Darwin viewed organisms as would-be perpetual machines that went through a natural filter process. Only the perpetual ones come through. A perpetual machine is fun. Originally it meant a machine that didn't need energy from the outside to run. But that is not what we mean here, rather a machine or system that is able to perpetually run and reproduce itself.
Organisms are exactly such perpetual machines.
In order to run it needs to maintain the continuous flow of energy and matter through it. In other words, it has to eat. Let's play with this idea for a while. The problem is that it makes no effort for getting new gas. It relies on us humans to fill it up.