Exploring the amazing world of lichens Lichenologist Manuela Dal Forno. Bottom photo: A reindeer lichen. (Alice Gerlach/NMNH)
Exploring the amazing world of lichens
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Lichens are a symbiotic relationship between algae and fungus. They have been on earth for millions of years, living on rocks, trees, and soil in all different habitats on all seven continents. Even though lichens are all around us, scientists are still learning about what they are, where they live, and how many different species of lichens there are.

Fungus is any group of spore-producing organisms feeding on organic matter, and include molds, yeast, mushrooms, and toadstools. 

Algae is a simple, non-flowering plant, which contain chlorophyll and produce sugar through photosynthesis, like other plants, but do not have true stems, roots, leaves, or vascular tissue like most other plants. Lichenization is a fungal lifestyle, and therefore the name of lichen is the name of the fungus component.

When you look at a lichen, what you’re looking at is the “house” that the fungus and algae grow together. Scientists call this house a “thallus.” When algae and fungus come together to form this house, we see a lichen. This partnership is called a symbiotic relationship, because it helps both the fungus and algae survive. Research has shown that lichens are not a natural biological group, meaning they do not all come from a single common ancestor, in other words, lichens have many origins. Currently there are almost 20,000 species of lichenized fungi known.

In this symbiotic relationship, the fungus and algae benefit from being associated with each other. The fungus provides the house, its shelter (the thallus). This shelter helps the algae survive in habitats where it would otherwise be exposed to the elements and possibly could not survive. The algae provide food for the fungus, in the form of sugar, which is a byproduct of photosynthesis that occurs within the algae.

Lichens are very important for the environment. They are an important food source for many animals, provide nest materials for birds, and provide habitat and material for biomimicry for insects and other organisms.

Lichens are also important for humans by providing natural dyes, perfumes, litmus paper, and even food. Humans even use lichens as bio-indicators, organisms that help humans monitor the health of the environment. Some species of lichens are sensitive to environmental pollution, so their presence or absence can help us understand more about the health of the environment, like air quality. 

Lichens produce over one thousand different chemical compounds, most of them unique to lichens. These compounds include acids and pigments. Some chemicals may even fluoresce under UV light, making them important components for lichen identification.

Lichens have DNA, which is used to identify lichen and compare relationships amongst and within species. DNA analysis has been an important tool for lichenologists in identifying and understanding the biodiversity of lichens.

Tune into the free Smithsonian Science How webcast, Exploring the Amazing World of Lichens, to meet Dr. Manuela Dal Forno. Through a live video stream and interactive polls and Q&A, Manu will take questions about lichens and her research. Sign up and tune in here: https://naturalhistory.si.edu/education/distance-learning/exploring-amazing-world-lichens-manuela-dal-forno

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CRITICAL THINKING QUESTION
What do you know about lichens? Where did you learn this fact?
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