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Ch. 29 - Fungi
Freeman - Biological Science 8th Edition
Freeman8th EditionBiological ScienceISBN: 9780138276263Non è quello che usi tu?Cambia libro di testo
Capitolo 29, Problema 14

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

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Extracellular digestion in Pilobolus begins when the mycelia secrete digestive enzymes onto the surface of the dung. These enzymes break down complex organic materials into simpler molecules outside the fungal cells.
The enzymes involved in this process include cellulases, proteases, and lipases, which target cellulose, proteins, and lipids respectively. This breakdown is crucial for converting the dung's nutrients into forms that the fungus can absorb.
Once the complex molecules are broken down into simpler compounds like sugars, amino acids, and fatty acids, these smaller molecules are absorbed by the fungal hyphae through their cell walls.
The absorption of nutrients allows Pilobolus to grow and extend its mycelia throughout the dung, utilizing the available resources for energy and growth.
This process of extracellular digestion and nutrient absorption is essential for the survival and reproduction of Pilobolus, enabling it to thrive in its unique ecological niche.

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Extracellular Digestion

Extracellular digestion is a process where organisms secrete enzymes into their environment to break down complex molecules into simpler ones that can be absorbed. In fungi like Pilobolus, this involves releasing enzymes onto the substrate, such as dung, to decompose organic material externally before absorbing the nutrients.
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Digestion and Digestive Tracts

Fungal Mycelium

Mycelium is the vegetative part of a fungus, consisting of a network of fine white filaments called hyphae. In Pilobolus, the mycelium grows through the substrate, such as dung, and plays a crucial role in nutrient absorption after extracellular digestion has broken down the organic matter.
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09:57
Fungi - 2

Role of Enzymes in Fungi

Enzymes are biological catalysts that speed up chemical reactions. In fungi, enzymes like cellulases and proteases are secreted to break down cellulose and proteins in the substrate. This enzymatic activity is essential for the digestion process, allowing fungi to access nutrients necessary for growth and reproduction.
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09:57
Fungi - 2
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Domanda del libro di testo

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?

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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.

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Domanda del libro di testo

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.

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Domanda del libro di testo

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.

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

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