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Classification

Classification. Ms. Moore 1/14 /12. Why classify?. To study the diversity of life, biologists use a classification system to name organisms and group them in a logical manner. Taxonomy : the discipline where scientists classify organisms and assign each organism a universally accepted name.

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Classification

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  1. Classification Ms. Moore 1/14/12

  2. Why classify? • To study the diversity of life, biologists use a classification system to name organisms and group them in a logical manner. • Taxonomy: the discipline where scientists classify organisms and assign each organism a universally accepted name

  3. Early Classification Systems • 350 B.C. Aristole set up 2 kingdoms: • Animal • Plant • 1600s John Ray recognized 2 kingdoms: • Animal • Plant Land Sea Air Classified by: Classified by: Similarities in body structure

  4. Common Names Misleading • John Ray noticed that common names were misleading • So, he chose to name them in Latin because all scientists knew Latin and it is not spoken so translation is not a problem. • Drawback: names were too long! • Example: Carnation = dianthus floribussolitoriissquamiscalycinissubovatisbrevissimiscorolliscrenatis

  5. Linnaeus to the Rescue! • 1700s Carolus Linnaeus developed a two kingdom system • Animal • Plant • Agreed with Ray and used Latin, but gave every organism a two-part scientific name • Genus – Species • Ex. Homo sapiens • This system of classification is known as binomial nomenclature.

  6. Binominal Nomenclature • Genus: group of closely related species • Species: unique to each species within the genus Ursusmaritimus Ailuropodamelanoleuca Ursusarctos

  7. Linnaeus’s System of Classification • Heirarchial system includes 7 levels/taxons: • Species • Genus • Family • Order • Class • Phylum • Kingdom

  8. Genus species • Two smallest categories • Examples: Homo sapien Canis lupus Heterocephalusglaber Susscrofa

  9. Family/Order/Class/Phylum/Kingdom • Family: groups of genera • Ursidae family of bears • Order: broad taxonomic category composed of similar features • Canidae (dogs) and Felidae (cats) • Class: composed of similar orders • Mammalia: warm-blooded, have body hair, produce milk • Phylum: includes many different organisms that nevertheless share important characteristics • Mammals groups with birds, reptiles, etc in the phylum Chordata (backbone) • Kingdom: largest and most inclusive of Linnaeus’s taxonomic categories • Animals and Plants

  10. Similarities • Species were grouped together in larger taxa according to visible similarities and differences. • How would you have classified dolphins? • Evolutionary relationships are important in classification.

  11. Evolutionary Classification • Phylogeny is the study of evolutionary relationships among organisms. • Organisms are now grouped into categories that represent lines of evolutionary descent. • Grouping organisms together based on their evolutionary history is called evolutionary classification. • Species within a genus are more closely related to one another than to species in another genus. This is because all members of a genus share a recent common ancestor.

  12. Using Cladograms • Cladograms are diagrams used to show the relationship among organisms with evolutionary innovations—new characteristics that arise as lineages evolve. • Characteristics that appear in recent parts of a lineage, but not in its older members are called derived characters. • Just like a family tree shows the relationships among different lineages within a family, cladograms represent a type of evolutionary tree.

  13. Showing Relationships

  14. DNA and RNA in Classification • How can DNA and RNA be used in classification? • The genes of many organisms show important similarities at the molecular level. Similarities in DNA can be used to help determine classification and evolutionary relationships. • Humans and yeast related? • Myosin • The more similar the DNA of two species, the more recently they shared a common ancestor. The more two species have diverged from each other, the less similar their DNA will be.

  15. The Tree of Life Evolves • As biologists learn more about he natural world, they realize that Linnaeus's two kingdoms Plantae and Animalia did not represent the full diversity of life.

  16. Three-Domain System • Eukarya (eukaryote = nucleus) • Protista include organisms that cannot be classified as animals, plants, or fungi. • Amoeba, Paramecium, slime molds, giant kelp, algae • Fungi members are heterotrophs who usually feed on dead or decaying matter. • Mushrooms, yeasts • Plantae members are photosynthetic autotrophs and immobile. • Mosses, fens, flowering plants • Animalia includes multicellular and heterotrophic organisms who have no cell wall. • Sponges, worms, insects, fishes, mammals • Bacteria (prokaryote = no nucleus) • Bacteria are unicellular and prokaryotic. Cell walls contain peptidoglycan. • Archaea (prokaryote = no nucleus) • Archaea are also unicellular and prokaryotic. Cell walls do not contain peptidoglycan. • Members of this domain live in some of the most extreme environments you can imagine—volcanic hot springs, brine pools, etc.

  17. Working in lab groups, complete the cladogram worksheets.

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