CH 22 - Chapter 22 The Diversity of Fungi 22.1 What Are the...

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Chapter 22 The Diversity of Fungi
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22.1 What Are the Key Features of Fungi? Fungal bodies consist of slender threads Most fungi are multicellular Cells are surrounded by cell walls composed of chitin , a nitrogen-containing polysaccharide The body of almost all fungi is a mycelium , an interwoven threadlike filaments called hyphae Hyphae 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 Fungi cannot move, but grow rapidly in any direction within a suitable environment
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Author Animation: The Structure of Fungi
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The Filamentous Body of a Fungus Fig. 22-1 cell wall septum cytoplasm pore hyphae (b) Hyphae (c) Hypha cross-section (a) Mycelium
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Fungi obtain their nutrients from other organisms Fungi secrete enzymes outside their bodies and absorb the digested nutrients Fungal feed on dead organic material and wastes Fungal parasites absorb nutrients from cells of living hosts and may cause disease Some symbiotic fungi live in mutually beneficial relationships with other organisms Fungal predators consume living organisms Fungi reproduce by spores Spores are tiny reproductive packages capable of developing into adult fungi They are often produced in large numbers, and are dispersed by animals or air currents
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Nemesis of Nematodes Fig. 22-2 Fungal predator video (click me)
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roundworm part of a hypha that formed a noose-like ring around the worm
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Some Fungi Can Eject Spores Fig. 22-3 Spores being dispersed after a drop of water hits the fungus
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Most fungi can reproduce both asexually and sexually During asexual reproduction: Usually occurs under stable conditions, results in the rapid production of genetically identical clones During sexual reproduction: 2 different hyphae fuse so that the nuclei share a common cell The nuclei fuse to form a diploid zygote The zygote undergoes meiosis to form haploid sexual spores The spores germinate and develop into a new mycelium by mitosis Produces fungal bodies that are genetically distinct from either parent
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22.2 What Are the Major Groups of Fungi? Fungus species are classified into five phyla 1. Chytridiomycota (chytrids) 2. Zygomycota (zygomycetes) 3. Glomeromycota (glomeromycetes) 4. Basidiomycota (basidiomycetes) 5. Ascomycota (ascomycetes)
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Evolutionary Tree of the Major Groups of Fungi Fig. 22-4
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Table 22-1
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1. CHYTRIDS – Most chytrids are aquatic – They are distinguished from other fungi by forming flagellated spores that require water for dispersal – They reproduce both asexually and sexually Most feed on dead aquatic material Some 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 frogs Primitive chytrids are believed to have given rise to the other groups of modern fungi
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Fungal Spores Responsible for loss of species?
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Chytrid Filaments Fig. 22-5
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