why somes species don’t have their own body heat (like reptiles) and rely on the environment’s temperature when the combustion of sugar in the blood releases energy and heat (and allows us to have our own body temperature)?
In: Biology
There’s more to body heat than producing energy.
You are right, “cold” blooded animals do produce body heat. However, they don’t retain it. There are a few reasons for this.
They don’t regulate their production of body heat. They don’t produce more when they’re cold by doing things like shivering.
They don’t constrict blood vessels to move blood away from their skin to reduce the loss of body heat to the environment.
The reason they don’t is that cold blooded came first. Warm blood animals evolved to be warm blooded instead of being cold blooded.
There are disadvantages to being warm blooded. One is that it requires a lot more food. Warm blooded animals have to eat a lot more food to maintain their body temperature. A lot of cold blooded animals can go very long periods without eating. Warm blooded animals have to be more active so that they can be, well, more active. They’re always closer to starving to death than cold blooded animals. In fact, some smaller warm blooded animals are in constant danger of starving to death if they don’t keep eating all day.
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