Chapter 1: Scientific Thinking WHO WOULD YOU RATHER BE AND WHAT WOULD YOU RATHER DO? COME LEARN BIOLOGY WITH US. Your best pathway to.
Download ReportTranscript Chapter 1: Scientific Thinking WHO WOULD YOU RATHER BE AND WHAT WOULD YOU RATHER DO? COME LEARN BIOLOGY WITH US. Your best pathway to.
Chapter 1: Scientific Thinking WHO WOULD YOU RATHER BE AND WHAT WOULD YOU RATHER DO? COME LEARN BIOLOGY WITH US. Your best pathway to understanding the world Thomas Chen, Santa Monica College Learning Goals • • • • • • • • • • • • • Differentiate between scientific and alternative ways of thinking Describe the attributes of scientific and biological literacy Apply the scientific method to everyday situations Understand the flexibility of the scientific method Design critical experiments to test hypotheses Understand the importance of well-designed and controlled experiments Describe ways to blind experiments Describe the biases that can occur in scientific studies and ways to reduce those biases Understand how statistics can add support to scientific claims Identify pseudoscience and anecdotal evidence masked as scientific evidence Understand the limitations of science as a means to answer questions Understand how hierarchical organization and evolution tie together all the major themes in biology Define biology and properties of living things 1.1 What is science? Science is more than just a collection of facts, science is a process for understanding the world. What science is NOT? SCIENCE IS NOT a process that ... 1. can solve any problem or question 2. can ignore rules 3. attempts to prove things 4. produces certainties or absolute facts 5. in which understanding comes from faith or beliefs What is biology? Biology is the scientific study of living things. Don't believe everything you see on "Dr. Oz," researchers say. http://www.cbsnews.com/news/dont-believe-everything-you-seeon-dr-oz-researchers-say/ CBS NEWS December 22, 2014, 11:44 AM Researchers looked at a broad range of advice offered on "The Dr. Oz Show" and another popular medical program, "The Doctors." They found that fewer than half of Dr. Oz's recommendations -- just 46 percent -- were backed up by medical evidence. "The Doctors" had a slightly better track record, with 63 percent of their recommendations supported by evidence. The host of "The Dr. Oz Show," Dr. Mehmet Oz, has come under fire before for touting unproven "miracle" weight-loss supplements. He was grilled by a Senate committee in June and accused of misleading consumers about the supposed fat-burning benefits of green coffee bean extract. After he promoted the product on his show in 2012, viewers eagerly snapped up half a million bottles of the pills. Scientists Are curious Ask questions about how the world works Seek answers • Does the radiation released by cell phones cause brain tumors? • Are anti-bacterial hand soaps better than regular soap? • Do large doses of vitamin C reduce the likelihood of getting a cold? • Why is morning breath so stinky? And can you do anything to prevent it? • Why is it always windy on streets with tall buildings? • Does taking aspirin before drinking alcohol lead to faster intoxication? A CASE IN POINT: What do you call these three pieces of evidence presented by the FBI on SONY hacking? Conclusive? Convincing? Circumstantial? Inconclusive??? The FBI points to three key factors that "in part" lead to its conclusion. The statement mentions 1) the similarities between deletion malware used in the Sony hack to deletion malware previously by North Korean hackers; 2) it refers to tools used in the Sony attack that were similar to ones deployed in a North Korean attack on South Korean media and banks; and 3) the agency pointed out that infrastructure hardcoded into the malware (including IP addresses) matched infrastructure identified as North Korean in the past. Scientists deal with these issues everyday. Science Not simply a body of knowledge or a list of facts to be remembered… …but rather an intellectual activity, encompassing observation, description, experimentation, and explanation of natural phenomena. “How do you know that is true?” • The single question that underlies scientific thinking Dannon yogurt • Claimed in nationwide advertisements that its Activia yogurt relieves irregularity and helps with “slow intestinal transit time.” • Also claimed that its DanActive dairy drink helps prevent colds and flu. • The FTC charged that the ads were deceptive and had no substantiation or scientific evidence. …the importance of questioning the truth of many “scientific” claims you see on merchandise packages or read in the newspaper or on the Internet. Can we trust the packaging claims that companies make? • clinical drug trials and evidence • CEO says: people “are really not scientifically minded enough to be able to understand a clinical study.” You don’t have to be at the mercy of cranks, charlatans, advertising, or slick