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Power and Desal Tec English Review
Quiz by Leah Nemis
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A facility that generates electricity by converting energy from sources like coal, gas, water, wind, or sunlight.
Gas Turbine
Generator
Power Plant
Blended Product Water
This means changing something from one form to another.
Converting
Fixing
Directing
A facility that generates electricity by converting energy from sources like coal, gas, water, wind, or sunlight.
This means changing something from one form to another.
Electricity is the energy that makes lights glow, fans spin, mobiles charge, and machines work.
Conductivity is a machine that spins when air, water, steam, or gas moves through it.
S_ _ _ _ formation is a hard crystalline substance that adheres to heat exchanger surfaces.
A device that converts mechanical energy into electrical energy.
A machine that burns fuel to produce hot gases, which spin internal blades to generate mechanical energy.
Means how easily electricity moves through a material.
Chemical Inhibitors are substances added to prevent or slow down scale formation.
Chemical added to prevent foaming tendency of flashing brine.
Holds the Taprogge balls.
Alkaline water with pH level 8 or _______.
Pump that extracts product water and sends it to reservoir.
Choose the correct spelling for the machine that spins when air, water, steam, or gas moves through it.
Choose the correct spelling for the air compression device.
Choose the correct spelling for the CO2-adding process.
Choose the correct spelling for the corrosion-control method.
Catches Taprogge balls after passing through tubes.
Sponge rubber balls used in the Taprogge system.
is thecomponent where compressed air and fuel are mixed and burned to create hot,high-pressure gases that drive the turbine.
Cathodic Protection is a method of corrosion control where the metal to be protected is made the cathode in an electrochemical cell by applying a direct current from anexternal anode.
Addition of chemicals like caustic soda and chlorine dioxide to adjustpH and kill bacteria before the water enters the reservoir.
Means the ability to do work or cause change.
Power and Desal Mastery QuizA. Arundhati Roy B. Jhumpa Lahiri C. Salman Rushdie D. Anita Desai ________________________________________ 2. The Lowland was published in: A. 2001 B. 2013 C. 2010 D. 2005 ________________________________________ 3. Which earlier work earned Lahiri the Pulitzer Prize? A. The Namesake B. Unaccustomed Earth C. Interpreter of Maladies D. The Lowland ________________________________________ 4. The novel is primarily about: A. Technology and modernity B. Immigration, family, and political violence C. Business rivalry D. Mythology and folklore ________________________________________ 5. The two central brothers in the novel are: A. Rahul and Anil B. Subhash and Udayan C. Gogol and Ashoke D. Amit and Nikhil ________________________________________ 6. Where did the brothers grow up? A. Mumbai B. Dhaka C. Calcutta D. Delhi ________________________________________ 7. Udayan becomes involved in: A. Peace activism B. Cinema C. Naxalite movement D. Business ________________________________________ 8. Subhash moves to: A. London B. Rhode Island C. Toronto D. Chicago ________________________________________ 9. Udayan is killed in: A. Jail B. A riot C. The lowland near his house D. A car accident ________________________________________ 10. Why does Subhash marry Gauri? A. Love B. To protect her and her unborn child C. Financial benefit D. Family pressure ________________________________________ 11. Gauri eventually: A. Becomes a politician B. Starts a business C. Leaves her family D. Returns to India ________________________________________ 12. Subhash raises Bela: A. With Gauri B. Alone C. With help from his parents D. In India ________________________________________ 13. Bela grows up believing: A. Udayan is her father B. Subhash is her father C. She has no father D. Her father died in war ________________________________________ 14. The setting of political unrest is linked to: A. Partition B. Naxalbari uprising C. Independence movement D. Civil War ________________________________________ 15. The narrative style uses: A. Magical realism B. Non-linear structure C. Poetry D. Second-person narration ________________________________________ 16. Gauri’s character represents: A. Traditional motherhood B. Obedient wife C. Intellectual autonomy and emotional detachment D. Political activism ________________________________________ 17. Bela’s character signifies: A. Rebellion against education B. Second-generation identity struggle C. Complete assimilation D. Materialistic living ________________________________________ 18. Memory in the novel functions as: A. A simple recollection B. A haunting presence affecting identity C. A forgotten history D. A symbolic decoration ________________________________________ 19. The lowland itself symbolizes: A. Wealth B. Stability C. Transitional, unstable space D. Escape ________________________________________ 20. Lahiri’s prose style can be described as: A. Flowery and ornate B. Minimalistic and restrained C. Dramatic and verbose D. Highly poetic ________________________________________ 21. Water imagery reflects: A. Joy and happiness B. Power and victory C. Memory and emotional fluidity D. Evil ________________________________________ 22. Which theory applies strongly to this novel? A. Structuralism B. Postcolonial hybridity C. Absurdism D. Modernism ________________________________________ 23. Postcolonial hybridity is linked to: A. Complete assimilation B. Identity in-between cultures C. Traditional values D. Language fluency alone ________________________________________ 24. Which character best reflects second-generation identity conflict? A. Gauri B. Bela C. Subhash D. Udayan ________________________________________ 25. What does Subhash struggle with most? A. Career failure B. Language C. Guilt and secrecy D. Wealth ________________________________________ 26. Udayan’s ideology centers on: A. Business growth B. Armed communist revolution C. Religious reform D. Education ________________________________________ 27. The novel shows how political violence leads to: A. Personal healing B. Economic prosperity C. Emotional trauma across generations D. Cultural unity ________________________________________ 28. Betrayal appears as: A. Only political B. Only emotional C. Both political and familial D. A background idea ________________________________________ 29. The genre of the text best fits: A. Fantasy B. Realistic political family saga C. Science fiction D. Thriller ________________________________________ 30. The narrative constantly shifts between: A. Dream and reality B. India and America C. Past and future India D. Fiction and nonfiction ________________________________________ 31. Homi Bhabha’s "third space" represents: A. Physical land B. A zone of cultural in-betweenness C. A literal building D. A heavenlike vision ________________________________________ 32. Gauri symbolizes: A. Traditional widowhood B. Female agency vs social expectation C. Blind loyalty D. Economic dependence ________________________________________ 33. Bela unknowingly inherits: A. Udayan’s ideology B. Gauri’s academic passion only C. Subhash’s calmness D. Grandparents’ wealth ________________________________________ 34. Lahiri uses silence to: A. Avoid details B. Deepen psychological complexity C. Reduce story relevance D. Simplify events ________________________________________ 35. A major structural device is: A. Letters B. Non-linear flashbacks C. Mythic storytelling D. Metafiction ________________________________________ 36. Which text offers a migrant theme comparison? A. The God of Small Things B. The White Tiger C. The Namesake D. Train to Pakistan ________________________________________ 38. The Naxalite movement first emerged in: A. Mumbai B. Naxalbari village C. Delhi D. Kerala ________________________________________ 39. Which theme repeats strongly? A. Celebration of success B. Silence and secrets C. Fantasy D. Heroism ________________________________________ 40. What does Bela do as an adult? A. Becomes a doctor B. Engages in environmental activism C. Joins corporate life D. Moves into politics ________________________________________ 41. The immigrant experience in the novel is portrayed as: A. Full belonging B. Alienation and partial belonging C. Achievement D. Liberation ________________________________________ 42. Which idea does Lahiri question through Gauri? A. Heroism B. Maternal expectation C. Religious devotion D. Wealth ________________________________________ 43. Subhash represents: A. Pure rebellion B. Survival and adaptation C. Anti-immigrant sentiment D. Total withdrawal ________________________________________ 44. Lahiri’s writing expects readers to: A. Passively accept the