Evolution 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) 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 Telomeres are shortened every time a cell divides (Harley et al. 1990) Rate 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 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 Houseflies - Reed and Bryant (2000)

Energy Trade-Offs Antagonistic Pleiotropy Hypothesis – Mutation allocates energy to early reproduction or late death 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) Fig Antagonistic Pleiotropy Hypothesis

Conclusion 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