| Abstract [eng] |
The present atmosphere of the Earth is a result of the evolution that began at the time of the planet`s formation 4, 5 milliard years ago. Many experts think that this evolution was mostly dependent on the development of the Earth`s biosphere. The first organisms that appeared on the Earth grew up and were reproduced at a fast rate. The increase of the biomass of the ecosystem and the whole biosphere was one of the most distinct trends of the evolution. Accumulation of detritus and mineral resources of organic origin grew up with the increase of the biomass. This kind of accumulation is proved by the current large quantities of mineral resources of organic origin. With the accumulation of the biomass of the biosphere the amount of oxygen in the environment increased whereas the amount of carbon dioxide decreased as specified by the oxygen photosynthesis equation (CO2 + H2O → (CH2O) + O2). Accumulation of oxygen in the atmosphere caused formation of ozone (O3), thanks to which life could exist both in the water and on the dry land. Evolution of plants on the dry land led to the increase in the production rate of the first products and appearance of lignin, a heavily decomposable compound. Appearance of lignin, an increased biodiversity, a faster rate of rock washout caused by symbiotic interaction, wide spreading of lignified plant on the Earth has resulted in larger global amounts of biomass, a faster burial of organic materials and increased amounts of oxygen, and in the respective reduction of carbon dioxide concentrations in the atmosphere. Nowadays, many experts agree that the whole or almost the whole of the existent oxygen in the combined and free condition is most likely of biogenic origin. On the contrary, changes in the levels of carbon dioxide are mainly attributed to non – organic and geochemical phenomena as opposed to biological ones. The created models for calculation of oxygen and carbon dioxide contents in the atmosphere are not absolutely accurate. Many modellers emphasize one or several criteria whereby changes in the contents of atmospheric carbon dioxide are calculated within a geologic time interval; however they fail to take into account many other phenomena that make effect on the amount of carbon dioxide. |
