Despite their apparent diversity, living things are fundamentally similar inside. The whole of biology is thus a ______ between two themes: astonishing variety in individual particulars and astonishing constancy in fundamental mechanisms. In this chapter, we begin by outlining the universal features common to all life on our planet, along with some of the fundamental properties of their cells. We then discuss how an analysis of DNA genomes allows scientists to position the wide variety of organisms in an evolutionary “tree of life.”
