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

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)

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

Redi’s (1626-1697)Experiment Observation: Flies land on meat that is left uncovered. Later maggots appear on the meat.

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

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

Redi’s Experiment Experiment/Procedure:

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

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

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)

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

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

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