answers1-6 - Answers to Review Questions (p. 37) 1. Explain...

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Answers to Review Questions (p. 37) 1. Explain the apparent contradictions in defining microbiology as the study of microscopic organisms or the study of single-celled organisms. ANS: Most single-celled organisms require a microscope to be viewed, but not all. Some species are actually large enough to see with the naked eye. Many microbes form multicellular communities that render them visible. Two examples of these are mushrooms and biofilms. There are also some multicellular organisms that are microscopic, but do not fall into the category of a microorganism. 2. What is the genome of an organism? How do genomes of viruses differ from those of cellular microbes? ANS: The genome of an organism is the total genetic information contained in the organism’s chromosomal DNA. For most cellular organisms it contains all the information necessary for the organism’s self-replication. The genome of a virus is not always DNA. Furthermore, the viral genome does not contain all the information needed for self-replication. It relies on the cell machinery and its genome typically contains information to take over host cell processes to generate more virus particles. 3. Under what conditions might microbial life have originated? What evidence supports current views of microbial origin? ANS: The early Earth environment was composed mainly of highly reduced compounds. Living cells may have formed from spontaneous reactions sparked by UV absorption or electrical discharge. Miller found that when reduced compounds were subjected to an electrical discharge, several amino acids were observed. Oró did a similar experiment and found the production of adenine. There is still debate as to where the first cells came from. Some scientists believe life has an extraterrestrial origin. 4. List the ways in which microbes have affected human life throughout history. ANS: Probably the first thing that will come to mind is a microbe’s disease-causing properties. Microbes have been used in food production, mining, for their insecticidal activity, and for antibiotic production, to name just a few uses. We also rely on organisms to cycle compounds such as carbon and nitrogen. 5. Summarize the key experiments and insights that shaped the controversy over spontaneous generation. What key questions were raised, and how were they answered? ANS: Spontaneous generation means that life arises spontaneously, without parental organisms. In the 1600s, Redi showed that maggots appearing on decaying meat were actually the offspring of flies. When flies could not gain access to the meat, no maggots were observed. In the 1700s, Spallanzani sterilized liquid broth and showed that no organisms could grow unless the medium was inoculated. Proponents of spontaneous generation argued that there was no growth due to lack of oxygen. In the 1800s, Pasteur created swan-necked flasks to illustrate that it was not the lack of oxygen
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This note was uploaded on 10/05/2010 for the course BIOLOGY mcb1220 taught by Professor Mcdonals during the Spring '10 term at Aachen University of Applied Sciences.

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answers1-6 - Answers to Review Questions (p. 37) 1. Explain...

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