AllanBergmann rule




Different Yet Complimentary


Even though the Bergmann rule and Allan rule are different rules entirely they are both complementary to each other. In 1847 Bergmann observed that within the same spices of warm-blooded animals, populations have less bulky individuals are more often found in warm climates near the equator while, those with greater bulk, mass, are found further from the equator in colder regions. This is due to the fact that big animals generally have larger body masses that result in more heat being produced. The greater amount of heat results from there being more cells. A normal by product of metabolism in cells is heat production. Subsequently the more cells an animal has, the more internal heat it will produce. In addition, larger animals usually have smaller surface area relative to their body masses and therefore are comparatively, in efficient at radiating their body heat off into the surrounding environment. This is illustrated when the volume increases twice as fast as the surface size. Relatively less surface area results in relatively less heat being lost. In 1877, Allen went further than Bergmann in observing that the length of arms, legs, and other appendages also has an effect on the amount of heat lost to the surrounding environment. He noted that among warm-blooded animals, individuals in populations living further away from the equator in colder environments. This is due to the fact that a thin body with relatively long appendages is less compact and subsequently has more surface area. The greater the body area, the faster body heat will be lost to the environment. A tall and slender individual will have the same volume but greater surface area. It is comparable to an animal with arm and legs. I will demonstrate to you in this essay that even though the Allan rule and Bergmann rule are two different rules they are also complementary to each other. I will show this through explaining each on thoroughly, compare and contrast them and by presenting examples for each rule.

Carl Bergmann was a 19th century biologist who pointed out that amongst birds and mammal individuals of the same species tend to be larger and heavier when they lived in colder climates. This applies to pumas, bears, koalas, penguins, etc. Even in the case of people, there is an obvious difference between the height and weight of a high-latitude Scandinavian and those of an equatorial pygmy. The larger size increases the distance between the environment and the creature’s core, which has to be maintained near 37 degrees Celsius. The Bergmann rule is a scientific theory that states that the further from the equator, an animal needs a larger body with less relative surface area to help it stay warm in the winter. Conversely, smaller animals with a relatively larger surface area can dissipate body heat easier, helping them remain cool. The relationship between size and temperature was initially observed for endothermic animals and extended to insects, constituting Bergmann’s rule. The altitude and latitude, in which the insects develop, through the temperature, can influence their size.


Joel Asaph Allan, naturalist, born in Springfield, Massachusetts on July 19th 1838. He studied first at the Wibraham Academy, and then at the Lawrence Scientific School under Agassiz, where he devoted special attention to zoology, and was one of the assistants that accompanied Agassiz on the expedition to Brazil in 1865. He visited Florida in 1869, and the Rocky Mountain region in 1871, with the scientific exploring parties, and in 1873 was the chief of expedition sent out by the Northern Pacific railroad. In 1870 he became an assistant in ornithology at the museum of comparative zoology at Cambridge, and in 1871 received the Humbolt Scholarship. Since 1885 he has been curator of the department of mammals and birds in the American Museum Of Natural History, New York. In 1871 he was made a fellow of the American Academy Of Arts and Sciences, and in 1876 a fellow of the Natural Academy Of Sciences. He is also a member of the American Association For The Advancement Of Science, and of the American Philosophical Society. From 1883 to 1886 he was president of the American Ornithologists’ Union. He is the author of numerous reports and scientific papers among which are “On Geographical Variation In