packaging. Learn exactly what it means to have scientific evidence. Learn what it means to think scientifically. The most important questions in biology: What are the chemical and physical bases for life and its maintenance? How do organisms use genetic information to build themselves and to reproduce? What are the diverse forms that life on earth takes and how has that diversity arisen? How do organisms interact with each other and with their environment? Scientific Literacy how to think scientifically how to use the knowledge we gain to make wise decisions increasingly important in our lives literacy in matters of biology is especially essential Cases in point: Which statement is most likely true? Can you answer them? 1. Indoor tanning salons are safer than tanning outside. 2. Most doctors prefer ibuprofen over acetaminophen for treating an injury. 3. Over-the-counter flu medications can shorten the duration of influenza. 4. A diet medication promises a large weight loss within 7 days. 5. Vaccinations can cause autism. Take-home message 1.1 Through its emphasis on objective observation, description, and experimentation, science is a pathway by which we can come to discover and better understand the world around us. 1.2 Biological literacy is essential in the modern world. A brief glance at any newspaper will reveal… Why are unsaturated fats healthier for you than saturated fats? What are allergies? Why do they strike children from clean homes more than children from dirty homes? Why do new agricultural pests appear faster than new pesticides? Biological Literacy The ability to: 1. use the process of scientific inquiry to think creatively about real-world issues, 2. communicate those thoughts to others, and 3. integrate them into your decision-making. BRCA1? Can genes be patented? Figure 1.9 Depression Biology is connected to many important issues in our lives • Medicine & health • Genetic engineering, stem cell therapy, cloning • Environmental problems and solutions Take-home message 1.2 Biological issues permeate all aspects of our lives. To make wise decisions, it is essential for individuals and societies to attain biological literacy. 1.3 The scientific method is a powerful approach to understanding the world. If science proves some belief of Buddhism wrong, then Buddhism will have to change —Dalai Lama, 2005 Why and when do people develop superstitions? Can animals be superstitious? Understanding How the World Works Someone wonders about why something is the way it is and then decides to try to find out the answer. This process of examination and discovery is called the scientific method. The Scientific Method Observe a phenomenon Propose an explanation for it Test the proposed explanation through a series of experiments ↓ Accurate and valid, or… Revised or alternative explanations proposed Scientific Thinking Is Empirical… …based on experience and observations that are rational, testable, and reproducible. Which statement below is based on empirical information? 1. A rabbit’s foot can prevent bad luck. 2. Chinese is harder to learn than Spanish. 3. We had a really cold winter; therefore, global warming must not be happening. 4. Soy beans contain all the essential amino acids. 5. An apple a day keeps the doctor away. Take-home message 1.3 There are numerous ways of gaining an understanding of the world. Because it is empirical, rational, testable, repeatable, and self-correcting, the scientific method is a particularly effective approach. 1.4 - 1.10 A beginner’s guide: what are the steps of the scientific method? 1.4 Thinking like a scientist: how to use the scientific method “Scientific Method” A rigid process to follow? A “recipe”? An adaptable process? One that includes many different methods? The basic steps in the scientific method are: Step 1: Make observations. Step 2: Formulate a hypothesis. Step 3: Devise a testable prediction. Step 4: Conduct a critical experiment. Step 5: Draw conclusions and make revisions. What should you do when something you believe in turns out to be wrong? This may be the most important feature of the scientific method: it tells us when we should change our minds. The scientific method can be used to examine a wide variety of issues. Does echinacea reduce the intensity or duration of the common cold? Does chemical runoff give rise to hermaphrodite fish? Does shaving hair from your face, legs, or anywhere else cause it to grow back coarser or darker? Put the steps of the scientific method in order. 1. 2. 3. 4. ABCDE ACBCE ADCBE ADBCE A. B. C. D. E. My car won’t start. If I jump my car’s battery, then my car will start. I jumped my battery, and the car still will not start. The car battery must have lost its charge. Maybe it is not the battery; I had better call a tow truck. Take-home message 1.4 The scientific method (observation, hypothesis, prediction, test, and conclusion) is a flexible, adaptable, and efficient pathway to understanding the world because it tells us when we must change our beliefs. 