Question

how did the fungus supply water, shelter,and minerals to alga

Answer 1

here is your answer this association is called symbiotic relationship

Symbiosis in lichens is the mutually helpful symbiotic relationship of green algae and/or blue-green algae (cyanobacteria) living among filaments of a fungus, forming lichen. The algae or cyanobacteria benefit their fungalpartner by producing organic carbon compounds through photosynthesis

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