No. Whenever you edit or enhance a photo, you're working on a copy. By default Save as a copy will be selected in the bottom right hand corner of the screen. When you click Done editing, you will see the original version of the image, as well as the copy.

However, if you click the Save as a copy drop down arrow, you can select to replace the original. In this case, your original image will be replaced with the edits that you have made.