Symbionts are organisms that live in close association with another species, often benefiting from the relationship. This interaction can be mutualistic, where both species gain advantages, or parasitic, where one benefits at the expense of the other. Examples of symbionts include bacteria in the human gut that help with digestion and lichens, which are formed from a partnership between fungi and algae. In ecosystems, symbionts play crucial roles in nutrient cycling and energy flow. For instance, mycorrhizal fungi form symbiotic relationships with plant roots, enhancing nutrient uptake. Understanding symbionts is essential for studying biodiversity and ecosystem health, as they contribute to the balance of natural environments.