Kingdom Animalia

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Kingdom Animalia

• Phylum Cnidaria (Coelenterata)

http//videos.howstuffworks.com/hsw/11758-the-worl
d-of-animals-phylum-cnidaria-video.htm
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Two Body Forms

• Cnidarians include Jellyfish, Sea Anemones,
  Hydras, and Corals
• All have radial symmetry (little rings)
• Two body forms
• Medusa- Free-floating, jelly-like and often
  umbrella shaped
• Polyp- Tubelike and usually attached to a rock or
  other surface

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Two Body Forms

• Tentacles surround mouth, located at free end of
  body
• Three layers of cells
• Outer layer from ectoderm
• Inner layer from endoderm
• Middle layer of mesoglea (jelly-like)
• Cells arranged into tissues
• Coelenteron- digestive cavity where enzymes
  digest food

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Two Body Forms
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Body Forms

• Cnidocytes
• Stinging cells located on the tentacles
• Distinguishing characteristic of Cnidarians
• Small, barbed harpoon (nematocyst) within each
  Cnidocyte
• Used for defense or to spear prey
• Toxins can be deadly or only stun

• Extracellular digestion
• Digestion begins outside the cell in the
  gastrovascular cavity
• Enzymes break food into smaller fragments
• Cells lining cavity engulf fragments and finish
  digestion intracellularly

http//video.google.com/videoplay?docid-750522024
6577159769eiQPWqSLrmO4OcrwLvmayYAQqcnidarians
vtlfhlenLrmO4OcrwLvmayYAQqcnidariansvtlfhl
en
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Class Hydrozoa

• Freshwater hydrozoa
• Genus Hydra exist only as Polyps less than .4
  long
• Attach to objects with sticky secretion from the
  basal disk
• Can glide on objects or tumble
• Have a nerve net- branching system of nerves with
  no brain

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Class Hydrozoa

• Marine Hydrozoa
• Often live in colonies
• Can be medusas or polyps
• Ex Portuguese man-of-war
• Physalia- floats on water and dangles tentacles
  with powerful neurotoxins (nerve poisons)

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Reproduction in Hydrozoa

• Most hydrozoans are colonial and reproduce
  asexually by budding
• Some species are sexual
• Most single sexes, but some hermaphrodites
• Genus Obelia
• Colonize a single polyp with buds
• Reproductive polyps produce medusas
• Medusas reproduce sexually and produce ciliated
  larvae called planulae, which develop into new
  polyps

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Obelia Reproduction
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Class Scyphozoa

• Jellyfish relatives
• Cubozoans- Small box-shaped medusas with
  tentacles on corner of box
• Inconspicuous polyp stage
• Ex Box jellysish or Sea wasp can be deadly
• Phylum Ctenophora- Comb jellies have only a
  medusa stage and no nematocysts
• Class Tenaculata- with tentacles
• Class Nuda- without tentacles
• Irukandji Jellyfish (Carukua barnesi)
• 2.5 cm in diameter
• Kills in days

• True jellyfish and active predators
• Range from thimble size to queen-size mattresses
• Mostly medusas which reproduce sexually
• Polyp stages early in life

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Jellyfish Relatives

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Class Anthozoa

• Largest class existing only as polyps
• Includes anemones, coral, sea pansies, sea fans,
  and sea whips
• Nearly all contain symbiotic algae,
  dinoflagellates, in exchange for food
• Many of the brilliant colors come from the algae

• Some reproduce asexually by budding
• Others sexual with sperm and egg being released
  into the ocean where fertilization occurs
• Zygotes develop into planulae that settle and
  develop into polyps

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Class Anthozoa
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Class Anthozoa

• Sea anemones- Small and colorful in coastal areas
• Highly muscular- can retract when touched
• Reproduce asexually by splitting themselves into
  two
• Corals
• Colonies called reefs
• Secrete calcium carbonate skeleton that cements
  to skeletons of neighbors
• Top layer is living polyps
• Bottom layers are old skeletons

http//video.google.com/videoplay?docid2146135098
468558056eiQPWqSLrmO4OcrwLvmayYAQqcnidariansv
tlfhlen
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Great Barrier Reef
http//www.aims.gov.au/docs/online-data/reef-from-
space.html
http//ngm.nationalgeographic.com/ngm/0101/feature
2/media.html