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Ch. 29 - Fungi
Freeman - Biological Science 8th Edition
Freeman8th EditionBiological ScienceISBN: 9780138276263Not the one you use?Change textbook
Chapter 29, Problem 11

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.

Verified step by step guidance
1
Understand the life cycle of zygomycetes, which includes both asexual and sexual phases. The asexual phase involves the production of sporangia that release spores, as described in the problem.
Recognize that during the sexual phase of zygomycetes, the process involves the fusion of hyphae from two compatible mating types. This is a key characteristic of their sexual reproduction.
Identify the term 'zygosporangium' as a structure formed during the sexual phase of zygomycetes. It results from the fusion of hyphae and is crucial for sexual reproduction.
Compare the options provided in the problem: a) production of ascospores, b) production of basidiospores, c) production of motile sperm and eggs, and d) formation of a zygosporangium.
Determine that option d, 'Hyphae from two compatible mating types fuse and form a zygosporangium,' best describes the sexual phase of the life cycle of Pilobolus, a zygomycete.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Fungal Reproduction

Fungi can reproduce both sexually and asexually, with different structures and processes involved in each mode. Asexual reproduction often involves the production of spores in structures like sporangia, which can disperse and grow into new organisms. Sexual reproduction typically involves the fusion of specialized cells or structures from two compatible mating types, leading to genetic recombination and the formation of new fungal structures.
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Zygomycetes

Zygomycetes are a class of fungi characterized by their mode of sexual reproduction, which involves the formation of a zygosporangium. This structure is formed when hyphae from two compatible mating types fuse, leading to the development of a thick-walled zygospore. This zygospore can withstand harsh conditions and eventually germinate to produce new fungal growth, completing the sexual phase of the life cycle.
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Spore Dispersal Mechanisms

Fungi have evolved various mechanisms to disperse their spores effectively, ensuring their survival and propagation. The 'squirt gun' mechanism of Pilobolus is a fascinating example, where sporangia are forcibly ejected to land on fresh grass. This increases the likelihood of being ingested by herbivores, like cows, and subsequently deposited in a nutrient-rich environment, such as dung, where the spores can germinate and grow into new mycelium.
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Related Practice
Textbook Question

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.

Textbook Question

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.

Textbook Question

Many mushrooms are extremely colorful. One hypothesis is that the colors serve as a warning to prevent animals from eating mushrooms, much like the bright yellow and black stripes on wasps help to deter potential predators. Design an experiment to test this hypothesis.

Textbook Question

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.

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.

Textbook Question

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.

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

Textbook Question

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