Bio 113 Portfolio
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  • Prion
    • Life Cycles
    • Evolutionary History
    • Kuru
    • Sources
  • Virus
    • Life Cycles
    • Evolutionary History
    • Rabies
    • Sources
  • Bacteria
    • Life Cycles
    • Evolutionary History
    • Pseudomonas syringae
    • Borrelia burgdorferi
    • Sources
  • Archaea
    • Life Cycles
    • Evolutionary History
    • Sulpholobus acidocaldarius
    • Sources
  • Protista
    • Life Cycles
    • Evolutionary History
    • Giardia lamblia
    • Phytophthora infestans
    • Hexacontium enthacanthum
    • Corallina officinalis
    • Discostelium discoideum
    • Sources
  • Plantae
    • Life Cycles
    • Evolutionary History
    • Dicranum polysetum
    • Adiantum aleuticum
    • Ginkgo biloba
    • Pyrus communis
    • Magnolia virginiana
    • Sources
  • Fungi
    • Life Cycles
    • Evolutionary History
    • Lentinula edodes
    • Neurospora crassa
    • Gigaspora gigantea
    • Rhizopus stolonifer
    • Batrachochytrium dendrobatidis
    • Sources
  • Animalia
    • Life Cycles
    • Evolutionary History
    • Euplectella aspergillum
    • Lingula anatina
    • Priapulus caudatus
    • Mellita quinquiesperforata
    • Tachyglossus aculeatus
    • Sources

Evolutionary History

pic (6)

  • Viruses have existed since living cells first evolved (2)
  • They do not form fossils so molecular techniques have been used to compare the DNA or RNA of viruses to investigate their origin (3)
  • There are 3 main hypotheses that explain the origins of viruses (4)
Regressive
  • Viruses may have once been parasitic cells of other cells
  • Over time they lost the genes not required by their parasitism
  • aka. degeneracy or reduction hypothesis
Progressive
  • Viruses may have evolved from bits of DNA or RNA that "escaped" from the genes of larger organisms
  • Escaped DNA may have come from plasmids or transposons
Virus-first
  • Viruses may have evolved from complex molecules of protein and nucleic acid at the same time the first cells appeared on earth
  • They would have therefore been dependent on cellular life for billions of years
  • Viruses are currently recognized as ancient and therefore have origins that predate the split of life into 3 domains (5)
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