Bergmann's rule

Berg·​mann's rule | \ˈbərg-mənz, ˈberg-\

Definition of Bergmann's rule 

: a statement of the principle that within a polytypic wide-ranging species of warm-blooded animals the average body size of members of each geographic race varies inversely with the mean environmental temperature

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History and Etymology for Bergmann's rule

after Karl Bergmann †1865 German biologist

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