Gas exchange in insects and fish Flashcards
How does gas exchange occur in insects
Gas enters and leaves trachea through tiny pores called spiracles
Tracheae are supported by strengthened rings to keep them open, they divide into dead end tubes called tracheoles.
Tracheoles extend deep into body tissues so oxygen moves directly from the atmosphere to body cells.
How does diffusion aid gas exchange in insects
Gases move in and out by diffusion down a diffusion gradient as oxygen is constantly used and carbon dioxide generated by respiration thus maintaining a concentration gradient.
How does the contraction of muscles aid gas exchange in insects
The contraction of muscles in the insect can squeeze the trachea enabling mass movement (mass transport) of gases in and out.
How does the water at the end of tracheoles aid gas exchange in insects
End of tracheoles filled with water so when muscles respire anaerobically they generate soluble lactate that dissolves and lowers water potential in the muscle cells.
This draws water out of the tracheoles into cells by osmosis down a water potential gradient. This reduces the water and increases the length of air in the tracheoles.
Diffusion is faster in gas than liquid so diffusion is more rapid.
What are the disadvantages of insects gas exchange system
1) When spiracles are open water vapour can evaporate so for much of the time they have to be kept closed and just periodically opened.
2) For efficient gas exchange the diffusion pathway must be short so insects have to be small.
Describe the structure of the fishes gas exchange system
Gills are made of stacks of gill filaments.
On these gill filaments at right angles to them are gill lamellae to increase the surface area.
The flow of water over the gill lamella and flow of blood inside gill lamella are in opposite directions – counter current flow
(Familiarise yourself with image of fishes gas exchange system - search online)
What is meant by the counter current flow between the blood and water in fishes gas exchange system
Blood with high oxygen concentration meets water with its maximum oxygen concentration so diffusion takes place.
Blood with its lowest oxygen concentration meets water which has had most oxygen removed so again diffusion takes place.
How is the counter current flow in fishes gas exchange system advantageous
It maintains a diffusion gradient all the way across the gill lamella and 80% available oxygen is absorbed.
Where is the site of gas exchange in fish
the gill filaments
What are gill rakers
appendages (projecting parts) along the front edge of the gill arch
What do gill arches do
Support the gills
What are gill filaments
the thin, delicate, thread-like structures that are attached to the gill arches.
What are gill arches
The bony or cartilaginous structures that support the entire gill structure.
What do gill rakers do
Filter out debris and larger particles from the water, preventing them from entering the gill filaments and damaging the respiratory surfaces.
