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Fungi

1. Fungi can cause serious disease, primarily in plants.

2. Fungi produce useful food products.

Classification of Fungi (Table 12.3 and Figure 12.11)

1. Zygomycetes, Ascomycetes, Basidiomycetes, and Deuteromycetes or Fungi Imperfecti are the four groups of true fungi.

2. Chytridiomycetes are a close relative.

3. Yeast, mold, and mushroom are common terms that indicate morphological forms of fungi. (Figures 12.12,12.13, and 12.17)

4. Fungal filaments are called hyphae and a group of hyphae is called a mycelium. (Figures 12.15,12.16)

5. Dimorphic fungi can grow either as a single cell (yeast) or as mycelia.

Fungal Habitats

1. Fungi inhabit just about every ecological habitat and can spoil a large variety of food materials because they can grow in high concentrations of sugar, salt, and acid.

2. Fungi can be found in moist environments at temperatures from -6°C to 50°C and pH from 2.2 to 9.6.

3. Fungi are heterotrophs with enzymes that can degrade most organic materials.

Fungal Disease in Humans (Table 12.4)

1. Fungi may produce an allergic reaction.

2. Fungi may produce toxins that make humans ill. These include ergot, those in poisonous mushrooms, and aflatoxin.

3. Fungi cause mycoses such as histoplasmosis, coccidioidomycosis, and candidiasis.

Symbiotic Relationships Between Fungi and Other Organisms

1. Lichens result from an association of a fungus with a photosynthetic organism such as an alga or a cyanobacterium. (Figure 12.18)

2. Mycorrhizas are the result of an intimate association of a fungus and the roots of a plant.

Economic Importance of Fungi

1. The yeast Saccharomyces is used in the production of beer, wine, and bread.

2. Penicillium and other fungi synthesize antibiotics.

3. Fungi spoil many food products.

4. Fungi cause diseases of plants such as Dutch elm disease and wheat rust.

5. Fungi have been useful tools in genetic and biochemical studies.

Review Questions 321

12.4 Slime Molds and Water Molds (Figure 12.19)

1. Acellular and cellular slime molds are important links in the terrestrial food chain. (Figure 12.20)

2. Oomycetes, also known as water molds, cause some serious diseases of plants.

12.5 Multicellular Parasites: Arthropods and Helminths

Arthropods

1. Arthropods act as vectors for disease. (Table 12.5)

2. Mosquitoes spread disease by picking up disease-causing organisms when the mosquito bites, and later injecting these organisms into subsequent animals that it bites. (Figure 12.21)

3. Fleas transmit disease such as plague; lice can transmit trench fever, epidemic typhus, and relapsing fever. (Figure 12.22)

4. Ticks are implicated in Rocky Mountain spotted fever and Lyme disease.

5. Mites cause scabies, and dust mites are responsible for allergies and asthma. (Figure 12.23)

Helminths (Table 12.6)

1. Most nematodes or roundworms are free-living, but they may cause serious disease such as pinworm disease, whipworm disease, hookworm disease, and ascariasis.

2. Cestodes are tapeworms with segmented bodies and hooks to attach to the wall of the intestine.

3. Most tapeworm infections occur in persons who eat uncooked or undercooked meats; some tapeworms are acquired by ingesting fleas infected with dog or cat tapeworms. (Figure 12.24)

4. Trematodes, or flukes, often have complicated life cycles that necessarily involve more than one host.

5. Schistosoma mansoni cercaria can penetrate the skin of persons wading in infected waters and cause serious disease. (Figure 12.25)

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