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Biology: Exploring Life

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1 Biology: Exploring Life
Lab 1 Biology: Exploring Life

2 Antibiotics Too Much of a Good Thing? Vocabulary
The following terms and techniques are presented in or relevant to this video: Antibiotic—A chemical substance that kills microorganisms and cures infections. Antibiotic resistance—A trait that allows a microorganism to be resistant to an antibiotic. Evolution—Genetic change in a population or species over generations. Gangrene—The localized death of cells from an infection or the loss of blood supply. Meningitis—An infectious disease of the meninges, the layer of connective tissue that enwraps and protects the brain and spinal cord. Pneumonia—An infectious disease of the lungs caused by bacteria and viruses. Tuberculosis—An infectious disease caused by the bacteria Mycobacterium tuberculosis. Textbook Reference Biology: Concepts & Connections Module 1.6 Evolution explains the unity and diversity of life (pages 8–9) Module 1.8 Connection: Biology is connected to our lives in many ways (page 12) Module 5.9 Some pesticides and antibiotics inhibit enzymes (page 78) Module 12.2 Bacterial plasmids can serve as carriers for gene transfer (page 233) Module 13.5 Scientists can observe natural selection in action (page 266) Module The evolution of antibiotic resistance in bacteria is a serious public health concern (page 278) Module Some bacteria cause disease (page 330) Essential Biology and Essential Biology with Physiology Observing Natural Selection (pages 12–13) Biology and Society: Drugs That Target Cells (page 53) Natural Selection in Action (pages 255–256) The Ecological Impact of Prokaryotes (pages 307–310) Media Resources Web/CD Thinking as a Scientist 12.2 How Can Antibiotic-Resistant Plasmids Transform E. coli? Web/CD Thinking as a Scientist 13.4 How Do Environmental Changes Affect a Population? Web/CD Thinking as a Scientist Connection: What Are the Patterns of Antibiotic Resistance? Web/CD 34A Connection: DDT and the Environment Web/CD 1F Case Studies of Antibiotic Resistance Web/CD 8H Origins of Genetic Variation Web/CD 18A DDT and the Environment Web/CD Chapter 13—Case Studies in the Process of Science: What Are the Patterns of Antibiotic Resistance? Web/CD Chapter 4—Biology and Society on the Web: Learn about the downside of antibiotic use Web/CD Chapter 13—Biology and Society on the Web: Learn about the evolution of bacteria that are resistant to antibiotics

3 Antibiotics Your doctor prescribes an antibiotic and specifically cautions you to take every pill. Why? After the students watch the video, it’s likely that their response to this question may change. The question is repeated to offer an opportunity for you to continue the discussion, possibly with different opinions by your students.

4 Antibiotics Checkpoint What is an antibiotic?
a. It is a toxin used by bacteria to kill molds. b. It is a drug that can kill infectious bacteria. c. It is a chemical produced by the body to defend itself against viruses. d. It’s an area with conditions that don’t support life. e. None of the above are correct. Checkpoint questions are intended to help your students review the basic terms, facts, and information presented in the video segment. Alternatively, you may find these questions helpful if you have a personal response system integrated into your classroom. Questions and Answers What is an antibiotic? b. It is a drug that can kill infectious bacteria.—Option a is not the best answer because antibiotics were derived from molds that killed bacteria. Option c is not the best answer because antibiotics are generally considered to be drugs not produced by the body. In addition, antibiotics don’t work against viruses. Option d is not the best answer an antibiotic is not a place. Option e is not the best answer because Option b is correct.

5 Antibiotics Checkpoint Human white blood cells ________.
a. carry oxygen and carbon dioxide to the lungs b. store antibiotics for release at sites of infection c. serve as one of the body’s natural lines of defense against microbial invaders d. gather and eliminate antibiotics from the site of an infection e. All of these are correct. Checkpoint questions are intended to help your students review the basic terms, facts, and information presented in the video segment. Alternatively, you may find these questions helpful if you have a personal response system integrated into your classroom. Questions and Answers Human white blood cells _________. c. serve as one of the body’s natural lines of defense against microbial invaders—Option a is not correct because white blood cells are not used for carbon dioxide or oxygen transport. Option b is not correct because white blood cells don’t store antibiotics. Option d is not correct because white blood cells are a natural defense against microbial invaders and not against the antibiotic drugs. Option e is not correct because option c is the correct answer. White blood cells serve as one of the body’s natural lines of defense.

