Reptiles ectotherms

Endothermic animals can achieve and sustain levels of activity even when temperatures plummet or vary widely. This can be a huge advantage over ectothermy, especially m northern latitudes, at night, or during the winter. In colder climates, an ectothermic predator such as a snake will tend to be more sluggish and less successful than an endothermic predator. There are no reptiles or insects in the polar regions. 

The analysis that follows begins with a consideration of the proximate causes of systemic endothermy, an issue that can be approached by asking, How does an ectothermic vertebrate like a reptile differ from a mammal in terms of mechanisms for supporting endother-... 

The differences in metabolic rate between ectotherms and endotherms thus are due to the preexponential term a, which is approximately four- to fivefold higher in birds and mammals relative to reptiles. On a mass-specific basis (for instance, oxygen consumption per gram wet mass) the mass exponent is near... 

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