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Chapter 30 Fungi: Recyclers, Killers, and Plant Partners. Biology 101 Tri-County Technical College Pendleton, SC. Fungi Characteristics. ALL are heterotrophic organisms with absorptive nutrition NO photosynthetic members of this kingdom

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Chapter 30 fungi recyclers killers and plant partners

Chapter 30 Fungi: Recyclers, Killers, and Plant Partners

Biology 101

Tri-County Technical College

Pendleton, SC

Fungi characteristics
Fungi Characteristics

  • ALL are heterotrophic organisms with absorptive nutrition

    • NO photosynthetic members of this kingdom

  • Some are saprobes that absorb nutrients from dead matter; others are parasites that absorb nutrients from living hosts; and some live in mutualism with other organisms

  • Unicellular and multicellular species

Characteristics cont
Characteristics, cont.

  • Cell walls (if present) possess complex polysaccharide chitin

  • Most fungi have complex body forms

  • All the fungi produce spores

    • asexual, sexual, or both

  • Only one phylum (Chytridioimycota) has spores or gametes that possess flagella

What a body
What a body…

  • Most fungi NOT unicellular but whether they can be called multicellular is questionable

  • Vegetative (feeding) body of fungus called a mycelium

  • Mycelium composed of rapidly growing individual tubular filaments called hyphae (hypha)

Body cont
Body, cont.

  • Within most hyphae, there is NO division into separate cells so organelles (even nuclei) can move around (COENOCYTIC HYPHAE)

  • May be more appropriate to call fungi “multinucleate”

  • Some hyphae are subdivided into cell-like compartments by incomplete cross walls called septa (septum)

  • Those with septa said to have SEPTATE HYPHAE

Body cont1
Body, cont.

  • Certain modified hyphae called rhizoids anchor members of Chytridiomycota to their substrate

  • Tubular body of fungus give it a unique relationship with its environment

  • Has enormous surface area-to-volume ratio which is marvelous adaptation to absorptive nutrition

  • Able to tolerate highly hypertonic environment and temperature extremes

Modes of reproduction
Modes of Reproduction

  • Asexual reproduction takes many forms

    • production of haploid spores within sporangia

    • production of naked spores at tips of hyphae (condia = dust)

    • Cell division by unicellular fungi (equal division or asymmetrical division = bud)

    • Fragmentation by simple breakage of the mycelium

Modes cont
Modes, cont.

  • Sexual reproduction rather unique because often NO morphological distinction between male/female individuals/structures

  • There is genetically determined distinction between two or more mating types

  • Individuals of same mating type cannot mate with each other but can mate with different mating type

  • This prevents self-fertilization

More on the modes yeehaw
More on the modes..yeehaw!!

  • In many fungi, zygote nuclei formed by sex reproduction ONLY diploid nuclei in life cycle

  • These nuclei undergo meiosis, producing haploid nuclei that wind up in spores

  • Haploid nuclei (either method) germinate and nuclei divide mitotically to produce hyphae

Enough on modes already
Enough on modes, already

  • Some use dikaryon stage to reproduce sexually

  • Plasmogamy, karyogamy, dikaryon, heterokaryon

  • No gamete cells, only gamete nuclei

  • These hyphae are neither 2N or N, but rather they are dikaryotic (N + N)

  • Dikaryosis most significant genetic peculiarity of fungi


  • Aquatic microorganisms with cells walls of chitin

  • Either parasitic or saprobic

  • Reproduce both asexually and sexually

  • Only fungi that have flagella at any life cycle stage

  • Allomyces is best example


  • Have coenocytic hyphae and produce NO motile cells

  • Zygote only diploid cell in life cycle

  • Rhizopus stolonifer is black bread mold (and will hide on the onions…)

  • Can reproduce asexually and sexually


  • Distinguished by production of sacs called asci (sexual reproduction structure)

  • Septate hyphae

  • Divided into two groups on basis of asci

  • Euascomycetes (true) possess ascocarp (specialized fruiting structure that contains/protects the asci)

  • Hemiascomycetes (half) do NOT possess ascocarp

Ascomycetes cont
Ascomycetes, cont.

