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Megan Viohl

on 7 March 2013

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Transcript of Platyhelminthes

Flatworms Platyhelminthes Bilateral Symmetry Cestoda (Tapeworm) And Because Turbellarians are so Pretty: Evolution and "Relatives" -Scientists believe the first turbellarians evolved around 550 MYA

-No fossils due to soft body structure Distinguishing Characteristics
of Platyhelminthes Triploblastic Digestion System Platyhelminthes pharynxes and branched-out guts (gastrovascular cavity). Once in the he nutrients are absorbed and the waste products are regurgitated out through the mouth. Some species can also take in nutrients through their skin. Reproduction Most are hermophroditic (they can reproduce sexually or asexually, depending on the conditions and availability of a mate). Movement Turbellaraians move with cilia on ventral surfaces and muscle cell contractions that cause a flapping motion. The other classes mostly rely on their hosts' circulatory systems and their own hooks, spikes, and suckers for movement. Turbellaria (Planarian Flatworm) Instead, oxygen diffuses through the skin. No Body Cavities Three cell layers: ectoderm, mesoderm, and endoderm The Four Classes Turbellaria Trematoda (Flukes) Cestoda (Tapeworms) No Skeletal System No Respiratory System Instead, oxygen diffuses through the skin.
(That's why Platyhelminthes
must be flat or small!) Instead, the mesoderm layer of cells, reinforced with collagen fibers that attach to muscles, acts as a hydrostatic skeleton. Platyhelminthes do not possess an internal body cavity. Nervous System Acoelomate
("no body cavity present") X X -Free-living
-Freshwater, Saltwater, and Terrestrial
- Live in animal hosts or freshwater Schistosoma
(genus) life-cycle -Parasitic
-Most species require at least two hosts for growth
-Segmented into proglottids
-Uses Hooks and suckers to attach to hosts -Parasitic
_Live outside hosts
-Hooks and anchors are attached to the end of Monogeneas
-Indirect life-cycle (two
or more hosts)
Monogenea Nerves extend throughout the entire body and concentrate in head region. In place of a brain, Platyhelminthes possess two nerve-rich masses called ganglia. Platyhelminthes have eyespots (ocelli) that can sense light. Asexual reproduction occurs when a single organism splits up into smaller "pieces" through transverse division, then regrows any missing parts. Most species contain male and female reproduction parts, so they can also sexually reproduce by self-fertilization or cross-fertilization. Bibliography
"Flatworms." Flatworm. N.p., n.d. Web. 01 Mar. 2013. <http://www.mcwdn.org>.

"Flatworms, Tapeworms, Flukes." N.p., Web. 01 Mar. 2013. <http://www.discoverlife.org/>.

"Introduction to the Platyhelminthes." Introduction to the Platyhelminthes. University of California, Berkeley, May 2000. Web. 01 Mar. 2013. <http://www.ucmp.berkeley.edu>.

"Platyhelminthes." The Encyclopedia of Earth. N.p., n.d. Web. 01 Mar. 2013. <http://www.eoearth.org>.

"Platyhelminthes." Encyclopedia of Life. N.p., n.d. Web. 27 Feb. 2013. <http://eol.org>.

"Platyhelminthes." Kennesaw.edu. Kennesaw State University, n.d. Web. 01 Mar. 2013. <http://science.kennesaw.edu>.

Platyhelminthes Pictures. Digital image. Picsearch. N.p., n.d. Web. 02 Mar. 2013. <http://www.picsearch.com>.

Sandhyarani, Ningthoujam. "Reproduction." Buzzle.com. Buzzle.com, 31 May 2011. Web. 01 Mar. 2013.
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