Taxon

**History of Taxon and Taxonomy:**
– Term ‘taxon’ first used in 1926 by Adolf Meyer-Abich for animal groups
– Word ‘taxonomy’ coined a century before from Greek components
– Proposed for plants by Herman Johannes Lam in 1948
– Adopted at the VII International Botanical Congress in 1950

**Definition and Concept of Taxon:**
– Taxon defined as a taxonomic unit, inferred to be phylogenetically related
– Includes populations of organisms with common differentiating characters
– Encompasses all included taxa of lower rank and individual organisms

**Taxonomic Ranks and Hierarchy:**
– Hierarchy of biological classifications has eight major taxonomic ranks
– Phylum traditionally used for animals, division for plants, fungi, etc.
– Prefixes like super-, sub-, and infra- indicate rank importance
– Rank is relative and restricted to a particular systematic schema
– Class rank often phenetic or paraphyletic, challenging traditional nomenclature

**Taxonomic Classification and Nomenclature:**
– Taxon is a group of one or more populations of an organism seen by taxonomists
– Taxon is usually given a particular name and ranking
– Taxon is governed by nomenclature codes specifying the correct scientific name
– Taxonomists often differ on criteria for inclusion in a taxon
– Modern systematists use cladistic methods to ensure taxa reflect evolutionary relationships

**Taxonomic Tools and Methods:**
– Taxonomic keys are tools used to identify organisms based on their characteristics
– Keys consist of a series of choices that lead the user to the correct identification
– Keys can be based on physical traits, ecological preferences, or genetic markers
– Taxonomic keys are essential for accurately identifying unknown species
– Modern classification methods use genetic data in addition to morphological traits