plot B. Read emotional subtext in silences C. Ignore symbols D. Only enjoy the story ________________________________________ 45. The lowland as a metaphor mainly signifies: A. Joy B. Unstable cultural ground C. Triumph D. Isolation from family ________________________________________ 46. Why is The Lowland considered significant? A. Its fantasy themes B. Its deep engagement with politics & identity C. Its humor D. Its romantic style ________________________________________ 47. Which comparative author also writes about diaspora identity? A. Chetan Bhagat B. Amitav Ghosh C. Premchand D. Ruskin Bond ________________________________________ 48. Udayan’s death drives the plot because: A. Family hides it B. It forces new relationships & trauma C. People forget him D. It has no consequence ________________________________________ 49. The narrative ends emphasizing: A. Closure and peace B. Lasting consequences of secrets C. National identity D. Religious conflict ________________________________________ 50. Scholars study this work because it explores: A. Only Indian history B. Trauma, diaspora, gender & politics C. Folk storytelling D. ComedyA Brief History of Washington’s Crossing of the Delaware River, Christmas Night 1776... In the fall of 1776, General George Washington and his army had suffered a series of defeats at the hands of the British Army. The Continental Army had lost every battle with the British in the New York campaign: Long Island, Manhattan, Brooklyn Heights, Harlem and White Plains and had surrendered Fort Washington and Fort Lee. At Fort Lee, the army barely escaped and was forced to leave behind its store of provisions, ammunition, and many of its weapons. A sense of defeat had settled around Washington as he was forced to retreat across New Jersey in November and finally to Pennsylvania on December 8, 1776. The British, at least, considered the war over. By December 11th, the only reason the British had not taken Philadelphia, the seat of the Continental Congress, was that Washington had ordered every boat in the Delaware River on the New Jersey side to be brought to the Pennsylvania side, thus denying the British army transportation. Washington knew that the British would be capable of resuming an offensive by crossing the Delaware once it iced over. As the harsh winter set in, the morale of the American troops was at an all-time low. The soldiers were forced to deal with a lack of both food and warm clothing, while Washington watched his army shrink because of desertions and expiring enlistments. Now, more than ever, a victory was desperately needed. Washington devised a courageous plan to take the offensive and cross the Delaware River on Christmas night and attack the Hessian garrison at Trenton, New Jersey, nine miles south of his encampment near McConkey's Ferry. The original plan called for three divisions to cross the Delaware under the cover of darkness. Lt. Col. John Cadwalader's division was to cross at Bristol and engage the southern most contingent of British forces — Hessian troops under the command of Colonel von Donop. General James Ewing's division was to cross at Trenton Ferry and take a position south of Assunpink Creek below Trenton and hold the bridge over that stream. Washington's division was to cross at McConkey's Ferry and then divide into two corps under General Nathanael Greene and General John Sullivan. Their point of attack was Trenton and the Hessian troops quartered there under the command of Colonel Johann Gottlieb Rall. The boats to be used for the crossing were gathered earlier in the month in compliance with General Washington's orders, primarily as a defensive measure. Various types of boats had been collected, most notably the large Durham boats used to carry pig iron down the Delaware to the Philadelphia markets. There were a number of problems in moving a large number of men, cannons, and supplies in an age when overland transportation was by foot and animal power. The roads were rutted and winding. There were no bridges over major rivers because the technology did not exist to span great distances. A river like the Delaware was crossed by ferry, sometimes out of service because of ice floes or floods, and certainly not designed to carry masses of men and equipment across quickly. A river could be a formidable natural barrier to an army on the move. Washington had several logistical concerns for the crossing. In addition to the troops were the cannon; each of which required at least two horses to pull it. The heavier twelve pounders, and probably the eight pounders, had four horses. There would have been between four and six ammunitions wagons. Officers of the rank of colonel or higher may have had horses. In sum, Washington had to move 2,400 men, eighteen cannons, at least four ammunition wagons and fifty to seventy-five horses across the Delaware River the night of December 25, 1776. Fully expecting to be supported by Cadwalader's and Ewing's divisions south of Trenton, Washington assembled his own troops near McKonkey's Ferry in preparation for the crossing. By 6:00 pm, 2,400 men had begun crossing the ice-chocked river. There was an abrupt change in the weather, forcing the men to fight their way through sleet and a blinding snowstorm. The river was flooded with sheets of ice moving at eleven or twelve miles per hour. These obstacles proved to be too much for the two supporting divisions led by Generals Cadwalader and Ewing, who did not cross at their assigned points along the river. It was Washington's pure force of will and determination that led to his troops' successful crossing of the river. Increasing Washington's odds were the sailors of Marblehead, Massachusetts. This group of hardened seamen, led by Col. John Glover, were used to the Nor'easters of New England. Sheer determination and muscles conditioned to the demands of rowing under the weather conditions now facing the Continental army enabled the Marbleheaders to row back and forth across the Delaware countless times. During the time of the Revolution, American soldiers marched single file along the margins of the roads. They were only assembled into a battle line (three deep) when they reached the battlefield. The battle plan had Washington's army marching in two divisions... General Greene's and General Sullivan's. They made a night march in two columns on separate roads, a very tricky operation that was prone to failure since the columns needed to arrive at the battlefield at the same time to carry out the surprise attack planned by Washington. The American army carried out the march flawlessly. Against all odds, Washington and his men successfully completed the crossing and marched to Trenton on the morning of December 26th and, in the resulting battle, achieved a resounding victory over the Hessians. By moving ahead with his bold and daring plan, General Washington reignited the cause of freedom and gave new life to the American Revolution.What term refers to the belief in the application of Charles Darwin's theory of natural selection to human society, particularly as it relates to competition and success? A) Muckraker B) Square Deal C) Social Darwinism D) Suffrage Which term describes journalists and writers who exposed and criticized social issues and corruption in the late 19th and early 20th centuries? A) Yellow Journalism B) Sherman AntiTrust Act C) Big Stick Policy D) Muckraker Theodore Roosevelt's domestic policy aimed at balancing the interests of business, consumers, and labor. What is it called? A) Open Door Policy B) Square Deal C) Social Darwinism D) Muckraker Which term represents the idea of equal voting rights, particularly for women, during the Progressive Era? A) Dollar Diplomacy B) Suffrage C) Corollary D) Roosevelt This legislation, passed in 1890, was designed to curb the power of large corporations and promote fair competition: A) Sherman AntiTrust Act B) Square Deal C) The Panama Canal D) Yellow Journalism What was the foreign policy approach that Theodore Roosevelt used to assert U.S. influence in the Western Hemisphere, emphasizing the use of military force if necessary? A) Big Stick Policy B) Open Door Policy C) Social Darwinism D) Muckraker Which policy aimed to ensure that all nations had equal trading access to China's markets in the late 19th and early 20th centuries? A) Dollar Diplomacy B) Big Stick Policy C) Open Door Policy D) Corollary This sensational and often exaggerated style of journalism, particularly associated with newspapers like the New York Journal and the New York World, helped fuel public sentiment leading to the Spanish-American War. What is it called? A) Roosevelt B) The Panama Canal C) Yellow Journalism D) Square Deal Which U.S. president played a significant role in the construction of the Panama Canal? A) Corollary B) Roosevelt C) Sherman AntiTrust Act D) Dollar DiplomacyA Choose the correct answer. 