Chapter 33, Problem 1FIB

Summary Introduction

Introduction:

Respiration is a process used by organism for the exchange of gases with the environment through inhalation and exhalation. The respiratory system consists of the respiratory passage that extends through head, neck, and the lungs. The primary function associated with respiratory system is breathing.

Answer to Problem 1FIB

Correct answer:

Three types of organisms that lack specialized respiratory system are sponges, sea jellies and flatworms. These animals depend entirely on the diffusion process for gas exchange.

Explanation of Solution

Simplest animal’s sponges use ciliated cells to create water current that moves into their central canal which 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.

Conclusion

Sponges, flatworms, and sea jellies lack specialized respiratory structures thus they rely on diffusion for gas exchange.