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Chapter 18

Chapter 18. Fungus. 18.1 Fungi are adapted for nutrition by absorption. hyphae: tiny threads of cytoplasm surrounded by a plasma membrane and covered by a cell wall Cell walls made of chitin Strong , flexible polysaccharide Cross-walls: divide the long filaments into many cells

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Chapter 18

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  1. Chapter 18 Fungus

  2. 18.1 Fungi are adapted for nutrition by absorption • hyphae: tiny threads of cytoplasm surrounded by a plasma membrane and covered by a cell wall • Cell walls made of chitin • Strong , flexible polysaccharide • Cross-walls: divide the long filaments into many cells • Exchange cytoplasm, organelles and distribute nutrients

  3. Mycelium • mycelium(mycelia): interwoven mat of hyphae • Feeding structure • Maximizes surface area within food • Km of hyphae each day • In Oregon, mycelium is 5.5 km across, 9 km2 of forest, 2400 years old

  4. Nutrition • absorptive nutrition: method by which the fungus absorbs small organic molecules from its surroundings • Digests food outside mycelium by secreting enzymes • Enzymes break down molecules so they can be absorbed • Food sources • Fallen logs, dead animals, waste • Parasitic fungi: absorb nutrients from living hosts

  5. Reproduction • spores: haploid single cells with thick cell walls • Spread by wind and can withstand unfavorable conditions • Most are asexual • Sexual reproduction: haploid hyphae from different mycelia fuse together and combine genetic info • Can produce trillions of spores • Puffballs • Found 200 km above the surface

  6. 18.2 Kingdom Fungi consists of diverse forms

  7. Zygote Fungi • Mostly terrestrial and live in soil or decaying material • Rhizopus stolonifer • Food available= asexual reprod. • Sporangia: spore-forming structures at tips of hyphae • Food depleted= sexual • Two mycelia fuse • zygosporangium: reproductive structure

  8. Sac Fungi • Marine, freshwater, and terrestrial • Single-celled or large morels • Ascus (sac) contains spores • Similar reproduction to zygote fungus

  9. Club Fungi • Agaricus bisporus • Most common • Important decomposers of wood and plant material • Some are parasites • Usually sexual • Spores drop from “gills” underneath • Can grow within hours

  10. Club Fungi Reproduction

  11. Yeast • Single-celled fungi • Inhabit liquid or moist habitats • Plant sap and animal tissues • Reproduce asexually • Cell division or pinching of “buds” • Some sexually • Form ascus or basidium; classified as sac or club • Imperfect fungi: no known sexual stage of reproduction • Used for fermentation or raise dough

  12. Mold • Any fungus that grows very rapidly on a surface • Most asexual • Some imperfect • Sexual stages place some in zygote, sac, or club • Rhizopus - zygote • Penicillium - sac

  13. Mmmmm…. cheesy

  14. 18.3 Fungi have a major impact on other life. • Symbiotic fungi • Close relationship between two different species that benefits at least one of them • Mutualistic: both benefit

  15. Lichen • lichen: mutualistic pairing of a fungus and an alga • Photosynthetic algae feed the fungus • Fungal mycelium provides a good habitat • Usually a sac fungus and either green algae or cyanobacteria • More than 25,000 “species” of lichen

  16. Benefits of lichen symbiosis • Environments where neither could live on its own • Pioneer organisms • Tundra • Do not tolerate air pollution; death of lichen = poor air quality

  17. Mycorrhizae • Symbiotic relationship between fungal hyphae and plant roots • Fungus provides more water and nutrients, plant provides sugar • Mushrooms around trees

  18. Disease-causing fungi • 30% of fungi are parasitic • Dutch Elm disease • Eliminated most elm trees in N Amer • 50 species parasitic in humans and other animals • Yeast infections • Ringworm • Athlete’s Foot

  19. Commercial Uses • Truffles • Cheese • Fungi “ripen” them • Yeast for baking and brewing • Antibiotics

  20. Chemical Cycling • Decompose matter • Circulate carbon and nitrogen • Some can decompose clothing, boots, glue, and plastic

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