When it comes to talking about our environment, ecologists and those involved in the sciences in general use many terms, however, if you concentrate on how long and complicated these terms are you will miss out on the fascinating phenomena they describe, an example is the term polymorphism.

When species look different from each other, even if the difference is slight, it is easy to say that they are two different species.

But in nature we have what is known as polymorphism. This occurs when two or more clearly defined forms of the species appear in the same population.

Before going any further, let me clarify that polymorphism is not a mechanism by which new species come about, it is more related to how individuals of a species become adapted to their environment.

In polymorphism, each form is referred to as a morph. However, in order to be classified as being polymorphic, the morph must occupy the same habitat at the same time. Usually the amount of morphs in a population stays relatively constant. However, natural and artificial selection can change the numbers of morphs. Also, certain conditions have to be present; for instance, the characters that make the morphs different from each other cannot be of a continuous nature, for example, its weight.

Polymorphism is triggered by two aspects; the environment and their genetic make up. These two are called the switch mechanisms. Polymorphism triggered by environmental conditions is called polyphenism, Probably one of the most well-known examples of polymorphism is of the Peppered Moth (Biston betularia).

These light coloured moths rest on the trunks of trees camouflaged by the lichens on the bark. However with the sudden growth of industrial pollution in the 19th century, the light coloured lichens which they used as camouflage became blackened by the soot. Therefore, the light coloured moths stood out and were easy prey for their predators. In 1848, a dark version of the moth was found in Manchester in the United Kingdom. However, by 1895, 98% of the individuals of this species in the area were black.

Another example of how the environment causes polymorphism is sex determination of the offspring where the temperature determines if the embryos will develop into either a male or a female as in alligators. This is a good example of how environmental factors exert a great influence on animals. However polymorphism caused by environmental factors is less common.

The second switch mechanism that triggers polymorphism is the genetic make up of the organism. In order for polymorphism caused by genetics to take place, three conditions need to be present; firstly, it must be one inbreeding population. Secondly there must be discrete forms and finally their presence is not maintained by mutations. In the last condition it should be noted that it is a common mistake to think that morphs are individuals that have come about as a result of a mutation. In order to definitively say that morphs occur for this species, the least common morph has to occur in the population with the frequency that it cannot be regarded as a mutation.

However, if I were to go into the genetics of polymorphism in detail it would become too complicated, which is also not the aim of this article; rather it is to acquaint you with the concept of polymorphism. An example of genetic polymorphism is sexual dimorphism, where the males and females of the same species differ in appearance.

This occurs with the White-Bearded Manakins (Manacus manacus) birds, where the males are brightly coloured while the females are a dull brown, blending in with the forest floor.

This is quite advantageous as the males job is to attract females to mate with, hence they have to be conspicuous while the females make nests under bushes on the forest floor to raise her brood, so in order to avoid drawing attention to her and her brood she is cryptically coloured.

There are many other examples of genetic polymorphism in human populations as well for example, sickle cell anaemia and the different blood groups present. However, in terms of blood groups the differences can only be detected with a test, which in this case they are referred to as cryptic morphs.

Therefore we see that in order for an organism to survive, forming different species is not the only solution, a species can develop different forms that are more adapted to the conditions in an area.

But whether these forms are triggered by environmental factors or by genetics, they both serve the same purpose of ensuring the survival of a species.