gogol

The second major group of multicellular organisms, the kingdom Fungi, is usefully discussed now, since it too arose in all probability from the protistan protophyta. But whereas the Metaphyta arose from photosynthetic forms, the Fungi arose from non-synthetic ancestors. The Fungi are eukaryotic and predominantly multicellular decomposers, with diverse types of organization.

The bodies of these organisms are sometimes unicellular, but more often organized into filaments. Each filament is called a hypha; collectively, they make up a mycelium. The mycelium, which may be highly branching, extends into the environment that nourishes the fungus. Typically, as decomposers, the fungi live in moist areas where there is an abundance of organic material. Hence their occurrence in dead wood or the litter on forest floors. But they also invade animal tissues--athlete's foot is caused by a fungus. They are severe problems in terms of food spoilage, since they cause molding of breads and vegetables, but they are also helpful in food production, especially in beer brewing and wine making, which depend on the fermentation of yeasts, and in certain cheeses. The colored patches in blue cheese are the result of fungal growth. In brief, fungi grow just about anywhere there is organic material that can be decomposed. Decomposition occurs through the release of enzymes that degrade substrates in the immediate vicinity of the hypha. These substrates are macromolecular constituents produced by other organisms because such molecules contain necessary building blocks for further growth of the fungi. Proteins supply amino acids, nucleic acids nucleotides, and carbohydrates and lipids sugars and other carbon compounds. These smaller molecules are assimilated into the fungal cells and used there for vegetative growth.

Reproductive functions involve sexual reproduction as well as asexual spore-formation. Although the reproductive structures of the familiar puffballs, mushrooms, toadstools, and brackets of shelf fungi are rather complex structures, they constitute the lesser part of fungal growth. The usually invisible mycelium comprises the mass of the organism and is quite simply organized. Only in the reproductive structures does complexity approach that seen in the thalli of the red or the brown algae, for example.