2.1 Taxonomy BACKGROUND INFORMATION Taxonomy is the classification of organisms. Carl Linnaeus developed a standardized system in his manifest, Species Plantarium, in 1753. This document standardized binomial nomenclature as a replacement for descriptive names or polynomials. International acceptance of the system took nearly 200 years. Today, two international organizations, one for zoology and one for botany, determine the rules of nomenclature and record specific names. These rules and names are modified every four to six years and published in English, French, and German. The most recent edition is available online. Scientific names have advantages over common names: speakers of all languages accept them; each name applies to only one species; and each species has only one name. “Formal” scientific names often have a third part, the authority. The authority is not italicized or underlined. The authority is written as an abbreviation of the last name of the person responsible for naming the organism. An example is Quercus alba L., with “L” for Linnaeus. The universally used classification system is hierarchical, based on biological similarity. Phylogeny is the evolutionary history of an organism and is the cornerstone of a branch of biology called systematic taxonomy. A phylogenetic tree is a family tree that shows a hypothesis about the evolutionary relationships thought to exist among groups of organisms. Phylogenetic trees are usually based on a combination of evidence: the fossil record, morphology, embryological patterns of development, chromosomes, and DNA. Misconceptions Enough detail is given in the text to illustrate to the students that taxonomy is an evolving science. The six-kingdom model is not universally accepted; not too long ago the same was true for the fivekingdom system. Divisions and assignments below the kingdom level are subject to debate and change. The classic definition of a “species” is related organisms that share common characteristics and are capable of interbreeding. This works fine for most life forms, but not for all. For example, bacteria can exchange genetic material between species, and many different species and even genera of microorganisms look confusingly similar. Gene mapping is leading to wholesale reclassification of organisms that are now found to be unrelated even though similar in appearance.