BIO2231 - Mollusca 2 Flashcards
<p><span>Describe</span></p>
<p><strong><span>Class Bivalvia</span></strong></p>
<p>7 points.</p>
<ul><li>Shell has two valves, normally open </li><li>Animal laterally flattened </li><li>Thin mantle tissue lines valves, provides incurrent/ excurrent siphons </li><li>Ctenidia very large W shaped with internal chamber connected to excurrent siphon </li><li>Foot reduced to muscular blade often used for digging </li><li>Most are specialised filter feeders </li><li>Usually sessile but many can move around</li></ul>
<p><span>BIO2231 5aa</span></p>
<p><span>Notable points</span></p>
<p><strong><span>Class Bivalvia</span></strong></p>
<p>7 points.</p>
<ul> <li>No head!</li> <li>No Radula</li> <li>Sensory structures on mantle edge</li> <li>Some are carnivorous</li> <li>Some can swim!</li> <li>Important as major habitat for smaller invertebrates</li> <li>Zooxanthellae (again)</li></ul>
<p><span>BIO2231 5ab</span></p>
<p><span>Describe</span></p>
<p><strong><span>Phylum Mollusca - Class Scaphopoda</span></strong></p>
<p>5 points.</p>
<p><span>Tusk shells</span></p>
<ul><li>Usually small </li><li>Shell tubular (open at both ends) </li><li>No gills, mantle lines the inside of the tube and absorbs O₂ </li><li>Burrowers, foot adapted for digging </li><li>Detritus/ substrate feeders</li></ul>
<p><span>BIO2231 5ac</span></p>
<p><strong><span>Phylum Mollusca - Class Cephalopoda</span></strong></p>
<p>8 points.</p>
<ul><li>Foot modified to funnel + ring of tentacles around head </li><li>Tentacles with suckers </li><li>Large visceral mass </li><li>Head with excellent eyes, large brain </li><li>Large mantle cavity with pair of ctenidia </li><li>Shell variously modified or lost adapted for buoyancy! </li><li>Closed circulatory system </li><li>Active (fast) predators</li></ul>
<p><span>BIO2231 5ad</span></p>
<p><span>Definition</span></p>
<p><strong><span>Ectocochleate?</span></strong></p>
<p>2 points.</p>
<p><span>Externally shelled cephalopods</span></p>
<ul><li>Nautiloids </li><li>Ammonoids (extinct)</li></ul>
<p><span>BIO2231 5ae</span></p>
<p><span>Definition</span></p>
<p><strong><span>Endocochleate</span></strong></p>
<p><span>Cephalopod clades without an external shell<br></br>Coleoidea</span></p>
<div><strong>Cuttlefish</strong> = small, curved shell ( cuttle ), entirely enclosed by mantle </div>
<div><strong>Squid</strong> = only retains thin proteinaceous strip (pen) </div>
<div><strong>Octopus</strong> = shell absent</div>
<div><strong>Vampire squid </strong>= deep sea variant </div>
<p><span>BIO2231 5af</span></p>
<p><span>Class Cephalopoda</span></p>
<p><strong><span>Locomotion</span></strong></p>
<p>5 points.</p>
<ul> <li>Via contraction of mantle and forcing water through a siphon (or funnel)</li> <ul> <li>Slow jetting respiration and ordinary locomotion</li> <li>Fast jetting escape mechanism</li> </ul> <li>Fin swimming</li> <li>Walking (with arms)</li></ul>
<p><span>BIO2231 5ag</span></p>
<p><span>Class Cephalopoda</span></p>
<p><strong><span>Nutrition</span></strong></p>
<p>4 points.</p>
<ul><li>Primarily predatory, cannibalism is known in some species </li><li>Feed using arms with suckers </li><li>Chitinous beak equipped with large muscles </li><li>Radula</li></ul>
<p><span>BIO2231 5ah</span></p>
<p><strong><span>What is a radula?</span></strong></p>
An anatomical structure used by mollusks for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus.<p style="text-align:right;"><span>BIO2231 5ai</span></p>
<p><span>Class Cephalopoda</span></p>
<p><strong><span>Sensory organs</span></strong></p>
<p>3 points.</p>
<ul><li>Most elaboarate of all molluscs </li><li>Highly sophisticated eyes </li><li>Elaborate communication often via visual signals</li></ul>
<p><span>BIO2231 5aj</span></p>
<p><strong><span>What are Chromatophores?</span></strong></p>
<p><span>Pigment cells (in epithelium)</span></p>
<p><span>BIO2231 5ak</span></p>
<p><span>Class Cephalopoda</span></p>
<p><strong><span>Camouflage and visual signalling</span></strong></p>
<p>3 points.</p>
<ul> <li>Muscles expand or contract chromatophores</li> <ul> <li>Concentrate (contract) pigment granules</li> <li>dilute (relax/expand) pigment granules</li> </ul></ul>
<p><span>BIO2231 5al</span></p>
<p><span>Phylum Mollusca - Life histories</span></p>
<p><strong><span>Basic plan</span></strong></p>
<p>5 points.</p>
<ul> <li>separate sexes (dioecious) mostly</li> <li>external fertilisation</li> <li>two successive larval stages </li> <ul> <li>trochophore larva</li> <li>veliger larva with ciliated velum (gastropods and bivalves)</li> </ul></ul>
<p><span>BIO2231 5am</span></p>
<p><strong><span>What is Polyplachophora?</span></strong></p>
<p><span>Ancestral life cycle strategy</span></p>
<div>Adult</div>
<div>Gametes</div>
<div>External fertlisation</div>
<div>Trochophore</div>
<div>Metamorphosis and settlement</div>
<div>Adult</div>
<p><span>BIO2231 5an</span></p>
<p><span>Phylum Mollusca - Life histories</span></p>
<p><strong><span>Gastropoda - option 1</span></strong></p>
<div>+ many bivalves and scaphopods</div>
<ul><li>Adults</li><li>GAMETES </li><li>External fertlisation </li><li>Trochophore </li><li>Veliger</li><li>Metamorphosis and settlement </li><li>Adult</li></ul>
<p><span>BIO2231 5ao</span></p>
