The Facts

• There are seven levels, or ranks, in the biological classification system. From generic to specific, the levels are kingdom, phylum, class, order, family, genus and species. This is based on the theory that species is the unit with the fewest members, yet the highest commonality between those members, while kingdom has the most members with the fewest similarities. Every known organism on earth, from the blue whale to microscopic bacteria, is classified in this system.
  
  

History

• Depiction of Linneaus at Oxford University Museum of Natural History
  
  In his online text for Biology, Michael J. Farabee, Ph.D, says that Aristotle was possibly the first to begin discussing the organization of the world's species. In 1753, Carolus Linneaus began the basis of biological classification that we use today. The Swedish botanist initially classified all known species, at that time, into two groups. Animalia and Plantae remained the two general headings until 1969 when the idea of five kingdoms was initiated by Robert Whitaker. The kingdom taxon remains one that continues to evolve as science discovers more about classified species as well as discovers new species. Currently, five kingdoms are accepted, Plantae, Animalia, Fungi, Protista and Monera.
  
  

Significance

• The importance of biological classification is the organization it affords such a large and vital portion of our existence. These categories allow scientists the ability to study all of earth's organisms in a systematic way, providing the framework for the evolving knowledge of how these kingdoms work separately and together.
  
  

Types of Classification

• Gulls
  
  Initially, Linneaus determined biological classification by the general characteristics of a species. An example would be feathers on bird species or scales on the reptile species. Later, according to Farabee, Willi Hennig created a classification system called cladistics. The German biologist classified organisms by derived characteristics or shared ancestry. This focus on evolution is different from Linneaus' original idea as he looked for the current, visible characteristics rather than those that assisted in the species evolution.
  
  

Advancements

• A sixth kingdom, according to Farabee, has recently been considered in response to further studies. This kingdom is Archaea; a group of organisms considered to be more evolved than bacteria. Ross E. Koning, Ph.D., states that Carl Woese and George Fox first presented the idea that Archaea deserved their own kingdom. In 2003, Koning says that there was confirmed proof as a result of the genome sequence analysis to warrant a sixth kingdom.