Math in the Natural Sciences

Math and the Environment

What are survivorship curves?

Survivorship curves record and plot the fate of the young, and their chances of survival in key age categories. Significant factors affecting all populations are birth rates, death rates, and longevity. By recording the numbers of births and deaths over a period of time, researchers can determine the average longevity of organisms in each age class; these numbers tell a great deal about a population.

There are three basic survivorship curves. Type I curves represent species that have offspring with a high survival rate, with most living to a certain age and then dying; humans are an example. Type II curves represent organisms with a steady death rate from the time they are born or hatch until they die; their survivorship varies and includes such species as deer, large birds, and fish. Type III curves include those organisms that have a low survivorship shortly after being born, but with a high longevity for the individual organisms that survive; maple and oak trees can be included in this category.


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