What is a symbiotic relationship between fungus and alga in a lichen?

A symbiotic relationship between fungus and alga in a lichen involves the mutualistic interaction where the fungus provides structure, protection, and moisture retention for the alga, while the alga conducts photosynthesis to produce food (sugars) that the fungus can utilize. This partnership allows lichens to thrive in harsh environments where neither organism could survive alone. The combination enhances nutrient acquisition and resilience, showcasing a unique example of cooperation in nature.