I had to look for the excerpt attached to this question, and here is my answer:
The speaker in the excerpt given was Grendel and here, he was describing about himself at how he reacts and acts in times of arguments. Based on this excerpt above him, this shows that he is just PRACTICAL based on how he responds to the given situation.
The cell theory proposes that all living organisms are made up of cells, who in turn come from other cells, as well as that cells are responsible for the structure and organization of living things.
Its using a comma before a conjunctive adverb.
