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

http://www.foxnews.com/science/2013/07/23/hey-flipper-dolphins-use-names-to-reunite/

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)BacteriaEukarya

The three domains in the tree of life are Bacteria, Archaea, and EukaryaDomains are above the kingdom level

based on rRNA studies of prokaryotesdomain model more clearly shows prokaryotic diversity

Domain Eukarya includes all eukaryotes

Kingdom PlantaeGreen

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 progressThe 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 Monerasplit 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): Archaeplastida

Division: Rhodophyta (red algae)

The heterokonts or stramenopiles are a major line ofProtists. 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) Class Bacillariophyceae (diatoms)

Division Phaeophyta (brown algae)

Kingdom: ChromalveolataPhylum:Heterokontophyta

Marine Phyla – 27 members of Kingdom Animaliahttp://www.mesa.edu.au/phyla/

http://comenius.susqu.edu/biol/202/taxa.htm

See all new supergroups