Question

Is why is it necessary to separate oxygenated and deoxygenated in mammals?

Answer 1

Mammals are warm blooded. Our body temperature is independent of external factors.
Mixing of oxygenated and deoxygenated blood causes variations in temperature and mammals can't withstand such variations.

So it is necessary to separate them.
Hope this helps you.

Answer 2

Explanation:

It is necessary to separate oxygenated and deoxygenated blood to maintain efficient supply of oxygen into the body. This system is essential in animals that have high energy need. For example, animals like mammals and birds which constantly use this energy to maintain their body temperature.