Exploring Life: Scientific Methodology Chapter 1 Exploring Life: Scientific Methodology

Nature of Biological Inquiry: Science as a PROCESS Biological study is an ongoing process Information is continually being built upon and modified Science tries not to hold onto ideas just because they are familiar or comfortable Try to judge the evidence objectively. Tries to avoid personal bias. (examples…) Only when scientists are open to new ideas does scientific understanding increase

Concept 1.5: Biologists use various forms of inquiry to explore life At the heart of science is inquiry A search for information and explanation, often focusing on specific questions about the natural world in us and around us Biology blends two main processes of scientific inquiry Discovery science Hypothesis-based science

Discovery science (“observational” research) Describes natural structures and processes as accurately as possible through careful observation and analysis of data

Types of Data Data Are recorded observations Can be quantitative or qualitative Figure 1.24

Using the Scientific Method to solve a problem

The Myth of the Scientific Method Is an idealized process of inquiry Very few scientific inquiries strictly adhere to the “textbook” scientific method, but follow the same basic sequence The general idea 

Hypothesis-based science In science, inquiry that asks specific questions usually involves the proposing and testing of hypotheses In science, a hypothesis Is a tentative answer to a well-framed question, an explanation on trial Makes predictions that can be tested A scientific hypothesis must have two important qualities It must be testable It must be falsifiable

We all use hypotheses in solving everyday problems Observations Questions Hypothesis # 1: Dead batteries Hypothesis # 2: Burnt-out bulb Prediction: Replacing batteries will fix problem Replacing bulb Test prediction Test does not falsify hypothesis Test falsifies hypothesis Figure 1.25

Deduction: The “If…then” Logic of Hypothesis-Based Science In deductive reasoning The logic flows from the general to the specific; If A = B and B = C, then A = C Ex: Red meat has iron in it and beef is red meat, so beef has iron in it. If a hypothesis is correct, then we can expect a particular outcome prediction: is a forecast, based on your hypothesis. Experiment to see if your prediction came true. If not, your hypothesis must be rejected. If the predictions do come true, your hypothesis MAY be correct (accepted).

Designing controlled experiments Experiment must be designed to: Test the hypothesis Test the effect of one variable by comparing control groups and experimental groups in a way that cancels the effects of unwanted variables variables, constants/controls, # of trials, replicates, repeatability, reliability, accuracy, sampling

A controlled study: Variables: Experimental variable is the variable that is purposely changed or manipulated. All other variables need to remain constant, or “controlled”. Ensures that the phenomena observed result from factors we think they do. Groups: Test group (or “experimental”group) is a group of subjects that are exposed to the experimental variable. Control group is a group for comparison that is not exposed to the experimental variable; ex: a placebo may be used to simulate medication.

Science, Technology, and Society Technology applies scientific knowledge for some specific purpose “Bioinformatics":  analysis of biological information using computers and statistical techniques Modeling (ex: pharmacology/drug design, ecological models) Data collection and analysis (ex: DNA sequencing = Human Genome Project - mapping of 20-25,000 genes, over 3.3 billion base pairs)  http://en.wikipedia.org/wiki/Human_Genome_Project

What should you look for when you read about science? Be Critical when reading a scientific study What should you look for when you read about science? Beware of anecdotal data This is when people use their intuition or personal experiences as data. Understand methodology and results Does the data justify the conclusions inferred by the scientists? Be able to read a graph Have some understanding of statistics

Nature of Biological Inquiry Experiments generate data that’s ideally quantitative and objective Data is usually tabulated in tables or displayed in graphs . . . a Line graph. Line graphs are used to track changes over short and long periods of time, ex: rate of change. When smaller changes exist, line graphs are better to use than bar graphs. Line graphs can also be used to compare changes over the same period of time for more than one group. . . . a Bar Graph. Bar graphs are used to compare things between different groups or to track changes over time. However, when trying to measure change over time, bar graphs are best when the changes are larger. . . . a Pie Chart. Pie charts are best to use when you are trying to compare parts of a whole. They do not show changes over time.

