Biology: The Unity and Diversity of Life (14th Edition)

Published by Brooks/Cole Publishing Co.
ISBN 10: 1305073959
ISBN 13: 978-1-30507-395-1

Chapter 36 - Self-Quiz - Page 638: 1


a. a closed circulatory system

Work Step by Step

In a closed circulatory system, a muscular heart or hearts pump blood throughout the body within a system of vessels. Exchange of gases, nutrients, and wastes occur through the walls of the capillaries, the tiniest of these vessels. This closed system is found in all vertebrates. However, the structure of the heart varies among vertebrates; fish have two-chambered hearts, amphibians and many reptiles have three-chambered hearts, and mammals and birds have four-chambered hearts. Many non-vertebrate animals have open circulatory systems where hemolymph, which is a yellowish fluid similar to blood, is pumped by the heart into open vessels.
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