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Chapter 18 Classification Finding Order in Diversity There are 1.5 million known species that have been identified and classified Why classify? How could a scientist classify living things? Taxonomy NO, it is not stuffing a dead animal It is the logical classification of organisms based on similarities Assigning Scientific Names Name two ways we can name this large rodent that burrows holes in the ground In America we have opossums that are considered ugly and of no use to humans In New Zealand, opossums are highly regarded for their beautiful fur and are often used as a food source Binomial Nomenclature Bi = two Nomial = name Designed by Carolus Linnaeus Each species is given its own two word name How to use the bionomial system The first name is the Genus of the organism It is capitalized and italicized Ex. Ursus The second name is the Species It is written in lower case and also italicized Ex. arctos Finished Product Ursus arctos Linnaeus’s System of Classification Hierarchical Consists of levels Seven levels Kingdom, Phylum, Class, Order, Family, Genus, Species Kingdom Most diverse Largest category Species Most specific Smallest Category Modern Evolutionary Classification Which similarities are most important? In Linnaeus’ time, organisms were grouped according to physical characteristics Using the example of a dolphin, how might this be a problem? Evolutionary Classification Phylogeny – evolutionary relationships Grouping into categories based on evolutionary descent Some organisms may look closely related, but do not share a common ancestor Group these three organisms Although Limpets and Barnacles look very Similar they have important differences. Their larvae are unlike each other Barnacles are segmented, more like a crab Barnacles, like crabs molt (shed outer layer) This places barnacles in the category of crustaceans like crabs and limpets in the category mollusk like clams Classification Using Cladograms Derived Characters Characteristics that appear through evolution and are not present in older ancestors Cladogram Diagram used to show evolutionary relationships between organisms Branches show where new characteristics appear Similarities in DNA and RNA By comparing genes in different species, scientists can determine how closely they are related Probably the most powerful tool for classification Ex. P. 454 Vultures and Storks African vultures and American vultures were once classified in the same family (falcon) Recent DNA comparisons show, American vultures are more closely related to storks Molecular Clocks By comparing the number of mutations in gene sequences of two or more species, scientists can determine how long ago they separated The degree of dissimilarity is an indication of how long ago two species shared a common ancestor There are Three Domains Domains categorize organisms based on how long they have been evolving independently They are larger than kingdoms Archaea- contains kingdom archaebacteria Bacteria – contains kingdom eubacteria Eukarya – contains animals, plants, fungi and protists Kingdoms and Domains There are six Kingdoms Animal Plant Fungi Protist Archaebacteria Eubacteria Dichotomous Key Tool used to identify organisms