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11-21-11 Life Histories I - Aging

11-21-11 Life Histories I - Aging - ZOL445 Evolution Life...

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ZOL445 Evolution November 21, 2011 Life History Evolution I: Aging Life History Characteristics: Age at first reproduction Mortality rate Rate of reproduction Aging and decline in reproductive success All factors that affect the life table o Shows probability that a person of that age will die before his/her next birthday o Probability of surviving any particular year of age o Remaining life expectancy for people at different ages Age Fraction surviving Age- specific RS Expected RS of individual s x l x m x l x m x 0 1 0 0 1 0.8 0 0 2 0.6 1 0.6 o FITNESS = Σl x m x = Σ(fraction surviving)*(age specific RS) Aging : The decrease in reproductive success and probability of survival with age (decline in Expected RS in life table) Theories of aging: How we age : Mechanisms by which we age and die Why we age : Reasons why evolution acts/does not act on these mechanisms Weismann and Theory of Programmed Cell Death August Weismann (1834-1914) “There is a specific death mechanism that eliminates old and worn-out members of the population to provide living space for the young.” “That life span is connected with the number of somatic cell generations which follow after each other in the course of an individual life, and that this number, like the life span of individual generations of cells, is already determined in the embryonic cell.” Programmed Cell Death and the Hayflick limit Hayflick noticed that fibroblasts stopped growing on their own. He and Morehead mixed old and young fibroblasts and found that when the old fibroblasts stopped, the mixed population was entirely composed of new fibroblasts.
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