Mollusks

General Characteristics Kingdom: Animalia Phylum: Mollusca “soft body” Class: Cephalopoda “head-footed” (squid) Examples of Mollusca Clams Snails Slugs Octopuses

Groups of Mollusks Classified according to their foot and shell Three major classes of mollusks Gastropods Bivalves Cephalopods

Characteristics 112,000 species Coelomates Soft body with internal or external shell Larval stage called a trochophore Body plan: Foot – takes on many forms Mantle – covers the body Shell – (present in most) Visceral mass – internal organs

7 survival systems Feeding & Digestion Excretion mouth, anus and complex stomach radula-help the mollusks scrape algae and force food backward Some filter feed-through their gills Tentacles- grab and hold prey Excretion carried out by a pair of nephridia (earthworm also had this) Empties into the mantle cavity

Circulatory Respiration Response Open circulatory system- gastropoda & bivalvia Closed circulatory system- cephalopoda Respiration Use gills to exchange O2 and CO2 Response Mental capacity like that of a cat Largest eyes among animals Complex nervous system Nerve ring located around the mouth with a nerve cord connected to ganglia

Reproduction Movement Internal fertilization (cephalopods) External fertilization Movement Varies among classes of mollusks Gastropoda- crawling Bivalvia- sessile Cephalopoda- rapid swimming

Gastropods snails, slugs, limpets and nudibranchs Shell-less or single shelled Move by a muscular foot Some are poisonous, bright colors

Bivalves Things with two shells

Cephalopoda octopi, squids, and cuttlefish soft-bodied , head is attached to foot foot is divided into tentacles with sucking disks small internal shells or no shell at all Squid have a modified shell called a pen most complex of the mollusks

Echinoderms “spiny skin”

General Characteristics Invertebrates No cephalization (no head region) Deuterostomes- recall from earlier what this means? Habitat- marine environments Examples: Sea stars Sand dollars Sea urchins Sea cucumbers

Unique Characteristics Endoskeleton Made up of plates called ossicles Water-vascular system Tube feet Extensions that aid in movement, feeding, respiration and excretion