CLASS 11 CHAPTER 2 BIOLOGICAL CLASSIFICATION Part 2 I KINGDOM FUNGI They are a unique kingdom of heterotrophic organisms They are cosmopolitan i e they are present everywhere They grow in warm and humid places White spots on mustard leaves are due to a parasitic fungus Eg Bread Mould Orange Rots Mushroom Toadstools etc Fungi are used for multiple purposes They are a source of antibiotics and some unicellular fungi are used to make bread and beer products Eg Penincillium used to make Penicillin Yeast used to make bread and beer Other fungi cause diseases in plants and animals Eg wheat rust causing Puccinia called hyphae types Except yeasts fungi are filamentous Fungi bodies are made up of long slender thread like structures Fungi possess a network of hyphae called mycelium and are of two o Coenocytic Hyphae They are continuous tubes filled with multinucleated cytoplasm o Septate Hyphae They are tubes having septae or cross walls Remember septum the wall separating the chambers of the heart Fungal cell wall is made up of chitin and polysaccahrides Chitin is a long chain polymer of N acetylglucosamine Fungi are heterotrophs and follow various modes of heterotrophic nutrition o Fungi are primarily saprophytic i e they absorb soluble organic matter from dead and decaying matter o Some are parasitic i e they derive their nutrition from living organisms by converting them into their host for nutrition o Some fungi live in symbiotic associations they survive through co dependency with other living organisms with the organisms usually providing nutrition to the fungi and the fungi in return providing protection and mineral and water supply to the organism Fungi adhering to symbiotic associations for nutrition are symbionts Eg Lichen symbiotic association between algae and fungi and Mycorrhiza s symbiotic association with plant roots of higher plants Vegetative Propagation Reproduction Asexual Reproduction by asexual spores Sexual Reproduction by Sexual spores Fragmentation Fission Budding Conidia Sporangiospores zoospores Oospores Ascopsores Basidiospores i VEGETATIVE PROPAGATION Fragmentation a Process by which fungi reproduces by mycelial fragmentation i e the mycelium breaks up into individual fragments each mycelial fragment capable of growing into a separate mycelium and later on fungi Eg Molds yeasts and mushrooms Fission b Process by which one cell undergoes nuclear division and splits into two daughter cells After some growth these cells continuously divide and eventually population of cells forms and into a fungi c Process by which a bud develops on the parent fungi with the cytoplasm of the parent unifying with the bud and upon full development it separates from the fungi Budding ii ASEXUAL REPRODUCTION a Conidia It is a type of asexual reproductive spore usually produced at the tip or side of hyphae or on special spore producing structures called conidiophores Each conidiophore contains millions of conidia that detach from them when mature Large ones are called macroconidia and small ones are called microconidia b Sporangiospores They are the spores encapsulated or stored in a sporangium a specialized cell that forms stores and nourishes sporangiospores until they are fully mature and bursts open when the sporangiospores within them fully mature and are ready for reproduction Sporangium can vary in shape from an elliptical sphere or ellipsoidal or complete sphere or globose This type of asexual reproduction is seen in the fungal groups of Chytridiomycetes and Zygomycetes It is also seen in the Oomycetes which is a group of fungi that is phylogenetically unrelated to the true fungi c Zoospores A zoospore is an asexual spore arising from a zoosporangium when mature that is flagellated and motile They are naked incapable of dividing do not possess any walls and utilize their endogenous food reserve for nourishment and energy Usually found in fungi near water bodies and shed their flagella when they encyst germinate to form fungi and forms a wall iii SEXUAL REPRODUCTION Sexual Reproduction in fungi involving the formation of fruiting bodies and thereby causing the release of ascopores oospores or basidiospores Ascospores Found in clusters of four or eight spores within a single mother cell called the ascus Sometimes enclosed in a gelatinous sheath or within a sac Oospores Result of sexual reproduction in the oomycote and zygomycota Formed in the oogonium Survival structures in the soil Basidiospores A sexual spore formed by fungi basidiomycetes Reproduced sexually with the formation of club shaped and cells knows as basidia which usually carry external meiospores Spore development occurs in basidia Sexual spore formed by fungi ascomycetes A diploid zygote formed by the fusion of male and female gamete In fungi sexual reproduction involves three crucial steps 1 Plasmogamy It is the fusion of the protoplasms cytoplasm nucleoplasm of 2 motile or non motile gametes It s the first step of sexual reproduction 2 Karyogamy It s the fusion of the nuclei of the two gametes It s the second step of sexual reproduction 3 Meiosis It s the last step of sexual reproduction and involves the meiotic division of the zygote due to which spores are formed In sexual reproduction 2 haploid hyphae fuse together In some cases the fusion of haploid cells cause the formation diploid 2n cells immediately Dikaryophase It is a phase in fungi that causes a momentary pause due to the intervention of a dikaryon a cell in which two nuclei from either parent share a single cytoplasm for a certain period of time or up until conditions are favourable in between plasmogamy and karyogamy in fungi Later the nuclei of the parents fuse and become diploid Fungi form fruiting bodies in which reduction division occurs leading to formation of haploid spores By mycelium morphology mode of spore formation and nutrition fungi can be classified into four categories 1 PHYCOMYCETES o Found in aquatic habitats on decaying wood in moist and damp places or as obligate parasites parasites that are completely dependent on the host for its survival o They have aseptate and coenocytic mycelium continuous network of hyphae without any separating walls o Reproduce via zoospores motile or aplanospores non motile They are produced in the sporangium endogenously o Sexual reproduction between male and female gametes are of three types namely i Isogamous Fusion of two gametes that are same in size ii Anisogamous Fusion of two gametes that are