Which of the following is NOT a primary producer?

Primary producers are organisms that can produce their own food through the process of photosynthesis or chemosynthesis, converting inorganic substances into organic matter. They form the base of the food web and are essential for energy flow in ecosystems.

Cyanobacteria, algae, and photosynthetic plants are all examples of primary producers because they possess chlorophyll or other pigments that enable them to capture sunlight and convert it into energy through photosynthesis. This process allows them to produce organic compounds, which serve as food for other organisms.

In contrast, herbivores, as mentioned in the question, are not primary producers. They are consumers that rely on primary producers for their energy and nutrients by feeding on them. By consuming plants or algae, herbivores obtain the organic compounds that primary producers create. Thus, distinguishing herbivores as non-producers highlights their role in the food web as consumers rather than producers in the energy flow of ecosystems.