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Kingdom Fungi

Kingdom Fungi. Chapter 26. Learning Objective 1. What are the distinguishing characteristics of kingdom Fungi?. Fungi. Eukaryotic heterotrophs Secrete digestive enzymes onto food then absorb predigested food Cell walls with chitin. KEY CONCEPTS.

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Kingdom Fungi

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  1. Kingdom Fungi Chapter 26

  2. Learning Objective 1 • What are the distinguishing characteristics of kingdom Fungi?

  3. Fungi • Eukaryotic heterotrophs • Secrete digestive enzymes onto food • then absorb predigested food • Cell walls with chitin

  4. KEY CONCEPTS • Fungi are eukaryotic heterotrophs that absorb nutrients from their surroundings

  5. Learning Objective 2 • What is the body plan of a fungus?

  6. Fungi Structures • Fungi include • unicellular yeast • filamentous, multicellular mold • Most multicellular fungi • have long, threadlike filaments (hyphae) • branch and form a tangled mass (mycelium)

  7. Insert “Mycelium” mycelium.swf

  8. Learn more about mycelium by clicking on the figure in ThomsonNOW.

  9. Hyphae • In most fungi • perforated septa (cross walls) divide hyphae into individual cells • In some fungi • zygomycetes and glomeromycetes • hyphae are coenocytic (form elongated, multinuclear cell)

  10. Fungus Body Plan

  11. Hyphae 25 µm Fig. 26-1 (a-b), p. 557

  12. Fig. 26-1 (c-e), p. 557

  13. KEY CONCEPTS • A fungus may be a unicellular yeast or a filamentous, multicellular mold consisting of long, branched hyphae that form a mycelium

  14. Learning Objective 3 • What is the life cycle of a typical fungus, including sexual and asexual reproduction?

  15. Reproduction • Most fungi reproduce sexually and asexually by spores • Spores • produced on aerial hyphae • land in suitable spot and germinate

  16. Germination of a Spore

  17. Spore Hypha Mycelium Fig. 26-2, p. 557

  18. Asexual Reproduction

  19. Bud development Fig. 26-3a, p. 558

  20. Fig. 26-3b, p. 558

  21. Plasmogamy • Fungi of two different mating types meet, hyphae fuse • cytoplasm fuses • nuclei remain separate • Fungi enter dikaryotic (n + n) stage • each new cell has one nucleus of each type

  22. Karyogamy • Fusion of nuclei • takes place in hyphal tip • results in diploid (2n) zygote nucleus

  23. Genetic Divisions • Meiosis • produces 4 different haploid (n) nuclei • each nucleus becomes part of a spore • Mitosis • forms new mycelia when spores germinate

  24. Asexual Spores • Can be produced by mitosis • genetically similar • When these spores germinate • they also develop into mycelia

  25. Fungal Life Cycles

  26. 7 8 Spore germinates and forms mycelium by mitosis. Large numbers of haploid (n) spores are produced by mitosis. Asexual reproduction Mycelia of two different mating types fuse at their tips, and plasmogamy (fusion of cytoplasm) occurs. Spores germinate and form mycelia by mitosis. 1 2 Mycelia 6 Sexual reproduction Spores are released. Spores Haploid stage (n) Plasmogamy Dikaryotic stage (n + n) 5 Diploid stage (2n) Meiosis results in four genetically different haploid ( n ) nuclei. Spores develop around nuclei. 3 Dikaryotic (n + n) mycelium develops. Zygote nucleus (2n) Dikaryotic mycelium Meiosis Karyogamy Karyogamy (fusion of nuclei) occurs, forming a diploid (2 n ) zygote nucleus. 4 Fig. 26-4, p. 559

  27. KEY CONCEPTS • Most fungi reproduce both asexually and sexually by means of spores

  28. Learning Objective 4 • Support the hypothesis that fungi are opisthokonts, more closely related to animals than to plants

  29. Flagellate Cells • Animals and fungi have flagellate cells • Example: chytrid gametes and spores • Flagellate cells propel themselves • with single posterior flagellum

  30. Platelike Cristae • Like animal cells, fungal cells have platelike cristae in their mitochondria

  31. Opisthokonts • Fungi are opisthokonts • along with animals and choanoflagellates • based on chemical and structural characters

  32. Fungal Evolution

  33. Basidiomycetes Glomeromycetes Zygomycetes Ascomycetes Chytrids Evolution of ascospores Evolution of basidiospores Evolution of dikaryotic stage Loss of flagellum Common flagellate ancestor Fig. 26-5, p. 560

  34. Learning Objective 5 • Support the hypothesis that chytrids may have been the earliest fungal group to evolve from the most recent common ancestor of fungi

  35. Chytrids (Chytridiomycetes) • Produce flagellate cells during life cycle • no other fungi have flagella • Probably earliest fungi to evolve from flagellate protist • common ancestor of all fungi

  36. Chytrid

  37. 5 µm Fig. 26-6, p. 561

  38. Learning Objective 6 • List distinguishing characteristics, describe a typical life cycle, and give examples of each of these fungal groups: • chytridiomycetes • zygomycetes • glomeromycetes • ascomycetes • basidiomycetes

  39. Chytrids 1 • Reproduce both asexually and sexually • Gametes and zoospores are flagellate • Allomyces • part of life is multicellular haploidthallus • part is multicellular diploidthallus

  40. Chytrids 2 • Haploid thallus produces 2 types of flagellate gametes that fuse • Both plasmogamy and karyogamy occur • producing flagellate zygote

  41. Chytrids 3 • Diploid thallus bears zoosporangia • produce diploid zoospores, resting sporangia • in which haploid zoospores form by meiosis • Haploid zoospores form new haploid thalli

  42. Chytrid Life Cycle

  43. Glomeromycetes Basidiomycetes Ascomycetes Zygomycetes Chytrids Common flagellate ancestor Fig. 26-7a, p. 562

  44. Mature haploid thallus Haploid thallus produces two types of gametes by mitosis. Sporangium 2 1 Haploid zoospore Gamete type A Haploid zoospore grows into haploid thallus. Gamete type B 6 Haploid zoospores are produced by meiosis. SEXUAL REPRODUCTION HAPLOID (n) GENERATION Gametes fuse and their nuclei fuse, producing flagellate zygote. Resting sporangium 3 DIPLOID (2n) GENERATION Plasmogamy and karyogamy Meiosis 5 Resting sporangium Motile zygote Meiosis occurs in resting sporangia. Zoosporangium Zygote germinates and develops into diploid thallus. 4 Zoosporangia produce flagellate diploid zoospores by mitosis. Zoospores give rise to new diploid thalli. ASEXUAL REPRODUCTION (by mitosis) 7 Diploid zoospore Fig. 26-7b, p. 562

  45. Zygomycetes1 • Rhizopus (black bread mold) • forms haploid thallus • produces asexual spores and sexual spores • Asexual spores germinate • form new thalli

  46. Zygomycetes2 • In sexual reproduction • hyphae of 2 different haploid mating types form gametangia • Plasmogamy occurs • as gametangia fuse

  47. Zygomycetes 3 • Karyogamy occurs • diploid zygote forms • from which zygospore develops • Meiosis • produces recombinant haploid zygospores

  48. Zygomycetes 4 • When zygospores germinate • each hypha develops a sporangium at its tip • Spores are released • develop into new hyphae

  49. Zygomycete Life Cycle

  50. Glomeromycetes Basidiomycetes Ascomycetes Zygomycetes Chytrids Common flagellate ancestor Fig. 26-9a, p. 564

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