II. Survivorship

A. Definition 1. A survivorship curve shows how likely an individual is to die at a certain age a. 3 types of populations tend to appear 1. Type I: most deaths at old age 2. Type II: equal deaths at all ages 3. Type III: most deaths at young ages

2. Also can use data to calculate life expectancy which tells length of time an individual can expect to live. 3. Creating a life table collects all pertinent information for an age group. a. X= age interval b. D(x)= # of individuals dying c. S(x)= # of individuals surviving (total individuals –D(x)) d. L(x)= average # of individuals allive [(S(x) + S(x+1))/2]

e. T(x)= # of time units for all individuals (years x S Li) 1. goes from bottom up f. e(x)= life expectancy (T(x)/ S(x)) g. q(x)= age specific mortality rate (fraction dying) 1. q(x)= D(x)/S(x) h. l(x)= age specific survival (fraction still alive) 1. l(x)= S(x)/S(0)

4. Table should be headed as follows : Age Class; D(x); S(x); L(x); T(x); e(x); q(x); l(x)

5. Data can be graphed to give big picture a. Survivorship curves are l(x) vs age class b. Mortality curves are q(x) vs age class