ZingPath: Classification

Throughout history, philosophers and scientists (including Aristotle and Linnaeus) have organized organisms into various groupings. One of the original classification systems recognized organisms as either plants or animals. After many years and many discoveries, this system proved to be inadequate, so additional categories were added.

Until recently, there were five recognized kingdoms. However, discoveries of Archaebacteria (prokaryotes that live in extreme conditions) led scientists to update the modern classification system further. This system currently operates with three domains (the largest and broadest category) known as Archaea, Bacteria, and Eukarya.

Domain Archaea contains one kingdom called Archaebacteria, consisting of prokaryotic organisms that live in extreme environments like volcanic hot springs. Domain Bacteria also contains one kingdom called Eubacteria. Domain Eukarya is the only domain containing multiple kingdoms, including Protista, Fungi, Plantae, and Animalia. After kingdoms, the modern classification system further divides organisms into more and more specific categories known as Phylum, Class, Order, Family, Genus, and Species.

In order to classify newly discovered organisms into the appropriate kingdom, scientists look at a variety of cellular characteristics, including the presence or absence of the following: cell walls, centrioles, chloroplasts, and flagella. Scientists also look at what type of respiration the cell conducts as well as how the cell stores carbohydrates.