 Have tentacles with nematocysts near mouth.  Nematocysts are stinging cells  Cnidaria is Greek for “stinging cell”  Examples: jellyfish, sea anemone, coral, hydra  Most are marine, but some are freshwater.  Nematocysts are used in defense and for feeding

 Radial Symmetry  Central hollow body opening with one body opening.  Body is two tissue layers thick  Ectoderm- outside layer  Endoderm- inside layer  No skeleton. Water supports the body.  Coral and sea anemone are sessile or stationary; adult jellyfish are moved by current. Some jellyfish can swim.

 Two basic shapes  Polyp  vase-shaped, mouth on top  Medusa  cup-shaped, mouth on underneath

 Nematocysts stun prey  Tentacles put prey in mouth.  Digestion takes place inside body.  Wastes exit through mouth.

 Gas Exchange by diffusion  Nerve net concentrated near mouth  No circulatory system

 Asexual  Budding  Regeneration  Sexual  External fertilization takes place when eggs and sperm are released into the water.

 Provide homes for other organisms  Coral grouping together makes coral reefs  Jellyfish product poisons that are studied to better understand our own nervous systems.