Dogs have a reduced nonfunctional digit on their paws known as a dewclaw what is this and example of

Answer;

Vestigial Structure

Explanation;Vestigial Structure are structures that have no apparent function and appear to be residual parts from a past ancestor. Vestigial structures are normally homologous to structures that are functioning normally in other species and therefore may be considered evidence for evolution. Other examples of vestigial structures include; the human appendix, the pelvic bone of a snake, and the wings of flightless birds.

The light is great source of energy