. Elements of ecology. Ecology. 340 Relations within the Species form. Illustrations of such curves of growth for laboratory cultures of Protozoa, yeasts, Drosophila, flour beetles, and water fleas, and for natural populations of bees, ants, thrips, sheep, and other animals are discussed in further detail by Alice et al. (1949, Ch. 21). The growth of man's population follows a similar pattern whether examined in individual regions or in the world as a whole. A plot of the census records for the United States for the years up to 1940 is shown in Fig. , and the curve has been extrapolated by
. Elements of ecology. Ecology. 340 Relations within the Species form. Illustrations of such curves of growth for laboratory cultures of Protozoa, yeasts, Drosophila, flour beetles, and water fleas, and for natural populations of bees, ants, thrips, sheep, and other animals are discussed in further detail by Alice et al. (1949, Ch. 21). The growth of man's population follows a similar pattern whether examined in individual regions or in the world as a whole. A plot of the census records for the United States for the years up to 1940 is shown in Fig. , and the curve has been extrapolated by fitting the logistic func-. 1700 20 40 60 80180020 40 60 801900 20 40 60 80 2000 20 40 60 802100 Year Fig. Growth curve of the population of the United States, showing census counts from 1790 to 1950. The logistic function has been fitted to the counts from 1790 to 1910 and extrapolated to 2100. The agreement of the extrapolation with the counts for 1920 to 1950 is shown, and a cessation of growth about the year 2000 is indicated. (Modified from Pearl, Reed, and Kish, 1940.) tion. The agreement of the 1950 census figure of 151 million with the extrapolated curve and the indication of an asymptote at about 184 million in the year 2100 may be observed. Equilibrium and Fluctuation The logistic curve discussed in the previous section applies only to periods of population growth (when A^ M) and to situations in which the rate of increase is controlled only by density-dependent factors. Since the inhabitants of a natural area have mostly been present for a long time, we see the initial stages of population growth only in special instances. The early part of population increase is. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Clarke, George L. (George Leonard), 1905-. New York, Wiley
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