6 Antibiotics Checkpoint
About half of the antibiotics produced today __________. a. end up in animal feed b. are used by field hospitals in war zones c. are shipped to third-world countries d. become useless due to developing resistance by bacterial populations e. are stored for later use Checkpoint questions are intended to help your students review the basic terms, facts, and information presented in the video segment. Alternatively, you may find these questions helpful if you have a personal response system integrated into your classroom. Questions and Answers About half of the antibiotics produced today _________. a. end up in animal feed—Option b is not the best answer. Although antibiotics are used in hospitals in war zones, this use does not account for half of the production. Option c is not the best answer because more antibiotic is used domestically than is shipped overseas. Option d is not correct. Although antibiotic resistance is a concern, it is not significant enough to obviate so much antibiotic. Option e is not the best answer. Stockpiling antibiotic is not an effective practice against antibiotic resistance.

7 Antibiotics Checkpoint
How do bacteria populations become drug resistant? a. Antibiotics remove drug-susceptible individuals but leave those that are drug-resistant. b. Natural selection drives bacterial populations to change. c. Some individuals are genetically resistant to antibiotics. d. All of these are correct. Checkpoint questions are intended to help your students review the basic terms, facts, and information presented in the video segment. Alternatively, you may find these questions helpful if you have a personal response system integrated into your classroom. Questions and Answers How do bacteria populations become drug resistant? d. All of these are correct.—Options a, b, and c all describe conditions that contribute to the development of antibiotic resistance by bacterial populations. Option d is the best answer.

8 Antibiotics Checkpoint
Which of these is not an effective strategy to prevent antibiotic resistance? a. Don’t stockpile antibiotics. b. Don’t demand antibiotics from your physician. c. Use antibiotics only as long as symptoms remain. d. Use antibiotics as prescribed. e. Don’t share antibiotics with others. Checkpoint questions are intended to help your students review the basic terms, facts, and information presented in the video segment. Alternatively, you may find these questions helpful if you have a personal response system integrated into your classroom. Questions and Answers Which of these is not an effective strategy to prevent antibiotic resistance? c. Use antibiotics only as long as symptoms remain.—Option c is the best answer. Doctors prescribe enough antibiotic to rid the body of a disease-causing bacteria. Discontinuing medication prematurely may kill the vulnerable bacteria but allow the more resistant bacteria to survive and continue the infection. Options a, b, d, and e are considered to be effective strategies against the development of antibiotic resistance.

9 Antibiotics Biology and Society The development of antibiotic resistance by bacteria illustrates how natural selection affects our lives. Can you name another way our society experiences the effects of natural selection? Biology and Society questions are intended to help your students explore the social implications of the issues presented in the video. It is hoped that the information below will help you facilitate a class discussion about these issues. Discussion Question The development of antibiotic resistance by bacteria illustrates how natural selection affects our lives. Can you name another way our society experiences the effects of natural selection? Follow-Up Questions Is it likely that insect or plant pests (weeds) might develop resistance to pesticides and herbicides? Some plants, like BT corn and BT cotton, are being engineered to include a pesticide gene. What do you predict to be the long-term success of such a strategy? What strategies should a farmer employ to prevent pests from becoming resistant? Antibiotic resistance in bacteria is not the only case in which humans are causing pressures that contribute to the natural selection of a population. Other examples include insect resistance to BT corn, BT cotton, and other natural and genetically altered crops (http://www.nature.com/nsu/021202/ html). A great deal of research is being conducted to develop strategies to prevent pest populations from developing pesticide resistance (http://www.biotech-info.net/ECB.pdf).

10 Antibiotics Biology and Society Discussion Question
The development of antibiotic resistance by bacteria illustrates how natural selection affects our lives. Can you name another way our society experiences the effects of natural selection? Follow-Up Questions Is it likely that insect or plant pests (weeds) might develop resistance to pesticides and herbicides? Some plants, like BT corn and BT cotton, are being engineered to include a pesticide gene. What do you predict to be the long-term success of such a strategy? What strategies should a farmer employ to prevent pests from becoming resistant? Antibiotic resistance in bacteria is not the only case in which humans are causing pressures that contribute to the natural selection of a population. Other examples include insect resistance to BT corn, BT cotton, and other natural and genetically altered crops (http://www.nature.com/nsu/021202/ html). A great deal of research is being conducted to develop strategies to prevent pest populations from developing pesticide resistance (http://www.biotech-info.net/ECB.pdf).

