For my research for information for topics to write on I have come across many rules that pertain to biology and ecology.

Many of these are not widely known so I thought I would take the opportunity to briefly introduce and explain the principle behind each. The rules introduce some interesting concepts as to how organisms function in specific conditions. So what qualifies these as rules? Well the term "rule" is applied to generalisations that have arisen from observations over a series of organisms. One way to looking at these rules is to separate them into categories. However, there are too many so I have split them up into a two-part article.

Conservation of body heat and therefore energy is very important to many organisms, so it should come as no surprise that there are quite a few ecological rules in this area. One such rule is Allen's Rule which was developed in 1877 by Joel Asaph Allen and states that endotherms(warm blooded) from colder climates usually have shorter appendages or limbs than their counterparts in warmer climates. Endothermic animals also called warm-blooded animals can regulate and maintain their body temperature. The theory behind this is that the surface area available to get rid of heat is less in shorter limbs therefore less heat and thus energy is lost. This is important to animals that occupy cold climates which need to conserve heat. However, the opposite is so for warmer climates where heat needs to be expended quickly to prevent the animal from overheating.

Another rule that pertains to endothermic animals is Gloger's Rule. This rule states that, "within a species of endotherms, more heavily pigmented forms tend to be found in more humid environments such as near the equator". This is actually seen in humans where persons in the Southern Hemisphere are darker than those in the drier northern areas.

This rule developed through his observation that birds in more humid areas had darker feathers. One proposed reason is that the humidity in these habitats causes more bacteria on the feathers, but darker feathers are more difficult for the bacteria to break down, due to the presence of eumelanins.

Eumelanins are the most common form of biological melanin found in skin and hair.

But there are rules that include ectotherms as well, also called cold-blooded animals cannot regulate their own body temperature and it actually fluctuates according to the temperature of the surroundings, for example, reptiles and amphibians. It known as the temperature–size rule where, "ectothermic animals in areas of high temperatures are relatively small as adults"

Another rule in this category is Bergmann's Rule that basically states that animals in colder areas tend to be larger than those in tropical or warmer areas. This is similar to Allen's Rule in that it deals with surface area, and states that larger animals have a greater surface area relative to its total volume therefore they will lose heat more slowly compared to smaller animals.

The final rule in this category that I could find is called the Egg Rule which states that, "the average number of eggs in a set or clutch laid by songbirds and several other kinds of birds, increases as one moves north in latitude". This may be because songbirds can raise a single brood per season while further south, the production of multiple broods is possible.

The is one rule that does not fit into any category; this is Jordan's Rule which has two applications. With respect to zoology it states that "fishes in areas that have low temperatures tend to have more vertebrae than those in warmer areas".

However, when applied to the area of evolution, it states that, "organisms that are closely related tend to occupy adjacent areas rather than identical or areas that are distant from each other."

These are just some of the many rules that have developed over the years to describe the conservation of body heat and appearance of animals in certain regions. Next week we will look at some rules that cover location, size and behaviour.