1.5 Step 1: Make observations. Look for interesting patterns or cause-and-effect relationships. Does taking echinacea reduce the intensity or duration of the common cold? Using the scientific method, we can answer these (and other) questions: Does chemical runoff give rise to hermaphrodite fish? Does hair that is shaved grow back coarser or darker? 1. 2. 3. 4. 5. Which answer below is NOT an observation? The sky appears blue on a clear sunny day. I feel more awake after my morning coffee. Exercising 5 days a week will improve my fitness. Oranges taste sweet, while lemons are sour. The campfire is hot. Take-home message 1.5 The scientific method begins by making observations about the world, noting apparent patterns or cause-and-effect relationships. 1.6 Step 2: Formulate a hypothesis. A proposed explanation for observed phenomena To be most useful, a hypothesis must accomplish two things: 1. It must clearly establish mutually exclusive alternative explanations for a phenomenon. 2. It must generate testable predictions. Figure 1-9 Hypothesis: the proposed explanation for a phenomenon Devising Testable Predictions We can only evaluate the validity of a hypothesis by putting it to the test. Researchers often pose a hypothesis as a negative statement, proposing that there is no relationship between two factors. The Null Hypothesis A negative statement that proposes that there is no relationship between two factors These hypotheses are equally valid but are easier to disprove. An alternative hypothesis It is impossible to prove a hypothesis is absolutely and permanently true. Which answer below is a hypothesis? 1. When sick, I took echinacea and felt better in a couple of days. 2. Echinacea reduces the duration and severity of the common cold. 3. Patients treated with echinacea should recover faster than untreated patients. 4. None of the above. Which statement below restates our hypothesis about echinacea as a null hypothesis? 1. 2. 3. 4. Echinacea reduces the duration and severity of the common cold. There is no link between sugar consumption and obesity. Hair that is shaved grows back coarser and darker. Taking vitamin C will reduce the duration and severity of an illness. 5. Eyewitness testimony is always accurate. Null and Alternative Hypotheses Echinacea reduces the duration and severity of the symptoms of the common cold. Or as a null hypothesis: • Echinacea has no effect on the duration or severity of the symptoms of the common cold. Estrogens in sewage runoff turn fish into hermaphrodites. Or as a null hypothesis: Estrogens in sewage runoff have no effect in turning fish into hermaphrodites. Hair that is shaved grows back coarser and darker. Or as a null hypothesis: There is no difference in the coarseness or color of hair that is shaved relative to hair that is not shaved. Take-home message 1.6 A hypothesis phenomenon. is a proposed explanation for a 1.7 Step 3: Devise a testable prediction from a Hypothesis. Suggest that under certain conditions we will make certain observations. Keep in mind any one of several possible explanations could be true. The goal is to: Propose a situation that will give a particular outcome if your hypothesis is true… …but that will give a different outcome if your hypothesis is not true. Let’s consider: Hypothesis: Eyewitness testimony is always accurate. Hypothesis: Eyewitness testimony is always accurate. Prediction: Individuals who have witnessed a crime will correctly identify the criminal regardless of whether multiple suspects are presented one at a time or all at the same time in a lineup. Which statement below is a prediction based on the following hypothesis: Echinacea reduces the duration and severity of the symptoms of the common cold. 1. If echinacea works, then the duration of cold symptoms will be the same between both treated and untreated patients. 2. If echinacea works, then patients suffering from colds should recover sooner when taking echinacea. 3. If echinacea works, then individuals suffering from the flu should recover sooner when taking echinacea. 4. If echinacea works, then taking twice the dosage of echinacea will be twice as effective. Hypothesis: Echinacea reduces the duration and severity of the symptoms of the common cold. Hypothesis: Hair that is shaved grows back coarser and darker. Prediction: If shaving leads to coarser, darker hair growing back, then if individuals shaved one leg only, the hair that grows on that leg should become darker and coarser than the hair growing on the other leg. Which answer below is a testable prediction? 1. 2. 3. 4. 5. Eyewitnesses will correctly identify a suspect individually or in a line up. Echinacea reduces the duration and severity of the common cold. Hair that is shaved grows back coarser and darker. Taking vitamin C will reduce the duration and severity of an illness. There is no link between sugar consumption and obesity. Take-home message 1.7 For a hypothesis to be useful, it must generate a testable prediction. 