NAME:

QUIZ # 3

1. Described the common features of the organisms placed in the Deuteromycota, and how the classes and orders within this phylum are based on form? Explain why this phylum is decreasing in size even though more fungal species are being identified.

The organisms in the phylum Deuteromycota are those higher fungi that only have an anamorphic (asexual) stage. They lack a known sexual (teleomorphic) stage. The Deuteromycota is often referred to as a Form-phylum because the organisms are grouped based on form, and may not be the most closely related. As such, groupings are polyphyletic. The classes are defined based on first whether they produce hyphae (Coelomycetes and Hyphomycetes) or are yeast-like (Blastomycetes), and if they do produce hyphae, whether the conidiophores and conidia occur in structures (pycnidia and acervuli) (the Coelomycetes) or not the Hyphomycetes). Orders are based on the type of structure for one class (the Coelomycetes), and on whether or not they produce conidia, or only hyphae for the class lacking asexual spore-bearing structures (the Hyphomycetes).

The phylum is decreasing in size primarily because organisms are being re-classified into the Ascomycetes, or some into the Basidiomycetes, based on their molecular phylogenetic relatedness to other species already in those phyla. Some already do not recognize this group as a separate phylum (eg. Kendrick, author of the Fifth Kingdom)..

2. Draw and compare an ascocarp vs. a basidiocarp, included the nuclear content of the hypha forming these sporocarps, name the fertile layer where their respective sexual spores are formed.

3. Explain why Neurospora has been used as a genetic model system.

Neurospora crassa has been used as a genetic model system because it is able to grow on a chemically defined medium, crosses are straightforward, and all of the products of a meiotic event can be isolated (8 ascospores in one ascus) and their phenotypes scored. Finally, with N. crassa (and many other ascomycetes), mutants are easy to isolate and identify because one can isolate a large number of haploid asexual spores, subject them to mutagenesis and then score them for growth defects.

4. Draw the structure of a generic mushroom, include the Pileus, Scales, Gills, Annulus, Stipe and Volva, and explain from what tissue they developed from.

Scales- developed from the universal veil

Pileus (cap) –developed from mass of differentiated mycelia that makes up the basidiocarp

Gills- developed from immature hymenium

Annulus- developed from the partial veil

Stipe- developed from mass of differentiated mycelia, like the pileus

Vulva- developed from the universal veil

5. Why are Uredinales and Ustilaginales known as Teliomycetes? Explain what feature of karyogamy is different in this class when compared to the rest of the basidiomycetes.

The class Teliomycetes is used to define these plant pathogenic organisms because they differ from other basidiomycetes by having a teliospore stage. The teliospore is a thick-walled resting spore that is usually an overwintering stage for these fungi. The teliospore is the site of karyogamy in this group, instead of the basidium which is the site of karyogamy in the rest of the basidiomycetes. When the teliospore germinates, its nuclei migrate into the basidium and then undergo meiosis and basidiospores are produced.