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Why & How do we age? (How does dietary restrictions affect the…
Why & How do we age?
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Pleiotropy Theory
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genes that benefit the organism early in life will be favored by selection even if they have bad effects at later ages
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Evidence: by restricting reproduction to later ages, the intensity of selection on the later portions of life span was increased
Disposable Soma Theory
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trade off between growth, reproduction & DNA repair maintenance
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Controversy: There are inconsistencies due to observed effects of dietary restriction, which increase lifespan. But according to disposable soma theory, with less caloric intake, there would be less total energy to be distributed towards sam maintenance. This would lead to decreased lifespan.
Extrinsic mortality (constant over age): result of environmental changes/hazards, adaptations such as wings or large brains can reduce it
if the level is high, life expectancy in the wild is short, the force of selection attenuates fast, deleterious gene effects accumulate at earlier ages, there is little selection for high level of somatic maintenance
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What is senescence? Biological aging, deterioration of functional characteristics