11 Antibiotics Biology and Society
Many antibiotics—like penicillin—are no longer effective, but it is costly to develop replacements. Do we have an obligation to societies that cannot afford to develop these new and expensive antibiotics? Biology and Society questions are intended to help your students explore the social implications of the issues presented in the video. It is hoped that the information below will help you facilitate a class discussion about these issues. Discussion Question About 50% of the antibiotics produced today are used in the livestock industry. What impact does this have on the treatment of human diseases? Follow-Up Question Is it reasonable to expect that a disease-causing bacteria in livestock might jump over to infect humans? There is a raging debate on the use, or some would say misuse, of antibiotics in the livestock industry. Frontline, a PBS program, offers a thorough overview of the debate on its website (http://www.pbs.org/wgbh/pages/frontline/shows/meat/safe/).

12 Antibiotics Biology and Society
About 50% of the antibiotics produced today are used in the livestock industry. What impact does this have on the treatment of human diseases? Biology and Society questions are intended to help your students explore the social implications of the issues presented in the video. It is hoped that the information below will help you facilitate a class discussion about these issues. Discussion Question About 50% of the antibiotics produced today are used in the livestock industry. What impact does this have on the treatment of human diseases? Follow-Up Question Is it reasonable to expect that a disease-causing bacteria in livestock might jump over to infect humans? There is a raging debate on the use, or some would say misuse, of antibiotics in the livestock industry. Frontline, a PBS program, offers a thorough overview of the debate on its website (http://www.pbs.org/wgbh/pages/frontline/shows/meat/safe/).

13 Antibiotics Internet Research
Antibacterial Soap Doesn’t Prevent Viral Infection (http://kidshealth.org/research/antibacterial_products.html) This article outlines our use and misunderstanding of antibacterial soaps. Are there concerns that bacteria will develop resistance to antibacterial soaps? Drug Companies Snub Antibiotics (http://www.nature.com/nsu/030915/ html) The article speculates that drug companies are spending less money and less effort to develop new antibiotics. What evidence does the author cite? What are the consequences to global health if this is the case? Is Your Meat Safe? (http://www.pbs.org/wgbh/pages/frontline/shows/meat/safe/) This site outlines the debate over the use of antibiotics in the livestock industry. Familiarize yourself with the issues, then share your thoughts (http://www.pbs.org/wgbh/pages/frontline/shows/meat/talk/). Was the coverage fair and unbiased? Internet Research links are intended to help your students delve more deeply into the topics presented in the video. Antibacterial Soap Doesn’t Prevent Viral Infection (http://kidshealth.org/research/antibacterial_products.html) This article outlines our use and misunderstanding of antibacterial soaps. Are there concerns that bacteria will develop resistances to antibacterial soaps? Technology and Society Activity The article makes the point that antibiotic soaps don’t kill viruses, the cause of a great many illnesses, and many people still come down with the flu. Ask your students to evaluate this example for conditions that would contribute to the natural selection of bacteria that are resistant to antibiotic soaps. Drug Companies Snub Antibiotics (http://www.nature.com/nsu/030915/ html) The article speculates that drug companies are spending less money and effort to develop new antibiotics. What evidence does the author cite? What are the consequences to global health if this is the case? The article introduces the economic issues surrounding the research and development of new drugs. Ask your students to debate the conflicting positions advocating corporate profit and global health. If companies aren’t able to generate capital to pay for the research and development of new drugs, then where does this money come from? Is Your Meat Safe? (http://www.pbs.org/wgbh/pages/frontline/shows/meat/safe/) This site outlines the debate over the use of antibiotics in the livestock industry. Familiarize yourself with the issues, then share your thoughts (http://www.pbs.org/wgbh/pages/frontline/shows/meat/talk/). Was the coverage fair and unbiased? Ask your students to conduct a census of the meat department in their local grocery store. What percentage of beef, pork, chicken, or fish is organic? While the U.S. Food and Drug Administration doesn’t have a comprehensive system to notify consumers, this BBC article outlines issues relevant to the British consumer. It might be a valuable activity to ask your students to consider whether consumers in the United States and Canada should have these same food-labeling notifications. Additional Resources Drug-Resistant Gonorrhea Gains Foothold in N.E. (http://www.intelihealth.com/IH/ihtIH/WSIHW000/333/29758/ html) This is a 2004 article outlining a drug-resistant strain of gonorrhea that has emerged in the United States. Risks of Stockpiling Antibiotics to Counter Bioterrorism (http://www.tufts.edu/med/apua/News/Articles/risksOfStockpiling.html) This is a short article written by Stuart B. Levy, M.D., of Tufts University and president of the Alliance for the Prudent Use of Antibiotics. The article outlines concerns about stockpiling antibiotics. BT Corn & European Corn Borer: Long-Term Success Through Resistance Management (http://www.extension.umn.edu/distribution/cropsystems/DC7055.html) This is an article from the University of Minnesota Extension Service. It gives an overview advocating the use of BT corn and then outlines management practices designed to help prevent BT resistance in European corn borers.

