Chapter 1: Scientific Thinking Your best pathway to understanding the world Lectures by Mark Manteuffel, St. Louis Community College Learning Goals • Describe what science is. • Describe the scientific method. • Describe key aspects of well-designed experiments. • Describe how the scientific method can be used to help make wise decisions. • Describe the major themes in biology. More than just a collection of facts, science is a process for understanding the world. 1.1 What is science? What is biology? 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? 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.” The most important questions in biology: What is the chemical and physical basis for life and its maintenance? How do organisms use genetic information to build themselves and to reproduce? The most important questions in biology: 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 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 decisionmaking. Take-home message 1.2 Biological our lives. To issues permeate all aspects of 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. 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 & valid, or… Revised or alternative explanations proposed Scientific Thinking Is Empirical… …based on experience and observations that are rational, testable, and repeatable. 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. A beginner’s guide: what are the steps of the scientific method? 1.4 Thinking like a scientist: how do you 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. Q 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 shaving hair from your face, legs, or anywhere else cause it to grow back coarser or darker? 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-andeffect 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 hair that is shaved grow back coarser or darker? 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. 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. 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. Null and Alternative Hypotheses 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 is a proposed explanation for a phenomenon. 1.7 Step 3: Devise a testable prediction. Suggest that, under certain conditions, we will make certain observations. Devising a Testable Prediction from a Hypothesis Keep in mind any one of several possible explanations could be true. Devising a Testable Prediction from a Hypothesis 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. 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. 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. 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. Does shaving or cutting hair make it grow back more thickly? Hypothesis: Hair that is shaved grows back coarser and darker. Critical ideas? experiment 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. 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. 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 Hypotheses and Theories A hypothesis is a proposed explanation for a phenomenon. • a good hypothesis leads to testable predictions. Hypotheses and Theories A theory is a hypothesis for natural phenomena that is exceptionally wellsupported by the data. • 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 Take-home message 1.10 Scientific theories do not represent speculation or guesses about the natural world. Take-home message 1.10 Theories are hypotheses that have been so strongly and persuasively supported by empirical observation that the scientific community views them as very unlikely to be altered by new evidence. 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. Elements Common to Most Experiments 2. Experimental group • a group of individuals who are exposed to a particular treatment Elements Common to Most Experiments 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 Elements Common to Most Experiments 4. Variables • characteristics of your experimental system that are subject to change 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? Experimental Control design group with whom to compare the treatment group? Design a more carefully controlled study. 160 ulcer patients Experimental Control group? group? 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 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. 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 nonscientists 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 Mean Pain Score 1. Debridement 51 ± 23 2. Lavage 54 ± 24 3. Placebo 52 ± 24 What conclusions can you draw from these results? 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? 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. Scientific thinking can help us make wise decisions. 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. 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. Take-home message 1.15 • 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 Statistical is not causation.” analyses can help us to organize and summarize. 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 chance. 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 Q Does the measles, mumps, and rubella vaccine cause autism? Science is a way to call the bluff of those who only pretend to knowledge. It is a bulwark against mysticism, against superstition, against religion misapplied to where it has no business being. If we’re true to its values, it can tell us when we’re being lied to. —Carl Sagan Take-home message 1.17 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 nonquantifiable, 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. What is Life? Try to define it Characteristics shared by all living organisms and living systems: • A complex, ordered organization consisting of one or more cells. • The use and transformation of energy to perform work. • Sensitivity and responsiveness to the external environment. Characteristics shared by all living organisms and living systems: • Regulation and homeostasis. • Growth, development, and reproduction. • Evolutionary adaptation leading to descent with modification over time. Two Unifying Themes Hierarchical The organization power of evolution 4 Chief Areas of Focus 1. The chemical, cellular, and energetic foundations of life 2. The genetics, evolution, and behavior of individuals 3. The staggering diversity of life and the unity underlying it 4. Ecology, the environment, and the subtle and important links between organisms and the world they inhabit Take-home message 1.19 • “Life” is not easily described with a simple definition. Take-home message 1.19 • The characteristics shared by all living organisms include: – complex and ordered organization; – the use and transformation of energy; – responsiveness to the external environment. Take-home message 1.19 • The characteristics shared by all living organisms include: – regulation and homeostasis; – growth, development, and reproduction; – and evolutionary adaptation leading to descent with modification.