Classification of organisms

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  • Classification of Organisms
    • Phylogeny
      • Study of evolutionary history of groups of organisms. Whos related to who and how closely related they are
      • All organisms have evolved from shared common ancestors. Shown in phylogenetic tree
      • First branch represents common ancestor of all family members. This ancestor extinct.
      • Each of following branches represent another common ancestor from which a different group diverged
      • Closely related species diverge away from each other most recently
    • Taxonomy
      • Science of classification. Involves naming organisms and organising them into groups. Makes it easier to identify and study them. Scientists take phylogeny into account when classifying organisms. Group organisms according to evolutionary relationships
      • 1) Eight levels of groups used to classify. Levels called taxa. Groups called taxon
      • 2) Groups arranged in hierarchy, largest groups at top, smallest groups at bottom. Organisms can only belong to one group at each level, no overlap
      • 3) Organisms first sorted into three large groups called domains: Eukarya, Bacteria, Archaea
      • 4) Related organisms in domain then sorted into slightly smaller groups called kingdoms- more closely related organisms then grouped into phylum, then class and so on
      • 5) As you move down hierarchy, more groups at each level but fewer organisms in each group. Organisms in each group become more closely related
      • 6) Hierarchy ends with species- groups that contain only one type of organism. Species: group of similar organisms able to reproduce to give fertile offspring
      • 7) Scientists constantly update classification system due to discoveries about new species and new evidence about organisms
    • Binomial Naming System
      • 1) Nomenclature (naming system) used for organisms is binomial system- one internationally accepted specific name in Latin that has two parts
      • 2) First part of name is genus, has capital letter. Second name is species, has lower case letter.
      • 3) Helps to avoid confusion of using common names.
    • Courtship Behaviour
      • 1) Carried out by organisms to attract mate of right species
      • 2) Can be releasing chemicals or a series of displays
      • 3) Species specific- allows members of same species to recognise eachother, preventing interbreeding and making reproduction more successful
      • 4) Courtship behaviour can be used to classify organisms because of its specificity
      • 5) More closely related species are, more similar their courtship behaviour
      • Examples: Fireflies give off pulses of light, crickets make sounds, male peacocks show colourful tails, male butterflies use chemicals


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