Different countries have different rules about how much a piece of artwork must be changed before it classed as a 'derivative work.'
That being said, if it's a character or some other uniquely-identifiable thing, especially if it's used for commercial purposes, it could fall under the copyright law of a character, or trademark law.
'Copyright' is the right to copy something. If you draw an original picture of your favourite anime character, the picture itself would be copyright to you, but the character in that picture would be copyright to its copyright holders. Whether that is a perfect copy or a hand-drawn copy, it's still a copy of that character.
So technically, drawing a picture of your favourite anime character, unless you own the copyright of that character, is a violation of the copyright of the character's creator.
As far as copying things like an apple from a photo, copyright laws in some countries state that the photographer holds the copyright of his/her photos, and copyright law is intended to protect the copyright of the photograph, not the rights of the subject of the photograph.
So if you copy a photograph in a way that's identifiable as a copy of the photograph, then you could be breaking copyright law. It depends on whether your 'copy' is different enough to be considered a derivative work. If you only copy part of the photograph, then your copy could come under 'fair use' law.
Many countries have signed a treaty that protects the copyrights of their citizens in all the countries who have signed that teaty. I believe it's the URAA:
But the intent of copyright is so that people can have control, for a finite period of time, over the works that they create so that they can copy those works for commercial purposes.
Copyright law is not the same in every country, but copyright law is a legal mechanism. So the answer to 'What is protected by copyright?' is not clear-cut.