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Article: Circulatory System
- Article from:
- Animal Sciences
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CopyrightCOPYRIGHT 2002 The Gale Group Inc. This material is published under license from the publisher through the Gale Group, Farmington Hills, Michigan. All inquiries regarding rights should be directed to the Gale Group. (Hide copyright information)
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Circulatory System
Every living organism on Earth, from amoebas to redwoods to whales, has a circulatory system
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a means of gathering and transporting nutrients and collecting and removing waste products.
Plants have an elegant system of strawlike tubes called phloem and xylem, which stretch from the roots to the topmost leaves. Stomata, tiny evaporative holes in the leaves, create suction that steadily draws water up the xylem from the roots, allowing plants hundreds of feet tall to circulate nutrients without a pump.
All cells of the simplest animals, such as single-celled amoebas and multicellular flatworms, are close to the surface. In these cells, nutrients wash through the ...