Lichens

The lichens below are alliances between two very different organisms, fungi and green algae. The fungus collects water and minerals for both, and the algae make high-energy nutritients via photosynthese. To stay alive the fungus needs algae, but the algae are very well able to live without a fungal partner. Lichens grow very slowly, that’s why you find them mostly in places where they don’t need to compete with other plants. Like here on a branch of a tree, or on a rock, where other plants just can’t survive. In the air or in the surface of a rock they find enough minerals to grow, and they can stay for months without any water; in dry conditions their biological activity stops temporarily.



Lichens are classified according to their forms. A classification according to the combination of fungal and algal partners should be more appropriate, but many lichens are not yet well described, and maybe there exist more combinations of fungi and algae as we know. In the picture left a fruticose lichen, and down and right a foliose one.







Fragments of lichen, small clusters of fungus and algae, are blown away and start growing wherever they find circumstances to settle. This is the most common way to reproduce for a lichen. The fungus as well as the alga also has a way to reproduce while exchanging genetic material. The new fungus growing from the fungal spores has to find an algal partner to form a new lichen.