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

Cold blooded animals don’t generate more heat than their normal body requirements. Think of how your lap top gets warm just from being on. Maybe it’ll get even warmer if you make it do something demanding like play a video game. Normal cellular activity on it’s own generates heat. The cold blooded animals don’t spend more calories than needed for their normal cellular activities.

Warm blooded animals do all their normal cellular activity plus even more just to bring the heat up. It’s a lot like running a high end video game in the background on your computer just because you want to heat your room up a bit.

There are advantages and disadvantages to both methods. Warm blooded animals need more calories to raise their heat up, but don’t need to bask in the sun just to get their body going.

Answer 2

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.