8) Classification Of Living Organisms

• Traditionally, living things have been classified into groups based on their structure and characteristics.
• One of the main systems used was developed by Carl Linnaeus.
•  Linnaeus classified living things into:

  kingdom - phylum -> class - order - family - genus - species
• Organisms are named by the binomial system, i.e. they have two parts to their Latin name:

  • The first part is their genus.
  • The second part is their species.
• • New models of classification were proposed because:

  microscopes improved, so scientists learnt more about cells

  • biochemical processes became better understood.
• Due to evidence, e.g. from genetic studies, 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 environments)

  bacteria (true bacteria)

  • eukaryota (including protists, fungi, plants and animals).
• Throughout the history of life on Earth, different organisms have been formed by evolution and some organisms have become extinct.
• Extinction may be caused by:

  • changes to the environment over geological (long periods of) time
  • new predators
  • new diseases
  • new, more successful competitors
  • a single catastrophic event, e.g. massive volcanic eruptions or collisions with asteroids.
• For example, the great auk is now extinct due to over-hunting.