Kingdom Fungi: Features, Structure, and Reproduction

Kingdom Fungi has a huge diversity of organisms that are neither plants nor animals. Examples of these distinctive multicellular eukaryotes include mushrooms and yeast, which causes our bread to rise and ferments our beer and wine. 

• There are tens of thousands of different species of fungi on Earth, according to scientists. 
• Fungi were once supposed to be simply early forms of plants, according to one theory.
• It is more appropriately known as the "Kingdom of Multicellular Decomposers." 
• It has eukaryotic multicellular (or multinuclear), spore-producing, and non-chlorophyllous forms.

Key Terms: Fungi, Spores, Hyphae, Yeast, Vegetative, Mycelium, Lichen, Multicellular, Reproduction.

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Features of Fungi 

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Some general characteristics or features of fungi are as follows.

• They are eukaryotic organisms that are predominantly multicellular. 
• There is a cell wall, however, it is made of chitin. There is no cellulose. 
• Absolutely no chlorophyll is present. 
• There is no tissue differentiation.
• They could be parasites or saprophytes. 
• Glycogen is a reserve food. 
• Some algae and fungi can create symbiotic relationships. Such a group is referred to as "Lichen." 
• Mycelium, the term for the filamentous part of fungi, is their body. Hyphae are the individual filaments. 
• Either the hyphae have several cells or multiple nuclei. Coenocytic condition is another name for the multinucleate condition. 
• Reproduction can have a sexual or asexual form.

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Structure of Fungi and Their Nature of Growth

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The structure of fungi includes mycelium, hyphae and filaments. A detailed description of the structure is as follows.

• Each mycelium is produced by a spore, which then gives rise to a hypha, which exhibits apical growth (it branches near the tip). 
• Mycelium then continues to grow and spread over the substratum and expand its areas of absorption. 
• All fungi, with the exception of yeast, have bodies made up of this mass of loosely woven filaments, known as hyphae.
• Hyphae may grow in two characteristic manners- 

1. Hyphae spread out naturally to create a loose, tangled mass. The cells can be easily separated from one another. Prosenchyma mycelium is one such kind. 
2. Some hyphae develop in highly compact masses by growing in close proximity to one another. The cells are difficult to separate. Pseudoparenchyma is the term for such a mass.

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Nutrition in Fungi

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Since none of the fungi contains chlorophyll, they are all heterotrophic. The nutrients are taken in by the cell from the environment in an absorptive type of nourishment. 

1. Parasitic Fungi

Other living things provide the food for these fungi. The majority of parasitic fungi inflict harmful diseases on plants and animals. The numerous outgrowths that parasitic fungi frequently produce penetrate the host's body deeply and feed there. These extensions are known as haustoria.

2. Saprophytic Fungi

Dead and decomposing organic waste serves as the feeding source for these fungi. Because they act as "decomposers," these are crucial for the environment. They contribute to material recycling by breaking down organic waste into inorganic chemicals.

3. Symbiotic Fungi

For mutual advantage, certain fungi coexist with other types of life. Symbiosis is a relationship that is mutually beneficial to both partners. In the form of lichen and mycorrhizae, fungi have a similar relationship with algae and the roots of higher plants.

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Reproduction in Fungi

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Fungi reproduce by vegetative, asexual and sexual reproduction methods. 

1. Vegetative reproduction

This process involves separating a piece of the main plant body, which then grows into fresh mycelium. Typically, it happens through rhizomorphs, sclerotia, fission, and fragmentation. Yeast typically exhibits budding.

2. Asexual reproduction

The production of asexual spores is the key step in this process. However, these spores do not combine. Both gamete production and fertilization are absent. 

Asexual spores are formed by mitotic division and are of the following main types-

1. Zoospores: These spores as they bear flagella for locomotion. These develop into specialized structures called sporangium. 
2. Aplanospores: These are also developed in the sporangium, but these are non-motile. They do not have any flagellum. The spores developed in sporangium are also developed in sporangium are called sporangiospores. 
3. Conidia: These are also non-motile spores but these do not develop inside the sporangium. The spores develop freely, on conidiospores. 

3. Sexual reproduction in fungi

In fungi, specialized spores are used for sexual reproduction. Common names for these are oospores (in Phycomycetes), ascospores (in ascomycetes), and basidiospores. (in basidiomycetes).

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Classification of Fungi

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The classification of fungi has been based on a number of factors, including morphology, spore kinds, reproductive methods, and life cycle types. The different types of reproduction patterns and life cycles form the foundation of the classification.

Important features of different classes of fungi 

1. Phycomycetes

Phycomycetes class of fungi involves below mentioned features.

• It is known as zygomycetes. 
• Aquatic areas are home to Phycomycetes. In moist and humid areas, some members are observed growing on rotting wood. 
• Septate and coenocytic describe the mycelium. 
• Zoospores are used in asexual reproduction.
• Zygospores aid in sexual reproduction. Two gametes fuse to generate a zygospore. So, zygospores have a diploid structure. 
• Mucor, Rhizopus, and Albugo are a few examples that are frequently used.

2. Ascomycetes

Ascomycetes are the fungi that are also called sac-fungi.

• They are multicellular, with the exception of a small number of individuals, like yeast. 
• Although they primarily disintegrate, certain varieties are parasitic or coprophilous (growing on dung). 
• The mycelium has septa and is branching. 
• Conidia formed exogenously on the unique mycelium known as conidiospores are what are known as asexual spores. 
• Ascospores, unique spores, are used in sexual reproduction. 
• Examples. Aspergillus, Claviceps, and Neurospora. 
• As a tool for genetic and biochemical study, Neurospora is crucial. 

3. Basidiomycetes 

Basidiomycetes possess some common features as mentioned below 

• Puffballs, bracket fungi, and mushrooms are some common names for them. 
• In moist soil, on logs, and in tree stumps, they primarily grow as saprophytes. However, a lot of them, like rusts and smuts, are parasites in higher plants. 
• Branching and septa are present in the mycelium. 
• Examples include Puccinia (rust fungus), Ustilago (smut) and Agaricus (mushrooms).
• Amanitamuscaria, sometimes known as the "death angel," is a very dangerous fungus. A mushroom.

4. Deuteromycetes

This class of fungi is known as imperfect fungi as they lack sexual reproduction

• These fungi are only known in their asexual or vegetative states. 
• The perfect (sexual) stages of Deuteromycetes members are unknown. 
• While many of the members are decomposers and aid in mineral cycling, some are saprophytes or parasites. 
• These mushrooms can only procreate asexually using spores called conidia.
• Trichoderma, Colletotrichum, and Alternaria are a few examples.

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Things to Remember

• Kingdom fungi are also called the Kingdom of multicellular decomposers.
• The hyphae are either multicellular or multinucleated. 
• The cell wall is present but it contains chitin. Cellulose is absent.
• In all fungi, there are two distinct phases in the life cycle. 
• In the vegetative phase, there is a rapid absorption of nutrients from the surroundings and the growth of branches. 
• During the reproduction phase, hyphae grow aerial and form various types of fruiting structures and reproduction cells (spores and gametes). 
• Spores help in the propagation of the species and its spread to the new substratum.