ventilation in fish

Question 1

why has gas exchange in bony fish evolved?

Answer 1

-they are large and active so high oxygen demand
-low surface area : vol
-scaly surface doesn’t allow gases to pass through
-lower oxygen concentration in water than air

Question 2

describe what happens in fish when they breath in

Answer 2

-fish opens its mouth/buccal cavity
-the floor of the mouth moves down
-volume inside buccal cavity increases
-pressure inside buccal cavity decreases
-water flows inside
-operculum is closed

Question 3

describe what happens when a fish breaths out

Answer 3

-fish closes mouth
-the floor of the mouth moves up
-this decreases volume in buccal cavity
-and increases pressure in the buccal cavity
-water is pushed through the gills
-operculum is opened reducing pressure in operculum cavity helping water flow through gills

Question 4

how are gills in fish specialised for gas exchange

Answer 4

-fill lamellar is where gas exchange takes place, water flows between them and oxygen diffuses from the water into blood stream and co2 out

-gill filaments= thin =short diffusion distance
-gill lamellar= increase surface area
-good blood supply in lamellae close to surface =short diffusion distance

Question 5

what is the purpose of countercurrent flow in fish

Answer 5

maintains steep concentration gradient across the whole of gill lamellae

Question 6

explain countercurrent flow

Answer 6

-blood flows opposite direction to water so there’s always more oxygen in water that blood= diffusion across whole of lamellae

-100% saturation achieved

Question 7

explain parallel flow

Answer 7

-blood flows same direction as water
-equilibrium reached at end of flow =there’s diffusion across only a part of gill lamellae
-50% saturation achieved