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Bizarre Facts in Biology Just When You Thought It Was Safe

by Sylvester Allred

Chapter 20: The Diversity of Fungi

Right now in soil near you, a microscopic biotic drama is being played out. In the lead role is a predaceous fungus, and the supporting role belongs to its prey, the nematodes (roundworms) ().

Predaceous fungi () spread their mycelium throughout the soil like a tangle of octopus arms. Nematodes slither blindly through the soil, occasionally bumping into the mycelium—a chance meeting in total darkness. It could be a chemical in the soil that attracts the nematodes or just a chance encounter; nonetheless, once the nematode encounters the fungus, the worm becomes entrapped. These predaceous fungi have several methods, depending on the species, by which to snare their next meal. Some species have rings on their mycelia that constrict their prey. The constricting rings are like tiny lassos through which an unknowing nematode crawls. Cells in the ring swell, closing the noose. Other species use branched hyphae with adhesives for capturing prey. As you can see, not all predators have teeth, sharp claws, hooked talons, or even vision.

After capture, the fungus sends threads of hyphae into the nematode’s body and begins the process of digestion. The mode of nutrition in which an organism obtains its food from another source is called heterotrophy. The nematode’s proteins, carbohydrates, and fats are broken down into usable products for the fungus. Life thus recycles.

Related Concepts

Evolutionary Connections: The Nematode Nemesis in Chapter 20.

What Are the Results of Interactions Between Predators and Their Prey? in Chapter 40.

1. There is an ever-escalating "arms race" in nature; for example, a plant produces a chemical to deter being eaten by an insect—the insect evolves a chemical to detoxify the plant. How might nematodes avoid predatory fungi? What would need to take place from an evolutionary perspective?

2. Speculate as to how a fungus, which normally processes material that is no longer living (such as a dead tree), could become so specialized as to feed on nematodes?

3. What are some downsides to this fungal specialization?

Web Investigations Humongous Fungus

Chapter 20: The Diversity of Fungi

Estimated time: 10 minutes

The case study that begins this chapter features the humongous fungus Armillaria ostoyae. The finding of these giant fungi (Oregon, Washington, and Michigan all tout their humongous fungi!) has provided forest management () people with new insights into how humans impact forests and the management of forests. The Armillaria fungus is now known to be a natural participant in a forest ecosystem. Its spread is not worsened by the suppression of forest fires by humans as was once believed.

The Oregon fungus was not the first humongous fungus to be identified. In 1992, the fungus Armillaria bulbosa () (now more correctly classified as Armillaria gallica) was identified in Michigan. Extensive genetic comparisons showed conclusively that the 37-acre fungus was in fact one organism.

Although the Michigan humongous fungus is really located in a different township, Crystal Falls, MI (), claims it as their own. Every September, Crystal Falls celebrates its famous fungus with a Fungus Fest where you can get a fungus burger or fungus fudge! If you plan to see the fungus while you're there, prepare to be disappointed because it is mostly underground and out of sight.

1. What tree species should be considered for replacement of trees removed during harvesting?

2. What type of genetic information was examined to demonstrate the Michigan fungus was one organism?

3. What late night show host had some fun with the Michigan humongous fungus? According to the host in question, what does the fungus taste like?

Issues in Biology Where Have All the Fungi Gone?

Chapter 20: The Diversity of Fungi

In the Earth Watch of this chapter the issue of disappearing fungi is addressed. Lest you shrug this off as of little concern, consider that many of the fungi that are disappearing live symbiotically with plants (mycorrhizae). The relationship between plants and fungi benefits both organisms. The heterotrophic fungi obtain sugars produced by the photosynthetic activities of the plants. In turn, the fungi provide the plants with additional nutrients from the soil.

Plants involved in mycorrhizae grow better than plants that are not (see the comparison picture in chapter 24 of your textbook). Some plants, like orchids (), are dependent on their fungal partners for survival. Cultivation of some plants like the Pink Ladyslipper orchid () is futile because of the poorly understood relationship between the orchid and its fungal partner. Attempts to restore endangered plant species () may fail without the presence of the proper fungal species.

Plants aren’t the only organisms dependent on their fungal partners. Some animals like the endangered northern flying squirrel () rely on mycorrhizae for food. The truffles that the squirrels consume form mycorrhizae with specific plant species.

1. If the fungi involved with orchid seeds are eliminated, what do you predict will happen to the seeds? How will the population of orchids be affected?

2. Will fungi form mycorrhizae with just any kind of plant?

3. If the spruces in the Southern Appalachians were removed and replaced with pines, what do you predict would happen to the northern flying squirrels?

