Why are green plants necessary for living organisms?

(N/A) $\Rightarrow$ All animals,including human beings,depend on plants for their food. Green plants synthesize the food they need,and all other organisms depend on them for their nutritional requirements.
$\Rightarrow$ Green plants carry out 'photosynthesis',a physico-chemical process by which they use light energy to drive the synthesis of organic compounds.
$\Rightarrow$ Since green plants perform photosynthesis and produce their own food,they are classified as autotrophs,while other organisms are heterotrophs.
$\Rightarrow$ Ultimately,all living forms on Earth depend on sunlight for energy. The conversion of solar energy into chemical energy by plants through photosynthesis is the basis of life on Earth.
$\Rightarrow$ Photosynthesis is essential for two primary reasons:
$(A)$ It is the primary source of all food on Earth.
$(B)$ It is responsible for the release of oxygen into the atmosphere,which is essential for the respiration of all aerobic living beings.