Bivalves

Question 1

Structure of bivalves

Answer 1

Laterally compressed 
Has a shell made of 2 parts which is hinged
Strong abductor muscles for keeping the shell closed, can open for feeding but can keep very firmly shut
Has very reduced head and NS
Lost radula 
Some use foot for food collection
Byssal threads keep attached to rocks 
Sensitive to light - can close shell
Some move by flapping shell
Most dioecious

Question 2

Types of Bivalve

Answer 2

1. Protobranchs - deposit feeders

2. Lamellibranchs - filter feeders

Question 3

Protobranchs

Answer 3

-use foot for food collection
-deposit feeding
cilia to gather food and passes to mouth
-small gill for respiration
-water drawn into mantle cavity through cilia action on gill

Question 4

Lamellibranchs

Answer 4

• most bivalves
• have large gills - generate current over gills by drawing water into mantle cavity
• cilia used for generating currents for gaseous exchange
• some cilia used for sorting food particles and passing it to mouth
• large foot, mainly used for anchorage