Archaea are microorganisms without a cell nucleus (i.e., prokaryotes), which were originally classified as Archaebacteria. Nowadays, procaryotic organisms are classified into two domains: Archea (Archaebacteria) and Bacteria (Eubacteria). These organisms are characterized by the lack of membrane-bound organelles. On the other hand, the domain Eukaryota consists of organisms that have their nuclei enclosed by a membrane. This domain is divided into four kingdoms: Protista, Plantae, Fungi and Animalia. Binomial nomenclature is a classification system to name species, where the first word of the name indicates the genus of the species and the second part of the name indicates the species within the genus. Finally, reproductive isolation is a term used to indicate physiological, mechanical, behavioral and geographical barriers that prevent interbreeding between two different species.
