The Tree of Life is a diagrammatic representation of all life on Earth. It can be split into three branches1: the Bacteria and the Archaea (single-celled organisms) and the Eukarya (multi-cellular organisms).
You see that tiny box labelled “Fungi, Animalia, Plantae”? That tiny box contains all the fungi, animals and plants in the world! Every living thing you’ve ever seen with the naked eye fits in that box! Human beings, other animals and plants make up just a tiny fraction of all life – by far the dominant lifeform on Earth is the humble bacteria.
Woese et al (1990) Towards a natural system or organisms: Proposal for the domains Archaeae, Bacteria, and Eucarya, Proceedings of the National Academy of Sciences, 87, pp. 4576-4579. Download