Unformatted text preview:

Aging and Other Life History CharactersWhat is life history?Life histories and trade-offsThe life history of a hypothetical female Virginia opossum (Austad 1988, 1993) (fig. 12.2)Life history theory attempts to answer questions such as the following:Aging and life span: what is aging?Survivorship PatternsSlide 8Slide 9Mortality PatternsAging in collared flycatchers: natural population (Gustafsson & Part 1990) (Fig. 12.4 a)Aging in red deer: natural population (Clutton-Brock et al. 1988) (Fig. 12.4 b)Aging in D. melanogaster: laboratory population (Rose 1984) (Fig. 12.4 c)Rate-of-living theory of aging: “live fast, die young”Predictions of the rate-of-living theory of agingThe data suggest that prediction (1) is not upheld (Austad & Fischer 1991) (Fig. 12.5)Experiments show that prediction (2) is not upheld (Luckinbill et al. 1984) (Fig. 12.6)The “telomere” theory of agingA prediction based on the “telomere” theory of agingLife span of cells and whole organisms (Rhome 1981) (Fig. 12.7)The paradox of aging – 1The paradox of aging – 2The evolutionary theory of senescenceA verbal argumentA hypothetical non-senescent life history (constant survivorship, constant reproduction for ages ≥ 3, all individuals die before age 16) (Fig. 12.9 a)A hypothetical non-senescent life history (constant survivorship, constant reproduction for ages ≥ 3, all individuals die before age 14) (Fig. 12.9 b)A hypothetical non-senescent life history (constant survivorship, constant reproduction for ages ≥ 2, all individuals die before age 10) (Fig. 12.9 c)Evolutionary genetic mechanismsAn implication of the evolutionary analysisExperimental evolution of life span in D. melanogasterPowerPoint PresentationMortality rate vs. age in fly populations that have evolved different life spansFemale egg laying vs. age in fly populations that have evolved different life spans - evidence for antagonistic pleiotropy between early age reproduction and life spanLaboratory evolution of life span in D. melanogaster (Luckinbill et al. 1984) (Fig. 12.6)Increase in inbreeding depression with age is consistent with the mutation accumulation mechanism of senescence (Hughes et al. 2002) (Fig. 12.10)Decrease in life span in houseflies when adults live ≥ 4 days is consistent with mutation accumulation (Reed and Bryant 2000) (Fig. 12.11)Antagonistic pleiotropy in the age-1 gene of C. elegans (Walker et al. 2000) (Fig. 12.12)A phenotypic trade-off between early age and later age reproduction in collared flycatchers (Gustafsson & Part 1990) (Fig. 12.13)How many offspring should an individual produce in a given year?A mathematical treatment of Lack’s hypothesis (Fig. 12.16)Most birds lay smaller clutches than predicted by Lack’s hypothesisReasons why birds may not behave according to Lack’s hypothesis1Aging and Other Life History CharactersChapter 122What is life history?•Life histories describe:–Age at maturity (age of 1st reproduction) (early or late)–Reproductive patterns (reproduce once or many times)–Number of offspring (many or few)–Size of offspring (large or small)–Life span (short or long)•Life history is a description of the way in which organisms realize their fitness –“Life history components” are “fitness components”3Life histories and trade-offs•Because the amount of energy than an organism can harvest is finite, life histories inevitably involve trade-offs:–many small vs. few large offspring–rapid reproduction and shorter life span vs. slower reproduction and longer life span•Natural selection should attempt to adjust the allocation of energy between growth, metabolism, repair, and reproduction in such a way as to maximize total lifetime reproduction (= fitness)4The life history of a hypothetical female Virginia opossum (Austad 1988, 1993) (fig. 12.2)5Life history theory attempts to answer questions such as the following:•Why do we age (senesce)?•Why do some species reproduce only once while other reproduce repeatedly?•Why do some species have many small offspring while others have only a few relatively large ones?•Why do some take a long time to reach reproductive maturity, others only a short time?6Aging and life span:what is aging?•Mortality senescenceDecrease in the probability of survival, per unit time, as age increases•Reproductive senescenceDecrease in reproduction with increasing age7Survivorship Patternspx is the probability of surviving from age x to x+101Probability of survivorship, pxAgeSenescent8Survivorship Patternspx is the probability of surviving from age x to x+101Probability of survivorship, pxAgeSenescentNon-senescent9Survivorship Patternspx is the probability of surviving from age x to x+101Probability of survivorship, pxAgeSenescentAnti-senescentNon-senescent10Mortality Patternsqx is the probability of dying in the age interval x to x+1 (= 1 - px)01Probability of mortality, qxAgeSenescent11Aging in collared flycatchers: natural population (Gustafsson & Part 1990) (Fig. 12.4 a)12Aging in red deer: natural population (Clutton-Brock et al. 1988) (Fig. 12.4 b)13Aging in D. melanogaster: laboratory population (Rose 1984) (Fig. 12.4 c)14Rate-of-living theory of aging:“live fast, die young”•Aging is caused by accumulation of irreparable damage to cells and tissues•Damage is caused by errors in replication, transcription and translation; and by toxic metabolic by-products (oxidative damage, etc.)•All organisms have been selected to resist and repair cell and tissue damage to the maximum extent physiologically possible. They lack the genetic variation that would enable them to evolve more effective repair mechanisms than they already have.15Predictions of the rate-of-living theory of aging1) Because cell and tissue damage is caused in part by the by-products of metabolism, the aging rate should be correlated with the metabolic rate, or, equivalently, different species (within broad taxonomic groups) should have similar per gram total lifetime energy expenditures2) Because organisms have been selected to resist and repair damage to the maximum extent possible, species should not be able to evolve longer life spans16The data suggest that prediction (1) is not upheld (Austad & Fischer 1991) (Fig. 12.5) Bats, in particular, live almost 3 times longer than other mammals of similar size and metabolic rateMarsupials have significantly lower metabolic rates than other mammals of the same size, but also have significantly shorter life


View Full Document

NAU BIO 435 - Life History

Download Life History
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Life History and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Life History 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?