Exam 2.4: Textbook

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  1. Ascomycetes:

    economical importance
    • a.      Most of the molds that cause food spoilage are these
    • b.      Causesome plant diseases, like powdery mildews and Panama disease of bananas; chesetnut blight; Dutch elm disease
    • c.       Many yeasts are ascomycetes
  2. Three major groups of ascomycetes
    • 1.      Three major groups:
    • Taphrinomycotina: dominated by yeasts

    Saccaromycotina: dominated by yeasts

    Pezizomycotina: largest and includes all filamentous ascoma-producing species (about 40% form lichens)
  3. Structure of ascomycetes
    • a.      Unicellular (yeasts)
    • b.      Filamentous
    •                                                                                                                                       i.      Hyphae have perforated septa, which allow cytoplasm and the nuclei to move from one cell to the next
    •                                                                                                                                     ii.      Hyphal cells of vegetative mycelium may be either uninucleate or multinucleate
    • 1.      Some are homothallic; others heterothallic
  4. Life cycle of the ascomycetes: Asexual

    Asexual takes place through formation of __that are __
                                                                                                                                          i.      __are formed from __, which are borne at the tips of modified hyphae called __
    1.      Unlike zygomycetes, which produce spores how, ascomycetes produce their asexual spores __
    • conidia 
    • multinucleate
    • Conidia 
    • conidiogenous cells
    • conidiophores
    • internally within a sporangium
    • externally as conidia
  5. Life cycle of ascomycetes: Sexual

    a.      Sexual involves formation of an __, a saclike structure within which __ are formed following meiosis
                                                                                                                                          i.      Because the __resembles a sac, the ascomycetes commonly are referred to as the __ 
    1.      Both __ and __ are unique
    • ascus
    • haploid ascospores
    • ascus 
    • sac fungi (cup fungi)
    • asci and scospores
  6. 1.      __ occurs within a complex structure composed of tightly interwoven hyphae—the __
    a.      Many __are __

    • Ascus formation
    • ascoma, or ascocarp
    • ascomata 
    • macroscopic
  7. What are the different forms an ascoma may be?
    a.      An ascoma may be open and more or less cup-shaped (apothecium); closed and spherical (cleistothecium), or spherical to flask-shaped with a small pore through which the ascospores escape (perithecium)
  8. 1.      __ develop on an inner surface of the __, called the __ 
    In the life cycle of a filamentous ascomycete, the mycelium grows out from a __ on a suitable substrate
                                                                                                                                          i.      Soon after the mycelium begins to __ by __
                                                                                                                                        ii.      Many generations of __are produced during the growing season and it is the __that are primarily responsible for __ and __the fungus
    • Asci 
    • ascoma
    • hymenial layer
    • germinationg ascospore
    • reproduce asexually
    • forming conidia
    • conidia 
    • conidia 
    • propagating and disseminating
  9. a.      Sexual reproduction, involving ascus formation, occurs on the __
                                                                                                                                          i.      The formation of __ precedes sexual reproduction
    Explain what happens?
    • same mycelium that produces conidia
    • multinucleate gametangia called antheridia and ascogonia

    The male nuclei of the antheridium passes into the ascogonium via the trichogyne which is an outgrowth of the ascogonium --> plasmogamy
  10.                                                                                                                                       i.      In the ascogonium, the male nuclei pair with __ within the common cytoplasm, but they do not __
    1.      __ now begin to grow out of the __
    a.      As these hyphae continue to develop, what happens; and cell division occurs in such a way that the resultant cells are __
    genetically different female nuvlei

    yet fuse with them

    Ascogenous hyphae


    compatible pairs of nuclei migrate into them

    dikaryotic (two compatible haploid nuclei)
  11.                                                                                                                                       i.      The asci form near the __ forms a hooked __, which allows the paired nuclei to __, one in the __and the other in the __
                                                                                                                                        ii.      Subsequent cell division occurs in such a way that the immature ascus contains a __
    • tips of the dikaryotic, ascogenous hypha
    • tip, or crozier
    • divide simultaneously
    • hypha 
    • hook
    • compatible pair of nuclei
  12. 1.      These two nuclei then fuse to form a __, the only one in the life cycle of the ascomycetes
    2.      Soon after __, the young ascus begins to __
    a.      The diploid nucleus then undergoes __, which is generally followed by one __, producing an ascus with __
    • diploid nucleus
    • karyogamy
    • elongate
    • meiosis
    • mitotic division
    • eight nuclei
  13.    i.      These haploid nuclei are then cut off in segments of the cytoplasm to form __
                                                                                                                                                                                                                ii.      In many ascomycetes, the ascus becomes __at maturity and finally bursts, doing what in the cup fungi and some of the perithecium-forming species
                                                                                                                                                                                                              iii.      The ascospores are propelled about __ from the ascus, but some species propel them as far as __; initiates __
    • ascospores
    • turgid 
    • releasing its ascospores explosively into the air 
    • 2 cm
    • 30 cm
    • airborne spore dispersal
  14. 1.      In yeasts, each haploid cell is capable of serving as a __, and two haploid cells sometimes fuse to form a __, which functions as an __
    a.      Meiosis occurs within the __
    b.      __ are produced per __, although in some, meiosis is followed by one or more __, resulting in greater numbers of __
    • gamete
    • diploid cell, or zygote
    • ascus
    • ascus
    • Four ascospores
    • ascus
    • mitotic divisions
    • ascospores
  15.                                                                                                                                       i.      In other yeasts, meiosis is sometimes __, and the zygote divides __to form a population of __ that reproduce __
    1.      Thus, some yeasts have both __
    a.      Diploid cells may undergo __and revert to the haploid condition
    • delayed
    • mitotically 
    • diplod cells
    • asexually by budding
    • haploid and diploid budding stages
    • meiosis
  16. 1.      In other yeasts, the __fuse in pairs immediately after they are formed; in this case, the ascospore is the __ in the life cycle which is diploid
    • ascospores 
    • only haploid cell
  17. 1.      The Asexual fungi are ascomycetes
    a.      DNA sequencing shows that fungi formally classified as __are asexual forms of Ascomycetes
    b.      Many fungi exhibit the phenomenon of __, in which genetically different nuclei occur together in a common cytoplasm
    • Deuteromycetes 
    • heterokaryosis
  18.                                                                                                                                       i.      The nuclei may differ because of __ or __ of genetically distinct __
    1.      Because genetically different nuclei may occur in different proportions in different parts of a mycelium, these sectors may have divfferent properties
    • mutation or fusion
    • hyphae
  19. a.      Among the asexual fungi, haploid nuclei that are genetically different often __-->diploid nuclei with __and new __ forms
                                                                                                                                          i.      Meiosis does not form the new haploid nucleus, but rather what does?
    • fuse
    • recombination 
    • haploid nuclei
    • a gradual loss of chromosomes, called haploidization
  20. 1.      __, __, and __ occur in sequence called __
    a.      These cycles add to genetic and evolutionary flexibility in fungi that lack a true sexual cycle
    • Plasmogamy, karyogamy, and haploidization
    • parasexuality
  21. a.      Commercial importance
                                                                                                                                          i.      Cellulose degrading enzymes produced by __-->give jeans stonewashed look; detergent; control fungi that attack crops
                                                                                                                                        ii.      Antibiotics: __
    b.      Disease:
                                                                                                                                          i.      __-->ringworm, athlete’s foot, etc
    • Trichoderma
    • penicillin
    • Dermatophytes
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Exam 2.4: Textbook
2014-03-10 22:59:14
Plant Kingdom
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