A symbiosis occurs when two or more organisms of different species live together in an intimate, close and persistent association over time, which at least implies benefits for one of these species.

Lichens are symbiotic associations between fungi and algae or cyanobacteria that represent a very old way of life, born more than 190 million years ago.

Now you know that algae or cyanobacteria do not only live in aquatic environments!

With the help of fungi, which have a great capacity to accumulate moisture, lichens are protected against drying and solar radiation. Moreover, algae or cyanobacteria contribute their ability to perform photosynthesis, producing its own food to the fungus. These characteristics of photosynthetic fungi and algae or photosynthetic cyanobacteria in a single symbiotic organism make lichens very peculiar organisms exceptionally resistant to adverse environmental conditions and, therefore, able to colonize very diverse ecosystems.

To maintain this intimate relationship, the fungi penetrate into the cells of the algae by organs called haustoria. Through them, they take nutrients synthesized by the alga during photosynthesis. In this way, these organisms can colonize ecosystems with difficult living conditions such as rock surfaces or the woody stems of many trees.

If you look closely at this trail, you will see how a way of life based on the reciprocal collaboration between two species of organisms is much more frequent than you could initially think!