1. G AS E XCHANGE The exchange of Oxygen and Carbon dioxide What characteristic do all respiratory surfaces have in common? They must be moist Respiratory surfaces in different animals are adapted for maximal gas exchange capacity

2. G ILLS Ventilation – increasing flow over the respiratory surface What is the advantage of countercurrent exchange? How can insects meet their high metabolic demands for oxygen with an open circulatory system?

3. L UNGS Connects to circulatory system Located in thoracic cavity, near the heart Describe the pathway of oxygen to the lungs. What is the passage of oxygen as it enters your nasal passageway and is used by tissues in your big toe? How do mammals ventilate their lungs? What is so special about the avian respiratory system?

4. Control of Breathing