I be lichen it!
Different species of lichen growing on fence boards. One of the strangest relationships on the planet Earth exists between an alga and a fungus. Together they exhibit obligate mutualism - a form of symbiosis where each partner of the relationship has to be together to survive. There are some 15,000 to 20,000 species of lichen across the planet. The word species is a bit odd in this circumstance as there are actually 2 distinct species making up the single entity. For the most part, the fungus is a unicellular variety belonging to the Ascomycetes, the same group that yeast belongs to. The photosynthetic component of the equation often is a form of green algae, although it may also be a member of the cyanobacteria. Both forms benefit from the presence of the other. The fungus receives sugars from photosynthesis done by the algal component. The fungal component provides moisture, other nutrients, and protection for the algae. Although lichens...