Chapter 36

The most abundant gas in the atmosphere is _____ a. nitrogen b. carbon dioxide c. oxygen d. hydrogen

Respiratory proteins such as hemoglobin _____ a. contain metal ions b. occur only in vertebrates c. increase the efficiency of oxygen transport d. both a and c

In insects, most gas exchange occurs at _____ a. the tips of tracheal tubes b. the body surface c. gills d. paired lungs

Countercurrent flow of water and blood increases the efficiency of gas exchange in _____ a. fishes b. amphibians c. birds d. all of the above

In human lungs, gas exchange occurs at the _____ a. two bronchi b. pleural sacs c. alveolar sacs d. both b and c

When you breathe quietly, inhalation is _____ and exhalation is _____ a. passive; passive b. active; active c. passive; active d. active; passive

During inhalation _____a. the thoracic cavity expands b. the diaphragm relaxes c. atmospheric pressure declines d. both a and \(c\)

Most oxygen being transported in blood _____ a. is bound to hemoglobin b. combines with carbon to form carbon dioxide c. is in the form of bicarbonate d. is dissolved in the plasma

At high altitudes, _____ a. nitrogen bubbles out of the blood b. hemoglobin has fewer oxygen-binding sites c. atmospheric pressure is lower than at sea level d. both b and c