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Chapter 22 Opisthokants:group of fungi,animals, and choanoflagellates modes of nutrition◦ Saprobes:absorb nutrients from dead organic matter◦ Parasites:absorb nuterients from living hosts◦ Mutualists:benefit both partners fungi evolved from unicellular protist that had falgellum Unicellular,free-living fungi are yeasts Body of multicellular fungi=mycelium◦ composed of individal tubular filaments (hyphae)▪ hyphae subdivided into cell-like ocmpartments by incomplete cross-walls=septa▪ other species have hundreds of nuclei=coenocytic and no septa  Fungi have tolerance for highly hypertonic environmental Saprobic fungi are major decomposers on earth◦ no decomposers=no carbon cycle on earth◦ produce spores Facultative parasites:grow on living organisms,but can grow by themselves Obligate parasites:only grow on specific living host  Lichens: association of fungi with cyanobacteria,photosynthetic alga, or both◦ susceptible to poor air quality, but can survive in harsh environments◦ body forms:▪ crustose(crustlike):lichens look like colored poweder dusted over substrate▪ foliose(leafy)▪ fructicose(shrubby)◦ reproduce by fragmentation of vegetative body(thallus) or by specialized structures (soredia) Mycorrhizae:association of fungi and roots of plants◦ fungus obtais material and provides minerals and water to plant◦ endomycorrhizae:fungus wraps around root▪ dont penetrate cell walls▪ increase surface area for absorption of water/minerals◦ arbuscular mycorrhizae:enter root and penetrate cell walls of root cells▪ form arbuscular (treelike) structure inside cell wall◦ fungus provides better absorption of H20 and obtains organic compounds from plant▪ may provide plant with growth hormones and protection from disease causing microbes◦ plants that lakc chlorophyll have mycorrhizae Endophytic fungi:fungi that live within plants and don't cause obvious deleterious symptoms  6 major groups of fungi◦ microsporidia◦ chytrids◦ zygospore fungi◦ arbuscular mycorrhizal fungi◦ sac fungi◦ club fungi Asexual reproduction forms◦ production of haploid spores within structures called sporangia◦ production of haploid spores at tips of hyphae called conidia◦ Cell division by unicellular fungi: ▪ fission:equal division of cell into 2▪ budding:asymmetrical division in which smaller daughter cell produced  Individuals of same mating type cannot mate◦ can mate with other mating type of same species Microsporidia◦ unicellular parasitic fungi◦ lack mitochondria have reduced structures(mitosomes)▪ mitosomes contain no DNA◦ hots cell penetrated by polar tube that grows from microsporidian spore ▪ contents injected into cell called sporoplasm chytrids◦ possess flagellated gametes◦ only fungi to have flagella at any lie cycle stage◦ reproduce both asex. And sex.◦ Parasitic and mutualistic Other 4◦ cytoplasms of two individuals of different mating type fuse (plasmogamy) before nuclei fuse (karyogamy)◦ Zygospore=resting stage undergoes meiosis to become sporangiophore◦ Sporangiophore:fruiting structure Arbuscular mycorrhizal fungi◦ Symbiotic, mutualistic relationship with plants◦ hyphae=coenocytic◦ reproduce asex. Last 2◦ two genetically different haplod nuclei co-exist and divide within each cell of mycelium▪ stage is dikaryon▪ ploidy indicated by n+n Sac fungi◦ distinguished by production of sacs called asci Club fungi◦ septate=hyphae◦ Basidium (swollen cell at tip of specialized hypha) is characteristic◦ basidiomata=fruiting structure, basidia=reproductive


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UNLV BIOL 197 - Chapter 22

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