Classification of Life

• Living things are categorized into groups, called taxa, which share similar properties or characteristics
• Taxonomy - living things categorized based on similar properties or characteristics
• Taxonomy is a branch of biology developed by the Swedish botanist Carolus Linnaeus who lived during the 18th Century
• Taxonomy ranks (from general to specific):

  
  

  DKPCOFGS

  1. domain
  2. kingdom
  3. phylum
  4. class
  5. order
  6. family
  7. genus
  8. species
• domain - broadest category of biological taxonomy
• Three domains exist

  1. Archaea
  2. Bacteria
  3. Eukarya
• prokaryotic - single-celled organisms without a nucleus and membrane
• archaea and bacteria - are both prokaryotic
• Eukarya - organisms that can be unicellular or multicellular with cells that have a nucleus and membrane-bound organelles (eukaryotic)
• Kingdom - before domains were introduced, this was the highest taxonomic rank
• The six (6) Kingdoms:

  PEAFPA

  1. Protista
  2. Eubacteria
  3. Archaebacteria
  4. Fungi
  5. Plantae
  6. Animalia
• Monera - kingdom; has been split into two kingdoms-- Eubacteria and Archaebacteria
• kingdom Eubacteria - belongs to the domain Bacteria
• kindom Archaebacteria - covered by the Archaea domain
• Domain Eukarya is composed of 4 kingdoms

  
  

  PFPA

  1. Protists
  2. Fungi
  3. Plants
  4. Animals
• phyla - plural of phylum
• phylum - the next rank after kingdom; more specific than kingdom, but less specific than class
• There are 35 phyla in the kingdom Animalia, including

  1. Chordata (all organisms with a dorsal nerve cord),
  2. porifera (sponge)
  3. arthropoda (arthropods)
• class - there are 108 different classes in kingdom Animalia, including

  1. Mammalia (mammals),
  2. Aves (birds),
  3. Reptilia (reptiles)
• Class: Kingdom Plantae - divided into 5 major groups:

  1. Thallophyta
  2. Bryophyta
  3. Pteridophyta
  4. Gymnosperms
  5. Angiosperms
• order - more specific than class; between 19-26 orders of Mammalia (mammals), Aves (birds), and Reptilia (reptiles), among many others
• Some orders of Mammalia are:

  1. Primates
  2. Cetaceans (whales, dolphins, and porpoises)
  3. Carnivora (large carnivores/omnivores)
  4. Chiroptera (bats)
• Family - more specific; some families in the order Carnivora, i.e

  1. Canidae (dogs, wolves, foxes)
  2. Felidae (cats)
  3. Mephitidae (skunks)
  4. Ursidae (bears)
• There are 12 total families in the order Carnivora
• genus and species - the levels range from domain to the smallest categories; these two lowest categories are used to give an organism's scientific name using binomial nomenclature
• The species is referred to first by the genus, then the species
• Historically, organisms were classifies according to shared physical characteristics-- visible similarities though unreliable because organisms look the same does not necessarily mean that they are related
• Scientific names are always italicized
• phylogeny - the study of evolutionary relationships allows organisms to be classified according to their common ancestors
• Cladistic analysis - uses cladograms to examine new characteristics, called derived characters, which arise in a lineage
• As new traits appear on the cladogram, only the organisms further down the branch possess these traits
• In the phylogenetic hypothesis, major clades of eukaryotes are grouped into four "supergroups"
• Formerly, all the eukaryotes generally called protists were assigned to a single kingdom, Protista
• 4 Major clades of eukaryotes:

  1. Excavata
  2. "SAR" Clade
  3. Archaeplastida
  4. Unikonta
• Domain Bacteria:

  1. Proteobacteria
  2. Chlamydia
  3. Spirochetes
  4. Gram-Positive
  5. Bacteria
  6. Cyanobacreria
• Domain Archaea:

  1. Korarchaeota
  2. Euryarchaeota
  3. Crenarcheota
  4. Nanoarchaeota