• Created on: 29-05-13 00:09


  • Biological classification is the process of sorting living things into groups. Natural classification does this by grouping things on how closely related they are. reflects evolutionary relationships.
  • Taxonomy is the study of the principles of classification.
  • Phylogeny is the study of the evolutionary relationships between organisms. All have evolved from a common ancestor. More recent relative = more closely related
  • Monophyletic: belong to the same phylogenetic groups
  • Taxonomic hierarchy: Domain, Kingdom, Phylus, Class, Order, Family, Genus, Species
  • Autotrophic Nutrition: organism makes its own food from simple inorganic molecules
  • Heterotrophic Nutrition: gains nutrients from complex organic molecules 
  • Prokaryotae: e.g. bacteria: prokaryotic, unicellular, no nucleus, less than 5 micrometres, naked DNA chromosomes, no membrane-bound organelles, smaller ribosomes
  • Protoctista: e.g. algae: eukaryotic, mostly single-celled, wide variety of forms, plant and animal features, mostly free-living, autotrophic and heterotrophic nutrition
  • Fungi: eukaryotic, mycelium with hyphae, cell walls made of chitin, multinucleate
  • Plantae: eukaryotic, multicellular, cellulose cell wall, autotrophic nutrition
  • Animalia: eukaryotic, multicellular, heterotrophic nutrition, fertilised eggs, usually mobile
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Classification 2

  • Binomial Naming System: two names to identify each species: genus and species.
  • Dichotomous key: series of qus with two alternative answers to help identify specimen
  • Early classification systems only used observable features:
    • Molecular evidence - similarities in proteins and DNA. More closely related organisms will have more similar molecules. Sequence of DNA bases, sequence of amino acids in proteins from different organisms. More similar = more related
    • Embryological evidence - similarities in early stages of organism's development
    • Anatomical evidence - similarities in structure and function of different body parts
    • Behavioural evidence - similarities in behaviour and social organisation of organisms
  • Three domains: Cells that contain a nucleus are placed in the domain Eukarya. Organisms that were in Prokaryotae are separated into to new kingdoms: Archaea and Bacteria.
    • New evidence, mainly molecular, reclassified as two domains showed large differences between Archaea and Bacteria.
    • Molecular = enzyme RNA polymerase is different in Archaea and Bacteria. 
    • Archaea have similar histones to Eukarya
    • Cell membrane evidence - bonds in B and A different. Composition of flagella different
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