It has often been said that “it’s a dog-eat-dog world out there”. However, upon closer inspection, it appears that many organisms work together to survive rather than competing with one another. This type of relationship is called “mutualism” because the organisms involved both play a role in helping each other survive and thrive.
A prime example of a mutualistic relationship is lichen. Lichens are a partnership between a fungus and an algae and sometimes a cyanobacteria. The fungus provides structural integrity to the lichen, creating a home for the algae, while the algae photosynthesizes to produce food for both itself and the fungus. Cyanobacteria, when present, fixes nitrogen, providing an important nutrient to the lichen system. Though species of algae and cyanobacteria have been found growing alone, the fungi species found in lichen are never seen without their counterparts. Some scientists postulate that lichens may be better characterized as a mini ecosystem rather than an organism. There are over 3,600 species of lichen in North America, and over 700 of them are right here in the north woods!
Hundreds of mutualistic relationships are present in nature. One can find ants protecting aphids from predators and receiving “honeydew”, a sweet liquid, from the aphids; plants such as clover and lupine that have mycorrhizal fungi growing in their roots which fix nitrogen for the plant; and bees pollinating plants, receiving nectar from their flowers in return. Humans have a mutualistic relationship too! The bacteria that call our intestines home help us digest our food. Perhaps Darwin didn’t have the whole story when he said that nature is based on “survival of the fittest”. Many organisms cooperate in order to survive.
Lichens of the North Woods by Joe Walewski