FreeScienceLessons

• Taxonomic classification system


  System used to categorise and name living organisms
• Species


  A group of organisms that can reproduce to produce live fertile offspring
• Binomial naming system


  Naming system that uses the genus and species names
• There are millions of species of living organisms on Earth, but only a tiny proportion have been identified and studied
• Common name


  Name used by non-scientists for an organism
• Use of common names


  Can create problems, as the same species can have different common names in different places, and different species can have the same common name
• Linnaean classification system


  Logical system of classification developed by Carl Linnaeus in the 1700s, which is still used today
• Linnaean classification system


  • Organisms are categorised into taxonomic groups based on common features
  • The system is hierarchical, with the broadest groups at the top and the most specific at the bottom
• Taxonomic groups


  • Domain
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• In the exam, you are not expected to have memorized the classification of any specific organism, but you could be asked to complete the taxonomic groups for a given organism
• Binomial name


  Consists of the genus and species names, with the first letter of the genus capitalized and the rest in lowercase, written in italics or underlined
• Horses and donkeys are separate species because they cannot reproduce to produce fertile offspring
• Prokaryotes


  • Unicellular organisms
  • No nucleus or membrane-bound organelles
  • DNA forms a circular loop and not bound to histone proteins
  • Have small 70S ribosomes
  • Get nutrients by absorption or photosynthesis
• Eukaryotes (Animalia, Plantae, Fungi, Protoctista)


  • DNA held in a membrane-bound nucleus
  • Contain other membrane-bound organelles like mitochondria
• Animalia


  • Multicellular
  • Heterotrophic (ingest/eat other organisms)
  • Glucose stored as glycogen
  • No chloroplasts or cell wall
  • Movement by protein contraction (e.g. muscles), cilia, flagella
• Plantae


  • Multicellular
  • Autotrophic (synthesize own food by photosynthesis)
  • Glucose stored as starch
  • Contain cellulose cell wall and chloroplasts with chlorophyll
  • Limited movement (e.g. Venus flytrap, ginkgo biloba)
• Fungi


  • Unicellular or multicellular
  • Cell wall made of chitin
  • Cannot photosynthesize, lack chlorophyll
  • Absorb nutrients from surroundings, often decaying matter
  • Glucose stored as glycogen
  • Cannot move
• Protoctista


  • Diverse group, don't fit in Animalia, Plantae or Fungi
  • Mostly unicellular, some multicellular
  • Can be heterotrophic or autotrophic
  • Some move by flagella, cilia or amoeboid movement, some have no active movement
• Biologists now look at protein and DNA sequences to classify organisms, in addition to observable features
• Organisms closely related evolutionarily have more similarity in their molecules than distantly related organisms
• Archaea


  Group of extremophile prokaryotes, very different from common bacteria like E. coli in cell membrane structure, cell wall composition, and ribosome structure
• Domains


  Higher taxonomic level than kingdoms, proposed by Carl Woese - the three domains are Bacteria, Archaea, and Eukarya
• The three domain, six kingdom system is now widely used by biologists