Category: 06. Fungi

Since the 1990s, dramatic changes have occurred in the classification of fungi. Improved understanding of relationships of fungi traditionally placed in the phyla Chytridiomycota and Zygomycota has resulted in the dissolution of outmoded taxons and the generation of new taxons. The Chytridiomycota is retained but in a restricted sense. One of Chytridiomycota’s traditional orders, the Blastocladiales, has been raised […]

Fungi have ancient origins, with evidence indicating they likely first appeared about one billion years ago, though the fossil record of fungi is scanty. Fungal hyphae evident within the tissues of the oldest plant fossils confirm that fungi are an extremely ancient group. Indeed, some of the oldest terrestrial plantlike fossils known, called Prototaxites, which were common in […]

Although the fungal symbionts of many lichens have fruiting structures on or within their thalli and may release numerous spores that develop into fungi, indirect evidence suggests that natural unions of fungi and algae occur only rarely among some lichen groups, if indeed they occur at all. In addition, free-living potential phycobionts are not widely distributed; for example, despite repeated searches, […]

A lichen is an association between one or two fungus species and an alga or cyanobacterium (blue-green alga) that results in a form distinct from the symbionts. Although lichens appear to be single plantlike organisms, under a microscope the associations are seen to consist of millions of cells of algae (called the phycobiont) woven into a matrix formed of the filaments of the fungi (called the mycobiont). […]

Relatively little is known of the effects of the environment on the distribution of fungi that utilize dead organic material as food (i.e., saprobic fungi; see above Nutrition). The availability of organic food is certainly one of the factors controlling such distribution. A great number of fungi appear able to utilize most types of organic materials, such as lignin, cellulose, or other polysaccharides, which have been added to […]

In the life cycle of a sexually reproducing fungus, a haploid phase alternates with a diploid phase. The haploid phase ends with nuclear fusion, and the diploid phase begins with the formation of the zygote (the diploid cell resulting from fusion of two haploid sex cells). Meiosis (reduction division) restores the haploid number of chromosomes and […]

Sexual reproduction, an important source of genetic variability, allows the fungus to adapt to new environments. The process of sexual reproduction among the fungi is in many ways unique. Whereas nuclear division in other eukaryotes, such as animals, plants, and protists, involves the dissolution and re-formation of the nuclear membrane, in fungi the nuclear membrane remains intact throughout the […]

Typically in asexual reproduction, a single individual gives rise to a genetic duplicate of the progenitor without a genetic contribution from another individual. Perhaps the simplest method of reproduction of fungi is by fragmentation of the thallus, the body of a fungus. Some yeasts, which are single-celled fungi, reproduce by simple cell division, or fission, in which one cell undergoes nuclear […]

Following a period of intensive growth, fungi enter a reproductive phase by forming and releasing vast quantities of spores. Spores are usually single cells produced by fragmentation of the mycelium or within specialized structures (sporangia, gametangia, sporophores, etc.). Spores may be produced either directly by asexual methods or indirectly by sexual reproduction. Sexual reproduction in fungi, as in other living organisms, […]

A number of fungi have developed ingenious mechanisms for trapping microorganisms such as amoebas, roundworms (nematodes), and rotifers. After the prey is captured, the fungus uses hyphae to penetrate and quickly destroy the prey. Many of these fungi secrete adhesive substances over the surface of their hyphae, causing a passing animal that touches any portion of the mycelium to adhere firmly to the […]