https://wiki-pathfindersonline.designerthan.at/api.php?action=feedcontributions&feedformat=atom&user=137.148.236.145 2026-05-10T07:29:03Z User contributions MediaWiki 1.35.5 https://wiki-pathfindersonline.designerthan.at/index.php?title=AY_Honors/Shells_-_Advanced/Answer_Key&diff=17181 2004-10-05T16:06:23Z

<p>137.148.236.145: </p> <hr /> <div>'''Nacre''' is an organic mixture of [[calcium carbonate]] (&lt;nowiki&gt;CaCO&lt;/nowiki&gt;&lt;sub&gt;3&lt;/sub&gt;) in the form of platy crystals of [[aragonite]] and [[conchiolin]] (a [[scleroprotein]]). <br /> <br /> Nacre is secreted by the [[ectoderm|ectodermic]] [[cell (biology)|cells]] of the [[mantle tissue]] of certain species of [[mollusk]]. In these mollusks nacre is continually deposited onto the inner surface of the animal's shell (the [[iridescent]] ''nacreous layer'', also known as ''[[mother of pearl]]''), both as a means to smooth the shell itself and as a defense against [[parasite|parasitic organisms]] and damaging detritus.<br /> <br /> When a mollusk is invaded by a parasite or is irritated by a foreign object which the animal cannot eject, a process known as ''[[encystation]]'' entombs the offending entity in successive, concentric layers of nacre. This process eventually forms what we call [[pearl]]s and continues for as long as the mollusk lives.</div>

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