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Fungi

Fungi. Decomposers, Mutualists, and Killers. Fungi. Fungi (most) degrade dead organic matter form nutritional partnerships with most vascular plants & some algae are pathogens of some plants & animals. parasitic fungi Figure 31.1. Fungi. Fungi are absorptive heterotrophs saprobic

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Fungi

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  1. Fungi Decomposers, Mutualists, and Killers

  2. Fungi • Fungi • (most) degrade dead organic matter • form nutritional partnerships with most vascular plants & some algae • are pathogens of some plants & animals

  3. parasitic fungiFigure 31.1

  4. Fungi • Fungi • are absorptive heterotrophs • saprobic • mutalistic • parasitic • predatory (rarely)

  5. predatory fungusFigure 31.5

  6. fungal hyphaeFigure 31.3

  7. Fungi • Fungal growth forms • yeasts are unicellular • most fungi produce multinucleate hyphae • high surface area for absorption • coenocytic or septate • chitinous cell walls • mycelia are massed hyphae

  8. conidIaFigure 31.12

  9. budding yeastFigure 31.2

  10. Fungi • Fungal reproduction • asexual reproduction • sporangia - chambers producing haploid spores • conidia - naked spores on hyphal tips • binary fission or budding • fragmentation

  11. Fungi • Fungal reproduction • sexual reproduction • between haploid hyphae of different mating types • fusion of haploid hyphae (plasmogamy) produces dikaryotic (n+n) hyphae (heterokaryon) • dikaryotic nuclei eventually fuse (karyogamy) to produce zygote • meiosis produces haploid spore nuclei

  12. Fungi • Phylogeny • four phyla differ in • presence of septa in hyphae • sexual reproductive structures • methods of sexual spore formation • DNA sequencing agrees that the four phyla are monophyletic

  13. Fungi • Phylogeny • deuteromycetes are fungi without sexual reproductive data • a polyphyletic “holding category” • new techniques are assigning deuteromycetes to the four phyla

  14. fungal phylogenyFigure 31-6

  15. fungal classificationTable 31.1

  16. Fungi • Phylum Chytridiomycota • earliest diverging fungal group • aquatic • parasitic or saprobic (rarely mutualistic) • unicellular or mycelial • haploid or diploid, none dikaryotic

  17. Fungi • Phylum Chytridiomycota • reproduction in Allomyces • haploid zoospore germinates to produce haploid body • haploid body produces male and female gametangia • gametangia produce haploid gametes • [flagellated gametes and zoospores is a unique (ancestral?) character]

  18. Fungi • Phylum Chytridiomycota • reproduction in Allomyces • pheromone attracts male gamete to female • fusion of gamete nuclei produces zygote • zygote grows into diploid body • diploid body produces many diploid zoospores • diploid zoospores produce more diploid bodies

  19. Fungi • Phylum Chytridiomycota • reproduction in Allomyces • diploid bodies produce resting sporangia • meiosis within resting sporangia produces haploid zoospores • alternation of generations

  20. Allomyces sp. gametangia forming haploid gametesFigure 31.7

  21. Fungi • Phylum Zygomycota • mostly coenocytic • haploid except zygote • entirely nonmotile • some participate in mycorrhizal association with plants • familiar example: Rhizopus stolonifer

  22. Pilobolus sp.sporangiophores topped with sporangiaFigure 31.8

  23. sporangium shedding sporesFigure 31.9

  24. Fungi • Phylum Zygomycota • reproduction • asexual spores are produced on stalked sporangiophores bearing single or multiple sporangia • sexual reproduction occurs between hyphae of different mating types

  25. Fungi • Phylum Zygomycota • reproduction • sexual reproduction • pheromones cause hyphae to grow toward each other • gametangia are produced and fuse into a zygosporangium • gametes (1n) fuse into a zygote (2n)

  26. Fungi • Phylum Zygomycota • reproduction • sexual reproduction • meiosis produces zygospores (1n) inside the resistant zygosporangium • after dormancy, zygosporangium releases zygospores • zygospores germinate to produce haploid hyphae

