Buoyancy

Question 1

Density =

Answer 1

Weight per unit volume

Question 2

How much water does a 1000cc fish displace?

Answer 2

1000cc of fluid.

The amount of water displaced is the exact volume of the fish/object etc that enters the water.

Question 3

A 1000g fish will displace how much water in a freshwater and salt water environment.

Answer 3

Freshwater = 1000g

Saltwater = 1025g

Question 4

How does a fish obtain neutral buoyancy?

Answer 4

By changing the density of the internal body fluids by getting rid of the heavier elements.

Question 5

How does a dinoflagellate obtain neutral buoyancy?

(solution buoyancy)

Answer 5

it reduces concentrations of

• Magnesium
• Calcium
• Sulphate

In favour of lighter ions like

• Sodium
• Pottasium

Question 6

Sharks do not have swim bladders. Pelagic sharks such as the basking shark use what as a method as buoyancy?

(solution buoyancy)

Answer 6

• Lipid fat storage
• Liver accounts for 25% of body weight
• Half of shark liver oil is squalene (low density)
• Cartilaginous skeleton
• Bottom dwelling sharks have a smaller liver

Question 7

What is a siphonophores and what does it belong to?

Answer 7

• A surface float containing CO2 belonging to the ‘portugese man of war’
• CO2 is produced by special gas cells which break down serine

Question 8

What has a submersible gas float?

Answer 8

Cephalopods such as Nautilus and Sepia

• have rigid gas filled shells
• gas chambers are emptied of fluid by active transport of Na+ across the siphuncular membrane.
• Gas diffuses into evactuated space left by removal of fluid

Question 9

What is a teleost swimbladder?

Answer 9

• They are gas filled connective tissue sacks within the gut cavity
• They are not rigid like cephalopod shells, they can expand and contract as the fish moves vertically in the water column.
• Because their volume changes, so does the buoyancy of the fish

Question 10

Two types of swimbladders?

Answer 10

A - Physotome

• Primitive and mostly fresh water
• connected to gut via pneumatic duct
• Fish can swallow air at water surface or burp it out

B - Physoclist

• More advanced and mostly marine
• Gas is secreted into the lumen of the swimbladder or resorbed by specialised circulatory circuits.

Question 11

Describe this process

Answer 11

• Secretion of lactic acid and CO2 by the cells of the gas gland
• causes release of O2 from the haemoglobin via Root shift.
• Rete mirabile acts as a countercurrent multiplier to increase O2 concentrations until they exceed those in the lumen