1.8 Step 4: Conduct a critical experiment. an experiment that makes it possible to decisively determine whether a particular hypothesis is correct Hypothesis: Echinacea reduces the duration and severity of the symptoms of the common cold. Hypothesis: Estrogens in sewage runoff turn fish into hermaphrodites. Critical experiment ideas? Does shaving or cutting hair make it grow back more thickly? Hypothesis: Hair that is shaved grows back coarser and darker. Critical experiment ideas? Take-home message 1.8 A critical experiment is one that makes it possible to decisively determine whether a particular hypothesis is correct. 1.9 Step 5: Draw conclusions, make revisions. Trial and error The Role of Experiments What is important is that we attempt to demonstrate that our initial hypothesis is not supported by the data. If it is not, we might then adjust our hypothesis. Making Revisions Try to further refine a hypothesis. Make new and more specific testable predictions. So a good hypothesis is falsifiable. Does echinacea help prevent the common cold? Hypothesis: Echinacea reduces the duration and severity of the symptoms of the common cold. Hypothesis: Hair that is shaved grows back coarser and darker. Of the three conclusions discussed, which is not convincing to you? 1. 2. 3. 4. 5. 1 and 2 2 and 3 1 and 3 All of the above. None of the above. 1. Echinacea does not decrease the duration and symptoms of the common cold. 2. Eyewitnesses do not always correctly identify a suspect. 3. Shaved hair does not grow back darker and coarser. Take-home message 1.9 Based on the results of experimental tests, we can revise a hypothesis and explain the observable world with increasing accuracy. A great strength of scientific thinking, therefore, is that it helps us understand when we should change our minds. 1.10 When do hypotheses become theories? Two distinct levels of understanding that scientists use in describing our knowledge about natural phenomena A hypothesis is a proposed explanation for a phenomenon. • a good hypothesis leads to testable predictions, but is falsifiable. A theory is a hypothesis for natural phenomena that is exceptionally wellsupported by the data and has broad explanatory power. • a hypothesis that has withstood the test of time and is unlikely to be altered by any new evidence. Theories vs. Hypotheses Repeatedly tested, Broader in scope Which statement below is likely not a scientific theory? 1. 2. 3. 4. Continents slowly drift. The sun is the center of our solar system. Bacteria can cause disease. Handwriting can definitively reveal one’s personality. Take-home message 1.10 Scientific theories do not represent speculation or guesses about the natural world. Theories are hypotheses that have been so strongly supported by empirical observation that the scientific community views them as very unlikely to be altered by new evidence. 1.11–1.13 Well-designed experiments are essential to testing hypotheses. 1.11 Controlling variables makes experiments more powerful. Elements Common to Most Experiments 1. Treatment • any experimental condition applied to individuals 2. Experimental group • a group of individuals who are exposed to a particular treatment 3. Control group • a group of individuals who are treated identically to the experimental group with the one exception: they are not exposed to the treatment 4. Variables • characteristics of your experimental system that are subject to change Controlling Variables the most important feature of a good experiment the attempt to minimize any differences between a control group and an experimental group other than the treatment itself Why does this experiment fall short of qualifying as a good example of the scientific method? Design a more carefully controlled study. -- 160 ulcer patients -- Experimental group? -- Control group? Is arthroscopic surgery for arthritis beneficial for the 300,000 people who have it each year? How do we know? The Placebo Effect The phenomenon in which people respond favorably to any treatment The placebo effect highlights the need for comparison of treatment effects with an appropriate control group. Clever Hans CLASSROOM CATALYST WHICH ANSWER BELOW WOULD STRENGTHEN YOUR EXPERIMENTAL DESIGN? 1. Use a large sample size with equal numbers of males and females and a broad range of ethnicities. 2. Use a small sample size and only look at the affects on men. 3. Use a large sample size and look at the affects on college-age people (18-25 years old). 4. Use a large sample size and look at the affects on African Americans. Experimental Designs Blind experimental design • The experimental subjects do not know which treatment (if any) they are receiving. Double-blind experimental design • Neither the experimental subjects nor the experimenter knows which treatment the subject is receiving. Hallmarks of an Extremely Well-designed Experiment Blind/double-blind strategies Randomized • The subjects are randomly assigned into experimental and control groups. Think back to the echinacea study. What type of experimental design was employed? 