Molluscs Flashcards
What are the 7 classes of Mollusc
Gastropoda Bivalvia Cephalopoda Polyplacothora Scaphopoda Alplacophora Monoplacophora
Name the main features of gastropoda
Snails, slugs etc Largest class 'muscular foot' Greatest diversity in water Juveniles undergo 'torsion' - whole body inside shell twists 180 degrees, so the respiratory mantle cavity lies over the head. This allows withdrawal into the shell
Name the main features of bivalvia
Clams, mussels etc
Highly specialised aquatic molluscs
Hinged shells that open to access food and oxygen
Name the main features of cephalopoda
Octopus, squid, cuttlefish etc Agile hunters Most intelligent invertebrates Rapid backwards acceleration Sophisticated nervous system Colour-changing
Name the main features of polyplacothora
Flattened, rock-hugging chitons Most primitive of all molluscs Algae grazers No eyes or tentacles Shells made of 8 reinforced flexible plates Radula reinforced with silica or iron
Name the main features of scaphopoda
Tusk shells (open at both ends)
Live in marine sediments
Common but rarely seen
Probe for food with captacula
Name the main features of alplacothora
No shell Calcerous spines Worm-like Live in marine sediments Headless Hermaphrodites
Name the main features of monoplacophora
Simple conical shell no eyes or tentacles radula 6 pairs of kidneys weak foot
How did mollusc shells evolve?
Early molluscs had a proteinous cuticle that was progressively reinforced with calcium
They are often helically coiled and provide protection from predators
Name the three bivalvia gill functions
Protobranch - most primitive, consists of two large ciliated palps
Lamellibranch - majority of species, ciliated ctendias as filters to catch food, which is passed on by smaller ciliated palps into the mouth
Septibranch - Ctendias are muscular diaphragms which suck in small animals captured by muscular palps
