In biology, a survivorship curve is a type of graphic that shows the rate of survival of individuals of one species along time. This type of graphics includes three types of curves. The first one or Type I occurs when individuals can survive during the first ages but by the middle and end of life, the survival rate falls. The second one or Type II occurs in species in which survival rate slowly declines as time passes. Finally, in the third curve or Type III, there are species that experience difficulties for surviving at the beginning of life by then survival rate stay the same. In the case of humans, most scientists classified our species in Type I because at early age survival rate is mainly high as only a few percentages of the population dies at a young age, but after middle age and in elderly the death rate sharps and therefore survival rate falls.
