A series of approaches to cover these re-introduced topics in the new AS-level Biology A course.
It looks at:
1. understanding key terms and how a unidirectional flow of water is maintained over the gills.
2. explaining why a countercurrent flow is more efficient at exchanging oxygen in fish than a concurrent flow.
3. suggests dissection activities to examine the gas exchange system of a bony fish and/or insect trachea.
4. the ventilation system in insects explaining how they are adapted for efficient gas exchange.