Bio Exam 2 (Charts: Molds)

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  1. Oomycota: cell wall comp
    Cellulose/cellulose-like polymers
  2. Oomycota: structure
    • Unicellular
    • Highly branched,
    • coenocytic,
    • and filamentous (resemble hyphae of fungi)
  3. Oomycota: reproduction
    • Sexually : oogamous
    • Asexually: motile zoospore, with two flagella
    • Can be heterothallic or homothallic
  4. Oomycota: location/ movement
    • aquatic
    • terrestrial
  5. Oomycota: human relevance
    • Plasmopara viticola: caused downy mildew in grapes
    • Phytophthora infestans: caused late blight of potatoes
    • Gene is being engineered to resist the pathogens
  6. Plasmodial Slime Molds: Cell wall
    No cell wall; instead, it is a naked mass of protoplasm called the plasmodium
  7. Plasmodial Slime Molds: Structure
    When conditions are appropriate: thin, streaming, multinucleate masses of protoplasm that creep along like amoebas, engulfing and digesting bacteria, etc.

    • eukaryotic
    • Fan-shaped (veins going through them) with flowing protoplasmic tubules that are thicker at the base of the fan and spread out, branch, and become thinner toward their outer ends
    • Tubules consist of slightly solidified protoplasm through which more liquefied protoplasm flows rapidly
    • Foremost edge contains a thin film of gel separated from the substrate by only a plasma membrane and a slime sheath
  8. Plasmodial Slime Molds: Reproduction
  9. Plasmodial Slime Molds: Location
    • Any place that has adequate food supply and moisture—when in short supply, they migrate away or stop moving, dividing into small mounds which produces a sporangium
    • Does not like sunlight
    • Movement: moves in one direction, but some can stop and go the other direction
  10. Cellular Slime Molds: Cell wall
    Cellulose-rich ecell walls during part of ther life cycle
  11. Cellular Slime Molds: structure
    • Amoeba like
    • In starvation: individual cells aggregate to form a motile, sluglike mass
    • Uninucleate, haploid myxamoebas retain their individualityà form pseudoplasmodium (slug), which releases asexual spores after moving
  12. Cellular Slime Molds: Reproduction
    • Undergo a type of mitosis found in plants and animals, where the nuclear envelope breaks down; reproduce by cell division
    • They have centrioles
    • Asexual reproduction by spores
    • Sexual reproduction: results in formation of walled zygotes called macroccysts, which are formed by aggregations of myxamoebas that are smaller than those involved in formation of slugs
  13. Cellular Slime Molds: location/ movement
    • Litter-rich soils where they exist as free-living amoeba-like cells (myxamoebas)
    • Movement: aggregate by chemotaxis, migrating towards cAMP, which is secreted by the starved myxamoebas
  14. Oomycota: reproductive cycle
    • 1.       In the oomycetes,, one to many eggs are produced in the oogonia and the antheridia contains male nuclei
    • 2.       Fertilization results in formation of thick-walled zygote (oospore), which is the resting stage
  15. Plasmodial Slime Mold: Life history
    • young 2n sporangium with multinucleate protoplasm increases in number by mitosis --> protoplasm cleaved into spores with a 2n nucleus -->meiosisà haplophase: haploid spores --> release of protoplast as an amoeba or flagellated gamete--> plasmogamy--> karyogamy --> (a) binucleate microcyst or (b)
    • (b) Diplophase: 2n zygote--> forms the plasmodium --> (c) sclerotia or (d)
    • (d) formation of sporangium--> young sporangium--> mature sporangium
  16. Cellular Slime MOlds--> Life cycle in terms of cAMP
    • 1.       when starved, the myxamoebas aggregate towards cAMP, which is secreted by the starved myxamoebas
    • 2.       cAMP diffuses away from the cellsà concentration gradient
    • 3.       secreting cells release cAMP in waves (at least 3)
    • 4.       binding of cAMP triggers rearrangement of actin filaments, allowing the movement toward camp
    • 5.       they aggregate towards the center and their plasma membrane becomes stickyà stick together
    • a.       anterior end becomes stalk (dies by apoptosis)
    • b.      posterior end becomes top of stalk (dormant spores)à dispersed
  17. Cellular Slime Molds--> Sexual Reproductive Cycle
    1.       aggregations of myxamoeas that are roundà two haploid myxamoebas fuseà single large myxamoebaà zygote, which is phagocytic and eats all the myxamoebas, becoming a giant celà thick cell wall (rich in cellulose) is laid down around the giant cellà macrocyst
  18. Life Cycle of a Cellular Slime Mold
    sorocarp -->  spores --(germination) --> haploid myxamoeba --> (a) microcyst or (b) 

    (b) --(aggregation)--> giant mass of myxamoeba --> (c) macrocyst [with a giant cell wall secreted around it] or (d)

    (d) formation of pseudoplasmodium (cells start specializing) --> pseudoplasmodium development (anterior becomes stalk and posterior becomes spores)--> sorocarp [
    back to the beginning]
Card Set:
Bio Exam 2 (Charts: Molds)
2014-03-17 14:40:27
Plant Kingdom
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