Eventually, the guest cells became the organelles of a new kind of cell. Partnerships between cells once foreign and even enemies to each other are at the very roots of our being. They provide one of the first and most powerful examples of evolutionary adaptation by symbiosis. In the new taxonomy, the fungi, estimated at 100,000 species, are given their own kingdom. While their cells are eukaryotic, they have a fundamentally different life-cycle and ecological adaptation than plants or animals.
Plants produce, animals consume, and fungi absorb.
They absorb minerals and other nutrients directly through their membrane, and also transport complex chemicals out to plants with which they are in symbiotic association. An example is the mycorrhizal association between many species of fungi and the roots of trees and shrubs, which are fundamental to the ecological viability of forests. Many kinds of fungi obtain nutrition as parasites or as decomposers. Molds and yeasts are used in the production of cheese and beer, and antibiotics such as penicillin are fungal in origin. This is the basic autotrophic food-producing process of the biosphere.