Biology (11th Edition)

Published by McGraw-Hill Education
ISBN 10: 1-25918-813-2
ISBN 13: 978-1-25918-813-8

Chapter 48 - The Respiratory System - Review Questions - Synthesize: 3


The organisms listed do not need respiratory organs since they are unicellular, with proportionally very large external surface area. This allows for sufficient gas exchange by simple diffusion to meet their needs.

Work Step by Step

From Fick's Law (p.1004), surface area is a critical feature for this exchange, and, when you consider these things (look at images of flatworms and ciliates in earlier chapters, as examples), you see that they already have lots of surface area across which diffusion can occur.
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.