The ability of an organism to generate and regulate its own body heat internally.
From Greek 'auto-' (self) + 'therme' (heat). Scientific term developed in the 19th century to describe what was previously called 'warm-blooded' animals.
Mammals and birds have autothermy, which is why they can survive in freezing conditions and stay active at night—unlike reptiles that need external heat. This single adaptation was revolutionary for evolution, allowing creatures to colonize every climate on Earth.
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