Fungi apbio-1204208133234612-5

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  • (a) A fungal mycelium spreads over decaying vegetation. The mycelium is composed of (b) a tangle of microscopic hyphae, only one cell thick, (c) portrayed in cross section to show their internal organization.
  • These filaments of the chytrid fungus Allomyces are in the midst of sexual reproduction. The orange structures visible on many of the filaments will release male gametes; the clear structure will release female gametes. Chytrid gametes are flagellated, and these swimming reproductive structures aid dispersal of members of this mostly aquatic phylum.
  • FIGURE 22-2 Some fungi can eject spores A ripe earthstar mushroom, struck by a drop of water, releases a cloud of spores that will be dispersed by air currents.
  • (a) Top: During asexual reproduction in the black bread mold (genus Rhizopus), haploid spores, produced within (b) sporangia, disperse and germinate on food such as bread. The resulting haploid hyphae may complete the asexual cycle by producing sporangia and spores.
  • (a) Top: During asexual reproduction in the black bread mold (genus Rhizopus), haploid spores, produced within (b) sporangia, disperse and germinate on food such as bread. The resulting haploid hyphae may complete the asexual cycle by producing sporangia and spores.
  • FIGURE 22-3 Evolutionary tree of the major groups of fungi
  • FIGURE 22-4 Chytrid filaments These filaments of the chytrid fungus Allomyces are in the midst of sexual reproduction. The orange structures visible on many of the filaments will release male gametes; the clear structures will release female gametes. Chytrid gametes are flagellated, and these swimming reproductive structures aid dispersal of members of this mostly aquatic phylum
  • FIGURE 22-5 (part 1) The life cycle of a zygomycete Top: During asexual reproduction in the black bread mold (genus Rhizopus ), haploid spores, produced within sporangia, disperse and germinate on food such as bread. Bottom: During sexual reproduction, hyphae of different mating types (designated + and - on the bread) contact one another and fuse, producing a diploid zygospore. The zygospore undergoes meiosis and germinates, producing sporangia that liberate haploid spores.
  • FIGURE 22-5 (part 2) The life cycle of a zygomycete Top: During asexual reproduction in the black bread mold (genus Rhizopus ), haploid spores, produced within sporangia, disperse and germinate on food such as bread. Bottom: During sexual reproduction, hyphae of different mating types (designated + and - on the bread) contact one another and fuse, producing a diploid zygospore. The zygospore undergoes meiosis and germinates, producing sporangia that liberate haploid spores.
  • FIGURE 22-5 (part 3) The life cycle of a zygomycete Top: During asexual reproduction in the black bread mold (genus Rhizopus ), haploid spores, produced within sporangia, disperse and germinate on food such as bread. Bottom: During sexual reproduction, hyphae of different mating types (designated + and - on the bread) contact one another and fuse, producing a diploid zygospore. The zygospore undergoes meiosis and germinates, producing sporangia that liberate haploid spores.
  • FIGURE 22-6 The life cycle of a typical ascomycete Top: In ascomycete asexual reproduction, haploid hyphae give rise to stalked structures that produce haploid spores. Bottom: In sexual reproduction, haploid nuclei of different mating types fuse to form diploid zygotes that divide and give rise to haploid ascospores.
  • (a) The cup-shaped fruiting body of the scarlet cup fungus (b) The morel, an edible delicacy. (Consult an expert before sampling any wild fungus—some are deadly!)
  • The mushroom (top left) is a reproductive structure formed from aggregated hyphae made up of cells that each contain two haploid nuclei. Within the cap, leaflike gills bear numerous basidia (top right). Within each basidium, the two haploid nuclei fuse, producing a diploid zygote. The zygote then undergoes meiosis, forming haploid basidiospores that are released from the basidia (right). After dispersal by wind or water, the basidiospores germinate, forming haploid hyphae. When hyphae of different mating types meet, some of the cells fuse. These cells, each containing two haploid nuclei, produce an extensive underground mycelium (bottom). Under appropriate conditions, portions of the mycelium aggregate, swell, and differentiate, poking up through the soil as mushrooms and completing the cycle.
