Name: KEY
Quiz
Two
1.
Are fungi which rely on forcible discharge to their spores likely to be
further dispersed than those that rely on passive release. Explain your answer (2 pts)
Passive Release. Those that rely on forcible
discharge are often only shot a short distance, while those that rely on
passive release are usually dry spores that travel long distances in air
currents. An example of forcibly
discharged fungi, are the coprophilous fungi that are shot beyond the ring of
repugnance in order to land on nearby vegetation for ingestion by
herbivores. Most cosmopolitan
fungi (ie Aspergillus, Penicillium or Rhizopus) are passively released. [An
exception are the basidiospores of the mushrooms which may travel a long
distance. They are forcibly discharged to get them between the gills and then
dispersed by air currents.
2. What
is the difference between constitutive and exogenous dormancy? What is required
to break each type of dormancy? (2pts)
Dormancy is a period of rest or minimal
metabolic activity. Constitutive
dormancy is when internal (or innate) properties of the spore impose dormancy
and it requires a “trigger” for the breaking of dormancy. Triggers we discussed
include heat shock, cold, and some chemicals.
Exogenous dormancy is dormancy imposed by unfavorable
environmental (external) conditions.
Exogenous dormancy is broken when favorable conditions for growth
return. Those conditions must
remain present for growth to continue.
3. For true slime molds, which stage(s) have cell
walls and which stage(s) lack cell walls? (0.5 points for each stage) What is the nuclear content of each of
these stages? (0.5 points for each correct answer)
Cell walls: microsclerotia (n),
sclerotia (macrosclerotia) (2n), spores (n), sporangia (2n)
No cell wall: myxamoebae (n), swarm cells (n), plasmodium stage (2n).
4.
Describe the
differences between a plasmodium and a pseudoplasmodium? (2 points)
Both structures lack cell walls and have
a “slimy” appearance because of this. A plasmodium is a multinuclear, acellular (single large cell
is acceptable answer) feeding stage of the Myxomycota. The nuclei in the
plasmodium are diploid.
A pseudoplasmodium is a multicellular
uninucleate structure of the Cellular slime molds composed of aggregated
haploid amoebae. It is not a
feeding stage.
Plasmodium Pseudoplasmodium
Diploid nuclei haploid
nuclei
Feeding (assimilative) not
feeding
Acellular multicellular
5. Name
a phylum that has a plasmodium stage and one that has a pseudoplasmodium stage.
(1 point each)
Plasmodium: Myxomycota,
Plasmodiophoromycota
Pseudoplasmodium: Dictyosteliomycota,
Acrasiomycota