First we distinguish Vegetal from Animal Populations. the section called Vegetal Populations>
Inside Animal Populations, we make the difference between two category of individuals: in two words, larger and smaller ones.
The first category contains humanoids with their predators (like wolf, bear, dragon, etc) and their victims (rabbit, sheep, trout). More generally this category is the one of all smarter animals and of all possible characters. We will qualify this animals of "Major'.the section called Populations of major animals>
All other animals will belong to the second category (insects, plankton, bacteria, etc). These animals will be qualified of 'Minor'. the section called Population of minor animals>
The reason of this separation is an issue of processing power and memory use... It is difficult in present time to envision simulating one billion ants or one billion bacteria. And moreover, the impact on the game would be minimal. For these reasons, a fraction of the fauna will be globally simulated: All individuals of the second category will be considered as part of the local fauna. the section called Remarks on the Game>