gas exchange in fish

Question 1

describe and explain how fish maintain a flow of water over the gill. (4)

Answer 1

to get water into the fish, the mouth opens, the opercular valves shuts. The buccal cavity is lowered to get more water into the mouth - water enters the mouth due to the increased volume and decreased pressure created in the mouth due to the lowering of the buccal cavity. - When enough water is acquirred the mouth shuts and the buccal cavity is raised which decreases the volume in the mouth and increases the pressure therefore water diffuses from high to low pressure into the opercular cavity. The operculum valves now open and forces the water across the gills. The gills now intake the oxygen into the blood that runs in the capillaries that are located in the gill fillaments

Question 2

what is the gas exchange surface in a fish ?

Answer 2

the gill

Question 3

what is on the surface of gill fillaments that increase the surface area available for gas exchange ?

Answer 3

secondary lamellae

Question 4

what substances does gas exchange occur between ?

Answer 4

gas exchange occurs between water and blood that runs in the capillaries in gill filaments

Question 5

what kind of gas exchange adaptation do boney fish have ?

Answer 5

boney fish have a counter current flow mechanism

Question 6

what happens in a counter current system ?

Answer 6

counter current system maintains a concentration gradient over the full length of the gill because water and blood are always flowing in opposite directions. blood is always moving next to water which has more oxygen in it.

Question 7

what does the counter current system allow the fish to do ?

Answer 7

it means that more oxygen can enter the blood and so more aerobic respiration can occur