A primary consumer is an organism that feeds on primary producers, which are plants or algae. They are also called herbivores, and they make up the second trophic level in a food chain. Primary consumers are usually small in size and there are many of them. They can range from microscopic organisms such as zooplankton to animals as big as elephants. Several other feeding strategies are also used by primary consumers, such as algivores that feed on photosynthetic algae, frugivores that feed on the fruiting bodies of plants, nectarivores that feed on plant nectar, folivores that feed on leaf material, granivores that feed on grains and seeds, and fungivores that feed on heterotrophic fungi such as mushrooms. Primary consumers often have specific physiological adaptations that allow them to process the carbohydrates produced through photosynthesis, which can be hard to break down and extract nutrition from. Herbivores often have rows of wide, flat teeth that are used to rasp, grind, and tear tough plant material and woody stems. Many primary consumers also have symbiotic bacteria, which live within a special organ called the cecum and assist with the digestion of plant material.