Question

Why there are separate channels in mammals and birds for oxygenated and deoxygenated blood

Answer 1

there are seperate channels because both bloods have different amount of CO2 and O2 in them so if they will mix they mammals will not be able to perform respiration. Therefore it is necessary to keep them seperated.

Answer 2

because birds can fly and there structure of body is light so that they can fly easily and in mammals the condition is different