Exam 29: Fungi

Use the following information to answer the question(s) below. For several decades now, amphibian species worldwide have been in decline. A significant proportion of the decline seems to be due to the spread of the chytrid fungus, Batrachochytrium dendrobatidis (Bd). Chytrid sporangia reside within the epidermal cells of infected animals, animals that consequently show areas of sloughed skin. They can also be lethargic, which is expressed through failure to hide and failure to flee. The infection cycle typically takes 4 to 5 days, at the end of which zoospores are released from sporangia into the environment. In some amphibian species, mortality rates approach 100 percent; other species seem able to survive the infection. -It has been hypothesized that fungi and plants have a mutualistic relationship because fungi provide critical nitrogen for the plants' use. How do we know this happens? In experiments using radioactively labeled ________.

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?

Which of the following characteristics is unique to chytrids compared to other groups of fungi?

Why does total biomass (graph e in the accompanying figure) not vary with AMF diversity?

Long, branching fungal filaments are called ________.

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

Use the following information to answer the question(s) below. 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 (A, B, C, and D), no AMF species (O), or all four AMF species together (A + B + C + D); 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. On the graphs below, 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. -Based on graphs in the accompanying figure, 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? Its biomass is greatest when ________.