Fungi are found in all types of environments where organic materials are available. For examples, water, air, dead and decaying organic matter, living organisms.
Some fungi are unicellular. The thallus of the fungi is long and tubular with filamentous branches called as hyphae. Hyphae are aseptate, coenocytic, uni-, di- or multinucleate.
The mass of interwoven hyphae is called mycelium. Mycelium may be unicellular or multicellular.
The cells of fungi have definite cell wall mainly made up of chitin. Chitin is a nitrogenous material containing polysaccharide. Other components of the fungal cell wall may be cellulose-glycogen, cellulose-glucan (found in oomycetes), Cellulose-chitin, chitin-chitosan (found in zygomycetes), Chitin-glucan (found in ascomycetes and basidiomycetes) etc.
Fungi are eukaryotic and they do not have plastids. As fungi do not have chlorophyll, they cannot perform photosynthesis. They obtain their nourishment from the environment by extracellular digestion and absorption of digested food material. So they are known as heterotrophs.
Fungi live as saprophytes on dead and decaying organic matter, as parasites on/inside living organisms. Some fungi grow in symbiotic relationship with algae and form lichens. Some of the fungi grow in close association with the roots of the vascular plants forming mycorrhizae.
The reserve food material of the fungi is glycogen, fats or lipid globules.
Fungi reproduce vegetatively by fragmentation, budding and fission.
During favorable conditions, they reproduce asexually by spores. The asexual spores are called sporangiospores and conidia. The sporangiospores may be zoospores or aplanospores. Zoospores are flagellated spores with one or two flagella. Aplanospores are non-flagellated spores.
Sexual reproduction in fungi is through gametes and is carried out with the help of planogametic copulation, gametangial contact, gametangial copulation, spermatization or somatogamy.
Fungi show progressive reduction of sexuality
Fungi exhibit asexual haplontic, haplontic-dikaryotic, haplo-diplontic or diplontic life cycle.