Classification is the way we communicate about biological diversity naming organisms so we know that we are referring to the same thing the problem with common names ➡ no rules for usage Example: Red Cedar Eastern US Western US Europe Eastern Red Cedar Western Red Cedar Red Cedar Example: Tomato Solanum lycopersicum L. Swedish botanist Species Plantarum (1753) Carol von Linne Binomial nomenclature Each species has a two word Latin name consisting of its genus and species names. These words are always underlined or italicized when written. Example: Tomato Solanum lycopersicum L. Example: Red Cedar Eastern US Western US Europe Eastern Red Cedar Western Red Cedar Red Cedar Swedish botanist Species Plantarum (1753) Carolus Linneaus Hierarchical system - groups nested within groups Kingdom Phylum Class Order Family Genus Species Swedish botanist Species Plantarum (1753) Carolus Linneaus Tomato Kingdom Plantae Phylum (Division) Magnoliophyta Class Magnoliopsida Order Solanales Family Solanaceae Genus Solanum Species Solanum lycopersicum L. Swedish botanist Species Plantarum (1753) Carolus Linneaus Human Kingdom Animalia Phylum (Division) Chordata Class Mammalia Order Primates Family Hominidae Genus Homo Species Homo sapiens Swedish botanist Species Plantarum (1753) Carolus Linneaus Nested hierarchical levels Kingdom (smaller groups nested in larger groups) Phylum Class 1) flexibility to expand our Order classification system without Family starting from scratch Genus 2) ability to organize large Species numbers of things Swedish botanist Species Plantarum (1753) Carolus Linneaus Sexual System Organized plants into 24 classes based on the presence or absence and number of sexual parts as the basis for his classification "Nine men in the same bride's chamber, with one woman" “The affinities of all the beings of the same class have sometimes been represented by a great tree. I believe this simile largely speaks the truth...The green and budding twigs may represent existing species; and those produced during former years may represent the long succession of extinct species...As buds give rise by growth to fresh buds, and these, if vigorous, branch out and overtop on all sides many a feebler branch, so by generations I believe it has been with the great Tree of Life, which fills with its dead and broken branches the crust of the earth, and covers the surface with ever-branching and beautiful ramifications.” (Darwin, 1859) from Bonnet (1745) Ernst Haeckel (1866).