How does the development of cell theory serve as an example for the development of scientific theories in general?

The development of cell theory serves to show the rigorous activities that must be accomplished before a theory can be developed. A scientific theory is a tested and acceptable explanation for a particular observation. A scientific theory usually started as an observation. The observation is use to formulate an hypothesis which is then tested by carrying out an appropriate experiment. If the experiment confirms the hypothesis to be true, then other scientists from different parts of the world will carry out their own experiments in order to confirm the result of the experiment.
When the result of the experiment has been tested continuously for a long time and find to be true, then it becomes a theory. This is the chains of activities which the observations made in cells undergo before it becomes cell theory.

He used pea plants to study the patterns of heredity.