Taxonomy is the study of the classification of living things. Taxonomy is ordered from kingdom, phylum, class, order, family, genus and species. Most organisms are referred to in a standardized format, the binomial nomenclature, which is the genus and species name together, such as homo sapiens.
Modern classification is based on classifying organisms based on evolutionary descent, rather than physical similarities. Other techniques include using derived characteristics to see which organisms are most closely related based on adaptations, nucleic acid comparisons using computer analysis to determine relatedness, and counting the DNA mutations, which is a clock of how old a species is.
The Three Domains
In the modern system, domains are a level above kingdoms. The new three domains divide organisms into prokaryotes and eukaryotes. There are two domains for prokaryotes, the Archaea, which are ancient prokaryotes, and Bacteria, which are the more recent, common prokaryotes. Eukaryotes are organized into the domain Eukarya. The domain Archaea includes the kingdom archaebacteria, which are prokaryotes that live in extreme conditions. The domain Bacteria includes the kingdom eubacteria, which are the more common bacteria. The domain Eukarya includes the kingdoms protista, fungi, plantae, and animalia. Protists are the bridge organism between prokaryotes and eukaryotes. Fungi are decomposers. Plantae are multi-cellular autotrophs, and animals are the multicellular consumers.