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Lecture 161. List the defining characteristics of Fungi2. Describe the ecological and symbiotic roles of Fungi3. Name and characterize each of the six groups of Fungi Fungi are related to animals Opisthokonts Absorptive heterotrophy Chitin in cell walls Flagellated ancestor Developed from Unicellular protist with a flagella Absorptive heterotrophy Secrete digestive enzymes outside of body- Break down large food molecules Absorb breakdown products through plasma membrane Can also be Saprobes Parasites Mutualists Fungi are made up of 6 major groups Microsporidia Chytrids Not monophyletic Zygomycota [zygospore fungi] Not monophyletic Glomeromycota [mycorrhizal fungi] Ascomycota [sac fungi] Monophyletic  Basidiomycota [club fungi] Monophyletic Unicellular fungi are called yeasts Aquatic/moist Absorb nutrients through cell surfaces Yeasts are not monophyletic “yeast” refers to a lifestyle; not a taxonomic group Includes:  Zygospore fungi [zygomycota] Sac fungi [Ascomycota] Club fungi [basidiomycota] Multicellular fungi are composed of hyphae Mycelium  Body of a multicellular fungus Composed of a mass of individual filaments (hyphae) ** Septum Incomplete cross walls Subdivided cell-like compartments in hyphae Septate Fungi that have septum Coenocytic  Hyphae that lack septum Have hundreds of nuclei Results from repeated nuclear divisions Dikaryotic - N + N Fungi are absorptive heterotrophs External digestion Surface area to volume ratio Due to hyphae being close to environment Causes fungi to lose water rapidly in dry environments  Absorption Fungi have cell walls with more than one nucleus Mitosis differences Production of haploid spores within structures called sporangia Production of haploid spores [not enclosed in sporangia] at the tips of hyphae are called conidia Cell division by unicellular fungi- Fission Relatively equal division- Budding Asymmetrical division Simple breakage of mycelium Plasmogamy Fusion of cytoplasm Karyogamy Fusion of nuclei No loss of nuclear envelope Most lack centrioles Fungi reproduce sexually or asexually Plasmogamy Karyogamy Mating types Genetically determined distinction Two fungi of the same mating type cannot reproduce Alternation of generations Conidia Not enclosed; spores at tips of the hyphae Sporangia Enclosed spaces Fungi can be saprobes Global carbon cycle Carbon cycle would fail without fungi Nitrate, ammonium, but not N2 Obtain nitrogen from proteins/ products of protein breakdown Peat Formation leads to acidification of swamps Which drastically reduces fungal populations Permian extinction Fungi flourished Symbioses are partnerships that can be positive, negative, or in between Obligate  Parasites that grow only on their specific living hosts Facultative  Parasites that can attack living organisms but can also grow by themselves and in artificial environments Fungi can be pathogens, parasites, or predators Parasites Can produce haustonia- Branching projections that push through cell walls into living plants cells- Absorb nutrients from those cells Fungi may play a role in amphibian decline Batrachochytrum dendrobatidis Attacking amphibian populations Symbioses between fungi and bacteria (cyanobacteria) or green algae are called Lichens Most are Ascomycota 30,000 “species” Found in all sorts of exposed habitats Mycorrhizae are symbioses between plants and fungi Ectomycorrhizae Fungi wraps around the roots of plants Arbuscular mycorrhizae Fungi enter the root of plants and penetrates the cell wall of root cells- Inside cell wall but outside plasma membrane Plants and colonization of land Mycorrhizar evolution was the single most important step in the colonization of the terrestrial environment by living things Microsporidia are unicellular parasites Lack mitochondria, buthave mitostomes Derived from mitochondria- Contain no DNA Unicellular fungi with walls that contain chitin Obligate parasites Can infect mammals and even humans Penetrate host with polar tube Sporoplasm Replicates within host cell and produces new infective spores Chytrids have flagella Once classified as protists Aquatic  Environment where fungi first evolved Flagellated gametes Parasitic/saprobic Many live in freshwater or moist soil but some are marine Coenocytic, but not dikaryon Zygospore fungi produce zygotes Haploid for most of their life Reproduce largely asexually Glomeromycota are asexual plant symbionts Obligate symbionts Asexual reproduction Sister group to dikarya Ascomycota produce sac like fruiting bodies Sexual and asexual reproduction Dikaryon ***** Asci Sacs that contain sexually produced ascospores Include yeast, penicillin, truffles Basidiomycota have dikaryotic mushrooms Saprobic Basidiomata Fruiting structures N + N Diploid momentarily Basidium Sexual reproductive

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Ole Miss BISC 162 - Lecture notes

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