Practice question

Continued consumption of finite prebiotic organics by chemoheterotrophs would exhaust hot dilute soup, creating selective pressure for alternative carbon acquisition. Chemoautotrophs developed pathways to fix carbon dioxide using inorganic electron donors like H2S, Fe2+ or H2, independent of organic supply. This innovation allowed colonization of environments lacking organics and preceded photoautotrophy. The transition illustrates metabolic evolution driven by resource limitation. Hence Depletion of organic matter represents adaptive response to diminishing organic resources. This concept integrates genetics, ecology and molecular evidence, frequently tested in NEET, GATE and CSIR-NET, highlighting links between genotype, phenotype and environment.