Reading a Graph What information does this line graph convey? 1.4 Making sense of a scientific study Reading a Graph What information does this line graph convey? Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 130 standard error 120 Diameter of trees (cm) 1 10 100 Site 1 Site 2 Site 3 Site 4

Human population The Keeling Curve is a graph which plots the ongoing change in concentration of carbon dioxide in Earth's atmosphere since 1958. It is based on continuous measurements taken at the Mauna Loa Observatory in Hawaii that began under the supervision of Charles David Keeling. Ice core data from G. Marland, T.A. Boden, and R.J. Andres

Observe, Collect, and Record Data independent variable?  dependent variable?

Nature of Biological Inquiry Data analyzed using rigorous statistical analyses Mathematical test: How valid is experimental data? A significance level of 0.30 means that a conclusion has a 30% chance of being incorrect Scientists would find this an unacceptably large chance of error In general scientists will not say that they have a “significant” result unless the chances that their explanation is wrong are less than 5% (p < 0.05)

Nature of Biological Inquiry Collected and analyzed data will then be interpreted to draw a set of conclusions Conclusions may lead to development of new hypotheses and a new set of experiments Other scientists may repeat study Do their results gel with yours? If not, yet more experiments may be needed to find out why not!

Science is a social activity The Culture of Science Science is a social activity Characterized by both cooperation and competition Importance of PEER REVIEW Findings should be accurately written up and published where it can be subject to “peer review” Must include methods, data, conclusions; should be repeatable Others can learn from it, build on it. Other scientists judge quality of the work Figure 1.31

Reading about scientific information Scientific journals are considered the best primary source of information but can be difficult for the lay person to understand. Peer reviewed Ex: American Journal of Botany, Journal of Zoology, etc List of Biological journals http://en.wikipedia.org/wiki/List_of_scientific_journals_in_biology Often the lay person reads secondary sources and must be wary of information taken out of context. Be careful of information on the Internet by using reliable sources such as URLs with .edu, .gov and .org http://www.plosbiology.org/home.action Public Library of Science

How the Cause of Ulcers Was Discovered: The scientific method in action Observations: many patients had a particular bacterium near their ulcers Hypothesis: Helicobacter pylori is the cause of gastritis and ulcers.(1982 by Dr. Barry Marshall and Dr. Robin Warren ) Experiment/observations: 1st – H. pylori was isolated and grown from ulcer patients 2nd – humans swallowing a H. pylori solution resulted in inflammation in their stomachs Conclusion: H. pylori was the cause of most ulcers and can be cured by antibiotics See: http://en.wikipedia.org/wiki/Helicobacter_pylori#History

A controlled study in action Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1.3 Science is a process a. State Hypothesis: Antibiotic B is a better treatment for ulcers than antibiotic Large number of subjects were selected Subjects were divided into three groups b. Perform Experiment: Groups were treated the same except as noted Control group: received placebo Test group 1: received antibiotic A Test group 2: received antibiotic B c. Collect Data: Each subject was examined for the presence of ulcers d. 100 80 80 60 60 Conclusion: Hypothesis is supported: Antibiotic B is a better treatment for ulcers than antibiotic A Effectiveness of Treatment (%) 40 20 10 Control Group Test Group 1 Test Group 2 a: © blickwinkel/Alamy; d: © Phanie/Photo Researchers, Inc.

Theories in Science A scientific theory is a well-substantiated explanation of some aspect of the natural world that is acquired through the scientific method, and repeatedly confirmed through observation and experimentation. From the US National Academy of Sciences: “The formal scientific definition of theory is quite different from the everyday meaning of the word. It refers to a comprehensive explanation of some aspect of nature that is supported by a vast body of evidence. Many scientific theories are so well established that no new evidence is likely to alter them substantially. For example, no new evidence will demonstrate that the Earth does not orbit around the sun (heliocentric theory), or that living things are not made of cells (cell theory), that matter is not composed of atoms (atomic theory), or that the surface of the Earth is not divided into solid plates that have moved over geological timescales (the theory of plate tectonics) One of the most useful properties of scientific theories is that they can be used to make predictions about natural events or phenomena that have not yet been observed.[7]”