Fish Gas Exchange

Question 1

Structure of Gills

Answer 1

• in the gill cavity and covered by operculum
• gill filaments stacked to form gill plates
  need flow of water to keep them apart
• gill lamellae at right anfles from filaments to increase surface area of gills for gas exchange
  main site gas exchange
  few cells thick and have blood capillaries
• bony gill arch supports gills

Question 2

What is counter current flow

Answer 2

blood flows different direction to water
so blood always comes into contact with water at higher oxygen content
for steep diffusion gradient to be maintained along gill structure

Question 3

Why do bony fish need gills

Answer 3

very active so high oxygen demand so gills have to take oxygen from water and remove co2

Question 4

How does bony fish exchange system work

Answer 4

• mouth opens
• buccal cavity floor lowered
  increased volume so decreased pressure so water moves in
• same time opercular cavity expands lowering pressure
• buccal cavity floor moves up increasing pressure so water moves over the gills
• mouth closes and operculum opens
• opercular cavity move inwards to increase pressure and force water over gills and out of operculum
• buccal cavity floor moves up maintaining flow of water over gills

Question 5

What are gill adaptions?

Answer 5

gill lamellae increase surface area
tips of gill filaments overlap for increased resistance to slow water movement over gills
countercurrent exchange system for steeper concentration gradient maintained