Lichen

This is a photo of tree-dwelling lichen on tree bark. This represents the biological term lichen. Lichen is a complex life form that consists of a symbiotic association of algae or cyanobacteria and fungi. The fungi is the dominant partner that gives lichen the majority of its characteristics such as its shape. The algae also gives lichen some characteristics such as its blue or green color. Lichen is mostly found on tree bark, exposed rock, and part of biological soil crust. The composite body of the lichen is called the thallus and is anchored by hairlike structures called rhizines. Lichen that is crustlike and tightly held to its substrate are called crustose. The lichen shown in the picture is an example of crustose due to its crustlike and thin appearance. Large and leafy lichen are referred to as foliose lichen. As mentioned earlier, the lichen is a symbiotic association between algae or cyanobacteria and fungi. This symbiotic relationship is called mutalism, where the algae and fungi benefit from each other. The algae form carbohydrates that once excreted, the fungi absorbs and uses to make another carbohydrate. Fungi contribute by absorbing water from the air and providing shade for the light sensitive algae below it.

Britannica, The Editors of Encyclopaedia. “Lichen.” Encyclopædia 

        Britannica, Encyclopædia Britannica, Inc., 4 Feb. 2018, www.britannica.com/science/lichen.

“What Are Lichens?” US Forest Service, www.fs.fed.us/wildflowers/beauty/lichens/whatare.shtml.