
A fungus is any of the eukaryotic creatures, which include the more common mushrooms and microbes like molds and yeasts. Together with Animalia, Plantae, Protista, Protozoa, and Chromista, these species are categorized as belonging to one of the traditional eukaryotic kingdoms.

While mushrooms and toadstools (poisonous mushrooms) are not the most common or commercially significant fungus, they are the most easily identified.
The Latin name for mushroom, fungus (plural fungi), has evolved to represent the entire group. Mycology is the study of fungi, derived from the Greek word "mykēs," which means mushroom.

Molds are occasionally used to refer to fungi other than mushrooms, however this name is more appropriate for fungi like bread mold.
Importance of Fungi
Fungi may be found in abundance—in the soil and air, in lakes, rivers, and oceans, on and among plants and animals, in food and clothes, and in the human body. Fungi, like bacteria, degrade organic matter and release carbon, oxygen, nitrogen, and phosphorus into the soil and environment.

Fungi are essential to many household and industrial processes, notably the making of bread, wine, beer, and certain cheeses.
Fungi are also utilized as food; for example, certain mushrooms, morels, and truffles are epicurean delicacies, and mycoproteins (fungal proteins) generated from the mycelia of specific species of fungi are used to manufacture protein-rich diets.
Form and Function of fungi
Size Range
Because of their size, mushrooms are clearly visible in fields and forests, and so were the only fungus known prior to the introduction of the microscope in the 17th century.
The most visible portion of a fungus is its fruiting body, also known as the sporophore. Sporophores differ significantly in size, shape, color, and lifespan. Some are minuscule and undetectable to the naked eye; others are as little as a pinhead; and still others are massive buildings.

Distribution and Abundance
Fungi are classified as terrestrial or aquatic, with the latter dwelling in freshwater or marine habitats. Freshwater organisms are frequently found in clean, chilly water since they do not survive high degrees of salt.

Fungi are present in all temperate and tropical parts of the earth where there is enough moisture for them to thrive. A few species of fungus thrive in the Arctic and Antarctic areas, although they are rare and are more frequently seen living in symbiosis with algae in the form of lichens.

Basic Morphology
A typical fungus consists of a mass of branching, tubular filaments surrounded by a stiff cell wall. The filaments, known as hyphae (single hypha), branch repeatedly into a complex, radially growing network known as the mycelium, which forms the thallus, or undifferentiated body, of the typical fungus.

The mycelium grows by absorbing nutrients from the environment and, once mature, generates reproductive cells known as spores, either directly or through specific fruiting structures.
The spores are released and spread by a number of passive or active means; once on an appropriate substrate, the spores germinate and generate hyphae, which expand, branch frequently, and constitute the next individual’s mycelium.

Structure of The Thallus
Almost all fungi have cell walls in their hyphae, which form the thallus. (True slime mold thalli lack cell walls, hence they are classified as protists rather than fungi.) A hypha is a multibranched tubular cell containing cytoplasm.

The tube itself might be continuous or separated into compartments or cells by cross walls known as septa (single septum). Nonseptate (coenocytic) hyphae have nuclei distributed throughout the cytoplasm.
Hyphae are often either nonseptate (as seen in more primitive fungus) or incompletely septate (with perforations). This allows cytoplasm to flow from one cell to another.

Sporophores and Spores
When a fungus’s mycelium reaches a certain stage of growth, it begins to produce spores, either directly on the somatic hyphae or, more commonly, on special sporiferous (spore-producing) hyphae, which can be loosely arranged or grouped into intricate structures known as fruiting bodies or sporophores.

Even though some of the most evolved fungus are aquatic in fresh or marine environments, they do not generate motile spores. Asexually generated spores (commonly called conidia) are produced exogenously in these fungi and often develop terminally or laterally on special spore-producing hyphae known as conidiophores.
Conidiophores can be found individually on the hyphae or in unique asexual fruiting bodies such as flask-shaped pycnidia, mattress-shaped acervuli, cushion-shaped sporodochia, or sheaf-like synnemata.
