How Scientists Work How do scientists test hypotheses

How Scientists Work How do scientists test hypotheses? How does a scientific theory develop?

Objectives SPI 3210 Inq. 1 Select a description or scenario that reevaluates and/or extends a scientific finding. n SPI 3210 Inq. 2 Analyze the components of a properly designed scientific investigation. n SPI 3210 Inq. 5 Defend a conclusion based on scientific evidence. n

Chimpanzees and Humans n You and your partner, determine your roles

Inquiry n n n Inquiry is the search for information and explanation Scientists begin an inquiry investigation with a question There are two main types of scientific inquiry: discovery science and hypothesisbased science Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Discovery Science n n Discovery science describes natural structures and processes This approach is based on observation and the analysis of data Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Types of Data n n Data are recorded observations or items of information Data fall into two categories n n Qualitative, or descriptions rather than measurements Quantitative, or recorded measurements, which are sometimes organized into tables and graphs Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

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Induction in Discovery Science n n Inductive reasoning draws conclusions through the logical process of induction Repeat specific observations can lead to important generalizations n For example, “the sun always rises in the east” Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Deduction: The “If…Then” Logic of Hypothesis Based Science n n Deductive reasoning uses general premises to make specific predictions For example, if organisms are made of cells (premise 1), and humans are organisms (premise 2), then humans are composed of cells (deductive prediction) Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Partner time Humans: describe the difference between inductive and deductive reasoning to your partner n Chimpanzees: Review the difference between quantitative and qualitative data n

Objectives SPI 3210 Inq. 1 Select a description or scenario that reevaluates and/or extends a scientific finding. n SPI 3210 Inq. 2 Analyze the components of a properly designed scientific investigation. n SPI 3210 Inq. 5 Defend a conclusion based on scientific evidence. n

A Closer Look at Hypotheses in Scientific Inquiry n n n A hypothesis must be testable and falsifiable Hypothesis-based science often makes use of two or more alternative hypotheses Failure to falsify a hypothesis does not prove that hypothesis n For example, you replace your flashlight bulb, and it now works; this supports the hypothesis that your bulb was burnt out, but does not prove it (perhaps the first bulb was inserted incorrectly) Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

n n n The Myth of the Scientific Method The scientific method is an idealized process of inquiry Hypothesis-based science is based on the “textbook” scientific method but rarely follows all the ordered steps Discovery science has made important contributions with very little dependence on the so-called scientific method Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Scientific Method n Stating the Problem n. How do new living things, or organisms, come into being? n Forming a Hypothesis n. Francesco Redi questioned theory of spontaneous generation

Scientific Method n Setting Up a Controlled Experiment n Recording and Analyzing Results n Drawing a Conclusion n Publishing and Repeating Investigations

Objectives SPI 3210 Inq. 1 Select a description or scenario that reevaluates and/or extends a scientific finding. n SPI 3210 Inq. 2 Analyze the components of a properly designed scientific investigation. n SPI 3210 Inq. 5 Defend a conclusion based on scientific evidence. n

Partner time Humans: Tell your partner the two things that make a valid hypothesis n Chimpanzees: Walk through the steps of the scientific method n Chimps and humans together: discuss how we sometimes oversimplify the scientific method n

Objectives SPI 3210 Inq. 1 Select a description or scenario that reevaluates and/or extends a scientific finding. n SPI 3210 Inq. 2 Analyze the components of a properly designed scientific investigation. n SPI 3210 Inq. 5 Defend a conclusion based on scientific evidence. n

Setting Up a Controlled Experiment n Variables - factors in an experiment that can change n equipment used, type of material, amount of material, temperature, light, and time n Only one variable tested at a time n All other variables are kept unchanged, or controlled. ncontrolled experiment.

Types of variables n Independent variable n Manipulated variable n What you change n Dependent variable n Responding variable n Changes in response to manipulated variable n What you measure

Example experiment n Determining the source of life

Publishing and Repeating Investigations n Needham’s Test of Redi’s Findings n mid-1700 s, John Needham, an English scientist n attacked Redi’s work n claimed spontaneous generation could occur under right conditions n heated gravy

Publishing and Repeating Investigations n Spallanzani’s Test of Redi’s Findings n Lazzaro Spallanzani, Italian n Broth had not been boiled long enough n Boiled a container of broth in a water bath for 45 minutes Image from: http: //www. chemheritage. org/Educational. Services/pharm/antibiot/readings/sp

Publishing and Repeating Investigations n Pasteur’s Test of Spontaneous Generation n In 1864, French scientist, Louis Pasteur n designed a flask with long curved neck n showed all living things come from other living Image from: http: //www. chemheritage. org/Educational. Services/pharm/antibiot/readings/sp

Verifiable What does this word mean? n How does it relate to science? ? n

How a Theory Develops n Hypothesis may become so well supported scientists consider it a theory. n Theories enable scientists to make accurate predictions about new situations n As new evidence is uncovered, a theory may be revised or replaced by a more useful explanation

Inferences n Scientists often draw inferences from data gathered during experiments. n Inference- conclusion made on the basis of facts and previous knowledge rather than on direct observations. n Unlike a hypothesis, an inference is not directly testable.

Objectives SPI 3210 Inq. 1 Select a description or scenario that reevaluates and/or extends a scientific finding. n SPI 3210 Inq. 2 Analyze the components of a properly designed scientific investigation. n SPI 3210 Inq. 5 Defend a conclusion based on scientific evidence. n

Precision and Accuracy n Precision Describes the unit you used to measure n The smaller the unit of measurement, the more precise the measurement n n Accuracy How close the measurement is to the actual value n How different your number is from the accepted value n

Qualitative vs. quantitative n Qualitative n n Descriptive data Quantitative n Measurement data