Life: The Science of Biology 11th Edition

Published by W. H. Freeman
ISBN 10: 1-31901-016-4
ISBN 13: 978-1-31901-016-4

Chapter 49 - Circulatory Systems - 49.2 - Vertebrate Circulatory systems Evolved from Single to Double Circuits - 49.2 Recap - Learning Outcomes - Page 1049: 2

Answer

The lungfish developed an extra organ that protruded from its gut. It consisted of many thin blood vessels that allows blood to pick up oxygen from the lung. As a result of this adaptation, two anterior gill arches eventually lost their gills, causing a direct linkage from the heart to the dorsal aorta. The twin atria in modern mammals likely developed as a result of these adaptations.

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