She knew Pa was the reason they all left; what she wondered was why no one took her with them.
-- Narration (chapter 2)

Importance: This line of narration helps to establish the sense of abandonment that Kya feels after her family members leave the shack permanently, leaving Kya and Pa to live their alone. Moreover, these lines develop Pa's abusive nature, which is depicted more directly in later parts of the novel.

Where ya been, marsh hen? Where’s yo’ hat, swamp rat?
-- Students (chapter 4)

Importance: These chants are among the insults that Kya receives from the other students during the one day that Kya attends school. The students apparently all feel the need to make fun of Kya because she lives in the swamp. This dynamic establishes the prejudice that the townspeople direct towards Kya for years.

He didn't want to shame her, so didn't show surprise.
-- Narration (chapter 16)

Importance: This line describes Tate's reaction after Kya, age 14, asks...