The one I will use for this essay is as follows. A living organism is a system that can interact with its environment, exchanging material with the outside, and capable of reproducing itself. Essentially, this is a chemical definition of life. Molecules pass into the organism and are built up to complex molecules distinctive of the organism by a series of chemical reactions. Waste products from this process are passed back out again.
Many people believe that life involves something else apart from chemistry.
This is a piece of speculation that I will ignore since I know nothing about it. The above chemical definition of life actually imposes severe limits on where life can be expected. Life on Earth is made up of complex molecules based on Carbon . This is no accident. Carbon is the only atom capable of forming large complex molecules.