evolution of aging katy nicholson and coco shea. why do organisms age?
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Evolution of AgingEvolution of Aging
Katy Nicholson and Coco Shea
Why do organisms age?
• Decline in individual’s fertility and probability of survival
• Lose ability to completely repair mutations in cells and tissue (lack of energy)
• Decline in individual’s fertility and probability of survival
Definition of Aging (Senescence)Definition of Aging (Senescence)
• Decline in individual’s fertility and probability of survival
• Lose ability to completely repair mutations in cells and tissue (lack of energy)
• Decline in individual’s fertility and probability of survival
• Populations lack the genetic variation necessary to respond to selection against aging
• Populations lack the genetic variation necessary to respond to selection against aging• Telomeres are shortened every time a cell divides (Harley et al. 1990)
Rate of Living TheoryRate of Living Theory
• Telomeres are shortened every time a cell divides (Harley et al. 1990)
• Populations lack the genetic variation necessary to respond to selection against aging
• Less selective pressure on deleterious mutations after reproductive age
• Accumulation of deleterious mutations after reproductive age
• Neutral alleles can drift to fixation
Evolutionary Theory of AgingEvolutionary Theory of Aging
• Accumulation of deleterious mutations after reproductive age
• Less selective pressure on deleterious mutations after reproductive age
• Accumulation of deleterious mutations after reproductive age
• Less selective pressure on deleterious mutations after reproductive age
• Accumulation of deleterious mutations after reproductive age
• Neutral alleles can drift to fixation
Evolution of Shorter Life Span:Accumulation of Deleterious Mutations
Fig. 12.11 Houseflies - Reed and Bryant (2000)
Energy Trade-OffsEnergy Trade-Offs
• Antagonistic Pleiotropy Hypothesis – Mutation allocates energy to early reproduction or late death
• Reproduce Early or Reproduce Longer?• Reproduce Early or Reproduce Longer?• Antagonistic Pleiotropy Hypothesis – Mutation allocates energy to early reproduction or late death
• Reproduce Early or Reproduce Longer?
• eg. Nematode: Caenorhabditis elgans (Walker et al. 2000)• eg. Nematode: Caenorhabditis elgans (Walker et al. 2000)
Fig. 12.12
Antagonistic Pleiotropy HypothesisAntagonistic Pleiotropy Hypothesis
ConclusionConclusion
• Aging is accumulation of deleterious mutations• Allocate energy to reproducing early or to repairing cells later
• Aging is accumulation of deleterious mutations• Allocate energy to reproducing early or to repairing cells later
• Aging is accumulation of deleterious mutations
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