What Type of Organism is fungi?
Fungi show a great diversity in morphology and habitat. Fungi are heterotrophic organisms, they obtain their nutrients by absorption. The cell wall of fungi are mostly made up of carbohydrate chitin, while the cell wall in plants is made of cellulose. The carbohydrates stored in fungi is in the form of glycogen. The 'fruit' body of fungus is only seen, while the living body of the fungus is a mycelium, it is made of tiny filaments called hyphae. The mycelium is hidden., Nutrition in fungi is by absorbing nutrients from the organic material in which they live. Fungi do not have stomachs, they digest their food before it pass through the cell wall into the hyphae. The hyphae secrets enzymes and acids that break down the organic material into simple compounds.General characteristics of fungi are as follows:
- Fungi are eukaryotic organisms.
- They are non-vascular organisms.
- They reproduce by means of spores.
- Depending on the species and conditions both sexual and asexual spores may be produced.
- They are typically non-motile.
- Fungi exhibit the phenomenon of alteration of generation.
- The vegetative body of the fungi may be unicellular or composed of microscopic threads called hyphae.
- The structure of cell wall is similar to plants but chemically the fungi cell wall are composed of chitin.
- Fungi are heterotrophic organisms.
- They fungi digest the food first and then ingest the food, to accomplish this the fungi produce exoenzymes.
- Fungi store their food as starch.
- Biosynthesis of chitin occurs in fungi.
- The nuclei of the fungi is very small.
- During mitosis the nuclear envelope is not dissolved.
- Nutrition in fungi - they are saprophytes, or parasites or symbionts.
- Reproduction in fungi is both by sexual and asexual means. Sexual state is referred to as teleomorph, asexual state is referred to as anamorph.
Division Ascomycota: Sac Fungi
The sac-fungi produce spores in small cup-shaped sacs called asci, hence the name ascomycota. The mature sac fungi spores are known as ascospores, they are released at the tip of the ascus breaks open. Yeast is the most common one-celled fungi. Yeast reproduces through asexual process called budding. The buds form at the side of the parent cell, they pinch-off and grow into new yeast cell which is identical to the parent cell. Examples of sac-fungi are morels, truffles, cup fungi and powdery mildews. Example: Aspergillus, Claviceps, Neurospora.
Division Basidiomycota: Club Fungi Basidiomycota includes the mushrooms, puff-balls, smuts, rusts and toadstools. The spores are borne on a club-shaped spore case called basidium. In mushrooms the basidia are lined at the gills under the cap. Huge numbers of spores are produced by the club fungi. In fact, an average sized mushroom produces over 16 billion spores. These spores rarely germinate or mature. Example: Agaricus(mushroom), Ustilago(smut), and Puccinia(rust fungus).
Division Zygomycota: Zygote forming Fungi
These fungi are usually found on cheese, bread, and other decaying food. They are zygote forming fungi, hence the name zygomycota. The spores are produced in round-shaped case called sporangium. The grayish fuzz seen on bread and decaying food is actually mass of mature sporangia mold. Under the microscope they are seen as pinheads. When the sporangium breaks open hundreds of spores are released. Example: Mucor, Rhizopus (the bread mould) and Albugo.
Division Deuteromycota: Imperfect Fungi
These organisms are known as imperfect fungi because they lack sexual reproduction. They reproduce by asexual spores known as conidia. Most of the fungi causes diseases to humans like ringworm, athlete's foot. Economically important imperfect fungi are Penicillium and Aspergillus. Other examples are Alternaria, Colletotrichum and Trichoderma.
Sac-fungi : Agaricus (mushroom), Ustilago (smut), and Puccinia (rust fungus).
Zygote-forming fungi : Mucor, Rhizopus (the bread mould) and Albugo.
Club fungi: Agaricus (mushroom), Ustilago (smut), and Puccinia (rust fungus).
Imperfect fungi: Alternaria, Colletotrichum and Trichoderma.
Mycorrhizae - More than 90% of the plants are symbionts of mycorrhizae. Myco means fungus and rhiza means root. Mycorrhizae are of two types ectomycorrhizae and endomycorrhizae.
Ectomycorrhizae - These are fungus forms sheath outside the root.Endomycorrhizae - They are also known as vesicular-arbuscular-mycorrhizae (VAM). Fungus does not form sheath around the roots.
Lichens - They are symbionts. They have a symbiotic relationship between a fungus and a alga. Neither of the organisms can survive on their own.
Economic Importance of FungiFungi are important in a variety of ways:
Recycling - Together with bacteria the fungi form a major role in recycling the dead and decayed matter.
Food - Many mushrooms are used as food by humans. Mushrooms species are edible and are cultured in many parts of the world for sale.
Medicines - Penicillin antibiotic is derived from a common fungi Penicillium. Many other fungi also produces antibiotics, which are used to control diseases in humans and animals.
Bio-control Agents - Fungi are used to parasitise insects which help control pests. Spores of fungi are sprayed on crops, this method is cheaper and environmentally friendly.
Plant and Animal Diseases - Many fungi live on and in plants and animals causing diseases. They also co-exist harmoniously with plants and animals.
Food spoilage - Fungi play a major role in recycling organic material. Fungal damage is responsible for large losses of stored food usually when the food contains moisture.