Campbell Biology (10th Edition)

Published by Pearson
ISBN 10: 0321775651
ISBN 13: 978-0-32177-565-8

Chapter 23 - Test Your Understanding - Level 3 - Synthesis/Evaluation: 6

Answer

Examples would be vestigial structures no longer needed but still present in some reduced from, structures selected against but for which the mutations for their complete elimination have simply not yet occurred. These include the appendix, an unneeded pocket off the human intestine, and the hind legs of whales, which are descended from walking land mammals.

Work Step by Step

There are many examples-- one way to find them is to skim the book looking for discussion of vestigial structures, ones left behind by evolution but not completely eliminated since the needed mutations to cause that have not yet happened. Consider how we have compared the current traits of organisms with common ancestors in previous chapters.
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