Chapter 26 Sponges and Cnidarians
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27 terms
Terms | Definitions |
|---|---|
 invertebrate | animals with no backbone |
| vertebrate | animals with a backbone |
| feedback inhibition | a mechanism of homeostasis where the body reacts to something in the external world (ex: getting hot and sweating) |
| blastula | hollow ball of cells |
| protostome | an animal whose mouth is formed from the blastopore |
| deuterostome | animal whose anus is formed from the blastospore |
| anus | opening through which waste leaves the digestive tract |
| endoderm | inermost germ layer |
| mesoderm | middle germ layer |
| ectoderm | outermost germ layer |
| radial symmetry | symmetry going around in a circle across the body |
| bilateral symmetry | symmetry that can split into two identical parts |
| caphalization | concentration of sense organs and nerve organs at the front end of the body |
| choanocytes | specilized cells that use flagella to move a steady current of water through the sponge |
| spicule | spike-like structure made of chalklike calcium carbonate or glasslike silica |
| archaeocytes | specialized cells that move around within the walls of the spong |
| internal fertilization | fertilization in the inside of the body |
| larva | immature stage of an organism |
| gemmules | groups of archaeocytes surrounded by a tough layer of spicules |
| nematocyst | poison-filled sting structure that contains a tightly coiled dart |
| cnidocytes | stinging cells located along tentacles in which cnidarians get their name |
| polyp | a cylindrical body with armlike tentacles; mouth points upwards, routed to ground |
| medusa | motile, bell-shaped body with a mouth on the bottom |
| gastrovascular cavity | digestive chamber with one opeing |
| nerve net | a loosely organized network of nerve cells that together allow cnidarians to detect stimuli |
| hydrostatic skeleton | consists of a layer of circular muscles and a layer of longitudinal muscles that (along with the nerve net) enable the body to move |
| external fertilization | fertilization on the outside of ones body |
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