Influence of UV radiation on the growth of cyanobacteria in the Archean and oxygenation of the Earth
Today I propose to plunge into the more remote prehistoric past of our planet, more than 2 billion years ago. Many events and processes in this period have not yet been fully understood, but every year researchers learn more about evolution on a younger planet. This review will address what helped early organisms, such as cyanobacteria, survive in more severe conditions associated with high levels of UV radiation without the ozone layer, and oxygenate the oceans billions of years ago and create conditions for the development of life, The way we can imagine it over the past millions of years. This can also be used as an example for a better understanding of the potential for the appearance of biospheres on the surfaces of exoplanets that are exposed to elevated levels of UV radiation.
Solar ultraviolet radiation is the key factor controlling the habitation of planetary surface media and regulating the evolution of life. Up to 2.4 billion years and the development of the protective ozone layer, the flux of UV radiation, in particular with wavelengths corresponding to bactericidal UV radiation that reached the surface of the Archean Ocean, was an order of magnitude higher than today. As a result, the rate of damage to DNA, unprotected organisms, could limit the size and scale of the biosphere. In order to survive, photosynthetic microorganisms such as cyanobacteria in the evolution process would require DNA repair mechanisms or protein metabolism associated with the synthesis of their own proteins and amino acids by borrowing components from the environment to avoid damage caused by UV radiation, and also create environmental mechanisms to protect against harmful effects. In addition, a new interest in the ability of life to carry a high radiation environment was caused by the recent discoveries of terrestrial planets in the habitable zones of a number of nearby red dwarfs, such as, for example, TRAPPIST-1 and Proxima Centauri. They have significantly different stellar spectra compared to the Sun, and planets are much closer to their stars than Earth, which probably leads to significantly larger fluxes of ultraviolet radiation on the surface of these exoplanets. It is worth mentioning that as of September 1, 2018, scientists have detected 3823 exoplanets.
The video was created on the basis of the article:
UV radiation limited the expansion of cyanobacteria in early marine photic environments
doi.org/10.1038/s41467-018-05520-x
of August 06, 2018
Fragments of the video are kindly provided: ESA / Hubble, ESO./L. Calçada / Nick Risinger (skysurvey.org)
European Southern Observatory (ESO) and NASA
#science #biology #Earth #evolution
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