  • Hemiascomycetes are microscopic with many unicellular species

  • Saccharomyces cerevisiae (yeast)

  • Reproduce asexually by “budding”

  • Sexual reproduction produces ascospores

  • Euascomycetes include filamentous fungi known as the “molds”

Ascomycetes iii
Ascomycetes, III

  • Many (euascomycetes) are parasites (Chestnut blight/Dutch Elm disease)

  • Also includes the cup fungi: morels and truffles

  • Penicillium (antibiotic/Chamembert & Roquefort)

  • Asperigillus (soy sauce/sake/aflatoxins

  • **Reproduce asexually by means of condia and sexually by a dikaryon


  • Club fungi that includes puff balls, bracekt fungi, commercial mushrooms, some parasites, and some symbionts

  • Usually have septate hyphae

  • Basidium (swollen cell at tip of hyphae) characteristic sexual reproductive structure

  • Basidiospores contains spores

  • Some have cap (pileus) which has gills on underside

  • Great numbers of basidia develop on gills

Let s talk sex but quietly
Let’s talk sex..but quietly

  • Zygomycota reproduce sexually when adjacent hyphae of two different mating types release pheromones which cause them to grown together

  • These hyphae produce gametangia that fuse to form zygosporangia containing zygospores

  • Zygosporangia develop thick, multilayered walls that protect the zygospores

Zygomycota cont
Zygomycota, cont.

  • Highly resistant zygospores may remain dormant for months before their nuclei undergo meiosis and a sporangium sprouts

  • Sporangium contains product of meiosis—haploid nuclei that are incorporated into spores

  • Spores disperse and geminate to form new generation of haploid hyphae


  • Enough on budding already…

  • Sexual reproduction includes formation of dikaryon

  • Nuclei from male structure on one hypha enter female making structure on hypha of compatible mating type

  • Dikaryotic ascogenous (asci-forming) hyphae develop from dikarytoic female mating structure

Ascomycota cont
Ascomycota, cont.

  • Introduced nuclei divide simultaneously with host nuclei

  • Eventually asci form at tip of ascogenous hyphae

  • Only with formation of asci, do nuclei finally fuse

  • Nuclear division and meiosis of diploid nucleus takes place within individual asci

  • Meiotic products incorporated into ascospores that are ultimately released to begin new haploid generation


  • Basidiomycota are the “club fungi”

  • After nuclei fuse in basidium, diploid nucleus undergoes meiosis and four haploid nuclei are incorporated into haploid basidiospores which form on tiny stalks

  • Basidiospores typically forcibly discharged from basidia


  • Called the “imperfect” fungi

  • Mechanisms of sexual reproduction readily distinguish members of four phyla from one another

  • Many fungi, however, lack a sexual stage or their stage has NOT yet be identified

  • Fungi not yet classified in one of four phyla are placed together as “imperfect”

  • Is holding area for species whose sexual reproduction stage (if any) has not been identified


  • Mycorrhiza is mutualistic relationship between root hairs of plant and a fungus

  • Ectomycorrhizae: fungus wraps around root, >ing surface area for absorption of water and minerals

    • Mass of fungi (like sponge) help hold water in area of root

    • Infected roots branch extensively and become swollen and club-shaped

Mycorrhiza cont
Mycorrhiza, cont.

  • Endomycorrhizae: infection internal to root with no hyphae visible on root surface

  • Fungus obtains organic compounds from plant while increasing absorption of water and minerals (esp. phosphorus) by plant

  • Fungus may provide certain growth hormones and protect plant from attack by microorganisms

Mycorrhiza cont1
Mycorrhiza, cont.

  • Been suggested this relationship ALLOWED plants to survive move to land

  • Plants with active mycorrhizae are deeper green and may resist drought and temperature extremes between than plants of same species with little or no mychorrhizae development

  • Attempts to introduce plants to new areas have fialed until bit of soil from native land was provided


  • Lichen is mutualistic relationship between a fungus and a photosynthetic microorganism (cyanobacterium or green algae)

  • Are found in all sorts of exposed habitats

  • Important pioneer organisms and help in the soil cycle

  • Very sensitive to air pollution because they are unable to excrete toxic substances they absorb

  • Chattanooga, Tennessee