Gas Exchange in Fish Flashcards
Why can’t fish use their body surface for gas exchange?
Fish have a waterproof and gas - tight outer covering and small surface area to volume ratio, making diffusion across the body surface ineffective
What specialised gas exchange surface have fish evolved?
Gills - an internal gas exchange surface adapted for efficient oxygen uptake and carbon dioxide removal
Why do fish need a specialised gas exchange system?
Their small surface area to volume ratio means their body surface cannot provide enough oxygen or remove enough carbon dioxide
Where are the gills located in fish?
Inside the body, behind the head
What are the main structural components of fish gills?
- Gill filaments - make up gills, stacked up like pages in a book
- Gill lamellae - positioned at right angles to the filaments to increase the surface area
How does water flow over the gills?
Water is taken in through the mouth, forced over the gills, and exits through an opening on each side of the body
What is countercurrent flow in fish gills?
The flow of water over the gill lamellae and the flow of blood within gill lamellae are in opposite directions
What would happen if water and blood flowed in the same direction in fish gills?
Far less gas exchange would occur because the diffusion. gradient would only be maintained for part of the gill
Why is countercurrent flow important in fish gills?
It ensures maximum gas exchange by maintaining a diffusion gradient across the entire length of the gill lamellae
What is the countercurrent exchange principle in fish gills?
It is the system where blood and water flow in opposite directions over the gill lamellae to maximise oxygen uptake
How does countercurrent flow maintain oxygen diffusion in fish gills?
- Oxygen - rich water meets blood that is already partially oxygenated, so oxygen diffuses into the blood
2.Oxygen - poor blood metts water that still contains some oxygen, so oxygen continues to diffuse into the blood
Why does countercurrent flow allow for efficient gas exchange?
It maintains a diffusion gradient across the entire gill lamellae, allowing fish to absorb about 80% of the oxygen from the water
What would happen if fish gills used parallel flow instead of countercurrent flow?
The diffusion gradient would only be maintain across part of the gill lamellae, and the blood would absorb only 50% of the available oxygen instead of the 80%