1. 2. 3. 4. Randomized trial Randomized, blind trial Randomized, double-blind trial Randomized, double-blind trial with test groups Take-home message 1.11 To draw clear conclusions from experiments, it is essential to hold constant all those variables we are not interested in. Control and experimental groups should vary only with respect to the treatment of interest. Differences in them can then be attributed to the treatment. 1·12 THIS IS HOW WE DO IT Is arthroscopic surgery for arthritis of the knee beneficial? How could you determine whether a particular type of surgery is effective? How does general scientific literacy—particularly among non-scientists such as the volunteers in this study—help in advancing our knowledge and understanding about a particular phenomenon? The Treatment Groups 1. Arthroscopic surgery with debridement 2. Arthroscopic surgery with lavage 3. Placebo surgery How did the researchers decide whether the arthroscopic surgery was effective? What is the take-home message from these two graphs? At two years, the pain scores were: Patient Group 1. Debridement Mean Pain Score 51 ± 23 2. Lavage 54 ± 24 3. Placebo 52 ± 24 What conclusions can you draw from these results? Give your opinion: “Given what I know about the scientific method, I would have volunteered for the arthroscopic knee surgery study.” 1. Strongly Agree 2. Agree 3. Neutral 4. Disagree 5. Strongly Disagree Take-home message 1.12 • In a well-controlled experiment, researchers demonstrated that arthroscopic knee surgery for osteoarthritis was no more beneficial for patients—in terms of knee pain and knee functioning—than a placebo surgery. 1.13 Repeatable experiments increase our confidence. Can science be misleading? How can we know? Do megadoses of vitamin C reduce cancer risk? An experiment must be reproducible and repeatable. Take-home message 1.13 Experiments and their outcomes must be repeatable for their conclusions to be valid and widely accepted. 1.14 We’ve got to watch out for biases. Can scientists be sexist? How would we know? Why isn’t the % of papers published with female first author 50%, even after the new review policy? 1. 2. 3. 4. Maybe there are fewer women than men who work as scientists. Maybe women are less likely to be the primary writer of a scientific article and thus be a first author. Maybe some of the authors are women but do not have gender specific names. Maybe women are not as likely to submit to the journal being studied. Take-home message 1.14 Biases can influence our behavior, including our collection and interpretation of data. With careful controls, it is possible to minimize such biases. 1.15-1.18 Scientific thinking can help us make wise decisions. Think about the following – a good and credible clinical trial must have the following components. Completely randomized, double-blinded, placebo controlled, multicentered involving a large population. What is the difference between a prospective and a retrospective clinical trial? A parallel design vs. a crossover design? 1.15 Visual displays of data can help us understand and explain phenomena. Variables Independent Variables • some measurable entity that is available at the start of a process and whose value can be changed as required. Dependent Variables • created by the process being observed and whose value cannot be controlled. 1. 2. 3. 4. Which represents the independent variable? Percentage of papers published with female first authors Sex of the author is known Sex of the author is not known Both 2 and 3. Take-home Message 1.15 Visual displays of data, which condense large amounts of information, can aid in the presentation and exploration of the data. The effectiveness of such displays is influenced by the precision and clarity of the presentation, and it can be reduced by ambiguity, biases, hidden assumptions, and other issues that reduce a viewer’s confidence in the underlying truth of the presented phenomenon. 1.16 Statistics can help us in making decisions Statistics A set of analytical and mathematical tools designed to help researchers gain understanding from the data they gather. Drawing conclusions based on limited observations is risky. Measuring a greater number of people will generally help us draw more accurate conclusions about human height. Making Wise Decisions About Concrete Things Does having access to a textbook help a student to perform better in a biology class? • Students who had access to a textbook scored an average of 81% ± 8% on their exams… • …while those who did not scored an average of 76% ± 7%. Statistics can also help us to identify relationships (or the lack of relationships) between variables. a positive correlation • meaning that when one variable increases, so does the other “Correlation is not causation.” Cause-consequence relationship: the mechanism, or how does it happen? Statistical analyses can help us to organize and summarize. What is the average range of scores for students who use textbooks while studying? 