  • The mushroom (top left) is a reproductive structure formed from aggregated hyphae made up of cells that each contain two haploid nuclei. Within the cap, leaflike gills bear numerous basidia (top right). Within each basidium, the two haploid nuclei fuse, producing a diploid zygote. The zygote then undergoes meiosis, forming haploid basidiospores that are released from the basidia (right). After dispersal by wind or water, the basidiospores germinate, forming haploid hyphae. When hyphae of different mating types meet, some of the cells fuse. These cells, each containing two haploid nuclei, produce an extensive underground mycelium (bottom). Under appropriate conditions, portions of the mycelium aggregate, swell, and differentiate, poking up through the soil as mushrooms and completing the cycle.
  • The giant puffball Lycopedon giganteum may produce up to 5 trillion spores. Shelf fungi, the size of dessert plates, are conspicuous on trees.
  • Mushrooms emerge in a fairy ring from an underground fungal mycelium, growing outward from a central point where a single spore germinated, perhaps centuries ago.
  • Most lichens have a layered structure bounded on the top and bottom by an outer layer formed from fungal hyphae. Attachments formed from fungal hyphae emerge from the lower layer and anchor the lichen to a surface, such as a rock or a tree. An algal layer in which the alga and fungus grow in close association lies beneath the upper layer of hyphae.
  • A colorful encrusting lichen, growing on dry rock, illustrates the tough independence of this symbiotic combination of fungus and alga.
  • Hyphae of mycorrhizae entwining about the root of an aspen tree. Plants grow significantly better in a symbiotic association with these fungi, which help make nutrients and water available to the roots.
  • This basidiomycete pathogen destroys millions of dollars’ worth of corn each year. Even a pest like corn smut has its admirers, though. In Mexico this fungus is known as huitlacoche and is considered to be a great delicacy.
  • Yeasts are unusual, normally nonfilamentous ascomycetes that reproduce most commonly by budding. The yeast shown here is Candida, a common cause of vaginal infections.
  • Penicillium growing on an orange. Reproductive structures, which coat the fruit’s surface, are visible, while hyphae beneath draw nourishment from inside. The antibiotic penicillin was first isolated from this fungus.
  • Truffles, rare ascomycetes (each about the size of a small apple), are a gastronomic delicacy.
  • The delicate, translucent reproductive structures of the zygomycete Pilobolus will literally blow their tops when ripe, dispersing the black caps with their payload of spores.
  • Arthrobotrys , the nematode (roundworm) strangler, traps its nematode prey in a nooselike modified hypha that swells when the inside of the loop is contacted.
  • Fungi apbio-1204208133234612-5

    1. 1. Chapter 22 TheFungi
    2. 2. Chapter 22 Fungal AnatomyMulticellularBody of almost all fungi is a mycelium, an interwoven mass of threadlike filaments called hyphae (singular, hypha)Chitin cell wallsHyphae of most species are divided into many cells by partitions called septa (singular, septum); each cell possesses one or more nuclei • Pores in the septa allow cytoplasm to stream from one cell to the next
    3. 3. The Filamentous Body Chapter 22 of a Fungus(a) Mycelium (c) Hyphal Cells (cutaway) Haploid Cytoplasm Nuclei Septum (b) Individual Hyphae Pore Cell Walls
    4. 4. Chapter 22 Chytrid FilamentsMaleFemale
    5. 5. Chapter 22 Fungal NutritionThree major types of heterotrophic nutrition • Saprophytic—digestion of dead organisms • Parasitic—digestion of live organisms • Symbiotic—mutual benefit of two independent organisms
    6. 6. Chapter 22 Fungal ReproductionAsexual • Fragmentation • Asexual spore formation – Haploid mycelium produces haploid asexual spores by mitosis – Spores germinate and develop into a new mycelium by mitosisResults in the rapid production of genetically identical clones
    7. 7. Chapter 22
    8. 8. Chapter 22 Fungal Sexual ReproductionTypically occurs under conditions of environmental change or stress • Neighboring haploid mycelia of different, but compatible mating types come into contact with each other • The two different hyphae fuse so that the nuclei share a common cell • The different haploid nuclei fuse to form a diploid zygote • Zygote undergoes meiosis to form haploid sexual spores
    9. 9. Zygomycete Life Cycle (a) Chapter 22Sporangia Spores (haploid) Diploid 2n Zygospore Haploid germinates 1n Hyphae of opposite mating types fuse to (b) Photo of Sporangia form zygospore.