1 When his grandma died, he came ….. some of her money and property. A into C across B up D round 2 We should try to ….. the amount of rubbish in our area. A increase C provide B improve D reduce 3 I avoid driving to work because there are always ….. jams in the centre. A transport C power B traffic D station 4 By the end of the year, there will be more ….. farms in our city. A solar C floating B vertical D electric 5 Who is going to ….. our new piano? A deal C deliver B produce D construct 6 She doesn’t like being ….. in the house; she wants people around her. A healthy C lonely B crowded D alone 7 Why don’t you come ….. for dinner tonight? A up C over B into D back 8 Mr Jones has found the cure for a serious ….. . A disease C crime B pollution D poverty 9 Scientists are hopeful ….. the future of energy sources. A for C about B in D with 10 Do you think ….. tube trains will ever be used? A drone C charging B front D vacuum Grammar B Choose the correct answer. 1 I’ll still ….. two hours from now. A have gardened C garden B have gardening D be gardening 2 ….. you ….. your homework by 7 o’clock? A Will ... finish C Will … have finished B Will … be finishing D Won’t … finish 3 By 2100, experts ….. new energy sources. A will have discovered C will be discovering B will be discovered D will discover 4 The film will have started before we ….. there. A will have got C get B will get D will be getting 5 This time tomorrow, Sheila ….. a job interview. A will have C will be having B is having D will have had 6 David ..... back from work by dinner time. A will be coming C will have come B will come D won’t be coming 7 I can’t believe that in a few hours, we ….. our first live concert. A are performing C will have performed B will be performing D will perform 8 ….. next Friday, I will be flying to Glasgow. A This time C By B At D Until 9 Jake ….. by the end of September. A will retire C will have retired B is retiring D will be retiring 10 ….. the time Mum gets home, I will have tidied my room. A Before C Until B At D By Everyday English C Choose the correct answer. 1 A: How did you find that job? B: a I’ll be working in the local library. b I’ll be there from June 15th. c There was an advert online. 2 A: I can’t wait! B: a Sounds like fun. b I’ll work in my uncle’s restaurant. c I’ll stay there for two weeks. 3 A: Do you have any plans for the summer? B: a Really? b What about you? c Haven’t I told you? 4 A: What will your duties be? B: a I’ll be flying to London to see my uncle. b I’ll be helping customers. c I’ll have earned enough money to buy a new smartphone. 5 A: How long will you stay there? B: a Until the end of July. b Well, this time next week, I’ll be relaxing. c And what are your plans? Multiple choice quiz on this reading: By 1900, the United States had claimed its place as a world power through the Spanish-American War. As the new century began, the country governed subject territories in Puerto Rico, Hawaii, Guam, the Wake Islands, and the Philippines. U.S. troops also occupied Cuba. U.S. businesses reached beyond the country's borders. During the first decade of the new century, the Coca-Cola Company, Quaker Oats, AT&T, the Standard Oil Company, Du Pont, General Electric, and Ford Motor Company seized the opportunity for international sales. After finding international markets, they built factories abroad, taking advantage of lower labor costs in foreign countries. Then they asked for U.S. protection of their investments and interests. Foreign countries invested heavily in Central America. U.S. investors focused on banana plantations and mining, as well as railroads, with little money in government bonds. By 1913, U.S. investments in Central America totaled about $93 million. British investment in Central America peaked at about $115 million in 1913. About $75 million of that total represented railroad holdings, mostly in Costa Rica and Guatemala. The other $40 million was in government bonds, which were worth little or nothing. The Roosevelt Corollary to the Monroe Doctrine From its earliest days, the United States claimed a special interest in the Western Hemisphere. The Monroe Doctrine, issued in 1823, warned European powers to keep their hands off Latin America. In 1902, Britain, Germany, and Italy mounted a naval blockade of Venezuela. They wanted to force the government to repay its debts. All the countries involved eventually agreed to settle the matter by arbitration. The United States stood back and did nothing, but U.S. citizens were clearly uneasy with the appearance of European military forces in "their" hemisphere. In 1904, President Theodore Roosevelt issued a corollary to the Monroe Doctrine, saying that the United States would act as a police officer to keep order in the region. He intended both to keep European military forces out of the hemisphere and to protect U.S. and European investors, exerting whatever pressure or control on Latin American governments that might be necessary to these ends. In 1905, the Dominican Republic owed $40 million in debts to European lenders. In order to prevent the European nations from using military force to collect their debts, Roosevelt used U.S. power. The United States basically took over collection of Dominican customs taxes, declared that $20 million of the debt was unjustified, and began repayment of the rest. Building a Canal The United States needed a canal through Central America, in order to save shipping time and costs. Colombia had the best location for a canal, and the United States negotiated a deal. It would pay Colombia $10 million for a three-mile-wide strip of land and would make annual rental payments of $250,000 yearly, beginning in 1912. Colombia's Senate turned down the deal, and Roosevelt exploded in rage, calling its members "foolish and homicidal corruptionists." Roosevelt considered seizing the land for the canal by military force but soon found an easier way. The province of Panama seceded from Colombia. A U.S. gunship stood off shore, protecting the Panamanian rebels. They formed a new republic under the protection of the United States. The new country of Panama and the United States agreed on a canal treaty within days. The new treaty had similar terms except that the Canal Zone would be five miles wide, instead of three, and the United States would guarantee and maintain the independence of Panama. Revolutions While Roosevelt welcomed the revolution that separated Panama from Colombia, he opposed most other revolutionary activity. So did his successors in office, William Howard Taft and Woodrow Wilson. The U.S. presidents sent troops to put down revolutions in Nicaragua and Haiti, using U.S. military forces to set up new governments in those countries and maintaining military occupations for years. U.S. military interventions were frequent throughout the hemisphere. Dollar Diplomacy President Taft preferred using "dollar diplomacy" to control Latin American countries. In Honduras, for example, U.S.-based banana companies virtually ran the government. Taft supported expanded U.S. investment in South and Central American countries, the Caribbean, and the Far East. He ordered Secretary of State Philander Chase Knox to protect U.S. investments, sending in military troops if necessary. On the World Stage As a world power, the United States did not limit its involvement to the Western Hemisphere. In 1905, President Roosevelt brought Russia and Japan to the negotiating table to end their war over control of Korea and Manchuria. Roosevelt agreed to Japanese annexation of Korea in return for Japan giving up any claim to China, Hawaii, and the Philippines. Roosevelt won the Nobel Peace Prize for settling this dispute. In 1906, Roosevelt's negotiating powers were tested again. This time, he mediated a dispute between the Alliance powers—Germany, Austria-Hungary, and Italy—with the Entente—France, Russia, and Britain—over control of Morocco. The United States backed France and ended the dispute. No longer an upstart, the United States had taken its place as a world power alongside its former colonial ruler.Owls, such as the young snowy owls on the previous page, have for centuries been symbols of both wisdom and mystery. To many cultures their piercing eyes have conveyed a look of intelligence. Their silent flight through darkened landscapes in search of prey has projected an air of power or wonder. For this chapter and this book, owls are an engaging example of a living organism from the world of biology—the study of life. BIOLOGY AND YOU Living in a small town, in the country, or at the edge of the suburbs, one may be lucky enough to hear an owl's hooting. This experience can lead to questions about where the bird lives, what it hunts, and how it finds its prey on dark, moonless nights. Biology, or the study of life, offers an organized and scientific framework for posing and answering such questions about the natural world. Biologists study questions about how living