Chapter 20: The Diversity of Fungi Thinking Through the Concepts

1. Describe the structure of the fungal body. How do fungal cells differ from most plant and animal cells?

2. What portion of the fungal body is represented by mushrooms, puffballs, and similar structures? Why are these structures elevated above the ground?

3. What two plant diseases, caused by parasitic fungi, have had an enormous impact on forests in the United States? In which division are these fungi found?

4. List some fungi that attack crops. To which phyla do they belong?

5. Describe asexual reproduction in fungi.

6. What is the major structural ingredient in fungal cell walls?

7. List the phyla of fungi, describe the feature that gives each its name, and give one example of each.

8. Describe how a fairy ring of mushrooms is produced. Why is the diameter related to its age?

9. Describe two symbiotic associations between fungi and organisms from other kingdoms. In each case, explain how each partner in these associations is affected.

Chapter 20: The Diversity of Fungi Applying the Concepts

1. Dutch elm disease in the United States is caused by an exotic—that is, an organism (in this case, a fungus) introduced from another part of the world. What damage has this introduction done? What other fungal pests fall into this category? Why are parasitic fungi particularly likely to be transported out of their natural habitat? What can governments do to limit this importation?

2. The discovery of penicillin revolutionized the treatment of bacterial diseases. However, penicillin is now rarely prescribed. Why is this? Hint: Refer back to Chapter 15.

3. The discovery of penicillin was the result of a chance observation by an observant microbiologist, Alexander Fleming. How would you search systematically for new antibiotics produced by fungi? Where would you look for these fungi?

4. Fossil evidence indicates that mycorrhizal associations between fungi and plant roots existed in the late Paleozoic era, when the invasion of land by plants began. This evidence suggests an important link between mycorrhizae and the successful invasion of land by plants. Why might mycorrhizae have been important fungi in the colonization of terrestrial habitats by plants?

5. General biology texts in the 1960s included fungi in the plant kingdom. Why do biologists no longer consider fungi as legitimate members of the plant kingdom?

6. What ecological consequences would occur if humans, using a new and deadly fungicide, destroyed all fungi on Earth?

Chapter 20: The Diversity of Fungi Essay Challenge

1. In the previous chapter, you learned about organisms in the domain bacteria and the kingdom protista. Compare and contrast those organisms with the fungi covered in this chapter. Your answer should include physical characteristics and the importance of them to other living things.

2. What is the advantage to making spores as a reproductive strategy?

3. What are the four phyla of fungi? How are they similar? Different?

4. With what other organisms can fungi live in mutually beneficial relationships? How does the fungus benefit from these relationships?

 

5. Based on the discovery that in lichens with algal symbionts the fungal hyphae penetrate the algal cell walls just like fungi that parasitize plants, and on the knowledge that fungi may use up to 90% of the algae's sugars, is it reasonable to refer to lichens as mutually beneficial relationships?

6. While scratching his athlete’s foot, a friend says that fungi are aggravating and that humans would be better off without them around. What will you tell your friend to convince him/her that the loss of fungi would be devastating to humans?

7. What fungal activities support the notion that your muscle proteins may contain nitrogens that were once a part of the muscle proteins of a Tyrannosaurus rex?

8. In this chapter and the previous one, you learned about the organisms that do the incredibly important job of decomposition (breaking down dead bodies). What organisms from this chapter and the previous one perform this all-important job of decomposition? Why would the ecosystems in which these organisms are found cease to function without them?

Chapter 20: The Diversity of Fungi Figure Caption Questions and Answers

Figure 20-1 The filamentous body of a fungus

Question: Which features of a fungus's body structure are adaptations related to its method of acquiring nutrients?

Figure 20-6 The life cycle of a typical basidiomycete

Question: If two spores from the same sporangium each germinate, and the resulting hyphae come into contact, can sexual reproduction follow?

Figure 20-7 Diverse basidiomycetes

Question: Are the structures shown in these photos haploid or diploid?

Figure 20-15 Penicillium

Question: Why do some fungi produce antibiotic chemicals?

1. Organisms classified as fungi:

a. are autotrophic. b. absorb their food nutrients after performing extracellular digestion.

c. have cell walls with cellulose. d. produce embryos during sexual reproduction.

e. All of these are correct.

