Classification
Jan 14, 2016
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