Chapter 5, Problem 1ER

Summary Introduction

To discuss: Definition of Bergmann’s rule and Allen’s rule

Introduction:

Climate adaption:

Climate adaptation refers to the ability of organisms to adapt to changes in the climate. Humans are homoeothermic where they maintain a constant temperature and can tolerate minimum temperature. However, a body temperature above 104 ­ 107 °F for an extended period leads to organ failure and death.

Explanation of Solution

Bergmann’s rule:

The rule states that mammals and birds in the hot region will have smaller bodies than cold-adapted mammals and bird populations. Consequently, human populations adapted to hot climates tend to have small and narrow bodies.

It refers to the principle that an animal’s size is heat-related. Smaller bodies are adapted to hot environment and larger bodies are adapted to cold environments. Both of these rules cause systematic changes in the surface area to volume ratios.

Allen’s rule:

The rule states that mammals and birds in heat-adapted area will have long limbs, which tend to have greater body mass, and thus, promote heat dissipation. Mammals in cold region will have short limbs, which tend to have shorter body mass and thus, promote heat conservation. The principle states that the animal’s limb lengths are heat-related. Limbs are longer in hot environments and shorter in cold environment.

Conclusion

Bergmann’s rule states that mammals and birds in the hot region will have smaller bodies than cold-adapted mammals and bird populations. Allen’s rule states that mammals and birds in heat-adapted area will have long limbs, which tend to have greater body mass, and thus, promote heat dissipation.