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Senescence, Menopause, Semelparity
Terms in this set (23)
Optimal life history specifies allocation to?
what proximate reasons are there for senescence?
physiological impacts of individual simply being alive
- inevitable wear and tear, despite repair
what evidence is there that 'inevitable wear and tear' isn't the best explanation for senescence
very old Creosote bush 'King clone' - more than 11,000 years old
- suggests it is possible to repair yourself indefinitely
What ultimate explanations are there for senescence
inevitable accumulation of mutations
who suggested the accumulation of late-acting mutations
Peter Medawar, 1952
Force of natural selection declines with ?
If a your individual fails to reproduce, has a big effect on fitness of genotype
If an old individual, likely won't breed again, dies, selection will have much less effect
- thus discrimination between alternatives is less strong
Who made the antagonistic pleiotropy theory?
small positive effect early in life will balance against a big negative effect later in life
who made the disposable soma theory?
With the disposable soma theory (Kirkwood, 1977)
what is the optimum level of investment into repair?
that maximises lifetime reproductive success at an intermediate lifespan
What 3 species is menopause seen in?
what adaptive reason might there be on the depletion of oocytes?
based on costs and benefits of reproduction after 45-50 years
What benefits might there be to menopause?
large brain = long period of dependance
- high risk mother dies in childbirth for offspring later in life
- switch to other activities e.g. care of grandchildren
Cant and Jonhstone, 2008 suggested?
(best adaptive explanation)
conflict in group over breeding
different individuals who could be breeding in a group
,though those not breeding could be helping other individuals
What non-apdative explanation is there to menopause?
side-effect of living longer than we did in our 'evolutionary' environment
- not caught up with the selection we now impose on ourselves
why is it not likely that menopause is just a non-adoptive consequence of living longer ?
modern hunter gatherer still live long enough to see a point at which selection could be happening for menopause
- so prehistoric populations didn't survive long enough to experience menopause
With semelparity what is not selected for?
When would semelparity be favoured?
When current reproductive success is increasing with effort
= increasing returns
Low probability of future reproduction
What can you compare to infer on semelparity?
Life history in lobelias
In Lobelia telekii - Semelparous
what is seen?
Very low probability of future reproduction
Greater reproduction per flowering episode
In Lobelia keniensis - Iteroparous
what is seen?
puts much less effort into each flowering episode
Schneider & Rubin, 1997 did an experiment with?
Stegodyphus - Spider
Schneider and Rubin, 1997
what was found
success of second brood was lower
than success of first brood
- Semelparity better, risk of predation = low chance of second brood
- lower success of second brood
Semelparity give higher fitness returns on average
What do static models predict optimisation for?
something immediately available
- easy to test
This set is often in folders with...
Size & Fat
Cost of reproduction
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