Rule stating that as we move toward the polar region from tropics the size of organism increases is:
Allen's rule
•Allen's rule is a biological rule posited by Joel Asaph Allen in 1877. The rule says that the body shapes and proportions of endotherms vary by climatic temperature by either minimizing exposed surface area to minimize heat loss in cold climates or maximizing exposed surface area to maximize heat loss in hot climates.
•Bergmann's rule is an ecogeographic principle 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.
•Fisher's principle is an evolutionary model that explains why the sex ratio of most species which produce offspring through sexual reproduction is approximately 1:1 between males and females. It was famously outlined by Ronald Fisher in his 1930 book The Genetical Theory of Natural Selection.
•Cope's rule, named after American paleontologist Edward Drinker Cope, postulates that population lineages tend to increase in body size over evolutionary time. It was never actually stated by Cope, although he tended to hypothesize the occurrence of linear evolutionary trends.