Vestigial Structures: Definition & Examples

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  • 0:00 Definition of…
  • 0:49 Why We Have Vestigial…
  • 1:21 Evidence for Evolution
  • 2:34 More Examples
  • 3:15 Lesson Summary
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Lesson Transcript
Instructor: Julie Zundel

Julie has taught high school Zoology, Biology, Physical Science and Chem Tech. She has a Bachelor of Science in Biology and a Master of Education.

Have you ever wondered why you get goose bumps? Or why you have an appendix? These are vestigial structures and link us to our ancestors from millions of years ago. This lesson will define vestigial structures, explain how it is evidence for evolution and will give examples.

Definition of Vestigial Structures

It's 3 a.m. and those sharp pains you have been experiencing in your stomach have gone from bad to worse. In fact, this is not a typical stomachache. You have a fever, you're vomiting and the stomach pains just won't subside. You have appendicitis, and if you don't hurry to the hospital, that tiny worm-like pouch on your large intestines will burst and kill you.

The appendix has no use in humans, and yet there it is, causing problems for many of us. It - along with a dog's dewclaw, a whale's back legs and even goose bumps - are called vestigial structures, or structures that have no use now but likely had a use in an ancestor.

Why We Have Vestigial Structures

If our appendix has no use, why do we have it? It is believed that our ancestors had a larger, functional appendix that assisted in the digestion of woody material, like tree bark. In fact, many animals, like rabbits, have a functional appendix that aides in digestion.

This idea holds true for other vestigial structures like a whale's hind legs. These legs are reduced in size and do not serve a purpose in the whale, but did serve a purpose in the whale's ancestor.

Evidence for Evolution

Vestigial structures are considered one of the pieces supporting the theory of evolution, which states that organisms change over time. To explain why vestigial structures are important to the theory of evolution, let's use the vestigial structure of the whale to illustrate this concept.

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