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Chapter31[1] - Chapter 31 Fungi I Introduction What are...

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Chapter 31: Fungi I. Introduction: What are Fungi? a. 80,000 identified species so far b. Eukaryotes c. Single or multi-celled (branching networks of multicellular filaments) d. Terrestrial e. Heterotrophs, Decomposers i. without fungi, the Earth would be piled high with dead trees ii. only fungi and a few bacteria are capable of digesting both cellulose (in plant cell wall) and lignin (in wood) f. Parasites (athlete’s foot, yeast infection), mutualists II. Why Do Biologists Study Fungi? a. Fungi Provide Nutrients to Land Plants i. Fungi + plant root = mycorrhizal association b. Fungi Speed up the Carbon Cycle on Land i. Decomposers and recyclers ii. Saprophytes (eat dead plant material) iii. During Carboniferous Period 1. few fungal fossils (high acid environment) 2. An increase in peat and coal production because plants were not broken down. iv. at the end of the Permian Period (250 mya) 1. greatest mass extinction of all time 2. brief increase in fungal fossils 3. thought that massive die-off of trees provided rotting wood and a favorable environment for fungi. v. Fungi complete carbon cycle by breaking down dead/rotting organisms c. Fungi Have Important Economic Impacts i. Some (a very few) are pathogenic ii. Some produce antibiotics iii. Impact on crop production and storage iv. Impact on food industry 1. mushrooms are eaten 2. food production using fungi: bread, soy sauce, tofu, cheese, beer, wine, whiskey v. Impact on environment 1. pathogen to certain trees (chestnut blight) Dutch elm disease d. Fungi are key model organisms in Eukaryotic genetics i. Neurospora (one gene, one enzyme) ii. Saccharomyces – model for eukaryotic cells (easy to grow in lab) III. How Do Biologists Study Fungi? a. Direct sequencing b. Analyzing morphological traits (only 2 growth forms) i. Single-celled = yeasts ii. Multi-celled, filamentous = mycelia 1. dynamic: grow out and die back with changes in food supply 2. can become very large (1310 acre organism in Oregon) 3. hyphae (individual filaments of mycelium) a. haploid (some are heterokaryotic (2 haploid nuclei) b. hyphae are very thin tubes. This thinness increases surface area to volume ratio and increases the absorption potential, while
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