How is Jem demonstrating that he is becoming an adult with textual evidence

Jem begins to mature during the beginning of Part Two and starts behaving like his morally-upright father. In chapter 14, Dill runs away from home and hides underneath Scout's bed. After discovering Dill under Scout's bed, Jem and Scout listen to Dill explain how and why he ran away. Jem understands that Dill's parents are probably worried about him and demonstrates maturity by saying,

"You oughta let your mother know where you are...You oughta let her know you’re here" (Lee, 142).

In chapter 15, Jem, Scout, and Dill watch as the Old Sarum bunch surrounds Atticus outside of Tom Robinson's cell in the Maycomb jailhouse. Jem recognizes that his father is in a dangerous situation and refuses to go home when Atticus tells him to. Jem once again demonstrates his maturity by recognizing the dangerous situation and refusing to leave his father alone. Scout describes her brother's obstinance by thinking,

We were accustomed to prompt, if not always cheerful acquiescence to Atticus’s instructions, but from the way he stood Jem was not thinking of budging (Lee, 154).

Following the Tom Robinson trial, Jem develops empathy for defenseless beings and illustrates his maturation by preventing Scout from squashing a harmless roly-poly bug in chapter 25. As Scout is about to smash the bug, Jem scowls at her. When Scout asks Jem why she isn't allowed to smash the bug, he reveals his maturation and understanding of his father's lesson regarding the importance of protecting innocent beings by saying,

"Because they don’t bother you" (Lee, 242).

In chapter 28, Scout gets yelled at from Mrs. Merriweather for coming onto the stage late and ruining the pageant. Fortunately, Jem demonstrates his maturity by attempting to comfort his sister. Scout contemplates,

She made me feel awful, but when Jem came to fetch me he was sympathetic. He said he couldn’t see my costume much from where he was sitting. How he could tell I was feeling bad under my costume I don’t know, but he said I did all right, I just came in a little late, that was all. Jem was becoming almost as good as Atticus at making you feel right when things went wrong (Lee, 262).