Evolution And Theories Of Ageing Flashcards
What is ageing?
Progressive loss of function accompanied by decreasing fertility and increasing mortality with advancing in age.
When does fertility in women stop?
45-50 years old
Why do women stop being fertile?
We have a finite number of egg cells, eventually we run out of coccyges.
What is the issue with proximate cause of women becoming infertile?
Why wouldn’t natural selection not produced a longer lasting ovary.
Why would the difficulty of birth lead to women becoming infertile later in life?
May be a fitness advantage to limiting reproduction to ages when it is comparatively safe so women can raise existing offspring to independence
Why is the ‘grandmother hypothesis’?
Woman avoid danger of childbirth but benefit as a grandmother to help care for offspring.
Why do we age?
Diversity in longevity betweenspecies show there maybe genes for ageing
Is ageing programmed?
No
How do we know ageing isn’tprogrammed?
- There is no evidence of ageing genes
- Group selection necessary for ageing doesn’t work
- selection is weak at old age
How does extrinsic mortality drive ageing?
Sources of extrinsic mortality imposes a limit on life span
Genes are selected to ensure survival for expected lifespan and no more
What are evolutionary theories of ageing?
- Mutation accumulation
- Antagonistic pleiotropy
- Disposable soma
Who came up with the mutation accumulation theory?
Peter Medawar in 1952
What is the mutation accumulation theory?
Deleterious mutations are selected against at a young age.
Expressed at a later stage of life because you have already passed on your genes.
Selection is weaker later in life.
Why is selection weaker in life?
Extrinsic mortality
Mutation accumulate
What is Huntington’s disease?
Genetically determined (dominant)
Neurological disorder
Severe symptoms
When does Huntington’s disease occur?
40-50 years (after reproduction)
What disease proves the mutation accumulation theory?
Huntington’s disease because it occurs after reproduction.
What is in antagonistic pleiotropy theory of aging?
Mutations that are beneficial early in life (before reproduction) but are deleterious later in life do not get selected out of a population because selection is less efficient later in life.
How is oestrogen an example of antagonistic pleiotropy?
In early life it provides higher fertility but later in life high levels of oestrogen may lead to breast cancer.
Who came up with the antagonistic pleiotropy theory?
George Williams in 1957
What is the evidence for a genetic contribution to ageing?
Comparing longevities of mono- and di-zygotic twins suggest that 25% of variability in ageing is explained by genes.
What is the issue with the evidence for a genetic contribution to ageing?
Some studies suggest only 10% of the variability in longevity is explained by genes.
What is the disposable soma theory?
Ageing is caused by accumulation of damage.
Deprivation orresources
Maintenance vs. Reproduction
What predictions are made in the disposable soma theory?
Multiple types of damage.
Long-lived species should have better defences and accumulates damage more slowly.
Who came up with the disposable soma theory?
Tom Kirkwood in 1977
What is the accumulation of molecular damage?
Free radical/oxidative
Protein and DNA copy error
Other sources of damage including glucose, toxin and uv
Which theory is correct for ageing?
The 3 theories are not exclusive and provide complementary explanations for why ageing occurs.
What is the main prediction for the disposable suma theory?
The allocation strategy will respond to environmental variation and the rate of ageing may be altered.
How does mortality change with age?
Mortality increases exponentially
Why is the fact woman stop reproducing so strange?
Only mammals to stop being capable of reproducing.
What is the mortality rate fer human births?
10%, birth is way safer in all other mammals.
Why is life expectancy going up?
- Hygiene
- Medical care
- child mortality decreases
- late life mortality extended.
Why can higher life expectancy going up going to be a problem?
Higher life costs
Over population.
Why is there no evidence for ageing genes?
Because there has never been any mutations that have resulted in living forever.
What is evolutionary group selection?
Dying to make space for your kin.
What are mono-zygotes twins?
Exactly the same genome.
What is the most important thing in maintenance in the body?
All systems should carry the same protection level as there is no point repairing DNA if you’ll die due to protein turnover.
How does the allocation of energy change based on age?
Fertility goes down and allocation maintenance increases.
What is the difference between long and short lived species regarding the disposable soma theory?
In long live species damage accumulate slower and the protective mechanisms are much better.
What is oxidative stress?
Damage caused by the by products of metabolism
Mitochondria can produce superoxides.
What are superoxides?
Reactive oxides that can damage macromolecule
How does oxidative stress accumulate over time?
After half life span evidence of damage first shown.
After that damage increases exponentially.
What is Ros?
Relative oxygen species
What is specific about the ros in long lived species?
Release long live but less reactive ros
Should have more effective repair systems.
What is the hayflick limit?
Proliferating cells have a dividing limit after that they become senescent cells.
What are senescent cells?
Damage cells
If you remove them in mice, heath is restored and they live longer.
How does feeding affect ageing?
Can increase life span by reducing feeding, proved by mice.
Why does a reduction in feeding lead to a reduction in ageing.
Work to change internal condition to survive on less so higher survival in them.
