depth

• Natural selection and other processes led to a staggering diversity of organisms
• Biologists have identified and named about 1.5 million species so far
• They estimate that 2-100 million additional species have yet to be discovered
• Taxonomy


  The discipline of classifying organisms and assigning each organism a universally accepted name
• Binomial nomenclature


  The naming system developed by Carolus Linnaeus where each species is assigned a two-part scientific name in Latin
• Linnaeus's seven levels of classification (from smallest to largest)

  • Species
  • Genus
  • Family
  • Order
  • Class
  • Phylum
  • Kingdom
• Taxon


  A taxonomic category
• Species and genus are the two smallest categories
• Phylogeny


  The study of evolutionary relationships among organisms
• Evolutionary classification


  Grouping organisms based on evolutionary history, not just physical similarities
• The higher the level of the taxon, the further back in time is the common ancestor of all the organisms in the taxon
• Derived characters


  Characteristics that appear in recent parts of a lineage but not in its older members
• Cladogram


  A diagram that shows the evolutionary relationships among a group of organisms
• Similarities in DNA can be used to help determine classification and evolutionary relationships
• Molecular clock


  Uses DNA comparisons to estimate the length of time that two species have been evolving independently
• The three domains


  • Eukarya
  • Bacteria
  • Archaea
• Domain Bacteria


  • Unicellular prokaryotes
  • Thick, rigid cell walls that surround a cell membrane
  • Cell walls contain peptidoglycan
• Domain Archaea


  • Unicellular prokaryotes
  • Many live in extreme environments
  • Cell walls lack peptidoglycan, cell membranes contain unusual lipids
• Domain Eukarya


  • Organisms that have a nucleus
  • Organized into four kingdoms: Protista, Fungi, Plantae, Animalia
• The six kingdoms


  • Eubacteria
  • Archaebacteria
  • Protista
  • Fungi
  • Plantae
  • Animalia
• Kingdom Protista


  • Eukaryotic organisms that cannot be classified as animals, plants, or fungi
  • Display the greatest variety
  • Can be unicellular or multicellular, photosynthetic or heterotrophic, and share characteristics with plants, fungi, or animals
• Kingdom Fungi


  • Heterotrophs
  • Most feed on dead or decaying organic matter by secreting digestive enzymes and absorbing small food molecules
  • Can be multicellular (mushrooms) or unicellular (yeasts)
• Kingdom Plantae


  • Multicellular, photosynthetic autotrophs
  • Nonmotile
  • Have cell walls that contain cellulose
• Kingdom Animalia


  • Multicellular and heterotrophic
  • Cells do not have cell walls
  • Great diversity, many species exist in nearly every part of the planet