things work, how they interact with the environment, and how they change over time. Biologists study many different kinds of living things ranging from tiny organisms, such as bacteria, to very large organisms, such as elephants. Each day, biologists investigate subjects that affect you and the way you live. For example, biologists determine which foods are healthy. As shown in Figure 1-1, everyone is affected by this impor- tant topic. Biologists also study how much a person should exer- cise and how one can avoid getting sick. Biologists also study what CHARACTERISTICS OF LIFE The world is filled with familiar objects, such as tables, rocks, plants, pets, and automobiles. Which of these objects are living or were once living? What are the criteria for assigning something to the living world or the nonliving world? Biologists have established that living things share seven characteristics of life. These characteristics are organization and the presence of one or more cells, response to a stimulus (plural, stimuli), homeostasis, metabolism, growth and development, reproduction, and change through time. Organization and Cells Organization is the high degree of order within an organism’s internal and external parts and in its interactions with the living world. For example, compare an owl to a rock. The rock has a spe- cific shape, but that shape is usually irregular. Furthermore, differ- ent rocks, even rocks of the same type, are likely to have different shapes and sizes. In contrast, the owl is an amazingly organized individual, as shown in Figure 1-2. Owls of the same species have the same body parts arranged in nearly the same way and interact with the environment in the same way. Copyright © by Holt, Rinehart and Winston. All rights reserved. ORGANISM (Barn Owl) ORGAN (Owl’s Ear) TISSUE (Nervous Tissue Within the Ear) CELL (Nerve Cell) your air, land, and fAll living organisms, whether made up of one cell or many cells, have some degree of organization. A cell is the smallest unit that can perform all life’s processes. Some organisms, such as bacteria, are made up of one cell and are called unicellular (YOON-uh-SEL-yoo-luhr) organisms. Other organisms, such as humans or trees, are made up of multiple cells and are called multicellular (MUHL-ti-SEL-yoo-luhr) organisms. Complex multicellular organisms have the level of orga- nization shown in Figure 1-2. In the highest level, the organism is made up of organ systems, or groups of specialized parts that carry out a certain function in the organism. For example, an owl’s ner- vous system is made up of a brain, sense organs, nerve cells, and other parts that sense and respond to the owl’s surroundings. Organ systems are made up of organs. Organs are structures that carry out specialized jobs within an organ system. An owl’s ear is an organ that allows the owl to hear. All organs are made up of tissues. Tissues are groups of cells that have similar abilities and that allow the organ to function. For example, nervous tissue in the ear allows the ear to detect sound. Tissues are made up of cells. A cell must be covered by a membrane, contain all genetic information necessary for replication, and be able to carry out all cell functions. Within each cell are organelles. Organelles are tiny structures that carry out functions necessary for the cell to stay alive. Organelles contain biological molecules, the chemical compounds that provide physical structure and that bring about movement, energy use, and other cellular functions. All biological molecules are made up of atoms. Atoms are the simplest particle of an ele- ment that retains all the properties of a certain element. Response to Stimuli Another characteristic of life is that an organism can respond to a stimulus—a physical or chemical change in the internal or external environment. For example, an owl dilates its pupils to keep the level of light entering the eye constant. Organisms must be able to respond and react to changes in their environment to stay alive. ORGANELLE (Mitochondrion) BIOLOGICAL MOLECULE (Phospholipid) ATOM (Oxygen) cell from the Latin, cella meaning “small room,” or “hut” Word Roots and Origins www.scilinks.org Topic: Characteristics of Life Keyword: HM60257 mb06se_bios01.qxd 5/18/07 10:37 AM Page 7 8 CHAPTER 1 Homeostasis All living things, from single cells to entire organisms, have mecha- nisms that allow them to maintain stable internal conditions. Without these mechanisms, organisms can die. For example, a cell’s water content is closely controlled by the taking in or releas- ing of water. A cell that takes in too much water will rupture and die. A cell that doesn’t get enough water will also shrivel and die. Homeostasis (HOH-mee-OH-STAY-sis) is the maintenance of a stable level of internal conditions even though environmental conditions are constantly changing. Organisms have regulatory systems that maintain internal conditions, such as temperature, water content, and uptake of nutrients by the cell. In fact, multi- cellular organisms usually have more than one way of maintain- ing important aspects of their internal environment. For example, an owl’s temperature is maintained at about 40°C (104°F). To keep a constant temperature, an owl’s cells burn fuel to produce body heat. In addition, an owl’s feathers can fluff up in cold weather. In this way, they trap an insulating layer of air next to the bird’s body to maintain its body temperature. Metabolism Living organisms use energy to power all the life processes, such as repair, movement, and growth. This energy use depends on metabolism (muh-TAB-uh-LIZ-uhm). Metabolism is the sum of all the chemical reactions that take in and transform energy and materials from the environment. For example, plants, algae, and some bacteria use the sun’s energy to generate sugar molecules during a process called photosynthesis. Some organisms depend on obtaining food energy from other organisms. For instance, an owl’s metabolism allows the owl to extract and modify the chemi- cals trapped in its nightly prey and use them as energy to fuel activities and growth. Growth and Development All living things grow and increase in size. Some nonliving things, such as crystals or icicles, grow by accumulating more of the same material of which they are made. In contrast, the growth of living things results from the division and enlargement of cells. Cell division is the formation of two new cells from an existing cell, as shown in Figure 1-3. In unicellular organisms, the primary change that occurs following cell division is cell enlargement. In multi- cellular life, however, organisms mature through cell division, cell enlargement, and development. Development is the process by which an organism becomes a mature adult. Development involves cell division and cell differen- tiation, or specialization. As a result of development, an adult organism is composed of many cells specialized for different func- tions, such as carrying oxygen in the blood or hearing. In fact, the human body is composed of trillions of specialized cells, all of which originated from a single cell, the fertilized egg. This unicellular organism, Escherichia coli, inhabits the human intestines. E. coli reproduces by means of cell division, during which the original cell splits into two identical offspring cells. FIGURE 1-3 Observing Homeostasis Materials 500 mL beakers (3), wax pen, tap water, thermometer, ice, hot water, goldfish, small dip net, watch or clock with a second hand Procedure 1. Use a wax pen to label three 500 mL beakers as follows: 27°C (80°F), 20°C (68°F), 10°C (50°F). Put 250 mL of tap water in each beaker. Use hot water or ice to adjust the tem- perature of the water in each beaker to match the temperature on the label. 2. Put the goldfish in the beaker of 27°C water. Record the number of times the gills move in 1 minute. 