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  1. Classification Chapter 18

  2. What’s Wrong Here?

  3. Classification • To study the diversity of life, biologists use a classification system to name organisms and group them in a logical manner • Taxonomy is the discipline of classifying organisms and assigning each organism a universally accepted name

  4. What is the benefit of having a universal classification system?

  5. Development of a Classification System • Carolus Linnaeus- developed a two word naming system that is still in use today • In Binomial Nomenclature each species is always assigned a two-part scientific name

  6. The first part of the scientific name is the genus. The first letter of this name is always capitalized--- Ursus • The second part of the scientific name is the species, which is never capitalized ---- maritimus

  7. Now You Try • Examples: • ursus maritimus • homo sapiens • canis familiaris

  8. What’s in a Name • When written together, the scientific name includes both the species and genus name of the organism • This should be italicized when typed or underlined when written hand-written

  9. Taxonomic Categories • Linnaeus’s system of classification uses 7 taxonomic categories. • Genus is a group of different species that share common characteristics Kingdom Phylum Class Order Family Genus Species

  10. Taxonomic Characteristics • Families are composed of different groups of genera (genus) that share similar characteristics • Families are grouped into orders. • Orders are grouped into classes. • Classes are grouped into phyla (Phylum) • Phyla (phylum) are grouped into a large category called a kingdom

  11. Modern Evolutionary Classification • Linnaeus compared structure and anatomy • Biologists now group organisms into categories that represent lines of evolutionary descent, not just physical similarities • Derived Characteristics are those that “show up” in newer parts of a lineage but are not in its older members

  12. Modern Evolutionary Classification • Cladograms are diagrams that show evolutionary relationships between groups of organisms

  13. Modern Evolutionary Classification • The genes of many organisms show important similarities at the molecular level. These similarities can be used as criteria to help determine classification • All organisms use RNA and DNA to pass on information. All organisms use ATP as an energy-carrying molecule. Similarities in other important chemicals give us another way to compare them

  14. Modern Evolutionary Classification • Molecular clocks use DNA comparisons to estimate the length of time that two species have been evolving independently. • This relies on the rate that neutral mutations accumulate in the DNA of different species

  15. Kingdoms and Domains • Using new tools available today, scientists have expanded upon Linnaeus’s system of classification. • The 6 kingdom system of classification includes the kingdoms Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia

  16. Kingdoms and Domains • Today, most scientists are now recognizing molecular evidence that requires the addition of a category even larger than kingdom: the domain • Domains: • Archaea • Bacteria • Eukarya