| A | B |
|---|
| cnidarians | are characterized by two cell layers, a saclike digestive tract, and tentacles |
| radial symetry | body plan in which appendages are arranged around a central point |
| hydroid | colonial animal composed of different polyps that together as a single organism |
| medusa | umbrella shaped body part composed of two membranes |
| mesoglea | jellylike mass between the two membranes of the medusa |
| cnidoblasts | stinging cells contained in their tenacles |
| nematocyst | coiled thread with a barb, usually toxic |
| polyp | body structure with mouth, tentacles, and digestive cavity; lives attached to a substrate |
| symbionts | member of two different species involved in mutually beneficial relationship |
| symbiosis | close relationship between different species; usually beneficial |
| coral polyp | coral animal, usually colonial; resembles small sea anemone |
| colonial animals | organisms that live attached to one another by a thin membrane and have shared membrane |
| zooxanthelle | dinoflagellate algae that live sympiotically within coral polyps |
| nerve net | simple nervous system, a network of nerve cells and receptor cells |
| planula | ciliated, swimming larva of some invertebrates |
| sea anemones | have tentacles and a nerve net; live as sessile polyps |
