Gas Exchange In Fish

Question 1

Gas Exchange

Answer 1

• lower concentration of oxygen in water than air

- gas exchange surface = gills

Question 2

Structure Of Gills

Answer 2

• water with oxygen enters fish through its mouth and passes through gills
• gills made of lots of thin plates called gill filaments which large SA for exchange so increases rate of diffusion
• gill filaments covered in lots of tiny structures called lamellae which increases SA even more
• lamellae has lots of blood capillaries and a thin surface layers of cells to speed up diffusion between the water and blood

Question 3

Counter-Current System

Answer 3

• in gills blood flows through lamellae in one direction and water flows over them in the opposite direction
• water with high oxygen concentration always flows next to blood with a lower concentration of oxygen
• steep concentration gradient is maintained between the water and the blood
• as much oxygen as possible diffuses from water into blood
• blood enters lamellae with low oxygen concentration and leaves with high oxygen concentration
• water flowing towards lamella has high oxygen conc and water flowing away has low oxygen concentration