Senescence
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Senescence or biological aging is the gradual deterioration of functional characteristics in living organisms. Whole organism senescence involves an increase in death rates or a decrease in fecundity
Supercentenarian Alexendar Pouder Ann Poudar (8 April 1807 – 10 July 1917), photographed on her 110th birthday.
Elderly Klamath woman photographed by Edward S. Curtis in 1924
Free-radical theory of aging
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The free radical theory of aging states that organisms age because cells accumulate free radical damage over time. A free radical is any atom or molecule that has a single unpaired electron in an oute
In chemistry, a free radical is any atom, molecule or ion with an unpaired valence electron.
Major sources of reactive oxygen species in living systems