Q: Which of the following is a correct calculation of the partial pressure of oxygen at sea level, where atmospheric pressure is 760 mm Hg and oxygen makes up 21% of the air?

$$0.21 \times 760 = 160 mm Hg$$

Question 1

Which of the following best explains why small aquatic animals like Hydra do not require a circulatory system?

Accepted Answer

Their bodies are only one or two cell layers thick, allowing direct exchange of materials with the environment.

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 the organs, while in closed systems, blood is confined to vessels.

Question 3

A fish is found to have a two-chambered heart and single circulation. Which of the following best describes the path of blood flow in this fish?

Accepted Answer

Heart → gills → body → heart

Question 4

Which of the following statements about double circulation in mammals is correct?

Accepted Answer

The right side of the heart pumps blood to the lungs, and the left side pumps blood to the body.

Question 5

A patient has a blood pressure reading of 120/70 mm Hg. What do these numbers represent?

Accepted Answer

120 mm Hg is the systolic pressure, and 70 mm Hg is the diastolic pressure.

Question 6

Which of the following best describes the function of precapillary sphincters?

Accepted Answer

They regulate the flow of blood into capillary beds.

Question 7

Which of the following is a correct calculation of the partial pressure of oxygen at sea level, where atmospheric pressure is 760 mm Hg and oxygen makes up 21% of the air?

Accepted Answer

$$0.21 	imes 760 = 160 mm Hg$$

Question 8

Why do aquatic animals such as fish require more energy for gas exchange compared to terrestrial animals?

Accepted Answer

Oxygen is less soluble in water, and its concentration decreases with increasing temperature.

Question 9

Which of the following best explains the advantage of countercurrent exchange in fish gills?

Accepted Answer

It maintains a gradient that favors the diffusion of oxygen from water into blood along the entire length of the gill.

Question 10

A person is exposed to high altitude, where oxygen levels are low. Which hormone is released to stimulate red blood cell production, and where is it produced?

Accepted Answer

Erythropoietin (EPO), produced by the kidneys

Question 11

Which of the following is NOT a function of plasma proteins in blood?

Accepted Answer

Transport of oxygen

Question 12

During vigorous exercise, the pH of blood decreases due to increased CO2 production. How does this affect hemoglobin's affinity for oxygen?

Accepted Answer

Hemoglobin's affinity for oxygen decreases, facilitating the release of O2 to tissues (Bohr shift).

Question 13

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

Accepted Answer

They initiate the clotting process by forming a plug and releasing chemicals that activate clotting factors.

Question 14

A patient has a genetic disorder that prevents the production of functional fibrinogen. What would be the most likely consequence?

Accepted Answer

Inability to form stable blood clots

Question 15

Which of the following best explains why veins have valves, but arteries do not?

Accepted Answer

Valves in veins prevent the backflow of blood due to lower pressure, especially in the limbs.

Question 16

Which of the following is a correct sequence of events in the cardiac cycle?

Accepted Answer

Atrial and ventricular diastole → atrial systole → ventricular systole

Question 17

Which of the following best describes the main function of the lymphatic system in relation to the circulatory system?

Accepted Answer

It returns excess interstitial fluid to the bloodstream.

Question 18

Which of the following is a correct description of how mammals ventilate their lungs?

Accepted Answer

By negative pressure breathing, pulling air into the lungs as the diaphragm contracts

Question 19

Which of the following best explains why Weddell seals can dive for long periods?

Accepted Answer

They have a high blood to body volume ratio and store oxygen in myoglobin proteins in their muscles.

Circulation and Gas Exchange in Animals

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