Get Their Food
One difference between fungi and plants usually found in backyards 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:
- When the fungus steals something like water or nutrients from the living thing it's living on or inside of, it's 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.