14 Antibiotics Summary We didn’t have antibiotics before the 1940s.
Alexander Fleming helped to develop the first antibiotic from a mold. Antibiotics work to kill infecting bacteria. Natural variations exist within bacterial populations that make some bacteria resistant to antibiotics. Abuse of antibiotics promotes the development of antibiotic-resistant bacteria. Textbook Reference Biology: Concepts & Connections Module 1.6 Evolution explains the unity and diversity of life (pages 8–9) Module 1.8 Connection: Biology is connected to our lives in many ways (page 12) Module 5.9 Some pesticides and antibiotics inhibit enzymes (page 78) Module 12.2 Bacterial plasmids can serve as carriers for gene transfer (page 233) Module 13.5 Scientists can observe natural selection in action (page 266) Module The evolution of antibiotic resistance in bacteria is a serious public health concern (page 278) Module Some bacteria cause disease (page 330) Essential Biology and Essential Biology with Physiology Observing Natural Selection (pages 12–13) Biology and Society: Drugs That Target Cells (page 53) Natural Selection in Action (pages 255–256) The Ecological Impact of Prokaryotes (pages 307–310) Media Resources Web/CD Thinking as a Scientist 12.2 How Can Antibiotic-Resistant Plasmids Transform E. coli? Web/CD Thinking as a Scientist 13.4 How Do Environmental Changes Affect a Population? Web/CD Thinking as a Scientist Connection: What Are the Patterns of Antibiotic Resistance? Web/CD 34A Connection: DDT and the Environment Web/CD 1F Case Studies of Antibiotic Resistance Web/CD 8H Origins of Genetic Variation Web/CD 18A DDT and the Environment Web/CD Chapter 13—Case Studies in the Process of Science: What Are the Patterns of Antibiotic Resistance? Web/CD Chapter 4—Biology and Society on the Web: Learn about the downside of antibiotic use Web/CD Chapter 13—Biology and Society on the Web: Learn about the evolution of bacteria that are resistant to antibiotics

15 Antibiotics Preventing the development of antibiotic-resistant bacteria is in the hands of every individual. What actions will you take? It is hoped that the closing question will help your students make the following connections as they consider the topics presented in the video: The misuse of antibiotics by each individual can have dramatic consequences. Governments, corporations, and individuals all have a contributing role to the abuse of antibiotics. The actions we take in the United States will be ineffective if the rest of the world continues to misuse antibiotics in the treatment of diseases.

16 Five Steps of the scientific method
Observation come from others or results of earlier tests Questions are asked about unclear aspects of the observations: How? Why? When? Hypotheses are tentative explanation of a phenomenon phrased in such a way as to be testable. Predictions are logical, testable outcomes of the hypotheses developed by the use of deductive reasoning. Predictions take the form of if (statement of hypotheses) is true, then (predictions). Tests of prediction are performed to determine if the predictions are supported (fail to falsify) or falsified.

17 Concept Check Not all science discoveries strictly follow the “scientific method”. Which of the following would best be described as discovery science? Sequencing the human genome. Describing a new bird species from the Philippines. A project to find preserved specimens of the probably extinct Rocky Mountain locust frozen in glaciers . All of the above.

18 Answer Not all science discoveries strictly follow the “scientific method”. Which of the following would best be described as discovery science? All of the above.