1. 2. 3. 4. 90 to 100% 95% 55-65% 65% Take-home message 1.16 Because much variation exists in the world, statistics can help us evaluate whether differences between a treatment and control group can be attributed to the treatment rather than random 1.17 Pseudoscience and misleading anecdotal evidence can obscure the truth. How to Prevent Being Taken in or Fooled by False Claims Identify two types of “scientific evidence” that frequently are cited in the popular media and are responsible for people erroneously believing that links between two things exist, when in fact they do not. 1. Pseudoscience: individuals make scientific-sounding claims that are not supported by trustworthy, methodical scientific studies. 2. Anecdotal observations: based on only one or a few observations, people conclude that there is or is not a link between two things. “Four out of five dentists surveyed recommend sugarless gum for their patients who chew gum.” “How do they know what they know?” Maybe the statement is factually true, but the general relationship it implies may not be. Anecdotal Observations do not include a sufficiently large and representative set of observations of the world data are more reliable than anecdotes Be critical. Which answer below is likely false? 1. Eating flax seeds and cold water fish are heart healthy. 2. Caffeine can reverse the effects of alcohol consumption. 3. The optimal weight for most adult humans is a BMI between 20-25. 4. Both 1 and 3. Although MMR vaccination does not cause autism, some people still think it does. Why? 1. Lack of scientific literacy 2. Swayed by anecdotal evidence 3. Fear due to lack of control for the cause 4. Combination of the above Take-home message 1.17 5. Other Pseudoscience and anecdotal observations often lead people to believe that links between two phenomena exist, when in fact there are no such links. 1.18 There are limits to what science can do. One of Several Approaches to the Acquisition of Knowledge The scientific method is, above all, empirical. Value judgments and subjective information Moral statements and ethical problems Take-home message 1.18 Although the scientific method may be the most effective path toward understanding the observable world, it cannot give us insights into the generation of value judgments and other types of non-quantifiable, subjective information. On the road to biological literacy: what are the major themes in biology? 1.19 Important unifying themes tie together the diverse topics in biology. Two Unifying Themes Hierarchical organization The power of evolution Four Chief Areas of Focus 1. 2. 3. 4. The chemical, cellular, and energetic foundations of life The genetics, evolution, and behavior of individuals The staggering diversity of life and the unity underlying it Ecology, the environment, and the subtle and important links between organisms and the world they inhabit Biologists investigate the full spectrum of life, from the biosphere to the biochemical reactions within a cell. Ecosystem Characteristics shared by all living organisms and living systems • A complex, ordered organization consisting of one or more cells. • Acquire & utilize energy to perform work. • Respond to the internal & external environment. • Regulation and homeostasis. • Growth, development, and reproduction. • Evolutionary adaptation leading to descent with modification over time. Take-home message 1.19 “Life” is not easily described with a simple definition. • The characteristics shared by all living organisms include: – complex and ordered organization; – the use and transformation of energy; – responsiveness to the external environment. • The characteristics shared by all living organisms include: – regulation and homeostasis; – growth, development, and reproduction; – and evolutionary adaptation leading to descent with modification. Classroom Catalyst Tuskegee Syphilis Study: Bioethics and Informed Consent What was the hypothesis for the Tuskegee Syphilis Study? 1. Black men suffering from syphilis will respond positively to treatment. 2. Men and women suffering from syphilis will respond positively to treatment. 3. Untreated men suffering from syphilis will respond positively to treatment. 4. Healthy black men will respond positively to treatment. What was the hypothesis for the Tuskegee Syphilis Study? 1. Black men suffering from syphilis will respond positively to treatment. 2. Men and women suffering from syphilis will respond positively to treatment. 3. Untreated men suffering from syphilis will respond positively to treatment. 4. Healthy black men will respond positively to treatment.