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CHAPTER REVIEW USING VOCABULARY 1. For each pair of terms, explain how the meanings of the terms differ. a. virus and viroid b. oncogene and proto-oncogene c. capsid and envelope d. provirus and vector 2. Use the following terms in the same sentence: virus, lytic cycle, lysogenic cycle, and bacteriophage. 3. Use each of the following terms in a separate sentence: prion, prophage, temperate virus, and bacteriophage. 4. Word Roots and Origins The word virus is derived from the Greek ios, which means “poison.” Using this information, explain why the term virus is a good name for these particles. UNDERSTANDING KEY CONCEPTS 5. Summarize how the structure of viruses was discovered by Wendell Stanley. 6. Discuss why viruses are not considered living organisms. 7. Describe three different shapes viruses can have. 8. Compare replication in DNA viruses to replication in RNA viruses. 9. Differentiate the lytic cycle of viral replication from the lysogenic cycle of viral replication in bacteriophages. 10. Summarize how viruses are thought to have originated. 19. CONCEPT MAPPING Use the following terms to create a concept map that describes the lytic cycle: viruses, virulent, phage, injects, DNA, replicates, assemble, protein, and lyse. CRITICAL THINKING 20. Evaluating Information The drug azidothymidine (AZT) works by blocking the enzyme reverse transcriptase. Explain how AZT can help patients infected with HIV. 21. Applying Information Shingles is a disease caused by the same herpesvirus that causes chickenpox. How do you account for the fact that shingles often appears years after the initial chickenpox attack? 22. Applying Current Research Based on your knowledge of HIV structure and replication, describe one way to interrupt the replication of HIV. 23. Applying Information How does the increase of resistance to antiviral drugs in HIV relate to the theory of evolution by natural selection? 24. Applying Information Tobacco mosaic virus does not infect humans, but humans can transmit TMV from infected plants to healthy plants. What role do humans play in this mode of transmission? 25. Making Real-Life Connections For viral diseases without known cures, such as AIDS, certain types of hepatitis, and Ebola, identify ways in which the incidence of such diseases can be reduced. 26. Interpreting Graphics Look at the graph below. Discuss how the sharp jump in the number of viruses outside the cell corresponds to the phases of the lytic cycle. Growth Curve of Viruses 12. Name three vectors of viral diseases that can spread viruses to humans. 13. Discuss the role of viruses and oncogenes in the onset of cancer. 14. Describe the structure of HIV. 15. Explain the activity of reverse transcriptase in the replication cycle of the human immunodeficiency virus (HIV). 16. Summarize how emerging diseases can occur. 17. Discuss three methods humans use to control the spread of viral diseases. Number of viruses outside the cell 11. Describe four diseases caused by viruses that occur in humans. Time 18. Describe how viruses, viroids, and prions differ from one another. 496 CHAPTER 24 Copyright © by Holt, Rinehart and Winston. All rights reserved. CHAPTER REVIEW USING KEY TERMS 14. List four diseases caused by bacteria and the organs that the diseases affect. 1. For each pair of terms, explain how the meanings of the terms differ. a. halophile and thermoacidophile b. phototroph and chemotroph c. transduction and conjugation 2. Explain the relationship between antibiotics and antibiotic resistance. 3. Word Roots and Origins The term autotroph comes from the Greek autos, meaning “self,” and trophikos, meaning “food.” Using this information, explain why the term autotroph is a good name for cyanobacteria. UNDERSTANDING CONCEPTS 4. Identify the method that scientists have used to investigate how eukaryotes, bacteria, and archaea are related. 5. List one distinguishing characteristic of each of the three main groups of archaea. 6. List three common methods that are used to identify bacteria. 7. State reasons that cyanobacteria are considered the most self-sufficient organisms in nature. 8. Identify a nitrogen-fixing bacterium commonly found in the root nodules of legumes. 9. Name one bacterium that produces an antibiotic that is used in medicine. 10. Label the parts of the bacterium below. A B 15. Summarize how antibiotic resistance can develop in a bacterial population. 16. Relate three things that you can do to prevent foodborne illness in your home. 17. Identify the metabolic process that bacteria use to make food products such as pickles, coffee, and sauerkraut. 18. CONCEPT MAPPING Create a concept map that identifes the three main cell shapes of bacteria and describes the nutritional modes of bacteria. Include the following terms in your concept map: prokaryotes, bacilli, cocci, spirilla, chemotrophic, heterotrophic, endotoxin, exotoxin, Gram-negative, and Gram-positive. CRITICAL THINKING 19. Applying Information Scientists have only recently discovered fossilized prokaryotes. Explain why these fossils may have taken so long to discover. 20. Predicting Results Clostridium perfringens, the soil-dwelling bacterium that causes gas gangrene, is an obligate anaerobe. Using this information, predict which would be more likely to become infected with C. perfringens: a deep puncture wound or a surface cut. Explain the reason for your inference. 