Study questions - The Ascomycota and Deuteromycota

Ascomycota Questions

1. What are the ways that the Ascomycota reproduce asexually? Why is asexual reproduction important? Would you expect the ways in which asexual reproduction takes place in Ascomycota to differ from that of Deuteromycota? Why?

2. List and describe the four methods of sexual reproduction (plasmogamy) in the Ascomycota.

3. In the Ascomycota there is a delay of karyogamy after plasmogamy. What is the consequence or result of this delay? In your answer, explain whether from a single karyogamy event, you will get a single meiotic event or may have multiple meioses.

4. In Saccharomyces, which has single cells during its somatic phase, there in no extended dikaryon. Why? Might there be an extended diploid stage? Explain your answer.

5. What are spermatia? Explain their importance in the life cycle of Ascomycota.

6. What is the difference between a bitunicate and a unitunicate ascus? Which classes of the Ascomycota (based on ascocarp type) have bitunicate and which have unitunicate asci?

7. Ascus formation in many Ascomycota involves formation of a dikaryon, a crozier, karyogamy, meiosis and mitosis. Describe the sequence of these events and ascospore formation.

8. Asci may contain one, 4, 8 or thousands of ascospores.

• Explain how an ascus could have these different numbers of spores. Specify how 1,4, 8 or 1000 may form.
• Explain why each ascus represents a unique recombination event, and within a single ascocarp (eg. perithecium, apothecium, cleistothecium, pseudothecium), there may be over 100 different genetic recombination events occuring.
  

9. Ascomycota have been separated into Classes according to the type of ascocarp they have.

• a. Name, describe and draw these ascocarps and the classes that produce each type.
• b. Although convenient, division of the Ascomycota into classes by this method is not used by the Tree of Life Web project. Why not? Can you give some specific examples of the problem with classfication based on ascocarp type?
  

10. Taphrina is in the order Taphrinales and Saccharomyces is in the order Saccharomycetales . Although neither produces an ascocarp and thus by form are classified in the Hemiascomycetes, they are quite different. Describe the major ways in which these orders differ from each other.

11. Saccharomyces cerevisiae is diplobiontic, heterothallic, and budding. Explain these terms in relation to its life cycle.

12. Why is Saccharomycodes ludwiggi said to have a "short haploid" life cycle?

13. Are the Ascomycota a monophyletic or polyphyletic group? Why?

14. Some refer to the Ascomycota and the Basidiomycota collectively as the Dikaryomycota. Why do they do this?

Deuteromycota Questions

14. The Deuteromycota are called a "form" phylum and each sub-division within this form phylum also has the word "form" placed in front of it (ie. its genera called "form" genera) Why? What does this mean?

15. How does a sporangiospore differ from a conidium?

16. About 1900, Saccardo developed a way to classify the Deuteromycota. What criteria were used (describe all of them)? What criteria are used in the Hughes-Barron System?

17. The Deuteromycota have no sexual cycle. Still, it is possible to have genetic recombination in this phylum. Explain (hint, dig back to earlier lectures). Would genetic recombination in the Deuteromycota be as efficient as in the Ascomycota?

18. What are the different "form" classes in the Deuteromycota?
How are they differentiated?

19. Aspergillus and Penicillium are both "form" genera in the same form class, and they both reproduce asexually by the same mode. What is this mode called? By what means does one distinguish these two form genera? Use drawings to illustrate your point? They are very important fungi for humans. Name two products these fungi produce that are significant, or used by humans.

20. Definitions (Both Ascomycota and Deuteromycota):

perfect stage-
imperfect stage-
teleomorph-
anamorph-
ascogonium-
antheridium-
crozier-
trichogyne-
dikaryon-
pycnidium-
acervulus-
synnema-
sporodochium-
conidiophore-