Platyhelminthes Presentation by Brendan, John, and Kunio Period 6 3/12/10 http://www-tc.pbs.org/kcet/shapeoflife/imganim/platyhelminthes5.jpg Slide by Brendan
Intro Phyla: Platyhelminthes (Flatworms) marine, freshwater, and damp habitats called Flatworms because their bodies are thin between the dorsal (top side) and ventral (bottom side) surfaces 4 classes Monogenea Trematoda Cestoda Turbellaria Slide by Brendan
Sample Platyhelminthes Diplozoon paradoxum (Monogenea) Taenia saginata (Cestoda) http://www.infektionsbiologie.ch/parasitologie/seiten/lernmo dule/lm5/bilder_05/lm5217diplo.jpg http://www.biogang.net/upload_img/biodiversity/biodiversity-12881-2.jpg Schistosoma mansoni (Trematoda) http://ucf.tekkom.net/bsc2011/images/cards/2/platyhelm_trematoda _Schistosoma.jpg Prosthoceraeus giesbrechti (Turbellaria) Slide by Brendan http://www.bing.com/i mages/search?q=prost hoceraeus&go=&form= QBIR&qs=n#focal=c25f 34d88cedf455841ef16 b8b381a0e&furl=http% 3A%2F%2Fwww.horta. uac.pt%2fspecies%2fpl athelminthes%2fprost hoceraeus_giesbrechti %2FProsthoceraeus_gi esbrechti.jpg
Classes Turbellaria: Mostly marine, body surface ciliated (flatworms) Monogenea: Marine parasites, ciliated larva infects host (monogeneans) Trematoda: Parasites, life cycles include intermediate hosts (trematodes) Cestoda: Parasites of vertebrates, no head or digestive system (tapeworms) Brendan Davis
Body Cavity Acoelomates No body cavity other than gut No anus so the same pharyngeal opening takes in food and expels waste Gut http://cas.bellarmine.edu/tietjen/images/bodyplans.gif Slide by Brendan
Body Symmetry They are bilaterally symmetrical. They can be folded in half over a line running from head to tail Triploblastic Composed of three layers: Ectoderm (outer) Mesoderm (middle) Endoderm (center) http://pt-lobos.com/ctenoimg/comb_jelly_c.jpg Slide by Brendan
Nervous System Cephalization can be seen within Platyhelminthes through the ganglia: two dense clusters of nerve cells that function as two brains A pair of ventral nerve cords emerge from the ganglia that run the length of the body Kunio Iwata! http://www.angelfire.com/oh5/derenbagsby/images/141999_platyhelminthes.jpg
Circulatory System No specialized circulatory organs http://www.starfish.ch/fotos/worms-wuermer/plathelminthes-plattwurm/pseudoceros-dimidiatus.jpg Kunio Iwata!
Excretory System Protonephridial tubules Flame cells: blind ended enlargements of tubules within which beat flagella. This lets out excess water as well as waste. The pharynx also serves as an organ in which excretion may occur. M = Mesoderm F = Flagella P N T = Protonephridial Tubule http://www.path.cam.ac.uk/~schisto/general_parasitology/parasitology_platyhelminthes_bodyplan.html Kunio Iwata!
Locomotion/Musculature Locomotion can take place in one of two ways: Movement by cilia (in which some move along slime trails by beating epidermal cilia) Muscle contraction http://www.youtube.com/watch?v=zch37ki_r_e http://struggle.net/history/images/flatworm.gif Kunio Iwata!
Skeletal Structure Platyhelminthes have no skeletal system. http://www.biology.iastate.edu/courses/211l/platyhelm/planaria%20internal%20anatomy%20wm John Qiu
Sensory Structures/Features Flatworms have eyespots on their head region. They have photoreceptors and cells that can distinguish colors. http://cas.bellarmine.edu/tietjen/laboratories/platyh5.gif John Qiu
Reproduction Asexual reproduction occurs from fragmentation or binary fission. Flatworms are also hermaphrodites, so sexual reproduction can occur as well. http://image.tutorvista.com/content/reproduction/ribbon-flat-wormfragmentation.jpeg John Qiu
Gas Exchange Gas exchange occurs on the cellular level, by diffusion. Endoparasites go through anaerobic metabolism, or fermentation. John Qiu
Unique Characteristics Lack of body cavity. 3 layers of the body (middle mesoderm.) Dorsoventrally flattened. Has a mouth but no anus. http://www.glogster.com/media/2/3/71/6/3710611.jpg John Qiu
Quiz 1. What type of symmetry do Platyhelminthes have? 2. Why are they often called Flatworms 3. What are ganglia and what function do they serve? 4. What are two ways in which movement can occur? 5. How can flatworms go through asexual reproduction? A. External forces B. Binary fission C. Supertwisting D. Impossible 6. How does gas exchange occur in flatworms? A. Diffusion B. Using its anus C. Expelling from the mouth D. Opens its body cavity Slide by Brendan
Answers 1. Bilateral Symmetry 2. Thin between dorsal and ventral sides 3. Dense cluster of nerve cells that function as the brains 4. Movement by cilia and muscle contraction 5. B, Binary Fission 6. A, Diffusion http://www.starfish.ch/fotos/worms-wuermer/plathelminthes-plattwurm/thysanozoon-nigropapillosus5.jpg Slide by Brendan