Invertebrates 2 flatworms, molluscs & annelids

Dorso ventrally flattened ovoid shape convex dorsal

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Dorso-ventrally flattened, ovoid shape, convex dorsal surface with 8 plates (b) Muscular foot provides strong attachment & is used in locomotion (c) Reduced head (d) Scrapes algae with radula 3. Gastropoda (Class Gastropoda) (a) Marine, fresh water & terrestrial (b) Shell may be absent (c) Bilateral, but torsion or twisting of shell & visceral mass
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Invertebrates -2: Platyhelminthes, Mollusca & Annelida Page 4 of 9 (d) Distinct head with tentacles - Tentacles contain sense organs & move independently - Top tentacles have ________________________________________________ - Bottom tentacles have _____________________________________________ (e) Nutrition & respiration (f) Movement is by contraction of foot muscle 4. Bivalves (Class Bivalvia) - Clams, oysters, mussels & scallops
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Invertebrates -2: Platyhelminthes, Mollusca & Annelida Page 5 of 9 (a) Body form (b) Head & radula lost - Eyes & sensory tentacles on outer edge of mantle (c) Gills used for respiration & feeding (i) Incurrent & excurrent siphons (ii) Water movement (iii) Mucous on gills traps food (d) Bivalves are usually sedentary (e) Defense & pearls only in some bivales - If a foreign particle (sand, parasite) is lodged between the shell & mantle, mantle secretes nacre around the objects. 5. Cephaopoda (Class Cephalopoda) (a) The shell is present (nautiluses), absent (octopuses), or reduced & internal (squid & cuttlefishes).
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