| A | B |
|---|
| nematocyst | the stinger of a jellyfish |
| mantle | part of a mollusc that makes the shell |
| sac plan | digestive system has only one opening |
| ectoderm | outer tissue layer of an animal's body |
| endoderm | inner tissue layer of an animal's body |
| coelom | the body cavity of an animal |
| polyp and medusa | life stages of a cnidarian |
| mesoderm | third tissue layer necessary for the formation of the coelom |
| tube-within-a-tube | digestive system has two openings |
| protostome | mouth end of digestive system develops first |
| deuterostome | tail end of digestive system develops first |
| exoskeleton | outer skeleton of arthropods |
| bilateral | having two identifiable halves, left and right |
| radial | having a circular organization |
| complete metamorphosis | larva does not resemble adult |
| incomplete metamorphosis | larva resembles adult |
| Malpighian tubule | blood-filtering structure in insects |
| nephridia | blood-filtering structure in molluscs |
| kidney | blood-filtering structure in vertebrates |
