1. Introduction to The Scientific Method A. Russo-Neustadt CSULA

2. What is the Scientific Method? A system of investigation that consists of three major steps: Step 1 = gathering facts or making an observation Step 2 = developing a hypothesis (explanation) to explain your observation Step 3 = testing your hypothesis

4. Step 1 for Primrose Example Observation = Plants on the northern side of your house are large and blooming profusely, while those on the southern side of the house are small, with few blooms

5. Step 2 for Primrose Example Note the following – Soil is dry on the southern side of the house, but moist on the northern side of the house, thus, Hypothesis = The primroses on the southern side of the house show poor growth because the soil there is too dry.

6. Step 3 Testing Your Hypothesis Requires Four Sub-steps Designing an experiment Making a prediction about the outcome of the experiment (based on the assumption that your hypothesis is correct) Conducting the experiment and collecting data (results) Drawing a conclusion = interpreting the results of the experiment

7. What is an Experiment? A scientific investigation carried out under controlled conditions. Controlled conditions refers to the attempt to regulate all variables that could influence the outcome of the experiment except the variable under investigation Examples of important variables for the primrose example?

8. Experimental Design for the Primrose Example Give the plants on the southern side of the house enough water to keep the soil as moist as it is on the northern side of the house

9. Prediction for the Primrose Example Predictions are “If, then” statements and look like - If “my hypothesis is correct”, then “the following should happen during my experiment”. If the plants on the southern side of the house show poor growth because the soil there is too dry, then…?

10. Conducting the Experiment for the Primrose Example Add additional water to the plants on the southern side of the house so that the soil moisture is approximately equal to that on the northern side of the house. Conduct experiment for (how long?) Result (data) = ?

11. Conclusion for the Primrose Example Differences in soil moisture are NOT responsible for the differences in plant growth observed between those primroses planted on the northern versus southern sides of the house.

12. What Do We Do Now? Modify our original hypothesis based on the outcome of our first experiment (return to step 2 and repeat process) Modified Hypothesis = The primroses on the southern side of the house show poor growth because they receive too much sunlight.

13. Step 3 for Modified Hypothesis Experimental Design – Use shade cloth to reduce the amount of sunlight received by the primroses on the southern side of the house to an amount equal to that received by plants on the northern side of the house.

14. Step 3 for Modified Hypothesis (continued) Prediction = If the primroses on the southern side of the house show poor growth because they receive too much sunlight, then...?

15. Step 3 for Modified Hypothesis (continued) Conducting the Experiment – Shade plants of the southern side of the house such that they receive +/- the same amount of sunlight as those on the northern side of the house Conduct experiment for (how long?) Results (data) = ?

16. Step 3 for Modified Hypothesis (continued) Conclusion = Differences in sunlight experienced by plants on the northern versus southern side of the house may have been an important factor in their growth differences.

17. A Note of Caution The scientific method never allows us to conclusively prove an hypothesis. Instead, the scientific method is designed to disprove an hypothesis. (For example, our original hypothesis in today’s example.) The original hypothesis is then modified and tested until a hypothesis is developed that cannot be proven incorrect.

18. What is a Scientific Theory? A hypothesis that has been tested in many different ways (i.e. with different experimental designs), many times and by many different scientists, but can not be proven incorrect So much evidence has been assembled in favor of an hypothesis that the scientific community is reasonably certain (but never absolutely sure) that the hypothesis is correct The scientific community is still open to modification of the theory, if appropriate evidence is produced

19. Another Example Francisco Redi was an Italian physician- scientist who demonstrated that spontaneous generation (production of life from non-living things) was not required to explain the appearance of maggots in spoiled meat.

20. ??????? Redi noticed that flies swarm around meat left exposed to the air and that maggots appear in the meat a few days later.

21. ?????? He thought that perhaps the maggots did not arise spontaneously from the non-living meat, as was commonly believed at the time, but that instead the maggots were produced by the flies.

22. ?????? In order to test this explanation, he cleaned two similar jars and put the same amount of fresh meat, without maggots, in each jar. He then covered one jar with gauze, so that no flies could enter, and left the other jar open to the flies.

23. ??????? He placed the jars on the same window ledge and was careful to keep the temperature, light exposure and humidity the same in both jars.

24. ?????? He thought to himself, “If the flies produce the maggots, then preventing their access to the meat should prevent production of maggots”.

25. ???????? After several days, Redi noticed that maggots appeared in the meat in the open jar, but not in the jar covered with gauze.

26. ??????? He decided that the results of this experiment suggested that the maggots are produced by the flies and not by spontaneous generation of life within the meat.

27. When Redi cleaned two similar jars, put the same amount of fresh meat in each jar and covered one jar with gauze and left the other jar open to the flies he was: A. Making an observation B. Designing an experiment C. Making a prediction D. Developing a hypothesis

28. When Redi cleaned two similar jars, put the same amount of fresh meat in each jar and covered one jar with gauze and left the other jar open to the flies he was: A. Making an observation B. Designing an experiment C. Making a prediction D. Developing a hypothesis

29. When Redi noticed that flies swarm around meat left exposed to the air and that maggots appear in the meat a few days later he was: A. Making a Prediction B. Developing a hypothesis C. Drawing a conclusion D. Making an observation

30. When Redi noticed that flies swarm around meat left exposed to the air and that maggots appear in the meat a few days later he was: A. Making a Prediction B. Developing a hypothesis C. Drawing a conclusion D. Making an observation

31. When Redi decided that the results of his experiment suggested that the maggots are produced by the flies and not by spontaneous generation of life within the meat he was: A. Drawing a conclusion B. Making an observation C. Controlling the variables D. Making a prediction

32. When Redi decided that the results of his experiment suggested that the maggots are produced by the flies and not by spontaneous generation of life within the meat he was: A. Drawing a conclusion B. Making an observation C. Controlling the variables D. Making a prediction

33. When Redi thought “perhaps maggots do not arise spontaneously from non-living meat, but instead are produced by the flies” he was: A. Making an observation B. Developing a hypothesis C. Drawing a conclusion D. Gathering facts

34. When Redi thought “perhaps maggots do not arise spontaneously from non-living meat, but instead are produced by the flies” he was: A. Making an observation B. Developing a hypothesis C. Drawing a conclusion D. Gathering facts

35. When Redi developed his If-Then statement he was: A. Making a hypothesis B. Making an observation C. Making a prediction D. Making cookies

36. When Redi developed his If-Then statement he was: A. Making a hypothesis B. Making an observation C. Making a prediction D. Making cookies

37. In the experiment described above, Redi was careful to make sure that both the experimental and the control jars were maintained at the same temperature and humidity, and received the same amount of light. He took these precautions because he wanted to conduct his experiment under controlled conditions. In Redi’s experiment temperature, humidity and amount of light represent the: a.Observations, b. Replicates, c. Variables, d. Results, e. Conclusions.

38. In the experiment described above, Redi was careful to make sure that both the experimental and the control jars were maintained at the same temperature and humidity, and received the same amount of light. He took these precautions because he wanted to conduct his experiment under controlled conditions. In Redi’s experiment temperature, humidity and amount of light represent the: a.Observations, b. Replicates, c. Variables, d. Results, e. Conclusions.