FIG. 46.1 (a) Size, (b) range, and (c) density of a population. The places where populations occur can be mapped, and the numbers of individuals within those populations can be estimated. This information helps us understand what factors limit population distributions. Sources: Data from A. Atkinson, V. Siegel, E. A. Pakhomov, M. J. Jessopp, V. Loeb, 2009, “A Reappraisal of the Total Biomass and Annual Production of Antarctic Krill,” Deep- 7–