2.2: Adaptations for gas exchange in fish Flashcards
Why do fish require specialised gas exchange?
They have a smaller surface area to volume ratio, relatively active so have high metabolic rates making oxygen requirements high, and require a ventilation mechanism to maintain concentration gradients for gas exchange.
Do fish have a higher surface area to volume ratio or a smaller surface area to volume ratio?
Smaller surface area to volume ratio.
Do fish have a high oxygen requirement? Why?
Yes, because they have a high metabolic rate.
Why do fish require a ventilation mechanism?
In order to maintain concentration gradients for gas exchange.
What is the first step in ventilation in fish?
Mouth opens, floor of buccal cavity lowers so volume increases, pressure decreases and water rushes in.
What is the second step in ventilation in fish?
Mouth closes, floor of buccal cavity raises, increasing pressure pushing water over the gills.
What is the third step in ventilation in fish?
Pressure in gill cavity increases and water forces operculum open and leaves through it.
What do gill rakers do?
Gill rakers prevent large particulates entering and blocking the gills.
What do gill filaments do?
Create a high surface area.
What is counter current flow?
Blood and water flow in opposite directions across the gill plates. This maintains a concentration gradient for efficient diffusion as diffusion cannot reach equilibrium.
