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 levelsEach 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 Linneaus livedLinnaean system based only on physical similarities.Physical similarities are not always the result of close

relationshipsGenetic similarities more accurately show close relationships

Modern classification is based on genetic similarity

Cladistics is classification based on common ancestry

Phylogeny is the evolutionary history for a group of species.evidence from living species, fossil record, and molecular data shown with branching tree diagrams

Cladistics is a common method to make trees.– classification based on common ancestry– species placed in order that they descended from common

ancestor

Living fossil - found in Ordovician strata 450 mya

Horseshoe Crab

• A cladogram is an evolutionary tree made using cladistics.

– A clade is a group of species that shares a common ancestor.

– Each species in a clade shares some traits with the ancestor.

– Each species in a clade has traits that have changed.

major-clades-of-animals-april-2013-5

KINGDOM Animalia1. Animal Clade 2. Unicellular

Animals3. Multicellular Animals 4. Tissue-Level

Grade5. Organ-Level Grade 6. The Radiate

Animals7. The Bilaterians 8. The

Nephrozoans9. The Deuterostomes 10. The

Protostomes11. The Ecdysozoans 12. The

Spiralians

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 unshuffled 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

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

AnimaliaProtista

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

AnimaliaProtista

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

AnimaliaProtista

Fungi

Plantae

Archea

Bacteria

The three domains in the tree of life are Bacteria, Archaea, and Eukarya.

Domains are above the kingdom level. proposed by Carl Woese based on rRNA studies of

prokaryotesdomain model more clearly shows prokaryotic diversity

– kingdom Protista has been adjustedThe taxonomy of protists is still changing. Newer classifications attempt to use ultrastructure, biochemistry, and genetics.

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 ProtistaDivision Chrysophyta Class Chrysophyceae (golden algae) Class Bacillariophyceae (diatoms)Division Phaeophyta (brown algae)

Kingdom: ChromalveolataPhylum:Heterokontophyta

(unranked):ArchaeplastidaDivision:Rhodophyta

Domain Eukarya includes all eukaryotes

– kingdom PlantaeGreen algaeChlorophyta and charophyta

Marine Phyla – 27 members of Kingdom Animalia

http://www.mesa.edu.au/phyla/Shows all new supergroups

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