The organ is the LUNGS.
The lungs excrete carbon dioxide and water vapour through metabolism.
The lungs are used for breathing in humans, through the lungs we take in oxygen which is carried by the blood to all the part of the body and we exhale carbon dioxide which is a waste product generated as a result of the reactions that occur in the body.
The prairie would become overpopulated and there would be no more food for the rabbits and they would eventually die.