2. One of the more important characteristics used in the classification of fungi is its form of _______. Fungi that lack this characteristic are classified in the group _________.

a. asexual reproduction; lichens b. sexual reproduction; deuteromycetes

c. mycelium; Chytridiomycota d. septa; Zygomycota

3. Many plants form a symbiotic relationship between the plant root and fungi. These fungi are called _______ and benefit the plant by supplying _________ to the plant.

a. mycorrhizae; organic nutrients b. rusts; carbohydrates

c. imperfect fungi; proteins d. cup fungi; cytoplasm

4. Sexual reproduction in the Zygomycota life cycle includes which of the following sequences of events?

a. The haploid zygospore reproduces by meiosis to form haploid spores that grow by meiosis to form the diploid mycelium.

b. The diploid zygospore reduces by meiosis to form haploid spores that will produce a haploid mycelium through mitosis.

c. Haploid gametes divide by meiosis to produce a diploid zygote that grows by mitosis, producing a diploid mycelium.

d. Free-swimming gametes fuse to form a diploid zygote that grows by mitosis into a diploid mycelium.

5. Fungi that form zygospores after the fusion of two hyphae are classified into the _____ phylum.

a. ascomycetes b. deuteromycetes c. zygomycetes

d. basidiomycetes e. chytrids

1. A lichen is an association between a fungus and a(n):

a. algae or photosynthetic prokaryote. b. nonphotosynthetic bacterium.

c. green plant. d. unicellular fungus-like plant.

2. The function of the algal component of a lichen is to:

a. break down dead tissues. b. provide support or protection.

c. transfer pollen. d. make food via photosynthesis.

e. ferment sugars and produce alcohol.

3. The mushrooms on the pizza you might have eaten last night belong to the phylum:

a. Zygomycota. b. Basidiomycota. c. Deuteromycota d. Ascomycota.

4. When the zygospore undergoes meiosis, _____ are produced.

a. zygotes b. sporangia c. swimming spores d. asci e. mushrooms and puffballs

5. The fungi which cause black bread mold belong to the phylum:

a. Deuteromycota. b. Basidiomycota. c. Zygomycota. d. Ascomycota.

6. The underground body of a fungus is called a:

a. mushroom. b. hypha. c. mycelium. d. zygospore. e. lichen.

7. Basidia undergo _____ to produce haploid basidiospores.

a. meiosis b. fertilization c. mitosis d. pollination

1. If you examined the structure of the body of a typical fungus you would find:

a. a mass of round cells called coccae, which form a long chain of cells connected by chitin.

b. a mass of square cells called hexae, which are clumped together, forming the structures we observe on rotting organic material.

c. a mass of flattened cells called squamae, which are stacked on top of each other, forming a mass called a mycelium.

d. a mass of threadlike cells called hyphae.

2. The fungal spores resulting from sexual reproduction are produced after:

a. the mycelia of two compatible mating types fuse.

b. the septa between hyphal cells break down and allow the nuclei to fuse.

c. a male mycelium encounters a mature female mycelium.

d. the mycelium encounters a favorable environment for growth.

3. Which of the following is an important function of fungi?

a. Yeasts perform alcoholic fermentation that produces CO2 which makes bread rise.

b. Some fungi recycle nutrients when they decompose dead plant and animal bodies.

c. Some fungi produce antibiotics. d. All of these are important functions of fungi.

4. In the Basidiomycota and the Ascomycota, _______ produces _______ spores, which give rise to a new mycelium.

a. meiosis; diploid b. meiosis; haploid c. mitosis; diploid d. mitosis; haploid

5. Which of the following associations is incorrect?

a. zygomycetes – zygospores

b. basidiomycetes – fruiting bodies we identify as mushrooms, puffballs, and shelf fungi

c. deuteromycetes – absence of sexual reproduction

d. chytrids – lightweight windblown sexual spores

e. ascomycetes – asci

1. The spores of chytrids are unique because they are:

a. found in club-shaped reproductive structures called basidia b. flagellated.

c. lightweight windblown structures.. d. formed in a sac-like case called as ascus.

2. The sexual reproductive structures in the zygomycetes are the:

a. zygospores. b. sporangia. c. asci. d. basidia.

3. Which of the following describe the condition of the nuclei of zygospores?

a. The cells contain a single haploid nucleus. b. The cells contain two haploid nuclei.

c. The cells contain a single diploid nucleus. d. The cells contain two diploid nuclei.

4. Within the phylum Ascomycota, the sexually produced spores are:

a. in groups of four on small club-like structures. b. flagellated.

c. within a black ball-like structure between two hyphae of complementary mating types.

d. within elongated sac-like structures.

5. The basidia of a mushroom are located on or in its:

a. flagellum. b. asci. c. gills. d. zygospores.

6. The absence of sexual reproductive structures is associated with the:

a. basidiomycetes. b. zygomycetes. c. deuteromycetes/imperfect fungi.

d. ascomycetes. e. chytrids.

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