Final answer:
Bergmann's rule states that larger-sized populations or species are found in colder environments, while smaller-sized populations or species are found in warmer environments.
Step-by-step explanation:
Bergmann's rule states that within a taxonomic group, larger-sized populations or species are found in colder environments, while smaller-sized populations or species are found in warmer environments. This rule is supported by the fact that larger organisms have a smaller surface area-to-volume ratio, which helps them retain heat better in cold environments.