Fungi are one of the strangest of life's kingdoms. They are ubiquitous and very important to science and commerce. Fungi are responsible for everything from the creation of beer and cheese and life-saving pharmaceuticals such as penicillin. They are also the cause of deadly diseases like histoplasmosis and they can cause severe damage to crops and material goods.
Fungi may be more closely related to animals than plants. They are a taxonomical nightmare, however, because of their inherent variability. Along with this variability, which often entails multiple alleles for a single locus, other characteristics which make fungi special are:
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. Used with permission. For further information see the BioTech homenode.