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“ Cnidaria ” PowerPoint Presentation
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“ Cnidaria ”

“ Cnidaria ”

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“ Cnidaria ”

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  1. “Cnidaria” A Presentation by Jack Lorge and Palmer Mathews

  2. Cnidarians and Common Names • Class 1- Anthozoa • Common Name = True Coral, Sea Anemones, Sea Pens

  3. Cnidarians and Common Names • Class 2- Cubozoa • Common Name = Box Jellyfish

  4. Cnidarians and Common Names • Class 3- Hydrozoa • Common Name = Freshwater Hydra, Fire Coral

  5. Cnidarians and Common Names • Class 4- Scyphozoa • Common Name = True Jellyfish

  6. “Anemone”

  7. Video • http://www.youtube.com/watch?v=HciagFg3ZOg

  8. Body Symmetry • 2 Body Forms in Cnidaria 1. Polyp (has radial symmetry) 2. Medusa (has radial symmetry)

  9. In Photos: Body Symmetry Polyp Medusa

  10. Body Plan • Cnidarians have a radially symmetrical body and are diploblastic. • 2 Layers: Ectoderm and Endoderm • Coelenterates

  11. Cnidarian Movement --Medusae swim by jet propulsion: muscles squeeze water out of the cavity. Not very strong, so must swim with currents. --Hydras and sea anemones can “creep” and “crawl” over rocks, but exhibit minimal movement Video Link: http://en.wikipedia.org/wiki/File:Chrysaora_quinquecirrha-Sea_nettle_(jellyfish).ogg

  12. Nutrition • 3 Main Ways of Nutrition • Predation (most common form) • Filtering food particles from water, absorbing dissolved chemicals • Obtaining nutrients from symbiotic algae within their cells

  13. Gas Exchange Process • No respiratory organs • Both cell layers absorb oxygen and expel carbon dioxide into the water

  14. Excretion • Undigested remains are excreted through the mouth/anus

  15. Defense Mechanisms • Tentacles contain cnidocytes • Contain capsule-like organelles called cnidae which can outwardly explode • Specialized cnidae contain nematocysts • Contain a stinging thread that can penetrate the body wall of prey

  16. Response to Stimuli • Cnidarians have no brain • Noncentralized nerve net is associated with sensory structures throughout the body • Therefore, cnidarians can detect and respond to stimuli from all directions

  17. Reproduction • Some cnidarians exist only as polyps, only as medusae, or both