 Figures 2a and 2b: The Logistic Growth Model   The figure on the top (from Gause [1934], p. 35) shows theoretical curves. “Geometric increase” represents the exponential growth model discussed in the text; “saturating population” refers to the carrying capacity (see  Box 2).  The figure on the bottom (from Gause [1934], p. 36) shows an example of an empirical growth curve obtained in the laboratory. If the curve is fitted to a logistic curve (to which it shows similarity), then K = 375 is the estimated carrying capacity.