Oh goodness There is a fungus among us!!!!!!What is a fungus? A eukaryotic, heterotrophic organism devoid of chlorophyll that obtains its nutrients by absorption, and reproduces by spores.
Characteristics1. All are eukaryotic Possess membrane-bound nuclei (containing chromosomes) and a range of membrane-bound cytoplasmic organelles (e.g. mitochondria, vacuoles, endoplasmic reticulum). 2. Most are filamentous Composed of individual microscopic filaments called hyphae, which exhibit apical growth and which branch to form a network of hyphae called a mycelium. 3. Some are unicellular e.g. yeasts. 4. Protoplasm of a hypha or cell is surrounded by a rigid wall Composed primarily of chitin and glucans, although the walls of some species contain cellulose. 5. Many reproduce both sexually and asexually Both sexual and asexual reproduction often result in the production of spores. 6. Their nuclei are typically haploid and hyphal compartments are often multinucleate Although the Oomycota and some yeasts possess diploid nuclei. 7. All are achlorophyllous They lack chlorophyll pigments and are incapable of photosynthesis. 8. All are chemoheterotrophic (chemo-organotrophic) They utilise pre-existing organic sources of carbon in their environment and the energy from chemical reactions to sythesise the organic compounds they require for growth and energy. 9. Possess characteristic range of storage compounds e.g. trehalose, glycogen, sugar alcohols and lipids. 10. May be free-living or may form intimate relationships with other organisms i.e. may be free-living, parasitic or mutualistic (symbiotic). Modes of nutrition Fungi=absorptive heterotrophs Animals=phagotrophic heterotrophHeterotroph (chemo-organotrophs):an organism incapable of synthesizing carbohydrates from inorganic sources; requires preformed organic compounds produced by other organisms Plants=autotrophsHyphae (singular, hypha) Cylindrical, branching filaments composed of a tubular cell wall filled with cytoplasm and organelles Most fungal hyphae are 2-10 m diameter
SeptaSeptaregular cross-walls formed in hyphae. Hyphae with septa are septate, those lacking septa are aseptate or coenocytic. primary septa are formed as a process of hyphal extension and generally have a septal pore, which allows for cytoplasmic and organelle movement.Secondary or adventitious septa are imperforate, formed to wall off ageing parts of the mycelium.
Kingdom FungiChytridiomycotalack true hyphae pretty diverseZygomycotacoenocytic hyphaeZygote fungi terrestrial and fast growingBread mold (Rhizopus)Glomeromycotacoenocytic hyphaemycorrhizae sympiotic relationship between roots of plant and fungusAscomycotaseptate hyphaeSpores located in asciYeasts (Neurospora)Sordaria ap lab 3Basidiomycotaseptate hyphaeClub fungi typical mushroomDeuteromycota Most Penicillium
Fungi as model organismsSmall genome relative to other eukaryotesMany fungal genes are homologous to those in other eukaryotesEasy to grow, short life cyclesHaploid genomes amenable to mutationSexual stage for analysis of segregation and recombination of genes; all products of meiosis can be retrieved in haploid sporesAsexual (clonal) reproductionFungal ReproductionMany fungi have the ability to reproduce by asexual and sexual means
Kingdom FungiPhyla:ChytridiomycotaForm motile spores called zoosporesMeiosis occurs in resting sporangiumGlomeromycotaForm spores containing hundreds of nuclei; no known sexual reproductionZygomycotaForm asexual spores called sporangiosporesMeiosis occurs in zygosporeAscomycota (including Deuteromycetes)Form asexual spores called conidiaMeiosis occurs in ascusBasidiomycotaMeiosis occurs in basidiumFungal life cycles The vegetative thallus predominates in the life cycle of a fungus The thallus may be haploid (1n), dikaryotic (n+n) or diploid (2n) in different groups of fungiPloidy of thallus is determined by the timing of these events in the life cycle:Plasmogamy (cell fusion)Karyogamy (nuclear fusion)Meiosis (reduction division)What are the 3 stages during the life cycle of the fungus?
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