The primary characteristic of a producer in an ecosystem is its ability to create organic compounds through photosynthesis or chemosynthesis. Producers, such as plants and some microorganisms, transform inorganic substances (e.g., carbon dioxide and water) into energy-rich compounds, serving as the foundation of food webs. By converting solar energy into chemical energy, they support all other trophic levels, including herbivores and carnivores. This role is crucial for sustaining life on Earth and maintaining ecosystem productivity.