Changes

==Long-distance signaling==

==Long-distance signaling==

Chemicals called [[hormones]] are used for long-distance signaling. Hormones vary widely in molecular size and type, and usually travel via the circulatory system to target cells in other parts of the body.

Chemicals called [[hormones]] are used for long-distance signaling. Hormones vary widely in molecular size and type, and usually travel via the circulatory system to target cells in other parts of the body.<ref>Campbell, Neil A., and Jane B. Reece. Biology. San Francisco: Benjamin Cummings, 2002. Print.</ref>

 

==References==

==References==

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