Figure 12.1 The exponential growth model. (a) Over time, a population living under ideal conditions can experience a rapid increase in population size. This produces a J-shaped curve. (b) Human population growth is an excellent example of a J-shaped curve.

Data from http://www2.uvawise.edu/pww8y/Supplement/ConceptsSup/PopulationSup/ChartWldPopGro.html.