Why photosynthesis is considered as the basic unit of life?

Photosynthesis is considered a fundamental process for life because it is how autotrophic organisms, like plants and some bacteria, convert light energy into chemical energy in the form of glucose. This process not only produces the organic compounds that serve as food for these organisms but also generates oxygen as a byproduct, which is essential for the survival of aerobic organisms, including humans. By forming the base of the food chain, photosynthesis sustains ecosystems and drives the energy flow in biological systems. Thus, it is crucial for both the energy needs of living organisms and the overall balance of Earth's atmosphere.