3. Move the goldfish to the beaker of 20°C water. Repeat observations. Move the goldfish to the beaker of 10°C. Repeat observations. Analysis What happens to the rate at which gills move when the temp- erature changes? Why? How do gills help fish maintain homeostasis? Quick Lab mb06se_bios01.qxd 5/18/07 10:37 AM Page 8 THE SCIENCE OF LIFE 9 Reproduction All organisms produce new organisms like themselves in a process called reproduction. Reproduction, unlike other characteristics, is not essential to the survival of an individual organism. However, because no organism lives forever, reproduction is essential for the continuation of a species. Glass frogs, as shown in Figure 1-4, lay many eggs in their lifetime. However, only a few of the frogs’ off- spring reach adulthood and successfully reproduce. During reproduction, organisms transmit hereditary informa- tion to their offspring. Hereditary information is encoded in a large molecule called deoxyribonucleic acid, or DNA. A short segment of DNA that contains the instructions for a single trait of an organism is called a gene. DNA is like a large library. It contains all the books—genes—that the cell will ever need for making all the struc- tures and chemicals necessary for life. Hereditary information is transferred to offspring during two kinds of reproduction. In sexual reproduction, hereditary information recombines from two organisms of the same species. The resulting offspring are similar but not identical to their parents. For example, a male frog’s sperm can fertilize a female’s egg and form a single fer- tilized egg cell. The fertilized egg then develops into a new frog. In asexual reproduction, hereditary information from different organisms is not combined; thus the original organism and the new organism are genetically the same. A bacterium, for example, reproduces asexually when it splits into two identical cells. Change Through Time Although individual organisms experience many changes during their lifetime, their basic genetic characteristics do not change. However, populations of living organisms evolve or change through time. The ability of populations of organisms to change over time is important for survival in a changing world. This factor is also impor- tant in explaining the diversity of life-forms we see on Earth today. 1. How does biology affect a person’s daily life? 2. How does biology affect society? 3. Name the characteristics shared by living things. 4. Summarize the hierarchy of organization found in complex multicellular organisms. 5. What are the different functions of homeostasis and metabolism in living organisms? 6. How does the growth among living and nonliv- ing things differ? 7. Why is reproduction an important characteristic of life? CRITICAL THINKING 8. Applying Information Crystals of salt grow and are highly organized. Why don’t biologists con- sider them to be alive? 9. Analyzing Models When a scientist designs a space probe to detect life on a distant planet, what kinds of things should it measure? 10. Making Comparisons Both cells and organisms share the characteristics of life. How are cells and organismsood supply will be like in the near future.EVOLUTION OF LIFE Individual organisms change during their lifetime, but their basic genetic characteristics do not change. However, populations of liv- ing organisms do change through time, or evolve. Evolution, or descent with modification, is the process in which the inherited characteristics within populations change over generations, such that genetically distinct populations and new species can develop. Evolution as a theme in biology helps us understand how the various branches of the “tree of life” came into existence and have changed over time. It also explains how organisms alive today are related to those that lived in the past. Finally, it helps us understand the mechanisms that underlie the way organisms look and behave. Natural Selection The ability of populations of organisms to change over time is important for survival in a changing world. According to the theory of evolution by natural selection, organisms that have certain favorable traits are better able to survive and reproduce success- fully than organisms that lack these traits. One product of natural selection is the adaptation of organisms to their environment. Adaptations are traits that improve an indi- vidual’s ability to survive and reproduce. For example, rabbits with white fur and short ears in a snowy place, such as the one in Figure 1-7a, may avoid predators and frostbitten ears more often than those with dark fur and long ears. Thus, the next generation of rabbits will have a greater percentage of animals carrying the genes for white fur and short ears. In contrast, the brown, long- eared rabbit, as shown in Figure 1-7b, would survive and reproduce more successfully in a hot desert environment. The survival and reproductive success of organisms with favor- able traits cause a change in populations of organisms over gener- ations. This descent with modification is an important factor in explaining the diversity of organisms we see on Earth today. 1. Name three unifying themes found in biology. 2. How is the unity and diversity in the living world represented? 3. Identify the three domains and the kingdoms found in each domain. 4. How are organisms interdependent? 5. Describe why evolution is important in explain- ing the diversity of life. 6. Distinguish between evolution and natural selection. CRITICAL THINKING 7. Applying Information Assign the various top- pings you put on pizza to the appropriate domains and kingdoms of life. 8. Analyzing Graphics According to the “tree” in Figure 1-5, which of these pairs are more closely related: Archaea:Bacteria or Archaea:Eukarya? 9. Making Hypotheses Fossil evidence shows that bats descended from shrewlike organisms that could not fly. Write a hypothesis for how natural selection might have led to flying bats. SECTION 2 REVIEW (a) This short-eared arctic hare, Lepus arcticus, is hidden from predators and protected from frostbite in a snowy environment. (b) The mottled brown coats of desert rabbits blend in with the dirt and dry grasses, and their long ears help them radiate excess heat and thus avoid overheating. FIGURE 1-7 (a) (b) Copyright © by Holt, Rinehart and Winston. All rights reserved. THE SCIENCE OF LIFE 13 TH E STUDY OF BIOLOGY Curiosity leads us to ask questions about life. Science provides a way of answering such questions about the natural world. Science is a systematic method that involves forming and testing hypotheses. More importantly, science relies on evidence, not beliefs, for drawing conclusions. SCIENCE AS A PROCESS Science is characterized by an organized approach, called the scientific method, to learn how the natural world works. The methods of science are based on two important principles. The first principle is that events in the natural world have natural causes. For example, the ancient Greeks believed that lightning and thunder occurred because a supernatural god Zeus hurled thunderbolts from the heavens. By contrast, a scientist considers lightning and thunder to result from electric charges in the atmos- phere. When trying to solve a puzzle from nature, all scientists, such as the one in Figure 1-8, accept that there is a natural cause to solve that puzzle. A second principle of science is uniformity. Uniformity is the idea that the fundamental laws of nature operate the same way at all places and at all times. For example, scientists assume that the law of gravity works the same way on Mars as it does on Earth. Steps of the Scientific Method Although there is no single method for doing science, scientific studies involve a series of common steps. 1. The process of science begins with an observation. An observation is the act of perceiving a natural occurrence that causes someone to pose a question. 2. One tries to answer the question by forming hypotheses (singular, hypothesis). A hypothesis is a proposed explanation for the way a particular aspect of the natural world functions. 3. A prediction is a statement that forecasts what would happen in a test situation if the hypothesis were true. A prediction is recorded for each hypothesis. 4. An experiment is used to test a hypothesis and its predictions. 5. Once the experiment has been concluded, the data are analyzed and used to draw conclusions. 6. After the data have been analyzed, the data and conclusions are communicated to scientific peers and to the public. This way oth- ers can verify, reject, or modify the researcher’s conclusions. SECTION 3 OBJECTIVES ● Outline the main steps in the scientific method. ● Summarize how observations are used to form hypotheses. ● List the elements of a controlled experiment. ● Describe how scientists use data to draw conclusions. ● Compare a scientific hypothesis and a scientific theory. ● State how communication in science helps prevent dishonesty and bias. VOCABULARY scientific method observation hypothesis prediction experiment control group experimental group independent variable dependent variable theory peer review All researchers, such as the one releasing an owl above, use the scientific method to answer the questions they have about nature. FIGURE 1-8 Copyright © by Holt, Rinehart and Winston. All rights reserved. 