- Fungi are heterotrophic organisms.
- Fungi are filamentous, with the exception of unicellular yeasts.
- Fungi consist of long, slender thread-like structures called
- The network of hyphae is known as mycelium.
- Some hyphae are continuous tubes filled with multinucleated cytoplasm, these are called coenocytic hyphae and others have septae or cross walls in their hyphae.
- The cell walls of fungi are composed of chitin and polysaccharides.
- Most fungi are heterotrophic and absorb soluble organic matter from dead substrates and hence are called
- The fungi that depend on living plants and animals are called
- Fungi can also live as symbionts –. Example- in association with algae as lichens and with roots of higher plants as
- Reproduction in fungi can take place
- By vegetative means - fragmentation, fission and budding.
- Asexual reproduction is by spores called conidia or sporangiospores or
- Sexual reproduction is by oospores, ascospores and
- The sexual cycle involves the following three steps
- Fusion of protoplasms between two motile or non-motile gametes called
- Fusion of two nuclei called
- Meiosis in zygote resulting in haploid spores.
- The fusion of two haploid cells immediately results in diploid cells (2n), but in some fungi such as ascomycetes and basidiomycetes, an intervening dikaryotic stage (n + n i.e. two nuclei per cell) occurs; such a condition is called a dikaryon and the phase is called dikaryophase of fungus.
- Later, the parental nuclei fuse and the cells become diploid.
- The fungi form fruiting bodies in which reduction division occurs, leading to formation of haploid spores.
- Kingdom fungi is divided into various classes based on the morphology of the mycelium, mode of spore formation and fruiting bodies such as
- Members of phycomycetes are found in aquatic habitats and on decaying wood in moist and damp places or as obligate parasites on plant.
- The mycelium is aseptate and coenocytic.
- Asexual reproduction takes place by zoospores or by aplanospores and asexual reproduction takes place by
- If the gametes are similar in morphology, these are called as isogamous or if dissimilar, they are known as anisogamous or
Example- Mucor, Rhizopus.
- The ascomycetes are unicellular or multicellular.
- Commonly known as sac-fungi.
- They are saprophytic, decomposers, parasitic or coprophilous.
- Mycelium is branched and septate.
- The asexual spores are conidia produced on conidiophores.
- Sexual spores are called ascospores which are produced endogenously in sac like asci arranged in different types of fruiting bodies called ascocarps .
Example- Aspergillus , Claviceps and Neurospora.
- Commonly known forms of basidiomycetes are mushrooms, bracket fungi.
- They grow in soil, on logs and tree stumps or as parasite.
- The mycelium is branched and septate.
- Vegetative reproduction takes place by fragmentation.
- The sex organs are absent, but plasmogamy is brought about by fusion of two vegetative or somatic cells of different strains which gives rise to basidium arranged in fruiting bodies called
- Karyogamy and meiosis take place in the basidium producing four basidiospores.
Example- Agaricus (mushroom), Puccinia (rust fungus).
- Commonly known as imperfect fungi because only the asexual or vegetative phases of these fungi are known.
- The deuteromycetes reproduce only by asexual spores known as conidia.
- The mycelium is septate and branched.
- Some are saprophytes or parasites while a large number of them are decomposers of litter and help in mineral cycling.
Examples- Alternaria, Colletotrichum and Trichoderma.