Final answer:
A survivorship curve is the best method to show an individual's life expectancy in a population, graphing survival rates across different age intervals.
Step-by-step explanation:
The best method to show the life expectancy of an individual within a population is through a survivorship curve. Survivorship curves are graphs that display the number of individuals surviving at each age interval versus time. They are a key tool for population ecologists, revealing the patterns of mortality and survival within a population.
There are three types of survivorship curves: Type I, where mortality is low until older ages, typical of humans and many mammals; Type II, where mortality is constant across all ages, seen in some bird species; and Type III, where mortality is highest in early life, as seen in many trees and marine invertebrates.