Generals Characteristics• Bilateral symmetry;• Specialized respiratory organs (gills and lungs);• Open circulatory system (except incephalopods);• Foot-muscle.• Mouthparts-equipped by radule.• Many have the trocofora-larva (common ancestor with the annelids).• Ciliated epithelial surface and provided withmucous glands and sensory nerve endings.• Digestive system complex with anus that usually opens into the mantle cavity.• Nervous system consists of pairs of cerebral ganglia connected by nerve cord.• Embryogenesis typically protostomale.
Summary Diagram SYMMETRY DIGESTIVE SYSTEM METAMERISMMOLLUSK BILATERAL TWO OPENINGS NO Nuclear Mitochondrions Chloroplasts Cell wall Multicellularity membraneCells of Present Presents Absents Absent Presentmollusks
Bivalvia Anatomy: 1: posterior adductor, 2: anterior adductor, 3: outer gill demibranch, 4: inner gill demibranch, 5: excurrent siphon, 6: incurrent siphon, 7: foot, 8: teeth, 9: hinge, 10: mantle, 11: umbo.The shell of a bivalve is composedby calcium carbonate and consists of twohalves called valves…
CephalopodThis exclusively marine animals have a bilateralbody symmetry, a prominent head and a set of armsor tentacles modified from the primitive molluscanfoot.A peculiarity of some cephalopoda is that theirpenis elongation may result in a penis that is as longas the mantle, head and arms combined.
GastropodThere are many kinds of gastropods with sizes frommicroscopic to quite large. A peculiarity of gastropodsis that most land gastropods are hermaphrodite that isan organism having normally both the male and femaleorgans of generation.
RostroconchiaThey have a single shell in their larval stage, andthe adult typically has a single, pseudo-bivalved shell enclosing the mantle andmuscular foot.