Mollusca

Question 1

Summarise mollusca

Answer 1

Bilaterally symmetrical
Body more that two cell layers thick
Nervous system
Body wall comprise of a cuticle epidemic and muscles
They have gills for counter current flow

Question 2

Locomotion of mollusca

Answer 2

Sessile
crawling
burrowing
swimming

Question 3

Feeding I’m mollusca

Answer 3

Radula (spiked tounge) found in all taxa except bivalves

Question 4

Describe torsion in mollusca

Answer 4

Occurs in Gastropods
The visceral organ sack rotates 180 degrees during development the nerves are crossed over and the gut is flipped
Body sack seperate from the coiled shell
Detorted is when the organ sack is twisted back This means that the anus is where the head is so desiccation on the head of the Gastropoda is not ideal as the head contains the sensory organs, therefore they have slits in the shell so the faeces come out at the sides.
Theory as to why torsion happened is after torsion the mantle cavity is at the front of the head thus making it easier for the Gastropoda to retract its head