Lichens
Lichens are a mutualism formed between fungi and algae. Most of the fungi in this symbiotic relationship are not able to survive without an algal partner. This is because plants can make their own glucose through photosynthesis. This is very useful for the fungal part of the lichen, since it needs this glucose to survive.The fungus stores these sugars, sending out chemicals to help them diffuse through the cell walls of the algae. Algae can live in many different environments and extend its range significantly by coexisting with the fungus.