14 CHAPTER 1 OBSERVING AND ASKING QUESTIONS The scientific method generally begins with an unexplained observa- tion about nature. For example, people have noticed for thousands of years that owls can catch prey in near total darkness. As shown in steps and of Figure 1-9, an observation may then raise ques- tions. The owl observation raises the question: How does an owl detect prey in the dark? FORMING A HYPOTHESIS After stating a question, a biologist lists possible answers to a sci- entific question—hypotheses. Good hypotheses answer a question and are testable in the natural world. For example, as shown in step Figure 1-9, there are several possible hypotheses for the question of how owls hunt at night: (a) owls hunt by keen vision in the dark; (b) owls hunt by superb hearing; or (c) owls hunt by detecting the prey’s body heat. Predicting To test a hypothesis, scientists make a prediction that logically fol- lows from the hypothesis. A prediction is what is expected to hap- pen if each hypothesis were true. For example, if hypothesis (a) is true, (owls hunt by keen night vision) then one can predict that the owl will pounce only on the mouse in either a light or a dark room. If hypothesis (b) is true (owls hunt by hearing), then one can pre- dict that in a lighted room, the owl will pounce closer to the mouse’s head. But, in a dark room, the owl should pounce closer to a rustling leaf attached to the mouse. Finally, if hypothesis (c) is true (owls hunt by sensing body heat), then an owl would strike only the prey no matter the room conditions, because owls hunt by detecting the prey’s body heat. 3 1 2 Copyright © by Holt, Rinehart and Winston. All rights reserved. A scientific study includes observations, questions, hypotheses, predictions, experiments, data analysis, and conclu- sions. A biologist can use the scientific method to set up an experiment to learn how an owl captures prey at night. FIGURE 1-9 1 OBSERVATION Owls capture prey on dark nights. 2 QUESTION How do owls detect prey on dark nights? 3 HYPOTHESES a) Owls hunt in the dark by vision. b) Owls hunt in the dark by hearing. c) Owls hunt in the dark by sensing body heat. THE SCIENCE OF LIFE 15 Notice that these predictions make it difficult to distinguish be- tween the vision and body heat hypotheses. The reason is that both hypotheses predict that the owl could grab the mouse in a dark room. Also, these three hypotheses do not eliminate all other factors that could influence how the owl finds its prey. However, testing predictions can allow one to begin rejecting hypotheses and thus to get closer to determining the answer(s) to a question. DESIGNING AN EXPERIMENT Biologists often test hypotheses by setting up an experiment. Step in Figure 1-9 outlines an experiment to test the hypotheses about how an owl hunts at night. First, experimenters set up a room with an owl perch high on one side and a small trap door on the other side for releasing mice. Then, they tied a leaf to each mouse’s tail with a string and released each mouse into the room. Next, each mouse ran silently across the room, but the leaf trailed behind, making a rustling noise. During half of the trials, the lights were on. During the other half, the room was dark. Technicians videotaped all the action in the chamber with an infrared light, which owls cannot see. The researchers then viewed the videos and measured the position of the owl’s strike relative to each mouse’s head. Performing the Experiment Many scientists use a controlled experiment to test their hypotheses. A controlled experiment compares an experimental group and a control group and only has one variable. The control group pro- vides a normal standard against which the biologist can compare results of the experimental group. The experimental group is iden- tical to the control group except for one factor, the independent variable. The experimenter manipulates the independent variable, sometimes called the manipulated variable. 4 4 EXPERIMENT 5 DATA COLLECTION AND ANALYSIS Measure and compare the distance from the owl’s strike to the mouse and to the leaf in light and dark. 6 CONCLUSION Data supported the hearing hypothesis: Owls hunt in the dark by hearing. prey Test predictions of the three hypotheses. Control: In the light Experimental: In the dark 1 2 3 4 5 6 7 8 9 10 11 Predicting Results Materials 2 Petri dishes with agar, cellophane tape, wax pen Procedure 1. Open one of the Petri dishes, and streak your finger across the surface of the agar. 2. Replace the lid, and seal it with the tape. Label this Petri dish with your name and a number 1. 3. Seal the second Petri dish with- out removing the lid. Label this Petri dish with your name and the number 2. 4. Write a prediction about what will happen in each dish. Store your dishes as your teacher directs. Record your observations. Follow your teacher’s directions for disposal of your dishes. Analysis Was your prediction accurate? What evidence can you cite to support your prediction? If you did not obtain the results you predicted, would you change your testing method or your prediction? Explain. Evaluate the importance of obtaining a result that does not support your prediction. Quick Lab mb06se_bios03.qxd 5/18/07 10:40 AM Page 15 16 CHAPTER 1 The independent variable in the owl experiment is the presence or absence of light. In the owl experiment, the control group hunts in the light, and the experimental group hunts in the dark. In addi- tion to varying the independent variable, a scientist observes or measures another factor called the dependent variable, or respond- ing variable, because it is affected by the independent variable. In the owl experiment, the dependent variable is distance from the owl’s strike to the mouse’s head. Testing the Experiment Some controlled experiments are conducted “blind.” In other words, the biologist who scores the results is unaware of whether a given subject is part of the experimental or control group. This factor helps eliminate experimenter bias. Experiments should also be repeated, because living systems are variable. Moreover, scien- tists must collect enough data to find meaningful results. COLLECTING AND ANALYZING DATA Most experiments measure a variable—the dependent variable. This measurement provides quantitative data, data measured in numbers. For example, in the experiment above, scientists mea- sured the distance of an owl’s strike from the prey’s head in cen- timeters, as shown in step of Figure 1-9. An event’s duration in milliseconds is also an example of quantitative data. Biologists usually score the results of an experiment by using one of their senses. They might see or hear the results of an experiment. Scientists also extend their senses with a micro- scope for tiny objects or a microphone for soft sounds. In the owl experiment, biologists extended their vision with infrared cameras. Analyzing and Comparing Data After collecting data from a field study or an experiment and then organizing it, biologists then analyze the data. In analyzing data, the goal is to determine whether the data are reliable, and whether they support or fail to support the predictions of the hypothesis. To do so, scientists may use statistics to help determine relation- ships between the variables involved. They can then compare their data with other data that were obtained in other similar studies. It is also important at this time to determine possible sources of error in the experiment just per- formed. Scientists usually display their data in tables or graphs when analyzing it. For the owl study, biologists could have made a bar graph such as the one in Figure 1-10, which shows the average distance from the owl’s strike relative to the mouse’s head or the leaf in the light and in the dark. 5 5 0 10 15 20 25 In the light In the dark Average distance from strike (cm) Distance Between Owl Strike and a Mouse or From a Leaf Attached to Mouse 30 Mouse Leaf Mouse Leaf The data below are hypothetical results that might occur from the described owl experiment.The independent variable is the darkness of the room, and the dependent variable is how far the owl struck from the mouse’s head.The data show that the owl strikes more accurately at the mouse in the light but strikes more accurately at the leaf in the dark. FIGURE 1-10 Copyright © by Holt, Rinehart and Winston. All rights reserved. THE SCIENCE OF LIFE 17 DRAWING CONCLUSIONS Biologists analyze their tables, graphs, and charts to draw conclu- sions about whether or not a hypothesis is supported, as shown in step of Figure 1-9. The hypothetical owl data show that in the light, owls struck with greater accuracy at the mouse than at the leaf, but in the dark, owls struck with greater accuracy at the leaf than the mouse. Thus, the findings support the hearing hypothe- sis, but not the vision hypothesis. An experiment can only disprove, not prove, a hypothesis. For example, one cannot conclude from the results that the hearing hypothesis is proven to be true. Perhaps the owl uses an unknown smell to strike at the mouse. One can only reject the vision hypothe- sis because it did not predict the results of the experiment correctly. Acceptance of a hypothesis is always tentative in science. The scientific community revises its understanding of phenomena, based on new data. Having ruled out one hypothesis, a biologist will devise more tests to try to rule out any remaining hypotheses. Making Inferences Scientists often draw inferences from data gathered during a field study or experiment. An inference (IN-fuhr-uhns) is a conclusion made on the basis