Primary producers are organisms that create their own food through photosynthesis or chemosynthesis. They form the base of the food chain and are essential for the survival of other living organisms. Common examples include plants, algae, and some bacteria, which convert sunlight or chemical energy into organic matter. These producers play a crucial role in ecosystems by providing energy and nutrients to herbivores, which are then consumed by carnivores. Without primary producers, the entire food web would collapse, as they are the starting point for energy flow in environments like forests, oceans, and grasslands.