Living organisms consist of about 70 different elements, by chance largely in about the same proprotions as those of the Earth crust.
Some rare elements are toxic in nature, because they interfere with the function of the body, but all the common ones are used as constituents.
The basic functioning of all organisms are nearly the same at the molecular level, whether they are animals, plants or micro-organisms.
Of these elements, a few can exist in the air, because they have gaseous phases or compounds that are gases (blue on the picture). Because of their gaseous phases, they are in practice limitless in their capacity for spreading all over the globe. A local deficiency is very unlikely to happen.
The other elements (red) normally have no gaseous phases, so they are limited to spreading as ions in liquid phases or as solids. This limits their spreading capacity and loal deficiencies might occur.
In water, however, most elements can spread relatively easily. Local deficiencies are therefore very rare in the sea.
It might be this difference that restrained the adaptation of life to land. Only by special adaptations, life was able to establish on the nutrient-poor terrestrial area.
Of the non-gaseous elements, most exist in abundance compared to what is needed in the organism. There is one exception, however.
Phosphorus is needed in about a 10 times higher concentrations in our bodies than its average abundance in the Earth crust.
In the sea, the lack can be mitigated by continuous pumping of large volumes in order to make up for the weak solution in the sea water (although recycling is a solution often used even here).
But on land, because of the constant washing out of nutrients from land to sea with fresh water, there is in effect a constant threat of phosphorus deficiency. For life on land, therefore, recycling of phosphorus is utterly important.
Therefore, during ecosystem development, the general tendency to increase exergy consumption is expressed, among else, in an increased retention of nutrients, especially phosphorus. Highly developed (mature) ecosystems, e.g. tropical rain forests, show a very small loss of nutrients. For an ecosystem, losing phosphorus is like losing blood for an animal.
The method used to keep precious (limiting) resources in order to increase or maintain exergy consumption is called the regenerative cycle. It is a very general method that exists on all organizational levels.
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