Phylum Cnidaria

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Phylum Cnidaria

• Samantha Evans

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Phylum Cnidaria
Basic characteristics

• All Cnidaria have the following
• Basic radial symmetry
• Tentacles surrounding the mouth
• One opening to the digestive system
• Two layers of living tissue
• Epidermis
• Gastrodermis
• Gelatinous mesoglea between the layers

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Phylum Cnidaria
Classes

• Scyphozoa
• Cubozoa
• Hydrozoa
• Alcyonaria
• Zoantharia

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www.creationguide.com
tolweb.org
www.avru.org
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Phylum Cnidaria
Basic body plan
Polyp
Medusa
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Phylum Cnidaria
Polyp

• Sessile
• Stick to surfaces

Medusa
coris.noaa.gov

• Motile
• Move through passive drifting
• Also move via contractions of the body

biology.unm.edu
Many cnidarians go through stages as both polyp
and medusa during their lifetimes
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Phylum Cnidaria
Feeding

• Extend tentacles
• Wait for prey to become ensnared
• Pull food into gastrovascular cavity
• Digest
• Expel waste via opening to gastrovascular cavity

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Phylum Cnidaria
Tentacles

• Are armed with cnidocytes
• Cnidocytes contain cnidae
• Cnidae are capsule like organelles that can
  explode outwards
• Cnidae tentacles can be adhesive, poisonous or
  merely ensnare prey

www.curator.org
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Phylum Cnidaria
Nervous system

• Cnidarians have no brain
• Instead they have a network of nerves
• This nerve net is connected to sensory structures
  located around the body
• This allows the Cnidaria to respond to stimuli
  from all directions

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Phylum Cnidaria
Biodiversity

• The phylum contains 10,000 species
• Most of these species are marine
• A small amount are freshwater
• The phylum includes
• Jellyfish and Box Jellyfish
• The Portugese-Man-Of-War
• Corals
• And many others

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