Which organisms are categorized as primary consumers?

Primary consumers are organisms that consume producers, which are typically plants, algae, or photosynthetic bacteria. Since primary consumers primarily feed on these autotrophs, they are most commonly herbivores. Herbivores obtain their energy directly from consuming plant material, making them the first step in a food chain after producers.

In contrast, carnivores feed on other animals and are categorized as secondary or tertiary consumers, depending on their position in the food chain. Omnivores, which eat both plants and animals, can occupy multiple roles in a food web but are not exclusively primary consumers. Decomposers, such as fungi and bacteria, play a crucial role in breaking down dead organic material and recycling nutrients back into the ecosystem, but they do not fall under the category of consumers that directly consume producers. Thus, herbivores are distinctly classified as primary consumers because of their role in feeding on plants and contributing to the flow of energy in an ecosystem.