Why must the gas exchange system and the transport system work together in vertebrates?
most of the cells and tissues of vertebrates are not exposed to the air, and therefore oxygen. Without the gas exchange, and transport systems there would be no way to supply these tissues with oxygen. Without oxygen there is no final electron acceptor in the citric acid cycle, the chemical process by which the cells in your body produce most of the energy they need to function and survive. And without the citric acid cycle, which cannot function without oxygen, these cells and tissues would be unable to produce enough energy to stay alive, and your organs and tissues start to die.
