Evidence used in classification

• Convergent evolution - whereby organisms not closely related independently evolve similar traits due to adaption to similar environment or economical niches

  we can conclude it’s evolution; if two organisms with similar biological molecules are closely related, as they’ve not evolved separately for long
• Cytochrome C

  protein used in process of respiration

  • all living organisms that respire must have cytochrome c; but cytochrome c is not identical in all species
  • amino acids in cytochrome c can be identified +if we compare the sequence of amino acids in samples of cytochrome c from two different species , then we can draw certain conclusions:
  • if the sequences are the same, the two species must be closely related
  • if the sequences are different, the two species are not so closely related
  • the more differences found between the sequences, the less closely related the two species
• DNA

  contains genetic code

  → code is the same for all organisms, universal

  mutations are random

  the more similar the sequences are, the more closely related

  the more differences, you would consider them as less closely related
• The three-domain classification

  1990, Carl Woese suggested a new classification system

  • based his ideas on detailed study of ribosomal RNA gene

  → divided the two kingdom Prokaryote into two groups:

  BACTERIA (og Eubacteria)

  ARCHAEA (og Archaeabacteria)

  division based on fact that the bacteria are fundamentally different from Archaea + Eukaryotae
• Bacteria

  • a different cell membrane structure
  • flagella with a different internal structure
  • different enzyme (RNA polymerase) for DNA synthesis
  • no protein bound to their genetic material
  • different mechanisms for DNA replication + for synthesising RNA
• Archaea’s structure similar to eukaryotes

  • similar enzymes (RNA polymerase) for synthesising RNA
  • similar mechanisms for RNA replication + synthesising RNA
  • production of some protein that bind to their DNA

  Woese’s argument was that these differences between Bacteria + Archaea are fundamental + suggested the two are more different from each other than Archaea + Eukarya
• evolution

  process by which organisms change over time
• Natural Selection

  organisms that are better adapted to their environment have a higher chance of surviving + reproducing, passing on their alleles to their offspring