When asked to describe what genetic variation is, would “differences in living things” be sufficient? Or is there something else that I need to add
I would go with:
Genetic variation is the difference in genetic code (DNA/Genes) that creates internal (hidden) or external (visible) differences between species, or between members of the same species. These genetic differences are expressed as different phenotypes.
If asked about a single species, I would adjust my answer to only refer to that species.