Photosynthesis is the main source of biological energy, photosynthetic autotrophs use it to synthesize organic substances from inorganic ones, heterotrophs exist due to the energy stored by autotrophs in the form of chemical bonds, releasing it in the processes of respiration and fermentation. The energy received by mankind when burning fossil fuels (coal, oil, natural gas, peat) is also stored in the process of photosynthesis.
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.