Molluscs

Question 1

Facts about the molluscs

Answer 1

1. 2nd largest group of animals
2. Very diverse
3. Have a trochophore larva (if they have a larval stage)
4. 7 different groups (more but 2 are extinct)

Question 2

Standard mollusc structure

Answer 2

Visceral mass is surrounded by a mantel (which secretes the shell if they have one)
Mantel overhangs back on animal forming mantel cavity where gills are found
Radula in the mouth is a feeding device (conveyor of chitinous teeth)
Nerve ring around oesophagus branches in V mass and foot
Foot can be used in feeding or movement and can be modified
Open circulatory system combined with coelom (haemocoel)

Question 3

Mollusc gills

Answer 3

Consist of filaments, looks like a cone
Cilia found on gills keeping movement constant
Some cilia used in cleaning gills

Question 4

Foot movement in some molluscs

Answer 4

If used for movement, it creates waves of muscular contractions where they move antagonistically - acting on cells
Cells are built with fluid in the foot, so contractions act on this
Can produce mucous that aids in movement too

Question 5

Circulatory system of molluscs

Answer 5

Still have some vessels, but not completely closed

1. Blood starts at the gills and gets oxyenated
2. Goes through vessels into heart-like structure
3. Is pumped out through vessels and into haemolymph in the haemocoel
4. Circulates through all tissues
5. Goes back into vessels and gets oxygenated by gills again