In which of the following organisms does oxygen diffuse directly across a respiratory surface to cells, without being carried by the blood?
a. A grasshopper
b. A whale
c. An earthworm
d. A mouse

Which of the following is the main difference between your cardiovascular system and that of a fish?

a. Your heart has two chambers; a fish heart has four.

b. Your circulation has two circuits; fish circulation has one.

c. Your heart chambers are called atria and ventricles.

d. Yours is a closed system; the fish's is an open system.

Describe the disadvantages of an open circulatory system relative to a closed circulatory system.

One feature that amphibians and humans have in common is

a. The number of heart chambers.

b. A complete separation of circuits for circulation.

c. The number of circuits for circulation.

d. A low blood pressure in the systemic circuit.

If a molecule of CO₂ released into the blood in your left toe is exhaled from your nose, it must pass through all of the following except

a. The pulmonary vein.

b. The trachea.

c. The right atrium.

d. The right ventricle.

What is the function of the cilia in the trachea and bronchi?

a. To sweep air into and out of the lungs

b. To increase the surface area for gas exchange

c. To dislodge food that may have slipped past the epiglottis

d. To sweep mucus with trapped particles up and out of the respiratory tract

What do the alveoli of mammalian lungs, the gill filaments of fish, and the tracheal tubes of insects have in common?

a. Use of a circulatory system to transport gases

b. Respiratory surfaces that are infoldings of the body wall

c. Countercurrent exchange

d. A large, moist surface area for gas exchange

The diaphragm is a large sheet of muscle that helps move air in and out of your lungs. Breathing is automatically controlled by the brain, but you can choose to hold your breath or breathe deeper. What kind of muscle do you suppose makes up the diaphragm? (Explain your answer.)

Which of the following is not a true statement about open and closed circulatory systems?

a. Both systems have some sort of a heart that pumps a circulatory fluid through the body.

b. A frog has an open circulatory system; other vertebrates have closed circulatory systems.

c. The blood and interstitial fluid are separate in a closed system but are indistinguishable in an open system.

d. Some of the circulation of blood in both systems results from body movements.