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

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

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

Types of Data Data are recorded observations or items of information Data are recorded observations or items of information Data fall into two categories Data fall into two categories Qualitative, or descriptions rather than measurements Qualitative, or descriptions rather than measurements Quantitative, or recorded measurements, which are sometimes organized into tables and graphs 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 Inductive reasoning draws conclusions through the logical process of induction Inductive reasoning draws conclusions through the logical process of induction Repeat specific observations can lead to important generalizations Repeat specific observations can lead to important generalizations For example, “the sun always rises in the east” 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 Deductive reasoning uses general premises to make specific predictions 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) 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

A Closer Look at Hypotheses in Scientific Inquiry A hypothesis must be testable and falsifiable A hypothesis must be testable and falsifiable Hypothesis-based science often makes use of two or more alternative hypotheses Hypothesis-based science often makes use of two or more alternative hypotheses Failure to falsify a hypothesis does not prove that hypothesis Failure to falsify a hypothesis does not prove that hypothesis 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) 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

The Myth of the Scientific Method The scientific method is an idealized process of inquiry 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 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 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 Stating the Problem Stating the Problem How do new living things, or organisms, come into being? How do new living things, or organisms, come into being? Forming a Hypothesis Forming a Hypothesis Francesco Redi questioned the theory of spontaneous generation Francesco Redi questioned the theory of spontaneous generation flies produce maggots flies produce maggots

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

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

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

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

Publishing and Repeating Investigations Spallanzani’s Test of Redi’s Findings Spallanzani’s Test of Redi’s Findings Lazzaro Spallanzani, Italian Lazzaro Spallanzani, Italian Broth had not been boiled long enough Broth had not been boiled long enough Boiled a container of broth in a water bath for 45 minutes Boiled a container of broth in a water bath for 45 minutes Image from:

Publishing and Repeating Investigations Pasteur’s Test of Spontaneous Generation Pasteur’s Test of Spontaneous Generation In 1864, French scientist, Louis Pasteur In 1864, French scientist, Louis Pasteur designed a flask with long curved neck designed a flask with long curved neck showed all living things come from other living things showed all living things come from other living things Image from:

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

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

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

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