Which of the following is a primary producer in an ecosystem?

In an ecosystem, primary producers are organisms that can produce their own food through photosynthesis or chemosynthesis, forming the base of the food chain. Plants are classified as primary producers because they utilize sunlight, water, and carbon dioxide to create glucose and oxygen through the process of photosynthesis. This ability allows them to convert solar energy into chemical energy, which then becomes available to other organisms in the ecosystem.

Herbivores and carnivores, on the other hand, are consumers. Herbivores obtain their energy by feeding on primary producers, while carnivores feed on other consumers. Fungi, while crucial to decomposition and nutrient cycling, do not produce their own food and thus do not fit into the category of primary producers. Therefore, plants are the correct answer as they fulfill the role of primary producers in an ecosystem.