Taxonomy is the science of describing, naming, and classifying all living organisms. Taxonomists use genetics alongside behavioral and physical observations to classify all plants, animals, and microorganisms into specific classifications. Taxonomists have so far classified close to 2 million plants, animals, and microorganisms but an estimated 5 to 30 million different species exists on earth. As organisms become more loosely related they progress up an order until the 3 domains of life.  A species is the lowest level in taxonomy, they are classified as a group of organisms that have the capability to breed with one another.  As multiple species become loosely related they are classified as a genus. This trend progresses up a latter from species, genus, family, order, class, phylum, until the 3 domains of life.

The 3 domains of life are Eukaryota, Bacteria, and Archaea. Each domain has specific attributes with Eukaryotes composing life that most people see in their day to day activities. All animals, plants, fungi, and protists are in this domain, they have eukaryotic cells with membranes composed of unbranched fatty acid chains attached to glycerol by ester linkages and contain rRNA that is unique to this domain. Bacteria are prokaryotic cells that are similar to eukaryotes cells but contain no nucleus, lack membrane-bound organelles, and their own unique rRNA. Finally, the domain Archaea is composed of single-celled microorganisms more closely related to eukaryotes over bacteria. Archaean’s inhabit the extreme environments on earth such as deep sea rift vents and extremely alkaline or acid waters.