Chapter 34, Problem 1MC

Which of the following in not true of respiratory systems?

a. They transport carbon dioxide.

b. They require moist membranes for gas exchange.

c. They minimize the distances gases must diffuse.

d. They all work closely with circulatory systems.

Summary Introduction

Introduction:

Respiratory structures evolved as the complexity of the organisms evolved. They support, protect and retain the moisture of delicate cell membranes by which exchange of gases occurs. These structures include “tracheae in insects” and “lungs in most vertebrates”. The primary function associated with the respiratory system is breathing.

Answer to Problem 1MC

Correct answer:

The statement that is not true regarding respiratory systems is that they all work closely with the circulatory system. Therefore, option (d) is correct.

Option (d) is given as “They all work closely with the circulatory system”.

Explanation of Solution

Justify reason for the correct statement:

Respiratory systems work closely with circulatory system in complex animals whereas simplest animals such as sponges use ciliated cells to create a water current that moves into their central canal. This brings high oxygen for gas exchange, through diffusion. Sea jellies, anemones, and corals contain thin outer skin that allows rapid movement of gases during diffusion.

Flatworms also possess “a gastrovascular cavity” which is used for gas exchange as well as for the process of digestion. In all flatworms, exchange of gases by diffusion occurs through skin surface thus their body shape ensures that all cells are close to the skin. As these animals lack specialized respiratory structures, as well as connection with the circulatory system thus, not all respiratory systems, work closely with the circulatory system.

Hence, option (d) is correct.

Justify reasons for the incorrect statements:

Option (a) is given as “They transport carbon dioxide”.

The respiratory system ensures the exchange of gases such as oxygen and carbon dioxide. Carbon dioxide is transported from cells to lungs and to outside atmosphere by the respiratory system. As this statement is true hence, it is a wrong answer.

Option (b) is given as “They require moist membranes for gas exchange”.

The respiratory system requires moist membranes so that gases can dissolve and diffuse easily. As this statement is true hence, it is a wrong answer.

Option (c) is given as “They minimize the distances gases must diffuse”.

Respiratory systems in animals allow diffusion of gases. The main function of the respiratory system is to reduce the distance traveled by gases to allow easy diffusion. As this statement is true hence, it is a wrong answer.

Hence, options (a), (b), and (c) are incorrect.

Conclusion

Respiratory systems do not work closely with circulatory system in all animals.