Population age structure Life tables provide agespecific mortality and survival Lifetable agespecific account of mortality Cohort group of individuals born in the same time period Age x ID: 1025293
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1. Population Ecology:Human Survivorship
2. Population age structure
3. Life tables provide age-specific mortality and survivalLife-table: age-specific account of mortalityCohort: group of individuals born in the same time periodAge (x)Individuals (nx)0530115928034842155A cohort of 530 coquis from Luquillo, the fate tracked until all indiv diedOf the original 530 individuals born, only 159 survived to age 1.Of the 159 individuals, only 80 survived to age 2. Of the 80, only 48 survived to age 3.
4. SurvivorshipSuvivorship (lx): probability at birth of surviving to given age (x)Expresses the number of individuals surviving to any given age as a proportion of the original cohort size (nx/n0)Age (x)Individuals (nx)Survivorship (lx)05301.011590.32800.1534842155
5. Number of deathsAge (x)Individuals (nx)Survivorship (lx)Deaths (dx)05301.037111590.3792800.15323480.094210.04550.01
6. Mortality rate: deaths/alive# individuals that died during any given time (dx) divided by # alive at beginning of that interval (nx)Age (x)Individuals (nx)Survivorship (lx)Deaths (dx)Mortality rate (qx)05301.03710.7011590.3790.502800.15320.403480.09274210.0416550.015
7. Coqui life tableAge (x)Individuals (nx)Survivorship (lx)Deaths (dx)Mortality rate (qx)05301.03710.7011590.3790.502800.15320.403480.09270.554210.04160.75550.0151.0
8. Theoretical Survivorship Curves
9. Methods for Constructing Survivorship CurvesCohort (dynamic) life table: Follow population life (birth/hatching/germination) to death(2) Static life table:Age at death of individuals in a populationSnapshot: count number of individuals alive in each age class at one point in time
10. Assumptions for Constructing Survivorship CurvesStable age distributionWhat does this mean?Each age class sampled in proportion to its numbers in populationPopulation size is constantWhat does this mean?Mortality/birth rates constant over time
11. Static Method – Pick one of three approachesAges at deathGather data from visit(s) to cemetery or online cemetery recordsSelect two groups you’d like to compare (independent variable)Record birth/death year of 200+ individuals in each group, calculate age at deathSnapshot of age structureGather data from US Census recordsSelect two groups you’d like to compare (independent variable)Record ages at death of 200+ individuals in each groupCompare approach #1 and #2Groups: same group, different data sourcesData collection combination of approaches #1 and #2
12. TimelineLab Today (2/9):Pick your approach and your groupPick your variables/groupsDevelop hypothesis, prediction, and rationale – obtain approval before you leaveHomework between now and next lab:Gather data for your two groupsLab Next Week (2/16):Work in groups to compile and organize data, plot survivorship curvesWork on oral presentationOral PresentationsPeer Review of Presentations