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Chapter 31

Chapter 31. Fungi. Characteristics. eukaryotic mostly multicellular, yeasts unicellular no locomotion sexual & asexual reproduction in most heterotrophic by absorption (digestion extracellular) > 100,000 species saprophytes (also parasites, mutualistic symbionts) some pathogenic

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Chapter 31

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  1. Chapter 31 Fungi

  2. Characteristics • eukaryotic • mostly multicellular, yeasts unicellular • no locomotion • sexual & asexual reproduction in most • heterotrophic by absorption (digestion extracellular) • > 100,000 species • saprophytes (also parasites, mutualistic symbionts) • some pathogenic • decomposers • classified by sexual reproduction • cell walls of chitin (polysaccharide)

  3. Structure • hyphae – rootlike structures for absorption which collectively form a network, mycelium • cell walls: • septate – with cross walls with large pores • aseptate(coenocytic)–no cross walls; multinucleate • haustoria – nutrient-absorbing threads that penetrate tissues of host in some parasitic types • hyphae may grow as fast as 1km/day • mycelia have haploid nuclei, some dikaryons- 2 separate nuclei that are dissimilar

  4. Fungal mycelia

  5. Cell wall types

  6. Figure 31.2x Septate hyphae (left) and nonseptate hyphae (right)

  7. Haustoria

  8. Reproduction • spores (usu. haploid), diploid in brief sexual reproductive cycles, then meiosis returns these to haploid • syngamy – nuclear union in fertilization usu. involves some form of conjugation • usu. asexually in optimal condtions, sexually in harsh conditions

  9. Generalized life cycle

  10. Classification Division Zygomycota – conjugation fungi -common molds, incl. Rhizopus stolonifer, Pilobilus ~600 sp. mostly terrestrial in soil or on decaying plants/animals -coenocytic hyphae -asexually produce sporangia -sexually by zygosporangia formed during conjugation (+ and – strains fuse)

  11. Zygomycete life cycle

  12. Conjugation

  13. Rhizopus

  14. Pilobilus

  15. Division Ascomycota– sac fungi ~30,000 sp. -yeasts (Saccharomyces, Candida), Peziza (cup fungus), morels, Ceratocystis ulmi – causes Dutch elm disease -septate hyphae -asexually by conidia on conidiophores -sexually by haploid ascospores in asci -most fungal symbionts in this group

  16. Ascomycete life cycle

  17. Peziza, truffle, morel

  18. Yeast

  19. Penicillium

  20. apothecia

  21. Division Basidiomycota – club fungi ~25,000 sp. -mushrooms, puffballs, shelf fungi -produce > 10 billion spores -septate hyphae -asexually none, or conidia in some -sexually by basidiospores in basidium

  22. Basidiomycete life cycle

  23. basidiomycetes

  24. Gills of a basidiomycete

  25. Stinkhorn,Phallis impudicus

  26. Amanita (death cap)

  27. Fairy ring

  28. Division Deuteromycota – imperfect fungi ~25,000 sp. -ringworm, athlete’s foot fungus, Arthrobotrys – prey on roundworms in soil -asexually by conidia -sexually none observed

  29. Symbioses 1) lichens – algae (filamentous green) – Chlorophyta or blue green (cyanobacteria) & fungus (ascomycete) -may reproduce asexually either from fragments or by dispersing tiny airborne starters, soredia

  30. Lichen structure

  31. each organism also reproduces either sexually or asexually • alga provides food for fungus, fungus provides moisture, minerals, protection to alga perhaps • thought to be more of a controlled parasitism, than mutualism

  32. Lichens • usu. given genus & specific name • 3 types: a) crustose – crusty b) foliose – leafy c) fruticose – shrubby *air pollutant indicators

  33. Crustose, fruticose, & folliose lichens

  34. Symbioses 2) mycorrhizae – plant roots & fungus -plant provides nutrients, fungus provides more surface area to absorb water -usu. basidiomycetes, may also be ascomycetes or zygomycetes *found in ~90% of tree species

  35. Benefits of mycorrhizae

  36. Mycorrhizae

  37. Importance Beneficial: • decomposers • food source • source of antibiotics • used in food and alcohol industries

  38. Fungal production of an antibiotic

  39. Importance Harmful: • decay products • cause disease • destroy crops • spoil food

  40. wheat rust, ergot on rye

  41. pink ear disease of corn

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