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Name CHAPTER 10 Class Date Bacteria and Viruses SECTION 1 Bacteria and Archaea National Science Education Standards BEFORE YOU READ After you read this section, you should be able to answer these questions: LS 1b, 1c, 2a, 3a, 3b, 4b • What are bacteria and archaea? • What are the characteristics of bacteria? • How do archaea and bacteria differ? What Are Bacteria and Archaea? Organisms are grouped by traits they have in common. All living things can be grouped into one of three domains: Bacteria, Archaea, or Eukarya. All organisms in domain Eukarya are eukaryotes. Each cell of a eukaryote has a nucleus and membranebound organelles. All organisms in domains Bacteria and Archaea are prokaryotes. A prokaryote is an organism that is single-celled and has no nucleus. Although many prokaryotes live in groups, they are single organisms that can move, get food, and make copies of themselves. Most prokaryotes are very small and cannot be seen without a microscope. However, you can see some very large bacteria with your naked eye. Prokaryotes Eukaryotes • single-celled • single-celled or multicellular • no nucleus • nucleus • no membrane-bound organelles • membrane-bound organelles Domain Bacteria Domain Archaea STUDY TIP Underline Use colored pencils to underline the characteristics of bacteria in red, characteristics of archaea in blue, and characteristics shared by both in green. READING CHECK 1. Identify What are two characteristics of prokaryotes? Domain Eukarya What Characteristics Do Archaea and Bacteria Share? NO NUCLEUS Prokaryotes do not store their DNA in a nucleus as eukaryotes do. Their DNA is stored as a circular loop inside the cell. READING CHECK 2. Describe What does the DNA of a prokaryote look like? Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook 141 Bacteria and Viruses Name SECTION 1 Class Date Bacteria and Archaea continued REPRODUCTION READING CHECK Prokaryotes copy themselves, or reproduce, by a process called binary fission. Binary fission is reproduction in which a single-celled organism splits into two singlecelled organisms. Before a prokaryote can reproduce, it must make a copy of its loop of DNA. After the cell splits, the two new cells are identical to the original cell. 3. Identify How do prokaryotes reproduce? Binary Fission 1 The cell grows. 2 The cell makes a copy of its DNA. Both copies attach to the cell membrane. 3 The DNA and its copy separate as the cell grows larger. TAKE A LOOK 4 The cells separate. Each new cell has a copy of the DNA. 4. Describe After binary fission, how do the two cells compare to the original cell? What Are Some Characteristics of Bacteria? Most of the prokaryotes that scientists have found are bacteria. Domain Bacteria has more individual members than domains Archaea and Eukarya combined have. Bacteria can be found almost everywhere. Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook 142 Bacteria and Viruses Name SECTION 1 Class Date Bacteria and Archaea continued SHAPE Most bacteria are one of three shapes: bacilli, cocci, and spirilla. Bacilli are rod-shaped. Cocci are spherical. Spirilla are long and spiral-shaped. Different shapes help bacteria survive. Most bacteria have a stiff cell wall that gives them their shape. Some bacteria have hairlike parts called flagella (singular, flagellum). A flagellum works like a tail to push a bacterium through fluids. READING CHECK 5. List What are three common shapes of bacteria? The Most Common Shapes of Bacteria Bacilli are rod shaped. They have a large surface area, which helps them take in nutrients. However, a large surface area causes them to dry out quickly. Cocci are spherical. They do not dry out as quickly as rod-shaped bacteria. TAKE A LOOK 6. Compare What advantage do cocci have over bacilli? 7. Compare What advantage do bacilli have over cocci? Spirilla are long and spiral-shaped. They have flagella at both ends. These tail-like structures help the bacteria move through fluids. Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook 143 Bacteria and Viruses Name SECTION 1 Class Date Bacteria and Archaea continued ENDOSPORES STANDARDS CHECK LS 4b Populations of organisms can be categorized by the functions they serve in an ecosystem. Plants and some microorganisms are producers— they make their own food. All animals, including humans, are consumers, which obtain their food by eating other organisms. Decomposers, primarily bacteria and fungi, are consumers that use waste materials and dead organisms for food. Food webs identify the relationship among producers, consumers, and decomposers in an ecosystem. Most bacteria do well in warm, moist places. Some species of bacteria die in dry and cold surroundings. However, some bacteria form endospores to survive these kinds of conditions. An endospore is a thick, protective covering that forms around the DNA of a bacterium. The endospore protects the DNA from changes in the environment. When conditions are good, the endospores break open, and the bacteria begin to grow. CLASSIFICATION Scientists can classify bacteria by the way the bacteria get food. There are three ways for bacteria to get food: consume it, decompose it, or produce it. • Consumers eat other organisms. • Decomposers eat dead organisms or waste. • Producers make their own food. Some bacteria can make food using the energy from sunlight. Word Help: categorized to put into groups or classes 8. List Name three roles bacteria can play in an ecosystem. Decomposers, such as the ones helping to decay this leaf, return nutrients to the soil. This allows other living things to use those nutrients. CYANOBACTERIA Cyanobacteria are producers. These bacteria have a green pigment called chlorophyll. Chlorophyll traps the energy from the sun. The cell uses this energy to make food. Some scientists think that billions of years ago, bacteria similar to cyanobacteria began to live inside larger cells. According to this hypothesis, the bacteria made food for itself and the larger cells. In return, the larger cells protected the bacteria. This relationship may have led to the first plant cells on Earth. Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook 144 Bacteria and Viruses Name SECTION 1 Class Date Bacteria and Archaea continued How Do Archaea Differ from Bacteria? Like bacteria, archaea are prokaryotes. However, archaea are different from bacteria. For example, not all archaea have cell walls. When they do have them, the cell walls are made of different materials than the cell walls of bacteria. There are three types of archaea: heat lovers, salt lovers, and methane makers. Heat lovers live in hot ocean vents and hot springs. They usually live in water that is 60°C to 80°C. However, they have been found in living in water as hot as 250°C. Salt lovers live where there are high levels of salt, such as the Dead Sea. Methane makers give off methane gas. Methane makers often live in swamps. They can also live inside animal intestines. READING CHECK 9. Identify What is one difference between archaea and bacteria? TAKE A LOOK 10. Identify What type of archaea do you think would live in this swamp? HARSH ENVIRONMENTS Although bacteria can be found almost anywhere, archaea can live in places where even bacteria cannot survive. For example, many archaea live in places with little or no oxygen. Many can also survive very high temperatures and pressures. Scientists have found archaea in the hot springs at Yellowstone National Park and beneath 430 m of ice in Antarctica. Archaea have even been found 8 km below the surface of the Earth! Even though they can be found in harsh environments, many archaea also live in more moderate environments, such as the ocean. Critical Thinking 11. Infer What kind of prokaryote would most likely be found near vents at the bottom of the ocean with extremely high temperatures? Explain your answer. Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook 145 Bacteria and Viruses Name Class Section 1 Review Date NSES LS 1b, 1c, 2a, 3a, 3b, 4b SECTION VOCABULARY binary fission a form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size endospore a thick-walled protective spore that forms inside a bacterial cell and resists harsh conditions prokaryote an organism that consists of a single cell that does not have a nucleus 1. List What are the three domains that include all living things? 2. Compare Fill in the Venn Diagram to compare bacteria and archaea. 3. Describe How do some scientists think the first plants appeared on Earth? 4. List Name three kinds of archaea. 5. Infer Do you think it would be possible to find bacteria and archaea living in the same environment? Explain your answer. Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook 146 Bacteria and Viruses Life Science Answer Key continued 6. They break down materials in the environ- 3. Some scientists think that bacteria similar to ment and absorb them. 7. 23 8. ability to move 9. Answers may vary. Venus’ flytrap is in kingdom Plantae. cyanobacteria started living in larger cells. The bacteria made food for themselves and the larger cells. The larger cells gave the bacteria protection. This relationship may have led to the first plant cells. 4. heat lovers, salt lovers, methane makers 5. Yes; although some archaea can live in harsh environments where bacteria cannot survive, some archaea live in more moderate places, such as the ocean. Bacteria live in most places, other than the most extreme environments, so they are likely to be found in the same environments as some archaea. Review 1. Domain Eukarya is made up of only eukaryotes. Domains Bacteria and Archaea are made up of only prokaryotes. 2. As scientists discover more organisms that do not fit into existing groups, they add new groups. 3. Linnaeus probably did not know that many of these organisms existed. Because they are so small, and because many archaea live in extreme environments, Linnaeus would not have been able to study the characteristics of these organisms. 4. kingdom Protista SECTION 2 BACTERIA’S ROLE IN THE WORLD 1. by eating plants 2. 700 billion 3. It lets them make products that are hard to find in nature. 4. The insulin can be taken out of the bacteria and given to people with diabetes. 5. antibiotics Chapter 10 Bacteria and Viruses Review 1. Nitrogen fixation is a process in which cer- SECTION 1 BACTERIA AND ARCHAEA 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. They are single-celled and have no nucleus. a single loop inside the cell by binary fission They are the same. bacilli, cocci, spirilla Cocci don’t dry out as quickly. Bacilli have a large surface area to help them take in nutrients. as producers, consumers, or decomposers Not all archaea have cell walls. When they do, the walls are made of different materials than those in bacterial cell walls. methane makers Archaea—they can survive in harsher environments than most bacteria. 2. 3. 4. 5. Review 1. Bacteria, Archaea, Eukarya 2. Bacteria: Some can form endospores to 6. tain bacteria take in nitrogen from the air and change it to a form that plants can use. Nitrogen from the air passes into the soil. Bacteria in the soil and on plant roots change nitrogen to another form. Plants use this form. Animals eat the plants to get nitrogen. Possible answers: Bacteria in soil turn nitrogen into a form that plants can use. Some bacteria break down dead plant and animal matter. This makes nutrients available to other living things. In genetic engineering, scientists change the genes of bacteria or any living thing. Scientists can put genes from one organism into another. They get into a host organism and take nutrients from the host’s cells. nitrogen SECTION 3 VIRUSES survive harsh conditions; they are the most plentiful organisms on Earth. Archaea: Some can live in extreme environments; not all have cell walls. Center: prokaryotes, no nucleus, singlecelled, reproduction by binary fission 1. Viruses change quickly. 2. They cannot reproduce without a host; they cannot eat or grow. 3. DNA and RNA 4. spacecraft shape Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook Answer Key 10 Life Science