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B. How do Fungi Differ from Other Organisms?

Living organisms on our planet are divided into different kingdoms. Until fifty years ago, only two major kingdoms were recognized, the Plant Kingdom and Animal Kingdom. After a half-century of studies on the morphology, physiology, biochemistry, ultrastructure, and molecular nature of organisms, several kingdoms are now recognized. Many current biology books recognize 5 basic kingdoms of living organisms, the Monera (bacteria), Protoctista (protozoa), Plantae (plants), Animalia (animals) and Mycota (fungi). In 1988, scientists on three different continents discovered independently, using rDNA, that the fungi emerged very early from the animal kingdom not from plants as was traditionally assumed. We will look at how the fungi differ from four other kingdoms currently recognized.

  The kingdoms of organisms are further divided into the following categories:


Phyla or Divisions 






 The scientific name of a species is a binomial, consisting of the generic name and the species name. Thus, the common mushroom is Agaricus bisporus; (Agaricus = the generic name and bisporus = the species name).

Fungi differ from bacteria (the Kingdom Monera)  in that bacteria do not have organized nuclei or other membrane-bound organelles (i.e., they are prokaryotes). Bacterial cell walls do not contain chitin and glucans (Fig. 1-16).

Fig. 1-16. A dividing bacterium with developing cell wall.

Some bacteria, like all fungi, are heterotrophic (they can not manufacture their own food). Other bacteria, the Cyanobacteria, or what once were called the blue-green algae, have chlorophyll and are able to manufacture their food (autotrophic). They are the common green “scum” on bodies of water. Bacteria may be spiraled, cylindric, or globose.  


Fungi differ from the Protozoa (Kingdom Protoctista) in that protozoan groups are haploid or diploid, heterotrophic or autotrophic, most engulf their food (phagocytosis), and when flagellate, they have two or more flagella (01-34). This large kingdom contains about 35 phyla, three of which are very similar to fungi because their thalli (structures without roots, stems, or leaves) and zoospores resemble those of fungi, and they live in the same habitats with fungi. Current molecular studies suggest that this large group of phyla probably represents a number of different kingdoms.

Fungi differ from the Stamenopilids (Kingdom Stamenopila), a group that looks morphologically very similar to fungi, in  that Stamenopilids reproduce by means of biflagellate zoospores with a long whiplash flagellum and a shorter tinsel flagellum. Their vegetative mycelioid phase is  diploid, i.e. having a 2N number of chromosomes within the nucleus, and their walls are composed of cellulose and glucans. They have oogamous sexual reproduction and a pattern of steroid synthesis similar to plants. One large class of Stamenopilids, the Oomycetes, has been placed until recent years among the fungi and will be considered in more detail when we look at fungal-like organisms. Although they look like fungi, they differ in having biflagellate zoospores, diploid mycelium, cellulose in their walls, and sexually produced oospores.

Unlike fungi,  plants (Kingdom Plantae) are composed of diploid cells (except the gametes in pollen and ovules), their cell walls contain cellulose and pectin (plus other compounds), and they are autotrophic (i.e. they can manufacture their own food through the process of photosynthesis). Plants range from one-celled algae to multicelled giant redwoods, and include mosses, liverworts, ferns, and seed plants. Seed plants include small herbaceous ones to large palms, pines, oaks, and others. Lichens are organisms that have fungi and algae growing together in a mutual relationship.

Fungi differ from animals (Kingdom Animalia) in that the cells of animals are without walls, the body cells are diploid (only gametes are haploid), and animals engulf their food (and boy, do some of us engulf our food!). Animals may be cellular, or larger multicelled like the corals and snails, worms and fish, turtles and frogs, or birds and mammals.