Exponential growth refers to the growth rate in which the population grows faster irrespective of the population size. This growth may go on for a long time until there are no enough resources to meet the needs of the rapidly growing population.
When there are plenty resources population growth is exponential which when recorded in a line graph of population over time it will result into a J-shaped curve. When resources become insufficient to meet the needs of the available population number the population will decrease resulting to logistic growth.