of facts and previous knowledge rather than on direct observations. Unlike a hypothesis, an inference is not directly testable. In the owl study, it is inferred that the owl detects prey from a distance rather than by direct touch. Applying Results and Building Models As shown in Figure 1-11, scientists often apply their findings to solve practical problems. They also build models to represent or describe things. For example in 1953, James Watson and Francis Crick used cardboard balls and wire bars to build physical models of atoms in an attempt to understand the structure of DNA. Mathematical models are sets of equations that describe how dif- ferent measurable items interact in a system. The experimenter can adjust variables to better model the real-world data. CONSTRUCTING A THEORY When a set of related hypotheses is confirmed to be true many times, and it can explain a great amount of data, scientists often reclassify it as a theory. Some examples include the quantum the- ory, the cell theory, or the theory of evolution. People commonly use the word “theory” in a different way than scientists use the word. People may say “It’s just a theory” suggesting that an idea is untested, but scientists view a theory as a highly tested, generally accepted principle that explains a vast number of observations and experimental data. 6 Copyright © by Holt, Rinehart and Winston. All rights reserved. Biologists often apply their knowledge of the natural world to practical problems. Studies on the owl’s keen ability to locate sounds in space despite background noise are helping biotechnologists and bioengineers develop better solutions for people with impaired hearing, such as the people shown in this picture. FIGURE 1-11 18 CHAPTER 1 COMMUNICATING IDEAS An essential aspect of scientific research is scientists working together. Scientists often work together in research teams or sim- ply share research results with other scientists. This is done by publishing findings in scientific journals or presenting them at sci- entific meetings, as shown in Figure 1-12. Sharing information allows others working independently to verify findings or to con- tinue work on established results. For example, Roger Payne pub- lished the results of his owl experiments in a journal in 1971. Then, other biologists could repeat it for verification or use it to study the mechanisms introduced by the paper. With the growing impor- tance of science in solving societal issues, it is becoming increas- ingly vital for scientists to be able to communicate with the public at large. Publishing a Paper Scientists submit research papers to scientific journals for publica- tion. A typical research paper has four sections. First, the Introduction poses the problem and hypotheses to be investigated. Next, the Materials and Methods describe how researchers proceeded with the experiment. Third, the Results state the findings the experiment presented, and finally, the Discussion gives the significance of the experiment and future directions the scientists will take. Job Description Forensic biolo- gists are scientists who study biological materials to investigate potential crimes and other legal issues against humans and animals. Forensic scientists have knowledge in areas of biology, such as DNA and blood pattern analysis, and work in private sector and public laboratories. Focus On a Forensic Biologist As a law enforcement forensic specialist for the Texas Parks and Wildlife Department, Beverly Villarreal assists the game warden in investigations of fish and wildlife violations, such as illegal hunting and fishing. Villarreal analyzes blood and tissue samples to identify species of animals such as fish, birds, and reptiles. Her work helps game wardens as they enforce state laws regarding hunting and fishing. Most people think of forensic scientists as the glamorous crime investigators on TV, but according to Villarreal real forensic scientists “spend a great deal of time at a lab bench running analysis after analysis.” Many of the methods used in animal forensics, such as DNA sequenc- ing, are also used in human forensics. Education and Skills • High school—three years of science courses and four years of math courses. • College—bachelor of science in biol- ogy, including course work in zoology and genetics, plus experience in per- forming DNA analyses. • Skills—patience, attention to detail, and ability to use fine tools. Careers in BIOLOGY Forensic Biologist For more about careers, visit go.hrw.com and type in the keyword HM6 Careers. www.scilinks.org Topic: Scientific Investigations Keyword: HM61358 mb06se_bios03.qxd 5/18/07 10:40 AM Page 18 THE SCIENCE OF LIFE 19 1. What two principles make the scientific method a unique process? 2. Define the roles of observations and hypotheses in science. 3. Summarize the parts of a controlled experiment. 4. Summarize how we make conclusions about the results of an experiment. 5. Why is the phrase, “it’s just a theory” misleading? 6. Give another example of a conflict of interest. CRITICAL THINKING 7. Making Hypotheses On a nocturnal owl’s skull, one ear points up, and the other ear points down. Suggest a hypothesis for this observation. 8. Designing Experiments Design an experiment to establish if owls hunt by keen sight or hunt by heat seeking. 9. Calculating Information What was the average distance between the owl’s strike and the mouse if the recorded differences in this experiment were 25, 22, 19, 19, and 15? SECTION 3 REVIEW After scientists submit their papers to a scientific journal, the editors of that journal will send the paper out for peer review. In a peer review, scientists who are experts in the field anonymously read and critique that research paper. They determine if a paper pro- vides enough information so that the experiment can be duplicated and if the author used good experimental controls and reached an accurate conclusion. They also check if the paper is written clearly enough for broad understanding. Careful analysis of each other’s research by fellow scientists is essential to making scientific progress and preventing scientific dishonesty. HONESTY AND BIAS The scientific community depends on both honesty and good sci- ence. While designing new studies, experimenters must be very careful to prevent previous ideas and biases from tainting both the experimental process and the conclusions. Scientists have to keep in mind that they are always trying to disprove their favorite ideas. Scientists repeat experiments to verify previous findings. This allows for science to have a method for self-correction and it also keeps researchers honest and credible to their peers in the field. Conflict of Interest For most scientists, maintaining a good reputation for collecting and presenting valid data is more important than temporary prestige or income. So, scientists try to avoid any potential conflicts of interest. For example, a scientist who owns a biotechnology company and manufactures a drug would not be the best researcher to critically test that drug’s safety and effectiveness. To avoid this potential con- flict of interest, the scientist allows an unaffected party, such as a research group, to test the drug’s effectiveness. The threat of a potential scandal based on misleading data or conclusions is a pow- erful force in science that helps keep scientists honest and fair. Scientists present their experiments in various forms. The scientists above are presenting their work in the form of a poster at a scientific meeting. FIGURE 1-12 Copyright © by Holt, Rinehart and Winston. All rights reserved. The Internet can provide a wealth of scientific information for a report, but the information may not always be credible or accurate. You can use the methods above to check the accuracy and credibility of your sources. SCIENCE TECHNOLOGY SOCIETY SCIENCE ON THE INTERNET: A New Information Age I n the past, students research- ing a science topic would typ- ically begin their research by visiting a library to use printed reference materials, such as encyclopedias. Today, most stu- dents research topics by using a computer and searching for information on the Internet. The Internet can provide students with a wealth of infor- mation. But which Web sites have accurate information, and which Web sites do not? Checking Web Addresses Students should use the Web address, or URL, to establish the Web site’s credibility. Usually, the domain name can suggest who has published the Web site. Web sites can be pub- lished by governmental agen- cies (ends in “dot gov” or .gov), by educational institutions (ends in “dot edu” or .edu), by organizations (ends in “dot org” or .org), or by commercial businesses (ends in “dot com” or .com). Government Web sites are usually reliable. Examples of credible governmental Web sites are the National Institutes of Health (NIH) and the Food and Drug Administration (FDA). University and medical school sites are also reliable sources of information. Many organiza- tions that research and teach the public about specific diseases and conditions can also provide reliable information. Examples of such organizations are the American Cancer Society and the American Heart Association. Evaluating Web Sites The credibility of the author of the Web site should also be checked. Make sure the author is not trying to sell anything and is established in his or her field. For example, a health Web site’s author should be a med- ical professional. It is also important to check the date that the information was posted on the Web to ensure that the information is current. Also, the Web site should provide ref- erences from valid sources, such as scientific journals or govern- ment publications. Finally, the student should always double-check informa- tion between several reliable Web sites. If two or three reliable sites provide the same informa- tion, the student can feel confi- dent in using that information. Web Sites for Students The Internet Connect boxes in this textbook have all been reviewed by professionals at the National Science Teachers Association (NSTA). Students can trust that these sites are reliable sources for science- or health-related topics. REVIEW 1. Which types of Web addresses are the most reliable? 