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2/15/2011 taxonomy notes bI Taxonomy All Materials © Cmassengale Carolus Linnaeus Taxonomy - study of classifying organisms Taxonomists are scientists who study classifying Taxon ( taxa-plural) is a category into which related organisms are placed Reasons to Classify: Shows evolutionary relationships Accurately & uniformly names organisms Prevents misnomers such as starfish & jellyfish that aren't really fish Uses same language (Latin) for all names Prevents duplicated names because all names must be approved by International Naming Congresses (International Zoological Congress) Naming rules are followed called the International Code for Binomial Nomenclature Early Taxonomy: Aristotle was the first taxonomist dividing organisms into land, sea, & air dwellers John Ray was the first to use Latin for naming Linnaeus developed the modern system of naming known as binomial nomenclature, a two-word name (Genus & species) biologyjunction.com/taxonomy_notes_… 1/7 2/15/2011 taxonomy notes bI Scientific names should be italicized in print or underlined when writing Always capitalize the genus name, but write the species in lower case The scientific name for man is Homo sapiens The genus name may be abbreviated, but not the species (H. sapiens) Taxonomic categories: Linnaeus placed organisms into related groups called taxa (taxon-singular) based on their morphology (similar structure & function) The broadest taxon is called the kingdom Linnaeus put all organisms into one of two kingdoms --- Plantae or Animalia The other six taxa from broadest to most specific are --- Phylum, Class, Order, Family, Genus, & species A sentence to help remember these taxa is --- "King Phillip Came Over For Gooseberry Soup." Each taxa is a proper noun &should be capitalized except species Each level or taxon groups together organisms that share more characteristics than the level above biologyjunction.com/taxonomy_notes_… 2/7 2/15/2011 taxonomy notes bI Botanists use the term division instead of phylum for classifying plants Plant species are subdivided into varieties, while bacteria are subdivided into strains Basis for Modern taxonomy: Modern taxonomists classify organisms based on their evolutionary relationships Homologous structures have the same structure, but different functions & show common ancestry The bones in a bat's wing, human's arm, penguin's flipper are the same (homologous), but the function is different Analogous structures have the same function, but different structures & do not show a close relationship (insect wing & bird's wing) Similarity in embryo development shows a close relationship (vertebrate embryos all have tail & gill slits) biologyjunction.com/taxonomy_notes_… 3/7 2/15/2011 taxonomy notes bI Similarity in DNA & amino acid sequences of proteins show related organisms Modern Taxonomic System: Modern taxonomy uses six kingdoms --- Archaebacteria, Eubacteria, Protista, Fungi, Plantae, & Animalia Archaebacteria & Eubacteria are unicellular prokaryotes lacking a nucleus, while Protista, Fungi, Plantae, & Animalia are all eukaryotes with a nucleus & membrane-bound organelles All members of Plantae & Animalia are multicellular organisms Fungi & Animalia are heterotrophs, while Plantae are all autotrophs capable of making their own food Archaebacteria live in harsh environments like very salty lakes; intestines of mammals; and hot, sulfur springs & may be autotrophs or heterotrophs Eubacteria are true bacteria some of which cause disease Protista are mainly unicellular with a few multicellular organisms and may be autotrophic (Euglena) or heterotrophic (Ameba) Fungi include multicellular mushrooms, mold, unicellular yeast, etc. & are absorptive heterotrophs (digest food & then absorb it) biologyjunction.com/taxonomy_notes_… 4/7 2/15/2011 taxonomy notes bI Animalia are ingestive heterotrophs that take in food & then digest it inside their multicellular bodies. Plantae includes all plants & are the only all multicellular, autotrophic kingdom Phylogeny (evolutionary history): Phylogenetic trees are branching diagrams showing how organisms are related Also called family trees Fossil records help establish relationships on a phylogenetic tree Organizes living things based on their evolution (systematics) Common ancestor is shown at the base of the tree Most modern organisms shown at tips of branches Each time a branch divides into a smaller branch, a new species evolves biologyjunction.com/taxonomy_notes_… 5/7 2/15/2011 taxonomy notes bI Cladograms shows how organisms are related based on shared, derived characteristics such as feathers, hair, scales, etc. biologyjunction.com/taxonomy_notes_… 6/7 2/15/2011 taxonomy notes bI Three Domain System: Based on comparing sequences of ribosomal RNA in different organisms to determine ancestry All organisms placed into three broad groups called domains Domain Archaea (kingdom Archaebacteria) contains chemosynthetic bacteria living in harsh environments Domain Bacteria (kingdom Eubacteria) contains all other bacteria including those causing disease Domain Eukarya (kingdoms Protista, Fungi, Plantae, & Animalia) contains all eukaryotic organisms BACK biologyjunction.com/taxonomy_notes_… 7/7