Taxonomy

BIOL 1407

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 19th 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

Poison Arrow Frog

Dendrobates azureus

“Blue Tree-Walker”• Picture Credit: Jessie Cohen,

Courtesy of Smithsonian National Zoo @ nationalzoo.si.edu

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

Five Kingdom

Classification

Scheme

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.

Three Domains

Three Domains

Modern Taxonomic Hierarchy

ModernTaxonomic Hierarchy

Example: Giant Anteater Myrmecophaga tridactyla

Domain: EukaryaKingdom: AnimaliaPhylum: ChordataClass: MammaliaOrder: XenarthraFamily:

MyrmecophagidaeGenus: MyrmecophagaSpecies:

Myrmecophaga tridactyla

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, 8th ed. Pearson Benjamin Cummings.