Kingdom Fungi

Fungi differ from other organisms in structure, reproduction, and in methods of obtaining nutrients. Fungi are eukaryotic, nonphotosynthetic organisms, and most are multicellular heterotrophs. Most fungi are microscopic molds or yeasts. Molds, such as the fungus that grows on bread and oranges, are tangled masses of filaments of cells. Yeasts are unicellular organisms whose colonies resemble those of bacteria.

Filaments of fungi are called hyphae. The cell walls of hyphae contain chitin, a complex polysaccharide. The study of fungi is called mycology.

Most fungi are saprophytic, that is, they live on organic compounds that they absorb from dead organisms in the environment. This characteristic makes fungi a very important recycler of organic material in nature.

General Fungi Life Cycle

Zygomycota Life Cycle (Conjugation)

The first fungi were probably unicellular organisms that might have clung together after mitosis to form a long filament of cells. All modern phyla of fungi had evolved by about 300 million years ago.

PHYLUM ZYGOMYCOTA Pilobolus on horse dung Rhizopus

PHYLUM BASIDIOMYCOTA Club fungus

PHYLUM ASCOMYCOTA sac fungi distinguished by saclike compartments

Organization Fungi are eukaryotic, non-photosynthetic organisms. Most are multicellular heterotrophs. Most fungi are microscopic molds or yeasts. Yeasts are unicellular organisms.

Most fungi reproduce both sexually and asexually. Asexually, fungi produce thousands of genetically identical haploid spores, usually on modified cells of the hyphae. Asexual reproduction may also occur by fragmentation. In this process, a hypha dries and shatters, releasing individual cells that act as spores. The fungus that causes athlete’s foot reproduces this way. Reproduction

Yeast reproduce by a process called budding. Budding is an asexual process in which part of a yeast cell pinches itself off to produce a small offspring cell.

Many but not all species of fungi are also able to reproduce sexually. Fungi are neither male nor female. They occur in mating types that are sometimes called “minus” and “plus.” When two different mating types of the same species encounter one another, the hyphae of one mating type fuse with the hyphae of the opposite mating type. The ability of some fungi to reproduce both sexually and asexually provides an adaptive advantage.

Habitat Grows on bread and foods like oranges. Armillaria lives underground and occupies a space of up to eight hectares (861,000 ft2). Most fungi are saprophytic. Tree trunks or dead animals. Found primarily in soil. Fungi may infect the skin, hair, nails, and tissues of the body.

Structure and Function Fungi have no sensory system. Fungi secrete digestive enzymes and then absorb the digested nutrients. Like animals, fungi store energy in the form of glycogen.

SUPPORT The cell walls of fungi cells contain chitin, a complex polysaccharide not found in bacteria, protists, or other microorganisms but found in insects. The presence of chitin distinguishes cell walls of fungi from those of plants.

Lichens A lichen is a symbiosis. That means that it is two or more organisms living together such that both are more successful within the partnership than they would have been if they were living on their own. With lichens the basic components of this partnership are 1) a fungus called the 'mycobiont' and 2) one or more algae and/or a cyanobacteria called the 'photobiont'.