29. Fungi

What are homologous chromosomes? a. chromosomes that are similar in their size, shape, and gene content b. similar chromosomes that are found in different individuals of the same species c. the two chromatids in a replicated chromosome d. any chromosome in a diploid cell

Evaluate the following statements about mushrooms. Select True or False for each statement. T/F A diploid zygote is formed when a male spore fertilizes a female spore. T/F Haploid spores are formed by meiosis in basidia. T/F A mushroom is a reproductive structure that consists largely of dikaryotic cells. T/F Mushrooms are part of the group that also includes bracket fungi, boletes, puffballs, and stinkhorns.

What is an outcome of genetic recombination? a. the synapsing of homologs during prophase of meiosis I b. the new combination of maternal and paternal chromosome segments that results when homologs cross over c. the new combinations of chromosome segments that result when self-fertilization occurs d. the combination of a haploid phase and a diploid phase in a life cycle

What proportion of chromosomes in a man's skin cell are maternal chromosomes?

Nondisjunction that leads to problems in offspring can occur in: a. mitosis b. meiosis I only c. meiosis I and II d. mitosis, meiosis I, and meiosis II

If one species (2n=10) crosses with another species (2n=18), producing an allopolyploid offspring, what is the ploidy of the offspring? a. 2n=10 b. 2n=18 c. 2n=10 + 18=28 d. 4n=36 +20=56

Table 29.1 mentions that chytrids are responsible for massive die-offs currently occurring in amphibians. Review Koch's postulates; then design a study showing how you would use Koch's postulates to test the hypothesis that chytrid infections are responsible for frog deaths.

Some fungi have elaborate mechanisms for dispersing spores. For example, the 'squirt gun' fungus Pilobolus, which grows in cow dung, forcibly shoots off tiny black sporangia filled with spores. Any sporangia that are flung onto fresh grass are likely to be eaten by a grazing cow, passed through its digestive system unharmed, and deposited in a new batch of dung. The spores carried within the sporangia are perfectly positioned to grow into a new mycelium. 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.

Both asexual sporangia (shown in the photo) 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.

Select True or False for each statement. T/F Linked genes are always inherited together. T/F Genetic map distances measure the number of nucleotides between a pair of genes. T/F The farther apart genes are on a chromosome, the more likely there is to be a crossover between these genes during meiosis. T/F Crossing over occurs between genes on different homologs of a homologous chromosome pair.

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

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

Using high-speed video, researchers have measured several variables associated with sporangium discharge in various spore-shooting fungi. Based on the data in the table shown here, how do the launch speed and acceleration of Pilobolus compare with those of the other fungi? How does launch speed for each species compare with the top speed of 44 km/h reached by Jamaican athlete Usain Bolt during his 2009 world-record-setting 100-m race?

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