Here's the answer to the black panther question according to the Florida Panther Society:

Is there a “Black Panther”?

The term 'Black Panther' is quite often used in connection with large black cats - however there is no one distinct species of wildcat called a 'Black Panther'. Over the years it has become used as a common name that can be applied to any large black-coated cat. When you see a picture of a 'Black Panther' it is most likely that you are looking at either a Leopard or possibly a Jaguar with Melanistic coloration.

The term Melanistic is derived from melanin, a dark colored skin and hair pigment. In cats, melanism results in the fur of the animal being very dark or black in color. In many cases the usual markings of the animal can be faintly seen through the dark fur, especially at certain angles in bright sunlight. Melanistic cats are commonly born into mixed litters along with normally colored siblings.

(Note: There is no documented evidence of the existence of a melanistic Florida Panther.)