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Readings 15 notes

Biological Sciences
Course Code
Maydianne Andrade

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Readings 15
Pgs. 483-502 (refer to pg485 and 489)
-life history analysis is the branch of evolutionary biology that attempts to make sense of the
diversity in reproductive strategies
-the amount of energy an organism can harvest is finite and biological processes take time
according to the laws of physics and biology
-the benefit of being large is balanced by the cost of being susceptible to predators
-an individual that takes time to growth risks dying without reproducing at all
-whenever there is a trade off between different components of fitness, natural selection
favours the individuals that allocate energy and time with an optimal balance between benefits
and costs
-environmental variation is undoubtedly the source of much of the life history variation seen
among living organisms
-differences among life histories concern differences in allocation of energy
-allocating energy to different areas such as reproduction, metabolism, and repair all have
trade offs
-allocating energy to repair keeps tissues in better condition with the risk of having fewer
-allocating energy away from growth also produces fewer offspring
-aging, or senescenceU]oo](o]v]vv]v]À]µo[(]o]Çv}]o]Ç}(µÀ]Ào
-there are two theories of why aging exists
x Rate of living theory says that populations lack the genetic variation to respond to any
further to selection against aging
x The Evolution Theory says that aging is a trade off between the allocation of energy to
reproduction versus repair
-rate of living theory of senescence holds that aging is caused by the accumulation of
irreparable damage to cells and tissues, caused by errors during various DNA processes
-this theory makes two predictions
x Because of cell/tissue damage due to metabolism, aging rate is correlated with
metabolic rate
x Because organisms have been selected to resist and repair damage to maximum
extent possible, species are not able to evolve longer life spans
-the rate of living theory persists due to the fact that some cellular and genetic mechanisms
have appeared to link the senescence of cells to the senescence of organisms
-telomeres of a cell consist of repetitive DNA sequences that are lost for every cycle of DNA
replication, linking them to senescence and death of the cell
-after much experimentation, there is no simple relationship between telomere length, the
replicative senescence of cells and whole organism aging and death
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