How Fungi
Get Their Food

One difference between fungi and most plants noticed by backyard naturalists is that fungi don't photosynthesize -- they don't contain green chlorophyll so they don't use sunlight to produce carbohydrate, their food, by combining carbon dioxide with water. Fungi take their food from their environment in the following ways:

• From dead things, in which case they are known as saprophytes. In the woods, mushrooms growing on dead, decaying tree-trunks lying on the ground are saprophytes.

• From  other living things, with whom the fungus lives in a long-lasting or  permanent, very close association  (symbiosis). The following symbiotic relationships are possible:

• When the fungus hurts the living thing in or on which it lives, it is known as a parasite in a parasitic relationship. If you ever got an ear fungus or athlete's feet, you had a fungal parasite.

• When the living thing on which or in which the fungus lives is neither hurt nor helped by the fungus, the relationship is referred to as one of commensalism. Some fungi living harmlessly in the guts of animals are commensals.

• When the living thing on which or in which the fungus lives is helped by the fungus' presence, so that both parties benefit from the arrangement, the relationship is referred to as mutualism. One extremely important example of mutualism is that of the fungus-root combination known as mycorrhiza.

While microscopic fungi may absorb dissolved nutrients from their surroundings directly through their cell walls, nutrients generally enter larger fungi by soaking into -- or diffusing into -- cobwebby strands of root-like hyphae growing through the substrate (dead thing or living thing, such as soil or leaf  litter). You can see what hyphae look like here.