19 Percent of total attacks
A Case Study of Hypothesis-Based Science In experiments designed to test hypotheses The use of control groups and experimental groups helps to control variables Percent of total attacks on artificial snakes 100 80 60 40 20 83% 17% 16% 84% Artificial king snakes Artificial brown snakes Coral snakes absent present Figure 1.8B Figure 1.8C Figure 1.8D Figure 1.8E

20 Interpreting Data These two snakes look remarkably similar to each other. The coral snake (right) is very poisonous to vertebrates. Hypotheses: H1: The coral snake’s bright color pattern serves to warn off potential predators. H2: The the king snake suffers less predation because it mimics or looks like the coral snake. H3: The protection that king snakes receive by mimicking coral snake will depend on the presence of coral snakes.

21 Interpreting Data A team of scientists designed an investigation that used artificial snakes to test the previous hypotheses. Which of the previous hypotheses are supported by the results displayed at the right? H1: The coral snake’s bright color pattern serves to warn off potential predators. H2: The the king snake suffers less predation because it mimics or looks like the coral snake. H3: The protection that king snakes receive by mimicking coral snake will depend on the presence of coral snakes. Both A and B

22 Answer A team of scientists designed an investigation that used artificial snakes to test the previous hypotheses. Which of the previous hypotheses are supported by the results displayed at the right? Both A and B

23 Interpreting Data Biologists placed artificial snake mimics in two different localities to test the hypothesis that looking like a poisonous snake only works where the poisonous snake is found: Outside of the coral snake range—only king snakes present. Inside the coral snake range—both coral and king snakes are present.

24 Interpreting Data The data graphed at the right __________ the hypothesis that the effectiveness of mimic coloration depends upon the presence of the poisonous model is: supports does not support is irrelevant to

25 Answer The data graphed at the right __________ the hypothesis that the effectiveness of mimic coloration depends upon the presence of the poisonous model is: supports

26 Interpreting Data Based on this data which of the following is a logical hypothesis or prediction? King snakes outside of the range of coral snakes will more closely resemble coral snakes than populations of king snake living within the range of coral . King snakes outside of the range of coral snakes will not resemble coral snakes as closely as populations of king snakes that live within the range coral snakes. Neither prediction is valid.

27 Answer Based on this data which of the following is a logical hypothesis or prediction? King snakes outside of the range of coral snakes will not resemble coral snakes as closely as populations of king snakes that live within the range coral snakes.

28 Controls This case study provides an example of a controlled experiment, one that is designed to compare an experimental group (the artificial king snakes, in this case study) with a control group (the artificial brown snakes). Ideally, the experimental and control groups differ only in the one factor the experiment is designed to test–in our example, the effect of the snakes’ coloration on the behavior of predators.

29 Controls Without the control group, the researchers would not have been able to rule out the number of predators in the different test areas as the cause of the different number of attacks on the artificial king snakes. The clever experimental design left coloration as the only factor that could account for the low predation rate on the artificial king snakes placed within the range of coral snakes.

30 Hypothesis Theory needing investigation: a tentative explanation for a phenomenon, used as a basis for further investigation The hypothesis of the big bang is one way to explain the beginning of the universe.

31 Hypothesis - defined A conjecture advanced for heuristic purposes, cast in a form that is amenable to confirmation or refutation by conducting of definable experiments and the critical assembly of empiric data; not to be confused with assumption, postulation, or unfocused speculation. Heuristic: LOGIC procedure for getting solution: a helpful procedure for arriving at a solution but not necessarily a proof

32 Deduction Conclusion drawn: a conclusion drawn from available information. Drawing a conclusion: the process of drawing a conclusion from available information. LOGIC logical conclusion: a conclusion reached by applying the rules of logic to a premise. LOGIC reasoning: the forming of conclusions by applying the rules of logic to a premise

33 A Case Study from Ever yday Life
A Case Study from Ever yday Life Deductive reasoning is used in testing hypotheses as follows If a hypothesis is correct, and we test it, then we can expect a par ticular outcome

34 Two important qualities of the hypotheses-based science
A hypothesis must be testable. A hypothesis must be falsifiable. A hypothesis becomes credible when repeated attempts to disprove it fail.

35 Introduction to Lab 1 scientific inquiry is a particular way of answering questions questions that can be answered by sci­ence must meet specific guidelines and scientific investigations must be carried out using certain rules an investigator cannot show that his or her experiment was done according to the guidelines, then the results of that experiment will not be recognized as valid by other scientists

36 Introduction to Lab 1 The purpose of such guidelines can be understood by comparing them to sports records. For example, a new record set in a track and field event only counts if the meet was approved by the governing body that sets the guidelines. The site and equipment used are scrutinized to be sure that they are within the regulations and the athlete is tested for use of illicit substances. Only when these required conditions are met is the record certified as valid.

