Autotroph

Autotroph means ‘self-feeders’. Organisms that produce complex organic compounds or foods using carbon from simple substances such as CO₂ generally using energy from light (photosynthesis) or inorganic chemical reactions (chemosynthesis) are known as autotrophs. Plants, algae, and some bacteria harvest light energy through photosynthesis. These organisms, along with a few others that use chemical reactions as energy source (chemosynthesis), are called autotrophs. In photosynthesis, autotrophs form carbohydrates from CO₂ and a source of hydrogen (such as H₂O) in the chlorophyll-containing cells exposed to light. Thus, the photosynthesizes feed themselves and the entire living world. Chemosynthesis is performed by some rare autotrophs living in extreme environments like hydrothermal vents, cold seeps, whale falls, and wood falls in deep seas. They make food using energy from chemical reactions, often combining H₂S or CH₄ with O₂. For example, bacteria living in active volcanoes near hydrothermal springs punctuating deep seafloors oxidize S or H₂S to produce their food. All food chains start with some autotrophs. Besides, the efficiency of a food chain depends on the energy first consumed by the primary producers, ie, autotrophs. [Mohammad Zashim Uddin]