B3 Flashcards
What happens to the surface area to volume ratio as the size of an organism, increases?
Decreases
What happens to the rate of diffusion as the SA:Volume ratio increases?
Increases
What happens to the rate of diffusion as the size increases?
Decreases
Why do animals in a cold environment experience less heat loss?
Larger volume therefore smaller ratio, reduced heat loss/diffusion
Why do animals in a hot environment experience increased heat loss?
Have large features to maximise SA. Increased ratio, more heat loss/diffusion
Factors affecting the rate of diffusion? [3]
- (decreased) diffusion distance
- (increased) concentration gradient
- (increased) Surface area
What two features on a fish’s gills maximise SA?
-Gill lamella
-Gill filaments
How does a fish maximise concentration gradient?
The counter current system
How does the counter current system work? [3]
- Blood flows in the opposite direction to water in the fish’s gills
- This ensures a steep concentration gradient of oxygen is maintained
- Maintained along the entire length of the gill filament
How does a fish minimise diffusion distance?
Thin lamella
How does the alveoli reduce diffusion distance to maximise gas exchange?
Alveoli and surrounding capillares are one cell thick
How does the alveoli maximise concentration gradient to maximise gas exchange?
Constant blood supply by capillaries
What two things does ventilation consist of?
Inspiration and Expiration
Process of inspiration [6]
-External intercostal & diaphragm muscles contract
- Rib cage moves upwards & outwards
- Diaphragm flattens
- Increased volume of thoracic cavity
-Lung pressure decreases
- Air flows into lungs (from area of high pressure to area of low pressure)
Process of exspiration [6]
-External intercostal & diaphragm muscles relax
- Rib cage moves downwards & inwards
- Diaphragm becomes curved
- Decreased volume of thoracic cavity
-Lung pressure increases
- Air flows out of lungs (from area of high pressure to area of low pressure- down pressure gradient)
