During the ratification debate in Virginia, Madison promised that a bill of rights would be added after ratification. His promise reassured the convention and the Constitution was approved in that state by the narrowest margin. New York soon followed, but submitted proposed amendments.
Bacteria reproduce by a process known as binary fission, while eukaryote such as animal cells, reproduce by mitosis. In binary fission one bacterium slowly separates into two bacteria which then also divide and the life cycle continues as this process repeats over and over.
The main function of bacteria, like any organism, is to reproduce, and while mitochondria's main function is to produce energy in the form of ATP it also needs to reproduce. Mitochondria are formed by a process very similar to binary fission, the method by which bacteria divide.