GAS EXCHANGE IN FISH Flashcards
What are the gills?
Organs of gas exchange in fish.
What is the operculum?
The bony protective flap that covers the gills of bony fish.
What is a counter-current exchange system?
System in which 2 fluid components flow in opposite directions and exchange of properties between the fluids occurs.
Why is the operculum important?
Important in maintaining flow of water over the gills, even when the fish is stationary.
What about gills makes them well adapted for successful gas exchange?
Large surface area for diffusion; good blood supply to maintain conc. gradient and thin walls that give short diffusion distances.
Where are the gills contained?
In the gill cavity.
Describe gill filaments.
Fragile gill filaments occur in large stacks, they need water to keep them apart and so to expose the large surface area.
What is the main site of gas exchange in the gills?
The gill lamellae.
What give the gill filaments there large surface area?
The gill lamellae.
Why do fish require a constant flow of water?
Diffusion tends to be slow, so to get all of the oxygen they need for cellular respiration, flow must be constant.
Why can’t a fish survive long when out of water?
The gill filaments all stick together. The remaining exposed surface area is not big enough for effective gas exchange.
How do cartilaginous fish differ?
They do not have an operculum. They have to swim constantly to keep water flowing through their mouths and over their gills.
How have bony fish evolved a system using the operculum so that when they are not moving they can still ventilate their gills?
- The mouth opens, closing the operculum valve. This increases the volume of the buccal chamber, so pressure falls and water is drawn in.
- The mouth closes, opening the operculum valve. This decreases the volume of the buccal chamber, so pressure increases forcing water out through operculum pass the gills.
How do overlapping gill filaments make the gas exchange more effective?
If the water passes over the gills to quickly it limits the amount of oxygen and carbon dioxide that can be exchanged. Tips of adjacent gill filaments actually overlap increasing the resistance to flow of water. Slowing the flow down gives more time for the exchange of gases to take place.
