chapter 21 outline
chapter 21 outline BIOL 1110
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This 5 page Class Notes was uploaded by Caitrín Hall on Tuesday January 26, 2016. The Class Notes belongs to BIOL 1110 at University of Connecticut taught by Bernard Goffinet in Summer 2015. Since its upload, it has received 12 views. For similar materials see Introduction to Botany in Biology at University of Connecticut.
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Date Created: 01/26/16
Fungi and Lichens 21.1 Distinctive features of the Fungi Eukaryotic organisms Differ from plants: o Lack plastids (heterotrophic) o Store energy in glycogen (a polysaccharide distinct from carb storage of algae and plants) instead of starch o Cell wall – composed of chitin Differ from animals o Inability to capture prey/solid food by phagocytosis o Cell wall Hyphae – microscopic threadlike, branched filaments; long & thin large surface area (helps obtain food) & ability to penetrate small spaces o Secrete enzymes that break down large organic molecules into sugars, small organic molecules, and mineral ions o Absorb molecules via membrane carrier proteins absorptive nutrition Form monophyletic group 21.2 Major fungal groups differ in reproduction Phylum chytridiomycota o Chrytids disperse in moist habitats by flagellate, wall spores, and absorb organic food from cells of other organisms o Often parasites or pathogens o Produce food-absorbing hyphae within host cells Phylum blastocladiomycota o Disperse by flagellate spores o Life cycle involves alternation of haploid and diploid hyphae o Haploid-dominant zygotic life is what fungi usually have Subphylum mucoromycotina o Zygomycetes – not monophyletic o Generate multinucleate hyphae that rarely produce cross-walls (septa) o Loss of flagella—live in terrestrial habitats o Sporangia open and release airborne spores that grow into hyphae o Sexually—non-flagellate gametes at hyphal tips o Gametes merge to form zygosporangium (fuse to form diploid nuclei) Zygospore – contain many diploid nuclei; meiosis disperses haploid spores Phylum Ascomycota o “Sac fungi” o Sexual spores are produced in sacks o Hyphae are divided into cells by septa o Regulate passage of materials through septal pores with spherical plugs o Sexual – gametes formed at ends of hyphae o Hyphae grow close, mating occurs, resulting cell with 2 nuclei undergoes mitosis to produce hyphae each with 2 nuclei NO diploid zygote Delay of meiosis allows production of more zygotes and sexual spores per mating Phylum basidionmycota o Mushrooms o Crop diseases o Basidiomycetes “club fungi” o Sexual spores produced at ends of club-shaped structures (basidia) o Distinctive septa – membranes regulate passage of materials; clamp connections o Compatible nuclei exist together in dikaryon for long periods before forming zygote in hyphal tips o Zygote produces diverse sexual spores Sexual spores are produced in diverse types of fruiting bodies o Fruiting bodies – fleshy bodies that promote dispersal of spores by wind, water, and insects Asexual spores are used to disperse well-adapted genetic types o Imperfect fungi – no sexual reproduction observed 21.3 Fungi live in beneficial associations with most plants Mutualists – fungi that obtain their food in a mutually beneficial partnership with algae or plants; symbiotic association o Endophytes – live compatibly in plants; obtain organic food while contributing toxins or antibiotics to deter pests o Mycorrhizae – association of soil fungi with plant roots Provide water and minerals (phosphorus and fixed nitrogen) & organic food Mycelium absorbs materials from larger volume of soil than roots Narrow and long reach tiny soil spaces for nutrients; bind soils to reduce water loss and erosion Ectomycorrhizae – minerals move from soil into hyphae, around plant roots, into root cells; sugar moves from root cells into hyphae Endomicorrhizae – grow extensively into root cells, penetrate cell walls (not membranes) by secreting enzymes; arbuscules develop between cell walls and membranes—branched to increase SA Mycoheterotrophy – non-photosynthetic plants gain organic compounds through mycorrhizal fungi from other plants 21.4 Fungi are relevant to humans in many ways Main decomposers of the planet o Break down biodegradable dead organisms, wastes, and other organic matter that would otherwise accumulate in nature o Release CO2, nitrogen, phosphate needed by living things Scientific study of DNA/life functions Food and industrial production (medicine included) Aflatoxins and psychogenic effects 21.5 Lichens are partnerships between fungi and photosynthetic microbes Masses of fungal hyphae with upper layers of autotrophic green algae or cyanobacteria (sometimes both) o Algae and cyanobacteria provide lichen fungi (mycobionts) with organic food and oxygen o Fungi provide their autotrophs (photobionts) with CO2, water, minerals, protection o Occupy habitats with high light intensity produce red compounds that help prevent damage to photobiont’s photosynthetic apparatus o Produce defensive toxins Evolutionary diversity o Not all from common ancestor o Most are dominated by ascomycete fungi o Few are dominated by basidiomycete fungi o Lichen bodies: Crustose – flat and tightly adherent to surface Foliose – flat, leaflike Fruiticose – grow upright or hang from tree branches Reproduction and development o Mostly asexual o Soredia – small clumps of hyphae surrounding a few photobiont cells that can disperse in wind; lichen clones o Sexual – small fruiting bodies produce windborne spores Spores that end up in favorable place produce hyphae that must find appropriate photobionts Ecology o Grow on surfaces that can dry out o Become dormant until moisture is available reason for slow growth o Help soil development when their acids break up surfaces o Food source for other hardy organisms Human uses o Air-quality and atmospheric radiation level monitor o Survival food Chapter Wrap-up Examine and Discuss Self Test 1. Describe four phyla of fungi: their habitats, distinguishing features, and one representative genus or species of each. 2. Discuss some of the economic uses of fungi. 3. Explain some of the reasons that fungi are ecologically important. 4. Discuss ways in which fungi can be harmful to people or property. 5. Describe three ways in which fungi engage in beneficial relationships with plants. 6. Name and describe the three major growth forms of lichens. Applying Concepts 1. While examining a soil sample with a light microscope, you see what appears to be a fungal hypha without any reproductive structures or spores. How could you determine the phylum into which this fungus would be classified? (Hint: think about cross walls, also known as septa.) 2. Some species of the fungal genus Penicillium produce the well- known antibiotic penicillin, which has had an enormous impact on human health. What benefit does the fungus derive from making penicillin? 3. Imagine that somehow a new virus arose that eliminated all fungi from planet Earth. What would be the effect of the loss of fungi on the environment? In answering this question, consider all of the ecological roles that fungi play, as discussed in this chapter. 4. Imagine that you are part of a team of explorers in a dry, cold region of the world lacking green plants of any type. What photosynthetic, eukaryotic life forms might be present in such a forbidding place, and how would you recognize them?
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