Difference between revisions of "Adventist Youth Honors Answer Book/Nature/Fungi"
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Revision as of 07:52, 17 June 2007
- 1 1. Give the name of five classes of fungi and examples of each.
- 2 2. Identify fifteen common fungi of your locality. Draw or photograph them from live specimens.
- 3 3. Name three important fungi and tell what their value is.
- 4 4. Tell the life history of one example of each of the following:
- 5 5. Identify five fungus plant diseases.
- 6 6. Know what safety precautions to observe when handling fungi.
- 7 References
1. Give the name of five classes of fungi and examples of each.
- The phylum Chytridiomycota, the chytrids, represents a group of primitive aquatic fungi. They are characterized by having gametes that are motile by means of flagella.
- The zygomycetes, in phylum Zygomycota, are characterized by the formation of sexual spores called zygospores. The zygospores are not contained within a specialized fruiting body or sac. Zygospores form when the haploid nuclei at the ends of two hyphae fuse together in a process of fertilization to form a diploid zygote. The zygote immediately undergoes meiosis to form haploid cells that develop into zygospores. The zygospores are unenclosed, or “naked,” between the parental hyphae. An example of a zygomycete is the common black bread mold, Rhizopus nigricans.
- Members of the Glomeromycota are also known as the arbuscular mycorrhizal fungi. Only one species has been observed forming zygospores; all other species only reproduce asexually.
- The ascomycetes are members of the phylum Ascomycota. They are also called the “sac fungi” because their sexual spores (ascospores) are enclosed in tube-like sacs known as asci. The formation of ascospores is similar to that of zygospores, except that the ascospores formed by meiosis are enclosed in the asci. Neurospora crassa is an ascomycete mold that was important in studies of genetic linkage.
- Basidiomycetes, also known as the “club fungi,” are classified in phylum Basidiomycota. Their sexual spores, or basidiospores, are formed on complex fruiting body structures called basidia. Basidiomycetes include some of the most complex fungi, including mushrooms and puffballs.
2. Identify fifteen common fungi of your locality. Draw or photograph them from live specimens.
3. Name three important fungi and tell what their value is.
Saccharomyces cerevisiae: This fungus is used in baker's yeast.
Aspergillus niger: This fungus is used to make citric acid commercially, and it also can be used to make gluconic acid. Both are important food additives.
Penicillium chrysogenum: This is the organism that makes penicillin, from which the majority of the large class of beta-lactam antibiotics are derived. Penicillin and its derivatives have saved countless lives since they were discovered and isolated, starting in the 1940s.
4. Tell the life history of one example of each of the following:
- The life histories of rusts often are mind-bogglingly complex, often with the fungus spending part of its life on one kind of plant, then another part on a completely different kind of plant. For example, near my trailer there's an Eastern Redcedar tree, Juniperus virginiana. All winter some brown, bumpy, woody, tumor-like items about the size of golfballs were visible growing on the branches. In early spring the bumps on the thing developed slender, sharp "horns" from which pollen-like dust emerged. You can see the item at the left, magnified about four times.
5. Identify five fungus plant diseases.
Fusarium oxysporum, also referred to as Agent Green, is a fungus that causes Fusarium wilt disease in more than a hundred species of plants. It does so by colonizing the water-conducting vessels (xylem) of the plant. As a result of this blockage and breakdown of xylem, symptoms appear in plants such as leaf wilting, yellowing and eventually plant death.
Interest in Fusarium oxysporum as a pesticide was first raised after the discovery in the 1960s that it was the causative agent in the destruction of the Hawaiian coca population.
The United States government was involved in a controversial program to use Fusarium oxysporum for the eradication of coca in Colombia and other Andean countries, but these plans were cancelled by president Bill Clinton who was concerned that the unilateral use of a biological agent would be perceived by the rest of the world as biological warfare. The Andean nations have since banned its use throughout the region. Use of biological agents to kill crops is potentially illegal under the Biological Weapons Convention.
Pinkroot, Phoma terrestris.
Downy mildew refers to any of several types of oomycete that infect plants. In commercial agriculture, they are a particular problem for growers of crucifers, grapes and vine-type vegetables.
Cucurbit downy mildew (caused by Pseudoperonospora cubensis) is specific to cantaloupe, cucumber, pumpkin, squash, watermelon and other members of the gourd family. The disease is one of the most important diseases of cucurbits worldwide.
Botrytis leaf blight
Botrytis leaf blight, Botrytis squamosa.
Neck rot, Botrytis allii.
Smut, Urocystis cepulae.
Smudge, Colletotrichum circinans.
White rot, Sclerotium cepivorum.