All energy is derived from the transfer of electrons.Chemotrophsdependon oxidation or breaking chemical bonds of inorganic or organic compounds for energy.[ Select ]Y use solar energy (light) to excite an electrons to a higherenergy state, and thereby produce energy.Organisms can be classified based on the carbon source. Autotrophs are organisms that convert[Select ], an inorganic molecule, to synthesize all theirorganic carbon compounds. On contrary, heterotrpohs use[ Select ]as nutrients to sustain their carbon needs.