Phylogeny and the Tree of Life

Alright, we've learned about how unicellular organisms came to be, how they became multicellular, and then from those how evolution by natural selection produced all the species in the world today. But there are so many! Millions and millions in fact. Which is most closely related to which? When did each evolve? What about all the ones that are gone? How do we keep track of this?! Ok calm down, friend. There is a whole discipline called taxonomy that we use to keep track of the phylogeny of every species. To see how it works, we look at the tree of life!