Figure 2.

A depiction of the inner and outer worlds of individuals divides population models into kinds according to how the models span this universe: LDMs (lumped dynamics models), ABMs (agent-based models), and CPMs (computational population models). Agents at the boundary of the two worlds inherit their designated type from their internal state, with some designations, such as sex, being fixed early on, other designations, such as age class membership progressing linearly, and finally designations related to biomass and disease classes changing dynamically with food intake rates and immunological interactions. The internal states of individuals, however, are essentially driven by the inputs they receive from their external worlds (e.g. food intake, pathogen transmission, conspecific and heterospecific interactions).