Bergmann's rule is an ecogeographical rule that states that within a broadly distributed taxonomic clade, populations and species of larger size are found in colder environments, and species of smaller size are found in warmer regions. Allen's rule. The principle holding that in a warm-blooded animal species having distinct geographic populations, the limbs, ears, and other appendages of the animals living in cold climates tend to be shorter than in animals of the same species living in warm climates. Blackman’s law of limiting factors: When a process depends on a number of factors, its rate is limited by the pace of the slowest factor. Blackman's law of limiting factors determines the rate of photosynthesis. Cope's rule:Population lineages tend to increase in body size over evolutionary time.