Fungi

The two types of hyphae are:

1. Septate hyphae - have dividers between the cells called septa.
2. Non-septate hyphae (also known as aseptate or coenocytic hyphae) - form one long cell with many nuclei.

Most fungi live on dead matter or in soil. Some fungi also live in or on other organisms in symbiotic relationships.

The body of a fungus is called a mycelium, which is made up of a mass of hyphae.

Most fungi reproduce asexually by producing spores, which are haploid cells produced by mitosis from a haploid parent cell.

Sexual reproduction in fungi involves mating between two haploid hyphae that fuse to form a diploid spore called a zygospore.

The class Basidiomycota, known as the Club Fungi, includes mushrooms, puffballs, and shelf fungi. It is distinguished by the presence of a basidium, a club-shaped reproductive organ, which originates as a binucleate, dikaryotic structure and serves as a site for karyogamy and meiosis.

In Basidiomycota, haploid spores grow into tangles of hyphae called mycelia. These mycelia usually grow under the surface until they meet another mycelium, at which point they join through plasmogamy, producing binucleate, dikaryotic hyphae that form the fruiting body or basidia.

In Basidiomycota, basidia are lined with nuclei that fuse to form a diploid zygote. Following this, meiosis occurs, producing basidiospores that, when released, grow into hyphae.

The underside of a mushroom cap contains gills, which are lined with basidia where nuclear fusion occurs to form a diploid zygote.

Basidiomycota reproduce asexually by either budding or asexual spore formation. Budding occurs when an outgrowth of the parent cell is separated into a new cell, while asexual spore formation takes place at the ends of specialized structures called conidiophores.

The sexual reproductive structure in Ascomycota is known as the ascus.

During sexual reproduction in Ascomycota:

1. The + (female) hyphae bears a reproductive structure called ascogonium.
2. The – (male) hyphae bears a male reproductive structure called antheridium.
3. A tube grows from the female reproductive structure to the male reproductive structure.
4. The negative nuclei move into the female organ but do not fertilize with positive nuclei.
5. A hyphae grows from the female organ, resulting in binucleate hyphae (containing both +ive and -ive nuclei).
6. The terminal ends of the binucleate hyphae elongate, and their nuclei unite to form a zygote nuclei.
7. The zygote divides meiotically, producing 4 haploid spores.
8. These spores divide by mitosis to produce 8 small spores called ascospores, which are found in an ascus.

Ascomycota produce two types of reproductive structures: conidiophores for asexual reproduction and ascus for sexual reproduction.

Budding occurs when a small portion of the cytoplasm of the parent cell becomes separated into a small daughter cell. When yeast of opposite mating types meet, the cells fuse (plasmogamy), followed by the fusion of their nuclei (karyogamy), allowing diploid cells to reproduce more by budding.

The identifying characteristics of Zygomycota include the formation of a zygospores during sexual reproduction and the formation of aseptate hyphae (no cross walls) except in reproductive structures.

The three types of hyphae in Zygomycota are:

1. Rhizoids - reach below the surface and function in food absorption.
2. Sporangiophores - above the surface and bear the spore-producing sporangia.
3. Stolon - above the surface and connects groups of rhizoids and sporangiophores.

In sexual reproduction, when hyphae from positive and negative strains meet, they produce structures called progametangia that are dense and multinucleate. Cell walls form to separate the tips of the progametangia into gametangia. Plasmogamy then occurs between the two gametangia to form a zygote.

Karyogamy is the fusion of two nuclei and it takes place within the zygote during the sexual reproduction of fungi.

Initially, the cell walls of the zygote are thin, but they later thicken to form a zygospore.

Germination begins when the diploid nucleus undergoes meiosis and a sporangium develops.

Fungi can cause sicknesses and diseases in animals (e.g., ringworm), spoil food, fruits, and vegetables, and are responsible for diseases like taro leaf blight.

Yeast is used in bakery to make baked products, in cheese making, and in brewery industries for making alcohol.

Fungi act as decomposers, enhancing soil fertility by breaking down organic matter.

The fungus of the genus Penicillium is used in making penicillin and other antibiotics, and is important in dairy industries for making certain types of cheese.

Mycorrhizae are symbiotic relationships formed between the mycelium of club fungi and plant roots, enhancing nutrient and water absorption for the plants.

Fungi are divided into three main classes according to the mode of reproduction of the species.

Yeast belongs to the division of Ascomycota.

Yeast reproduces asexually through a process called budding, where a new cell forms off the side of the parent cell.