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