Final answer:
Cell theory describes the fundamental biological principle that all living things are composed of cells and that these cells arise from pre-existing cells, providing the basis for understanding life and its processes.
Step-by-step explanation:
The process or theory that explains how life functions and exists is cell theory. Cell theory is one of the fundamental principles of biology and states that all living things are composed of cells, and that living cells always come from other living cells. This theory is supported by numerous scientific findings and is widely accepted within the scientific community.
Relativistic quantum mechanics is a concept discussed within the fields of physics, specifically attempting to unify quantum mechanics and Einstein's theory of relativity. While this unified theory is significant in understanding the universe because it can theoretically explain objects of all sizes and masses, it does not directly explain the workings of life on a biological level.
In summary, while fields like quantum mechanics and relativity provide insight into the physical laws governing the universe at both the subatomic and cosmic scales, it is cell theory within biology that provides the foundation for understanding the existence and functioning of life.