Chapter 34

Describe how fish gills work, including the basic concept of countercurrent exchange. Why is this process important to allow fish to extract oxygen from water?

How does the respiratory system of a frog change when it undergoes metamorphosis? Why are these changes necessary?

Describe the respiratory system of birds and how it allows oxygen-rich air to enter the lungs during both inhalation and exhalation.

Explain some important characteristics of animals in moist environments that make specialized respiratory systems unnecessary.

How is breathing initiated? How are breathing rate and depth adjusted, and which blood gas is most tightly regulated?

Discuss the structures and functions of gills, tracheae, and lungs.

Compare bulk flow and diffusion. Explain how bulk flow and diffusion interact to promote gas exchange between air and blood and between blood and tissues.

Compare \(\mathrm{CO}_{2}\) and \(\mathrm{O}_{2}\) transport in the blood. Include the source and destination of each, and what physiological process makes gas exchange necessary.

Why do you think the alveoli cover a surface area as large as 1,500 square feet in an adult?