3.2.2: Gas exchange in fish

Question 1

what is the specialised gas exchange surface in fish

Answer 1

gills

Question 2

where is the gill in a fish located

Answer 2

in the buccal cavity in the mouth, the gill is behind the operculum (flap) and behind the opercula cavity

Question 3

describe the structure of a gill

Answer 3

multiple gill plates which are perpendicular on the thin plates called gill filaments

Question 4

explain how the gills of a fish are adapted to provide a large surface area

Answer 4

each bony gill has two stacks of thin plates called filaments, this provides a large surface area

Question 5

explain how the gills of a fish are adapted to reduce the length of the diffusion pathway

Answer 5

each gill plate has a single layer of flattened cells which have capillaries that are very close to the surface so oxygen has a short distance to diffuse from water into the blood

Question 6

explain how the gills of a fish maintain a steep concentration gradient

Answer 6

counter current system
blood and water flow over the gill plates in opposite directions, no equilibrium is reached and so there will always be more oxygen in water than in blood. Diffusion of oxygen occurs across the entire length of the gill plate. You get a higher maximum saturation of oxygen in the blood than parallel flow and so is more efficient

Question 7

what is a key point to remember when drawing a graph for counter current flow or parallel flow

Answer 7

never start oxygen in blood at zero

Question 8

what main difference between parallel and counter current flow means that counter current flow is more efficient

Answer 8

in counter current flow, no equilibrium is reached whereas in parallel flow, it occurs until an equilibrium is reached, so you get a higher maximum saturation of oxygen in the blood via counter current flow than parallel flow