| A | B |
|---|
| Phylum Cnidarian | This phylum includes hydra, jellyfish, sea anemone, coral; this group is characterized by the fact that they are soft-bodied, carnivorous animals that have stinging tentacles arranged in circles around their mouths. They are the simplest animals to have body symmetry and specialized tissues |
| cnidocyte | stinging cell located along the tentacles of cnidarians; used for defense and to capture prey |
| nematocyst | stinging structure within each cnidocyte of a cnidarian that is used to poison or kill prey |
| polyp | usually sessile stage of the life cycle of a cnidarian that has a cylindrical body with armlike tentacles |
| medusa | motile stage of the life cycle of a cnidarian that has a bell-shaped body |
| gastrovascular cavity | digestive chamber with a single opening, in which cnidarians, flatworms, and echinoderms digest food |
| gastroderm | inner lining of the gastrovascular cavity |
| mesoglea | layer that lies between these two tissues |
| nerve net | loosely organized network of nerve cells that together allow cnidarians to detect stimuli |
| statocysts | groups of sensory cells that help determine the direction of gravity |
| ocelli | eyespots made of cells that detect light |
| hydrostatic skeleton | layers of circular and longitudinal muscles, together with the water in the gastrovascular cavity, that enables movement |
| external fertilization | process in which eggs are fertilized outside the female’s body |
| budding | polyps can reproduce asexually by budding; budding begins with a swelling on the side of an existing polyp, which grows into a new polyp |
| Class Scyphozoa | this class contains jellyfish; the class name means "cup animals" since they live their lives primarily as medusas |
| bioluminescence | production of light by an organism to ward off predators; used by jellyfish |
| Class Hydrozoa | this class contains hydra and Portuguese man-of-war |
| Class Anthozoa | this class contains sea anemones and corals |
| coral bleaching | when high temperatures kill the algae that usually live in the tissues of corals, leaving behind only transparent cells atop ghostly white skeletons |
