening – b. Tubular muscular pharynx – c. Single arm leading anteriorly – d. Forked branch leading posteriorly – e. Note highly branched nature

Muscular pharynx

Flatworm feeding Downloads.htm Downloads.htm K0Y&NR=1&feature=fvwp K0Y&NR=1&feature=fvwp

2. Reproductive system a. Hermaphroditic b. Both sexes on same organism

3. Excretory system

4. No respiratory nor circulatory system Why not?

II. Classes of platyhelminthes A. Turbellaria 1. already described 2. planaria and relatives

B. Monogenea 1. parasitic forms 2. ectoparasites

C. Trematodes-schistosomiasis

D. Cestoidea-tapeworm 1. scolex 2. proglottids 3. de-evolution 4. reproductive machine 5. pieces of “rice” in feces

This is HUGE!!!

Once you are attached…

That is what you call “knockers”

Aren’t parasites fun?

What does this say??