What is taxonomy? Naming and classification of organisms Traditionally based on system developed by Carolus Linnaeus
Two Components to Linnaean System Idea of binomial nomenclature – naming organisms Idea of hierarchy – classifying organisms into groups
Binomial Nomenclature Idea is that each species is assigned a unique name Name has two parts: a genus name and a specific epithet Together, the two words make up the scientific name of the species
Binomial Nomenclature Allows clear communication between different researchers Prevents confusion that can occur from use of common names
Example Scientific Name: Yucca filamentosa Common Names: Bear grass, Adam’s needle, Weak-leaf yucca Picture Credit: Larry Allain @ USDA- NRCS PLANTS Database
Scientific Names: General Guidelines Scientific names are based on Latin. Scientific names are always italicized (when printed) or underlined (when hand-written) Modern scientific names follow international guidelines
Scientific Names: General Guidelines Different species with the same genus name are considered to be more closely related to each other than to other species. Genus name is always capitalized; specific epithet is always lower-case.
Example Panthera leo – lion Panthera onca – jaguar Panthera pardus – leopard Uncia uncia – snow leopard Lions, jaguars and leopards are more closely related to each other than to snow leopards.
Scientific Names: General Guidelines Some scientific names, especially older ones, include the name of the person who discovered or described the species. Example: The Tibetan antelope Pantholops hodgsonii was named for the 19 th century British naturalist who discovered it, Brian Houghton Hodgson. Picture Credit: Rhett A. Butler, mongabay.com
General Naming Guidelines Other scientific names refer to a region, such as Didelphis virginiana (Virginia opossum) Picture Credit: Alden M. Johnson @ California Academy of Sciences
General Naming Guidelines Scientific names often include some feature or trait of the species. The specific epithet for the hairy bush clover, Lespedeza hirta, refers to its “hairy” stem. Picture Credit: Tom Barnes, University of Kentucky
Scientific Names Giant Anteater Myrmecophaga tridactyla “Eater of ants, with three fingers” Picture Credit: Courtesy of Smithsonian National Zoo @ nationalzoo.si.edu
Taxonomic Hierarchy Linnaeus classified organisms into groups, based on shared characteristics. There were different levels of groups. Each level nests within the group above. In his system, the Kingdom was the most inclusive. Successive groups contain fewer and fewer organisms.
Linnaean Hierarchy Kingdom (most general) Phylum Class Order Family Genus Species (unique)
Two Kingdom System Linnaeus classified organisms into two kingdoms: Plantae and Animalia Plants, fungi, photosynthetic protists were all included into Plantae Animals, heterotrophic protists (such as Amoeba) were included into Animalia This system was revised several times.
Five Kingdom System Proposed by Whittaker in 1968 Kingdom Monera – prokaryotes Kingdom Protista – protists (eukaryotes that were not plants or animals or fungi) Kingdom Plantae – plants Kingdom Fungi – fungi Kingdom Animalia – animals
Research by Carl Woese Research done by Carl Woese in the 1980s with rRNA comparisons showed that all prokaryotes are not closely related. Prokaryotes are divided into two groups: true bacteria and archaeans (formerly called archaebacteria)
rRNA Comparisons Based on rRNA, plants, animals and fungi share more similarities with each other than with bacteria or archaeans All eukaryotes share more similarities with each other than with prokaryotes Archaeans share more similarities with eukaryotes than with bacteria
Domains Based on rRNA studies, Woese proposed a Three Domain System Domain Bacteria – “true” bacteria (prokaryotes) Domain Archaea – archaeans (prokaryotes) Domain Eukarya – eukaryotes
Modern Taxonomic Hierarchy Domains are the highest level (most inclusive), above Kingdoms. Kingdom Monera is no longer used. Kingdom Protista is no longer used. Kingdoms Plantae, Fungi and Animalia are still in use.
Modern Taxonomy Modern taxonomy is in a state of flux. As genomes are sequenced for different organisms, evolutionary relationships often become more clear. Taxonomy should reflect those relationships. Expect major changes in taxonomy over the next several years.
Categories and Taxa In this hierarch of classification, the different levels are categories. A named group at a level is called a taxon (plural = taxa). The giant anteater is in Class Mammalia. Class is the category; Mammalia is the taxon. The giant anteater is in Family Myrmecophagidae. Family is the category; Myrmecophagidae is the taxon.
The End Unless otherwise specified, all images in this presentation came from: Campbell, et al. 2008. Biology, 8 th ed. Pearson Benjamin Cummings.