Lichens are complex life forms representing a symbiotic partnership between a fungus and an alga (or cyanobacterium).
This fascinating relationship works as follows:
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The Fungus (Mycobiont): The dominant partner. It provides the lichen's overall structure (called the thallus) and shape. It also absorbs water and nutrients from the environment. The fungus dictates the lichen's characteristics, including its form and reproductive structures (fruiting bodies).
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The Alga or Cyanobacterium (Photobiont): Performs photosynthesis, creating food (sugars) for both itself and the fungus. Cyanobacteria can also fix nitrogen from the atmosphere, providing a vital nutrient, particularly in nutrient-poor environments.
Think of it as a miniature ecosystem where the fungus provides a home and gathers resources, while the alga or cyanobacterium provides the food. This allows lichens to survive in harsh environments where neither organism could survive alone, such as bare rock, tree bark, and even Arctic tundra. Lichens are incredibly diverse, coming in various colors, shapes (crustose, foliose, fruticose), and sizes.
