0.75
0.25
75
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0.75
0.25
75
%
The Survivorship Calculator computes the proportion of an original cohort that survives to a given age class. Survivorship (lx) is a foundational concept in life table analysis and population ecology. By tracking how many individuals from a birth cohort remain alive at each age, ecologists can characterize the mortality pattern of a species.
Survivorship curves are classified into three types: Type I (most mortality in old age, like humans), Type II (constant mortality across ages, like some birds), and Type III (high juvenile mortality, like many fish and plants). This calculator provides the lx value and cumulative mortality for any cohort and age combination.
Survivorship is calculated as:
lx = nx / n0
Where:
The value lx ranges from 1.0 (at birth, all alive) to 0.0 (all dead). Cumulative mortality is simply 1 - lx. These values form the basis of life tables used extensively in ecology, actuarial science, and epidemiology.
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Results
75% of the original cohort survives to age 5, indicating moderate early mortality typical of Type II survivorship.
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Results
Only 5% survive to age 1, characteristic of Type III species like marine invertebrates or many fish species.
Survivorship (lx) is the proportion of an original birth cohort that survives to a given age. It is a key component of life table analysis and is used to construct survivorship curves that visualize mortality patterns across the lifespan of a species.
Type I curves show low mortality until old age (humans, large mammals). Type II curves show constant mortality at all ages (some birds, lizards). Type III curves show very high juvenile mortality with few survivors reaching adulthood (oysters, sea turtles, many plants).
Survivorship values form a column in the life table alongside age-specific mortality rates (qx), death counts (dx), and life expectancy (ex). Together, these columns provide a comprehensive picture of how a cohort ages and dies, enabling population projections and conservation planning.
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