TAXONOMY

Species of Organisms There are 13 billion known species of organismsThere are 13 billion known species of organisms This is only 5% of all organisms that ever lived!!!!!This is only 5% of all organisms that ever lived!!!!! New organisms are still being found and identifiedNew organisms are still being found and identified

Taxonomy Classification: the arrangement of organisms into orderly groups based on their similaritiesClassification: the arrangement of organisms into orderly groups based on their similarities Taxonomy: the study of classifying organisms Taxonomists: scientists who study classifying Taxon (taxa-plural): category into which related organisms are placed

Reasons to Classify Shows evolutionary relationships Accurately & uniformly names organisms Prevents misnomers (starfish & jellyfish aren’t really fish) Uses same language (Latin) for all names Prevents duplicated names b/c all names must be approved by International Naming Congresses (International Zoological Congress) Naming rules are followed: International Code for Binomial Nomenclature

Early Taxonomy Aristotle: Greek philosopher; first to classify organisms; grouped into plants and animals – then into habitat John Ray: first to use Latin for naming Linnaeus: Swedish botanist; first to classify based on structure; developed modern system of naming known as binomial nomenclature; Systema Naturae (two-word name: Genus and species); “Father of Taxonomy”

Rules for Naming Scientific names should be italicized in print or underlined when written Always capitalize the genus name, and lower case species Scientific name for man is Homo sapiens Genus may be abbreviated, but not the species (H. sapiens)

Taxonomic Categories Linnaeus placed organisms into related groups called taxa based on their morphology (similar structure & function) The broadest taxon is called the domain – then 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 “King Phillip Came Over For Gooseberry Soup”

Taxonomic Categories contd. Each taxon groups together organisms that share more characteristics than the level above Botanists use the term division instead of phylum for classifying plants Plant species are subdivided into varieties, while bacteria are subdivided into strains

Domains Broadest, most inclusive taxonBroadest, most inclusive taxon Three domainsThree domains Archaea and Eubacteria are unicellular prokaryotes (no nucleus or membrane-bound organelles)Archaea and Eubacteria are unicellular prokaryotes (no nucleus or membrane-bound organelles) Eukarya are more complex and have a nucleus and membrane-bound organellesEukarya are more complex and have a nucleus and membrane-bound organelles

Domain Eukarya is Divided into Kingdoms Protista (protozoans, algae…)Protista (protozoans, algae…) Fungi (mushrooms, yeasts …)Fungi (mushrooms, yeasts …) Plantae (multicellular plants)Plantae (multicellular plants) Animalia (multicellular animals)Animalia (multicellular animals)

Taxons Most genera contain a number of similar speciesMost genera contain a number of similar species The genus Homo is an exception (only contains modern humans)The genus Homo is an exception (only contains modern humans) evolutionary relationshipsClassification is based on evolutionary relationships

Species What makes a species? –Common descent: have a common ancestor –Smallest distinct groupings: chromosomal and molecular characteristics –Reproductive community: must exclude members of other species; for sexually reproducing populations, interbreeding is critical for maintaining a reproductive community –Geographic range: distribution through space (cosmopolitan: large area; endemic: restricted distribution) –Evolutionary duration: distribution through time

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

Homologous Stuctures

Basis for Modern Taxonomy contd. 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) Similarity in DNA & amino acid sequences or proteins show related organisms

Embryo Development

Modern Taxonomic System Modern taxonomy uses six kingdoms  Archaebacteria, Eubacteria, Protista, Fungi, Plantae, & Animalia Archaebacteria & Eubacteria are unicellular prokaryotes lacking a nucleus Protista, Fungi, Plantae, & Animalia are all eukaryotes with a nucleus & membrane-bound organelles

Modern Taxonomic System contd. 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 (very salty lakes, intestines of mammals, hot sulphur springs); may be autotrophs or heterotrophs

Modern Taxonomic System contd. Eubacteria: true bacteria; some cause disease Protista: mainly unicellular; may be autotrophic (Euglena) or heterotrophic (Amoeba) Fungi: include multicellular mushrooms, mold, unicellular yeast, etc.; absorptive heterotrophs (digest food & then absorb it)

Modern Taxonomic System contd. Animalia: ingestive heterotrophs; multicellular Plantae: include all plants; all multicellular; all autotrophs

Modern Taxonomic System contd.

Phylogeny (Evolutionary History) Phylogenetic trees: branching diagrams showing how organisms are related; “family tree” Fossil records help establish relationships on a phylogenetic tree Organizes living things based on their evolution 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

Phylogenetic Tree

Cladograms Cladogram: show how organisms are related based on shared, derived characteristics such as feathers, hair, scales, etc.

Cladograms

Dichotomous Keying Used to identify organismsUsed to identify organisms Characteristics given in pairsCharacteristics given in pairs Read both characteristics and either go to another set of characteristics OR identify the organismRead both characteristics and either go to another set of characteristics OR identify the organism

Example of Dichotomous Key 1a Tentacles present – Go to 21a Tentacles present – Go to 2 1b Tentacles absent – Go to 31b Tentacles absent – Go to 3 2a Eight Tentacles – Octopus2a Eight Tentacles – Octopus 2b More than 8 tentacles – 32b More than 8 tentacles – 3 3a Tentacles hang down – go to 43a Tentacles hang down – go to 4 3b Tentacles upright–Sea Anemone3b Tentacles upright–Sea Anemone 4a Balloon-shaped body–Jellyfish4a Balloon-shaped body–Jellyfish 4b Body NOT balloon-shaped - 54b Body NOT balloon-shaped - 5