Explain how mold on a single piece of fruit can easily spread to nearby fruit.

Use the Chapter 2 dynamic spreadsheet Base Converter on our Web site to convert the base ten numbers 2400 and 2402 , which both have four digits, to a base seven number. What do you notice about the number of digits in the base seven representations of these numbers? Why is this?

Explain the process of extracellular digestion that occurs during the growth of $Pilobolus$ mycelia through dung.

Both asexual sporangia and zygosporangia can be found in cow dung. Make a simplified drawing that illustrates the events of plasmogamy, karyogamy, and meiosis that occur during sexual reproduction in $Pilobolus$. Be sure to indicate and label the zygosporangium.

Propose an experiment to test whether $Pilobolus$ shoots its sporangia preferentially toward light. Hypothesize why such a preference might be advantageous.

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.

Would you describe the association between $Pilobolus$ and cows as a symbiotic relationship? Explain your answer.

$Pilobolus$ is a zygomycete, and the sporangia just described produce asexual spores. In contrast, which of the following best describes what happens during the sexual phase of its life cycle?

a. It produces eight ascospores in each ascus.
b. It produces basidiospores that grow into mushrooms.
c. It produces motile sperm and eggs.
d. Hyphae from two compatible mating types fuse and form a zygosporangium.

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.

Angiosperms such as grasses, oaks, and maples are wind pollinated. The ancestors of these subgroups were probably pollinated by insects, however. As an adaptive advantage, why might a species "revert" to wind pollination? Why is it logical to observe that wind-pollinated species usually grow in dense stands containing many individuals of the same species? Why is it logical to observe that in wind-pollinated deciduous trees, flowers form very early in spring - before leaves form?

What trait(s) define(s) the vertebrates?

A) Jaws and a spinal cord.

B) Endoskeleton constructed of bone.

C) Notochord and a post-anal-tail.

D) Vertebrae and cranium.

Suppose that a gene originally identified in nematodes (roundworms) is found to be homologous with a gene that can cause developmental abnormalities in humans. Would it be possible to use fruit flies as a model organism to study this gene? Explain.

Which of these characteristics does not apply to cnidarians?

a. are diploblastic
b. possess a gastrovascular cavity with one opening
c. undergo metamorphosis
d. have a central nervous system

What determines the primary structure of a DNA molecule?

a. stem-and-loop configuration
b. complementary base pairing
c. deoxyribonucleotide sequence
d. hydrophobic interactions and hydrogen bonding