Ectotherms
Reptiles, such as these sunbathing Florida redbelly turtles, are ectotherms: they rely on their environment for body heat.
Source
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"Florida Redbelly Turtle (Pseudemys nelsoni)."
http://commons.wikimedia.org/wiki/File:Florida_Redbelly_Turtle_(Pseudemys_nelsoni).jpg
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