37 Introduction to Lab 1 In this laboratory you will learn about the basic elements of scientific inquiry and how to apply this process to solving problems.

38 Exercise 1.3: The Elements of an Experiment
Objectives: Define and give examples of dependent, independent, and standardized variables. Identify the variables in an experiment. Explain what control treatments are and why they are used. Explain what replication is and why it is important.

39 Exercise 1.3: The Elements of an Experiment
Variables are things that may be expected to change during the course of the experiment. The investigator deliberately changes the independent variable He measures the dependent variable to learn the effect of changing the independent variable. To eliminate the effect of anything else that might influence the dependent variable, the investigator tries to keep standardized variables constant.

40 Dependent Variables The dependent variable is what the investigator measures (or counts or records). It is what the investigator thinks will vary during the experiment. For example, she may want to study peanut growth. One possible dependent variable is the height of the peanut plants. Name some other aspects of peanut growth that can be measured. Number of peanuts, weight of the plants, leaf area, time to maturation. All of these aspects of peanut growth can be measured and can be used as dependent variables in an experiment. There are different dependent vari­ables possible for any experiment. The investigator can choose the one she thinks is most important, or she can choose to measure more than one dependent variable.

41 Independent Variables
The independent variable is what the investigator deliberately varies during the experiment. It is chosen because the investigator thinks it will affect the dependent variable. Name some factors that might affect the number of peanuts produced by peanut plants. Amount of fertilizer, type of fertilizer, temperature, amount of water, day length, genetic type of the peanuts.

42 Standardized Variables
A third type of variable is the standardized variable. Standardized variables are factors that are kept equal in all treatments, so that any changes in the dependent variable can be attributed to the changes the investigator made in the independent variable.

43 Standardized Variables
Since the investigator's purpose is to study the effect of one particular independent variable, she must try to eliminate the possibility that other variables are influencing the outcome. This is accomplished by keeping the other variables at constant levels, in other words, by standardizing these variables.

44 Standardized Variables
For example, if the scientist has chosen the amount of fertilizer as the independent variable, she wants to be sure that there are no differences in the type of fertilizer used. She would use the same formulation and same brand of fertilizer throughout the experiment. What other vari­ables would have to be standardized in this experiment? Amount of water, temperature, day length, genetic type of peanuts.

45 Predictions A hypothesis is a formal, testable statement The investigator devises an experiment or collects data that could prove the hypothesis false He should also think through the possible outcomes of the experiment and make predictions about the effect of the independent variable on the dependent variable in each situation. It is useful to think of a prediction as an if/then state­ment: If the hypothesis is supported, then the results will be ...

46 Levels of Treatment Once the investigator has decided what the independent variable for an experiment should be, he must also determine how to change or vary the independent variable. The values set for the independent variable are called the levels of treatment.

47 Control Treatments It is also necessary to include control treatments in an experiment. A control treatment is a treatment in which the independent variable is either eliminated or is set at a standard value. The results of the control treatment are compared to the results of the experimental treatments

48 Control Treatments An investigator studies the amount of alcohol produced by yeast when it is incubated with different types of sugars. Control treatment: A treatment with no sugar. 2. The effect of light intensity on photosynthesis is measured by collect­ ing oxygen produced by a plant. Control treatment: Put a plant in the dark. 3. The effect of NutraSweet sweetener on tumor development in labora­tory rats is investigated. Control treatment: One group of rats receives no NutraSweet sweetener.

49 Subjects are given squares of paper to taste that have been soaked in a bitter-tasting chemical. The investigator records whether each person can taste the chemical. Control treatment: Use some papers that do not contain the chemical. 5. A solution is made up to simulate stomach acid at pH 2. Maalox antacid is added to the solution in small amounts, and the pH is mea­sured after each addition. Control treatment: Add water instead of Maalox antacid.

50 Replication Replicating the experiment means that the scientist repeats the experiment numerous times using exactly the same conditions to see if the results are consistent. A concept related to replication is sample size. It is risky to draw conclusions based upon too few samples.

51 Methods investigator must find a method to measure the dependent variable; otherwise, there is no experiment. investigator must find a method to measure the dependent variable; otherwise, there is no experiment.

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