What Is the Difference Between Exponential and Logistic Population Growth?
A population with essentially unlimited access to resources grows exponentially. Exponential growth starts out slowly and then proceeds faster and faster as the population increases. Plotting the number of individuals against time yields a I-shaped exponential growth curve (Figure 3-20a). Logistic growth involves (1) exponential population growth when there is a steady decrease in population growth with time as the population encounters environmental resistance and approaches the carrying capacity of its environment and levels off. After leveling off, a population with this type of growth typically fluctuates slightly above and below the carrying capacity. A plot of the number of individuals against time yields a sigmoid, or S-shaped, logistic growth curve (Figure 3-20b). Figure 3-21 shows the logistic growth of the sheep population on the island of Tasmania, south of Australia, in the early 19th century. Figure 3-20 Theoretical population growth curves. (a) Exponential growth, in whic
