-Late life decline in an individual's fertility and probablity of
survival. -Reduces and individual's fitness *Should be opposed by
Examples of extended life span:
-Fly pop. can evolve longer life spans. -Bats live 3x as long as
other mammals of same size and similar metabolic rates. -Boosting
Life span can be extended IF:
-Natural selection can lead to longer life spans.
-The physiological and genetic mechanisms for longer life already
Accumulation of: (2 cases)
-Deleterious mutations acting late in life. -Pleiotropic genes with
benefits early in life and costs late in life.
Late-acting Deleterious Genes only occurs if:
-Late-acting deleterious alleles occur at higher frequency than early
acting deleterious alleles then inbreeding depression resulting from
creation of deleterious homozygotes should be more severe late in life. -Confirmed
by Hughes in pattern of fruit flies.
Hughes' fruit fly experiment.
-Allowed flies to only reproduce for 4-5 days. -Caused late
acting mutations to become neutral. -Longevity declined rapidly, in
both large and small populations.
-Lives on mainland SE United States, and Sapelo Island. -Half of
natural possum deaths are caused by predators. -Sapelo Island has NO
mammalian predators. *Sidenote: Second year mainland female
offspring grow more slowly than first year. : Second
year island female offspring grow just as fast as first year.
Three measures that the Virginia Oppossum (island females ) shows
1. Month-to-month probability of survival. 2. Reproductive
performance. 3. Connective tissue physiology.
Cross-linking of Collagen fibers results in.
1. Reduced flexiblity of the tendon. 2. Increases breaking time.
-In humans, compared to other physiological capacity, reproductive
capacity declines earlier and more rapidly in women than men. *Menopause
is a life history adaptation associated with the contribution grandmothers make to feeding
-Suggests that menopause is a life history adaptation associated with the contribution grandmothers make to feeding their grandchildren.
Accept or reject Grandmother hypothesis.
-A definitive test would show that: (1) Daughters of helpful grandmother have more children. (2) Helpful grandmothers achieve higher fitness.
What is the trade-off between number of offspring at a time?
-There is a trade-off between: 1. How many offspring are produced at one time. 2. How much time and energy parents can provide to each offspring.
What does David Lack assume for clutch size in birds? Can you calculate the number of offspring?
-Assumes a trade-off with the probability that an individual offspring will survive decreases with increasing clutch size. -Number of surviving offspring reaches max at intermediate clutch size. (Favored by selection) ** (# surviving offspring) = (clutch size) x (probability of survival)
Lack's hypothesis assumes there is no trade-off between:
1. A parent's reproductive effort in one year. 2. Its survival or reproductive performance in future years. ** Evidence found a (1) trade-off between current and future reproduction (2) trade-off between current reproduction and future survival.
Removing eggs in nest vs. Adding eggs in nest. Effect on daughters?
-When eggs were removed, daughters produced larger clutches. -When eggs were added, daughters produced smaller clutches.
Clutch size affects offspring's (2 answers)
1. Survivorship 2. ***Reproductive Performance***
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