3. Insect & Fish Gas Exchange Flashcards
Spiracles
Small holes in an insect’s exoskeleton. Air enters through them.
The spiracles open to a network of fine tubes called…
tracheae. These are lined with rings of chitin
Why are the tracheae lined with rings of chitin?
Strength - so that it doesn’t collapse.
Ensures airways are always open.
Tracheae sub-divide into tubes of smaller diameter called…
tracheoles - these are UNLINED
Where do the tracheoles end?
At the insect’s body cells
The entire tracheal system of an insect relies on…
a diffusion gradient
Ventilation of small insects/insects that aren’t very active
They are able to rely on enough oxygen reaching their tissues through their spiracles
Ventilation of active insects
They need to speed up the movement of oxygen to their tissues, so they pump their abdomens in & out using muscles.
What does the pumping of the abdomen in active insects do?
This helps fresh air to enter the tracheae.
Adaptations of tracheoles
- Very large number of fine tracheoles: large SA
- Thin walls: short diffusion pathway
- Use of oxygen and production of CO2 sets up: steep diffusion gradient
- Ends of tracheoles are fluid-filled: gases can dissolve so rate of diffusion is faster
What happens to the tracheoles at rest vs during flight?
At rest: water fills the ends of the tracheoles
During flight: the water diffuses into the muscle
4 other adaptations of insect gas exchange system when they fly
- Muscle cells anaerobically respire & produce lactic acid
- Lowers water potential of muscle cells
- Water moves by osmosis from tracheoles into muscle cells
- Reduces diffusion distance so diffusion of oxygen is much faster
EXAM QUESTION: Describe how an insect is able to obtain oxygen and limit water loss (6)
- Air enters through spiracles
- Through tracheae
- Diffusion gradient in trachea
- Tracheae associated with all cells/closely associated with cells
- Oxygen diffuses into cells
- Ventilation replacing air in tracheae
- Body covered with waterproof waxy layer/cuticle
- Spiracles are able to close
How do fish gills extract oxygen from the water?
Counter current mechanism
Units of partial pressure of oxygen
mm Hg
What is partial pressure?
The pressure of a single gas in the mixture as if that gas alone occupied the container. Also the pressure exerted by a single gas in a mixture of gases
Bony fish have:
- waterproof scales
2. small SA:vol ratio
Fish gill system in a nutshell
Oxygenated water enters through mouth -> water passes over gills -> deoxygenated water leaves
Where are gills?
In a cavity on the side of a fish’s head
How many pairs of gill arches are their on each side of a fish’s head?
4
On each arch are ____ series of stacked ______ splayed out as a ______
two; gill filaments; V
Disc-like projections called ________ are on the upper and lower surfaces of each ________
gill lamellae; gill filament
Where exactly is gas exchange carried out in the gills?
Across the surface of the lamellae
4 gill adaptations
- Very large SA
- Single layer of thin epithelial cells
- Dense network of capillaries carrying blood running underneath (close to the surface)
- Fish pushes water over the gills to ensure constant ventilation
