Exam 31: Fungi

You decide to bake bread from scratch.Which of the following is required to make your dough rise?

Most coal was formed during the Carboniferous period.What is a reasonable hypothesis that explains this observation?

Why is it more difficult to treat fungal infections than bacterial infections in humans?

You want to run an experiment to determine if an organism is a fungus.You place the organism in a petri dish with a small piece of wood.Which of the following results would support your hypothesis that your unknown organism is indeed a fungus?

Use the following information when answering the corresponding question(s). Suzanne Simard and colleagues knew that the same mycorrhizal fungal species could colonize multiple types of trees.They wondered if the same fungal individual would colonize different trees,forming an underground network that potentially could transport carbon and nutrients from one tree to another (S.Simard et al.1997.Net transfer of carbon between mycorrhizal tree species in the field.Nature 388:579-82).Figure 31.2 illustrates the team's experimental setup.Pots containing seedlings of three different tree species were set up and grown under natural conditions for three years;two of the three species formed ectomycorrhizae (Douglas fir,birch)and the other (cedar)formed arbuscular mycorrhizae.For the experiment,the researchers placed airtight bags over the Douglas fir and birch seedlings;into each bag,they injected either carbon dioxide made from carbon-13 or carbon-14 (¹³CO₂ and ¹⁴CO₂,isotopes of carbon).As the seedlings photosynthesized,the radioactive carbon dioxide was converted into radioactively labeled sugars that could be tracked and measured by the researchers. Figure 31.2 Figure 31.3 -Simard et al(1997)further hypothesized that if reciprocal transfer did occur,it would be a source-sink relationship driven by photosynthetic rates.That is,if one seedling is in full Sun and the other in deep shade,there will be a net movement of carbon from the seedling in full Sun to the one in deep shade.If a shade was placed over the birch seedlings and the cedar,and the Douglas fir was left in full Sun,what result could Simard and colleagues expect?

Some fungal species can kill herbivores while feeding off of sugars from its plant host.What type of relationship does this fungus have with its host?

You are a forester charged with increasing productivity in a South American forest newly planted with pines from Oregon.You believe that the southern forest lacks the fungal diversity needed by the North American pines,and that this lack of fungi is affecting the pines' productivity,but you have no evidence to support your ideas.To count how many fungal species were present in the Oregon forest,which methodology would you choose?

Figure 31.5 Use the graphs in Figures 31.4 and 31.5 and the following information when answering the corresponding questions. Canadian and Swiss researchers (van der Heijden et al. ,1998),interested in factors affecting biodiversity,grew a variety of grassland plants in combination with one of four arbuscular mycorrhizal (AMF)species,no AMF,or all four AMF species together;and they measured plant growth under each set of conditions.All plant species were grown in each plot,so they always competed with each other with the only difference being which AMF were present.Use the graphs in Figure 31.5 to answer the questions that follow.Note that the x-axis labels indicate the number and identity of AMF species (bar 0 = no fungi;bars A-D = individual AMF species;bar A+B+C+D = all AMF species together).The y-axis indicates the amount (grams)of plant biomass for the species shown in italics above each graph.Graph (e)is the total biomass (grams)of all 11 plant species combined;graph (f)is the biomass of Bromus erectus plants only,separated from the total. Figure 31.4 Figure 31.5 -Why does total biomass (graph e Figure 31.5)not vary with AMF diversity?

Fungi have an extremely high surface-area-to-volume ratio.What is the advantage of this to an organism that gets most of its nutrition through absorption?

You observe the gametes of a fungal species under the microscope and realize that they resemble animal sperm.To which of the following group does the fungus belong?

Based on the idea that fungi have pores between their cell walls,which allow cytoplasm to move from one end of the mycelium to the other,which of the following hypotheses is the most plausible?

Figure 31.4 Use the following information when answering the corresponding question(s). There is much discussion in the media about protecting biodiversity,but does it really matter? Canadian and Swiss researchers wanted to know if the diversity of arbuscular mycorrhizal fungi (AMF)was important to the productivity of grasslands (M.G.A.van der Heijden,J.N.Klironomos,M.Ursic,P.Moutoglis,R.Streitwolf-Engel,T.Boler,A.Wiemken,and I.R.Sanders.1998.Mycorrhizal fungal diversity determines plant biodiversity,ecosystem variability and productivity.Nature 396:69-72).Specifically,they wanted to know if it mattered which specific AMF species were present,or just that some type of AMF was present.They grew various plants in combination with one of four AMF species,no AMF,or all four AMF species together;and they measured plant growth under each set of conditions.All plant species were grown in each plot,so they always competed with each other with the only difference being which AMF species were present.Use the graphs in Figure 31.4 to answer the questions that follow.Note that the x-axis labels indicate the number and identity of AMF species (bar 0 = no fungi;bars A-D = individual AMF species;bar A+B+C+D = all AMF species together).The y-axis indicates the amount (grams)of plant biomass for the species shown in italics above each graph. -Based on the graphs in Figure 31.4,which of the following plant species is most likely not to form mycorrhizal associations?

