<P> Living organisms require available energy to stay alive , such as the energy humans get from food . Human civilization requires energy to function , which it gets from energy resources such as fossil fuels , nuclear fuel , or renewable energy . The processes of Earth 's climate and ecosystem are driven by the radiant energy Earth receives from the sun and the geothermal energy contained within the earth . </P>
where does the energy for most external processes on the earth come from
the radiant energy Earth receives from the sun the geothermal energy contained within the earth