fish respiration

Question 1

what is the advantage of the gills?

Answer 1

large SA and good blood supply
- ram ventilation forces water over gills

Question 2

what is the advantage of gill filaments?

Answer 2

large SA

Question 3

what is the advantage of gill lamellae?

Answer 3

good blood supply
- exchange site

Question 4

what is the gill operculum?

Answer 4

flap covering gills

Question 5

what are the processes of the buccal cavity?

Answer 5

1. mouth opens, cavity lowers
2. volume increases and pressure decreases so water enters
3. opercular cavity expands
4. cavity rises and pressure increases so water moves over gills
5. cavity lowers

Question 6

what are the adaptations of the fish respiratory system?

Answer 6

gill tips overlap = increased resistance which allows time for exchange
countercurrent flow = maintains gradient so a higher level of oxygen saturation is achieved

Question 7

what is the purpose of having a countercurrent flow?

Answer 7

if parallel, diffusion occurs until equilibrium is reached of blood and water so the net movement of oxygen stops

Question 8

explain how the gills of a fish are adapted for efficient gas exchange (6 marks)

Answer 8

• large surface area due to filaments which maximises rate of exchange
• rich blood supply from lamellae allow a steep concentration gradient
• thin layers decrease diffusion path
• circulation replaces blood
• ventilation replaces water
• countercurrent flow maintains oxygen diffusion

Question 9

suggest why the concentration of oxygen is higher in surface waters than water close to seabed (2 marks)

Answer 9

• air has a high concentration of oxygen and mixes with surface water
• plants near surface have light so produce more oxygen by photosynthesis