A lichen is an organism that results from a mutualistic relationship between a fungus and a photosynthetic organism. The other organism is usually a cyanobacterium or green alga. The fungus grows around the bacterial or algal cells.
This is all i know about caves: Caves are large, natural holes beneath the surface of the earth. Underground passages and caves are found in rocky landscapes across the world. They are found in areas with a lot of limestone, a common type of rock. They can be created in various ways, but most caves are hollowed out of rock by water.
