Fungi are a kingdom of living organisms that includes molds, mushrooms, and yeasts. They are eukaryotic, heterotrophic organisms that lack chlorophyll and must obtain nutrients by absorbing them from other living sources of biomass. There are over 400,000 known species of fungi, most of which are saprophytic, living off of dead and decaying matter. About 8% are plant pathogens and 0.5% are pathogens of humans and other animals. Fungi play an important ecological role in decomposition and nutrient cycling. They exhibit a variety of morphologies and life cycles and can be found in nearly every habitat on Earth.