UPSC NDA II 2015 General Ability Paper

Concept:Autotrophic organisms produce their own food using light energy and inorganic sources.Explanation:Autotrophs, like green plants and algae, contain chloroplasts that capture sunlight.They perform photosynthesis to convert carbon dioxide ($\mathrm{CO}_2$) and water ($\mathrm{H}_2\mathrm{O}$) into carbohydrates (such as glucose).This process stores light energy as chemical energy in the bonds of organic molecules.The carbohydrates serve as both a carbon source (to build biomass) and an energy source (via respiration).Thus, photosynthesis directly fulfills the carbon and energy needs of autotrophs.Other options: Gluconeogenesis is the synthesis of glucose from non‑carbohydrate precursors; glycogenesis is the synthesis of glycogen from glucose; external sources refer to obtaining carbon and energy from other organisms.These processes are not the primary means for autotrophs to meet their carbon and energy requirements.Autotrophs are the primary producers in ecosystems, forming the base of the food chain.Answer:Photosynthesis