Summary
A mutualistic partnership between a fungus and an alga or cyanobacterium.
In depth
The fungus (mycobiont) provides structure and protection; the alga or cyanobacterium (photobiont) provides sugars. Lichens colonise bare rock and are pioneers in succession; they are sensitive to air pollution, so act as bioindicators.
Lichens grow slowly and can live for centuries. They absorb pollutants directly, so are air quality indicators. Growth forms: crustose, foliose, fruticose.
Key idea: a lichen is a partnership, not one organism.
Lichens are classified by form: crustose (crust-like), foliose (leafy) and fruticose (shrubby). They grow slowly (often under 1 mm per year), live for centuries and survive extreme conditions by drying out. They produce acids that weather rock. Reproduction is by soredia or isidia, small packets containing both partners, or by fungal spores that must find a new alga.
They are sensitive to sulfur dioxide, so lichen diversity serves as an indicator of air quality. They provide food for reindeer, dyes (litmus) and nesting materials. Some include a third partner, a yeast, in the cortex.
Example: Xanthoria on tree bark and walls is easily seen as bright orange patches.
Frequently asked questions
What is Lichens?
A mutualistic partnership between a fungus and an alga or cyanobacterium.
Which area of biology covers Lichens, and how advanced is it?
Lichens is one of the 54 topics in Microbiology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Fungal Reproduction, Fermentation, Endospores.
Can you give an example of Lichens?
Reindeer moss is a lichen eaten by caribou.
What should I learn before Lichens?
Work through the Beginner topics in Microbiology first, such as Microorganisms, Bacteria, Archaea, then return to Lichens. Intermediate topics assume the Beginner vocabulary.
What topics are related to Lichens?
The closest topics to Lichens are Fungal Reproduction, Fermentation, Endospores, Fungi. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Lichens?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Lichens. To practise the whole of Microbiology, use the Microbiology quiz.
How is Lichens different from Fungal Reproduction?
Lichens: A mutualistic partnership between a fungus and an alga or cyanobacterium. Fungal Reproduction: Fungi reproduce by spores, sexually or asexually, dispersed through the air. Read both side by side and note what each one explains.
How should I study Lichens step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Fungal Reproduction and explain the difference aloud. Finally, take the Microbiology quiz and come back to this page for any question you miss.