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Fungal Ecology.docx

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Western University
Biology 4218A
Richard Gardiner

Fungal Ecology Fungi - Cannot fix energy directly - Use the energy stored in plant and animal biomass to create their mass Ecosystem - Abiotic substances: basic inorganic and organic compounds of environment - Producers: autotrophic organisms - Consumers: heterotrophic organisms - Decomposers/saprobes: heterotroph organisms that break down the complex compounds of dead organisms Saprobes in Nature - Majority of substrata that decay-organisms attack represent the ‘garbage of nature’ - Weight of leaves formed by single tree calculated = 2 tons over a 10 year period - Hardwood forest = 1 – 2 tons of leaves/branches are dropped per acre annually Ecological impacts of fungi Positive - Terrestrial communities dependent on fungi - Plants and fungi to land together 400 million years ago o Mycorrhizae – improvement of plant growth o Lichens – initial colonization of rocks o Food – source for animal Negative - Parasites and pathogens - Chestnut blight and Dutch elm disease - Catastrophic declines in amphibian pops Fruiting structure = disseminate spores by wind or animals Mycelium = elongate hyphal cells, branching pattern related to resource availability Rhizomorph = composed of amassed hyphae, organized into a conducting structure Making Nutrients available - Fungi obtain their nutrients by the secretion of extracellular enzymes into the environment - Fraction of useful resources being released into environment - Secretion of oxalic acid can aid in the weathering of calcareous bedrock Cellulose decomposition Cellulose  cellulase  long B1,4  cellulase  cellobiose  cellobiase  glucose Saprophytic fungi in soil - Numbers of microorganisms in 1 g of soil - True bacteria 10^6 – 10^9 - Actinomycetes 10^5 – 10^6 - Protozoa 10^4 – 10^5 - Fungi 10^4 – 10^5 Fungal life strategies: R, S and C selected (c: competitive selection; s: survival in stressful environments; r: rapid rates of reproduction with short life spans) R selected fungi: o Mucor, Rhizopus, Philobolus o Common in soil and dung o Sporangiophores germinate quickly o Mycelium develops quickly when nutrients are present o Reproductive structures formed soon after mycelium develops o Depletion of nutrients or completion causes the mycelium to collapse S selected fungi: o Some fungi grow in environments too extreme for other f
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