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15 Cards in this Set

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Charactersitic's of Mollusks

~ Soft-bodied

~ Coelomates

~ Have a three part body plan

~ Most have a shell

~ Bilateral symmetry

~ Ex. Snails, oysters, clams, octopus and squid

Mollusks Body Plan & Organ System

~ The three parts that make up the mollusk are the mantle, visceral mass and the foot

Mollusk Feeding & Digestion

~ All mollusks (Except bivalves) have a two shelled radula which is a tongue like organ covered with thousands of pointing curled teeth.

~ Food is digested in the stomach and intestine of the one way digestive tract.

~ Waste passes out the anus (Tube within a tube)

Animals with true coeloms

The gut and other internal organs are suspended from the body wall and are cushioned by the fluid within the coelom.

Visceral Mass

The visceral mass is the central section of the mollusk body and contains the mollsck's organs.


The heavy fold of tissue outside of the visceral mass which forms the outer layer of the body and secretes the mollusk's shell.


A muscular mass found in every mollusk which is used primarily for locomotion

Mollusk Excretion

~ The coelom of the mollusk collects waste body fluids

~ The cilia then pull the fluid from the coelom into a tubelike sructure called the nepheridia which recovers an useful materials (Ie. salt, sugar)

~ The remaining fluid leave via the anal pore

Mollusk Circulation

~ Most mollusks have a 3 chambered heart and an open circulatory system

~ Optopi and their relatives are exceptions as they have closed circulatory systems where blood remains inside of the vessels

Mollusk Respiration

~ Most mollusk respire with gills found in the mantle cavity

~ Mollusk gills extract 50% or more of the dissolved oxygen from the water that passes over them

~ Most terrestrial snails have no gills and the thin membrane that lines the snail's empty mantle cavity works as a primitive lung

Mantle cavity

Space located between the visceral mass and the mantle

Mollusk Reproduction

~ Distinct female and male invididuals (some snails and slugs are hermaphrodites)

~ Fertilization of eggs occurs externally in most aquatic mollusks and internally in terrestrial mollusks and octopuses and their relatives.

~ The fertilized eggs develop into trochophore larave

Trochosphere Larave


Mollusk Diversity

Gastropods, cepholopods and bivavles share the same basic organ systems and tissue layers but different feeding and body plans

Class Gastropoda

~ snails and slugs that live primarily marine but some in terrestrial and freshwater

~ Most gastropods have a pair of tentacles on their heads that have eyes on their tips

~ Most have a single shell but slugs and nudibranches have no shell

~ The foot of gastropods is adapted for locomotion. In terrestrials, the base secretes mucus from the base of the foot to provide a slimy path for them to glide along

~ Many are herbivores while others are active predators