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Online Dictionary of Invertebrate Zoology: Complete Work - Best Text

Online Dictionary of Invertebrate Zoology: Complete Work - Best Text

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<strong>Online</strong> <strong>Dictionary</strong> <strong>of</strong> <strong>Invertebrate</strong> <strong>Zoology</strong> 17actinoid, actiniform a. [Gr. aktis, ray; eidos, shape] Raylike;star-shaped; stellate.actinology n. [Gr. aktis, ray; logos, discourse] 1. The study <strong>of</strong>radially symmetrical animals. 2. The study <strong>of</strong> the activity <strong>of</strong>radiation.actinomere n. [Gr. aktis, ray; meros, part] A segment <strong>of</strong> a radiallysegmented organism.actinopharynx n. [Gr. aktis, ray; pharynx, gullet] (CNID: Anthozoa)Gullet <strong>of</strong> the sea anemone.actinostome n. [Gr. aktis, ray; stoma, mouth] The mouth <strong>of</strong> aradially symmetrical animal.actinotrocha, actinotroch n. [Gr. aktis, ray; trochos, wheel](PHORON) A free-swimming, elongate, ciliated larva <strong>of</strong> thephylum Phoronida, bearing tentacles attached to a girdleimmediately posterior to the preoral lobe.actinula n. [Gr. dim. aktis, ray] (CNID: Hydrozoa) A larvalstage that looks like either a polyp or medusa, dependingupon whether the mouth is turned upward or downward.action current The flow <strong>of</strong> electric current between a region <strong>of</strong>excitation and neighboring unexcited regions.action potential A temporary change in potential that occursacross the surface membrane <strong>of</strong> a muscle or nerve cell followingstimulation.activator n. [L. agere, to act] Any substance that renders anothersubstance active.active a. [L. agere, to act] Pertaining to movement; given toaction; alert.active center The site on an enzyme molecule that interactswith the substrate molecules; where activation and reactiontake place.active transport The transportation or movement <strong>of</strong> substancesthrough differentially permeable cell membranesagainst a concentration or electrical gradient with the expenditure<strong>of</strong> energy.actomyosin n. [Gr. aktis, ray; mys, muscle] Actin and myosin

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