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13 Life histories - BIO 370 Kirkpatrick Hall Fall 2004 p 1...

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BIO 370 Kirkpatrick & Hall, Fall 2004 p. 1 13. Life histories ( revised, Oct 9) What is a life history? Definition: The pattern of reproduction and survival over the life of an individual or species There is a huge variation between species in life histories Bristle cone pines live for thousands of years, reproducing a little each year Pacific salmon reproduce just once, then die We know life histories evolve under selection 1) We see differences between species 2) Artificial selection can change lifespan and reproductive rates (example: results from Drosophila ) What is a life table? Two key quantities l ( x ): The probability that a newborn survives to age x m ( x ): The fecundity of an individual that survives to that age A life table gives the values of l ( x ) and m ( x ) for all ages What does natural selection favor? Roughly speaking, selection favors individuals (or genes) that leave the maximum number of surviving offspring Lifetime reproductive success LRS = l (1) m (1) + l (2) m (2) + l (3) m (3) + ...
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