The Happy Robber A robber holds up a bank, but leaves with no money whatsoever. However, he is more pleased than if he had left with lots of money. Why????

Death by Romance A newly married couple had a fireside supper together. They were so cozy and comfortable that they dozed off on the floor. The next morning they were both found dead where they lay. What happened??

Scientific Method

and Spontaneous Generation

Objectives:

1) To identify the steps of the scientific method 2) To describe the parts of a controlled experiment

Scientific Method  A systematic way to solve a problem  Usually begins with a question about something observed  Important Note: There is NOT one “scientific method”

Scientific Method…  Hypothesis  Must be testable to be valid  If…then statement  Testing  Experiments  Models  Studies

Scientific Method, Experiments…  Control Group  Comparison  No experimental treatment  Experimental Group  Only

1

factor changed from control group  Factors that change in response  Constants

Scientific Method…  Tests yield data  Organized  Analyzed  Tests must be repeated  Conclusion  Answer to the problem

The Scientific Method in Action…

Disproving Spontaneous Generation

Where does life come from??

 Can something non-living come to life?

 If so , rotten meat could turn into flies

Is spontaneous generation true??

 1668, Francesco Redi was 1 st challenge theory to  Performed a controlled experiment using rotting meat  Hypothesized that maggots found on rotting meat came from flies not from meat itself 

If

maggots come from flies eggs,

then

only meat that has flies around it should have maggots

Redi’s Experiment:  3 jars with rotting meat  1 no cover  1 covered with cheesecloth  1 sealed

Evaluate Redi’s Experiment…  What was Redi’s control group?

 What was the Independent Variable?

 What were his constants?

Results:  Only the jar where the flies could reach the meat grew maggots  What should he conclude??

After Redi, there was still debate…  Did these conclusions apply to microorganisms?

 Over next 2 centuries, Needham, Spallanzani and Pasteur all performed experiments to answer this  Today, we accept the theory of biogenesis, living things come from other living things