Phylum Mollusca

Phylum MolluscaPhylum Mollusca

- From mollus meaning “soft”- From mollus meaning “soft”

CharacteristicsCharacteristics Eucoelomate - True body cavity

Hollow body cavity, Lined with peritonium (endodermis)

Bilateral symmetry Most have Mantle

Secretes shell - grows with organism Site of Respiration in terrestrial mollusks

Tripoblastic - 3 tissue layers Many Organ systems - well-defined

circulatory, respiratory, excretory, and digestive systems

Eucoelomate - True body cavity Hollow body cavity, Lined with peritonium

(endodermis) Bilateral symmetry Most have Mantle

Secretes shell - grows with organism Site of Respiration in terrestrial mollusks

Tripoblastic - 3 tissue layers Many Organ systems - well-defined

circulatory, respiratory, excretory, and digestive systems

Characteristics (Contd’)Digestion

Characteristics (Contd’)Digestion

Complete digestive tract Separate mouth and anus Radula

Rasping “file” with hundreds of tooth like structures

Feeding Patterns - filter feeders, herbivores, carnivores

Complete digestive tract Separate mouth and anus Radula

Rasping “file” with hundreds of tooth like structures

Feeding Patterns - filter feeders, herbivores, carnivores

Characteristics (Contd’)Circulation

Characteristics (Contd’)Circulation

Some - Open Circulatory System Ex. Gastropoda and bivalvia

Some - Closed circulatory system Ex. Cephalopoda

All have hearts

Some - Open Circulatory System Ex. Gastropoda and bivalvia

Some - Closed circulatory system Ex. Cephalopoda

All have hearts

Characteristics (Contd’) Cephalization

Characteristics (Contd’) Cephalization

Brain with nervous system Gastropoda and Cephalopoda Exception Bivalvia no head=no brain

Sensory cells All have - Touch, smell, taste, balance Some have - True eyes

Cephalopoda and some Gastropoda

Brain with nervous system Gastropoda and Cephalopoda Exception Bivalvia no head=no brain

Sensory cells All have - Touch, smell, taste, balance Some have - True eyes

Cephalopoda and some Gastropoda

ClassificationClassification

Phylum- Mollusca 5 classes:1.Gastropoda2.Bivalvia3.Cephalopoda4.Polyplacophora5.Scaphopoda

Phylum- Mollusca 5 classes:1.Gastropoda2.Bivalvia3.Cephalopoda4.Polyplacophora5.Scaphopoda

1. Class- Gastropoda -“stomach foot”

1. Class- Gastropoda -“stomach foot”

Has one shell or noneEx. Snails, slugs, sea slugs

Snail Conch

Slug Whelk Abalone

2. Class Bivalvia - “Two Shells”

2. Class Bivalvia - “Two Shells”

Ex. Clams, mussels, oysters, scallops

Ex. Clams, mussels, oysters, scallops

Clam Mussel

Scallop Oyster

3. Class Cephalapoda -“head foot”

3. Class Cephalapoda -“head foot”

No shell or one Ex. Squid, octopus, nautilus,

cuttlefish

No shell or one Ex. Squid, octopus, nautilus,

cuttlefish

OctopusSquid

Nautilus

4. Class Polyplacophora -“many plates”

4. Class Polyplacophora -“many plates”

Mantle made of 8 dorsal plates Ex. Chitons

Mantle made of 8 dorsal plates Ex. Chitons

5. Class Scaphopoda5. Class Scaphopoda

Ex. Tooth shell ( aka. Tusk shell) Ex. Tooth shell ( aka. Tusk shell)