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Platyhelminthes

Platyhelminthes. Melody Rodsuwan & Douglas Wang. Period 5. General Characteristics. flattened, bilaterally symmetrical have no other body cavity than the digestive cavity (acoelomates) platy = flat & helminthes = worms

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Platyhelminthes

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  1. Platyhelminthes Melody Rodsuwan & Douglas Wang Period 5

  2. General Characteristics • flattened, bilaterally symmetrical • have no other body cavity than the digestive cavity (acoelomates) • platy = flat & helminthes = worms • Platyhelminthes were regarded as a primitive stage in the evolution of bilaterians soft and ciliated epidermis covered with cuticle and external suckers or hooks, or both • space between internal organ filled by loose parenchyma • well developed muscle layers • no skeletal, circulatory, or respiratory system

  3. Classes of Platyhelminthes Turbellaria-Planaria http://www.thaigoodview.com/library/contest2551/science04/119/kingdon_animalia/Class%20Turbellaria.htm

  4. Classes of Platyhelminthes Cestoda-beef & pork tapeworms http://x3on.blogspot.com/2009_04_01_archive.html

  5. Classes of Platyhelminthes Monogenea-Diplozoon paradoxum http://instruction.cvhs.okstate.edu/jcfox/htdocs/Disk1/Images/Img0086.jpg

  6. Classes of Platyhelminthes Trematoda-Human Live Fluke http://gurungeblog.wordpress.com/2008/11/11/mengenal-phylum-platyhelminthes/

  7. Body Plan • Bilateral symmetry • have no other body cavity than the digestive cavity (acoelomates) • three germ layers (mesoderm, ectoderm, endoderm) • soft and ciliated epidermis covered with cuticle and external suckers or hooks, or both

  8. Feeding • General • flat worms have one digestive opening that branches to all parts of the body • Turbellarians • use muscular pharynx and prey on smaller animals or feed on dead animals • Cestoda • block the intestines and rob nutrients from the human host • Monogena and Trematoda • use suckers for attaching to internal organs rely on the host for digestion

  9. Respiration • General • Respiration occurs through diffusion • Mainly carnivorous and prey on small invertebrates • Also feed on remain of dead animal • All exchange is on a cellular level, by diffusion, which is why flatworms are flat. Nitrogenous waste mostly as ammonia, lost through diffusion. Endoparasitic forms often rely on anaerobic metabolism

  10. Circulation • General • Circulation occurs through diffusion • Lack circulation system • Some species have gastrovascular system • Otherwise, all internal transport occurs by simple diffusion through and between cells of the small body.

  11. Excretion • General • Excretion occurs through flame cells • Mouth: anterior end or mid-body on ventral surface • Lack an anus •  Excess water (and possibly wastes) enters the flame cell system and is propelled through the tubules toward the outside by the beating of the cilia (the "flame

  12. Response • General • Higher temperature and starvation • Negatively affect size • Decrease the number of days that elapsed before egg laying began • More larvae at 21°C than at 30°C • Tangoreceptor: respond to touch • Minimal b/c no orientation to light or gravity • Light sensitive eyespots • Can adapt and modify

  13. Response II • Ocelli • eyespots that detect light • Gangalia • main sources of sensory input • Aurical • tasting chemicals • Have a cephalized nervous system • ventral nerve cord • head ganglion attached to nerve cords connected body • by transverse branches across the

  14. Movement • Turbellians • use cilia to move over a secreted slime tract • head slightly raised • Cestoda • absorb nutrients from host • no movement • Monogenea and Trematoda • parasitic worms rely on the host's circulation • suckers for attachment

  15. Reproduction • General • Asexual reproduction • Budding • Binary fission • Regeneration • Sexual reproduction • Hermaphroditic • Occurs through the exchange of sperm • Internal fertilization • Cross fertilization

  16. Reproduction II • Turbellaria • exchange of sperm • Cestoda • proglottids: several ovaries and 1,000 distinct testes • Monogenea • make both sperm and eggs • Trematoda • gut and well-developed reproductive system

  17. Works Cited • "Platyhelminthes." W. Fielding Rubel School of Business. Web. 21 http://cas.bellarmine.edu/tietjen/images/platyhelminthes.htm • "Platyhelminthes." Oracle ThinkQuest Library. Web. 21 Apr. 2010. <http://library.thinkquest.org/26153/marine/platyhel.htm>. • "Behavior and Reproduction." Monogeneas. Web. 21 Apr. 2010. <http://animals.jrank.org/pages/1521/Monogeneans-Monogenea-BEHAVIOR-REPRODUCTION.html>.

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