The critical role of primary producers in a food chain is to convert sunlight into usable energy through photosynthesis. These autotrophic organisms, such as plants and algae, form the foundation of the food web by generating organic material that serves as food for primary consumers (herbivores). By capturing solar energy and producing biomass, primary producers drive energy flow and nutrient cycling in ecosystems. Their health directly impacts all higher trophic levels, emphasizing their essential contribution to ecological balance.