RULE 5 The abundance of organisms in nature varies with their size. - John Tyler Bonner

Merino sheep always flock while Highland sheep spread. The reason is that in Spain the summer feeding and winter feeding of the sheep were widely separated, and the shepherd had to march them many miles along the road and through the villages. If they did not flock, they would soon be lost in their seasonal journey. On the other hand, the Scottish shepherd never moves his Highland sheep large distances and wishes them to spread out as much as possible over the hills so that no one area is overgrazed, and both of these characteristics have been achieved by selective breeding.

RULE 4 The rate of various living processes varies with size, such as metabolism, generation time, longevity, and the speed of locomotion.

RULE 3 The division of labor (complexity) varies with size.