Demography population s size 2 Survivorship and fecundity 1 Demography study of vital statistics e g birth rate death rate that affect a Survivorship the age based pattern of survival Fecundity age based reproductive output ecological concept Fertility capacity to breed physiological concept a Life table age based tabular summary of mortality in a population b Fecundity schedule age based tabular summary of reproductive output of a population 3 Life tables b Vital statistics a Cohort life table follow a single cohort from birth to death Cohort group born in the same short time interval lx survivorship statistic proportional to the percent of individuals that make it to a given age proportion of original cohort surviving to the start of stage or interval x o lx Nx N0 dx mortality statistic overall extent of mortality in stage age interval proportional to percent of original cohort proportion of the original cohort dying during stage or interval x o dx Nx Nx 1 Nx qx mortality statistic age specific intensity probability of mortality proportion of the individuals entering stage x that die in stage or age interval x o qx Nx Nx 1 Nx Nx number of individuals alive at start of stage or age interval x x lx mx X months 0 1 2 3 4 5 6 Nx 200 140 100 20 10 5 0 lx 1 000 0 700 0 500 0 100 0 050 0 025 0 dx 0 300 0 200 0 400 0 050 0 025 0 025 qx 0 300 0 286 0 800 0 500 0 500 1 000 Fx 0 0 10 200 100 10 0 Mx 0 0 0 1 10 0 10 0 2 0 0 lx mx 0 0 0 05 1 00 0 50 0 05 0 1 6 0 0 0 10 3 00 2 00 0 25 0 5 35 months c Survivorship curves Survivorship as a function of time o Reveals age based pattern of survival and mortality o Many life tables and hence survivorship curves are static as opposed to cohort based Importance of plotting abundance on a logarithmic scale o Qx is constant every interval is equally likely to survive EX let qx 0 5 Can t see pattern later in life o Plot lx logarithmically slope is proportional to the age based probability of mortality EX let qx 0 9 constant Can see pattern of survivorship Type I II and III survivorship curves o I as age increases the age specific mortality increases EX humans whales o II constant age specific mortality rarest EX hydra o III as age increases age specific mortality decreases EX birds sea urchins o time scale must be considered EX newborns are at risk during first month of life Type III while humans are Type I