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EXAM 2 - General Mycology 427/527

Multiple Choice: Circle all the correct answers. There may be more than one correct answer. (0.5 points for each correct answer)

1. A tetrapolar mating system differs from a bipolar system because

a. there are two different mating type loci

b. the organism must be homothallic

c. for a mating to be successful you must have four different mating type alleles

d. it is unifactorial

e. a progeny strain will only be able to mate with 25% of its siblings instead of 50%

2. Water is essential for dispersal of

a. zoospores

b. the Chytridiomycota

c. the Oomycota

d. tetraradiate spores

e. airborne spores

3. Forcible discharge of fungal spores

a. can occur for both sexual and asexual spores

b. requires small spores.

c. is an important mechanism for coprophilic fungi to shoot their spores away from the dung on which they form

d. is when raindrops knock the spores out of a giant puffball

e. often occurs due to a build up of osmotic pressure in a vacuole causing it to burst

4. Constitutive dormancy is a condition that

a. is imposed on a spore by the environmental conditions

b. requires a trigger to break dormancy and allow spores to germinate

c. may be due to the presence of self-inhibitors of germination

d. requires the factors that allow for the breaking of dormancy to remain present for continued growth

5. The majority of fungal spores

a. are aerially dispersed

b. germinate and produce a mature fruiting structure

c. are zoospores

d. lack a cell wall

e. are embryos

f. are sexual spores

6. You are told that a cabbage field is dying due to a weird disease. You determine the plants were infected by Plasmodiophora brassicae because

a. the roots are swollen

b. you observe a pseudoplasmodium migrating from the plant roots

c. you are able to isolate and grow P. brassicae in petri dishes

d. you observe zoospores with one tinsel and one whiplash flagellum

e. you see a plasmodium without a cell wall in the roots

7. True slime molds differ from cellular slime molds by

a. producing a multicellular plasmodium

b. producing a plasmodium with diploid nuclei

c. having no aggregation stage

d. producing spores with cell walls

e. having a migrating slug stage

f. having both haploid and diploid feeding stages

8. A fruiting structure of the Myxomycota may be called

a. a myxameoba

b. a sporangium

c. a grex

d. a plasmodium

e. a plasmodiocarp

f. an aethalium

9. The Dictyosteliomycota and the Acrasiomycota both

a. produce haploid amoebae

b. produce a pseudoplasmodium with diploid cells

c. lack a cell wall on their pseudoplasmodium

d. more than doubles the number of cells they have while the pseudoplasmodium assimilates food

e. have both stalk cells and spore cells capable of germinating

f. have a migrating pseudoplasmodium stage

10. You have isolated a new fungus and think it is an oomycete. Which of the following characteristics that are present in all of the Oomycota help you confirm this?

a. biflagellate zoospores

b. it is an obligate pathogen

c. chitin in its cell walls

d. a diplanetic lifestyle

e. diploid nuclei in its hyphae

f. the zoospores are released from a vesicle that forms on the sporangium

11. The Saprolegniales differ from the Peronosporales by

a. being an order with many obligate plant pathogens

b. having multiple oospheres per oogonium

c. having both aerial and water dispersal of their sporangiospores

d. producing elongate instead of rounded sporangia

e. producing both primary and secondary zoospores

12. The genera Pythium and Phytophthora are both Oomycetes of the family Pythiaceae. You are given a fungal isolate which you are told is Phythophthora, but which, upon examination, you decide is Pythium. The criteria that could have led you to your conclusion was

a. you observe lemon-shaped sporangia

b. you see a vesicle form off of the sporangia in which the zoospores develop and from which they are released

c. the presence of indeterminate sporangiophores

d. aerial dispersal of the sporangia

e. you see club-shaped sporangiophores with chains of sporangia under the plant leaf epidermis

13. The order Chytridiales is thought to be less evolutionarily advanced than other orders of the Chytridiomycota because:

a. they have no sexual reproductive stage

b. members lack true mycelium

c. they are all saprobes, while the other orders contain many pathogens

d. they are all holocarpic

e. they contain cellulose in their cell walls

14. Rhizoids are

a. used to anchor some fungal thalli in the Chytridiomycota and Hyphochytriomycota

b. uninucleate structures

c. nutrient absorptive structures that penetrate a host cell wall, but not its plasma membrane

d. not found in holocarpic members of the Chytridiales

15. The Chytridiomycota are unique among organisms in the kingdom Fungi because

a. they have cellulose in their cell walls.

b. they have motile cells at some stage in their life cycle

c. contain several species that use a holocarpic mode of reproduction

d. they use DAP as an intermediate in their lysine biosynthetic pathway

e. the phylum contains an order that reproduces sexually by fusion between one motile and one non-motile gamete.

