What makes animals “cold-blooded?”

Question

Physiologically, what is the difference between cold-blooded vs. warm-blooded animals that makes them unable to regulate their own body temperature?

In: 2

Answer 1

As a general rule chemical reactions run faster when you increase the temperature. This gives an edge to animals able to maintain a body temperature higher than the environment as they can be more active.

But it has its downsides as these animals need more food (to generate the heat), insulation (to keep warm), and other adaptations like controlling said temperature (e. g. sweating or panting in hot conditions).

So it’s a matter of “choice of lifestyle” or, more precisely, the evolutionary pathway their ancestors followed. Which means you can’t say that cold-blooded animals are “unable” to regulate their body temperature: it’s not a lacking feature, they just never needed it.

Note two things:

* small animals like microorganisms or minute arthropods could never be warm-blooded as they have an enormous surface/volume ratio and any generated heat gets immediately sucked out to the environment.

* there are cold-blooded animals using a mixed strategy. For example some moths heat up their flight muscles by the equivalent of shivering before taking flight, and tunas’ swimming muscles also get hot when they cruise along. This increases efficiency in said muscles.