Alive individual Died this age Simulated ln S(a) Theoretical ln S(a)
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Cohort exhausted — press Restart

Survivorship Curves — Type I, II & III Mortality (2D)

One of population ecology's founding tools is the survivorship curve: chart the log of a birth cohort's surviving fraction against age and the shape immediately tells you how a species spends its mortality risk. This simulator seeds a 2D cohort grid of individuals and ages them one step at a time under a real hazard function — Type I (mortality concentrated late, like large mammals), Type II (constant hazard, a straight line on the log plot, like many birds and hydra), or Type III (mortality concentrated in infancy, like fish and insects). Each death is a genuine stochastic draw against the analytic survival probability, plotted live alongside the exact theoretical curve, while life expectancy at birth is integrated from the same hazard schedule in real time. Drag the canvas to pan between the cohort and the plot, and scroll to zoom.