Life Cycles

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Author:
HappyJedi7
ID:
140931
Filename:
Life Cycles
Updated:
2012-03-11 06:44:37
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Bio 244 lab
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Description:
Unit 10.8
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  1. Zygotic life cycle (general features)
    • observed in some algae, cellular slime molds, fungi
    • fusion of two haploid gametes (produced by haploid individuals, using mitosis) --> zygote undergoes meiosis to create haploid spore nuclei
    • unique feature to fungi: no gametes; plasmogamy not immediately followed by karyogamy
  2. Zygotic life cycle (fungi)
    • plasmogamy --> dikaryon state --> fruiting structures form --> in which karyogamy occurs
    • the spores are not released into the environment; liquid water not needed for fertilization (except for the chytrids, which have flagellated gametes)
    • karyogamy occurs long after plasmogamy has occured
  3. karyogamy
    • the fusion of the nuclei in fungi
    • occurs in the fruiting structures
    • occurs long after plasmogamy; the time between them depends on the species
  4. plasmogamy
    • fusion of two hyphae from two different individuals
    • of two mating types (+/-)
    • creates a dikaryon state (n+n; two distinct haploid nuclei)
  5. Gametic life cycle
    • observed in animals
    • produce haploid gametes using meiosis --> fuse together (syngamy/fertilization) to produce a diploid zygote --> undergoes mitosis to produce a multicellular adult
  6. Sporic life cycle (general)
    • oberved in some algae and in multicellular plants
    • typical of alternation of generations
    • two distinct different adults in the cylce
  7. alternation of generations
    • multicellular haploid adult (gametophyte)
    • multicellular diploid adult (sporophyte)
  8. Sporic life cycle (plants)
    sporophyte cells undergo meiosis --> produce haploid spores --> undergo mitosis to produce multicellular gametophyte --> undergo mitosis to produce gametes --> syngamy to form zygote --> undergoes mitosis to produce sporophyte
  9. spores
    • in both the zygotic and sporic life cycles can give rise directly to adult stages
    • long-lived
    • do not fuse with another spore
    • in fungi - spores are produced both mitotically and meiotically
    • in plants - spores are produced by meiosis (in sporphyte adult)
  10. gametes
    • must fuse with another gamete to produce zygote
    • short-lived
    • in plants (sporic life cycle) - gametes are produced by mitosis (in gametophyte adult)
    • in animals (gametic life cycle) - gametes are produced by meiosis

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