Specialised exchange surfaces Flashcards
Why do multi-celled organisms need a specialised exchange surface?
- There metabolic rate is usually high (especially in mamals) so the oxygen demand and carbon dioxide productions is high.
- The surface area to volume ratio (SA:V) is small compared to single-celled organisms. So the distance between the cells were the oxygen is needed and the supply of oxygen is too great.
https://www.youtube.com/watch?v=CqNb04a_-PI
How do you work out the volume of a cubiod?
Length x width x hight = V
How do you work out the volume of a cylinder?
(The area of the cross section) πr2 x height = V
How do you work out the volume of a sphere?
4/3πr3 = V
How do you work out the surface area of a cubiod?
(4 x length x height) + (2 x heigt x width) = SA
How do you work out the surface area of a cylinder?
(πD x height) + (πD2) = SA
How do you work out the surface area of a sphere?
4πr2 = SA
What are the characteristic features of an effective exchange surfaces?
- Increased surface area
- Thin walls
- Good blood supply
- Ventilation to maintain diffusion gradient
Explain why a good exchange system needs an increased surface area?
It’s so that multi-cellular organisms with a small surface area to volume ratio has more surface for the gas to diffuse. A larger surface area increases the gas exchange rate.
https://www.youtube.com/watch?v=l2D240zy6jI
Explain why a good exchange system needs thin layers?
Thin walls mean that there is a shorter distance for the gases to diffuse. Making the process faster and more efficient.
https://www.youtube.com/watch?v=l2D240zy6jI
Explain why a good exchange system needs a good blood supply?
Having a good blood supply ensures that the substances are constantly delivered to and removed from the exchange surfaces. This creates a steeper concentration gradient which means that diffusion is faster.
https://www.youtube.com/watch?v=l2D240zy6jI
Explain why a good exchange surface needs ventilation?
Ventilation heps to maintain a diffusion gradient for gases. As the air flow moves the oxygen into the lungs and the carbon dioxide out (keeping a steep concentration gradient).
