Explain why fungi that degrade dead plant materials are important to the global carbon cycle. Do you accept the text's statement that, without these fungi, 'Terrestrial environments would be radically different than they are today, and probably much less productive'? Why or why not?

What does it mean to say that a hypha is dikaryotic?

a. Two nuclei fuse during sexual reproduction to form a zygote.

b. Two independent nuclei, derived from different individuals, are present in each cell.

c. The nucleus is diploid or polyploid — not haploid.

d. It is extremely highly branched, which increases its surface area and thus absorptive capacity.

Evaluate each of the following defects. Which could lead to uncontrolled growth in cancer? Select True or False for each statement. T/FThe overexpression of MPF activity. T/FA nonfunctional Rb protein. T/FThe overexpression of G1 cyclin. T/FA nonfunctional E2F protein.

The hyphae of arbuscular mycorrhizal fungi (AMF) form bushy structures after making contact with the plasma membrane of a root cell. What is the function of these structures?

a. They anchor the fungus inside the root, so the association is more permanent.

b. They increase the surface area available for the transfer of nutrients.

c. They produce toxins that protect the plant cells against herbivores.

d. They break down cellulose and lignin in the plant cell wall.

The Greek root ecto means 'outer.' Why are ectomycorrhizal fungi, or EMF, aptly named?

a. Their hyphae form tree-like branching structures inside plant cell walls.

b. They are mutualistic.

c. Their hyphae form dense mats that envelop roots but do not penetrate the cell walls.

d. They transfer nitrogen from outside their plant hosts to the interior.

Lignin and cellulose provide rigidity to the cell walls of plants. But in most fungi, chitin performs this role. Why is it logical that most fungi don't have lignin or cellulose in their cell walls?

Lawns are sometimes fertilized with nitrate that can be washed into neighboring woodlots by rain. If the trees in that woodlot are associated with EMF, what effect might the excess nitrate have on the fungi and/or trees?

a. Fungal growth may be stimulated, causing the trees to transport more nitrogen to the fungi.

b. The fungi may secrete more peptidases to break down the nitrate.

c. The trees may take up the nitrate directly into their roots and rely less on the fungi.

d. The excess nitrate may stimulate the fungi to transport more sugar to the trees.