Long ago, many people believed that living things could come from nonliving things. They brought that worms came from wood that maggots came from decaying meat. This idea was spontaneous generation. In 1668, an Italian biologist, Francesco Redi, did experiments to prove that maggots did not come from meat but possibly from flies. One of his experiments is shown below. Redi placed pieces of meat in several jars. He divided the jars into two groups. He covered the first group of jars with fine cloth. He left the second group of jars uncovered. Redi observed the jars for several days. He saw flies on the cloth of the covered jars, and he saw flies laying eggs on the meat in the uncovered jars. Maggots appeared only on the meat in the group of jars left uncovered.
List the independent variable and dependent variable.