General characters
1. Constitute a unique kingdom of heterotrophic organisms.
2. Show great diversity in morphology and habitat.
3. Some are parasitic while most are saprophytic(fed on dead organisms).
4. Except Yeasts(Unicellular), other are multicellular and filamentous.
5. The body consists of long, slender, thread like structures called hyphae and network of hyphae is known as mycelium.
6. Some hyphae are continuous and multinucleate known as coenocytic hyphae while others have septate(have cross wall).
7. Cell wall is composed of chitin and polysaccharides.
8. Shows symbiotic association with algae called lichen and with roots of higher plants known as mycorrhiza.
8. Vegetative reproduction takes place by fragmentation, fission, budding, Asexual by spores called conidia, zoospores, aplanospores, etc. and sexual reproduction takes place by forming oospores, ascospores and basidiospores.
9. Sexual reproduction involves fallowing.
a) Plasmogamy- Fusion of protoplasm of two gametes
b) Karyogamy- Fusion of two nuclei.
c) Meiosis in zygote results in haploid spores.
During sexual reproduction in fungus fusion of two haploid hyphae of compatible mating types takes place which may results in diploid cell(2n) in some fungi or an intervening dikaryotic phase(n+n) called dikaryon and a phase is called dikaryotic phase and formation of fruiting body and haploid spores are the formed by meiosis.
Classes of Fungi
a) Phycomycetes(Algal Fungi)
i. Found in aquatic as well as damp habitats.
ii. Some are obligate parasites on plants.
iii. Mycelium is aseptate and coenocytic.
iv. Asexual reproduction takes place by motile zoospores or non motile aplanospores.
v. Spores produced endogenously in sporangium.
vi. Zygospores formed by fusion of two gametes which may be isogamous, anisogamous or oogamous.
examples: Mucor, Rhizopus, Albugo
b) Ascomycetes
i. Commonly called as sac-fungi. They are unicellular(Yeast) or Multicellular.
ii. They are saprophytic, decomposers, parasitic or coprophilous(growing on dung).
iii. Mycelium-branched and septate.
iv. Asexual spores(conidia) produced exogenously on special mycelium called conidiophores.
v. Sexual spores(Ascospores) produced endogenously in sac-like asci, arranged in different types of fruiting bodies called ascocarps.
vi. Example: Aspergillus, Claviceps, Neurospora-used extensively in biochemical and genetic work and several members such as morels and truffles are edible(consider as delicacies).
Basidiomycetes
i. Commonly known members are mushrooms, puff balls, or bracket fungi.
ii. Grow in soil, on logs and tree stumps, or as plant parasites(rusts and smuts).
iii. Mycelium-branched and septate.
iv. Asexual spores absent and most common means of vegetative reproduction is fragmentation.
v. Sex organs absent, but plasmogamy takes place through fusion of vegetative cells of different strains. Resultant structure is a dikaryon, which give rise to basidium.
vi. Basidia are arranged in fruiting bodies called basidiocarps.
Examples: Agaricus (mushroom), Ustilago (smut), Puccinia(rust).
Deuteromycetes
i. Known as imperfect fungi because sexual phase is absent. On recognition of sexual phase, the member is shifted to either class Ascomycetes or class Basidiomycetes. They reproduce only by asexual spores(conidia).
ii. Mycelium is septate and branched.
iii. Some are saprophytic while others are parasitic. Being decomposers, they help in mineral recycling.
Examples: Trichoderma