|MadSci Network: Zoology|
Thanks to my colleague, Steve Myers, for finding this Encarta article on teeth. http://encarta.msn.com/text_761561931__1/Teeth.html There you will find that Beavers are monophydont (although the more accepted spelling seems to be monophyodont), having a single set of teeth that grow for their entire lives. Humans (and apparently most mammals) are diphyodont, with 2 sets of teeth in a lifetime; one deciduous (falling out) and one permanent. Other animals may have polyphyodont dentition with regular replacement throughout their lives. The Web is a bit short on examples but polyphyodont animals are found among fish and reptiles, with sharks and alligators being specific examples of polyphyodont kinds. Hope this helps.
Try the links in the MadSci Library for more information on Zoology.