2 What is a Mollusk? Soft body with internal or external shell Ex: snails, slugs, clams, squids, and octopiTrochophore larva
3 Body plan: Foot – takes on many forms Mantle – covers the body Shell – (present in most), madeby glands in the mantleVisceral mass – internal organs
4 Feeding: Herbivores, Carnivores Filter feeders (clams, Oysters, scallops)ParasitesMany feed using a flexible tongue shaped structure called a radula. (snails, slugs)
5 Respiration:Aquatic mollusks – snails, clams – breathe using gills in the mantel cavityLand snails breathe with a “lung” – a mantle cavity with a large surface area and many blood vessels.
6 Circulation – can be open or closed Open works better for slow moving mollusks (less efficient)Closed works better for fast moving mollusks (more efficient)Excretion – tube shaped nephridiaResponse – nervous systems vary from simple to complexReproduction – many reproduce sexually with external fertilization,Tentacled mollusks this is usually internalA few are hermaphroditesAll have a free swimming trochophore larva !
7 Groups of Mollusks 1. Gastropods 2. Bivalves 3. Cephalopods Three major classes of mollusks1. Gastropods2. Bivalves3. Cephalopods
8 Gastropod snails, slugs, and nudibranchs Shell-less or single shelled Move by a muscular footSome are poisonous, bright colors