Whereas an endotherm expends a tremendous amount of energy just to maintain a constant body temperature, a cold ectotherm can pass months at a time requiring little food or oxygen.    From Wordnik.com.  [Amphibian] Reference

Endotherms differ from an ectotherm because they typically have core temperatures above that of the surrounding environment, whereas the core temperatures of ectotherms depend on external sources of heat – primarily from solar radiation.    From Wordnik.com.  [Endotherm] Reference

Turtle • Endotherm / ectotherm - Migration to northern water • Problems - Stagnant ocean.    From Wordnik.com.  [Recently Uploaded Slideshows] Reference