Why did oxygen have to be present in the earth’s atmosphere when the first living organisms emerged?

Oxygen was essential for the emergence of life on our planet. This is due to the fact that this particular chemical belongs to the macronutrients that form cells. In addition to oxygen, the presence of hydrogen and carbon was also required. Only three of these macronutrients make up approximately 80% of the chemical composition of the cell. Oxygen is necessary to maintain cell life, to create various substances, and so on. Although not all life forms need this gas. Viruses can calmly reside in a vacuum and wait to enter the cell for their activation.