Question

Lichens are composed of two different organisms. Why can they live in places where the individual organisms cannot?

Answer 1

It is well established fact lichens having two components one is algae and other is fungi. Both are different organism but they have symbiotic relation. In this relation algae make food and nourish to fungi where as fungi will degrade the mineral at rocky area and provide to algae or cyanobacteria. Here fungi also provide cover the lichens and prevent the dehydration of algae. Some examples of lichens are Letharia vulpina(wolf lichen), Flavoparmelia caperata, Chrysothrix chlorina

It grows on extreme places such rock where no water and soil is available. Here algae will do the photosynthesis and fungi will collect mineral for it. Therefore they do not need any favoruable environmental conditions that propagate the lichens.