Transcript Evolution of Aging & Late Life

Evolution of Aging & Late Life
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Chapter 18
Evolutionary Definition of Aging
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Sustained age-specific decline
of fitness related characteristics
not due to external
environmental factors
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Not possible to study in vast
majority of species in wild
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Based on Hamilton’s
Mathematical Forces of Natural
Selection.
Population Genetic Hypothesis for
Aging
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Antagonistic Pleiotropy
Evolutionary Trade-off, alleles with
early benefit produce bad side effects
later
Mutation Accumulation
Decline of force of natural selection fails
to remove deleterious mutations
Role of Experimental Evolution in
Aging
If Aging has evolutionary basis1.) Early reproduction will
accelerate aging in
population.
2.) Late reproduction will
slow aging in
population.
Results
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Some experimental results consistent with
Antagonistic Pleiotropy mechanism for
evolution of aging
Other experiments support conclusion that
Mutation Accumulation contributes to aging
in Drosophila
Aging easily identifiable product of evolution
involving many genes
Discovery of Late Life
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Studies of populations revealed
that mortality rates increased
exponentially during mid-life,
plateau later.
Two theories1) Natural selection drops to
zero after reproduction has
ended
2) “Lifelong heterogeneity”
differences in robustness of
individuals
Results
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Late-life plateaus change with changes in
end of reproductive age.
1) Antagonistic Pleiotropy possible
genetic mechanism
No indication lifelong heterogeneity factor in
Late-life plateaus