Question 1

Which of the following best describes the four steps of gas exchange in animals, in the correct order?

Accepted Answer

Ventilation, gas exchange, circulation, cellular respiration

Question 2

Why do large animals require a circulatory system, while small or thin animals like flatworms do not?

Accepted Answer

Diffusion is only efficient over small distances, so large animals need a circulatory system to transport gases and nutrients.

Question 3

Which of the following equations correctly represents the relationship between diffusion time and distance?

Accepted Answer

$$t \propto d^2$

Question 4

Which animal group is most likely to have an open circulatory system, and why?

Accepted Answer

Clams, because they are relatively sedentary and have low oxygen demands.

Question 5

In a closed circulatory system, which type of vessel is responsible for the exchange of gases, nutrients, and wastes with tissues?

Accepted Answer

Capillaries

Question 6

What is the main advantage of a four-chambered heart in mammals and birds?

Accepted Answer

It completely separates oxygen-rich and oxygen-poor blood, maximizing oxygen delivery to tissues.

Question 7

Which of the following best explains why fish have a single circulatory circuit, while mammals have a double circuit?

Accepted Answer

Fish live in water and have less need to overcome gravity, while mammals need separate circuits to efficiently deliver blood to lungs and body.

Question 8

Which of the following statements about hemoglobin is correct?

Accepted Answer

Hemoglobin increases the amount of oxygen that can be carried by blood.

Question 9

A patient has a defect in their AV (atrioventricular) valves. What is the most likely consequence?

Accepted Answer

Backflow of blood from ventricles to atria during ventricular contraction, causing a heart murmur.

Question 10

Which of the following best describes the function of baroreceptors in the circulatory system?

Accepted Answer

They detect changes in blood pressure and trigger compensatory responses.

Question 11

Which of the following equations correctly calculates cardiac output ($$CO) in $$humans?

Accepted Answer

$$CO = HR 	imes SV$$

Question 12

Why is countercurrent exchange in fish gills more efficient than concurrent exchange?

Accepted Answer

It maintains a favorable partial pressure gradient for oxygen across the entire gill surface.

Question 13

Which of the following is a key feature of the mammalian respiratory system that increases the efficiency of gas exchange?

Accepted Answer

The presence of millions of alveoli, which greatly increase surface area.

Question 14

A person is exposed to high altitude, where the partial pressure of oxygen is lower. Which of the following is a likely physiological response?

Accepted Answer

Increased breathing rate to compensate for lower oxygen availability.

Question 15

Which of the following best explains why water breathers expend more energy ventilating their respiratory surfaces than air breathers?

Accepted Answer

Water is denser and contains less oxygen than air.

Question 16

Which of the following statements about the lymphatic system is correct?

Accepted Answer

It returns excess interstitial fluid to the circulatory system.

Question 17

In mammals, which structure initiates the electrical signal that triggers heart contraction?

Accepted Answer

Sinoatrial (SA) node

Question 18

Which of the following is a correct statement about the relationship between partial pressure and gas exchange?

Accepted Answer

Gases diffuse from regions of higher partial pressure to regions of lower partial pressure.

Question 19

A patient has a mutation that reduces the production of surfactant in the lungs. What is the most likely consequence?

Accepted Answer

Reduced ability of alveoli to remain open, leading to decreased gas exchange.

Question 20

Which of the following best explains why diving mammals can stay underwater for extended periods?

Accepted Answer

They have high blood to body volume ratios and store oxygen in muscle myoglobin.

Circulation and Gas Exchange in Animals

Study Guide - Practice Questions