The fungi is a group of eukaryotic, multicellular and filamentous organisms, which include yeasts and moulds. They are classified as a kingdom. They are heterotrophic organisms that cannot produce their own food and depend on other organisms for their nutritional requirements.
The unique characteristic of the group that differentiates them from bacteria and other protists is that their cell wall is made up of chitin. The organisms that cannot photosynthesise are called fungi meaning organisms that depend on other organisms for their food. About 144,000 species of the organisms are known. They are found abundantly on Earth and are of great ecological and medicinal importance.
- Like eukaryotic organisms, they have a membrane-bound nucleus with chromosomes and DNA. They also have membrane-bound organelles, such as mitochondria and ribosomes.
- They share similarities with animals in lacking chloroplasts and being heterotrophic organisms.
- Like plants, they have a cell wall and a vacuole. They reproduce both sexually and asexually.
- They grow as a tubular, filamentous and elongated structure known as hyphae. Hyphae are multinucleated and grow from their tips. This type of growth is also seen in oomycetes.
- Like many plants and animals, some fungal species also show bioluminescence.
- Some fungi grow as unicellular yeasts that reproduce by budding and fission. They exist as dimorphic fungi that can switch between the yeast phase and mould phase in response to environmental conditions.
- The fungi are unique organisms that possess a cell wall made up of a chitin-glucan complex. Though chitin is found in arthropods, and glucan is found in plants, it is only fungi that have a combined complex of these two molecules.
- Asexual reproduction: In fungi, the asexual mode of reproduction takes place with the help of vegetative spores called conidia. Another means of reproduction is through mycelial fragmentation. Mycelial fragmentation takes place when the mycelia break into small pieces, and each piece grows into a new mycelium.
- Sexual reproduction: The fungal mating system can be heterothallic (mating between two opposite species) or homothallic (mating between two similar species). Ascospores and basidiospores are sexual spores that are formed for reproduction. A fungi goes through both haploid and diploid species in its life cycle.
- Spore dispersal: Both sexual and asexual spores are dispersed by wind. Such spores are often hydrophobic and do not absorb water, and are easily transported by raindrops.
Fungi forms multiple symbiotic relationships with other organisms such as lichen and mycorrhiza. Lichen meaning an association between fungi and algae, where the fungi depends on algae for food and nourishment, and algae reside on the fungi. Mycorrhizae are symbiotic relationships between fungi and roots of higher plants, where the fungi depends on roots for nourishment and in turn, fungi helps in better nutrient absorption to the roots.
- Penicillin, an antibiotic, has been extracted from the fungi Penicillium chrysogenum that is used against syphilis, meningitis and throat infections. Other fungal antibiotics include cyclosporine and lovastatin.
- Saccharomyces cerevisiae, better known as baker’s yeast, is used to make bread and alcoholic beverages.
- A wide variety of mushrooms, such as Agaricus bisporus, Pleurotus ostreatus and Lentinula edodes are consumed by humans as edible mushrooms.
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