Gas exchange in fish Flashcards
What percentage of water is O2
0.7, relatively low (1/30 of that in air)
Limitations of gas exchange through water compared to air 3
Low conc of O2
Denser than air
More viscous than air
Characteristics of bony fish x5
Covered in scales so no gas exchange throught surface
Contain gills in the opercular cavity
Skeleton of bones
Sea and fresh water
Counter current system
Characteristics of gills x3 and benefits
Made of numerous folds: increase SA
Good blood supply: maintain steep conc grad
Thin layer of cells separating blood from outside water: short diffusion path
Characteristics of cartilaginous fish x5
Skeleton of cartilage
Live in sea
Covered in scales
Have gill cleats
Parallel system of gas exchange
Two types of fish?
Cartilaginous and bony
Parallel gas exchange?
Blood and water travel in the same direction
3 parts of a gill
gill filament, gill arch, gill rakers
Function of gill arch
Bony structure to support the gill filaments and gill rakers
Structure and function of gill filaments
Increase SA, filled with blood, short diffusion path. Location of gas exchange
Function of gill rakers
filter water, trap prey/ particles
How many pairs of gills arefound in the pharynx
4
Pharynx?
throat
How many gill filaments along each gill
2: a double row
What exactly is the gas exchange surface of fish
The gill plates on the gill filaments
Describe the process goals exchange in fish
O2 from water passes through gill plates into capillaries
CO2 from blood passed out into water
Blood vessels carry the oxygenated blood away
Why can fish survive out of water
Gill filaments stick together bc of cohesion between water molecules bc gills are moist
Reduces SA of filaments
Less efficient gas exchange
Why do fish ventilate
To keep water flowing over the gills for conc grad for efficient gas exchange
Two stages of ventilation
inhale and exhale
Explain inhale of ventilation 5
Mouth opens
Operculum closes
Floor cavity lowers
So volume of mouth has increased and pressure falls
Water flows into mouth
Explain the exhale of ventilation
Mouth closed
Operculum opens
Floor of mouth raised
So volume of mouth decreases and pressure increases
Water flows out of the gills
What does countercurrent flow mean
Blood flow in capillaries is in the opposite direction to that of the water throught the gills
what is the advantage of counter current flow
The conc grad is maintained across the whole length of the gill filament so gas exchange occurs across the whole length
What types of gills do tadpoles have
External gills
Characteristics of external gills
Highly branched
Short diffusion path
Vascularised
Movement provides water currents
Why cant tadpoles stop moving
bc movement is what provides the current over their gills
What is the operculum
gill covers/ valves
Gill structures in cartilaginous fish
Gills in 5 spaces either side called gill pouches which open to the outside at the gill slits
Why is ventilation in cartilaginous fish less efficient than in bony fish
No special mechanism to force water over gills, must keep swimming for flow
Have parallel flow
What % of O2 do bony fish gills extract from water
80%
how many pairs of gills in the pharynx
4 pairs
