Classification

Linnaeus developed the scientific naming system still used today Taxonomy is the science of naming and classifying organisms A taxon is a group of organisms in a classification system Orcinus orca

Binomial nomenclature is a two-part scientific naming system –uses Latin words –scientific names always written in italics –two parts are the genus name and species descriptor

A genus includes one or more physically similar species –Species in the same genus are thought to be closely related –Genus name is always capitalized A species descriptor is the second part of a scientific name –always lowercase –always follows genus name –never written alone Callinectes sapidus

Scientific names help scientists to communicate –Some species have very similar common names –Some species have many common names Dolphin, porpoise, dolphinfish, mahi mahi

Linnaeus’ classification system has seven levels Each level is included in the level above it Levels get increasingly specific from kingdom to species

The Linnaean classification system has limitations Organisms can be classified based on physical similarities Linnaeus taxonomy doesn’t account for molecular evidence. The technology didn’t exist during 1700’s when Linnaeus lived Linnaean system based only on physical similarities. Physical similarities are not always the result of close relationships Genetic similarities more accurately show close relationships Modern classification is based on genetic similarity

Molecular evidence reveals species’ relatedness Molecular data may confirm classification based on physical similarities Molecular data may lead scientists to propose a new classification DNA is usually given the last word by scientists

Different molecules have different mutation rates. –Mitochondria DNA higher mutation rate – (10x faster than chromosomal DNA –passed down un-shuffled from mother to offspring –better for studying closely related species –Ribosomal RNA –lower mutation rate than most DNA –many conservative regions –better for studying distantly related species Mitochondrial DNA and ribosomal RNA provide two types of molecular clocks

Domain  Domain (also superregnum, superkingdom, empire or regio)  highest taxonomic rank of organisms in the three-domain system  designed by Carl Woese, an American microbiologist and biophysicist  Tree of life Introduced in 1990 has 3 domains: Archaea (a term which Woese created) Bacteria Eukarya

The three domains in the tree of life are Bacteria, Archaea, and Eukarya Domains are above the kingdom level based on rRNA studies of prokaryotes domain model more clearly shows prokaryotic diversity

Domain Eukarya includes all eukaryotes Kingdom Plantae Green algae: Chlorophyta and Charophyta

Classification is always a work in progress The current tree of life has three domains The tree of life shows our most current understanding. New discoveries can lead to changes in classification. Until 1866: only two kingdoms, Animalia and Plantae Animalia Plantae

Classification is always a work in progress The tree of life shows our most current understanding. New discoveries can lead to changes in classification. Until 1866: only two kingdoms, Animalia and Plantae –1866: all single-celled organisms moved to kingdom Protista Animalia Protista Plantae

Classification is always a work in progress The tree of life shows our most current understanding. New discoveries can lead to changes in classification. Until 1866: only two kingdoms, Animalia and Plantae –1938: prokaryotes moved to kingdom Monera –1866: all single-celled organisms moved to kingdom Protista Animalia Protista Plantae Monera

Classification is always a work in progress The tree of life shows our most current understanding. New discoveries can lead to changes in classification. Until 1866: only two kingdoms, Animalia and Plantae –1938: prokaryotes moved to kingdom Monera –1866: all single-celled organisms moved to kingdom Protista Monera –1959: fungi moved to own kingdom Fungi Protista Plantae Animalia

Classification is always a work in progress The tree of life shows our most current understanding. New discoveries can lead to changes in classification. Until 1866: only two kingdoms, Animalia and Plantae –1938: prokaryotes moved to kingdom Monera –1866: all single-celled organisms moved to kingdom Protista –1959: fungi moved to own kingdom –1977: kingdom Monera split into kingdoms Bacteria and Archaea Animalia Protista Fungi Plantae Archea Bacteria

kingdom Protista has been adjusted The taxonomy of protists is still changing Newer classifications attempt to use ultrastructure, biochemistry, and genetics (unranked):ArchaeplastidaArchaeplastida Division:Rhodophyta(red algae)

The heterokonts or stramenopiles are a major line of Protists. Currently containing more than 100,000 species. Most are algae, ranging from the giant kelp to the tiny diatoms. Originally the heterokont algae were treated as two divisions, first within the kingdom Plantae and later the Protista Division Chrysophyta Class Chrysophyceae (golden algae)golden algae) Class Bacillariophyceae (diatoms) Division Phaeophyta (brown algae) Kingdom: ChromalveolataChromalveolata Phylum:Heterokontophyta

Marine Phyla – 27 members of Kingdom Animalia See all new supergroups