Figure 12.16 Logistic growth in two species of Paramecium. (a) When Paramecium aurelia was raised under low or high food supply, the population size—measured in terms of the total volume of protist cells—grew rapidly at first and then slowed as they reached their carrying capacity. When twice as much food was provided, the species achieved a population size that was twice as large. (b) A similar pattern was found for another species of protist, Paramecium caudatum.

Data from G. Gause, The Struggle for Existence (Zoological Institute of the University of Moscow, 1934).