1. Scientific Methodology: The Heart of Science
I. Spontaneous Generation: the idea that life can arise from nonliving matter. Spontaneous
generation was accepted by many in the scientific community up until the mid-nineteenth
century. A series of simple experiments tested the validity of this idea.
II. Evidence used to support spontaneous generation was the observation that foods over
time become covered in maggots or fungal and bacterial growth. The inference behind
spontaneous generation is that there is no “parent” organism. Write this inference as a
hypothesis using an if–then sentence that suggests a way of testing it.
If spontaneous generation is valid, then covered food should also produce maggotts.
III. In 1668, Francesco Redi proposed a different hypothesis to explain the specific example
of maggots that appear on spoiled food. He had observed that maggots appear on meat a few
days after flies have been seen on the food. He inferred that the flies had left behind eggs
too small to see. Redi’s experiment is shown below. What conclusion can you draw from Redi’s experiment?

2. Study Questions:
The idea that life can arise from nonliving matter is called?
2. What was Francesco Redi’s hypothesis about the appearance of maggots?  
3. What are the independent, dependent & controlled variables in this experiment?   
4. Ideally, how many variables should an experiment test at a time?  
5. When a variable is kept unchanged in an experiment, it is said to be the  
6. What are the two groups in a controlled experiment?
7. What conclusion can you draw from Redi’s experiment?
Spontaneous Generation
If flies produce maggots, then flies could lay eggs in unprotected meat.
The manipulated variable was the presence or absence of the jar cover, and the
responding variable was whether maggots appear. The controlled variables (constants)
are using the same jar, meat & environment for the experiment.
One
controlled variable (constant).
Experimental & Control
Spontaneous generation is rejected. Redi reasoned that flies had laid eggs in the meat in the open jar. They are not able to enter the covered jar, therefore they could not lay eggs in the meat.