Employability skills are generally divided into three skill sets: (a) basic academic skills, (b) critical thinking skills and (c) personal qualities. The three skill sets are typically broken down into more detailed skill sets.
In the past Archaea were classified as an unusual group of bacteria and named archaebacteria, but since the Archaea have an independent evolutionary history and manifest numerous differences in their biochemistry from other forms of life, they are now classified as a separate domain in the three-domain system.
For the first billion years or so, life on Earth consisted of bacteria and archaea, microscopic organisms that represent two of the three genealogical branches on the Tree of Life (Fig. 15). Both groups are prokaryotes (single-celled organisms without nuclei). Archaea were recognized as a unique domain of life in the 1970s, based on some distinctive chemical and genetic features. The order in which branches radiate from the Tree of Life shows the sequence in which organisms evolved.