    10. 10. Zygomycete Life Cycle (b) Chapter 22 Hyphae of opposite mating types (+ & -) fuse. Zygospore germinates MEIOSIS NUCLEI FUSEHaploid 1n Diploid ZygosporeDiploid formed 2n
    11. 11. Chapter 22 Classification of FungiFungi have been assigned to four phyla based upon the way they produce sexual spores • Chytridiomycota (chytrids) • Zygomycota (zygote fungi) • Ascomycota (sac fungi) • Basidiomycota (club fungi)
    12. 12. Chapter 22
    13. 13. Chapter 22 The ChytridsChytrids • Most are aquatic • Reproduce both asexually and sexually • Form flagellated spores that require water for dispersal • Figure 22-4, p. 426, illustrates the chytrid fungus Allomyces in the midst of sexual reproduction
    14. 14. Chapter 22
    15. 15. Chapter 22 The ChytridsMost feed on dead aquatic materialSome species are parasites of plants and animals • One chytrid species is a frog pathogen believed to be a major cause of the current worldwide die-off of frogsPrimitive chytrids are believed to have given rise to the other groups of modern fungi
    16. 16. Chapter 22 ZygomycetesMost live in soil or on decaying plant or animal materialReproduce both asexually and sexually • Sexual spores are thick-walled zygosporesDuring asexual reproduction: • Haploid spores are produced via mitosis in black spore cases called sporangia • Spores disperse and germinate to form new haploid hyphae
    17. 17. Chapter 22 ZygomycetesDuring sexual reproduction • Two hyphae of different mating types come into contact and fuse • Nuclei fuse to form a diploid zygospore, a tough, resistant structure that can remain dormant for long periods until conditions are favorable • Meiosis occurs as the zygospore germinates • Resulting spores disperse and germinate to form new haploid hyphae that can enter either the asexual or sexual cycle
    18. 18. Chapter 22
    19. 19. Chapter 22
    20. 20. Chapter 22
    21. 21. Chapter 22 AscomycetesLive in a variety of marine, freshwater, and terrestrial habitatsReproduce both asexually and sexually • Sexual spores form in saclike asciDuring asexual reproduction • Haploid spores are produced via mitosis at the tips of specialized hyphae • Spores disperse and germinate to form new haploid hyphae
    22. 22. Chapter 22 AscomycetesDuring sexual reproduction • Two hyphae of different mating types come into contact and fuse, resulting in the formation of a fruiting body
    23. 23. Chapter 22
    24. 24. Chapter 22 AscomycetesBetter known examples include • Most of the food-spoiling molds • Morels and truffles (edible delicacies) • Penicillium, the mold that produces penicillin (the first antibiotic) • Yeasts (single-celled fungi)
    25. 25. Chapter 22 Some Ascomycetes(a) Scarlet Cup Fungus (b) Morel
    26. 26. Chapter 22 BasidiomycetesLive in a variety of marine, freshwater, and terrestrial habitatsUsually reproduce sexually • Sexual spores form in club-shaped basidiaDuring sexual reproduction: • Two hyphae of different mating types come into contact and fuse, resulting in the formation of a fruiting body
    27. 27. Chapter 22 Basidiomycete Life Cycle Haploid Nuclei Fusion forms diploid zygote. Basidia SIS on gills MEIO Basidiospores (haploid)Diploid Mushroom gills 2n bear reproductiveHaploid basidia. 1n
    28. 28. Chapter 22 Basidiomycete Life Cycle Basidiospores (haploid) Basidia on gills Hyphae aggregate to form mushroom “+” Mating Strain “-” Mating Strain Basidiospores germinate forming hyphae (haploid). +Diploid - Hyphae fuse, but 2n haploid nucleiHaploid remain separate 1n in binucleate cells
    29. 29. Chapter 22 BasidiomycetesBetter known examples include • Mushrooms (some are edible, others are poisonous) • Puffballs • Shelf fungi (decomposers of wood) • Stinkhorns • Rusts and smuts (plant parasites) • Yeasts
    30. 30. Chapter 22 Some Basidiomycetes(a) Giant Puffball (b) Shelf Fungi
    31. 31. Chapter 22 Fairy RingsA fairy ring is a circular pattern of mushroom growthFairy rings form at the leading edge of an expanding underground fungal mycelium • The wider the diameter of the ring, the older the mycelium • Some fairy rings are estimated to be 700 years old
