2 General Characteristics About 9000 speciesSimple nervous systemCalled a nerve net. No brainHas tentacles, sometimes very small that grab prey and pull them to the mouth, thus they are predators.They might be sessile or motile, or each at different times of their life.
3 General Characteristics Cont’d- Either tubular or bell shaped(Polyp or medusa form)Only animal withcnidocytesCnidocytes-specializedstinging cells (on tentacle)All marine (aquatic) exceptFor a few freshwater examples
4 ____________________________ Cnidarians’ bodies are organized around the (hollow stomach area)gastrovascular cavity, where digestion takes placeGV has a single opening that serves as both mouth and anus
5 2 Layers of CellsDiploblastic means that its body developes from 2 layers of cells.Gastrodermis: lines GV cavityEpidermis: lines the outside of the body (the skin)
6 In between the two layers is the mesoglea- a jelly-like substance.
11 FeedingUsing tentacles they touch the prey and inject the “poison” into them with nematocysts. This “stuns” or paralyzed the prey. WHY? So it wont tear its tentacles off in the struggle.Inner gastrodermis secretes digestive juices into gastrovascular cavity which digests food and circulates nutrients