Phylum: Mollusca

Class: Polyplacophora

Class: BivalviaClass: GastropodaClass: Cephalopoda

Class: BivalviaScallop

Gastropod

Class: PolyplacophoraChiton

Cuttlefish

Class: Cephalopod

Class: Gastropoda

Class: Bivalvia

Land slug Class: Gastropoda

Gastropod

Cephalopod

Nautilis

Class: Cephalopoda

Zebra Mussel Class: Bivalvia

Food for thought

What Phylum have all of these animals been in?

GENERAL CHARACTERISTICS

• Lifestyle- Variety, bottom feeders, borers, burrowers,

parasites, predators

• Economics- food, pearls, gardeners, hosts, sewers, predators, cleaning

http://www.americanpearl.com/pearedmov.html

• Bilateral symmetry

• Unsegmented, but has a definite head(cephalization)

• Locomotion- muscular foot

• Nervous system- Nerve cords, sensory nerve endings that sense touch, smell, taste, equilibrium, vision in some, and ganglia

• Respiration- O2/CO2 exchange through body surface and gills or lungs

• Circulatory system •Open system in most•Closed system in cephalopods

• Digestion - complex and specialized in different molluscs

- True coelom - Radula a hard tongue

• Excretion- Specialized system with a pair of kidneys for osmoregulation

• Reproduction- Most are dioecious, some are hermaphroditic or monecious

Characteristics Class: Bivalvia two shells

Examples• Mussels• Clams• Scallops• Oysters• Shipworms

Bivalvia (continued)

• Filter feeders (*no radula*)

• No cephalization

• Reproduction- dioecious with external fertilization

• Development- 3 larval stages trochophore larva spat

BivalviaShells divided into two parts.  Gills are used for feeding and gas exchange.Example:  Clams, oysters

Spawning clam

Ex-current siphon

Incurrent siphon of giant clam

Bivalvia (continued)

• Respiration- gills in mantle

• Nervous system- 3 pair of ganglia with 2 pair of nerve cords

• Sense organs- chemoreceptors statocysts in foot (balance)

Examples• Snails• Limpets• Slugs• Welks• Conchs• Sea slugs

CharacteristicsClass: Gastropoda----Large foot

Class: Gastropoda

• Largest and most diverse class of mollusca 2nd largest class overall 40,000 living species 15,000 fossils

• Most have shells

• most are bilateral/torsion causes asymmetry

Class: Gastropoda

• Mostly herbivours, some scavengers living on the dead and some carnivours

• Digestion- enzymes, extracellular and intracellular

(chemical / mechanical)• Respiration- By gills in the mantle

Terrestrial has lungs

Class: Gastropoda

• Nervous system- 3 pairs of ganglia

• Reproduction- Dioecious Monecious, but self fertilization rarely occurs

• Sense organs- Tentacles on head which may have eyes Statocysts in foot

CharacteristicsClass: Cephalopoda Head foot

Examples• Squid• Octopus• Nautiluses• Cuttlefish

Class: Cephalopoda

• Most complex class• *Most advanced invertebrate brain*• All are predators• All are marine• 2cm-30cm normal / Giant squid 18m• Ink production for protection

• Chromatophores pigment cells in skin controlled by nervous system and hormones allow cephalopods to change colors

Class: Cephalopoda• Locomotion-expelling water from mantle

• Reproduction- dioecious internal fertilization

• Circulatory system- Closed with capillaries to organs• Respiration- Gills

Class: Cephalopoda• Nervous system- Central with large brain Nerves with ganglia and buccal ring• Sense organs

•Eyes•Statocysts•chemoreceptors

Cladogram phylum Mollusca

Mollusca

Polyplacophora

GastropodaCephalopoda Bivalvia