    32. 32. Chapter 22A Mushroom Fairy Ring
    33. 33. Chapter 22 Symbiotic RelationshipsA symbiosis is a close interaction between organisms of different species over an extended period of timeThe fungal member of a symbiotic relationship may be harmful (a parasite of plants or animals) or beneficial (lichens and mycorrhizae)
    34. 34. Chapter 22 LichensLichens are symbiotic associations between fungi (usually an ascomycete) and algae or cyanobacteria • Fungus provides photosynthetic partner with shelter and protection • Photosynthetic partner provides fungus with food (sugar)
    35. 35. Lichens: Chapter 22Symbiotic Partnerships Algal LayerFungal Hyphae Attachment Structure
    36. 36. Chapter 22 LichensGrow on a wide variety of materials (soils, tree trunks and branches, rocks, fences, roofs, and walls)Are able to survive environmental extremes (newly formed volcanic islands, deserts)Are very diverse in form
    37. 37. Chapter 22Lichens Covering a Rock
    38. 38. Chapter 22 MycorrhizaeMycorrhizae (singular, mycorrhiza) are symbiotic associations between fungi and plant roots • Fungus provides plant with water, minerals, and organic nutrients it absorbs from the soil • Plant provides fungus with food (sugar)80% of plants with roots have mycorrhizaeRelationship may have helped plants colonize land
    39. 39. Mycorrhizae Chapter 22Enhance Plant Growth Mycorrhizae
    40. 40. Chapter 22 RecyclersFungi are Earth’s undertakers, feeding on the dead of all kingdomsFungal saprophytes (feeding on dead organisms) release extracellular substances that digest the tissues of the dead and liberate carbon, nitrogen, phosphorus compounds, and minerals that can be reused by plants
    41. 41. Chapter 22 Fungi Attack PlantsFungal parasites cause the majority of plant diseases • Ascomycete parasites cause Dutch elm disease and Chestnut blight • Rusts and smuts are basidiomycete parasites that cause considerable damage to grain crops
    42. 42. Chapter 22Corn Smut
    43. 43. Chapter 22 Fungi Cause Human DiseasesAthlete’s foot, jock itch, and ringworm are caused by fungi that attack the skinValley fever and histoplasmosis are caused by fungi that attack the lungs • Infection occurs when victim inhales sporesMost vaginal infections are caused by the yeast Candida albicans
    44. 44. Chapter 22Yeasts Candida sp.
    45. 45. Chapter 22 Fungi Produce ToxinsClaviceps purpurea (an ascomycete) produces several toxins • Infects rye plants and causes ergot disease • Symptoms of ergot poisoning include vasoconstriction of blood vessels, vomiting, convulsive twitching, hallucinations, and deathPenicillin • First antibiotic to be discovered • Used to combat bacterial diseases
    46. 46. Chapter 22Penicillium
    47. 47. Chapter 22 Fungi Contribute to GastronomyCertain ascomycete molds impart flavor to some of the world’s most famous cheeses • Roquefort • Camembert • Stilton • GorgonzolaYeasts are used in the production of wine, beer, and breadWine is produced when yeasts ferment fruit sugars; ethyl alcohol is retained, while CO2 is released
    48. 48. Chapter 22 Fungi Contribute to GastronomyBeer is derived when yeasts ferment sugars in germinating grains (usually barley); ethyl alcohol and CO2 are retainedBread rises when yeasts ferment sugar that has been added to bread dough; both ethyl alcohol and CO2 escape during bakingSome fungi are consumed directly • Mushrooms (a basidiomycete) • Morels (an ascomycete) • Truffles (an ascomycete)
    49. 49. Chapter 22Truffles
    50. 50. Chapter 22 Fungal IngenuityThe truffle has evolved an effective adaptation for dispersal of its spores • Releases an odor which causes pigs and other animals to dig it up, scattering spores to the windsThe zygomycete Pilobolus has evolved bulb tops that blast off, spreading spores
    51. 51. Pilobolus: Chapter 22An Explosive Zygomycete
    52. 52. Chapter 22 Fungal IngenuityArthrobotrys cleverly traps and “strangles” microscopic roundworms called nematodes to obtain nutrients
    53. 53. Chapter 22The Nemesis of NematodesUnfortunate nematode Special hypha with noose
    54. 54. Chapter 22TheEnd

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