Biology: Science for Life, with Physiology Sixth Edition Chapter 1 Can Science Cure the Common Cold? PowerPoint Lecture prepared by Dr. Judi Roux Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. Introduction to the Scientific Method Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. Learning Outcomes (1 of 2) • Describe the characteristics of a scientific hypothesis. • Compare and contrast the terms scientific hypothesis and scientific theory. • Distinguish between inductive and deductive reasoning. • Explain why the truth of a hypothesis cannot be proven conclusively via deductive reasoning. • Describe the features of a controlled experiment, and explain how these experiments eliminate alternative hypotheses for the results. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. Learning Outcomes (2 of 2) • List strategies for minimizing bias when designing experiments. • Define correlation, and explain the benefits and limitations of using this technique to test hypotheses. • Describe the information that statistical tests provide. • Compare and contrast primary and secondary sources. • Summarize the techniques you can use to evaluate scientific information from secondary sources. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. What advice do you receive from friends and family to treat your cold? A. Take vitamin C. B. Use zinc lozenges. C. Drink echinacea tea. D. Meditate. E. Get more rest. F. Wear a warm hat. G. Eat chicken soup. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (1 of 21) • Science is… ‒ a body of knowledge E.g., biology, the study of living organisms ‒ the discovery of something new and unknown Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (2 of 21) • Science is NOT… ‒ recalling specific facts about the world. ‒ memorizing what is already known. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (3 of 21) • The scientific method ‒ ‒ ‒ ‒ Making observations Proposing ideas Testing the ideas Discarding or modifying ideas based on results Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (4 of 21) • Observations lead to questions. • Hypotheses are proposed explanations for those observations. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (5 of 21) • Your mom’s observation: People are more likely to get colds when it is cold outside. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (6 of 21) • Your mom’s observation: People are more likely to get colds when it is cold outside. • Your mom’s hypothesis: Becoming chilled makes you more susceptible to illness. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (7 of 21) • The Nature of hypotheses ‒ Scientific hypotheses Testable: possible to evaluate Falsifiable: potentially false Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. Unfalsifiable hypothesis: You can’t prove it wrong Example: are there microchips in the COVID-19 vaccine? Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (8 of 21) • Everyday use of “theory” ‒ Untested ideas based on little information • Scientific theory ‒ Powerful, broad explanation for related observations Based on well-supported hypotheses Supported by different, independent lines of research example: Theory of evolution Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (9 of 21) • Chronic stomach ulcers ‒ Common belief: Ulcers are caused by acids and spicy foods. ‒ Treatment: drugs to reduce acid; avoiding spicy food ‒ New observation: Helicobacter pylori bacteria were found in most samples of ulcer tissue. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (10 of 21) • Chronic stomach ulcers ‒ Accepted fact: H. pylori infections cause stomach ulcers. 1. No reasonable alternative hypotheses are supported. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (11 of 21) • Chronic stomach ulcers ‒ Accepted fact: H. pylori infections cause stomach ulcers. 1. No reasonable alternative hypotheses are supported. 2. The hypothesis has not been rejected by carefully designed experiments. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (12 of 21) • Chronic stomach ulcers ‒ Accepted fact: H. pylori infections cause stomach ulcers. 1. No reasonable alternative hypotheses are supported. 2. The hypothesis has not been rejected by carefully designed experiments. 3. The relationship between H. pylori and stomach ulcers follows the germ theory of disease. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (13 of 21) • Fact 1: Fruits and vegetables contain much vitamin C. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (14 of 21) • Fact 1: Fruits and vegetables contain much vitamin C. • Fact 2: People with diets rich in fruits and vegetables are generally healthier. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (15 of 21) • Fact 1: Fruits and vegetables contain much vitamin C. • Fact 2: People with diets rich in fruits and vegetables are generally healthier. • Fact 3: Vitamin C is an anti-inflammatory agent that reduces throat and nose irritation. