...or at least a very simplified model that breaks down as you move towards simpler and simpler forms of life. That's because horizontal gene transfer is a thing, and when you go all the way back to prokaryotes, there's so much of it going on that any "tree of life" is a statistical picture that's valid only for a select genetic marker that's used to trace dependencies. Pick a different marker, you'll get an entirely different prokaryotic tree of life.

Life ultimately forms a graph