1) plants in the process of photosynthesis form and emit oxygen into the atmosphere;
2) living organisms use oxygen during respiration;
3) in the cells of living organisms, oxygen in the process of energy metabolism participates in redox reactions, as a result of which the end products of exchange are formed – water and carbon dioxide.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.