Large animals question

[biology_is_power]

why would large animals who are metabolically active need a complex respiratory and circulatory systems?

[victor]

it's due to balance their massive energy requirement....so, that's why the advanced and more efficient respiratory and circulatory system are built..

[biology_is_power]

oh i see. what role does circulatory system play? is it to replenish the energy? or is that the respitory's function?

thanks by the way

[MrMistery]

well, the circulatory system transports stuff... In this case, glucose and oxygen. The respiratory system gets you that oxigen