1. How Scientists Work Key Concepts How do scientists test hypotheses?
How does a scientific theory develop?

2. Designing an Experiment
Ask a question
Forming a hypothesis
An educated answer to the question
Based on some prior knowledge or experience
Setting up a controlled experiment
Constants
Independent Variable (manipulated)
Dependent Variable (responding)

3. Designing an Experiment
Collecting Data (recording and analyzing results)
Drawing a conclusion

4. Redi’s ( )Experiment
Observation:
Flies land on meat that is left uncovered. Later maggots appear on the meat.

5. Do maggots spontaneously
Redi’s Experiment
Question:
Do maggots spontaneously
generate from meat?

6. Redi’s Experiment
Forming a hypothesis:
Flies produce maggots.

7. Redi’s Experiment
Experiment/Procedure:

8. Redi’s Experiment Constants: Jars Type of meat Location Temperature
Time

9. Redi’s Experiment Independent Variable (Manipulated)
* Gauze covering that keeps the flies away from the meat.
Dependent Variable
(Responding)
* Whether maggots appeared

10. Redi’s Experiment Conclusion: (R.A.C.E.)
Flies produce maggots when they come in contact with meat.(R) Spontaneous generation of maggots did not occur.(A) The jars that were covered had no maggots, where as the jars left uncovered had maggots.(C) Based on the results of this experiment spontaneous generation did not occur.(E)

11. When experiments are not possible
Field studies
Observe animals in the wild
Human Studies
Look at past data
Address different variables
Large groups

12. How a theory develops
The word theory applies to a well tested explanation that unifies a broad range of observations.
Multiple people, or multiple experiments have the same tested results
Evolution
Plate tectonics
Relativity

13. Key Concepts How do scientists test hypotheses?
How does a scientific theory develop?