3.1

• Classification

  The process of naming and organising organisms into groups based on their characteristics
• Classification hierarchy from largest to smallest

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

  A group of organisms that can interbreed to produce fertile offspring
• This definition of species does not account for species that reproduce asexually
• It can be difficult to assign organisms to one species because:
• Analysing evolutionary relationships genetically

  1. Gel electrophoresis

  2. DNA sequencing

  3. Bioinformatics
• Gel electrophoresis


  Fluorescent DNA fragments are placed at one end of an agar gel plate. An electric current is applied, causing the DNA fragments to move towards the positively charged end. The resulting pattern of bands represents amino acids and is unique to every individual.
• DNA sequencing


  DNA is broken into small fragments, terminated at different lengths by fluorescently marked nucleotides, then duplicated using PCR. The fragments undergo gel electrophoresis, with the smallest fragments travelling furthest, meaning we can read the base sequence of the fragment according to distance travelled.
• Bioinformatics


  The use of technology and software to analyse large amounts of biological data. Can compare entire genomes and look for where mutations have caused divergence in the phylogenetic tree.
• How the scientific community evaluates data

  Papers sent out to other experts for peer review to check for validity. If data and conclusion seem reasonable, results are published in scientific journals. May also be presented at conferences.
• The five-kingdom model of classification has come under scrutiny because it relies heavily on physical observations, and since the introduction of DNA sequencing, new models have been developed
• The three-domain model of classification is more accepted by the scientific community because it takes into account research of a particular ribosomal unit and more accurately represents evolutionary relationships than the five-kingdom model