A mechanism is something like a clock, which is designed to tell time. An organism on the other hand is a natural mechanism like us humans beings, or a simple paramecium.
But the limitations between the two are being removed at a tremendous speed, and quite recently, a medical team was able to construct a full size human heart from stem cells alone. Consider also the news that it has been proven possible to convert fat cells to stem cells, and stem cells to practically every other type of cell, and we will soon be able to grow organs in the laboratory, from the patients own DNA.