Any living organism that synthesizes organic
substances from inorganic molecules by using
light or chemical energy. All green plants 
and many planktonic organisms are autotrophs,
using sunlight to convert carbon dioxide and
water into sugars by photosynthesis.
Some bacteria use the chemical energy of
sulphur compounds to synthesize organic
substances.  Materials synthesized and stored
by autotrophs provide the energy sources of
all other organisms; they are the primary
producers in all food chains.

Subject by: Russell Webb