Jorgen
If you haven't read the book, I suggest reading it. The lord of the flies is a short book with very little vocabulary that tells a good society about how a pure land can become corrupted, which is the large problem with utopian societies.
For a better understanding of the scar(Just in case you didn't know), is explained literally and figuratively. The scar is a place on the island that was damaged when the boys hit the island that was pure and untouched. When they arrived it damaged a part of an island, knocking down trees. This is the place where they get together, almost like a gash, an opening in the island.
This is mentioned in the first paragraph of the entire story, so here's your chapter one quote:
"The boy with fair hair lowered himself down the last few feet of rock and
began to pick his way toward the lagoon. Though he had taken off his
school sweater and trailed it now from one hand, his grey shirt stuck to
him and his hair was plastered to his forehead. All round him the long
scar smashed into the jungle was a bath of heat. He was clambering
heavily among the creepers and broken trunks when a bird, a vision of
red and yellow, flashed upwards with a witch-like cry; and this cry was
echoed by another."
Figuratively, it represents the corruption of man, but that won't help you in this case.
Your quotes on chapter 3 and four are unrelated, but here they are anyway :)
Chapter 3:
He picked his way up the scar, passed the great rock where Ralph had
climbed on the first morning, then turned off to his right among the trees.
He walked with an accustomed tread through the acres of fruit trees,
where the least energetic could find an easy if unsatisfying meal.
Chapter 4:
A moment later he was battling
with the complex undergrowth that was already engulfing the scar