Chemosynthetic autotrophs derive energy by 

Chemosynthetic autotrophs obtain energy by oxidising inorganic compounds such as hydrogen sulphide (H₂S), ammonia (NH₃), hydrogen gas (H₂), ferrous iron (Fe²⁺), and methane (CH₄). They are typically found in environments where sunlight is scarce or absent, such as deep-sea hydrothermal vents, caves, and some terrestrial habitats like acidic soils.