16. You look at a fungal specimen under the microscope and determine that it is a downy mildew (Peronosporaceae) not a white rust (Albuginaceae) because you see

a. haustoria penetrating the cell walls of their hosts

b. zoospores with a single whiplash flagellum

c. branched sporangiophores with sporangia coming out of stomates

d. club-shaped sporangiophores with chains of sporangia

e. multiple oospheres per oogonium

17. Achlya ambisexualis is said to be dioecious because

a. its has two oospheres per oogonium

b. it requires two hosts to complete its lifecycle

c. it produces two different hormones, antheridiol and oogoniol to induce sexual differentiation

d. it produces separate male and female thalli

18. Coelomomyces pathogens are said to be heteroecious because

a. they are self-sterile

b. they require both the mosquito larva and the copepod hosts to complete their life cycle

c. their cells have two different types of nuclei within them

d. their zoospores have two different types of flagella

True/False: Write true or false to the LEFT of each answer (1 point each)

1. For the Myxomycota, the diploid part of the lifecycle is necessary for production of sporangiospores

2. For the cellular slime molds, the diploid part of the lifecycle is necessary for production of sporangiospores

3. The Ceratiomyxales are unique among the Myxomycota because their spores are borne externally

4. An organism that uses eucarpic reproduction will be polycentric

5. cAMP induces plasmogamy of amoebae in the Dictyosteliomycota

6. Recombination between homologous chromosomes is rare during the parasexual cycle

7. A unique group of the Chtyridiomycota produce polyflagellate zoospores

8. Basidiospores rely on both forcible discharge and passive dispersal for their spread

Short Answers:

1. Why is it advantageous for coprophilus fungi to only rely on forcible discharge to disperse their spores? (2 pts)

2. Explain why the spores of a leaf pathogen are likely to be: (4.5 pts)

a. larger than average

b. hydrophobic

c. non-motile

3. What is the difference between a heterokaryon and a dikaryon? In your answer discuss the role both may play in producing genetic recombination. (3 points)

4. a. You have isolated a fungus that you observe is eucarpic, endobiotic and monocentric. What does this tell you about how its reproductive structures are formed and where it is found relative to its substrate? Draw an example of such a fungus. (3 pts)

4. b. You are able to see zoospores swimming that have a single flagellum, but cannot tell what type of flagellum it is. By observing the zoospores, how can you tell whether they are from the Hyphochytriomycota or the Chytridiomycota. What are two other features you can look for or test for that will allow you to determine which phylum your isolate is from? (2 pts)

c. You determine that your fungal isolate has rhizomycelium. What are these, and how do they differ from rhizoids and true mycelium? (2 pts)

5. Define and describe the relationship between an oogonium, an oosphere and an oospore of the Oomycota. In your answer, include information about the timing of meiosis, plasmogamy and karyogamy. You may include drawings. (4 pts)

6. Antheridiol and Oogoniol are two substances produced by the fungus Achlya ambisexualis. What are their roles in the A. ambisexualis.lifecycle (3 pts)

7. Here is the life cycle of a fungus-like

organism

a. Which phylum is the organism

from? (1 point)

b. Write the names of the structures

labeled 1 through 6, in the appropriate

blank below, write which are haploid,

and which are diploid, and whether each has (9 pts)

or lacks a cell wall.

Name of Structure Nuclear ploidy Cell wall?

1.

2.

3.

4.

5.

6.

b. Which are the assimilative structures in this life cycle? What does this mean? (2 pts)

c. Where does meiosis take place? (1 point)

8. Here is the life cycle of a

member of the Oomycota

a. What are the names of the structures

labeled 1-7? Which ones have

haploid nuclei and which ones

have diploid nuclei? (7 pts)

Name of Structure Nuclear ploidy

1.

2.

3.

4.

5.

6.

7.

b. What are two features of this life cycle that tell you it is

of the order Peronosporales and not Saprolegniales? (2 pts)

c. Where does meiosis take place? (1 point)

Definitions: (be concise) (1.5 points per definition)

exogenous dormancy

swarm cell

bipolar mating

plasmagel

diplanetic

operculum

isogamy

pseudoplasmodium

homothallic