Fungi

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Fungi

• Chapter 31

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Fungi Characteristics

• Despite their diversity fungi share some key
  traits
• Fungi are heterotrophs but do not ingest their
  food
• Fungi secrete exoenzymes into their surroundings
  which break down molecules and then the fungi
  absorbs the remaining smaller compounds
• This mode of nutrition is related to the diverse
  lifestyles exhibited by fungi
• Decomposers, Parasites, Mutualistic symbionts

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Body Structure
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Specialized Hyphae

• Some unique fungi have specialized hyphae that
  allow them to penetrate the tissues of their host
• Mycorrhizae are mutually beneficial relationships
  between fungi and plant roots

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Reproduction in Fungi

• Fungi propagate themselves
• By producing vast numbers of spores, either
  sexually or asexually
• Spores can be carried long distances
• Only if they land in an acceptable area will they
  germinate and produce new mycelia

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Life Cycle of Fungi
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Sexual Reproduction

• The sexual life cycle involves
• Cell fusion, plasmogamy
• Nuclear fusion, karyogamy
• An intervening heterokaryotic stage
• Occurs between plasmogamy and karyogamy in which
  cells have haploid nuclei from two parents
• Sometimes can be dikaryotic and have two
  different, separate nuclei
• The diploid phase following karyogamy
• Is short-lived and undergoes meiosis, producing
  haploid spores

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Sexual Reproduction
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Asexual Reproduction

• Many fungi that can reproduce asexually
• Grow as mold, sometimes on fruit, bread, and
  other foods
• Clones are produced by mitotic production of
  spores
• Other asexual fungi are yeasts
• Which produce by simple cell division

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Types of Fungi
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The Phylogeny of Fungi

• Fungi can be placed into five major phyla based
  on morphological and molecular findings

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Chytrids

• Phylum Chytridiomycota
• Are found in freshwater and terrestrial habitats
• Can be saprobic or parasitic
• Unique to other fungi in having flagellated
  spores called zoospores

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Zygomycetes

• Considerable diversity of life histories
• Include fast-growing molds, parasites, and
  commensal symbionts
• Are named for their sexually produced
  zygosporangia
• Where karyogamy and meiosis occur

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Zygomycetes

• Some zygomycetes, such as Pilobolus
• Can actually aim their sporangia toward
  conditions with good food sources
• Zygosporangia are resistant to freezing and
  drying
• Are capable of persisting through unfavorable
  conditions
• Can undergo meiosis when conditions improve

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Ascomycetes

• Found in marine, freshwater, and terrestrial
  habitats
• Defined by the production of sexual spores in
  saclike asci, which are contained in fruiting
  bodies called ascocarps
• Commonly called sac fungi
• Vary in size and complexity

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Ascomycetes
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• Ascomycetes reproduce
• Asexually by producing asexual spores called
  conidia

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Basidiomycetes

• Mushrooms, shelf fungi, and
• some mycorrhizae and molds
• Some nasty plant parasites, rusts and smuts
• Are defined by a clublike structure called a
  basidium, a transient diploid stage in the life
  cycle
• Club fungus
• Important decomposers of
• wood and other plant material

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Basidiomycetes
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Basidiomycetes
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Lichens

• The ultimate symbiosis
• Algae and fungus
• The fungal component of a lichen
• Is most often an ascomycete
• Algae or cyanobacteria
• Occupy an inner layer below the lichen surface