6.4 Classification

• Linnaeus Classification

  • Traditionally living things have been classified into groups depending on their structure and characteristics in a system developed by Carl Linnaeus
  • Living things were classified into:
  • Kingdom, Phylum, Class, Order, Family, Genus, Species
  • Organisms were named by the binomial system of genus and species
• Linnaeus divided all living organisms into two kingdoms:

  • Animal kingdom
  • Plant kingdom
• There have been major advances in biology since the development of the Linnaeus system.

  For example we can now use microscopes to look at internal structures, and analyse an organism's biochemistry (e.g. DNA) and look for similarities with other species.
• Three Domain System

  • Due to evidence available from chemical analysis there is now a 'three-domain system' developed by Carl Woese.
  • In this system organisms are divided into
  • Archaea - primitive bacteria usually living in extreme envrionments
  • Bacteria - true bacteria (e.g. those that live in the human digestive system)
  • Eukaryota - protists, fungi, plants and animals
• Evolutionary Trees

  • Evolutionary trees - method used by scientists to show how they believe organisms are related
  • A new branch shows where speciation has occurred
  • Scientists use current classification data for living organisms and fossil data for extinct organisms