There are two big differences between a drawing and a sketch. A drawings purposes are different, they can be done just as a beautiful work to look at, or be informative. A sketch is done by a few fast strokes with the artist expressing what he/she had in mind while sketching it. In modern time sketches has been accepted as artwork, while before a sketch was something an artist kept for himself.
One reason for sketches being so popular today is because sketches are so rich in expressions, while realistic drawings has got competition from the camera pictures that we have in this modern time.
So in conclusion: animal drawings purpose is either being informative or just a beautiful artwork to look at. Animal sketches purpose is showing the artist expressions by some fast strokes with the pencil.
Animal sketches, animal drawings what's the difference?