Botany CH 17 – Classification of Organisms

Taxonomy

 The science of classifying and naming organisms  Each group is called a taxon (pl. taxa) What is Taxonomy ?

Metadata Taxonomy

Bloom’s Taxonomy

iPhone Taxonomy

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Early Taxonomy ( 384 – 322 BC )  Aristotle, a philosopher of Greek origin, began the organization process  He used only 2 taxa  It was very inefficient as common names varied from place to place

Early Two Taxa System

 Linnaeaus, a Swedish botanist devised a system based upon form and structure  His goal was to join “ similar to similar”  His original system had 7 levels Linnaean System ( circa 1750 ) EMPIREKINGDOMCLASSORDERGENUSSPECIESVARIETY

 This system still had 7 levels – but now slightly different Linnaean – with an early change EMPIREKINGDOMCLASSORDERGENUSSPECIESVARIETY KINGDOMPHYLUMCLASSORDERFAMILYGENUSSPECIES

Levels of Classification

 While older systems were based on observed features  Recent DNA sequencing has uncovered natural relationships  So the system was re-organized into an 8 –level format Taxonomic Reshuffle

greater dissimilarity greater similarity (least alike) (most alike ) D OMAIN K INGDOM P HYLUM C LASS O RDER F AMILY G ENUS S PECIES Modern System

E NGLISH N AME G ROUP L ATIN / G REEK N AME animals KINGDOM Animalia chordates PHYLUM Chordata vertebrates SUB - PHYLUM Vertebrata mammals CLASS Mammalia primates ORDER Primates hominids FAMILY Hominidae human GENUS Homo wise SPECIES sapiens

 So the DNA sequencing ( think Genome Project) data forced the change to a 3-domain system  This system is not based solely on observable features  These domains are:  Domain Bacteria  Domain Archaea  Domain Eukarya The 3 Domain System

 These are prokaryotic organisms  They lack a true nucleus  They have cell walls  They reproduce by binary fission Domain Bacte ria

 These are also prokaryotic organisms  They lack a true nucleus  They have distinctive cell membranes  They reproduce by binary fission Domain Archaea

 These are the eukaryotic organisms  They have membrane bound organelles – including a membrane bound nucleus Domain Eukarya

The 6 Kingdom System BacteriaArchaeaEukarya EubacteriaArchaebacteriaProtistaPlantaeFungiAnimalia

 Eubacteria - means “true bacteria”  Archaebacteria – means “ ancient bacteria” Prokaryotic Kingd oms

 Protista  Neither plants, animals, or fungi  Identified by what they are not  Fungi  Get their nutrition by absorption  Plantae  Most are autotrophic  Animalia  Develop from embryos and have symmetry Eukaryotic Kingd oms

Naming System

 Linnaeus also developed a naming system for the organisms in his classification system  It was called binomial nomenclature  The “binomial” meant that every organism would be identified by its genus and species Linnaeus Revisited

 The genus name begins with an uppercase letter  The species name is always lowercase  Both would be underlined or italicized Rana pipiens ( Northern leopard frog ) Escherichia coli ( Enteric rod bacteria ) Binomial Nomenclature

Systematics

 Systematics is a way to classify organism by their relationship (evolutionary)  Systematics is based on inferences that are founded on homologous structures Systematics

 Homologous structures are organs or bones that appear in completely different organisms  It is these homologous structures that allows scientists to infer that these organisms had a “shared” ancestor Homologous Structures

Examples

 The inferred (evolutionary) history of a single species is known as phylogenetics  The prefix phylo means “tribe” or “race”  The suffix genetics means “origin” Phylogenetics

 Similarities between fossils and living species Phylogenetic Evidence

 Similarities in embryo  development ontogeny recapitulates phylogeny Phylogenetic Evidence

 Similarities in chromosome sequences Phylogenetic Evidence

 Similarities in homologous structures Phylogenetic Evidence

 All phylogenetic trees are hypothetical  They will change with every new discovery The Result Phylogenetic Tree

Cladistics

 Cladistics is a system that uses shared characters and derived characters for its grouping  It was conceived in 1966 by a German biologist  Cladistics infers that organisms that share a derived characters inherited it from a common ancestor Cladistics

 A shared character is a feature that all members of the group have in common Examples: hair in all mammals OR feathers in all birds  A derived character is an advanced trait that evolved within the group being analyzed Example: loss of a tail Cladistics

 A clade is a group of organisms that share a common ancestor  The derived character is used to group those organisms into the clade The Clade

 Amphibians, turtles, lizards, snakes, crocodiles, birds and mammals have or historically had four limbs  Fossils show that snakes did have limbs  Some modern snakes retain rudimentary limbs  Four limbs = a shared derived character and was inherited from a common ancestor for this clade of vertebrates A Vertebrate Clade

Vertebrate clade

Botany CH 17 – Classification of Organisms End