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