CIE IGCSE Biology: 复习笔记：11.1.1 Features of Gas Exchange Surfaces
- The surfaces where gas exchange occurs in an organism are very different and different organisms have evolved different mechanisms for getting the gases to the gas exchange surface depending on size, where they live etc.
- All gas exchange surfaces have features in common
- These features allow the maximum amount of gases to be exchanged across the surface in the smallest amount of time
- They include:
- Large surface area to allow faster diffusion of gases across the surface
- Thin walls to ensure diffusion distances remain short
- Good ventilation with air so that diffusion gradients can be maintained
- Good blood supply to maintain a high concentration gradient so diffusion occurs faster
The alveolus is the gas exchange surface in humans
You may notice that several of the features of alveoli that make them suited to their function are the same as those that make villi suited to their function; or root hair cells suited to their function – the reason for this is because all of these structures are involved in transporting substances across their surfaces – by diffusion, active transport, osmosis or a combination.So if you learn the features for one, you also know many of the features of the others!