Chapter 1

1. Chapter 1 How Scientists Work: The Scientific Method

2. Designing an Experiment • Ask a Question • Form a hypothesis • Set up a controlled experiment • Record and analyze results • Draw a Conclusion • Repeat

3. 1-1 What is Science? • The goal of science is to investigate and understand the natural world, to explain events in the natural world, and to use those explanations to make useful predictions.

4. Ask a Question • Should you just accept an explanation for something? • 2,000 years ago, a Roman Poet wrote a Recipe for Bees • 1. Kill a bull • 2. Build a shed • 3. Place dead bull on branches inside shed • Wait for summer. Decaying body will produce bees

5. Form a Hypothesis • A hypothesis is a scientific explanation for a set of observations that can be tested in ways that support or reject it. • Hypotheses are not always correct! • Spontaneous Generation • Life can arise from non-living things

6. Aristotle • “Vital forces” bring living things into being from non-living things

7. Francesco Redi • Italian physician (born 1626) • Set up an experiment to disprove the theory that maggots came from decaying meat (spontaneous generation)

8. Figure1-8 Redi’s Experiment on SpontaneousGeneration Section 1-2 OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat. HYPOTHESIS: Flies produce maggots. PROCEDURE Uncovered jars Covered jars Controlled Variables: jars, type of meat, location, temperature, time Several days pass Manipulated Variables: gauze covering that keeps flies away from meat Responding Variable: whether maggots appear No maggots appear Maggots appear CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur.

9. Controlled Experiments • Variables must be controlled • Change only one thing at a time • Ex – one jar covered and one uncovered

10. Controlled Variables • Controls are the parts of the experiment that are the same • Ex: types of jars, type of meat, temperature

11. Manipulated Variables/ Independent • The part of the experiment that changes • Ex: covered and uncovered jars • Also known as independent variable

12. Responding Variables/Dependent • What happens as a result of the manipulated variable • The result of the experiment • Also know as dependent variables

13. Record and analyze results • Detailed and specific • Use notebooks, journals, computers • Redi kept a journal so others copying his work could see his results

14. Collecting and Analyzing Data • Scientists record experimental observations, gathering information called data. There are two main types of data: quantitative data and qualitative data.

15. Collecting and Analyzing Data • Quantitative data are numbers obtained by counting or measuring. • Qualitative data are descriptive and involve characteristics that cannot usually be counted.

16. Make a chart: • 5 qualitative observations about the classroom • 5 quantitative observations about the classroom

17. Draw Conclusions • Did your results support or refute your hypothesis? • Redi proposed that flies produce maggots not the rotting meat…was he right? • If data does not support your hypothesis, you must come up with a new hypothesis and re-test.

18. REPEAT!!! • Scientists must be able to repeat each other’s investigations AND get the same results to ensure they are valid

19. Scientists who tested Redi’s work • Anton von Leeuwenhook • Saw “animalicules” in pond water, rainwater and dust • Said spontaneous generation could occur

20. Scientists who tested Redi’s work • John Needham • Used “animalicules” and gravy to show spontaneous generation could occur (p. 11) • What was wrong with his experiment? Heated gravy, looked at it days later and saw “little animals”

21. Lazzaro Spallanzani • Improved Needham’s experiment • Believed Needham did not heat the gravy to kill everything

22. Figure 1-10 Spallanzani’s Experiment p. 11 Section 1-2 Flask is open. Gravy is boiled. Gravy is teeming with microorganisms. Flask is sealed. Gravy is free of microorganisms. Gravy is boiled.

23. Lazzaro Spallanzani • Organisms had to enter the flask from the air since sealed container was free of microorganisms • Supported Redi, Disproved Needham

24. Louis Pasteur • Some people said Spallanzani’s experiment wasn’t fair because it eliminated air from one of the flasks • Thought air was the “life force” needed to produce new life

25. Louis Pasteur • Designed a new flask and repeated Spallanzani’s experiment • PHSchool.com code: cbp-1012 http://phschool.com/webcodes10/index.cfm?wcprefix=cbp&wcsuffix=1012&fuseaction=home.gotoWebCode&x=0&y=0

26. Figure 1-11 Pasteur’s Experiment Section 1-2 Broth is boiled. Broth is free of microorganisms for a year. Curved neck is removed. Broth is teeming with microorganisms.

27. Figure 1-11 Pasteur’s Experiment Section 1-2 Broth is boiled. Broth is free of microorganisms for a year. Curved neck is removed. Broth is teeming with microorganisms.

28. Figure 1-11 Pasteur’s Experiment Section 1-2 Broth is boiled. Broth is free of microorganisms for a year. Curved neck is removed. Broth is teeming with microorganisms.

29. Figure 1-11 Pasteur’s Experiment Section 1-2 Broth is boiled. Broth is free of microorganisms for a year. Curved neck is removed. Broth is teeming with microorganisms.

30. Pasteur • Convinced scientists spontaneous generation was false • Explained the souring of wine • Discovered small organisms were responsible for disease.

31. When experiments are not possible • Animal studies – observe only • Exposure to certain chemicals causing cancer • Can’t give people a chemical you suspect causes cancer

32. How a theory develops • A well tested explanation that unifies a broad range of observations • Can you name some • http://www.biologycorner.com/worksheets/scientific_method_plant_exp.html#.UjsFM2fpWSo