Has the explosion of phylogenetic research confirmed or overturned our ideas on relationships?
This research has provided overwhelming support for many long-recognized groups, among them insects, mammals and birds, as well as seed plants and flowering plants. It has also confirmed earlier suspicions that some groups do not form a single branch of the Tree of Life. Brown algae, for example, are only very distantly related to the red algae, and crocodiles and dinosaurs are more closely related to birds than they are to lizards or turtles. Phylogenetic studies are also uncovering totally unexpected relationships. This is especially true for microorganisms, where little visible structural evidence is available. Here, DNA sequences are providing data that are fundamentally changing our understanding of relationships. Only over the last few decades have we realized that there are three major branches of the Tree of Life — the Bacteria, the Archaea and the Eukaryotes. The Archaea, single-celled organisms that often live in extreme environments, had been put together with the Bacteria,
