The Phylogenetic Tree of Life

Evolutionary trees convey a lot of information about a group’s evolutionary history. Biologists are taking advantage of this by using a system of phylogenetic classification. In contrast to the traditional Linnaean system of classification, phylogenetic classification names only clades. For example, a strictly Linnaean system of classification might place the birds and non-Avian dinosaurs into two separate groups. However, the phylogeny of these organisms reveals that the bird lineage actually branches off of the dinosaur lineage, and so, in phylogenetic classification, the birds should be considered as a part of Dinosauria.
Linnaeus’s classification system is considered inadequate today as a means of accurately representing the degree of relationship between two organisms. Up until recently, Neanderthals were classified as Homo sapiens neandertalensis. They are now classified as their own species, Homo neandertalensis. Earlier, giant pandas were also classified with raccoons!
Instead of classifying organisms into prokaryote or eukaryote, it sorts them into three categories by splitting the prokaryotes into two kingdoms similar to the six-kingdom model: Archae bacteria and Eubacteria. All the eukaryotes, which is virtually everything else, are clumped into the Eukarya kingdom. Modern chemical and cellular evidence currently supports the three-kingdom model. It is believed that bacteria were among the first type of life, and the eubacteria separated leaving the archaebacteria and eukarya to continue as one in evolutionary struggles. The fact that modern archaebacteria contain many eukaryotic features indicates their separation occurred after the eubacteria and thereby establishes greater kinship between archaebacteria and eukarya. Archaebacteria are established as a midpoint between eubacteria and eukaraya.

The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon .They have no cel,l nucleus