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (16 of 21) • Fact 1: Fruits and vegetables contain much vitamin C. • Fact 2: People with diets rich in fruits and vegetables are generally healthier. • Fact 3: Vitamin C is an anti-inflammatory agent that reduces throat and nose irritation. • Hypothesis: Consuming vitamin C decreases the risk of catching a cold. ‒ Inductive reasoning: combining specific observations to a general principle Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (17 of 21) • Hypothesis: Consuming vitamin C decreases the risk of catching a cold. ‒ Sensible ‒ Needs to be tested ‒ May be proven false Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (18 of 21) • The logic of hypothesis tests Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (19 of 21) • The logic of hypothesis tests ‒ Hypothesis testing based on Deductive reasoning – General principle to predict observations If/then statements for making predictions Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. Deduction moves from idea to observation , while induction moves from observation to idea. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (20 of 21) • The logic of hypothesis tests Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.1 The Process of Science (21 of 21) • The logic of hypothesis tests ‒ Prediction is true Hypothesis is supported but NOT proven ‒ Prediction is false Hypothesis rejected and disproven Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.2 Hypothesis Testing (1 of 21) • Hypothesis: The common cold is caused by a virus. ‒ Tested by experiments ‒ Supported by experimental results. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. All hypotheses need to be tested with laboratory experiments. (1 of 2) A. True B. False Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. All hypotheses need to be tested with laboratory experiments. (2 of 2) A. True B. False Explanation: Some hypotheses may be tested by observations of fossils. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.2 Hypothesis Testing (2 of 21) • The experimental method ‒ Experiments Collect data or information Test specific hypotheses Example: Scientists will measure the effects of vitamin C on cold prevention Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.2 Hypothesis Testing (3 of 21) • The Experiment: To measure the effect of vitamin C on cold prevention • Variables: factors that may change ‒ Independent variables: those manipulated by the researcher Vitamin C intake Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.2 Hypothesis Testing (4 of 21) • The Experiment: To measure the effect of vitamin C on cold prevention • Variables: factors that may change ‒ Independent variables: those manipulated by the researcher Vitamin C intake ‒ Dependent variables: those not changed by the researcher; may change during the experiment Susceptibility to illness upon exposure to virus Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.2 Hypothesis Testing (5 of 21) • Controlled experiments ‒ Test the effect of a single variable ‒ Limit possible alternate hypotheses ‒ Differences in results should be due to treatment Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.2 Hypothesis Testing (6 of 21) • Control or control group ‒ Similar to experimental subjects ‒ Do NOT receive the experimental treatment Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.2 Hypothesis Testing (7 of 21) • Steps for controlled experiments 1. Random assignment to control or experimental group 2. Identical participation for both groups except for the testing treatment Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.2 Hypothesis Testing (8 of 21) • Echinacea tea experiment ‒ Hypothesis: Drinking echinacea tea relieves cold symptoms. Experimental group drank echinacea tea 5–6 times daily Control group drank “sham” tea (placebo) Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.2 Hypothesis Testing (9 of 21) • Echinacea tea experiment ‒ Hypothesis: Drinking echinacea tea relieves cold symptoms. Independent variable: drinking tea Dependent variable: relief from cold symptoms Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.2 Hypothesis Testing (10 of 21) • Echinacea tea experiment ‒ Hypothesis: Drinking echinacea tea relieves cold symptoms. Independent variable: drinking tea Dependent variable: relief from cold symptoms ‒ Results: Experimental group felt echinacea tea was 33% more effective. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.2 Hypothesis Testing (11 of 21) • Minimizing bias in experimental design Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.2 Hypothesis Testing (12 of 21) • Minimizing bias in experimental design ‒ Bias: influence on results ‒ Blind studies: limit participant knowledge ‒ Double-blind studies: also limit researcher knowledge of participant groups Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.2 Hypothesis Testing (13 of 21) • Using correlation to test hypotheses ‒ When controlled experiments on humans may be Impossible Dangerous Unethical Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.2 Hypothesis Testing (14 of 21) • Using correlation to test hypotheses ‒ Model systems: used to avoid unethical or impractical tests on humans Bacteria Fruit flies Nematodes Mammals (rodents, dogs, pigs, human cells) Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.2 Hypothesis Testing (15 of 21) • Relationships between factors • Hypothesis: Stress makes people more susceptible to catching a cold. ‒ Is there a correlation between stress and the number of colds people have caught? Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.2 Hypothesis Testing (16 of 21) • Using correlation to test hypotheses ‒ Results: The number of colds increases as stress levels increase. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.2 Hypothesis Testing (17 of 21) • Using correlation to test hypotheses ‒ Results: The number of colds increases as stress levels increase. ‒ Caution! Correlation does not imply causation. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. Correlation vs causation Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.2 Hypothesis Testing (18 of 21) • Using correlation to test hypotheses ‒ The correlation might be due to other reasons Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.3 Understanding Statistics (1 of 8) • What statistical tests can tell us ‒ Statistics in science Specialized branch of mathematics Evaluate and compare data Sample - Small subgroup used in experimental tests Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.3 Understanding Statistics (2 of 8) • What statistical tests can tell us ‒ Statistical tests Examine differences between groups Results from sample may extend to entire population Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.3 Understanding Statistics (3 of 8) • What statistical tests can tell us ‒ Statistically significant Results show a true difference between groups Low probability that difference between groups is due to random chance Probability of 5% or less Researchers may infer that treatment had an effect Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.3 Understanding Statistics (8 of 8) • What statistical tests cannot tell us ‒ If an experiment was designed and carried out properly ‒ If observer error occurred ‒ can only evaluate the probability of sampling error Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.4 Evaluating Scientific Information (1 of 7) • Primary Sources Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.4 Evaluating Scientific Information (2 of 7) • Primary Sources ‒ Primary source: original research ‒ Peer review: critique by other scientists before publication to increase confidence in results Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.4 Evaluating Scientific Information (3 of 7) • Secondary Sources ‒ Secondary source: story about the original research ‒ Book ‒ News report ‒ Advertisement Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.4 Evaluating Scientific Information (4 of 7) • Anecdotal evidence ‒ Based on one person’s experience, not on experimental data. ‒ Example: a testimonial from a celebrity Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.4 Evaluating Scientific Information (5 of 7) • Science in the News Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.4 Evaluating Scientific Information (6 of 7) • Science in the News ‒ Consider the source. ‒ ‒ ‒ ‒ ‒ Reputable? Science background? Advertisements? Current? References? Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. What is the best way to prevent the common cold? (1 of 2) A. Take vitamin C. B. Wash your hands. C. Take zinc lozenges. D. Get a cold vaccine. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. What is the best way to prevent the common cold? (2 of 2) A. Take vitamin C. B. Wash your hands. C. Take zinc lozenges. D. Get a cold vaccine. Explanation: Washing hands is the only method that has been shown to prevent the common cold. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. 1.5 Is There a Cure for the Common Cold? • No cure or vaccine • Best prevention: Keep your hands clean! • No effect on cold susceptibility: ‒ Vitamin C ‒ Diet quality ‒ Exposure to cold temperatures ‒ Exercise • But may reduce cold symptoms: ‒ Vitamin C ‒ Echinacea tea ‒ Zinc lozenges Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. Variables Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. Chapter Review of Learning Outcomes (1 of 2) • Can you describe the characteristics of a scientific hypothesis? • Can you compare and contrast the terms scientific hypothesis and scientific theory? • Can you distinguish between inductive and deductive reasoning? • Can you explain why the truth of a hypothesis cannot be proven conclusively via deductive reasoning? • Can you describe the features of a controlled experiment, and explain how these experiments eliminate alternative hypotheses for the results? Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. Chapter Review of Learning Outcomes (2 of 2) • Can you list strategies for minimizing bias when designing experiments? • Can you define correlation, and explain the benefits and limitations of using this technique to test hypotheses? • Can you describe the information that statistical tests provide? • Can you compare and contrast primary and secondary sources? • Can you summarize the techniques you can use to evaluate scientific information from secondary sources? Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved. Copyright Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved.
