Transcript Document

Evolution of Aging
Katy Nicholson and Coco Shea
Why do organisms age?
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)
Rate of Living Theory
• Populations lack the genetic variation
necessary to respond to selection against aging
• Telomeres are shortened every time a cell
divides (Harley et al. 1990)
Evolutionary Theory of Aging
• Accumulation of deleterious mutations after
reproductive age
• Less selective pressure on 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-Offs
• Reproduce Early or Reproduce Longer?
• Antagonistic Pleiotropy Hypothesis – Mutation
allocates energy to early reproduction or late death
Antagonistic Pleiotropy Hypothesis
• eg. Nematode: Caenorhabditis elgans (Walker et
al. 2000)
Fig. 12.12
Conclusion
• Aging is accumulation of deleterious
mutations
• Allocate energy to reproducing early or to
repairing cells later