Figure 31.5 Use the graphs in Figures 31.4 and 31.5 and the following information when answering the corresponding questions. Canadian and Swiss researchers (van der Heijden et al. ,1998),interested in factors affecting biodiversity,grew a variety of grassland plants in combination with one of four arbuscular mycorrhizal (AMF)species,no AMF,or all four AMF species together;and they measured plant growth under each set of conditions.All plant species were grown in each plot,so they always competed with each other with the only difference being which AMF were present.Use the graphs in Figure 31.5 to answer the questions that follow.Note that the x-axis labels indicate the number and identity of AMF species (bar 0 = no fungi;bars A-D = individual AMF species;bar A+B+C+D = all AMF species together).The y-axis indicates the amount (grams)of plant biomass for the species shown in italics above each graph.Graph (e)is the total biomass (grams)of all 11 plant species combined;graph (f)is the biomass of Bromus erectus plants only,separated from the total. Figure 31.4 Figure 31.5 -What is the major difference between Bromus erectus (graph f)and the other plant species (graphs a-d)included in the study?

Which of the following is an important role for fungi in the carbon cycle?

Why is it important that ectomycorrhizal fungi (EMF)have peptidase enzymes?

Microsporidians are considered parasitic because of the ability to penetrate their host cells using this structure.

Figure 31.4 Use the following information when answering the corresponding question(s). There is much discussion in the media about protecting biodiversity,but does it really matter? Canadian and Swiss researchers wanted to know if the diversity of arbuscular mycorrhizal fungi (AMF)was important to the productivity of grasslands (M.G.A.van der Heijden,J.N.Klironomos,M.Ursic,P.Moutoglis,R.Streitwolf-Engel,T.Boler,A.Wiemken,and I.R.Sanders.1998.Mycorrhizal fungal diversity determines plant biodiversity,ecosystem variability and productivity.Nature 396:69-72).Specifically,they wanted to know if it mattered which specific AMF species were present,or just that some type of AMF was present.They grew various plants in combination with one of four AMF species,no AMF,or all four AMF species together;and they measured plant growth under each set of conditions.All plant species were grown in each plot,so they always competed with each other with the only difference being which AMF species were present.Use the graphs in Figure 31.4 to answer the questions that follow.Note that the x-axis labels indicate the number and identity of AMF species (bar 0 = no fungi;bars A-D = individual AMF species;bar A+B+C+D = all AMF species together).The y-axis indicates the amount (grams)of plant biomass for the species shown in italics above each graph. -Based on the van der Heijden et al.(1998)graphs in Figure 31.4,which of the following is the best description of the data supporting the idea that a plant species did not form mycorrhizae with a fungus?

Use the following information when answering the corresponding question(s). Suzanne Simard and colleagues knew that the same mycorrhizal fungal species could colonize multiple types of trees.They wondered if the same fungal individual would colonize different trees,forming an underground network that potentially could transport carbon and nutrients from one tree to another (S.Simard et al.1997.Net transfer of carbon between mycorrhizal tree species in the field.Nature 388:579-82).Figure 31.2 illustrates the team's experimental setup.Pots containing seedlings of three different tree species were set up and grown under natural conditions for three years;two of the three species formed ectomycorrhizae (Douglas fir,birch)and the other (cedar)formed arbuscular mycorrhizae.For the experiment,the researchers placed airtight bags over the Douglas fir and birch seedlings;into each bag,they injected either carbon dioxide made from carbon-13 or carbon-14 (¹³CO₂ and ¹⁴CO₂,isotopes of carbon).As the seedlings photosynthesized,the radioactive carbon dioxide was converted into radioactively labeled sugars that could be tracked and measured by the researchers. Figure 31.2 Figure 31.3 -Refer to Figure 31.2.Which of the following results would support Simard et al.'s (1997)hypothesis that fungi can move carbon from one plant to another? Hypothesis: Sugars made by one plant during photosynthesis can travel through a mycorrhizal fungus and be incorporated into the tissues of another plant.

At which stage of a basidiomycete's life cycle would reproduction be halted if an enzyme that prevented the fusion of hyphae was introduced?

This group of fungi has the ability to penetrate its host's cell wall,thus increasing the efficiency with which materials are passed from fungus to host.