Fungi were grouped with plants by early taxonomists. While the two kingdoms do, of course, share some superficial similarities, modern analysis has since shown them to be incredibly different.
Plants and fungi appear to have a lot in common. The casual human observer may see little to distinguish them – they grow and die in roughly the same place, with any movement indiscernible to the naked eye. Indeed, mushrooms, moulds and yeasts were initially lumped in the same taxonomic category as plants.
Fungi were essentially considered anomalous plants until 1969, when ecologist Robert Whitaker classified them as their own kingdom because they subsist on decaying matter – unlike plants, which produce their own food; and animals, which consume other organisms.
Plants contain chloroplasts, organelles that are derived from an ancient event in which cyanobacteria came to reside in a previously heterotrophic cell, allowing it to produce its own food through photosynthesis.
Fungi, however, digest decaying matter by secreting enzymes and absorbing the resulting nutrients.
Plants and fungi are different in other ways as well. Fungi are actually much more closely related to animals than to plants – they share a common ancestor dating to around a billion years ago. Fungal cell walls contain chitin, which is present in the cell walls of some animals too.
Plant cell walls, however, maintain their rigidity using cellulose.
For all their differences, though, some plants and fungi have teamed up. A majority of terrestrial plants form helpful partnerships with mycorrhizal fungi. The plants provide the fungi with sugars and the fungi provide the plants with other nutrients taken from the soil.
