Given the importance of this topic from competitive examinations like SSC CGL, UPSC in this article, we would look at kingdom Fungi and its characteristics.
1. The fungi constitute a unique kingdom of heterotrophic organisms. They show a great diversity in morphology and habitat.
a. Cell type: Eukaryotic
b. Cell wall: present
c. Nuclear membrane: present
d. Mode of nutrition: Heterotrophic
2. The body of fungi consists of long, thin thread-like structures called hyphae (yeasts as an exception which are unicellular with a filamentous body). The network of hyphae is known as mycelium.
3. Some hyphae are continuous tubes filled with multinucleated cytoplasm called coenocytic hyphae. Cell walls are made up of chitin and polysaccharides (a carbohydrate, for example-starch, cellulose, or glycogen whose molecules consist of many sugar molecules bonded together).
4. Most fungi are saprophytic in nature i.e. feed on organic matter from the dead substrate while others that depend on living plants and animals are known as parasites.
5. Few fungi have a symbiotic relationship (beneficial to both partners involved) with algae, for e.g. Lichens and those who are in association with roots of higher plants e.g. Mycorrhiza
6. Reproduction in fungi can take place by vegetative means – fragmentation, fission and budding. Asexual reproduction takes place with the help of spores (microscopic particles that grow into fungi in favourable conditions). These spores are known as conidia/ zoospores/ sporangiospores.
7. Sexual reproduction takes place by oospores, ascospores and basidiospores. The sexual cycle involves three steps called plasmogamy (fusion of protoplasts), karyogamy (fusion of nuclei) and meiosis.
8. The morphology of the mycelium, mode of spore formation and fruiting bodies divide the kingdom into various classes viz Phycomycetes, Ascomycetes, Basidiomycetes and Deuteromycetes.
9. Phycomycetes:
a. Found in aquatic habitat, decaying wood and moist and damp places.
b. Asexual reproduction takes place by zoospores (motile) or by (non-motile).
c. Some examples include Mucor, Rhizopus (the bread mould mentioned earlier) and Albugo (parasitic fungi on mustard).
10. Ascomycetes:
a. Popularly known as sac-fungi, these are multicellular (Penicillium) while rarely are unicellular (yeast).
b. These fungi are saprophytic, decomposers, parasitic or coprophilous (grow on dung).
c. Some examples are Aspergillus, Claviceps and Neurospora (used extensively in biochemical and genetic work). Examples of this class like morels and truffles are edible.
11. Basidiomycetes:
a. Mushrooms, bracket fungi or puffballs are some examples of this class.
b. They grow in soil, on logs and tree stumps and in living plant bodies as parasites, e.g., rusts and smuts.
c. E.g. Agaricus (mushroom), Ustilago (smut) and Puccinia (rust fungi) are few members of Basidiomycetes.
11. Deuteromycetes:
a. Known as imperfect fungi since the only known phases of this fungi are asexual and vegetative.
b. Some members of this class are saprophytes or parasites, while a large number of them are decomposers of litter and contribute to mineral cycling.
c. Some examples are Alternaria, Colletotrichum and Trichoderma.
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