Since the advent of chemistry to humanity, it has become clear that everything around consists of a substance, which includes chemical elements. A variety of substances is provided by various compounds of simple elements. To date, 118 chemical elements have been openly and entered into the periodic table of D. Mendeleev. Among them, it is worth highlighting a number of leaders whose presence determined the appearance of organic life on Earth. This list includes: nitrogen, carbon, oxygen, hydrogen, sulfur and phosphorus.
Oxygen: discovery story
All these elements, as well as a number of others, contributed to the development of the evolution of life on our planet in the form in which we are now observing. Among all the components, it is oxygen in nature that contains more than other elements.
Oxygen as a separate element was discovered on August 1, 1774 by
Joseph Priestley. During an experiment to obtain air from mercury scale by heating using a conventional lens, he found that the candle burns with an unusually bright flame.
For a long time Priestley tried to find a reasonable explanation for this. At that time, this phenomenon was given the name "second air". Somewhat earlier, the inventor of the submarine K. Drebbel at the beginning of the XVII century released oxygen and used it for breathing in his invention. But his experiments did not affect the understanding of the role oxygen plays in the nature of the energy exchange of living organisms. However, the French chemist Antoine Laurent Lavoisier was recognized as the scientist who officially discovered oxygen. He repeated the Priestley experiment and realized that the gas produced was a separate element.
Oxygen interacts with almost all simple and complex substances, except for inert gases and noble metals.
Finding oxygen in nature
Among all the elements of our planet, oxygen occupies the largest share. The distribution of oxygen in nature is very diverse. It is present both in bound form and in free. As a rule, being a strong oxidizing agent, it is in a bound state. The presence of oxygen in nature as a separate unrelated element is recorded only in the atmosphere of the planet.
It is contained in the form of a gas and is a combination of two oxygen atoms. It makes up about 21% of the total atmosphere.
Oxygen in the air, in addition to its usual form, has an isotropic form in the form of ozone. The ozone molecule consists of three oxygen atoms. The blue color of the sky is directly related to the presence of this compound in the upper atmosphere. Thanks to ozone, hard short-wave radiation from our Sun is absorbed and does not reach the surface.
In the absence of the ozone layer, organic life would be destroyed like fried food in a microwave.
In the hydrosphere of our planet, this element is in a bound form with two hydrogen molecules and forms water. The proportion of oxygen content in the oceans, seas, rivers and groundwaters is estimated at about 86-89%, taking into account dissolved salts.
In the earth's crust, oxygen is bound and is the most abundant element. Its share is about 47%. The presence of oxygen in nature is not limited to the shells of the planet, this element is part of all organic creatures. Its share on average reaches 67% of the total mass of all elements.
Oxygen is the basis of life
Due to the high oxidative activity, oxygen is quite easily combined with most elements and substances, forming oxides. The high oxidizing ability of the element provides a well-known combustion process. Oxygen is also involved in slow oxidation processes.
The role of oxygen in nature as a strong oxidizing agent is indispensable in the life process of living organisms. Thanks to this chemical process, substances are oxidized with energy release. Its living organisms are used for their life.
Plants - a source of oxygen in the atmosphere
At the initial stage of the formation of the atmosphere on our planet, the existing oxygen was in a bound state, in the form of carbon dioxide (carbon dioxide). Over time, plants appeared that were able to absorb carbon dioxide.
This process became possible due to the emergence of photosynthesis. Over time, during the life of plants, over millions of years a large amount of free oxygen has accumulated in the Earth’s atmosphere.
According to scientists, in the past its mass fraction reached about 30%, one and a half times more than now. Plants, both in the past and now, significantly influenced the oxygen cycle in nature, thereby providing a diverse flora and fauna of our planet.
The value of oxygen in nature is not just huge, but paramount. The animal metabolism system clearly relies on the presence of oxygen in the atmosphere. In his absence, life becomes impossible in the form in which we know. Among the inhabitants of the planet will remain only anaerobic (able to live without the presence of oxygen) organisms.
The intense oxygen cycle in nature is ensured by the fact that it is in three states of aggregation in combination with other elements. Being a strong oxidizing agent, it very easily transfers from free form to bound form. And only thanks to plants that break down carbon dioxide through photosynthesis, is it in free form.
The breathing process of animals and insects is based on the production of unbound oxygen for redox reactions with the subsequent generation of energy to ensure the vital functions of the body. The presence of oxygen in nature, bound and free, ensures the full life activity of all life on the planet.
The evolution and chemistry of the planet
The evolution of life on the planet was based on the features of the composition of the Earth’s atmosphere, the composition of minerals and the presence of water in a liquid state.
The chemical composition of the crust, atmosphere and the presence of water became the basis for the origin of life on the planet and determined the direction of evolution of living organisms.
Based on the existing “chemistry” of the planet, evolution has come to carbon organic life based on water as a solvent for chemicals, as well as the use of oxygen as an oxidizing agent for energy.
Different evolution
At this stage, modern science does not refute the possibility of life in environments other than terrestrial conditions, where silicon or arsenic can be taken as the basis for constructing an organic molecule. And the medium of the liquid, as a solvent, can be a mixture of liquid ammonia with helium. As for the atmosphere, it can be represented in the form of gaseous hydrogen mixed with helium and other gases.
What metabolic processes can be under such conditions, modern science is not yet able to simulate. However, such a direction in the evolution of life is quite acceptable. As time proves, humanity is constantly faced with the expansion of the boundaries of our understanding of the world and life in it.