A Little Bit More
Although we’re surrounded by lichens, most of us haven’t paid much attention to these demure organisms. I say “organism” because a lichen really isn’t a plant, bacterium, or a fungus, it’s made up of two of these. Lichens are a symbiotic relationship (one or both participants benefit by living together) between an alga or bacterium and a fungus. Most of the bulk of a lichen is made up of fungal filaments but living among those filaments is either a green alga or a blue-green bacterium.
Believe it or not it was Beatrix Potter, the author who wrote about Peter Rabbit, who first proposed the idea that lichens were actually two organisms in one. Lichens are true pioneers; able to establish themselves on rocky surfaces in some of the most barren and inhospitable places in the world. Reindeer (European) and caribou (North American) feed heavily on lichens and even have a special digestive enzyme to help them extract adequate nutrition from these organisms.
The fungal part of a lichen produces an acid that can actually weather rock and thus create the beginnings of soil. As pioneers, lichens create a surface upon which other organisms can use to establish their own habitat. Lichens depend upon rainwater for essential minerals that they absorb directly but this also means they’re especially vulnerable to airborne pollutants. In many areas around the world, as air-borne pollutants have risen, especially in the cities, local lichen population have plummeted.
Activities
Lichen Hunt
Objectives: Close Look at Lichens
Materials: Hand lens, Lichens from surrounding areas
Although lichens grow all around us (except in areas where they’ve been killed off by pollution) few of us have ever noticed them or given them a thought. This is a chance for students to see what lichens they can find in their own schoolyard, park or backyard. Although your students may not have access to a backyard, most can access a nearby park or natural area. Actually, if pollution isn’t too bad, lichens can be found growing in all kinds of places, including may urban and suburban areas.
1. Have your students take a look at the links I’ve provided so they have a better sense what lichens look like. Remember, there are many, many different kinds and they come in an assortment of colors and shapes.
2. Once students have familiarized themselves with some of the possibilities, ask them to look around your school, trees and rocks at the park or on their way home and/or in their own backyard to see if they can find some lichens. They don’t need to find much – any little group will do. Students will be most likely to find lichens at the base of trees (old trees are best), or on rocks that have been lying around undisturbed for some time. Older is better simply because it takes time for lichens to grow into a large enough cluster to be obvious – remember, they’re slow growers.
3. Once they’ve found what they think are lichens, have them bring a small sample into the class in a sandwich bag. You don’t need much to see and there’s a good chance that your sample won’t live very long anyway.
4. You can place the lichen samples in a protected area where they can be spritzed with water (rainwater is best) periodically. You will note that when they are spritzed, they may show brighter color and may even plump up as they absorb water.
5. Use a hand lens or magnifying glass to help the students get a better look at their lichens. You may even want them to draw/paint them too.
6. No matter how much TLC you provide your lichens, my guess is that most, if not all, will gradually succumb. The environment in your classroom just won’t be right for them and they’ll slowly wither and die. But, you’ll have had an opportunity to see an organism that is rarely noticed despite the fact that it is right before your eyes!
Key Concepts
Identification, Environmental Issues, Adaptations and Diversity
Questions
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Posted by Rick Schumacher on July 24, 2006 at 07:12 PM
Q: We recently build a new house by a large formation of rock (slate) that is covered with lichens. Many of the rocks were covered with dirt etc (the remain of the construction). After removing the dirt I find most of the lichens are gone. Is there any way to reintroduce them back to the rocks and get them to grow again? Thanks, Rick
A: You're a man after my own heart - I too would want my lichens back!
The dirt has probably killed the algae (no light available) and therefore the entire alga/fungus symbiotic organism we know as lichens. If at least some lichens are present on the rocks my guess is that they'll recolonize but I know of no way to do it yourself. Guess I'd be sure that the rocks are clean of any soil so spores can get a good hold on the rock and begin growing. This isn't going to be an overnight process, lichens grow slowly, but over the next few years, you should be able to see the lichens spread. Best of luck to you and your lichens. Thanks for asking.