Ageing and Death Flashcards
(31 cards)
How can simple behaviour turn into complex behaviours
through the development of sensory and muscular systems leading to more complex responses
Define semelparity
a single reproductive episode followed by death
e.g pacific salmon
Define iteroparity
repeated reproductive episodes throughout life, before death
e.g atlantic salmon
Define extrinsic mortality
Death due to external factors (predation, accidents, environmental extremes, starvation etc.) e.g the way the environment kills you
Define intrinsic mortality
death due to internal factors (tissue deterioration, ineffective physiological maintenance, immuno-compromise, tumours etc.) e.g breaking down, disease creeping out from within
Who was Ming
507 y/o icelandic marine clam
What is the difference in ageing strategies between birds and mammals
Birds will usually live longer (3 times) than a mammal of the same size
Why is it odd that birds live so much longer than mammals
2 - 2.5x higher metabolic rate
15x higher lifetime metabolic expenditure
3oC higher body temperatures
2 - 4x higher blood glucose levels
which are all thought to accelerate ageing and death
Why are younger individuals more likely to to successfully proliferate a gene
Reproduction is additive and multiplicative through time e.g sooner you have kids, the sooner they can have ac child
Younger individuals have lower extrinsic probabilities of mortality e.g the longer you live, the more likely you will be killed
(Younger individuals have lower intrinsic probabilities of mortality)
Why does senescence occue
Because the strength of selection for surviving in age-structure populations declines with age
Define ageing
the progressive loss
of function accompanied by decreasing fertility and increasing mortality with
advancing age.
What is negligible senescence
When an animals don’t lose their ability to reproduce over time and their death rates don’t necessarily increase with age
Animals exhibiting negligible senescence
Galapagos tortoises and Lobsters
What is the Hayflick Limit
The number of times a cell can divide (in humans around 50 divisions)
What is the principle reason why animals have evolved different life spans
Evolution of longevity is predicted to be the
level of extrinsic mortality. If this level is high and life expectancy in the wild is short, the force of selection attenuates fast. Deleterious gene effects accumulate at earlier ages, and there
is little selection for a high level of somatic maintenance (intrinsic mortality) If there is a low level of extrinsic mortality, selection will postpone deleterious gene effects and direct greater
investment in building and maintaining a durable soma.
In terms or reproduction, why isn’t there a drive to increase longevity
When you are young there is a high reproductive success but as you get older your probability of dying due to extrinsic factors increases, thus reducing reproductive fitness soooo a relaxation of selection on
- investment to live longer/keep alive
- invest in later-age reproduction
What are the proximate reasons why we age
Reduced investment causes intrinsic ageing via Free radical damage Mitochondrial damage Glycation DNA damage Telomere shortening
What are the 3 main specific senescence theories
1.Mutation accumulation
2a Antagonistic pleiotropy
2b. Disposable soma
What is the relationship between high extrinsic mortality and reproduction
In environments of high extrinsic mortality e.g high predation, species will invest more into reproducing sooner
Example of lifespan differences within a species
Mainland and island living Virginia opossums were studied. It was found that those living on the island lived significantly longer than those on the mainland as their mortality rate was significantly lower due to less predation
Example of different levels of reproductive investment in the same species
Mainland Virginia opossums were younger when they had their first litter and that litter size is larger than opossums on the island
Why is the maintenance of life inherently challenging (mutation accumulation)
Due to problems from Errors in genetic mechanisms through germ-line/spontaneous deleterious mutations (e.g. cancer) Errors in physiological maintenance (e.g. free radical cell damage: Parkinson’s, Alzheimers) Deleterious alleles (e.g. Huntington disease)
How does extrinsic mortality affect intrinsic mortality (mutation accumulation)
Due to extrinsic mortality there is a progressive weakening of the force of selection which avoids, repairs and evolves against mutations.
When one reaches an age where wild survivorship is really low, the selection which favours upkeeping the body is also really low
Evidence for the mutation accumulation theory
Two populations or drosophila were maintained, one with high extrinsic mortality (killed after a few days) and low extrinsic mortality (killed after a few weeks). This was run for 5 years and then the adult intrinsic mortality was compared. HAM had a sig higher instricsic mortality than LAM
