Even when a person or organism dies, so long as it has reproduced or replicated itself its life goes on in the offspring. So the life is still not dead even when the individual ceases to be.
I think the stumbling block for you is that you're thinking on to grand a scale. A human is made up of an organized collection of cells, that form organs, that in turn form the individual person. Each cell of our body is alive in it's own right. You're confusing the life of a complex collection of cells (complex organisms) with the life in a single cell.
"Few are those who see with their own eyes and feel with their own hearts." -Albert Einstein
"I would rather have a mind opened by wonder than one closed by belief."
~ Gerry Spence