consider a population of insects in which females reproduce only once a year and then the adult population dies.In this case of discrete breeding, 
R = net reproductive rate, Net reproductive rate is used because it is 
the observed rate of natural increase after deaths have occurred, this graph shows how the population would grow year after 
year for 10 years, assuming that R stayed constant from generation to generation.With exponential growth, the number of individuals added each generation increases rapidly due to the total number of reproductive females increasing in the population.This growth curve, which is roughly J shaped, depicts exponential growth.Exponential growth phase: During this phase, growth is accelerating.