What significance for the development of life on Earth was the emergence of photosynthesis?

The emergence of photosynthesis by cyanobacteria (oxygen-free photosynthesis) freed life from dependence on organic compounds of abiogenic origin. Living organisms themselves began to produce organic matter. Organic matter of biogenic origin began to accumulate on the planet. At the same time, living organisms began to use directly the energy of the Sun and accumulate it.
During evolution, the process of photosynthesis gradually became more complicated. This led to three very important consequences that ensured the further development of life on Earth. Firstly, the reserves of organic substances necessary for the nutrition of heterotrophic organisms began to be created. As a result, many heterotrophs arose.
Secondly, as a result of photosynthesis, oxygen appeared on Earth, which significantly changed the living conditions. Organisms formed, initially capable of merely surviving in the presence of oxygen. As it accumulated in the Earth’s atmosphere, prerequisites were created for the appearance of cells with aerobic respiration, which is energetically 19 times more effective than fermentation. Thus, along with anaerobic metabolism, organisms have mastered the aerobic method of energy extraction. Thirdly, oxygen in the upper atmosphere formed an ozone screen that protected the Earth’s surface from harmful UV rays and created the conditions for organisms to escape from land to land.

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