Gas exchange in single-celled organisms and insects
- Created by: Laura
- Created on: 01-05-14 13:58
View mindmap
- Gas exchange in single-celled organisms and insects
- Gas exchange in single-celled organisms
- Single-celled organisms are small and therefore have a large surface area to volume ratio
- Oxygen is absorbed by diffusion across their body which is covered only by a cell surface membrane
- Carbon dioxide diffuses out across their body surface
- To reduce water loss they have waterproof coverings over their body surfaces this is a rigid outer skeleton that is covered with a waterproof cuticle and they have a small surface area to volume ratio to minimise the area water can be lost
- Cannot use body surface to exchange gases so have developed internal network of tubes called tracheae. Supported by strengthened rings to stop them collapsing.
- Divide into smaller tubes called tracheoles. These extend throughout all the body tissues of the insect This brings oxygen straight to the respiring tissues
- Gases move in and out the tracheal system in two ways
- Along a diffusion gradient
- Ventilation. The movement of muscles in insects can create mass movements of air in and out of the trachea. This further speeds up the exchange of respiratory gases
- Gases enter and leave trachea through tiny pores, called spiracles on the body surface. They open and close with a valve.
- When the spiracles are open water can evaporate from them. For much of the time they keep these closed to prevent water loss
- Gas exchange in single-celled organisms
Comments
No comments have yet been made