Only a few of these specific agents will be presented and discussed on this page. The fungi represent a diverse, heterogeneous group of eukaryotes. Most of these organisms are plant pathogens and relatively few cause disease in humans. In nature, fungi generally grow by secreting enzymes that digest tissues but some are actually predacious. In the vegetative phase, the cells are haploid and divide mitotically.
Most fungi exist as molds with hyphae but some fungi exist as unicellular yeast cells.
Some fungi can change their morphology and are termed dimorphic. In the reproductive phase, fungi may undergo either asexual or sexual reproduction. The fungi are classified based on the characteristics of their sexual phase. Zygomycota and Dikaryomycota. A third group of the fungi for which a sexual phase has not been observed is termed Deuteromycotina.