John, the WTS calls it "micro-evolution" to distinguish it from "macro-evolution". But of course they will not (and cannot!) explain where the boundary would be then between these two.
FYI: the origin of life is called abiogenesis. Like already said, indeed important to keep this separate from evolution.
Perhaps you can point your son to research the anatomy of whales. See: https://www.youtube.com/watch?v=lIEoO5KdPvg