21. Recognizing Relationships Penicillin works by interfering with the ability of bacteria to polymerize the peptidoglycan cell wall. Given this fact, explain why Gram-positive bacteria are more susceptible to the effects of penicillin than Gramnegative bacteria are. 22. Analyzing Graphics Examine the photograph below, which shows bacteria that have been treated with a Gram stain. Would you hypothesize that these bacteria produce endotoxins? Explain your answer. D C 11. Summarize how chemoautotrophs get carbon and energy from their environment. 12. Name the term used to describe bacteria that can live in the presence or absence of oxygen. 13. Describe one way that bacteria can exchange genetic information. 478 CHAPTER 23 Copyright © by Holt, Rinehart and Winston. All rights reserved. Standardized Test Preparation DIRECTIONS: Choose the letter of the answer choice that best answers the question. 1. What are viruses made of? A. enzymes and fats B. carbohydrates and ATP C. protein and nucleic acids D. mitochondria and lysosomes 2. How do viroids differ from viruses? F. Viroids are larger in size. G. Viroids do not have a capsid. H. Viroids do not have nucleic acids. J. Viroids can cause disease in plants. DIRECTIONS: Complete the following analogy. 7. skin : person :: capsid : A. virus B. insect C. fungus D. bacterium INTERPRETING GRAPHICS: The figure below represents the human immunodeficiency virus. Use the figure to answer the question that follows. 3. During which of the following processes does a phage kill its host? A. conjugation B. transcription C. the lytic cycle D. the lysogenic cycle 4. Which of the following is one reason why viruses are not considered living organisms? F. Viruses are able to grow. G. Viruses do not metabolize. H. Viruses can reproduce by splitting. J. Viruses are too small to be easily observed. INTERPRETING GRAPHICS: Study the figure below to answer the following questions. X Y 8. The structure labeled Y represents which of the following? F. capsid G. envelope H. RNA genome J. reverse transcriptase SHORT RESPONSE Reverse transcriptase is an enzyme that catalyzes the synthesis of DNA from RNA. Explain why retroviruses must have reverse transcriptase to replicate. EXTENDED RESPONSE 5. Which of the following does the diagram represent? A. a virus B. a prion C. a viroid D. a bacterium 6. To which of the following is label X pointing? F. envelope G. nucleic acid H. protein coat J. cell membrane Viruses share several characteristics of living organisms. However, viruses are not considered to be living. Part A Compare the characteristics viruses share with living organisms to the characteristics they do not share with living organisms. Part B Would you anticipate more or fewer emerging viral diseases to appear in the future? Explain. When using a diagram to answer questions, carefully study each part of the figure as well as any lines or labels used to indicate parts of the figure. VIRUSES Copyright © by Holt, Rinehart and Winston. All rights reserved. 497 Standardized Test Preparation DIRECTIONS: Choose the letter of the answer choice that best answers the question. 1. How do bacteria produce yogurt from milk? A. by conjugation B. by fermentation C. by nitrogen fixation D. by aerobic respiration 2. What are rod-shaped bacteria called? F. cocci G. bacilli H. spirilla J. halophiles 3. What are thermoacidophiles? A. bacteria B. archaea C. spirochetes D. cyanobacteria DIRECTIONS: Complete the following analogy. 7. obligate aerobe : oxygen :: obligate anaerobe : A. low pH B. absence of oxygen C. presence of methane D. high salt concentration INTERPRETING GRAPHICS: The image below shows different shapes in bacteria. Use the image to answer the questions that follow. Organism A 4. Genetic recombination in bacteria can occur during which process? F. conjugation G. binary fission H. heterocyst formation J. endospore production INTERPRETING GRAPHICS: The table below lists the response of a bacterium to several antibiotics. A score of 0 means not sensitive, and sensitivity increases as the score increases. Use the table to answer the questions that follow. Antibiotic Sensitivity Ampicillin 3 Bacitracin 0 Cephalosporin 0 Penicillin 0 Rifampin 0 Streptomycin 3 Tetracycline 2 5. Which of the following antibiotics killed the bacteria most effectively? A. penicillin B. bacitracin C. tetracycline D. streptomycin 6. Which of the following antibiotics had no effect on the bacterium? F. ampicillin G. tetracycline H. streptomycin J. cephalosporin Organism B Organism C 8. What shape is represented by organism C? F. coccus G. bacillus H. spirillum J. filamentous 9. You would expect the members of the bacterial genus Bacillus to be what type of shape? A. rod shaped B. spiral shaped C. square shaped D. sphere shaped SHORT RESPONSE The Gram stain is used to distinguish bacteria based on a certain physiological difference between the bacteria. Describe the color of Gram-positive and Gramnegative bacteria when they are treated with the Gram stain. EXTENDED RESPONSE Species of the symbiotic bacterial genus Rhizobium live within the root nodules of legumes, such as soybeans and peanuts. Some farmers take advantage of the nitrogen-fixing abilities of these species when they rotate their crops every few years and grow legumes instead of their normal food crops. Part A Define nitrogen fixation. Part B Explain the benefits of crop rotation on the soil. When asked to complete an analogy, focus on the completed pair of terms provided. Identify the relationship that exists between the two terms; then, find the answer choice that has the same relationship with the third term provided. BACTERIA Copyright © by Holt, Rinehart and Winston. 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