Prior to cell theory and germ theory, in the 1600s-1800s, some scientists supported the theory of spontaneous generation. The theory proposed that living (cellular) organisms could form from inanimate objects, or from other unrelated organisms. For example, it was thought that cheese or grain could facilitate the formation of mice. Which tenets of cell theory refute, or contradict, the theory of spontaneous generation?

The concept of spontaneous generation was disproved by the idea that life comes from pre-existing life.

Explanation:

The supporters of spontaneous generation theory stated that life did not come from outer space but there is natural spontaneous generation of the living organisms from non-living matter on the earth.

For example, they believed that the decayed and rotting material like mud, straw etc. had the capacity to give rise to organisms like frog, flies, etc.

However, Louis Pasteur by his careful experimentation showed that life comes from pre-existing life.

He showed that in pre-sterilized flasks, life did not come in a closed flask with killed yeast within but in another flask having killed yeast and open to air, new life appeared. Which clearly indicated that pre-existing life forms are present in the air.

Pasteur kept one flask open to air and curved the neck of other one (swan neck experiment) so that the killed yeast present in the flask is not in direct contact with the air.

With his experiment he proved that life cannot come from the non-living object.