Photoautotrophs (光能自养生物) Chemoautotrophs(化能自养生物) Because these organisms use light as their energy source,they are called photoautotrophs. Chemoautotrophs are autotrophs that obtain their energy not from sunlight but from certain specific chemical reactions involving only inorganic substrates.Photoautotrophs Photoautotrophs （光能自养生物） （光能自养生物） Chemoautotrophs Chemoautotrophs （化能自养生物） （化能自养生物） • Because these organisms use light as their energy source, they are called photoautotrophs. • Chemoautotrophs are autotrophs that obtain their energy not from sunlight but from certain specific chemical reactions involving only inorganic substrates