2. List four important features to evaluate when using a Web site for research. 3. Supporting Reasoned Opinions Why do you think a Web site that is advertising a product may not offer accurate information? REVIEW 20 www.scilinks.org Topic: Using the Internet Keyword: HM61589 mb06se_biosts.qxd 5/18/07 10:42 AM Page 20 TOOLS AND TECHNIQUES With proper equipment and good methods, biologists can see, manipulate, and understand the natural world in new ways. Microscopes are one of many useful tools used to unlock nature’s biological secrets. MICROSCOPES AS TOOLS Tools are objects used to improve the performance of a task. Microscopes are tools that extend human vision by making enlarged images of objects. Biologists use microscopes to study organisms, cells, cell parts, and molecules. Microscopes reveal details that otherwise might be difficult or impossible to see. Light Microscopes To see small organisms and cells, biologists typically use a light microscope, such as the one shown in Figure 1-13. A compound light microscope is a microscope that shines light through a spec- imen and has two lenses to magnify an image. To use this micro- scope, one first mounts the specimen to be viewed on a glass slide. The specimen must be thin enough for light to pass through it. For tiny pond organisms, such as the single-celled paramecium, light passing through the organism is not a problem. For thick objects, such as plant stems, biologists must cut thin slices for viewing. There are four major parts of a compound light microscope. For further description of the parts of a micro- scope, see the Appendix. 1. Eyepiece The eyepiece (ocular (AHK-yoo-luhr) lens) magnifies the image, usually 10 times. 2. Objective Lens Light passes through the specimen and then through the objective lens, which is located directly above the specimen. The objective lens enlarges the image of the specimen. Scientists sometimes use stains to make the image easier to see. 3. Stage The stage is a platform that supports a slide holding the specimen. The slide is placed over the opening in the stage of the microscope. 4. Light Source The light source is a light bulb that provides light for viewing the image. It can be either light reflected with a mirror or an incandescent light from a small lamp. SECTION 4 OBJECTIVES ● List the function of each of the major parts of a compound light microscope. ● Compare two kinds of electron microscopes. ● Describe the importance of having the SI system of measurement. ● State some examples of good laboratory practice. VOCABULARY compound light microscope eyepiece (ocular lens) objective lens stage light source magnification nosepiece resolution scanning electron microscope transmission electron microscope metric system base unit Compound light microscopes open the human eye to an interesting world including tiny pond organisms, healthy and diseased cells, and the functioning of cell parts. FIGURE 1-13 Objective lens Eyepiece (ocular lens) Stage Light THE SCIENCE OF LIFE 21 Copyright © by Holt, Rinehart and Winston. All rights reserved. 22 CHAPTER 1 Magnification and Resolution Microscopes vary in powers of magnification and resolution. Magnification is the increase of an object’s apparent size. Revolving the nosepiece, the structure that holds the set of objective lens, rotates these lenses into place above the specimen. In a typical com- pound light microscope, the most powerful objective lens produces an image up to 100 times (100) the specimen’s actual size. The degree of enlargement is called the power of magnification of the lens. The standard ocular lens magnifies a specimen 10 times (10). To compute the power of magnification of a microscope, the power of magnification of the strongest objective lens (in this case, 100) is multiplied by the power of magnification of the ocular lens (10). The result is a total power of magnification of 1000. Resolution (REZ-uh-LOO-shuhn) is the power to show details clearly in an image. The physical properties of light limit the ability of light microscopes to resolve images, as shown in Figure 1-14a. At pow- ers of magnification beyond about 2,000, the image of the speci- men becomes fuzzy. For this reason, scientists use other microscopes to view very small cellsWrite questions about the following story:Into the Woods Henry David Thoreau raised his pen to write, but the chatter of guests in the next room filled his ears. He stared at the page. “Concord, 1841” was all that he had written. How would he write a book with such noise in his family’s house? Thoreau headed outside, shutting the door with emphasis. He would have to find a place of his own. Thoreau walked out of town. Tall white pines soon replaced the painted houses. He listened to the rustling of the leaves. What if I could stay here, he thought. He could live off the land, close to nature, and begin his book. It would take work, but he could do it. FPG /The Image Bank/Getty Images Years passed, but Thoreau still did not have a place in the woods. One day, his friend Ralph Waldo Emerson had an idea. Emerson was a well-known writer who had bought some land near Walden Pond. Because he and Thoreau shared the same interest in nature, Emerson decided to let Thoreau use part of this land. In March of 1845, Thoreau began to build a cabin. By July, it was ready. He could live and write in the woods.Cabin Life Thoreau’s move to the woods indicated that he liked to be alone. But Thoreau did not feel that way. “I have a great deal of company in my house,” he wrote. Red squirrels woke him by running up and down the sheer sides of his cabin. A snowshoe hare lived in the debris under his cabin, thumping against the floorboards. A sparrow once perched on his shoulder. Thoreau recorded these experiences in his journal. How easily writing came to him with the beauty of nature around him! On Walden Pond Thoreau was a naturalist. He noticed the habits of animals. Each encounter showed him something new. One afternoon, Thoreau tried to get a close look at a loon, but the bird quickly dove into the pond. He knew loons could travel long distances under water, so he guessed where it would come up. But every time Thoreau paddled to one spot, the loon came up somewhere else and let out a call—a howling laugh. What a silly loon, Thoreau thought. But after a while, Thoreau felt as though the bird was laughing at him because he still could not catch up to it. Thoreau wrote in his journal: His white breast, the stillness of the air, and the smoothness of the water were all against him. At length he uttered one of those prolonged howls, as if calling on the god of the loons to aid him, and immediately there came a wind from the east and rippled the surface, and filled the whole air with misty rain, and I was impressed.The spectacular scene made Thoreau wonder at the loon. It no longer seemed a silly animal, but one with some mysterious power. As months went by, Thoreau also became aware of each animal’s ability to stay alive. “His power of observation seemed to indicate additional senses,” Emerson once remarked. In winter, as he warmed his cabin by fire, he watched in awe as the moles warmed their nest by their own body heat. He understood forest life as never before. Back to Concord Like the geese that move to new ponds at the season’s end, so too did Thoreau leave Walden. He had done what he had set out to do, and had learned much from the woods around him. He packed his few belongings and his stack of journals and returned to Concord. Now, he would turn his journal entries into a book. Generations to come would know life on Walden Pond!