Explain why only a fraction of energy from the sun that reaches the biosphere is available for use by photosynthetic organisms

the truman doctrine was an american foreign policy whose stated purpose was to counter soviet geopolitical expansion during the cold war. it was announced to congress by president harry s. truman on march 12, 1947, and further developed on july 12, 1948, when he pledged to contain threats to greece and turkey.

its probably to later but whats the question