Biology › Exchange surfaces and gas exchange

Exchange surfaces and gas exchange

Unit B07 · 3 lessons.

Notes

Illustrated notes for each topic in this unit, with worked examples and a checklist of objectives.

• Surface area to volume ratio: why size limits diffusion
  Surface area to volume ratio and how it falls as an organism gets larger, the effect of shape as well as size, Fick's law as a proportionality, why…
• Gas exchange in mammals: lungs and ventilation
  The route from trachea to alveolus, with the cartilage, ciliated epithelium, goblet cells, smooth muscle and elastic fibres found at each level; the…
• Gas exchange in insects, fish and plants
  The insect tracheal system from spiracle to tracheole and how tracheal fluid moves during activity, the structure of a bony fish gill and why…

Practical work

The practical capabilities this unit's work belongs to, each with its techniques, its calculations and the errors that cost marks.

• Dissection and biological drawing
• Non-living models of diffusion, osmosis and surface area