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Evolution Exam 3 Notes
Terms in this set (16)
What is the ultimate task of all living organisms under evolution by natural selection?
What is life history?
An individuals pattern of allocation, throughout life, of time and energy to various fundamental activities, such as growth, rapair of cell and tissue damage, and reproduction
How could life history evolve?
Variation in the timing of events and changes in the allocation of energy to different time periods of life
Why are there short winged females?
They use the energy that they would have gone into wings for producing eggs
Aging is a function of metabolic rate
Cell and tissue damage caused in part by the by-products of metabolism, and all organisms will reach the limit of biologically possible repair
Species should not be able to evolve longer life spans
Evidence does not support the hypothesis that species should not be able to evolve longer life spans
Variation in metabolic rate (life time expenditure of energy) is not correlated with life span
Mechanisms that are real?
As a cell divides, a portion of telomere is lost with each cell division (unless telomerase repairs, which happens in germ cells)
The longer a species lives . . .
the longer their telomeres are
If natural selection can lead to longer life spans, why don't organisms evolve to live longer and longer?
Trade-offs with other life history functions can lead to senescence.
Trade-offs between cancer risk and aging
Cells that continue to divide have strong expression of telomerase (e.g. cancer cells)
P53 monitors cells for damage to DNA
-Stop cell division
-Undergo programmed cell death (apoptosis)
-germ line mutations in p53= increased susceptibility to cancer
P53 over activity may attack stem cells that help repair organs and tissues
Mutation Accumulation Hypothesis
When a mutation causes death, it is important
If late acting mutations accumulate at higher rates, then severity of inbreeding depression should increase with age as well.
The mutation accumulation hypothesis suggests that...
-Mutations accumulate more rapidly late in life.
-Natural selection is weaker late in life.
-Alleles that favor early reproduction may be selected even though they promote early death.
The antagonistic Pleiotropy Hypothesis
Selection for alleles with pleiotropic effects that are advantageous early in life and deleterious late in life
-puts energy into reproduction and not repair
-Several genes identified that work this way
Wide spread evidence for trade-off between reproduction early in life and survival later in life
Trade-off between reproductive effort early in life and reproductive success later in life
(a) females that breed earlier have smaller clutches
(b) females given extra eggs have progressively smaller clutches
Evolution of Aging
Aging, like other biological characteristics, evolves but the evolutionary mechanisms underlying aging are different from those underlying most other phenotypes, that is aging does not have a function or purpose, and it is not adaptive.
Why does natural selection declive
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