Dating countryside people
They can survive in extremely cold areas such as on high mountains and in regions such as the arctic.
They may be virtually the only plant form surviving in some of these areas and can be vitally important sources of food for animals.
The algal cells, through the process of photosynthesis, provide the fungus with some of the organic nutrients which it needs.
In lichens where the partner is a species of is able to fix atmospheric nitrogen.
Lichens present a very intriguing problem for people whose job is to name different kinds of organisms.
This is because a lichen is not a separate organism in the sense of being one type of individual.
In return, the water, nutrients and gases absorbed from the environment by the fungus are shared with the algae.
Approximately 18,000 species of lichen have been described and identified worldwide.
Alternatively, it may be a type of relationship called a 'symbiosis' where both partners benefit.
Whatever the exact nature of the relationship, it undoubtedly results in an 'organism' which is capable of surviving in places where neither the fungal partner, nor the algal one, could survive on their own. The simplest lichens are crusts of loosley mixed fungal hyphae and algae.
The same fungus can also form different lichens depending on the type of alga which it associates with.
Most lichens contain only one kind of alga, but some may contain two.
The individual bits are called soredia and they contain both the fungus and the algal partner together.