Both Uses

illustrate
in
Life of Pi
(Edited)

Each to him was a triumph of logic and mechanics, and nature as a whole was an exceptionally fine illustration of science.
Chpt 5-8 *

illustration = something that helps clarify or demonstrate
I suspect she suspected that I had a different take on the matter, but she never said anything when as a child I devoured the comic books of the Ramayana and the Mahabharata and an illustrated children's Bible and other stories of the gods.
Chpt 21-24 *

illustrated = accompanied by drawings

Definitions:

(1) (illustrate as in: as illustrated by this example)
to help make clear -- typically by example
(2) (illustrate as in: an illustrated children's book)
to draw pictures (or provide photographs) to accompany a book or other writing
(3) (meaning too rare to warrant focus)