Transcript Phylum Cnidaria

Phylum Cnidaria
• Cnidarians (phylum Cnidaria) are multicellular animals with tissues that perform
specific functions
• Cnidarians include the sea anemones, jellyfish,
coral, and their relatives
• Cnidarians have radial symmetry;
in fact radial symmetry evolved
in the Cnidarians!
Cnidarians are rad!
• Animals with radial symmetry look the same
from all sides and have no head, front or back
• Instead have an oral surface (where mouth is)
and aboral surface
Phylum Cnidaria
• Cnidarians have a centrally-located mouth
surrounded by tentacles, slender, finger-like
projections used to capture and handle food
• All possess stinging cells, or nematocysts
• Nematocysts employ neurotoxins which
paralyze prey; 7-17 different types
• The mouth opens up to a gut, with only one
opening
Nematocysts
http://www.youtube.com/watch?v=BpKKGBivQo&feature=related
Phylum Cnidaria
• Cnidarians occur in two basic forms: a polyp, a
sac-like attached form with its mouth and
tentacles pointed upward, and a bell-like
medusa, which resembles an upside-down
polyp adapted to swimming
• Some Cnidarians have both polyp and medusa
stages; others spend their entire lives as either
a polyp or a medusa