The Lichens: Where Fungi Mix with Algae Help
Introduction to The Lichens: Where Fungi Mix with Algae
Another unusual group closely related to the fungi are the lichens ( LIE -kens). This term derives from ancient Greek and originally meant, “that which licks or eats around itself.” Lichens are mixtures of fungi with either algae or bluish-green bacteria, living together in symbiosis, such that each type of organism benefits.
Because they contain photosynthetic algae that produce chlorophyll, lichens may look like greenish moss growing on a rock or tree trunk. Lichens are not green plants or really any other type of single organism. Lichens are constructed somewhat like a tough, stale, blueberry pie containing two different types of organisms (Figure 8.6). Like a pie, there is a protective upper and lower crust of slender, tightly packed hyphae (the fungus partner). As in the fruiting body (cap and stem) of a mushroom, the middle of the lichen consists of a mycelium – a loose network of highly branched, thread-like hyphae. Finally, like thousands of blueberries baked into a pie, small round algae are inserted into the meshwork of the fungus mycelium.
This relationship is symbiotic ( sim -beye- AHT -ik) because the fungal crusts are tough enough to protect the contained algae from extremes of climate and temperature. The fungus also releases enzymes that partially digest rock or other hard surfaces, allowing nutrients to be absorbed by the lichen. In return, the algae produce additional energy for their fungal partners by carrying out photosynthesis. Thus, lichens make an extremely tough duo of cooperating organisms that, working together, can survive in some of the harshest habitats on planet Earth. Brave hikers can see them tightly clinging to rocks at the tops of frozen mountains, or even thriving in the empty wasteland of Antarctica!
Practice problems for these concepts can be found at: The Fungi: Not Just Mushrooms Test