Ch 18- Classification Why do biologists organize living organisms into groups that have biological meaning? Study the diversity of life Use classification system to name organisms and group them in logical manner Taxonomy- discipline of classifying organisms and assigning each organism a universally accepted name
Scientific Names Why don’t scientists use common names? Use Latin and Greek Bionomial nomenclature- two word naming system Each species given two-part scientific name Carolus Linnaeus First word is capitalized, second word is lowercased, written in italics Ursus arctos- grizzly bear Ursus- genus to which organism belongs Genus- group of closely related species artos- unique to each species within the genus
Linnaeus’s System of Classification Linnaeus’s hierarchical system of classification uses seven taxonomic categories Species Genus Family Order Class Phylum Kingdom Taxon- taxonomic category Family- genera that share many characteristics Ursidae Order- broad taxonomic category composed of similar families Carnivora Class- composed of similar orders Mammalia Phylum- several classes that share important characteristics Chordata Kingdom- largest and most inclusive categories Animalia
Sec 2- Modern Evolutionary Classification Phylogeny- evolutionary relationships among organisms How are evolutionary relationships important in classification? Organisms are grouped into categories that represent lines of evolutionary descent, or phylogeny- not just physical similarities Evolutionary classification- grouping organisms together based on their evolutionary history
Classification Using Cladograms Cladistic analysis identifies new characteristics that arise as lineages evolve over time Derived characters- characteristics that appear in recent parts of a lineage but not in its older members Evolutionary innovation, or new characteristics Cladogram- diagram that shows evolutionary relationships among group of organisms Help understand how one lineage branched from another Use derived characters
Similarities in DNA and RNA All organisms use DNA and RNA to pass on information How can DNA and RNA help scientists determine evolutionary relationships? Genes of many organisms show important similarities at molecular level Can be used to determine classification and evolutionary relationships Similar genes Human muscles and yeast DNA evidence More similar DNA sequence of two species, the more recently they shared a common ancestor American vulture, African vulture, stork
Molecular Clocks Uses DNA comparisons to estimate the length of time that two species have been evolving independently Relies on mutations Comparison between DNA sequences can reveal how dissimilar the genes are- indicates how long ago two species shared a common ancestor
Sec 3- Kingdoms and Domains How many kingdoms of life are there? What are the 6 kingdoms? Eubacteria Archaebacteria Protista Fungi Plantae Animalia Domain- taxonomic category larger than kingdom Eukarya- composed of protists, fungi, plants, animals Bacteria- Eubacteria Archaea- Archaebacteria
Domain Bacteria and Archaea Bacteria- unicellular and prokaryotic Thick, rigid cell walls Ecologically diverse- free living to deadly parasites Some photosynthetic, some not Some depend on oxygen, some not Archaea- unicellular and prokaryotic Most extreme environments Many survive only in absence of oxygen Cell walls lack peptidoglycan Unusual lipids in cell membranes, not found in any other organism
Domain Eukarya All have nucleus Protista, Fungi, Plantae, Animalia Protista- display greatest variety Unicellular and multicellular Photosynthetic and heterotrophic Fungi- heterotrophs Feed on dead or decaying organic matter Unicellular or multicellular Plantae- multicellular organisms that are photosynthetic autotrophs Animalia- multicellular and heterotrophic Incredible diversity