  27. Zygomycete life cycleFigure 31.9

  28. Fungi • Phylum Ascomycota • large diverse group (~30,000 spp.) • saprobes, parasites, mutualistic symbionts • hyphae segmented by porous septa • produce sexual spores in asci (sacs)

  29. Fungi • Phylum Ascomycota • two major subgroups • Hemiascomycetes • mostly unicellular (yeasts) or microscopically multicellular • asexual reproduction by fission or budding

  30. Fungi • Phylum Ascomycota • Hemiascomycetes • sexual reproduction • fusion of haploid cells of different mating types • [+/- mitotic population growth] • meiosis produces four haploid nuclei • [+/- mitosis to produce eight] • ascospores in the original cell = ascus

  31. Fungi • Phylum Ascomycota • Hemiascomycetes • familiar example = Saccharomyces cerevisiae (baker’s, brewer’s yeast)

  32. Fungi • Phylum Ascomycota • Euascomycetes • mycelia of septate hyphae • multicellular sexual fruiting bodies: ascocarps • asexual reproduction by conidia

  33. Fungi • Phylum Ascomycota • Euascomycetes • sexual reproduction • mating structures form on two compatible mating types • haploid nuclei from the “male” enter the female mating structure • the dikaryotic mating structure produces ascogenous hyphae

  34. Fungi • Phylum Ascomycota • Euascomycetes • sexual reproduction • tips of n+n hyphae form asci • in asci, haploid nuclei fuse • meiosis produces four haploid nuclei • [+/- mitosis to form 8 haploid nuclei] • spores are formed and released

  35. characteristic ascomycete reproductive sacsFigure 31.10

  36. Ascomycete life cycleFigure 31.13

  37. Fungi • Phylum Ascomycota • Euascomycetes • familiar examples • Neurosporacrassa bread mold used by Beadle and Tatum • brightly colored cup fungi • morels & truffels • Penecillium spp. • Aspergillus spp.

  38. Figure 31.11

  39. Fungi • Phylum Basidiomycota • large diverse group (~25,000 spp.) • saprobes, parasites, mutualistic symbionts • produce sexual spores on basidia

  40. Fungi • Phylum Basidiomycota • familiar examples • puffballs • bracket fungi • mushrooms and toadstools, edible and toxic • bird’s nest fungi • jelly fungi • smut and rust fungi

  41. BasidiomycetesFigure 31.14

  42. Fungi • Phylum Basidiomycota • sexual reproduction • basidiospores germinate to produce haploid, septate hyphae • hyphae of different mating types fuse to form dikaryotic hyphae • dikaryotic hyphae eventually produce a characteristic basidiocarp

  43. Fungi • Phylum Basidiomycota • sexual reproduction • basidiocarp bears surfaces covered with basidia • two nuclei in n+n basdium fuse to form 2n zygote • meiosis produces four basidiospores • basidiospores are displayed on tip of basidium and released

  44. basidiomycete life cycleFigure 31.15

  45. Fungi • Fungal Mutualisms with plants • mycorrhizae • endomycorrhizal fungi are within the root • ectomycorrhizal fungi are outside the root • fungal symbiont enhances absorption of water and some nutrients by photosymbiont • photosymbiont provides carbohydrate to fungal symbiont

  46. Fungi • Fungal mutualisms with plants • lichens (~13,500 spp.) • partnerships between fungi and green algae or cyanobacterium • fungal symbionts are usually ascomycetes • lichen are classified as distinct organisms • among the hardiest organisms

  47. Fungi • Fungal mutualisms with plants • lichens • critical primary producers in arctic ecosystems • fungal symbiont provides mineral nutrients • photosymbiont provides fixed carbon • among the most environmentally sensitive organisms

  48. Fungi • Fungal mutualisms with plants • lichens • three general growth forms • crustose - crust-like • foliose - “leafy” • fruticose - “shrubby”

  49. crustose, foliose, fruticose lichensFigure 31.17

  50. Fungi • Fungal mutualisms with plants • lichens • reproduction • fragmentation of thallus • some fungal symbionts produce ascospores or basidiospores

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