Presentation on theme: "Life tables Were first used to estimate insurance risk in human populations Divides the population into age specific classes Estimates the age-specific."— Presentation transcript:
1Life tablesWere first used to estimate insurance risk in human populationsDivides the population into age specific classesEstimates the age-specific mortality risk in each class
2A life table for a town in the East Midlands agepopdeath% death1 death in<12533201271-41113015-9155192776010-14164094410215-19161339179320-242148210214825-29159972272730-34160263545835-39198003458240-44160763941245-49134045922750-541302710812155-59100511367460-64102201765865-6991903202970-7474274451775-7952314141380-852884355885+18403475
3Assembling a life table Cohort or Dynamic life tableAssembled by following the fate of a cohort from birth to death.Static life tableAssembled estimating the age specific death risks from the age structure at a given time
4Dynamic life table Static life table age 1999 2000 2001 2002 survivorship lx10001.0014000.4021000.103200.02Static life tableestimatedage1999survivorship lx10001.0014000.4021000.103200.02
5However a static life table assumes the population is stable which is usually not true estimatedage1999survivorship lx10001.0014000.4021000.103200.02Originalestimatesestimatedage1999original populationsurvivorship lxsurvivorship10001.00140012000.400.33210014000.100.0732016000.020.13But what if the population is decreasing?Decreasing population
7Phlox drummondii (annual phlox) is native to central and eastern Texas Phlox drummondii (annual phlox) is native to central and eastern Texas. It is a winter annual and grows abundantly in sandy fields and on roadside verges. It germinates in response to cool rainy weather.
8qx=lx-lx+1the proportion of individuals that have died over a time period =the mortality rate.
9Mortality analysis time days time days Average mortality rate per day Log scaletime days
11Fecundity analysisNumber of seed produced per planttime days
12Diagrammatic dynamic life table for Phlox drummondii Rectangles=stages in the life-cycleInverted triangles= transition probabilitiesDiamond=seed production
13A more complex diagrammatic life table of the biennial ragwort Senecio jacobea DispersalSeed bank dynamicsgerminationimmigrationestablishmentBiennial lives for 2 years reproducing at the end of the second year
14Survivorship curvesType I = Found where there are ample resources e.g. human population in developed countriesType II = A constant risk of death throughout lifespan e.g. seeds in a buried seedbankType III = High early mortality e.g. many plants reproducing by seed