Currently many life forms differing from simple prokaryotes to the multicellular animals with highly sophisticated nervous systems exist on Earth. It is obvious that survival of these species was possible due to the optimal adaptation to the changeable environmental conditions. However it is not clear which parameter can be used to assess optimal species adaptation and survival. The theory of biological energy intensity (Milewski & Mills, 2010) provides the ultimate and universal parameter that allows explaining why certain life forms are dominating in certain environments.
In order to evaluate life efficiency several parameters have been proposed, such as replication, biomass accumulation, complexity and information. However those are not sufficient to explain the existence of dominant organisms. For example, unicellular Amoeba dubia contains as much as 200 hundred times of DNA amount as compared to human cell (Gregory & Hebert, 1999). Genetic complexity is also a not reliable estimation of dominance because for example wheat (Triticum sp) contains much more genes in its genome than human genome. With regard to the information it is clear that human brain has the most sophisticated neural network with powerful ability to store and process information. However simple prokaryotic organisms do not possess any neural systems and at the same time they dominate in many terrestrial and aquatic environments.
Considering disadvantages of all above mentioned parameters the authors (Milewski & Mills, 2010) have proposed new energy intensity (E) parameter as a major driving force for all organisms to achieve an evolutionary success. It is defined as amount of chemical and electromagnetic energy use per square meter per unit of time (Joules/m2 year). The use of Earths area in this equation instead of area of organism allows comparing on the uniform basis organisms that greatly differ in size and volume. The theory of maximising energy intensity predicts that in nutrient rich environments the microbes will dominate due to the fact that they have a fast metabolic turnover and reproduction. On the contrary in the nutrient scarce environments the macrobes (big animals and trees) will have an evolutionary advantage because they are able to collect and store the necessary catalytic elements (metals) that are indispensable for all metabolic processes.
In the course of evolution the life forms developed from simple prokaryotic (lacking nucleus) organisms to the eukaryotic (possessing nucleus and mitochondria) multicellular structures with elaborated nervous and memory systems. In order to compare evolutionary fitness of above stated organisms an energy intensity parameter was proposed. The fundamental basis of this energy efficiency is an ability of life forms to convert chemical potential energy of different molecules (such as ATP) directly to the electromagnetic kinetic energy through photons, electric charges and electron transitions. That allowed to avoid losses of energy via heat dissipation and led to the ultimate success of life on our planet.
References
Gregory, T., R. & Hebert, P. D. N. (1999). The modulation of DNA content: proximate causes and ultimate consequences. Genome Research 9, 317–324.
Milewski, A, V &. Mills, A, J. (2010) Does life consistently maximise energy intensity?Biological Reviews, 85, …