Classifying Life

Biological Classification


Taxonomy is the branch of biology concerned with grouping and classifying organisms on the basis of shared characteristics.

Taxonomic Ranks

Do kings play chess on fine glass sets?

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

Three Domain System

Carl Woese proposed the Three domain System in 1990 - separating life into Bacteria, Archaea and Eukarya.

There are many other systems proposed, but this is the currently most accepted one.

Development of Three Domain System

Woese took Ribosomal RNA (which takes messenger RNA into proteins) and compared them amongst the domains of life. He used this to reconstruct the tree of life as: