We then discuss how an analysis of DNA genomes allows scientists to position the wide variety of organisms in an evolutionary “tree of life.” This approach, which quantifies how closely organisms are related to one another, allows us to identify the three major branches of life on Earth, eukaryotes, bacteria, and archaea—each with unique qualities. We shall see that the familiar world of plants and animals—the focus of scientists for many centuries—makes up only a small slice of the complete diversity of life, the vast majority of which is invisible to the unaided human eye.
–Domains and Kingdoms of life | Video by RicochetScience
