Question 1

Which of the following best explains why diffusion alone is insufficient for transporting substances in large, complex animals?

Accepted Answer

Diffusion is only efficient over small distances because the time required increases with the square of the distance ($$t \propto d^2$).

Question 2

Which of the following is a key difference between open and closed circulatory systems?

Accepted Answer

In open systems, the circulatory fluid directly bathes organs, while in closed systems, blood is confined to vessels.

Question 3

Which animal would you expect to have the highest systolic blood pressure, and why?

Accepted Answer

A giraffe, because it needs to pump blood up its long neck against gravity.

Question 4

What is the main advantage of double circulation in mammals compared to single circulation in fish?

Accepted Answer

Double circulation maintains higher blood pressure in organs, allowing for more efficient oxygen delivery.

Question 5

Which of the following best describes the function of the sinoatrial (SA) node in the mammalian heart?

Accepted Answer

It acts as the pacemaker, setting the rate and timing of cardiac muscle contractions.

Question 6

A patient has a blood pressure reading of 150/95 mm Hg. Which of the following statements is correct?

Accepted Answer

The systolic pressure is 150 mm Hg, and the diastolic pressure is 95 mm Hg.

Question 7

Which of the following mechanisms helps return blood to the heart through veins, especially from the lower body?

Accepted Answer

Contraction of skeletal muscles and one-way valves in veins.

Question 8

Which of the following is a correct sequence of blood flow through the mammalian heart and lungs?

Accepted Answer

Right atrium → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium → left ventricle → aorta

Question 9

Which of the following best explains why capillaries are the primary site of exchange between blood and tissues?

Accepted Answer

Capillaries have thin walls and a large total cross-sectional area, allowing efficient exchange of materials.

Question 10

A person with sickle-cell disease is likely to experience which of the following symptoms, and why?

Accepted Answer

Reduced oxygen delivery to tissues due to deformed erythrocytes blocking blood vessels.

Question 11

Which of the following statements about atherosclerosis is correct?

Accepted Answer

It is caused by the buildup of fatty deposits (plaque) in arteries, leading to reduced blood flow.

Question 12

Which of the following best describes the Bohr shift?

Accepted Answer

A decrease in blood pH (increase in CO$$_2) $$lowers hemoglobin's affinity for O$$_2$$, facilitating oxygen release to tissues.

Question 13

Which of the following is a unique adaptation of diving mammals that allows them to remain underwater for extended periods?

Accepted Answer

They store large amounts of oxygen in myoglobin within their muscles.

Question 14

Which of the following best explains why fish gills are highly efficient at extracting oxygen from water?

Accepted Answer

They use a countercurrent exchange system, maintaining a gradient that favors O$$_2$$ diffusion into the blood.

Question 15

Which of the following is a correct statement about the control of breathing in humans?

Accepted Answer

The medulla oblongata regulates breathing rate in response to changes in blood pH, which reflects CO$$_2$$ levels.

Question 16

Which of the following best describes the role of platelets in the blood?

Accepted Answer

They are cell fragments that function in blood clotting.

Question 17

A person is prescribed statins after a heart attack. What is the primary function of these drugs?

Accepted Answer

They reduce LDL cholesterol levels, lowering the risk of further cardiovascular events.

Question 18

Which of the following is a function of the lymphatic system in relation to the circulatory system?

Accepted Answer

It returns excess interstitial fluid (lymph) to the bloodstream and helps filter pathogens.

Question 19

Which of the following best explains why amphibians can survive with a three-chambered heart?

Accepted Answer

They can supplement lung respiration with gas exchange through their skin (pulmocutaneous circuit).

Circulation and Gas Exchange: Structure, Function, and Adaptations

Study Guide - Practice Questions