Question

if producers make their own organic substance (food) from inorganic substances (light energy, h₂o, co₂) but consumers have to eat organic substances (food) to make their own inorganic substance (atp energy). what is the actual provider of our worlds energy in most ecosystems? air water sunlight

Explanation:

Producers (like plants) use sunlight (light energy) in photosynthesis to convert inorganic substances ($H_2O$, $CO_2$) into organic food. Consumers then obtain energy by eating these producers or other consumers. The initial energy source that drives this process in most ecosystems is sunlight. Air and water are important for life processes but are not the energy - providing entities in the context of energy flow in ecosystems as described (air has gases like $O_2$ and $CO_2$ which are reactants or products in metabolic processes, water is a reactant in photosynthesis and a medium for many reactions but not an energy source).

Answer:

sunlight